chore: Add Prabhpreet to the list of whitepper authors

add shared dependencies to workspace dependencies

all package level dependencies now rely on workspace

.github/workflows/qc.yaml

@@ -117,3 +117,32 @@ jobs:
           name: rosenpass
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
       - run: nix develop --command cargo test
+
+  cargo-fuzz:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cargo/bin/
+            ~/.cargo/registry/index/
+            ~/.cargo/registry/cache/
+            ~/.cargo/git/db/
+            target/
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+      - name: Install libsodium
+        run: sudo apt-get install -y libsodium-dev
+      - name: Install nightly toolchain
+        run: |
+          rustup toolchain install nightly
+          rustup default nightly
+      - name: Install cargo-fuzz
+        run: cargo install cargo-fuzz
+      - name: Run fuzzing
+        run: |
+          cargo fuzz run fuzz_aead_enc_into -- -max_total_time=60
+          cargo fuzz run fuzz_blake2b -- -max_total_time=60
+          cargo fuzz run fuzz_handle_msg -- -max_total_time=60
+          cargo fuzz run fuzz_kyber_encaps -- -max_total_time=60
+          cargo fuzz run fuzz_mceliece_encaps -- -max_total_time=60

Cargo.lock

@@ -107,6 +107,15 @@ dependencies = [
  "backtrace",
 ]
 
+[[package]]
+name = "arbitrary"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d5a26814d8dcb93b0e5a0ff3c6d80a8843bafb21b39e8e18a6f05471870e110"
+dependencies = [
+ "derive_arbitrary",
+]
+
 [[package]]
 name = "atty"
 version = "0.2.14"
@@ -213,6 +222,7 @@ version = "1.0.83"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f1174fb0b6ec23863f8b971027804a42614e347eafb0a95bf0b12cdae21fc4d0"
 dependencies = [
+ "jobserver",
  "libc",
 ]
 
@@ -438,6 +448,23 @@ version = "0.3.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7762d17f1241643615821a8455a0b2c3e803784b058693d990b11f2dce25a0ca"
 
+[[package]]
+name = "derive_arbitrary"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "67e77553c4162a157adbf834ebae5b415acbecbeafc7a74b0e886657506a7611"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "doc-comment"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fea41bba32d969b513997752735605054bc0dfa92b4c56bf1189f2e174be7a10"
+
 [[package]]
 name = "either"
 version = "1.9.0"
@@ -646,6 +673,15 @@ version = "1.0.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "af150ab688ff2122fcef229be89cb50dd66af9e01a4ff320cc137eecc9bacc38"
 
+[[package]]
+name = "jobserver"
+version = "0.1.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8c37f63953c4c63420ed5fd3d6d398c719489b9f872b9fa683262f8edd363c7d"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "js-sys"
 version = "0.3.65"
@@ -697,6 +733,17 @@ dependencies = [
  "rle-decode-fast",
 ]
 
+[[package]]
+name = "libfuzzer-sys"
+version = "0.4.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a96cfd5557eb82f2b83fed4955246c988d331975a002961b07c81584d107e7f7"
+dependencies = [
+ "arbitrary",
+ "cc",
+ "once_cell",
+]
+
 [[package]]
 name = "libloading"
 version = "0.7.4"
@@ -1011,10 +1058,9 @@ checksum = "3582f63211428f83597b51b2ddb88e2a91a9d52d12831f9d08f5e624e8977422"
 
 [[package]]
 name = "rosenpass"
-version = "0.2.1-rc.3"
+version = "0.2.1"
 dependencies = [
  "anyhow",
- "base64",
  "clap 4.4.8",
  "criterion",
  "env_logger",
@@ -1025,6 +1071,11 @@ dependencies = [
  "mio",
  "oqs-sys",
  "paste",
+ "rosenpass-ciphers",
+ "rosenpass-constant-time",
+ "rosenpass-sodium",
+ "rosenpass-to",
+ "rosenpass-util",
  "serde",
  "stacker",
  "static_assertions",
@@ -1033,6 +1084,64 @@ dependencies = [
  "toml",
 ]
 
+[[package]]
+name = "rosenpass-ciphers"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "rosenpass-constant-time",
+ "rosenpass-sodium",
+ "rosenpass-to",
+ "static_assertions",
+ "zeroize",
+]
+
+[[package]]
+name = "rosenpass-constant-time"
+version = "0.1.0"
+dependencies = [
+ "rosenpass-to",
+]
+
+[[package]]
+name = "rosenpass-fuzzing"
+version = "0.0.1"
+dependencies = [
+ "arbitrary",
+ "libfuzzer-sys",
+ "rosenpass",
+ "rosenpass-ciphers",
+ "rosenpass-sodium",
+ "rosenpass-to",
+ "stacker",
+]
+
+[[package]]
+name = "rosenpass-sodium"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "libsodium-sys-stable",
+ "log",
+ "rosenpass-to",
+ "rosenpass-util",
+]
+
+[[package]]
+name = "rosenpass-to"
+version = "0.1.0"
+dependencies = [
+ "doc-comment",
+]
+
+[[package]]
+name = "rosenpass-util"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "base64",
+]
+
 [[package]]
 name = "rustc-demangle"
 version = "0.1.23"
@@ -1614,6 +1723,12 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "zeroize"
+version = "1.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "525b4ec142c6b68a2d10f01f7bbf6755599ca3f81ea53b8431b7dd348f5fdb2d"
+
 [[package]]
 name = "zip"
 version = "0.6.6"

Cargo.toml

@@ -3,8 +3,48 @@ resolver = "2"
 
 members = [
     "rosenpass",
+    "ciphers",
+    "util",
+    "constant-time",
+    "sodium",
+    "to",
+    "fuzz",
+]
+
+default-members = [
+    "rosenpass"
 ]
 
 [workspace.metadata.release]
 # ensure that adding `--package` as argument to `cargo release` still creates version tags in the form of `vx.y.z`
 tag-prefix = ""
+
+[workspace.dependencies]
+rosenpass = { path = "rosenpass" }
+rosenpass-util = { path = "util" }
+rosenpass-constant-time = { path = "constant-time" }
+rosenpass-sodium = { path = "sodium" }
+rosenpass-ciphers = { path = "ciphers" }
+rosenpass-to = { path = "to" }
+criterion = "0.4.0"
+test_bin = "0.4.0"
+libfuzzer-sys = "0.4"
+stacker = "0.1.15"
+doc-comment = "0.3.3"
+base64 = "0.21.1"
+zeroize = "1.7.0"
+memoffset = "0.9.0"
+lazy_static = "1.4.0"
+thiserror = "1.0.40"
+paste = "1.0.12"
+env_logger = "0.10.0"
+toml = "0.7.4"
+static_assertions = "1.1.0"
+log = { version = "0.4.17" }
+clap = { version = "4.3.0", features = ["derive"] }
+serde = { version = "1.0.163", features = ["derive"] }
+arbitrary = { version = "1.3.2", features = ["derive"] }
+anyhow = { version = "1.0.71", features = ["backtrace"] }
+mio = { version = "0.8.6", features = ["net", "os-poll"] }
+libsodium-sys-stable= { version = "1.19.28", features = ["use-pkg-config"] }
+oqs-sys = { version = "0.8", default-features = false, features = ['classic_mceliece', 'kyber']  }

ciphers/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "rosenpass-ciphers"
+authors = ["Karolin Varner <karo@cupdev.net>", "wucke13 <wucke13@gmail.com>"]
+version = "0.1.0"
+edition = "2021"
+license = "MIT OR Apache-2.0"
+description = "Rosenpass internal ciphers and other cryptographic primitives used by rosenpass."
+homepage = "https://rosenpass.eu/"
+repository = "https://github.com/rosenpass/rosenpass"
+readme = "readme.md"
+
+[dependencies]
+anyhow = { workspace = true }
+rosenpass-sodium = { workspace = true }
+rosenpass-to = { workspace = true }
+rosenpass-constant-time = { workspace = true }
+static_assertions = { workspace = true }
+zeroize = { workspace = true }

ciphers/readme.md

@@ -0,0 +1,5 @@
+# Rosenpass internal cryptographic primitives
+
+Ciphers and other cryptographic primitives used by rosenpass.
+
+This is an internal library; not guarantee is made about its API at this point in time.

ciphers/src/lib.rs

@@ -0,0 +1,28 @@
+use static_assertions::const_assert;
+
+pub mod subtle;
+
+pub const KEY_LEN: usize = 32;
+const_assert!(KEY_LEN == aead::KEY_LEN);
+const_assert!(KEY_LEN == xaead::KEY_LEN);
+const_assert!(KEY_LEN == hash::KEY_LEN);
+
+/// Authenticated encryption with associated data
+pub mod aead {
+    pub use rosenpass_sodium::aead::chacha20poly1305_ietf::{
+        decrypt, encrypt, KEY_LEN, NONCE_LEN, TAG_LEN,
+    };
+}
+
+/// Authenticated encryption with associated data with a constant nonce
+pub mod xaead {
+    pub use rosenpass_sodium::aead::xchacha20poly1305_ietf::{
+        decrypt, encrypt, KEY_LEN, NONCE_LEN, TAG_LEN,
+    };
+}
+
+pub mod hash {
+    pub use crate::subtle::incorrect_hmac_blake2b::{
+        hash, KEY_LEN, KEY_MAX, KEY_MIN, OUT_MAX, OUT_MIN,
+    };
+}

ciphers/src/subtle/incorrect_hmac_blake2b.rs

@@ -0,0 +1,44 @@
+use anyhow::ensure;
+use rosenpass_constant_time::xor;
+use rosenpass_sodium::hash::blake2b;
+use rosenpass_to::{ops::copy_slice, with_destination, To};
+use zeroize::Zeroizing;
+
+pub const KEY_LEN: usize = 32;
+pub const KEY_MIN: usize = KEY_LEN;
+pub const KEY_MAX: usize = KEY_LEN;
+pub const OUT_MIN: usize = blake2b::OUT_MIN;
+pub const OUT_MAX: usize = blake2b::OUT_MAX;
+
+/// This is a woefully incorrect implementation of hmac_blake2b.
+/// See <https://github.com/rosenpass/rosenpass/issues/68#issuecomment-1563612222>
+///
+/// It accepts 32 byte keys, exclusively.
+///
+/// This will be replaced, likely by Kekkac at some point soon.
+/// <https://github.com/rosenpass/rosenpass/pull/145>
+#[inline]
+pub fn hash<'a>(key: &'a [u8], data: &'a [u8]) -> impl To<[u8], anyhow::Result<()>> + 'a {
+    const IPAD: [u8; KEY_LEN] = [0x36u8; KEY_LEN];
+    const OPAD: [u8; KEY_LEN] = [0x5Cu8; KEY_LEN];
+
+    with_destination(|out: &mut [u8]| {
+        // Not bothering with padding; the implementation
+        // uses appropriately sized keys.
+        ensure!(key.len() == KEY_LEN);
+
+        type Key = Zeroizing<[u8; KEY_LEN]>;
+        let mut tmp_key = Key::default();
+
+        copy_slice(key).to(tmp_key.as_mut());
+        xor(&IPAD).to(tmp_key.as_mut());
+        let mut outer_data = Key::default();
+        blake2b::hash(tmp_key.as_ref(), data).to(outer_data.as_mut())?;
+
+        copy_slice(key).to(tmp_key.as_mut());
+        xor(&OPAD).to(tmp_key.as_mut());
+        blake2b::hash(tmp_key.as_ref(), outer_data.as_ref()).to(out)?;
+
+        Ok(())
+    })
+}

ciphers/src/subtle/mod.rs

@@ -0,0 +1 @@
+pub mod incorrect_hmac_blake2b;

constant-time/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "rosenpass-constant-time"
+version = "0.1.0"
+authors = ["Karolin Varner <karo@cupdev.net>", "wucke13 <wucke13@gmail.com>"]
+edition = "2021"
+license = "MIT OR Apache-2.0"
+description = "Rosenpass internal utilities for constant time crypto implementations"
+homepage = "https://rosenpass.eu/"
+repository = "https://github.com/rosenpass/rosenpass"
+readme = "readme.md"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rosenpass-to = { workspace = true }

constant-time/readme.md

@@ -0,0 +1,5 @@
+# Rosenpass constant time library
+
+Rosenpass internal library providing basic constant-time operations.
+
+This is an internal library; not guarantee is made about its API at this point in time.

constant-time/src/lib.rs

@@ -0,0 +1,26 @@
+use rosenpass_to::{with_destination, To};
+
+/// Xors the source into the destination
+///
+/// # Examples
+///
+/// ```
+/// use rosenpass_constant_time::xor;
+/// use rosenpass_to::To;
+/// assert_eq!(
+///     xor(b"world").to_this(|| b"hello".to_vec()),
+///     b"\x1f\n\x1e\x00\x0b");
+/// ```
+///
+/// # Panics
+///
+/// If source and destination are of different sizes.
+#[inline]
+pub fn xor<'a>(src: &'a [u8]) -> impl To<[u8], ()> + 'a {
+    with_destination(|dst: &mut [u8]| {
+        assert!(src.len() == dst.len());
+        for (dv, sv) in dst.iter_mut().zip(src.iter()) {
+            *dv ^= *sv;
+        }
+    })
+}

doc/rosenpass.1

@@ -91,9 +91,18 @@ This makes it possible to add peers entirely from
 .Sh SEE ALSO
 .Xr rp 1 ,
 .Xr wg 1
+.Rs
+.%A Karolin Varner
+.%A Benjamin Lipp
+.%A Wanja Zaeske
+.%A Lisa Schmidt
+.%D 2023
+.%T Rosenpass
+.%U https://rosenpass.eu/whitepaper.pdf
+.Re
 .Sh STANDARDS
-This tool is the reference implementation of the Rosenpass protocol, written
-by Karolin Varner, Benjamin Lipp, Wanja Zaeske, and Lisa Schmidt.
+This tool is the reference implementation of the Rosenpass protocol, as
+specified within the whitepaper referenced above.
 .Sh AUTHORS
 Rosenpass was created by Karolin Varner, Benjamin Lipp, Wanja Zaeske,
 Marei Peischl, Stephan Ajuvo, and Lisa Schmidt.

flake.nix

@@ -29,6 +29,7 @@
       ]
         (system:
           let
+            scoped = (scope: scope.result);
             lib = nixpkgs.lib;
 
             # normal nixpkgs
@@ -58,11 +59,35 @@
             cargoToml = builtins.fromTOML (builtins.readFile ./rosenpass/Cargo.toml);
 
             # source files relevant for rust
-            src = pkgs.lib.sources.sourceFilesBySuffices ./. [
-              ".lock"
-              ".rs"
-              ".toml"
-            ];
+            src = scoped rec {
+              # File suffices to include
+              extensions = [
+                "lock"
+                "rs"
+                "toml"
+              ];
+              # Files to explicitly include
+              files = [
+                "to/README.md"
+              ];
+
+              src = ./.;
+              filter = (path: type: scoped rec {
+                inherit (lib) any id removePrefix hasSuffix;
+                anyof = (any id);
+
+                basename = baseNameOf (toString path);
+                relative = removePrefix (toString src + "/") (toString path);
+
+                result = anyof [
+                  (type == "directory")
+                  (any (ext: hasSuffix ".${ext}" basename) extensions)
+                  (any (file: file == relative) files)
+                ];
+              });
+
+              result = pkgs.lib.sources.cleanSourceWith { inherit src filter; };
+            };
 
             # builds a bin path for all dependencies for the `rp` shellscript
             rpBinPath = p: with p; lib.makeBinPath [
@@ -325,7 +350,7 @@
           checks = {
             cargo-fmt = pkgs.runCommand "check-cargo-fmt"
               { inherit (self.devShells.${system}.default) nativeBuildInputs buildInputs; } ''
-              cargo fmt --manifest-path=${./.}/Cargo.toml --check && touch $out
+              cargo fmt --manifest-path=${./.}/Cargo.toml --check --all && touch $out
             '';
             nixpkgs-fmt = pkgs.runCommand "check-nixpkgs-fmt"
               { nativeBuildInputs = [ pkgs.nixpkgs-fmt ]; } ''

fuzz/.gitignore

@@ -0,0 +1,4 @@
+target
+corpus
+artifacts
+coverage

fuzz/Cargo.toml

@@ -0,0 +1,47 @@
+[package]
+name = "rosenpass-fuzzing"
+version = "0.0.1"
+publish = false
+edition = "2021"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+arbitrary = { workspace = true }
+libfuzzer-sys = { workspace = true }
+stacker = { workspace = true }
+rosenpass-sodium = { workspace = true }
+rosenpass-ciphers = { workspace = true }
+rosenpass-to = { workspace = true }
+rosenpass = { workspace = true }
+
+[[bin]]
+name = "fuzz_handle_msg"
+path = "fuzz_targets/handle_msg.rs"
+test = false
+doc = false
+
+[[bin]]
+name = "fuzz_blake2b"
+path = "fuzz_targets/blake2b.rs"
+test = false
+doc = false
+
+[[bin]]
+name = "fuzz_aead_enc_into"
+path = "fuzz_targets/aead_enc_into.rs"
+test = false
+doc = false
+
+[[bin]]
+name = "fuzz_mceliece_encaps"
+path = "fuzz_targets/mceliece_encaps.rs"
+test = false
+doc = false
+
+[[bin]]
+name = "fuzz_kyber_encaps"
+path = "fuzz_targets/kyber_encaps.rs"
+test = false
+doc = false

fuzz/fuzz_targets/aead_enc_into.rs

@@ -0,0 +1,32 @@
+#![no_main]
+extern crate arbitrary;
+extern crate rosenpass;
+
+use libfuzzer_sys::fuzz_target;
+
+use rosenpass_ciphers::aead;
+use rosenpass_sodium::init as sodium_init;
+
+#[derive(arbitrary::Arbitrary, Debug)]
+pub struct Input {
+    pub key: [u8; 32],
+    pub nonce: [u8; 12],
+    pub ad: Box<[u8]>,
+    pub plaintext: Box<[u8]>,
+}
+
+fuzz_target!(|input: Input| {
+    sodium_init().unwrap();
+
+    let mut ciphertext: Vec<u8> = Vec::with_capacity(input.plaintext.len() + 16);
+    ciphertext.resize(input.plaintext.len() + 16, 0);
+
+    aead::encrypt(
+        ciphertext.as_mut_slice(),
+        &input.key,
+        &input.nonce,
+        &input.ad,
+        &input.plaintext,
+    )
+    .unwrap();
+});

fuzz/fuzz_targets/blake2b.rs

@@ -0,0 +1,22 @@
+#![no_main]
+extern crate arbitrary;
+extern crate rosenpass;
+
+use libfuzzer_sys::fuzz_target;
+
+use rosenpass_sodium::{hash::blake2b, init as sodium_init};
+use rosenpass_to::To;
+
+#[derive(arbitrary::Arbitrary, Debug)]
+pub struct Blake2b {
+    pub key: [u8; 32],
+    pub data: Box<[u8]>,
+}
+
+fuzz_target!(|input: Blake2b| {
+    sodium_init().unwrap();
+
+    let mut out = [0u8; 32];
+
+    blake2b::hash(&input.key, &input.data).to(&mut out).unwrap();
+});

fuzz/fuzz_targets/handle_msg.rs

@@ -0,0 +1,21 @@
+#![no_main]
+extern crate rosenpass;
+
+use libfuzzer_sys::fuzz_target;
+
+use rosenpass::coloring::Secret;
+use rosenpass::protocol::CryptoServer;
+use rosenpass_sodium::init as sodium_init;
+
+fuzz_target!(|rx_buf: &[u8]| {
+    sodium_init().unwrap();
+
+    let sk = Secret::from_slice(&[0; 13568]);
+    let pk = Secret::from_slice(&[0; 524160]);
+
+    let mut cs = CryptoServer::new(sk, pk);
+    let mut tx_buf = [0; 10240];
+
+    // We expect errors while fuzzing therefore we do not check the result.
+    let _ = cs.handle_msg(rx_buf, &mut tx_buf);
+});

fuzz/fuzz_targets/kyber_encaps.rs

@@ -0,0 +1,19 @@
+#![no_main]
+extern crate arbitrary;
+extern crate rosenpass;
+
+use libfuzzer_sys::fuzz_target;
+
+use rosenpass::pqkem::{EphemeralKEM, KEM};
+
+#[derive(arbitrary::Arbitrary, Debug)]
+pub struct Input {
+    pub pk: [u8; 800],
+}
+
+fuzz_target!(|input: Input| {
+    let mut ciphertext = [0u8; 768];
+    let mut shared_secret = [0u8; 32];
+
+    EphemeralKEM::encaps(&mut shared_secret, &mut ciphertext, &input.pk).unwrap();
+});

fuzz/fuzz_targets/mceliece_encaps.rs

@@ -0,0 +1,14 @@
+#![no_main]
+extern crate rosenpass;
+
+use libfuzzer_sys::fuzz_target;
+
+use rosenpass::pqkem::{StaticKEM, KEM};
+
+fuzz_target!(|input: &[u8]| {
+    let mut ciphertext = [0u8; 188];
+    let mut shared_secret = [0u8; 32];
+
+    // We expect errors while fuzzing therefore we do not check the result.
+    let _ = StaticKEM::encaps(&mut shared_secret, &mut ciphertext, input);
+});

papers/whitepaper.md

@@ -6,6 +6,7 @@ author:
 - Benjamin Lipp = Max Planck Institute for Security and Privacy (MPI-SP)
 - Wanja Zaeske
 - Lisa Schmidt = {Scientific Illustrator – \\url{mullana.de}}
+- Prabhpreet Dua
 abstract: |
        Rosenpass is used to create post-quantum-secure VPNs. Rosenpass computes a shared key, WireGuard (WG) [@wg] uses the shared key to establish a secure connection. Rosenpass can also be used without WireGuard, deriving post-quantum-secure symmetric keys for another application. The Rosenpass protocol builds on “Post-quantum WireGuard” (PQWG) [@pqwg] and improves it by using a cookie mechanism to provide security against state disruption attacks.
 
