refactor core

go/grpc_server/auth/auth.go

@@ -0,0 +1,54 @@
+package auth
+
+import (
+	"context"
+
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/status"
+)
+
+// Authenticator exposes a function for authenticating requests.
+type Authenticator struct {
+	Token string
+}
+
+// Authenticate checks that a token exists and is valid. It stores the user
+// metadata in the returned context and removes the token from the context.
+func (a Authenticator) Authenticate(ctx context.Context) (newCtx context.Context, err error) {
+	auth, err := extractHeader(ctx, "nekoray_auth")
+	if err != nil {
+		return ctx, err
+	}
+
+	if auth != a.Token {
+		return ctx, status.Error(codes.Unauthenticated, "invalid token")
+	}
+
+	return purgeHeader(ctx, "nekoray_auth"), nil
+}
+
+func extractHeader(ctx context.Context, header string) (string, error) {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return "", status.Error(codes.Unauthenticated, "no headers in request")
+	}
+
+	authHeaders, ok := md[header]
+	if !ok {
+		return "", status.Error(codes.Unauthenticated, "no header in request")
+	}
+
+	if len(authHeaders) != 1 {
+		return "", status.Error(codes.Unauthenticated, "more than 1 header in request")
+	}
+
+	return authHeaders[0], nil
+}
+
+func purgeHeader(ctx context.Context, header string) context.Context {
+	md, _ := metadata.FromIncomingContext(ctx)
+	mdCopy := md.Copy()
+	mdCopy[header] = nil
+	return metadata.NewIncomingContext(ctx, mdCopy)
+}