Fix a bunch of scanning / tagging bugs (#3154)

* Fix possible infinite loop/stack overflow with weird/broken zip files
* Fix path length calculation using bytes instead of characters (runes)
* Fix bug where oshash gets buffers with size not actually multiple of 8
* Add oshash tests

Co-authored-by: WithoutPants <53250216+WithoutPants@users.noreply.github.com>

pkg/hash/oshash/oshash.go

@@ -46,15 +46,16 @@ func oshash(size int64, head []byte, tail []byte) (string, error) {
 	return fmt.Sprintf("%016x", result), nil
 }
 
-// FromFilePath calculates the hash reading from src.
+// FromReader calculates the hash reading from src.
 func FromReader(src io.ReadSeeker, fileSize int64) (string, error) {
-	if fileSize <= 0 {
-		return "", fmt.Errorf("cannot calculate oshash for empty file (size %d)", fileSize)
+	if fileSize <= 8 {
+		return "", fmt.Errorf("cannot calculate oshash where size < 8 (%d)", fileSize)
 	}
 
 	fileChunkSize := chunkSize
 	if fileSize < fileChunkSize {
-		fileChunkSize = fileSize
+		// Must be a multiple of 8.
+		fileChunkSize = (fileSize / 8) * 8
 	}
 
 	head := make([]byte, fileChunkSize)
@@ -67,7 +68,7 @@ func FromReader(src io.ReadSeeker, fileSize int64) (string, error) {
 	}
 
 	// seek to the end of the file - the chunk size
-	_, err = src.Seek(-fileChunkSize, 2)
+	_, err = src.Seek(-fileChunkSize, io.SeekEnd)
 	if err != nil {
 		return "", err
 	}

pkg/hash/oshash/oshash_internal_test.go

@@ -1,75 +0,0 @@
-package oshash
-
-import (
-	"math/rand"
-	"testing"
-)
-
-// Note that the public API returns "" instead.
-func TestOshashEmpty(t *testing.T) {
-	var size int64
-	head := make([]byte, chunkSize)
-	tail := make([]byte, chunkSize)
-	want := "0000000000000000"
-	got, err := oshash(size, head, tail)
-	if err != nil {
-		t.Errorf("TestOshashEmpty: Error from oshash: %v", err)
-	}
-	if got != want {
-		t.Errorf("TestOshashEmpty: oshash(0, 0, 0) = %q; want %q", got, want)
-	}
-}
-
-// As oshash sums byte values, causing collisions is trivial.
-func TestOshashCollisions(t *testing.T) {
-	buf1 := []byte("this is dumb")
-	buf2 := []byte("dumb is this")
-	size := int64(len(buf1))
-	head := make([]byte, chunkSize)
-
-	tail1 := make([]byte, chunkSize)
-	copy(tail1[len(tail1)-len(buf1):], buf1)
-	hash1, err := oshash(size, head, tail1)
-	if err != nil {
-		t.Errorf("TestOshashCollisions: Error from oshash: %v", err)
-	}
-
-	tail2 := make([]byte, chunkSize)
-	copy(tail2[len(tail2)-len(buf2):], buf2)
-	hash2, err := oshash(size, head, tail2)
-	if err != nil {
-		t.Errorf("TestOshashCollisions: Error from oshash: %v", err)
-	}
-
-	if hash1 != hash2 {
-		t.Errorf("TestOshashCollisions: oshash(n, k, ... %v) =! oshash(n, k, ... %v)", buf1, buf2)
-	}
-}
-
-func BenchmarkOsHash(b *testing.B) {
-	src := rand.NewSource(9999)
-	r := rand.New(src)
-
-	size := int64(1234567890)
-
-	head := make([]byte, 1024*64)
-	_, err := r.Read(head)
-	if err != nil {
-		b.Errorf("unable to generate head array: %v", err)
-	}
-
-	tail := make([]byte, 1024*64)
-	_, err = r.Read(tail)
-	if err != nil {
-		b.Errorf("unable to generate tail array: %v", err)
-	}
-
-	b.ResetTimer()
-
-	for n := 0; n < b.N; n++ {
-		_, err := oshash(size, head, tail)
-		if err != nil {
-			b.Errorf("unexpected error: %v", err)
-		}
-	}
-}

pkg/hash/oshash/oshash_test.go

@@ -0,0 +1,111 @@
+package oshash
+
+import (
+	"bytes"
+	"math/rand"
+	"testing"
+)
+
+func BenchmarkOsHash(b *testing.B) {
+	src := rand.NewSource(9999)
+	r := rand.New(src)
+
+	size := int64(1234567890)
+
+	head := make([]byte, 1024*64)
+	_, err := r.Read(head)
+	if err != nil {
+		b.Errorf("unable to generate head array: %v", err)
+	}
+
+	tail := make([]byte, 1024*64)
+	_, err = r.Read(tail)
+	if err != nil {
+		b.Errorf("unable to generate tail array: %v", err)
+	}
+
+	b.ResetTimer()
+
+	for n := 0; n < b.N; n++ {
+		_, err := oshash(size, head, tail)
+		if err != nil {
+			b.Errorf("unexpected error: %v", err)
+		}
+	}
+}
+
+func TestFromReader(t *testing.T) {
+	makeByteArray := func(base []byte, mag int) []byte {
+		ret := base
+		for i := 0; i < mag; i++ {
+			ret = append(ret, ret...)
+		}
+		return ret
+	}
+
+	makeTailArray := func(base []byte, tail []byte) []byte {
+		ret := base
+		t := make([]byte, chunkSize)
+		copy(t[len(t)-len(tail):], tail)
+		ret = append(ret, t...)
+		return ret
+	}
+
+	tests := []struct {
+		name    string
+		data    []byte
+		want    string
+		wantErr bool
+	}{
+		{
+			"empty",
+			[]byte{},
+			"",
+			true,
+		},
+		{
+			"regular",
+			makeByteArray([]byte("this is a test"), 15),
+			"6a0eba04654d0b9b",
+			false,
+		},
+		{
+			"< chunk size",
+			[]byte("hello world"),
+			"d3e392dee38cd4df",
+			false,
+		},
+		{
+			"< 8",
+			[]byte("hello"),
+			"",
+			true,
+		},
+		{
+			"identical #1",
+			makeTailArray(make([]byte, chunkSize), []byte("this is dumb")),
+			"d5d6ddd820756920",
+			false,
+		},
+		{
+			"identical #2",
+			makeTailArray(make([]byte, chunkSize), []byte("dumb is this")),
+			"d5d6ddd820756920",
+			false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := bytes.NewReader(tt.data)
+
+			got, err := FromReader(r, int64(len(tt.data)))
+			if (err != nil) != tt.wantErr {
+				t.Errorf("FromReader() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("FromReader() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}