@@ -428,12 +429,89 @@ The responder code handling InitConf needs to deal with the biscuits and package
 
 ICR5 and ICR6 perform biscuit replay protection using the biscuit number. This is not handled in `load_biscuit()` itself because there is the case that `biscuit_no = biscuit_used` which needs to be dealt with for retransmission handling.
 
+### Denial of Service Mitigation and Cookies
+
+Rosenpass derives its cookie-based DoS mitigation technique for a responder from Wireguard [@wg]. 
+
+When the responder is under load, it may choose to not process further handshake messages, but instead to respond with a cookie reply message (see Figure \ref{img:MessageTypes}). 
+
+The sender of the exchange then uses this cookie in order to resend the message and have it accepted the following time by the reciever. 
+
+For an initiator, Rosenpass ignores the message when under load.
+
+#### Cookie Reply Message
+
+The cookie reply message consists of the `sid` of the client under load, a random 24-byte bitstring `nonce` and encrypting `cookie_tau` into a `cookie` reply field which consists of the following (from the perspective of the cookie reply sender):
+
+```
+cookie_tau = lhash("cookie-tau",r_m, a_m)[0..16]
+cookie = XAEAD(lhash("cookie-key", spkm), nonce, cookie_tau , mac_peer)
+```
+
+where `r_m` is a secret variable that changes every two minutes to a random value. `a_m` is a concatenation of the source IP address and UDP source port of the client's peer. `cookie_tau` will result in a truncated 16 byte value from the above hash operation. `mac_peer` is the `mac` field of the peer's handshake message to which message is the reply.  
+
+#### Envelope `mac` Field
+
+Similar to `mac.1` in Wireguard handshake messages, the `mac` field of a Rosenpass envelope from a handshake packet sender's point of view consists of the following:
+
+```
+mac = lhash("mac", spkt, MAC_WIRE_DATA)[0..16]
+```
+
+where `MAC_WIRE_DATA` represents all bytes of msg prior to `mac` field in the envelope.
+
+If a client receives an invalid `mac` value for any message, it will discard the message.
+
+#### Envelope cookie field
+
+The `cookie_tau` value encrypted as part of `cookie` field in the cookie reply message is decrypted by its receiver and stored as the `last_recvd_cookie` for a limited time (120 seconds). This value is then used by the sender to append a `cookie` field to the sender's message envelope to retransmit the handshake message.  This is the equivalent of Wireguard's `mac.2` field and is determined as follows:
+
+```
+
+if (is_zero_length_bitstring(last_recvd_cookie)  ||  last_cookie_time_ellapsed >= 120) {
+    cookie = 0^16; //zeroed out 16 bytes bitstring
+}
+else {
+    cookie = lhash("cookie",last_recvd_cookie,COOKIE_WIRE_DATA)
+}
+```
+
+Here, `last_recvd_cookie` is the last received decrypted data of the `cookie` field from a cookie reply message by a hanshake message sender, `last_cookie_time_ellapsed` is the amount of time in seconds ellapsed since last cookie was received, and `COOKIE_WIRE_DATA` are the message contents of all bytes of the retransmitted message prior to the `cookie` field.
+
+The sender can use an invalid value for the `cookie` value, when the receiver is not under load, and the receiver must ignore this value.
+However, when the receiver is under load, it may reject messages with the invalid `cookie` value, and issue a cookie reply message. 
+
+### Conditions to trigger DoS Mechanism
+
+Rosenpass implementations are expected to detect conditions in which they are under computational load to trigger the cookie based DoS mitigation mechanism by replying with a cookie reply message.
+
+For the reference implemenation, Rosenpass has derived inspiration from the linux implementation of Wireguard.
+
+This implementation suggests that the reciever keep track of the number of messages it is processing at a given time. 
+
+On receiving an incoming message, if the length of the message queue to be processed exceeds a threshold `MAX_QUEUED_INCOMING_HANDSHAKES_THRESHOLD`, the client is considered under load and its state is stored as under load. In addition, the timestamp of this instant when the client was last under load is stored. When recieving subsequent messages, if the client is still in an under load state, the client will check if the time ellpased since the client was last under load has exceeded `LAST_UNDER_LOAD_WINDOW` seconds. If this is the case, the client will update its state to normal operation, and process the message in a normal fashion.
+
+Currently, the following constants are derived from the Linux kernel implementation of Wireguard:
+
+```
+MAX_QUEUED_INCOMING_HANDSHAKES_THRESHOLD = 4096
+LAST_UNDER_LOAD_WINDOW = 1 //seconds
+```
+
 ## Dealing with Packet Loss
 
 The initiator deals with packet loss by storing the messages it sends to the responder and retransmitting them in randomized, exponentially increasing intervals until they get a response. Receiving RespHello terminates retransmission of InitHello. A Data or EmptyData message serves as acknowledgement of receiving InitConf and terminates its retransmission.
 
 The responder does not need to do anything special to handle RespHello retransmission – if the RespHello package is lost, the initiator retransmits InitHello and the responder can generate another RespHello package from that. InitConf retransmission needs to be handled specifically in the responder code because accepting an InitConf retransmission would reset the live session including the nonce counter, which would cause nonce reuse. Implementations must detect the case that `biscuit_no = biscuit_used` in ICR5, skip execution of ICR6 and ICR7, and just transmit another EmptyData package to confirm that the initiator can stop transmitting InitConf.
 
+### Interaction with cookie reply system
+
+The cookie reply system does not interfere with the retransmission logic discussed above. 
+
+When the initator is under load, it will ignore processing any incoming messages.
+
+When a responder is under load, a handshake message will be discarded and a cookie reply message is sent. The initiator, then on the reciept of the cookie reply message, will store a decrypted `cookie_tau` value to use when appending a `cookie` to subsequently sent messages. As per the retransmission mechanism above, the initiator will send a retransmitted InitHello or InitConf message with a valid `cookie` value appended. On receiving the retransmitted handshake message, the responder will validate the `cookie` value and resume with the handshake process. 
+
 \printbibliography
 
 \setupimage{landscape,fullpage,label=img:HandlingCode}

rosenpass/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rosenpass"
-version = "0.2.1-rc.3"
+version = "0.2.1"
 authors = ["Karolin Varner <karo@cupdev.net>", "wucke13 <wucke13@gmail.com>"]
 edition = "2021"
 license = "MIT OR Apache-2.0"
@@ -14,29 +14,30 @@ name = "handshake"
 harness = false
 
 [dependencies]
-anyhow = { version = "1.0.71", features = ["backtrace"] }
-base64 = "0.21.1"
-static_assertions = "1.1.0"
-memoffset = "0.9.0"
-libsodium-sys-stable = { version = "1.19.28", features = ["use-pkg-config"] }
-oqs-sys = { version = "0.8", default-features = false, features = ['classic_mceliece', 'kyber'] }
-lazy_static = "1.4.0"
-thiserror = "1.0.40"
-paste = "1.0.12"
-log = { version = "0.4.17", optional = true }
-env_logger = { version = "0.10.0", optional = true }
-serde = { version = "1.0.163", features = ["derive"] }
-toml = "0.7.4"
-clap = { version = "4.3.0", features = ["derive"] }
-mio = { version = "0.8.6", features = ["net", "os-poll"] }
+rosenpass-util = { workspace = true }
+rosenpass-constant-time = { workspace = true }
+rosenpass-sodium = { workspace = true }
+rosenpass-ciphers = { workspace = true }
+rosenpass-to = { workspace = true }
+anyhow = { workspace = true }
+static_assertions = { workspace = true }
+memoffset = { workspace = true }
+libsodium-sys-stable = { workspace = true }
+oqs-sys = { workspace = true }
+lazy_static = { workspace = true }
+thiserror = { workspace = true }
+paste = { workspace = true }
+log = { workspace = true }
+env_logger = { workspace = true }
+serde = { workspace = true }
+toml = { workspace = true }
+clap = { workspace = true }
+mio = { workspace = true }
 
 [build-dependencies]
-anyhow = "1.0.71"
+anyhow = { workspace = true }
 
 [dev-dependencies]
-criterion = "0.4.0"
-test_bin = "0.4.0"
-stacker = "0.1.15"
-
-[features]
-default = ["log", "env_logger"]
+criterion = { workspace = true }
+test_bin = { workspace = true }
+stacker = { workspace = true }

rosenpass/benches/handshake.rs

@@ -3,7 +3,6 @@ use rosenpass::pqkem::KEM;
 use rosenpass::{
     pqkem::StaticKEM,
     protocol::{CryptoServer, HandleMsgResult, MsgBuf, PeerPtr, SPk, SSk, SymKey},
-    sodium::sodium_init,
 };
 
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
@@ -58,7 +57,7 @@ fn make_server_pair() -> Result<(CryptoServer, CryptoServer)> {
 }
 
 fn criterion_benchmark(c: &mut Criterion) {
-    sodium_init().unwrap();
+    rosenpass_sodium::init().unwrap();
     let (mut a, mut b) = make_server_pair().unwrap();
     c.bench_function("cca_secret_alloc", |bench| {
         bench.iter(|| {

rosenpass/src/app_server.rs

@@ -4,6 +4,7 @@ use anyhow::Result;
 use log::{debug, error, info, warn};
 use mio::Interest;
 use mio::Token;
+use rosenpass_util::file::fopen_w;
 
 use std::cell::Cell;
 use std::io::Write;
@@ -21,17 +22,23 @@ use std::process::Stdio;
 use std::slice;
 use std::thread;
 use std::time::Duration;
+use std::time::Instant;
 
-use crate::util::fopen_w;
 use crate::{
     config::Verbosity,
     protocol::{CryptoServer, MsgBuf, PeerPtr, SPk, SSk, SymKey, Timing},
-    util::{b64_writer, fmt_b64},
 };
+use rosenpass_util::attempt;
+use rosenpass_util::b64::{b64_writer, fmt_b64};
 
 const IPV4_ANY_ADDR: Ipv4Addr = Ipv4Addr::new(0, 0, 0, 0);
 const IPV6_ANY_ADDR: Ipv6Addr = Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 0);
 
+// Using values from Linux Kernel implementation
+// TODO: Customize values for rosenpass
+const MAX_QUEUED_INCOMING_HANDSHAKES_THRESHOLD: usize = 4096;
+const LAST_UNDER_LOAD_WINDOW: Duration = Duration::from_secs(1);
+
 fn ipv4_any_binding() -> SocketAddr {
     // addr, port
     SocketAddr::V4(SocketAddrV4::new(IPV4_ANY_ADDR, 0))
@@ -66,6 +73,12 @@ pub struct WireguardOut {
     pub extra_params: Vec<String>,
 }
 
+#[derive(Debug)]
+pub enum DoSOperation {
+    UnderLoad { last_under_load: Instant },
+    Normal,
+}
+
 /// Holds the state of the application, namely the external IO
 ///
 /// Responsible for file IO, network IO
@@ -79,6 +92,7 @@ pub struct AppServer {
     pub peers: Vec<AppPeer>,
     pub verbosity: Verbosity,
     pub all_sockets_drained: bool,
+    pub under_load: DoSOperation,
 }
 
 /// A socket pointer is an index assigned to a socket;
@@ -434,6 +448,7 @@ impl AppServer {
             events,
             mio_poll,
             all_sockets_drained: false,
+            under_load: DoSOperation::Normal,
         })
     }
 
@@ -548,7 +563,37 @@ impl AppServer {
                 }
 
                 ReceivedMessage(len, endpoint) => {
-                    match self.crypt.handle_msg(&rx[..len], &mut *tx) {
+                    let msg_result = match self.under_load {
+                        DoSOperation::UnderLoad { last_under_load: _ } => {
+                            //TODO: Lookup peer through addresses (hash)
+                            let index = self
+                                .peers
+                                .iter()
+                                .enumerate()
+                                .find(|(_num, p)| {
+                                    if let Some(ep) = p.endpoint() {
+                                        ep.addresses() == endpoint.addresses()
+                                    } else {
+                                        false
+                                    }
+                                })
+                                .ok_or(anyhow::anyhow!("Received message from unknown endpoint"))?
+                                .0;
+                            let socket_addr = endpoint
+                                .addresses()
+                                .first()
+                                .copied()
+                                .ok_or(anyhow::anyhow!("No socket address for endpoint"))?;
+                            self.crypt.handle_msg_under_load(
+                                &rx[..len],
+                                &mut *tx,
+                                PeerPtr(index),
+                                socket_addr,
+                            )
+                        }
+                        DoSOperation::Normal => self.crypt.handle_msg(&rx[..len], &mut *tx),
+                    };
+                    match msg_result {
                         Err(ref e) => {
                             self.verbose().then(|| {
                                 info!(
@@ -703,11 +748,29 @@ impl AppServer {
         // desired on a non-dual-stack OS), thus just checking every socket after any
         // readiness event seems to be good enough™ for now.
 
+        println!("All sockets drained: {}", self.all_sockets_drained);
         // only poll if we drained all sockets before
         if self.all_sockets_drained {
             self.mio_poll.poll(&mut self.events, Some(timeout))?;
+
+            let queue_length = self.events.iter().peekable().count();
+
+            println!("queue length: {}", queue_length);
+
+            if queue_length > MAX_QUEUED_INCOMING_HANDSHAKES_THRESHOLD {
+                self.under_load = DoSOperation::UnderLoad {
+                    last_under_load: Instant::now(),
+                }
+            }
         }
 
+        if let DoSOperation::UnderLoad { last_under_load } = self.under_load {
+            if last_under_load.elapsed() > LAST_UNDER_LOAD_WINDOW {
+                self.under_load = DoSOperation::Normal;
+            }
+        }
+
+        // drain all sockets
         let mut would_block_count = 0;
         for (sock_no, socket) in self.sockets.iter_mut().enumerate() {
             match socket.recv_from(buf) {

rosenpass/src/cli.rs

@@ -1,10 +1,10 @@
 use anyhow::{bail, ensure};
 use clap::Parser;
+use rosenpass_util::file::{LoadValue, LoadValueB64};
 use std::path::{Path, PathBuf};
 
 use crate::app_server;
 use crate::app_server::AppServer;
-use crate::util::{LoadValue, LoadValueB64};
 use crate::{
     // app_server::{AppServer, LoadValue, LoadValueB64},
     coloring::Secret,

rosenpass/src/coloring.rs

@@ -6,18 +6,23 @@
 //! - guard pages before and after each allocation trap accidential sequential reads that creep towards our secrets
 //! - the memory is mlocked, e.g. it is never swapped
 
-use crate::{
-    sodium::{rng, zeroize},
-    util::{cpy, mutating},
-};
+use anyhow::Context;
 use lazy_static::lazy_static;
 use libsodium_sys as libsodium;
+use rosenpass_util::{
+    b64::b64_reader,
+    file::{fopen_r, LoadValue, LoadValueB64, ReadExactToEnd, StoreValue},
+    functional::mutating,
+    mem::cpy,
+};
+use std::result::Result;
 use std::{
     collections::HashMap,
     convert::TryInto,
     fmt,
     ops::{Deref, DerefMut},
     os::raw::c_void,
+    path::Path,
     ptr::null_mut,
     sync::Mutex,
 };
@@ -173,12 +178,12 @@ impl<const N: usize> Secret<N> {
 
     /// Sets all data of an existing secret to null bytes
     pub fn zeroize(&mut self) {
-        zeroize(self.secret_mut());
+        rosenpass_sodium::helpers::memzero(self.secret_mut());
     }
 
     /// Sets all data an existing secret to random bytes
     pub fn randomize(&mut self) {
-        rng(self.secret_mut());
+        rosenpass_sodium::helpers::randombytes_buf(self.secret_mut());
     }
 
     /// Borrows the data
@@ -243,7 +248,7 @@ impl<const N: usize> Public<N> {
 
     /// Randomize all bytes in an existing [Public]
     pub fn randomize(&mut self) {
-        rng(&mut self.value);
+        rosenpass_sodium::helpers::randombytes_buf(&mut self.value);
     }
 }
 
@@ -359,3 +364,80 @@ mod test {
         assert_eq!(new_secret.secret(), &[0; N]);
     }
 }
+
+trait StoreSecret {
+    type Error;
+
+    fn store_secret<P: AsRef<Path>>(&self, path: P) -> Result<(), Self::Error>;
+}
+
+impl<T: StoreValue> StoreSecret for T {
+    type Error = <T as StoreValue>::Error;
+
+    fn store_secret<P: AsRef<Path>>(&self, path: P) -> Result<(), Self::Error> {
+        self.store(path)
+    }
+}
+
+impl<const N: usize> LoadValue for Secret<N> {
+    type Error = anyhow::Error;
+
+    fn load<P: AsRef<Path>>(path: P) -> anyhow::Result<Self> {
+        let mut v = Self::random();
+        let p = path.as_ref();
+        fopen_r(p)?
+            .read_exact_to_end(v.secret_mut())
+            .with_context(|| format!("Could not load file {p:?}"))?;
+        Ok(v)
+    }
+}
+
+impl<const N: usize> LoadValueB64 for Secret<N> {
+    type Error = anyhow::Error;
+
+    fn load_b64<P: AsRef<Path>>(path: P) -> anyhow::Result<Self> {
+        use std::io::Read;
+
+        let mut v = Self::random();
+        let p = path.as_ref();
+        // This might leave some fragments of the secret on the stack;
+        // in practice this is likely not a problem because the stack likely
+        // will be overwritten by something else soon but this is not exactly
+        // guaranteed. It would be possible to remedy this, but since the secret
+        // data will linger in the Linux page cache anyways with the current
+        // implementation, going to great length to erase the secret here is
+        // not worth it right now.
+        b64_reader(&mut fopen_r(p)?)
+            .read_exact(v.secret_mut())
+            .with_context(|| format!("Could not load base64 file {p:?}"))?;
+        Ok(v)
+    }
+}
+
+impl<const N: usize> StoreSecret for Secret<N> {
+    type Error = anyhow::Error;
+
+    fn store_secret<P: AsRef<Path>>(&self, path: P) -> anyhow::Result<()> {
+        std::fs::write(path, self.secret())?;
+        Ok(())
+    }
+}
+
+impl<const N: usize> LoadValue for Public<N> {
+    type Error = anyhow::Error;
+
+    fn load<P: AsRef<Path>>(path: P) -> anyhow::Result<Self> {
+        let mut v = Self::random();
+        fopen_r(path)?.read_exact_to_end(&mut *v)?;
+        Ok(v)
+    }
+}
+
+impl<const N: usize> StoreValue for Public<N> {
+    type Error = anyhow::Error;
+
+    fn store<P: AsRef<Path>>(&self, path: P) -> anyhow::Result<()> {
+        std::fs::write(path, **self)?;
+        Ok(())
+    }
+}

rosenpass/src/config.rs

@@ -7,10 +7,9 @@ use std::{
 };
 
 use anyhow::{bail, ensure};
+use rosenpass_util::file::fopen_w;
 use serde::{Deserialize, Serialize};
 
-use crate::util::fopen_w;
-
 #[derive(Debug, Serialize, Deserialize)]
 pub struct Rosenpass {
     pub public_key: PathBuf,

rosenpass/src/labeled_prf.rs

@@ -1,10 +1,10 @@
 //! Pseudo Random Functions (PRFs) with a tree-like label scheme which
 //! ensures their uniqueness
 
-use {
-    crate::{prftree::PrfTree, sodium::KEY_SIZE},
-    anyhow::Result,
-};
+
+use crate::prftree::PrfTree;
+use anyhow::Result;
+use rosenpass_ciphers::KEY_LEN;
 
 pub fn protocol() -> Result<PrfTree> {
     PrfTree::zero().mix("Rosenpass v1 mceliece460896 Kyber512 ChaChaPoly1305 BLAKE2s".as_bytes())
@@ -23,6 +23,8 @@ macro_rules! prflabel {
 
 prflabel!(protocol, mac, "mac");
 prflabel!(protocol, cookie, "cookie");
+prflabel!(protocol, cookie_tau, "cookie-tau");
+prflabel!(protocol, cookie_key, "cookie-key");
 prflabel!(protocol, peerid, "peer id");
 prflabel!(protocol, biscuit_ad, "biscuit additional data");
 prflabel!(protocol, ckinit, "chaining key init");
@@ -30,7 +32,7 @@ prflabel!(protocol, _ckextract, "chaining key extract");
 
 macro_rules! prflabel_leaf {
     ($base:ident, $name:ident, $($lbl:expr),* ) => {
-        pub fn $name() -> Result<[u8; KEY_SIZE]> {
+        pub fn $name() -> Result<[u8; KEY_LEN]> {
             let t = $base()?;
             $( let t = t.mix($lbl.as_bytes())?; )*
             Ok(t.into_value())

rosenpass/src/lib.rs

@@ -1,7 +1,3 @@
-#[macro_use]
-pub mod util;
-#[macro_use]
-pub mod sodium;
 pub mod coloring;
 #[rustfmt::skip]
 pub mod labeled_prf;

rosenpass/src/lprf.rs

@@ -1,107 +0,0 @@
-//! The rosenpass protocol relies on a special type
-//! of hash function for most of its hashing or
-//! message authentication needs: an incrementable
-//! pseudo random function.
-//!
-//! This is a generalization of a PRF operating
-//! on a sequence of inputs instead of a single input.
-//!
-//! Like a Dec function the Iprf features efficient
-//! incrementability.
-//!
-//! You can also think of an Iprf as a Dec function with
-//! a fixed size output.
-//!
-//! The idea behind a Iprf is that it can be efficiently
-//! constructed from an Dec function as well as a PRF.
-//!
-//! TODO Base the construction on a proper Dec function
-
-pub struct Iprf([u8; KEY_SIZE]);
-pub struct IprfBranch([u8; KEY_SIZE]);
-pub struct SecretIprf(Secret<KEY_SIZE>);
-pub struct SecretIprfBranch(Secret<KEY_SIZE>);
-
-pub fn prf_into(out: &mut [u8], key: &[u8], data: &[u8]) {
-    // TODO: The error handling with sodium is a scurge
-    hmac_into(out, key, data).unwrap()
-}
-
-pub fn prf(key: &[u8], data: &[u8]) -> [u8; KEY_SIZE] {
-    mutating([0u8; KEY_SIZE], |r| prf_into(r, key, data))
-}
-
-impl Iprf {
-    fn zero() -> Self {
-        Self([0u8; KEY_SIZE])
-    }
-
-    fn dup(self) -> IprfBranch {
-        IprfBranch(self.0)
-    }
-
-    // TODO: Protocol! Use domain separation to ensure that
-    fn mix(self, v: &[u8]) -> Self {
-        Self(prf(&self.0, v))
-    }
-
-    fn mix_secret<const N: usize>(self, v: Secret<N>) -> SecretIprf {
-        SecretIprf::prf_invoc(&self.0, v.secret())
-    }
-
-    fn into_value(self) -> [u8; KEY_SIZE] {
-        self.0
-    }
-
-    fn extract(self, v: &[u8], dst: &mut [u8]) {
-        prf_into(&self.0, v, dst)
-    }
-}
-
-impl IprfBranch {
-    fn mix(&self, v: &[u8]) -> Iprf {
-        Iprf(prf(self.0, v))
-    }
-
-    fn mix_secret<const N: usize>(&self, v: Secret<N>) -> SecretIprf {
-        SecretIprf::prf_incov(self.0, v.secret())
-    }
-}
-
-impl SecretIprf {
-    fn prf_invoc(k: &[u8], d: &[u8]) -> SecretIprf {
-        mutating(SecretIprf(Secret::zero()), |r| {
-            prf_into(k, d, r.secret_mut())
-        })
-    }
-
-    fn from_key(k: Secret<N>) -> SecretIprf {
-        Self(k)
-    }
-
-    fn mix(self, v: &[u8]) -> SecretIprf {
-        Self::prf_invoc(self.0.secret(), v)
-    }
-
-    fn mix_secret<const N: usize>(self, v: Secret<N>) -> SecretIprf {
-        Self::prf_invoc(self.0.secret(), v.secret())
-    }
-
-    fn into_secret(self) -> Secret<KEY_SIZE> {
-        self.0
-    }
-
-    fn into_secret_slice(self, v: &[u8], dst: &[u8]) {
-        prf_into(self.0.secret(), v, dst)
-    }
-}
-
-impl SecretIprfBranch {
-    fn mix(&self, v: &[u8]) -> SecretIprf {
-        SecretIprf::prf_invoc(self.0.secret(), v)
-    }
-
-    fn mix_secret<const N: usize>(&self, v: Secret<N>) -> SecretIprf {
-        SecretIprf::prf_invoc(self.0.secret(), v.secret())
-    }
-}

rosenpass/src/main.rs

@@ -1,11 +1,18 @@
 use log::error;
-use rosenpass::{cli::Cli, sodium::sodium_init};
+use rosenpass::cli::Cli;
+use rosenpass_util::attempt;
 use std::process::exit;
 
 /// Catches errors, prints them through the logger, then exits
 pub fn main() {
     env_logger::init();
-    match sodium_init().and_then(|()| Cli::run()) {
+
+    let res = attempt!({
+        rosenpass_sodium::init()?;
+        Cli::run()
+    });
+
+    match res {
         Ok(_) => {}
         Err(e) => {
             error!("{e}");

rosenpass/src/msgs.rs

@@ -44,7 +44,11 @@
 //! ```
 
 use super::RosenpassError;
-use crate::{pqkem::*, sodium};
+use crate::pqkem::*;
+use rosenpass_ciphers::{aead, xaead};
+
+pub const MAC_SIZE: usize = 16;
+pub const COOKIE_SIZE: usize = 16;
 
 // Macro magic ////////////////////////////////////////////////////////////////
 
@@ -264,9 +268,9 @@ data_lense! { Envelope<M> :=
     payload: M::LEN,
     /// Message Authentication Code (mac) over all bytes until (exclusive)
     /// `mac` itself
-    mac: sodium::MAC_SIZE,
-    /// Currently unused, TODO: do something with this
-    cookie: sodium::MAC_SIZE
+    mac: MAC_SIZE,
+    /// Cookie value
+    cookie: COOKIE_SIZE
 }
 
 data_lense! { InitHello :=
@@ -277,9 +281,9 @@ data_lense! { InitHello :=
     /// Classic McEliece Ciphertext
     sctr: StaticKEM::CT_LEN,
     /// Encryped: 16 byte hash of McEliece initiator static key
-    pidic: sodium::AEAD_TAG_LEN + 32,
+    pidic: aead::TAG_LEN + 32,
     /// Encrypted TAI64N Time Stamp (against replay attacks)
-    auth: sodium::AEAD_TAG_LEN
+    auth: aead::TAG_LEN
 }
 
 data_lense! { RespHello :=
@@ -292,7 +296,7 @@ data_lense! { RespHello :=
     /// Classic McEliece Ciphertext
     scti: StaticKEM::CT_LEN,
     /// Empty encrypted message (just an auth tag)
-    auth: sodium::AEAD_TAG_LEN,
+    auth: aead::TAG_LEN,
     /// Responders handshake state in encrypted form
     biscuit: BISCUIT_CT_LEN
 }
@@ -305,7 +309,7 @@ data_lense! { InitConf :=
     /// Responders handshake state in encrypted form
     biscuit: BISCUIT_CT_LEN,
     /// Empty encrypted message (just an auth tag)
-    auth: sodium::AEAD_TAG_LEN
+    auth: aead::TAG_LEN
 }
 
 data_lense! { EmptyData :=
@@ -314,16 +318,16 @@ data_lense! { EmptyData :=
     /// Nonce
     ctr: 8,
     /// Empty encrypted message (just an auth tag)
-    auth: sodium::AEAD_TAG_LEN
+    auth: aead::TAG_LEN
 }
 
 data_lense! { Biscuit :=
     /// H(spki) – Ident ifies the initiator
-    pidi: sodium::KEY_SIZE,
+    pidi: aead::KEY_LEN,
     /// The biscuit number (replay protection)
     biscuit_no: 12,
     /// Chaining key
-    ck: sodium::KEY_SIZE
+    ck: aead::KEY_LEN
 }
 
 data_lense! { DataMsg :=
@@ -331,7 +335,9 @@ data_lense! { DataMsg :=
 }
 
 data_lense! { CookieReply :=
-    dummy: 4
+    sid: 4,
+    nonce: xaead::NONCE_LEN,
+    cookie_encrypted: MAC_SIZE + xaead::TAG_LEN
 }
 
 // Traits /////////////////////////////////////////////////////////////////////
@@ -384,30 +390,28 @@ impl TryFrom<u8> for MsgType {
 pub const BISCUIT_PT_LEN: usize = Biscuit::<()>::LEN;
 
 /// Length in bytes of an encrypted Biscuit (cipher text)
-pub const BISCUIT_CT_LEN: usize = BISCUIT_PT_LEN + sodium::XAEAD_NONCE_LEN + sodium::XAEAD_TAG_LEN;
+pub const BISCUIT_CT_LEN: usize = BISCUIT_PT_LEN + xaead::NONCE_LEN + xaead::TAG_LEN;
 
 #[cfg(test)]
 mod test_constants {
-    use crate::{
-        msgs::{BISCUIT_CT_LEN, BISCUIT_PT_LEN},
-        sodium,
-    };
+    use crate::msgs::{BISCUIT_CT_LEN, BISCUIT_PT_LEN};
+    use rosenpass_ciphers::{xaead, KEY_LEN};
 
     #[test]
     fn sodium_keysize() {
-        assert_eq!(sodium::KEY_SIZE, 32);
+        assert_eq!(KEY_LEN, 32);
     }
 
     #[test]
     fn biscuit_pt_len() {
-        assert_eq!(BISCUIT_PT_LEN, 2 * sodium::KEY_SIZE + 12);
+        assert_eq!(BISCUIT_PT_LEN, 2 * KEY_LEN + 12);
     }
 
     #[test]
     fn biscuit_ct_len() {
         assert_eq!(
             BISCUIT_CT_LEN,
-            BISCUIT_PT_LEN + sodium::XAEAD_NONCE_LEN + sodium::XAEAD_TAG_LEN
+            BISCUIT_PT_LEN + xaead::NONCE_LEN + xaead::TAG_LEN
         );
     }
 }

rosenpass/src/prftree.rs

@@ -1,25 +1,23 @@
 //! Implementation of the tree-like structure used for the label derivation in [labeled_prf](crate::labeled_prf)
-use {
-    crate::{
-        coloring::Secret,
-        sodium::{hmac, hmac_into, KEY_SIZE},
-    },
-    anyhow::Result,
-};
+use crate::coloring::Secret;
+
+use anyhow::Result;
+use rosenpass_ciphers::{hash, KEY_LEN};
+use rosenpass_to::To;
 
 // TODO Use a proper Dec interface
 #[derive(Clone, Debug)]
-pub struct PrfTree([u8; KEY_SIZE]);
+pub struct PrfTree([u8; KEY_LEN]);
 #[derive(Clone, Debug)]
-pub struct PrfTreeBranch([u8; KEY_SIZE]);
+pub struct PrfTreeBranch([u8; KEY_LEN]);
 #[derive(Clone, Debug)]
-pub struct SecretPrfTree(Secret<KEY_SIZE>);
+pub struct SecretPrfTree(Secret<KEY_LEN>);
 #[derive(Clone, Debug)]
-pub struct SecretPrfTreeBranch(Secret<KEY_SIZE>);
+pub struct SecretPrfTreeBranch(Secret<KEY_LEN>);
 
 impl PrfTree {
     pub fn zero() -> Self {
-        Self([0u8; KEY_SIZE])
+        Self([0u8; KEY_LEN])
     }
 
     pub fn dup(self) -> PrfTreeBranch {
@@ -32,21 +30,21 @@ impl PrfTree {
 
     // TODO: Protocol! Use domain separation to ensure that
     pub fn mix(self, v: &[u8]) -> Result<Self> {
-        Ok(Self(hmac(&self.0, v)?))
+        Ok(Self(hash::hash(&self.0, v).collect::<[u8; KEY_LEN]>()?))
     }
 
     pub fn mix_secret<const N: usize>(self, v: Secret<N>) -> Result<SecretPrfTree> {
         SecretPrfTree::prf_invoc(&self.0, v.secret())
     }
 
-    pub fn into_value(self) -> [u8; KEY_SIZE] {
+    pub fn into_value(self) -> [u8; KEY_LEN] {
         self.0
     }
 }
 
 impl PrfTreeBranch {
     pub fn mix(&self, v: &[u8]) -> Result<PrfTree> {
-        Ok(PrfTree(hmac(&self.0, v)?))
+        Ok(PrfTree(hash::hash(&self.0, v).collect::<[u8; KEY_LEN]>()?))
     }
 
     pub fn mix_secret<const N: usize>(&self, v: Secret<N>) -> Result<SecretPrfTree> {
@@ -57,7 +55,7 @@ impl PrfTreeBranch {
 impl SecretPrfTree {
     pub fn prf_invoc(k: &[u8], d: &[u8]) -> Result<SecretPrfTree> {
         let mut r = SecretPrfTree(Secret::zero());
-        hmac_into(r.0.secret_mut(), k, d)?;
+        hash::hash(k, d).to(r.0.secret_mut())?;
         Ok(r)
     }
 
@@ -69,7 +67,7 @@ impl SecretPrfTree {
         SecretPrfTreeBranch(self.0)
     }
 
-    pub fn danger_from_secret(k: Secret<KEY_SIZE>) -> Self {
+    pub fn danger_from_secret(k: Secret<KEY_LEN>) -> Self {
         Self(k)
     }
 
@@ -81,12 +79,12 @@ impl SecretPrfTree {
         Self::prf_invoc(self.0.secret(), v.secret())
     }
 
-    pub fn into_secret(self) -> Secret<KEY_SIZE> {
+    pub fn into_secret(self) -> Secret<KEY_LEN> {
         self.0
     }
 
     pub fn into_secret_slice(mut self, v: &[u8], dst: &[u8]) -> Result<()> {
-        hmac_into(self.0.secret_mut(), v, dst)
+        hash::hash(v, dst).to(self.0.secret_mut())
     }
 }
 
@@ -102,7 +100,7 @@ impl SecretPrfTreeBranch {
     // TODO: This entire API is not very nice; we need this for biscuits, but
     // it might be better to extract a special "biscuit"
     // labeled subkey and reinitialize the chain with this
-    pub fn danger_into_secret(self) -> Secret<KEY_SIZE> {
+    pub fn danger_into_secret(self) -> Secret<KEY_LEN> {
         self.0
     }
 }

rosenpass/src/protocol.rs

@@ -25,8 +25,8 @@
 //! };
 //! # fn main() -> anyhow::Result<()> {
 //!
-//! // always init libsodium before anything
-//! rosenpass::sodium::sodium_init()?;
+//! // always initialize libsodium before anything
+//! rosenpass_sodium::init()?;
 //!
 //! // initialize secret and public key for peer a ...
 //! let (mut peer_a_sk, mut peer_a_pk) = (SSk::zero(), SPk::zero());
@@ -69,18 +69,19 @@
 
 use crate::{
     coloring::*,
-    labeled_prf as lprf,
+    labeled_prf::{self as lprf},
     msgs::*,
     pqkem::*,
     prftree::{SecretPrfTree, SecretPrfTreeBranch},
-    sodium::*,
-    util::*,
 };
 use anyhow::{bail, ensure, Context, Result};
+use rosenpass_ciphers::{aead, xaead, KEY_LEN};
+use rosenpass_util::{cat, mem::cpy_min, ord::max_usize, time::Timebase};
 use std::collections::hash_map::{
     Entry::{Occupied, Vacant},
     HashMap,
 };
+use std::net::{IpAddr, SocketAddr};
 
 // CONSTANTS & SETTINGS //////////////////////////
 
@@ -109,6 +110,16 @@ pub const REKEY_AFTER_TIME_RESPONDER: Timing = 120.0;
 pub const REKEY_AFTER_TIME_INITIATOR: Timing = 130.0;
 pub const REJECT_AFTER_TIME: Timing = 180.0;
 
+// From the wireguard paper; "under no circumstances send an initiation message more than once every 5 seconds"
+pub const REKEY_TIMEOUT: Timing = 5.0;
+
+// Cookie Secret value Rm composing `cookie_tau` in the whitepaper
+pub const COOKIE_SECRET_LEN: usize = MAC_SIZE;
+pub const COOKIE_SECRET_EXP: Timing = 120.0;
+
+// Peer Cookie Tau expiration
+pub const PEER_COOKIE_TAU_EXP: Timing = 120.0;
+
 // Seconds until the biscuit key is changed; we issue biscuits
 // using one biscuit key for one epoch and store the biscuit for
 // decryption for a second epoch
@@ -144,14 +155,14 @@ pub type SSk = Secret<{ StaticKEM::SK_LEN }>;
 pub type EPk = Public<{ EphemeralKEM::PK_LEN }>;
 pub type ESk = Secret<{ EphemeralKEM::SK_LEN }>;
 
-pub type SymKey = Secret<KEY_SIZE>;
-pub type SymHash = Public<KEY_SIZE>;
+pub type SymKey = Secret<KEY_LEN>;
+pub type SymHash = Public<KEY_LEN>;
 
-pub type PeerId = Public<KEY_SIZE>;
+pub type PeerId = Public<KEY_LEN>;
 pub type SessionId = Public<SESSION_ID_LEN>;
 pub type BiscuitId = Public<BISCUIT_ID_LEN>;
 
-pub type XAEADNonce = Public<XAEAD_NONCE_LEN>;
+pub type XAEADNonce = Public<{ xaead::NONCE_LEN }>;
 
 pub type MsgBuf = Public<MAX_MESSAGE_LEN>;
 
@@ -184,6 +195,89 @@ pub struct CryptoServer {
 
     // Tick handling
     pub peer_poll_off: usize,
+
+    // Random state which changes every COOKIE_SECRET_EXP seconds
+    pub cookie_secret: CookieSecret,
+}
+
+#[derive(Debug)]
+pub enum CookieSecret {
+    Some {
+        value: [u8; COOKIE_SECRET_LEN],
+        last_updated: Timebase,
+    },
+    None,
+}
+
+impl CookieSecret {
+    pub fn new(value: [u8; COOKIE_SECRET_LEN]) -> Self {
+        Self::Some {
+            value,
+            last_updated: Timebase::default(),
+        }
+    }
+
+    // Get the cookie secret, does not update the value
+    pub fn get(&self, expiry: Timing) -> Option<&[u8]> {
+        if let CookieSecret::Some {
+            value: _value,
+            last_updated,
+        } = self
+        {
+            if last_updated.now() > expiry {
+                return None;
+            }
+        }
+
+        match self {
+            CookieSecret::Some { value, .. } => Some(value),
+            CookieSecret::None => None,
+        }
+    }
+
+    // Get the cookie secret or update the value if it has expired and return the updated value
+    pub fn get_or_update_ellapsed<F: Fn(&mut [u8])>(
+        &mut self,
+        expiry: Timing,
+        update_fn: F,
+    ) -> &[u8] {
+        if let CookieSecret::Some {
+            value,
+            last_updated,
+        } = self
+        {
+            if last_updated.now() > expiry {
+                update_fn(value);
+                *last_updated = Timebase::default();
+            }
+            value
+        } else {
+            *self = CookieSecret::Some {
+                value: [0; COOKIE_SECRET_LEN],
+                last_updated: Timebase::default(),
+            };
+            let value = match self {
+                CookieSecret::Some {
+                    value,
+                    last_updated: _,
+                } => value,
+                CookieSecret::None => unreachable!(),
+            };
+            update_fn(value);
+            value
+        }
+    }
+
+    pub fn is_some(&self) -> bool {
+        match self {
+            CookieSecret::Some { .. } => true,
+            CookieSecret::None => false,
+        }
+    }
+
+    pub fn is_none(&self) -> bool {
+        !self.is_some()
+    }
 }
 
 /// A Biscuit is like a fancy cookie. To avoid state disruption attacks,
@@ -211,6 +305,8 @@ pub struct Peer {
     pub session: Option<Session>,
     pub handshake: Option<InitiatorHandshake>,
     pub initiation_requested: bool,
+    pub cookie_tau: CookieSecret,
+    pub last_sent_mac: Option<Public<MAC_SIZE>>,
 }
 
 impl Peer {
@@ -222,6 +318,8 @@ impl Peer {
             session: None,
             initiation_requested: false,
             handshake: None,
+            cookie_tau: CookieSecret::None,
+            last_sent_mac: None,
         }
     }
 }
@@ -449,6 +547,7 @@ impl CryptoServer {
             peers: Vec::new(),
             index: HashMap::new(),
             peer_poll_off: 0,
+            cookie_secret: CookieSecret::None,
         }
     }
 
@@ -482,6 +581,8 @@ impl CryptoServer {
             session: None,
             handshake: None,
             initiation_requested: false,
+            cookie_tau: CookieSecret::None,
+            last_sent_mac: None,
         };
         let peerid = peer.pidt()?;
         let peerno = self.peers.len();
@@ -584,6 +685,8 @@ impl Peer {
             session: None,
             handshake: None,
             initiation_requested: false,
+            cookie_tau: CookieSecret::None,
+            last_sent_mac: None,
         }
     }
 
@@ -753,7 +856,122 @@ pub struct HandleMsgResult {
 }
 
 impl CryptoServer {
-    /// Respond to an incoming message
+    /// Process a message under load
+    /// This is one of the main entry point for the protocol.
+    /// Keeps track of messages processed, and qualifies messages using
+    /// cookie based DoS mitigation. Dispatches message for further processing
+    /// to `process_msg` handler if cookie is valid, otherwise sends a cookie reply
+    /// message for sender to process and verify for messages part of the handshake phase
+    /// (i.e. InitHello, InitConf messages only). Bails on messages sent by responder and
+    /// non-handshake messages.
+    pub fn handle_msg_under_load(
+        &mut self,
+        rx_buf: &[u8],
+        tx_buf: &mut [u8],
+        peer: PeerPtr,
+        socket_addr: SocketAddr,
+    ) -> Result<HandleMsgResult> {
+        //Check cookie value
+        let mut ip_addr_port = match socket_addr.ip() {
+            IpAddr::V4(ipv4) => ipv4.octets().to_vec(),
+            IpAddr::V6(ipv6) => ipv6.octets().to_vec(),
+        };
+
+        ip_addr_port.extend_from_slice(&socket_addr.port().to_be_bytes());
+
+        let (rx_bytes_til_cookie, rx_cookie, rx_mac, rx_sid) = match rx_buf[0].try_into() {
+            Ok(MsgType::InitHello) => {
+                let msg_in = rx_buf.envelope::<InitHello<&[u8]>>()?;
+                (
+                    msg_in.until_cookie().to_vec(),
+                    msg_in.cookie().to_vec(),
+                    msg_in.mac().to_vec(),
+                    msg_in.payload().init_hello()?.sidi().to_vec(),
+                )
+            }
+            Ok(MsgType::InitConf) => {
+                let msg_in = rx_buf.envelope::<InitConf<&[u8]>>()?;
+                (
+                    msg_in.until_cookie().to_vec(),
+                    msg_in.cookie().to_vec(),
+                    msg_in.mac().to_vec(),
+                    msg_in.payload().init_conf()?.sidi().to_vec(),
+                )
+            }
+            Ok(_) => {
+                bail!("Message did not contain cookie or could not be sent a cookie reply message (responder sent-message or non-handshake)")
+            }
+            Err(_) => {
+                bail!("Message type not supported")
+            }
+        };
+
+        let cookie_tau = lprf::cookie_tau()?
+            .mix(self.cookie_secret.get_or_update_ellapsed(
+                COOKIE_SECRET_EXP,
+                rosenpass_sodium::helpers::randombytes_buf,
+            ))?
+            .mix(&ip_addr_port)?
+            .into_value()[..16]
+            .to_vec();
+
+        let expected = lprf::cookie()?
+            .mix(&cookie_tau)?
+            .mix(&rx_bytes_til_cookie)?
+            .into_value()[..16]
+            .to_vec();
+
+        //If valid cookie is found, process message
+        if rosenpass_sodium::helpers::memcmp(&rx_cookie, &expected) {
+            let result = self.handle_msg(rx_buf, tx_buf)?;
+            Ok(result)
+        }
+        //Otherwise send cookie reply
+        else {
+            let mut msg_out = tx_buf.envelope_truncating::<CookieReply<&mut [u8]>>()?;
+            let cookie_key = lprf::cookie_key()?.mix(self.spkm.secret())?.into_value();
+
+            let mut cookie_reply_lens = msg_out.payload_mut().cookie_reply()?;
+            let nonce_val = XAEADNonce::random();
+
+            // Copy sender's session id to cookie reply message
+            {
+                let sid = cookie_reply_lens.sid_mut();
+                sid.copy_from_slice(&rx_sid[..]);
+            }
+
+            // Generate random nonce, copy it to message and nonce_val
+            {
+                let nonce = cookie_reply_lens.nonce_mut();
+                nonce.copy_from_slice(&nonce_val.value);
+            }
+
+            // Encrypt cookie
+            {
+                const COOKIE_LENS_SID_LEN: usize = 4;
+                let cookie_ciphertext =
+                    &mut cookie_reply_lens.all_bytes_mut()[COOKIE_LENS_SID_LEN..];
+                xaead::encrypt(
+                    cookie_ciphertext,
+                    &cookie_key,
+                    &nonce_val.value,
+                    &rx_mac,
+                    &cookie_tau,
+                )?;
+            }
+
+            // length of the response
+            let len = Some(self.seal_and_commit_msg(peer, MsgType::CookieReply, msg_out)?);
+
+            Ok(HandleMsgResult {
+                exchanged_with: None,
+                resp: len,
+            })
+        }
+    }
+
+    /// Handle an incoming message
+    /// This is one of the main entry point for the protocol.
     ///
     /// # Overview
     ///
@@ -837,7 +1055,14 @@ impl CryptoServer {
                 self.handle_resp_conf(msg_in.payload().empty_data()?)?
             }
             Ok(MsgType::DataMsg) => bail!("DataMsg handling not implemented!"),
-            Ok(MsgType::CookieReply) => bail!("CookieReply handling not implemented!"),
+            Ok(MsgType::CookieReply) => {
+                let msg_in = rx_buf.envelope::<CookieReply<&[u8]>>()?;
+                ensure!(msg_in.check_seal(self)?, seal_broken);
+
+                let peer = self.handle_cookie_reply(msg_in.payload().cookie_reply()?)?;
+                len = 0;
+                peer
+            }
             Err(_) => {
                 bail!("CookieReply handling not implemented!")
             }
@@ -850,7 +1075,8 @@ impl CryptoServer {
     }
 
     /// Serialize message to `tx_buf`, generating the `mac` in the process of
-    /// doing so
+    /// doing so. If `cookie_secret` is also present, a `cookie` value is also generated
+    /// and added to the message
     ///
     /// The message type is explicitly required here because it is very easy to
     /// forget setting that, which creates subtle but far ranging errors.
@@ -862,6 +1088,15 @@ impl CryptoServer {
     ) -> Result<usize> {
         msg.msg_type_mut()[0] = msg_type as u8;
         msg.seal(peer, self)?;
+        msg.seal_cookie(peer, self)?;
+
+        //Store sent mac value as last sent mac (for cookie reply)
+        let mut mac = [0u8; MAC_SIZE];
+        mac.copy_from_slice(msg.mac());
+
+        peer.get_mut(self)
+            .last_sent_mac
+            .replace(Public { value: mac });
         Ok(<Envelope<(), M> as LenseView>::LEN)
     }
 }
@@ -1131,12 +1366,22 @@ impl IniHsPtr {
     }
 
     pub fn apply_retransmission(&self, srv: &mut CryptoServer, tx_buf: &mut [u8]) -> Result<usize> {
-        let ih = self
-            .get_mut(srv)
-            .as_mut()
-            .with_context(|| format!("No current handshake for peer {:?}", self.peer()))?;
-        cpy_min(&ih.tx_buf[..ih.tx_len], tx_buf);
-        Ok(ih.tx_len)
+        let ih_tx_len: usize;
+
+        {
+            let ih = self
+                .get_mut(srv)
+                .as_mut()
+                .with_context(|| format!("No current handshake for peer {:?}", self.peer()))?;
+            cpy_min(&ih.tx_buf[..ih.tx_len], tx_buf);
+            ih_tx_len = ih.tx_len;
+        }
+
+        // Add cookie to retransmitted message
+        let mut envelope = tx_buf.envelope_truncating::<InitHello<&mut [u8]>>()?;
+        envelope.seal_cookie(self.peer(), srv)?;
+
+        Ok(ih_tx_len)
     }
 
     pub fn register_retransmission(&self, srv: &mut CryptoServer) -> Result<()> {
@@ -1154,7 +1399,7 @@ impl IniHsPtr {
                         .min(ih.tx_count as f64),
                 )
                 * RETRANSMIT_DELAY_JITTER
-                * (rand_f64() + 1.0);
+                * (rosenpass_sodium::helpers::rand_f64() + 1.0); // TODO: Replace with the rand crate
         ih.tx_count += 1;
         Ok(())
     }
@@ -1181,6 +1426,16 @@ where
             .copy_from_slice(mac.into_value()[..16].as_ref());
         Ok(())
     }
+
+    /// Calculate and append the cookie value if `cookie_tau` exists (`cookie`)
+    pub fn seal_cookie(&mut self, peer: PeerPtr, srv: &CryptoServer) -> Result<()> {
+        if let Some(cookie_tau) = peer.get(srv).cookie_tau.get(PEER_COOKIE_TAU_EXP) {
+            let cookie = lprf::cookie()?.mix(cookie_tau)?.mix(self.until_cookie())?;
+            self.cookie_mut()
+                .copy_from_slice(cookie.into_value()[..16].as_ref());
+        }
+        Ok(())
+    }
 }
 
 impl<M> Envelope<&[u8], M>
@@ -1190,7 +1445,10 @@ where
     /// Check the message authentication code
     pub fn check_seal(&self, srv: &CryptoServer) -> Result<bool> {
         let expected = lprf::mac()?.mix(srv.spkm.secret())?.mix(self.until_mac())?;
-        Ok(sodium_memcmp(self.mac(), &expected.into_value()[..16]))
+        Ok(rosenpass_sodium::helpers::memcmp(
+            self.mac(),
+            &expected.into_value()[..16],
+        ))
     }
 }
 
@@ -1236,13 +1494,13 @@ impl HandshakeState {
 
     pub fn encrypt_and_mix(&mut self, ct: &mut [u8], pt: &[u8]) -> Result<&mut Self> {
         let k = self.ck.mix(&lprf::hs_enc()?)?.into_secret();
-        aead_enc_into(ct, k.secret(), &NONCE0, &NOTHING, pt)?;
+        aead::encrypt(ct, k.secret(), &[0u8; aead::NONCE_LEN], &[], pt)?;
         self.mix(ct)
     }
 
     pub fn decrypt_and_mix(&mut self, pt: &mut [u8], ct: &[u8]) -> Result<&mut Self> {
         let k = self.ck.mix(&lprf::hs_enc()?)?.into_secret();
-        aead_dec_into(pt, k.secret(), &NONCE0, &NOTHING, ct)?;
+        aead::decrypt(pt, k.secret(), &[0u8; aead::NONCE_LEN], &[], ct)?;
         self.mix(ct)
     }
 
@@ -1294,7 +1552,7 @@ impl HandshakeState {
             .into_value();
 
         // consume biscuit no
-        sodium_bigint_inc(&mut *srv.biscuit_ctr);
+        rosenpass_sodium::helpers::increment(&mut *srv.biscuit_ctr);
 
         // The first bit of the nonce indicates which biscuit key was used
         // TODO: This is premature optimization. Remove!
@@ -1305,7 +1563,7 @@ impl HandshakeState {
 
         let k = bk.get(srv).key.secret();
         let pt = biscuit.all_bytes();
-        xaead_enc_into(biscuit_ct, k, &*n, &ad, pt)?;
+        xaead::encrypt(biscuit_ct, k, &*n, &ad, pt)?;
 
         self.mix(biscuit_ct)
     }
@@ -1331,7 +1589,7 @@ impl HandshakeState {
         // Allocate and decrypt the biscuit data
         let mut biscuit = Secret::<BISCUIT_PT_LEN>::zero(); // pt buf
         let mut biscuit = (&mut biscuit.secret_mut()[..]).biscuit()?; // slice
-        xaead_dec_into(
+        xaead::decrypt(
             biscuit.all_bytes_mut(),
             bk.get(srv).key.secret(),
             &ad,
@@ -1357,7 +1615,8 @@ impl HandshakeState {
         // indicates retransmission
         // TODO: Handle retransmissions without involving the crypto code
         ensure!(
-            sodium_bigint_cmp(biscuit.biscuit_no(), &*peer.get(srv).biscuit_used) >= 0,
+            rosenpass_sodium::helpers::compare(biscuit.biscuit_no(), &*peer.get(srv).biscuit_used)
+                >= 0,
             "Rejecting biscuit: Outdated biscuit number"
         );
 
@@ -1443,7 +1702,7 @@ impl CryptoServer {
             .mix(peer.get(self).psk.secret())?;
 
         // IHI8
-        hs.core.encrypt_and_mix(ih.auth_mut(), &NOTHING)?;
+        hs.core.encrypt_and_mix(ih.auth_mut(), &[])?;
 
         // Update the handshake hash last (not changing any state on prior error
         peer.hs().insert(self, hs)?;
@@ -1509,7 +1768,7 @@ impl CryptoServer {
         core.store_biscuit(self, peer, rh.biscuit_mut())?;
 
         // RHR7
-        core.encrypt_and_mix(rh.auth_mut(), &NOTHING)?;
+        core.encrypt_and_mix(rh.auth_mut(), &[])?;
 
         Ok(peer)
     }
@@ -1595,7 +1854,7 @@ impl CryptoServer {
         ic.biscuit_mut().copy_from_slice(rh.biscuit());
 
         // ICI4
-        core.encrypt_and_mix(ic.auth_mut(), &NOTHING)?;
+        core.encrypt_and_mix(ic.auth_mut(), &[])?;
 
         // Split() – We move the secrets into the session; we do not
         // delete the InitiatorHandshake, just clear it's secrets because
@@ -1625,7 +1884,7 @@ impl CryptoServer {
         )?;
 
         // ICR2
-        core.encrypt_and_mix(&mut [0u8; AEAD_TAG_LEN], &NOTHING)?;
+        core.encrypt_and_mix(&mut [0u8; aead::TAG_LEN], &[])?;
 
         // ICR3
         core.mix(ic.sidi())?.mix(ic.sidr())?;
@@ -1634,7 +1893,7 @@ impl CryptoServer {
         core.decrypt_and_mix(&mut [0u8; 0], ic.auth())?;
 
         // ICR5
-        if sodium_bigint_cmp(&*biscuit_no, &*peer.get(self).biscuit_used) > 0 {
+        if rosenpass_sodium::helpers::compare(&*biscuit_no, &*peer.get(self).biscuit_used) > 0 {
             // ICR6
             peer.get_mut(self).biscuit_used = biscuit_no;
 
@@ -1679,9 +1938,9 @@ impl CryptoServer {
         rc.ctr_mut().copy_from_slice(&ses.txnm.to_le_bytes());
         ses.txnm += 1; // Increment nonce before encryption, just in case an error is raised
 
-        let n = cat!(AEAD_NONCE_LEN; rc.ctr(), &[0u8; 4]);
+        let n = cat!(aead::NONCE_LEN; rc.ctr(), &[0u8; 4]);
         let k = ses.txkm.secret();
-        aead_enc_into(rc.auth_mut(), k, &n, &NOTHING, &NOTHING)?; // ct, k, n, ad, pt
+        aead::encrypt(rc.auth_mut(), k, &n, &[], &[])?; // ct, k, n, ad, pt
 
         Ok(peer)
     }
@@ -1713,12 +1972,12 @@ impl CryptoServer {
             let n = u64::from_le_bytes(rc.ctr().try_into().unwrap());
             ensure!(n >= s.txnt, "Stale nonce");
             s.txnt = n;
-            aead_dec_into(
+            aead::decrypt(
                 // pt, k, n, ad, ct
                 &mut [0u8; 0],
                 s.txkt.secret(),
-                &cat!(AEAD_NONCE_LEN; rc.ctr(), &[0u8; 4]),
-                &NOTHING,
+                &cat!(aead::NONCE_LEN; rc.ctr(), &[0u8; 4]),
+                &[],
                 rc.auth(),
             )?;
         }
@@ -1728,10 +1987,55 @@ impl CryptoServer {
 
         Ok(hs.peer())
     }
+
+    pub fn handle_cookie_reply(&mut self, cr: CookieReply<&[u8]>) -> Result<PeerPtr> {
+        let session_id = SessionId::from_slice(cr.sid());
+
+        let peer_ptr: Option<PeerPtr> = self
+            .lookup_session(session_id)
+            .map(|v| PeerPtr(v.0))
+            .or_else(|| self.lookup_handshake(session_id).map(|v| PeerPtr(v.0)));
+        if let Some(peer) = peer_ptr {
+            if let Some(mac) = peer.get(self).last_sent_mac {
+                let mut cookie_value = [0u8; COOKIE_SECRET_LEN];
+                let spkt = peer.get(self).spkt.secret();
+                let cookie_key = lprf::cookie_key()?.mix(spkt)?.into_value();
+
+                xaead::decrypt(
+                    &mut cookie_value,
+                    &cookie_key,
+                    &mac.value,
+                    &cr.all_bytes()[4..],
+                )?;
+
+                peer.get_mut(self).cookie_tau = CookieSecret::Some {
+                    value: cookie_value,
+                    last_updated: Timebase::default(),
+                };
+
+                Ok(peer)
+            } else {
+                bail!(
+                    "No last sent message for peer {pidr:?} to decrypt cookie reply.",
+                    pidr = cr.sid()
+                );
+            }
+        } else {
+            let sids: Vec<_> = self
+                .peers
+                .iter()
+                .map(|p| p.session.as_ref().map(|s| s.sidm))
+                .collect();
+            println!("SID: {:?}", sids);
+            bail!("No such peer {pidr:?}.", pidr = cr.sid());
+        }
+    }
 }
 
 #[cfg(test)]
 mod test {
+    use std::{net::SocketAddrV4, thread::sleep, time::Duration};
+
     use super::*;
 
     #[test]
@@ -1750,7 +2054,7 @@ mod test {
     /// Through all this, the handshake should still successfully terminate;
     /// i.e. an exchanged key must be produced in both servers.
     fn handles_incorrect_size_messages() {
-        crate::sodium::sodium_init().unwrap();
+        rosenpass_sodium::init().unwrap();
 
         stacker::grow(8 * 1024 * 1024, || {
             const OVERSIZED_MESSAGE: usize = ((MAX_MESSAGE_LEN as f32) * 1.2) as usize;
@@ -1824,4 +2128,129 @@ mod test {
         b.add_peer(Some(psk), pka)?;
         Ok((a, b))
     }
+
+    #[test]
+    fn cookie_reply_mechanism_responder_under_load() {
+        stacker::grow(8 * 1024 * 1024, || {
+            type MsgBufPlus = Public<MAX_MESSAGE_LEN>;
+            let (mut a, mut b) = make_server_pair().unwrap();
+
+            let mut a_to_b_buf = MsgBufPlus::zero();
+            let mut b_to_a_buf = MsgBufPlus::zero();
+
+            let ip_a: SocketAddrV4 = "127.0.0.1:8080".parse().unwrap();
+            let mut ip_addr_port_a = ip_a.ip().octets().to_vec();
+            ip_addr_port_a.extend_from_slice(&ip_a.port().to_be_bytes());
+
+            let _ip_b: SocketAddrV4 = "127.0.0.1:8081".parse().unwrap();
+
+            let init_hello_len = a.initiate_handshake(PeerPtr(0), &mut *a_to_b_buf).unwrap();
+
+            //B handles handshake under load, should send cookie reply message with invalid cookie
+            let HandleMsgResult { resp, .. } = b
+                .handle_msg_under_load(
+                    &a_to_b_buf.as_slice()[..init_hello_len],
+                    &mut *b_to_a_buf,
+                    PeerPtr(0),
+                    SocketAddr::V4(ip_a),
+                )
+                .unwrap();
+
+            let cookie_reply_len = resp.unwrap();
+
+            //A handles cookie reply message
+            a.handle_msg(&b_to_a_buf[..cookie_reply_len], &mut *a_to_b_buf)
+                .unwrap();
+
+            assert!(a.peers[0].cookie_tau.is_some());
+
+            let expected_cookie_tau = lprf::cookie_tau()
+                .unwrap()
+                .mix(b.cookie_secret.get(COOKIE_SECRET_EXP).unwrap())
+                .unwrap()
+                .mix(&ip_addr_port_a)
+                .unwrap()
+                .into_value()[..16]
+                .to_vec();
+            assert_eq!(
+                a.peers[0].cookie_tau.get(PEER_COOKIE_TAU_EXP),
+                Some(&expected_cookie_tau[..])
+            );
+
+            let retx_init_hello_len = loop {
+                match a.poll().unwrap() {
+                    PollResult::SendRetransmission(peer) => {
+                        break (a.retransmit_handshake(peer, &mut *a_to_b_buf).unwrap());
+                    }
+                    PollResult::Sleep(time) => {
+                        sleep(Duration::from_secs_f64(time));
+                    }
+                    _ => {}
+                }
+            };
+
+            let retx_msg_type: MsgType = a_to_b_buf.value[0].try_into().unwrap();
+            assert_eq!(retx_msg_type, MsgType::InitHello);
+
+            //B handles retransmitted message
+            let HandleMsgResult { resp, .. } = b
+                .handle_msg_under_load(
+                    &a_to_b_buf.as_slice()[..retx_init_hello_len],
+                    &mut *b_to_a_buf,
+                    PeerPtr(0),
+                    SocketAddr::V4(ip_a),
+                )
+                .unwrap();
+
+            let _resp_hello_len = resp.unwrap();
+
+            let resp_msg_type: MsgType = b_to_a_buf.value[0].try_into().unwrap();
+            assert_eq!(resp_msg_type, MsgType::RespHello);
+        });
+    }
+
+    #[test]
+    fn cookie_reply_mechanism_initiator_bails_on_message_under_load() {
+        stacker::grow(8 * 1024 * 1024, || {
+            type MsgBufPlus = Public<MAX_MESSAGE_LEN>;
+            let (mut a, mut b) = make_server_pair().unwrap();
+
+            let mut a_to_b_buf = MsgBufPlus::zero();
+            let mut b_to_a_buf = MsgBufPlus::zero();
+
+            let ip_a: SocketAddrV4 = "127.0.0.1:8080".parse().unwrap();
+            let mut ip_addr_port_a = ip_a.ip().octets().to_vec();
+            ip_addr_port_a.extend_from_slice(&ip_a.port().to_be_bytes());
+            let ip_b: SocketAddrV4 = "127.0.0.1:8081".parse().unwrap();
+
+            //A initiates handshake
+            let init_hello_len = a.initiate_handshake(PeerPtr(0), &mut *a_to_b_buf).unwrap();
+
+            //B handles InitHello message, should respond with RespHello
+            let HandleMsgResult { resp, .. } = b
+                .handle_msg(&a_to_b_buf.as_slice()[..init_hello_len], &mut *b_to_a_buf)
+                .unwrap();
+
+            let resp_hello_len = resp.unwrap();
+            let resp_msg_type: MsgType = b_to_a_buf.value[0].try_into().unwrap();
+            assert_eq!(resp_msg_type, MsgType::RespHello);
+
+            let sids: Vec<_> = b
+                .peers
+                .iter()
+                .map(|p| p.session.as_ref().map(|s| s.sidt))
+                .collect();
+            println!("Peer SIDs: {:?}", sids);
+
+            //A handles RespHello message under load, should send cookie reply
+            assert!(a
+                .handle_msg_under_load(
+                    &b_to_a_buf[..resp_hello_len],
+                    &mut *a_to_b_buf,
+                    PeerPtr(0),
+                    SocketAddr::V4(ip_b),
+                )
+                .is_err());
+        });
+    }
 }

rosenpass/src/sodium.rs

@@ -1,285 +0,0 @@
-//! Bindings and helpers for accessing libsodium functions
-
-use crate::util::*;
-use anyhow::{ensure, Result};
-use libsodium_sys as libsodium;
-use log::trace;
-use static_assertions::const_assert_eq;
-use std::os::raw::{c_ulonglong, c_void};
-use std::ptr::{null as nullptr, null_mut as nullptr_mut};
-
-pub const AEAD_TAG_LEN: usize = libsodium::crypto_aead_chacha20poly1305_IETF_ABYTES as usize;
-pub const AEAD_NONCE_LEN: usize = libsodium::crypto_aead_chacha20poly1305_IETF_NPUBBYTES as usize;
-pub const XAEAD_TAG_LEN: usize = libsodium::crypto_aead_xchacha20poly1305_ietf_ABYTES as usize;
-pub const XAEAD_NONCE_LEN: usize = libsodium::crypto_aead_xchacha20poly1305_IETF_NPUBBYTES as usize;
-pub const NONCE0: [u8; libsodium::crypto_aead_chacha20poly1305_IETF_NPUBBYTES as usize] =
-    [0u8; libsodium::crypto_aead_chacha20poly1305_IETF_NPUBBYTES as usize];
-pub const NOTHING: [u8; 0] = [0u8; 0];
-pub const KEY_SIZE: usize = 32;
-pub const MAC_SIZE: usize = 16;
-
-const_assert_eq!(
-    KEY_SIZE,
-    libsodium::crypto_aead_chacha20poly1305_IETF_KEYBYTES as usize
-);
-const_assert_eq!(KEY_SIZE, libsodium::crypto_generichash_BYTES as usize);
-
-macro_rules! sodium_call {
-    ($name:ident, $($args:expr),*) => { attempt!({
-        ensure!(unsafe{libsodium::$name($($args),*)} > -1,
-            "Error in libsodium's {}.", stringify!($name));
-        Ok(())
-    })};
-    ($name:ident) => { sodium_call!($name, ) };
-}
-
-#[inline]
-pub fn sodium_init() -> Result<()> {
-    trace!("initializing libsodium");
-    sodium_call!(sodium_init)
-}
-
-#[inline]
-pub fn sodium_memcmp(a: &[u8], b: &[u8]) -> bool {
-    a.len() == b.len()
-        && unsafe {
-            let r = libsodium::sodium_memcmp(
-                a.as_ptr() as *const c_void,
-                b.as_ptr() as *const c_void,
-                a.len(),
-            );
-            r == 0
-        }
-}
-
-#[inline]
-pub fn sodium_bigint_cmp(a: &[u8], b: &[u8]) -> i32 {
-    assert!(a.len() == b.len());
-    unsafe { libsodium::sodium_compare(a.as_ptr(), b.as_ptr(), a.len()) }
-}
-
-#[inline]
-pub fn sodium_bigint_inc(v: &mut [u8]) {
-    unsafe {
-        libsodium::sodium_increment(v.as_mut_ptr(), v.len());
-    }
-}
-
-#[inline]
-pub fn rng(buf: &mut [u8]) {
-    unsafe { libsodium::randombytes_buf(buf.as_mut_ptr() as *mut c_void, buf.len()) };
-}
-
-#[inline]
-pub fn zeroize(buf: &mut [u8]) {
-    unsafe { libsodium::sodium_memzero(buf.as_mut_ptr() as *mut c_void, buf.len()) };
-}
-
-#[inline]
-pub fn aead_enc_into(
-    ciphertext: &mut [u8],
-    key: &[u8],
-    nonce: &[u8],
-    ad: &[u8],
-    plaintext: &[u8],
-) -> Result<()> {
-    assert!(ciphertext.len() == plaintext.len() + AEAD_TAG_LEN);
-    assert!(key.len() == libsodium::crypto_aead_chacha20poly1305_IETF_KEYBYTES as usize);
-    assert!(nonce.len() == libsodium::crypto_aead_chacha20poly1305_IETF_NPUBBYTES as usize);
-    let mut clen: u64 = 0;
-    sodium_call!(
-        crypto_aead_chacha20poly1305_ietf_encrypt,
-        ciphertext.as_mut_ptr(),
-        &mut clen,
-        plaintext.as_ptr(),
-        plaintext.len() as c_ulonglong,
-        ad.as_ptr(),
-        ad.len() as c_ulonglong,
-        nullptr(), // nsec is not used
-        nonce.as_ptr(),
-        key.as_ptr()
-    )?;
-    assert!(clen as usize == ciphertext.len());
-    Ok(())
-}
-
-#[inline]
-pub fn aead_dec_into(
-    plaintext: &mut [u8],
-    key: &[u8],
-    nonce: &[u8],
-    ad: &[u8],
-    ciphertext: &[u8],
-) -> Result<()> {
-    assert!(ciphertext.len() == plaintext.len() + AEAD_TAG_LEN);
-    assert!(key.len() == libsodium::crypto_aead_chacha20poly1305_IETF_KEYBYTES as usize);
-    assert!(nonce.len() == libsodium::crypto_aead_chacha20poly1305_IETF_NPUBBYTES as usize);
-    let mut mlen: u64 = 0;
-    sodium_call!(
-        crypto_aead_chacha20poly1305_ietf_decrypt,
-        plaintext.as_mut_ptr(),
-        &mut mlen as *mut c_ulonglong,
-        nullptr_mut(), // nsec is not used
-        ciphertext.as_ptr(),
-        ciphertext.len() as c_ulonglong,
-        ad.as_ptr(),
-        ad.len() as c_ulonglong,
-        nonce.as_ptr(),
-        key.as_ptr()
-    )?;
-    assert!(mlen as usize == plaintext.len());
-    Ok(())
-}
-
-#[inline]
-pub fn xaead_enc_into(
-    ciphertext: &mut [u8],
-    key: &[u8],
-    nonce: &[u8],
-    ad: &[u8],
-    plaintext: &[u8],
-) -> Result<()> {
-    assert!(ciphertext.len() == plaintext.len() + XAEAD_NONCE_LEN + XAEAD_TAG_LEN);
-    assert!(key.len() == libsodium::crypto_aead_xchacha20poly1305_IETF_KEYBYTES as usize);
-    let (n, ct) = ciphertext.split_at_mut(XAEAD_NONCE_LEN);
-    n.copy_from_slice(nonce);
-    let mut clen: u64 = 0;
-    sodium_call!(
-        crypto_aead_xchacha20poly1305_ietf_encrypt,
-        ct.as_mut_ptr(),
-        &mut clen,
-        plaintext.as_ptr(),
-        plaintext.len() as c_ulonglong,
-        ad.as_ptr(),
-        ad.len() as c_ulonglong,
-        nullptr(), // nsec is not used
-        nonce.as_ptr(),
-        key.as_ptr()
-    )?;
-    assert!(clen as usize == ct.len());
-    Ok(())
-}
-
-#[inline]
-pub fn xaead_dec_into(
-    plaintext: &mut [u8],
-    key: &[u8],
-    ad: &[u8],
-    ciphertext: &[u8],
-) -> Result<()> {
-    assert!(ciphertext.len() == plaintext.len() + XAEAD_NONCE_LEN + XAEAD_TAG_LEN);
-    assert!(key.len() == libsodium::crypto_aead_xchacha20poly1305_IETF_KEYBYTES as usize);
-    let (n, ct) = ciphertext.split_at(XAEAD_NONCE_LEN);
-    let mut mlen: u64 = 0;
-    sodium_call!(
-        crypto_aead_xchacha20poly1305_ietf_decrypt,
-        plaintext.as_mut_ptr(),
-        &mut mlen as *mut c_ulonglong,
-        nullptr_mut(), // nsec is not used
-        ct.as_ptr(),
-        ct.len() as c_ulonglong,
-        ad.as_ptr(),
-        ad.len() as c_ulonglong,
-        n.as_ptr(),
-        key.as_ptr()
-    )?;
-    assert!(mlen as usize == plaintext.len());
-    Ok(())
-}
-
-#[inline]
-fn blake2b_flexible(out: &mut [u8], key: &[u8], data: &[u8]) -> Result<()> {
-    const KEY_MIN: usize = libsodium::crypto_generichash_KEYBYTES_MIN as usize;
-    const KEY_MAX: usize = libsodium::crypto_generichash_KEYBYTES_MAX as usize;
-    const OUT_MIN: usize = libsodium::crypto_generichash_BYTES_MIN as usize;
-    const OUT_MAX: usize = libsodium::crypto_generichash_BYTES_MAX as usize;
-    assert!(key.is_empty() || (KEY_MIN <= key.len() && key.len() <= KEY_MAX));
-    assert!(OUT_MIN <= out.len() && out.len() <= OUT_MAX);
-    let kptr = match key.len() {
-        // NULL key
-        0 => nullptr(),
-        _ => key.as_ptr(),
-    };
-    sodium_call!(
-        crypto_generichash_blake2b,
-        out.as_mut_ptr(),
-        out.len(),
-        data.as_ptr(),
-        data.len() as c_ulonglong,
-        kptr,
-        key.len()
-    )
-}
-
-// TODO: Use proper streaming hash; for mix_hash too.
-#[inline]
-pub fn hash_into(out: &mut [u8], data: &[u8]) -> Result<()> {
-    assert!(out.len() == KEY_SIZE);
-    blake2b_flexible(out, &NOTHING, data)
-}
-
-#[inline]
-pub fn hash(data: &[u8]) -> Result<[u8; KEY_SIZE]> {
-    let mut r = [0u8; KEY_SIZE];
-    hash_into(&mut r, data)?;
-    Ok(r)
-}
-
-#[inline]
-pub fn mac_into(out: &mut [u8], key: &[u8], data: &[u8]) -> Result<()> {
-    assert!(out.len() == KEY_SIZE);
-    assert!(key.len() == KEY_SIZE);
-    blake2b_flexible(out, key, data)
-}
-
-#[inline]
-pub fn mac(key: &[u8], data: &[u8]) -> Result<[u8; KEY_SIZE]> {
-    let mut r = [0u8; KEY_SIZE];
-    mac_into(&mut r, key, data)?;
-    Ok(r)
-}
-
-#[inline]
-pub fn mac16(key: &[u8], data: &[u8]) -> Result<[u8; 16]> {
-    assert!(key.len() == KEY_SIZE);
-    let mut out = [0u8; 16];
-    blake2b_flexible(&mut out, key, data)?;
-    Ok(out)
-}
-
-#[inline]
-pub fn hmac_into(out: &mut [u8], key: &[u8], data: &[u8]) -> Result<()> {
-    // Not bothering with padding; the implementation
-    // uses appropriately sized keys.
-    ensure!(key.len() == KEY_SIZE);
-
-    const IPAD: [u8; KEY_SIZE] = [0x36u8; KEY_SIZE];
-    let mut temp_key = [0u8; KEY_SIZE];
-    temp_key.copy_from_slice(key);
-    xor_into(&mut temp_key, &IPAD);
-    let outer_data = mac(&temp_key, data)?;
-
-    const OPAD: [u8; KEY_SIZE] = [0x5Cu8; KEY_SIZE];
-    temp_key.copy_from_slice(key);
-    xor_into(&mut temp_key, &OPAD);
-    mac_into(out, &temp_key, &outer_data)
-}
-
-#[inline]
-pub fn hmac(key: &[u8], data: &[u8]) -> Result<[u8; KEY_SIZE]> {
-    let mut r = [0u8; KEY_SIZE];
-    hmac_into(&mut r, key, data)?;
-    Ok(r)
-}
-
-// Choose a fully random u64
-pub fn rand_u64() -> u64 {
-    let mut buf = [0u8; 8];
-    rng(&mut buf);
-    u64::from_le_bytes(buf)
-}
-
-// Choose a random f64 in [0; 1] inclusive; quick and dirty
-pub fn rand_f64() -> f64 {
-    (rand_u64() as f64) / (u64::MAX as f64)
-}

rosenpass/src/util.rs

@@ -1,244 +0,0 @@
-//! Helper functions and macros
-use anyhow::{ensure, Context, Result};
-use base64::{
-    display::Base64Display as B64Display, read::DecoderReader as B64Reader,
-    write::EncoderWriter as B64Writer,
-};
-use std::{
-    borrow::{Borrow, BorrowMut},
-    cmp::min,
-    fs::{File, OpenOptions},
-    io::{Read, Write},
-    path::Path,
-    time::{Duration, Instant},
-};
-
-use crate::coloring::{Public, Secret};
-
-/// Xors a and b element-wise and writes the result into a.
-///
-/// # Examples
-///
-/// ```
-/// use rosenpass::util::xor_into;
-/// let mut a = String::from("hello").into_bytes();
-/// let b = b"world";
-/// xor_into(&mut a, b);
-/// assert_eq!(&a, b"\x1f\n\x1e\x00\x0b");
-/// ```
-#[inline]
-pub fn xor_into(a: &mut [u8], b: &[u8]) {
-    assert!(a.len() == b.len());
-    for (av, bv) in a.iter_mut().zip(b.iter()) {
-        *av ^= *bv;
-    }
-}
-
-/// Concatenate two byte arrays
-// TODO: Zeroize result?
-#[macro_export]
-macro_rules! cat {
-    ($len:expr; $($toks:expr),+) => {{
-        let mut buf = [0u8; $len];
-        let mut off = 0;
-        $({
-            let tok = $toks;
-            let tr = ::std::borrow::Borrow::<[u8]>::borrow(tok);
-            (&mut buf[off..(off + tr.len())]).copy_from_slice(tr);
-            off += tr.len();
-        })+
-        assert!(off == buf.len(), "Size mismatch in cat!()");
-        buf
-    }}
-}
-
-// TODO: consistent inout ordering
-pub fn cpy<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, dst: &mut T) {
-    dst.borrow_mut().copy_from_slice(src.borrow());
-}
-
-/// Copy from `src` to `dst`. If `src` and `dst` are not of equal length, copy as many bytes as possible.
-pub fn cpy_min<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, dst: &mut T) {
-    let src = src.borrow();
-    let dst = dst.borrow_mut();
-    let len = min(src.len(), dst.len());
-    dst[..len].copy_from_slice(&src[..len]);
-}
-
-/// Try block basically…returns a result and allows the use of the question mark operator inside
-#[macro_export]
-macro_rules! attempt {
-    ($block:expr) => {
-        (|| -> ::anyhow::Result<_> { $block })()
-    };
-}
-
-use base64::engine::general_purpose::GeneralPurpose as Base64Engine;
-const B64ENGINE: Base64Engine = base64::engine::general_purpose::STANDARD;
-
-pub fn fmt_b64<'a>(payload: &'a [u8]) -> B64Display<'a, 'static, Base64Engine> {
-    B64Display::<'a, 'static>::new(payload, &B64ENGINE)
-}
-
-pub fn b64_writer<W: Write>(w: W) -> B64Writer<'static, Base64Engine, W> {
-    B64Writer::new(w, &B64ENGINE)
-}
-
-pub fn b64_reader<R: Read>(r: R) -> B64Reader<'static, Base64Engine, R> {
-    B64Reader::new(r, &B64ENGINE)
-}
-
-// TODO remove this once std::cmp::max becomes const
-pub const fn max_usize(a: usize, b: usize) -> usize {
-    if a > b {
-        a
-    } else {
-        b
-    }
-}
-
-#[derive(Clone, Debug)]
-pub struct Timebase(Instant);
-
-impl Default for Timebase {
-    fn default() -> Self {
-        Self(Instant::now())
-    }
-}
-
-impl Timebase {
-    pub fn now(&self) -> f64 {
-        self.0.elapsed().as_secs_f64()
-    }
-
-    pub fn dur(&self, t: f64) -> Duration {
-        Duration::from_secs_f64(t)
-    }
-}
-
-pub fn mutating<T, F>(mut v: T, f: F) -> T
-where
-    F: Fn(&mut T),
-{
-    f(&mut v);
-    v
-}
-
-pub fn sideeffect<T, F>(v: T, f: F) -> T
-where
-    F: Fn(&T),
-{
-    f(&v);
-    v
-}
-
-/// load'n store
-
-/// Open a file writable
-pub fn fopen_w<P: AsRef<Path>>(path: P) -> Result<File> {
-    Ok(OpenOptions::new()
-        .read(false)
-        .write(true)
-        .create(true)
-        .truncate(true)
-        .open(path)?)
-}
-/// Open a file readable
-pub fn fopen_r<P: AsRef<Path>>(path: P) -> Result<File> {
-    Ok(OpenOptions::new()
-        .read(true)
-        .write(false)
-        .create(false)
-        .truncate(false)
-        .open(path)?)
-}
-
-pub trait ReadExactToEnd {
-    fn read_exact_to_end(&mut self, buf: &mut [u8]) -> Result<()>;
-}
-
-impl<R: Read> ReadExactToEnd for R {
-    fn read_exact_to_end(&mut self, buf: &mut [u8]) -> Result<()> {
-        let mut dummy = [0u8; 8];
-        self.read_exact(buf)?;
-        ensure!(self.read(&mut dummy)? == 0, "File too long!");
-        Ok(())
-    }
-}
-
-pub trait LoadValue {
-    fn load<P: AsRef<Path>>(path: P) -> Result<Self>
-    where
-        Self: Sized;
-}
-
-pub trait LoadValueB64 {
-    fn load_b64<P: AsRef<Path>>(path: P) -> Result<Self>
-    where
-        Self: Sized;
-}
-
-trait StoreValue {
-    fn store<P: AsRef<Path>>(&self, path: P) -> Result<()>;
-}
-
-trait StoreSecret {
-    fn store_secret<P: AsRef<Path>>(&self, path: P) -> Result<()>;
-}
-
-impl<T: StoreValue> StoreSecret for T {
-    fn store_secret<P: AsRef<Path>>(&self, path: P) -> Result<()> {
-        self.store(path)
-    }
-}
-
-impl<const N: usize> LoadValue for Secret<N> {
-    fn load<P: AsRef<Path>>(path: P) -> Result<Self> {
-        let mut v = Self::random();
-        let p = path.as_ref();
-        fopen_r(p)?
-            .read_exact_to_end(v.secret_mut())
-            .with_context(|| format!("Could not load file {p:?}"))?;
-        Ok(v)
-    }
-}
-
-impl<const N: usize> LoadValueB64 for Secret<N> {
-    fn load_b64<P: AsRef<Path>>(path: P) -> Result<Self> {
-        let mut v = Self::random();
-        let p = path.as_ref();
-        // This might leave some fragments of the secret on the stack;
-        // in practice this is likely not a problem because the stack likely
-        // will be overwritten by something else soon but this is not exactly
-        // guaranteed. It would be possible to remedy this, but since the secret
-        // data will linger in the Linux page cache anyways with the current
-        // implementation, going to great length to erase the secret here is
-        // not worth it right now.
-        b64_reader(&mut fopen_r(p)?)
-            .read_exact(v.secret_mut())
-            .with_context(|| format!("Could not load base64 file {p:?}"))?;
-        Ok(v)
-    }
-}
-
-impl<const N: usize> StoreSecret for Secret<N> {
-    fn store_secret<P: AsRef<Path>>(&self, path: P) -> Result<()> {
-        std::fs::write(path, self.secret())?;
-        Ok(())
-    }
-}
-
-impl<const N: usize> LoadValue for Public<N> {
-    fn load<P: AsRef<Path>>(path: P) -> Result<Self> {
-        let mut v = Self::random();
-        fopen_r(path)?.read_exact_to_end(&mut *v)?;
-        Ok(v)
-    }
-}
-
-impl<const N: usize> StoreValue for Public<N> {
-    fn store<P: AsRef<Path>>(&self, path: P) -> Result<()> {
-        std::fs::write(path, **self)?;
-        Ok(())
-    }
-}

sodium/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "rosenpass-sodium"
+authors = ["Karolin Varner <karo@cupdev.net>", "wucke13 <wucke13@gmail.com>"]
+version = "0.1.0"
+edition = "2021"
+license = "MIT OR Apache-2.0"
+description = "Rosenpass internal bindings to libsodium"
+homepage = "https://rosenpass.eu/"
+repository = "https://github.com/rosenpass/rosenpass"
+readme = "readme.md"
+
+[dependencies]
+rosenpass-util = { workspace = true }
+rosenpass-to = { workspace = true }
+anyhow = { workspace = true }
+libsodium-sys-stable = { workspace = true }
+log = { workspace = true }

sodium/readme.md

@@ -0,0 +1,5 @@
+# Rosenpass internal libsodium bindings
+
+Rosenpass internal library providing bindings to libsodium.
+
+This is an internal library; not guarantee is made about its API at this point in time.

sodium/src/aead/chacha20poly1305_ietf.rs

@@ -0,0 +1,63 @@
+use libsodium_sys as libsodium;
+use std::ffi::c_ulonglong;
+use std::ptr::{null, null_mut};
+
+pub const KEY_LEN: usize = libsodium::crypto_aead_chacha20poly1305_IETF_KEYBYTES as usize;
+pub const TAG_LEN: usize = libsodium::crypto_aead_chacha20poly1305_IETF_ABYTES as usize;
+pub const NONCE_LEN: usize = libsodium::crypto_aead_chacha20poly1305_IETF_NPUBBYTES as usize;
+
+#[inline]
+pub fn encrypt(
+    ciphertext: &mut [u8],
+    key: &[u8],
+    nonce: &[u8],
+    ad: &[u8],
+    plaintext: &[u8],
+) -> anyhow::Result<()> {
+    assert!(ciphertext.len() == plaintext.len() + TAG_LEN);
+    assert!(key.len() == KEY_LEN);
+    assert!(nonce.len() == NONCE_LEN);
+    let mut clen: u64 = 0;
+    sodium_call!(
+        crypto_aead_chacha20poly1305_ietf_encrypt,
+        ciphertext.as_mut_ptr(),
+        &mut clen,
+        plaintext.as_ptr(),
+        plaintext.len() as c_ulonglong,
+        ad.as_ptr(),
+        ad.len() as c_ulonglong,
+        null(), // nsec is not used
+        nonce.as_ptr(),
+        key.as_ptr()
+    )?;
+    assert!(clen as usize == ciphertext.len());
+    Ok(())
+}
+
+#[inline]
+pub fn decrypt(
+    plaintext: &mut [u8],
+    key: &[u8],
+    nonce: &[u8],
+    ad: &[u8],
+    ciphertext: &[u8],
+) -> anyhow::Result<()> {
+    assert!(ciphertext.len() == plaintext.len() + TAG_LEN);
+    assert!(key.len() == KEY_LEN);
+    assert!(nonce.len() == NONCE_LEN);
+    let mut mlen: u64 = 0;
+    sodium_call!(
+        crypto_aead_chacha20poly1305_ietf_decrypt,
+        plaintext.as_mut_ptr(),
+        &mut mlen as *mut c_ulonglong,
+        null_mut(), // nsec is not used
+        ciphertext.as_ptr(),
+        ciphertext.len() as c_ulonglong,
+        ad.as_ptr(),
+        ad.len() as c_ulonglong,
+        nonce.as_ptr(),
+        key.as_ptr()
+    )?;
+    assert!(mlen as usize == plaintext.len());
+    Ok(())
+}

sodium/src/aead/mod.rs

@@ -0,0 +1,2 @@
+pub mod chacha20poly1305_ietf;
+pub mod xchacha20poly1305_ietf;

sodium/src/aead/xchacha20poly1305_ietf.rs

@@ -0,0 +1,63 @@
+use libsodium_sys as libsodium;
+use std::ffi::c_ulonglong;
+use std::ptr::{null, null_mut};
+
+pub const KEY_LEN: usize = libsodium::crypto_aead_xchacha20poly1305_IETF_KEYBYTES as usize;
+pub const TAG_LEN: usize = libsodium::crypto_aead_xchacha20poly1305_ietf_ABYTES as usize;
+pub const NONCE_LEN: usize = libsodium::crypto_aead_xchacha20poly1305_IETF_NPUBBYTES as usize;
+
+#[inline]
+pub fn encrypt(
+    ciphertext: &mut [u8],
+    key: &[u8],
+    nonce: &[u8],
+    ad: &[u8],
+    plaintext: &[u8],
+) -> anyhow::Result<()> {
+    assert!(ciphertext.len() == plaintext.len() + NONCE_LEN + TAG_LEN);
+    assert!(key.len() == libsodium::crypto_aead_xchacha20poly1305_IETF_KEYBYTES as usize);
+    let (n, ct) = ciphertext.split_at_mut(NONCE_LEN);
+    n.copy_from_slice(nonce);
+    let mut clen: u64 = 0;
+    sodium_call!(
+        crypto_aead_xchacha20poly1305_ietf_encrypt,
+        ct.as_mut_ptr(),
+        &mut clen,
+        plaintext.as_ptr(),
+        plaintext.len() as c_ulonglong,
+        ad.as_ptr(),
+        ad.len() as c_ulonglong,
+        null(), // nsec is not used
+        nonce.as_ptr(),
+        key.as_ptr()
+    )?;
+    assert!(clen as usize == ct.len());
+    Ok(())
+}
+
+#[inline]
+pub fn decrypt(
+    plaintext: &mut [u8],
+    key: &[u8],
+    ad: &[u8],
+    ciphertext: &[u8],
+) -> anyhow::Result<()> {
+    assert!(ciphertext.len() == plaintext.len() + NONCE_LEN + TAG_LEN);
+    assert!(key.len() == KEY_LEN);
+    let (n, ct) = ciphertext.split_at(NONCE_LEN);
+    let mut mlen: u64 = 0;
+    sodium_call!(
+        crypto_aead_xchacha20poly1305_ietf_decrypt,
+        plaintext.as_mut_ptr(),
+        &mut mlen as *mut c_ulonglong,
+        null_mut(), // nsec is not used
+        ct.as_ptr(),
+        ct.len() as c_ulonglong,
+        ad.as_ptr(),
+        ad.len() as c_ulonglong,
+        n.as_ptr(),
+        key.as_ptr()
+    )?;
+    assert!(mlen as usize == plaintext.len());
+    Ok(())
+}

sodium/src/hash/blake2b.rs

@@ -0,0 +1,31 @@
+use libsodium_sys as libsodium;
+use rosenpass_to::{with_destination, To};
+use std::ffi::c_ulonglong;
+use std::ptr::null;
+
+pub const KEY_MIN: usize = libsodium::crypto_generichash_blake2b_KEYBYTES_MIN as usize;
+pub const KEY_MAX: usize = libsodium::crypto_generichash_blake2b_KEYBYTES_MAX as usize;
+pub const OUT_MIN: usize = libsodium::crypto_generichash_blake2b_BYTES_MIN as usize;
+pub const OUT_MAX: usize = libsodium::crypto_generichash_blake2b_BYTES_MAX as usize;
+
+#[inline]
+pub fn hash<'a>(key: &'a [u8], data: &'a [u8]) -> impl To<[u8], anyhow::Result<()>> + 'a {
+    with_destination(|out: &mut [u8]| {
+        assert!(key.is_empty() || (KEY_MIN <= key.len() && key.len() <= KEY_MAX));
+        assert!(OUT_MIN <= out.len() && out.len() <= OUT_MAX);
+        let kptr = match key.len() {
+            // NULL key
+            0 => null(),
+            _ => key.as_ptr(),
+        };
+        sodium_call!(
+            crypto_generichash_blake2b,
+            out.as_mut_ptr(),
+            out.len(),
+            data.as_ptr(),
+            data.len() as c_ulonglong,
+            kptr,
+            key.len()
+        )
+    })
+}

sodium/src/hash/mod.rs

@@ -0,0 +1 @@
+pub mod blake2b;

sodium/src/helpers.rs

@@ -0,0 +1,52 @@
+use libsodium_sys as libsodium;
+use std::os::raw::c_void;
+
+#[inline]
+pub fn memcmp(a: &[u8], b: &[u8]) -> bool {
+    a.len() == b.len()
+        && unsafe {
+            let r = libsodium::sodium_memcmp(
+                a.as_ptr() as *const c_void,
+                b.as_ptr() as *const c_void,
+                a.len(),
+            );
+            r == 0
+        }
+}
+
+#[inline]
+pub fn compare(a: &[u8], b: &[u8]) -> i32 {
+    assert!(a.len() == b.len());
+    unsafe { libsodium::sodium_compare(a.as_ptr(), b.as_ptr(), a.len()) }
+}
+
+#[inline]
+pub fn increment(v: &mut [u8]) {
+    unsafe {
+        libsodium::sodium_increment(v.as_mut_ptr(), v.len());
+    }
+}
+
+#[inline]
+pub fn randombytes_buf(buf: &mut [u8]) {
+    unsafe { libsodium::randombytes_buf(buf.as_mut_ptr() as *mut c_void, buf.len()) };
+}
+
+#[inline]
+pub fn memzero(buf: &mut [u8]) {
+    unsafe { libsodium::sodium_memzero(buf.as_mut_ptr() as *mut c_void, buf.len()) };
+}
+
+// Choose a fully random u64
+// TODO: Replace with ::rand::random
+pub fn rand_u64() -> u64 {
+    let mut buf = [0u8; 8];
+    randombytes_buf(&mut buf);
+    u64::from_le_bytes(buf)
+}
+
+// Choose a random f64 in [0; 1] inclusive; quick and dirty
+// TODO: Replace with ::rand::random
+pub fn rand_f64() -> f64 {
+    (rand_u64() as f64) / (u64::MAX as f64)
+}

sodium/src/lib.rs

@@ -0,0 +1,20 @@
+use libsodium_sys as libsodium;
+
+macro_rules! sodium_call {
+    ($name:ident, $($args:expr),*) => { ::rosenpass_util::attempt!({
+        anyhow::ensure!(unsafe{libsodium::$name($($args),*)} > -1,
+            "Error in libsodium's {}.", stringify!($name));
+        Ok(())
+    })};
+    ($name:ident) => { sodium_call!($name, ) };
+}
+
+#[inline]
+pub fn init() -> anyhow::Result<()> {
+    log::trace!("initializing libsodium");
+    sodium_call!(sodium_init)
+}
+
+pub mod aead;
+pub mod hash;
+pub mod helpers;

to/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "rosenpass-to"
+version = "0.1.0"
+authors = ["Karolin Varner <karo@cupdev.net>", "wucke13 <wucke13@gmail.com>"]
+edition = "2021"
+license = "MIT OR Apache-2.0"
+description = "Flexible destination parameters"
+homepage = "https://rosenpass.eu/"
+repository = "https://github.com/rosenpass/rosenpass"
+readme = "readme.md"
+
+[dev-dependencies]
+doc-comment = { workspace = true }

to/README.md

@@ -0,0 +1,477 @@
+# The To Crate – Patterns for dealing with destination parameters in rust functions
+
+<!-- The code blocks in this file double as tests. -->
+
+![crates.io](https://img.shields.io/crates/v/rosenpass-to.svg)
+![Libraries.io dependency status for latest release](https://img.shields.io/librariesio/release/cargo/rosenpass-to)
+
+The To Crate provides a pattern for declaring and dealing with destination parameters in rust functions. It improves over stock rust by providing an interface that allows the caller to choose whether to place the destination parameter first – through a `to(dest, copy(source))` function – or last – through a chained function `copy(source).to(dest)`.
+
+The crate provides chained functions to simplify allocating the destination parameter on the fly and it provides well defined patterns for dealing with error handling and destination parameters.
+
+For now this crate is experimental; patch releases are guaranteed not to contain any breaking changes, but minor releases may.
+
+```rust
+use std::ops::BitXorAssign;
+use rosenpass_to::{To, to, with_destination};
+use rosenpass_to::ops::copy_array;
+
+// Destination functions return some value that implements the To trait.
+// Unfortunately dealing with lifetimes is a bit more finicky than it would#
+// be without destination parameters
+fn xor_slice<'a, T>(src: &'a[T]) -> impl To<[T], ()> + 'a
+        where T: BitXorAssign + Clone {
+    // Custom implementations of the to trait can be created, but the easiest
+    with_destination(move |dst: &mut [T]| {
+        assert!(src.len() == dst.len());
+        for (d, s) in dst.iter_mut().zip(src.iter()) {
+            *d ^= s.clone();
+        }
+    })
+}
+
+let flip0 = b"\xff\x00\x00\x00";
+let flip1 = b"\x00\xff\x00\x00";
+let flip01 = b"\xff\xff\x00\x00";
+
+// You can specify a destination by using the to method
+let mut dst = [0u8; 4];
+xor_slice(flip0).to(&mut dst);
+xor_slice(flip1).to(&mut dst);
+assert_eq!(&dst[..], &flip01[..]);
+
+// Or using the to function
+let mut dst = [0u8; 4];
+to(&mut dst, xor_slice(flip0));
+to(&mut dst, xor_slice(flip1));
+assert_eq!(&dst[..], &flip01[..]);
+
+// You can pass a function to generate the destination on the fly
+let dst = xor_slice(flip1).to_this(|| flip0.to_vec());
+assert_eq!(&dst[..], &flip01[..]);
+
+// If xor_slice used a return value that could be created using Default::default(),
+// you could just use `xor_slice(flip01).to_value()` to generate the destination
+// on the fly. Since [u8] is unsized, it can only be used for references.
+//
+// You can however use collect to specify the storage value explicitly.
+// This works for any type that implements Default::default() and BorrowMut<...> for
+// the destination value.
+
+// Collect in an array with a fixed size
+let dst = xor_slice(flip01).collect::<[u8; 4]>();
+assert_eq!(&dst[..], &flip01[..]);
+
+// The builtin function copy_array supports to_value() since its
+// destination parameter is a fixed size array, which can be allocated
+// using default()
+let dst : [u8; 4] = copy_array(flip01).to_value();
+assert_eq!(&dst, flip01);
+```
+
+The to crate really starts to shine when error handling (through result) is combined with destination parameters. See the tutorial below for details.
+
+## Motivation
+
+Destination parameters are often used when simply returning the value is undesirable or impossible.
+
+Using stock rust features, functions can declare destination parameters by accepting mutable references as arguments.
+This pattern introduces some shortcomings; developers have to make a call on whether to place destination parameters before or after source parameters and they have to enforce consistency across their codebase or accept inconsistencies, leading to hard-to-remember interfaces.
+
+Functions declared like this are more cumbersome to use when the destination parameter should be allocated on the fly.
+
+```rust
+use std::ops::BitXorAssign;
+
+fn xor_slice<T>(dst: &mut [T], src: &[T])
+        where T: BitXorAssign + Clone {
+    assert!(src.len() == dst.len());
+    for (d, s) in dst.iter_mut().zip(src.iter()) {
+        *d ^= s.clone();
+    }
+}
+
+let flip0 = b"\xff\x00\x00\x00";
+let flip1 = b"\x00\xff\x00\x00";
+let flip01 = b"\xff\xff\x00\x00";
+
+// Copy a slice from src to dest; its unclear whether src or dest should come first
+let mut dst = [0u8; 4];
+xor_slice(&mut dst, flip0);
+xor_slice(&mut dst, flip1);
+assert_eq!(&dst[..], &flip01[..]);
+
+// The other examples can not be translated to use the standard rust pattern,
+// since using mutable references for destination parameters does not allow
+// for specifying the destination parameter on the right side or allocating
+// the destination parameter on the fly.
+```
+
+## Tutorial
+
+### Using a function with destination
+
+There are a couple of ways to use a function with destination:
+
+```rust
+use rosenpass_to::{to, To};
+use rosenpass_to::ops::{copy_array, copy_slice_least};
+
+let mut dst = b"           ".to_vec();
+
+// Using the to function to have data flowing from the right to the left,
+// performing something akin to a variable assignment
+to(&mut dst[..], copy_slice_least(b"Hello World"));
+assert_eq!(&dst[..], b"Hello World");
+
+// Using the to method to have information flowing from the left to the right
+copy_slice_least(b"This is fin").to(&mut dst[..]);
+assert_eq!(&dst[..], b"This is fin");
+
+// You can allocate the destination variable on the fly using `.to_this(...)`
+let tmp = copy_slice_least(b"This is new---").to_this(|| b"This will be overwritten".to_owned());
+assert_eq!(&tmp[..], b"This is new---verwritten");
+
+// You can allocate the destination variable on the fly `.collect(..)` if it implements default
+let tmp = copy_slice_least(b"This is ad-hoc").collect::<[u8; 16]>();
+assert_eq!(&tmp[..], b"This is ad-hoc\0\0");
+
+// Finally, if the destination variable specified by the function implements default,
+// you can simply use `.to_value()` to allocate it on the fly.
+let tmp = copy_array(b"Fixed").to_value();
+assert_eq!(&tmp[..], b"Fixed");
+```
+
+### Builtin functions with destination
+
+The to crate provides basic functions with destination for copying data between slices and arrays.
+
+```rust
+use rosenpass_to::{to, To};
+use rosenpass_to::ops::{copy_array, copy_slice, copy_slice_least, copy_slice_least_src, try_copy_slice, try_copy_slice_least_src};
+
+let mut dst = b"           ".to_vec();
+
+// Copy a slice, source and destination must match exactly
+to(&mut dst[..], copy_slice(b"Hello World"));
+assert_eq!(&dst[..], b"Hello World");
+
+// Copy a slice, destination must be at least as long as the destination
+to(&mut dst[4..], copy_slice_least_src(b"!!!"));
+assert_eq!(&dst[..], b"Hell!!!orld");
+
+// Copy a slice, copying as many bytes as possible
+to(&mut dst[6..], copy_slice_least(b"xxxxxxxxxxxxxxxxxxxxxxxxxxxxx"));
+assert_eq!(&dst[..], b"Hell!!xxxxx");
+
+// Copy a slice, will return None and abort if the sizes do not much
+assert_eq!(Some(()), to(&mut dst[..], try_copy_slice(b"Hello World")));
+assert_eq!(None, to(&mut dst[..], try_copy_slice(b"---")));
+assert_eq!(None, to(&mut dst[..], try_copy_slice(b"---------------------")));
+assert_eq!(&dst[..], b"Hello World");
+
+// Copy a slice, will return None and abort if source is longer than destination
+assert_eq!(Some(()), to(&mut dst[4..], try_copy_slice_least_src(b"!!!")));
+assert_eq!(None, to(&mut dst[4..], try_copy_slice_least_src(b"-------------------------")));
+assert_eq!(&dst[..], b"Hell!!!orld");
+
+// Copy fixed size arrays all at once
+let mut dst = [0u8; 5];
+to(&mut dst, copy_array(b"Hello"));
+assert_eq!(&dst, b"Hello");
+```
+
+### Declaring a function with destination
+
+The easiest way to declare a function with destination is to use the with_destination function.
+
+```rust
+use rosenpass_to::{To, to, with_destination};
+use rosenpass_to::ops::copy_array;
+
+/// Copy the given slice to the start of a vector, reusing its memory if possible
+fn copy_to_vec<'a, T>(src: &'a [T]) -> impl To<Vec<T>, ()> + 'a
+        where T: Clone {
+    with_destination(move |dst: &mut Vec<T>| {
+        dst.clear();
+        dst.extend_from_slice(src);
+    })
+}
+
+let mut buf = copy_to_vec(b"Hello World, this is a long text.").to_value();
+assert_eq!(&buf[..], b"Hello World, this is a long text.");
+
+to(&mut buf, copy_to_vec(b"Avoids allocation"));
+assert_eq!(&buf[..], b"Avoids allocation");
+```
+
+This example also shows of some of the advantages of using To: The function gains a very slight allocate over using `.to_vec()` by reusing memory:
+
+```rust
+let mut buf = b"Hello World, this is a long text.".to_vec();
+buf = b"This allocates".to_vec(); // This uses memory allocation
+```
+
+The same pattern can be implemented without `to`, at the cost of being slightly more verbose
+
+```rust
+/// Copy the given slice to the start of a vector, reusing its memory if possible
+fn copy_to_vec<T>(dst: &mut Vec<T>, src: &[T])
+        where T: Clone {
+    dst.clear();
+    dst.extend_from_slice(src);
+}
+
+let mut buf = Vec::default();
+copy_to_vec(&mut buf, b"Hello World, this is a long text.");
+assert_eq!(&buf[..], b"Hello World, this is a long text.");
+
+copy_to_vec(&mut buf, b"Avoids allocation");
+assert_eq!(&buf[..], b"Avoids allocation");
+```
+
+This usability enhancement might seem minor, but when many functions take destination parameters, manually allocating all of these can really become annoying.
+
+## Beside values: Functions with destination and return value
+
+Return values are supported, but `from_this()`, `to_value()`, and `collect()` cannot be used together with return values (unless they implement CondenseBeside – see the next section), since that would erase the return value.
+
+Alternative functions are returned, that return a `to::Beside` value, containing both the
+destination variable and the return value.
+
+```rust
+use std::cmp::{min, max};
+use rosenpass_to::{To, to, with_destination, Beside};
+
+/// Copy an array of floats and calculate the average
+pub fn copy_and_average<'a>(src: &'a[f64]) -> impl To<[f64], f64> + 'a {
+    with_destination(move |dst: &mut [f64]| {
+        assert!(src.len() == dst.len());
+        let mut sum = 0f64;
+        for (d, s) in dst.iter_mut().zip(src.iter()) {
+            *d = *s;
+            sum = sum + *d;
+        }
+        sum / (src.len() as f64)
+    })
+}
+
+let src = [12f64, 13f64, 14f64];
+
+// `.to()` and `to(...)` function as normal, but return the value now
+let mut dst = [0f64; 3];
+let avg = copy_and_average(&src).to(&mut dst);
+assert_eq!((&dst[..], avg), (&src[..], 13f64));
+
+let mut dst = [0f64; 3];
+let avg = to(&mut dst, copy_and_average(&src));
+assert_eq!((&dst[..], avg), (&src[..], 13f64));
+
+// Instead of .to_this, .to_value, or .collect variants returning a beside value have to be used
+
+let Beside(dst, avg) = copy_and_average(&src).to_this_beside(|| [0f64; 3]);
+assert_eq!((&dst[..], avg), (&src[..], 13f64));
+
+let Beside(dst, avg) = copy_and_average(&src).collect_beside::<[f64; 3]>();
+assert_eq!((&dst[..], avg), (&src[..], 13f64));
+
+// Beside values are simple named tuples
+
+let b = copy_and_average(&src).collect_beside::<[f64; 3]>();
+assert_eq!(b, Beside(dst, avg));
+
+// They can convert from and to tuples
+let b_tup = (dst, avg);
+assert_eq!(b, (dst, avg).into());
+assert_eq!(b, Beside::from(b_tup));
+
+// Simple accessors for the value and returned value are provided
+assert_eq!(&dst, b.dest());
+assert_eq!(&avg, b.ret());
+
+let mut tmp = b;
+*tmp.dest_mut() = [42f64; 3];
+*tmp.ret_mut() = 42f64;
+assert_eq!(tmp, Beside([42f64; 3], 42f64));
+```
+
+## Beside Condensation: Working with destinations and Optional or Result
+
+When Beside values contain a `()`, `Option<()>`, or `Result<(), Error>` return value, they expose a special method called `.condense()`; this method consumes the Beside value and condenses destination and return value into one value.
+
+```rust
+use std::result::Result;
+use rosenpass_to::{Beside};
+
+assert_eq!((), Beside((), ()).condense());
+
+assert_eq!(42, Beside(42, ()).condense());
+assert_eq!(None, Beside(42, None).condense());
+
+let ok_unit = Result::<(), ()>::Ok(());
+assert_eq!(Ok(42), Beside(42, ok_unit).condense());
+
+let err_unit = Result::<(), ()>::Err(());
+assert_eq!(Err(()), Beside(42, err_unit).condense());
+```
+
+When condense is implemented for a type, `.to_this(|| ...)`, `.to_value()`, and `.collect::<...>()` on the `To` trait can be used even with a return value:
+
+```rust
+use rosenpass_to::To;
+use rosenpass_to::ops::try_copy_slice;;
+
+let tmp = try_copy_slice(b"Hello World").collect::<[u8; 11]>();
+assert_eq!(tmp, Some(*b"Hello World"));
+
+let tmp = try_copy_slice(b"Hello World").collect::<[u8; 2]>();
+assert_eq!(tmp, None);
+
+let tmp = try_copy_slice(b"Hello World").to_this(|| [0u8; 11].to_vec());
+assert_eq!(tmp, Some(b"Hello World".to_vec()));
+
+let tmp = try_copy_slice(b"Hello World").to_this(|| [0u8; 2].to_vec());
+assert_eq!(tmp, None);
+```
+
+The same naturally also works for Results, but the example is a bit harder to motivate:
+
+```rust
+use std::result::Result;
+use rosenpass_to::{to, To, with_destination};
+
+#[derive(PartialEq, Eq, Debug, Default)]
+struct InvalidFloat;
+
+fn check_float(f: f64) -> Result<(), InvalidFloat> {
+    if f.is_normal() || f == 0.0 {
+        Ok(())
+    } else {
+        Err(InvalidFloat)
+    }
+}
+
+fn checked_add<'a>(src: f64) -> impl To<f64, Result<(), InvalidFloat>> + 'a {
+    with_destination(move |dst: &mut f64| {
+        check_float(src)?;
+        check_float(*dst)?;
+        *dst += src;
+        Ok(())
+    })
+}
+
+let mut tmp = 0.0;
+checked_add(14.0).to(&mut tmp).unwrap();
+checked_add(12.0).to(&mut tmp).unwrap();
+assert_eq!(tmp, 26.0);
+
+assert_eq!(Ok(78.0), checked_add(14.0).to_this(|| 64.0));
+assert_eq!(Ok(14.0), checked_add(14.0).to_value());
+assert_eq!(Ok(14.0), checked_add(14.0).collect());
+
+assert_eq!(Err(InvalidFloat), checked_add(f64::NAN).to_this(|| 64.0));
+assert_eq!(Err(InvalidFloat), checked_add(f64::INFINITY).to_value());
+```
+
+## Custom condensation
+
+Condensation is implemented through a trait called CondenseBeside ([local](CondenseBeside) | [docs.rs](https://docs.rs/to/latest/rosenpass-to/trait.CondenseBeside.html)). You can implement it for your own types.
+
+If you can not implement this trait because its for an external type (see [orphan rule](https://doc.rust-lang.org/book/ch10-02-traits.html#implementing-a-trait-on-a-type)), this crate welcomes contributions of new Condensation rules.
+
+```rust
+use rosenpass_to::{To, with_destination, Beside, CondenseBeside};
+use rosenpass_to::ops::copy_slice;
+
+#[derive(PartialEq, Eq, Debug, Default)]
+struct MyTuple<Left, Right>(Left, Right);
+
+impl<Val, Right> CondenseBeside<Val> for MyTuple<(), Right> {
+    type Condensed = MyTuple<Val, Right>;
+
+    fn condense(self, val: Val) -> MyTuple<Val, Right> {
+        let MyTuple((), right) = self;
+        MyTuple(val, right)
+    }
+}
+
+fn copy_slice_and_return_something<'a, T, U>(src: &'a [T], something: U) -> impl To<[T], U> + 'a
+        where T: Copy, U: 'a {
+    with_destination(move |dst: &mut [T]| {
+        copy_slice(src).to(dst);
+        something
+    })
+}
+
+let tmp = Beside(42, MyTuple((), 23)).condense();
+assert_eq!(tmp, MyTuple(42, 23));
+
+let tmp = copy_slice_and_return_something(b"23", MyTuple((), 42)).collect::<[u8; 2]>();
+assert_eq!(tmp, MyTuple(*b"23", 42));
+```
+
+## Manually implementing the To trait
+
+Using `with_destination(...)` is convenient, but since it uses closures it results in an type that can not be written down, which is why the `-> impl To<...>` pattern is used everywhere in this tutorial.
+
+Implementing the ToTrait manual is the right choice for library use cases.
+
+```rust
+use rosenpass_to::{to, To, with_destination};
+
+struct TryCopySliceSource<'a, T: Copy> {
+    src: &'a [T],
+}
+
+impl<'a, T: Copy> To<[T], Option<()>> for TryCopySliceSource<'a, T> {
+    fn to(self, dst: &mut [T]) -> Option<()> {
+        (self.src.len() == dst.len())
+            .then(|| dst.copy_from_slice(self.src))
+    }
+}
+
+fn try_copy_slice<'a, T>(src: &'a [T]) -> TryCopySliceSource<'a, T>
+        where T: Copy {
+    TryCopySliceSource { src }
+}
+
+let mut dst = try_copy_slice(b"Hello World").collect::<[u8; 11]>().unwrap();
+assert_eq!(&dst[..], b"Hello World");
+assert_eq!(None, to(&mut dst[..], try_copy_slice(b"---")));
+```
+
+## Methods with destination
+
+Destinations can also be used with methods. This example demonstrates using destinations in an extension trait for everything that implements `Borrow<[T]>` for any `T` and a concrete `To` trait implementation.
+
+```rust
+use std::borrow::Borrow;
+use rosenpass_to::{to, To, with_destination};
+
+struct TryCopySliceSource<'a, T: Copy> {
+    src: &'a [T],
+}
+
+impl<'a, T: Copy> To<[T], Option<()>> for TryCopySliceSource<'a, T> {
+    fn to(self, dst: &mut [T]) -> Option<()> {
+        (self.src.len() == dst.len())
+            .then(|| dst.copy_from_slice(self.src))
+    }
+}
+
+trait TryCopySliceExt<'a, T: Copy> {
+    fn try_copy_slice(&'a self)  -> TryCopySliceSource<'a, T>;
+}
+
+impl<'a, T: 'a + Copy, Ref: 'a + Borrow<[T]>> TryCopySliceExt<'a, T> for Ref {
+    fn try_copy_slice(&'a self)  -> TryCopySliceSource<'a, T> {
+        TryCopySliceSource {
+            src: self.borrow()
+        }
+    }
+}
+
+let mut dst = b"Hello World".try_copy_slice().collect::<[u8; 11]>().unwrap();
+assert_eq!(&dst[..], b"Hello World");
+assert_eq!(None, to(&mut dst[..], b"---".try_copy_slice()));
+```

to/src/lib.rs

@@ -0,0 +1,14 @@
+#![doc = include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/README.md"))]
+
+#[cfg(doctest)]
+doc_comment::doctest!("../README.md");
+
+// Core implementation
+mod to;
+pub use crate::to::{
+    beside::Beside, condense::CondenseBeside, dst_coercion::DstCoercion, to_function::to,
+    to_trait::To, with_destination::with_destination,
+};
+
+// Example use cases
+pub mod ops;

to/src/ops.rs

@@ -0,0 +1,80 @@
+//! Functions with destination copying data between slices and arrays.
+
+use crate::{with_destination, To};
+
+/// Function with destination that copies data from
+/// origin into the destination.
+///
+/// # Panics
+///
+/// This function will panic if the two slices have different lengths.
+pub fn copy_slice<'a, T>(origin: &'a [T]) -> impl To<[T], ()> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| out.copy_from_slice(origin))
+}
+
+/// Function with destination that copies all data from
+/// origin into the destination.
+///
+/// Destination may be longer than origin.
+///
+/// # Panics
+///
+/// This function will panic if destination is shorter than origin.
+pub fn copy_slice_least_src<'a, T>(origin: &'a [T]) -> impl To<[T], ()> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| copy_slice(origin).to(&mut out[..origin.len()]))
+}
+
+/// Function with destination that copies as much data as possible from origin to the
+/// destination.
+///
+/// Copies as much data as is present in the shorter slice.
+pub fn copy_slice_least<'a, T>(origin: &'a [T]) -> impl To<[T], ()> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| {
+        let len = std::cmp::min(origin.len(), out.len());
+        copy_slice(&origin[..len]).to(&mut out[..len])
+    })
+}
+
+/// Function with destination that attempts to copy data from origin into the destination.
+///
+/// Will return None if the slices are of different lengths.
+pub fn try_copy_slice<'a, T>(origin: &'a [T]) -> impl To<[T], Option<()>> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| {
+        (origin.len() == out.len()).then(|| copy_slice(origin).to(out))
+    })
+}
+
+/// Function with destination that tries to copy all data from
+/// origin into the destination.
+///
+/// Destination may be longer than origin.
+///
+/// Will return None if the destination is shorter than origin.
+pub fn try_copy_slice_least_src<'a, T>(origin: &'a [T]) -> impl To<[T], Option<()>> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T]| {
+        (origin.len() <= out.len()).then(|| copy_slice_least_src(origin).to(out))
+    })
+}
+
+/// Function with destination that copies all data between two array references.
+pub fn copy_array<'a, T, const N: usize>(origin: &'a [T; N]) -> impl To<[T; N], ()> + 'a
+where
+    T: Copy,
+{
+    with_destination(|out: &mut [T; N]| out.copy_from_slice(origin))
+}

to/src/to/beside.rs

@@ -0,0 +1,45 @@
+use crate::CondenseBeside;
+
+/// Named tuple holding the return value and the output from a function with destinations.
+#[derive(Debug, PartialEq, Eq, Default, PartialOrd, Ord, Copy, Clone)]
+pub struct Beside<Val, Ret>(pub Val, pub Ret);
+
+impl<Val, Ret> Beside<Val, Ret> {
+    pub fn dest(&self) -> &Val {
+        &self.0
+    }
+
+    pub fn ret(&self) -> &Ret {
+        &self.1
+    }
+
+    pub fn dest_mut(&mut self) -> &mut Val {
+        &mut self.0
+    }
+
+    pub fn ret_mut(&mut self) -> &mut Ret {
+        &mut self.1
+    }
+
+    /// Perform beside condensation. See [CondenseBeside]
+    pub fn condense(self) -> <Ret as CondenseBeside<Val>>::Condensed
+    where
+        Ret: CondenseBeside<Val>,
+    {
+        self.1.condense(self.0)
+    }
+}
+
+impl<Val, Ret> From<(Val, Ret)> for Beside<Val, Ret> {
+    fn from(tuple: (Val, Ret)) -> Self {
+        let (val, ret) = tuple;
+        Self(val, ret)
+    }
+}
+
+impl<Val, Ret> From<Beside<Val, Ret>> for (Val, Ret) {
+    fn from(beside: Beside<Val, Ret>) -> Self {
+        let Beside(val, ret) = beside;
+        (val, ret)
+    }
+}

to/src/to/condense.rs

@@ -0,0 +1,37 @@
+/// Beside condensation.
+///
+/// This trait can be used to enable the use of [to_this(|| ...)](crate::To::to_this),
+/// [to_value()](crate::To::to_value), and [collect::<...>()](crate::To::collect) with custom
+/// types.
+///
+/// The function [Beside::condense()](crate::Beside::condense) is a shorthand for using the
+/// condense trait.
+pub trait CondenseBeside<Val> {
+    type Condensed;
+
+    fn condense(self, ret: Val) -> Self::Condensed;
+}
+
+impl<Val> CondenseBeside<Val> for () {
+    type Condensed = Val;
+
+    fn condense(self, ret: Val) -> Val {
+        ret
+    }
+}
+
+impl<Val, Error> CondenseBeside<Val> for Result<(), Error> {
+    type Condensed = Result<Val, Error>;
+
+    fn condense(self, ret: Val) -> Result<Val, Error> {
+        self.map(|()| ret)
+    }
+}
+
+impl<Val> CondenseBeside<Val> for Option<()> {
+    type Condensed = Option<Val>;
+
+    fn condense(self, ret: Val) -> Option<Val> {
+        self.map(|()| ret)
+    }
+}

to/src/to/dst_coercion.rs

@@ -0,0 +1,17 @@
+/// Helper performing explicit unsized coercion.
+/// Used by the [to](crate::to()) function.
+pub trait DstCoercion<Dst: ?Sized> {
+    fn coerce_dest(&mut self) -> &mut Dst;
+}
+
+impl<T: ?Sized> DstCoercion<T> for T {
+    fn coerce_dest(&mut self) -> &mut T {
+        self
+    }
+}
+
+impl<T, const N: usize> DstCoercion<[T]> for [T; N] {
+    fn coerce_dest(&mut self) -> &mut [T] {
+        self
+    }
+}

to/src/to/mod.rs

@@ -0,0 +1,20 @@
+//! Module implementing the core function with destination functionality.
+//!
+//! Parameter naming scheme
+//!
+//! - `Src: impl To<Dst, Ret>` – The value of an instance of something implementing the `To` trait
+//! - `Dst: ?Sized`; (e.g. [u8]) – The target to write to
+//! - `Out: Sized = &mut Dst`; (e.g. &mut [u8]) – A reference to the target to write to
+//! - `Coercable: ?Sized + DstCoercion<Dst>`; (e.g. `[u8]`, `[u8; 16]`) – Some value that
+//! destination coercion can be applied to. Usually either `Dst` itself (e.g. `[u8]` or some sized variant of
+//! `Dst` (e.g. `[u8; 64]`).
+//! - `Ret: Sized`; (anything) – must be `CondenseBeside<_>` if condensing is to be applied. The ordinary return value of a function with an output
+//! - `Val: Sized + BorrowMut<Dst>`; (e.g. [u8; 16]) – Some owned storage that can be borrowed as `Dst`
+//! - `Condensed: Sized = CondenseBeside<Val>::Condensed`; (e.g. [u8; 16], Result<[u8; 16]>) – The combiation of Val and Ret after condensing was applied (`Beside<Val, Ret>::condense()`/`Ret::condense(v)` for all `v : Val`).
+
+pub mod beside;
+pub mod condense;
+pub mod dst_coercion;
+pub mod to_function;
+pub mod to_trait;
+pub mod with_destination;

to/src/to/to_function.rs

@@ -0,0 +1,14 @@
+use crate::{DstCoercion, To};
+
+/// Alias for [To::to] moving the destination to the left.
+///
+/// This provides similar haptics to the let assignment syntax is rust, which also keeps
+/// the variable to assign to on the left and the generating function on the right.
+pub fn to<Coercable, Src, Dst, Ret>(dst: &mut Coercable, src: Src) -> Ret
+where
+    Coercable: ?Sized + DstCoercion<Dst>,
+    Src: To<Dst, Ret>,
+    Dst: ?Sized,
+{
+    src.to(dst.coerce_dest())
+}

to/src/to/to_trait.rs

@@ -0,0 +1,96 @@
+use crate::{Beside, CondenseBeside};
+use std::borrow::BorrowMut;
+
+// The To trait is the core of the to crate; most functions with destinations will either return
+// an object that is an instance of this trait or they will return `-> impl To<Destination,
+// Return_value`.
+//
+// A quick way to implement a function with destination is to use the
+// [with_destination(|param: &mut Type| ...)] higher order function.
+pub trait To<Dst: ?Sized, Ret>: Sized {
+    fn to(self, out: &mut Dst) -> Ret;
+
+    /// Generate a destination on the fly with a lambda.
+    ///
+    /// Calls the provided closure to create a value,
+    /// calls [crate::to()] to evaluate the function and finally
+    /// returns a [Beside] instance containing the generated destination value and the return
+    /// value.
+    fn to_this_beside<Val, Fun>(self, fun: Fun) -> Beside<Val, Ret>
+    where
+        Val: BorrowMut<Dst>,
+        Fun: FnOnce() -> Val,
+    {
+        let mut val = fun();
+        let ret = self.to(val.borrow_mut());
+        Beside(val, ret)
+    }
+
+    /// Generate a destination on the fly using default.
+    ///
+    /// Uses [Default] to create a value,
+    /// calls [crate::to()] to evaluate the function and finally
+    /// returns a [Beside] instance containing the generated destination value and the return
+    /// value.
+    fn to_value_beside(self) -> Beside<Dst, Ret>
+    where
+        Dst: Sized + Default,
+    {
+        self.to_this_beside(|| Dst::default())
+    }
+
+    /// Generate a destination on the fly using default and a custom storage type.
+    ///
+    /// Uses [Default] to create a value of the given type,
+    /// calls [crate::to()] to evaluate the function and finally
+    /// returns a [Beside] instance containing the generated destination value and the return
+    /// value.
+    ///
+    /// Using collect_beside with an explicit type instead of [Self::to_value_beside] is mainly useful
+    /// when the Destination is unsized.
+    ///
+    /// This could be the case when the destination is an `[u8]` for instance.
+    fn collect_beside<Val>(self) -> Beside<Val, Ret>
+    where
+        Val: Default + BorrowMut<Dst>,
+    {
+        self.to_this_beside(|| Val::default())
+    }
+
+    /// Generate a destination on the fly with a lambda, condensing the destination and the
+    /// return value into one.
+    ///
+    /// This is like using [Self::to_this_beside] followed by calling [Beside::condense].
+    fn to_this<Val, Fun>(self, fun: Fun) -> <Ret as CondenseBeside<Val>>::Condensed
+    where
+        Ret: CondenseBeside<Val>,
+        Val: BorrowMut<Dst>,
+        Fun: FnOnce() -> Val,
+    {
+        self.to_this_beside(fun).condense()
+    }
+
+    /// Generate a destination on the fly using default, condensing the destination and the
+    /// return value into one.
+    ///
+    /// This is like using [Self::to_value_beside] followed by calling [Beside::condense].
+    fn to_value(self) -> <Ret as CondenseBeside<Dst>>::Condensed
+    where
+        Dst: Sized + Default,
+        Ret: CondenseBeside<Dst>,
+    {
+        self.to_value_beside().condense()
+    }
+
+    /// Generate a destination on the fly using default, condensing the destination and the
+    /// return value into one.
+    ///
+    /// This is like using [Self::collect_beside] followed by calling [Beside::condense].
+    fn collect<Val>(self) -> <Ret as CondenseBeside<Val>>::Condensed
+    where
+        Val: Default + BorrowMut<Dst>,
+        Ret: CondenseBeside<Val>,
+    {
+        self.collect_beside::<Val>().condense()
+    }
+}

to/src/to/with_destination.rs

@@ -0,0 +1,35 @@
+use crate::To;
+use std::marker::PhantomData;
+
+struct ToClosure<Dst, Ret, Fun>
+where
+    Dst: ?Sized,
+    Fun: FnOnce(&mut Dst) -> Ret,
+{
+    fun: Fun,
+    _val: PhantomData<Box<Dst>>,
+}
+
+impl<Dst, Ret, Fun> To<Dst, Ret> for ToClosure<Dst, Ret, Fun>
+where
+    Dst: ?Sized,
+    Fun: FnOnce(&mut Dst) -> Ret,
+{
+    fn to(self, out: &mut Dst) -> Ret {
+        (self.fun)(out)
+    }
+}
+
+/// Used to create a function with destination.
+///
+/// See the tutorial in [readme.me]..
+pub fn with_destination<Dst, Ret, Fun>(fun: Fun) -> impl To<Dst, Ret>
+where
+    Dst: ?Sized,
+    Fun: FnOnce(&mut Dst) -> Ret,
+{
+    ToClosure {
+        fun,
+        _val: PhantomData,
+    }
+}

util/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "rosenpass-util"
+version = "0.1.0"
+authors = ["Karolin Varner <karo@cupdev.net>", "wucke13 <wucke13@gmail.com>"]
+edition = "2021"
+license = "MIT OR Apache-2.0"
+description = "Rosenpass internal utilities"
+homepage = "https://rosenpass.eu/"
+repository = "https://github.com/rosenpass/rosenpass"
+readme = "readme.md"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+base64 = { workspace = true }
+anyhow = { workspace = true }

util/src/b64.rs

@@ -0,0 +1,20 @@
+use base64::{
+    display::Base64Display as B64Display, read::DecoderReader as B64Reader,
+    write::EncoderWriter as B64Writer,
+};
+use std::io::{Read, Write};
+
+use base64::engine::general_purpose::GeneralPurpose as Base64Engine;
+const B64ENGINE: Base64Engine = base64::engine::general_purpose::STANDARD;
+
+pub fn fmt_b64<'a>(payload: &'a [u8]) -> B64Display<'a, 'static, Base64Engine> {
+    B64Display::<'a, 'static>::new(payload, &B64ENGINE)
+}
+
+pub fn b64_writer<W: Write>(w: W) -> B64Writer<'static, Base64Engine, W> {
+    B64Writer::new(w, &B64ENGINE)
+}
+
+pub fn b64_reader<R: Read>(r: R) -> B64Reader<'static, Base64Engine, R> {
+    B64Reader::new(r, &B64ENGINE)
+}

util/src/file.rs

@@ -0,0 +1,63 @@
+use anyhow::ensure;
+use std::fs::File;
+use std::io::Read;
+use std::result::Result;
+use std::{fs::OpenOptions, path::Path};
+
+/// Open a file writable
+pub fn fopen_w<P: AsRef<Path>>(path: P) -> std::io::Result<File> {
+    Ok(OpenOptions::new()
+        .read(false)
+        .write(true)
+        .create(true)
+        .truncate(true)
+        .open(path)?)
+}
+/// Open a file readable
+pub fn fopen_r<P: AsRef<Path>>(path: P) -> std::io::Result<File> {
+    Ok(OpenOptions::new()
+        .read(true)
+        .write(false)
+        .create(false)
+        .truncate(false)
+        .open(path)?)
+}
+
+pub trait ReadExactToEnd {
+    type Error;
+
+    fn read_exact_to_end(&mut self, buf: &mut [u8]) -> Result<(), Self::Error>;
+}
+
+impl<R: Read> ReadExactToEnd for R {
+    type Error = anyhow::Error;
+
+    fn read_exact_to_end(&mut self, buf: &mut [u8]) -> anyhow::Result<()> {
+        let mut dummy = [0u8; 8];
+        self.read_exact(buf)?;
+        ensure!(self.read(&mut dummy)? == 0, "File too long!");
+        Ok(())
+    }
+}
+
+pub trait LoadValue {
+    type Error;
+
+    fn load<P: AsRef<Path>>(path: P) -> Result<Self, Self::Error>
+    where
+        Self: Sized;
+}
+
+pub trait LoadValueB64 {
+    type Error;
+
+    fn load_b64<P: AsRef<Path>>(path: P) -> Result<Self, Self::Error>
+    where
+        Self: Sized;
+}
+
+pub trait StoreValue {
+    type Error;
+
+    fn store<P: AsRef<Path>>(&self, path: P) -> Result<(), Self::Error>;
+}

util/src/functional.rs

@@ -0,0 +1,15 @@
+pub fn mutating<T, F>(mut v: T, f: F) -> T
+where
+    F: Fn(&mut T),
+{
+    f(&mut v);
+    v
+}
+
+pub fn sideeffect<T, F>(v: T, f: F) -> T
+where
+    F: Fn(&T),
+{
+    f(&v);
+    v
+}

util/src/lib.rs

@@ -0,0 +1,7 @@
+pub mod b64;
+pub mod file;
+pub mod functional;
+pub mod mem;
+pub mod ord;
+pub mod result;
+pub mod time;

util/src/mem.rs

@@ -0,0 +1,33 @@
+use std::borrow::{Borrow, BorrowMut};
+use std::cmp::min;
+
+/// Concatenate two byte arrays
+// TODO: Zeroize result?
+#[macro_export]
+macro_rules! cat {
+    ($len:expr; $($toks:expr),+) => {{
+        let mut buf = [0u8; $len];
+        let mut off = 0;
+        $({
+            let tok = $toks;
+            let tr = ::std::borrow::Borrow::<[u8]>::borrow(tok);
+            (&mut buf[off..(off + tr.len())]).copy_from_slice(tr);
+            off += tr.len();
+        })+
+        assert!(off == buf.len(), "Size mismatch in cat!()");
+        buf
+    }}
+}
+
+// TODO: consistent inout ordering
+pub fn cpy<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, dst: &mut T) {
+    dst.borrow_mut().copy_from_slice(src.borrow());
+}
+
+/// Copy from `src` to `dst`. If `src` and `dst` are not of equal length, copy as many bytes as possible.
+pub fn cpy_min<T: BorrowMut<[u8]> + ?Sized, F: Borrow<[u8]> + ?Sized>(src: &F, dst: &mut T) {
+    let src = src.borrow();
+    let dst = dst.borrow_mut();
+    let len = min(src.len(), dst.len());
+    dst[..len].copy_from_slice(&src[..len]);
+}

util/src/ord.rs

@@ -0,0 +1,8 @@
+// TODO remove this once std::cmp::max becomes const
+pub const fn max_usize(a: usize, b: usize) -> usize {
+    if a > b {
+        a
+    } else {
+        b
+    }
+}

util/src/result.rs

@@ -0,0 +1,7 @@
+/// Try block basically…returns a result and allows the use of the question mark operator inside
+#[macro_export]
+macro_rules! attempt {
+    ($block:expr) => {
+        (|| -> ::anyhow::Result<_> { $block })()
+    };
+}

util/src/time.rs

@@ -0,0 +1,20 @@
+use std::time::{Duration, Instant};
+
+#[derive(Clone, Debug)]
+pub struct Timebase(Instant);
+
+impl Default for Timebase {
+    fn default() -> Self {
+        Self(Instant::now())
+    }
+}
+
+impl Timebase {
+    pub fn now(&self) -> f64 {
+        self.0.elapsed().as_secs_f64()
+    }
+
+    pub fn dur(&self, t: f64) -> Duration {
+        Duration::from_secs_f64(t)
+    }
+}