fixy fixy, improvey improvey

Author: JackDoan

connection_state.go

@@ -81,6 +81,7 @@ func (cs *ConnectionState) Decrypt(l *slog.Logger, messageCounter uint64, out []
 	return out, nil
 }
 
+// VerifyRelay verifies AEAD protected (but not encrypted) relay frames. packet must be length-checked by the caller.
 func (cs *ConnectionState) VerifyRelay(l *slog.Logger, messageCounter uint64, packet []byte, nb []byte) error {
 	cs.decryptLock.Lock()
 	result := cs.window.Check(l, messageCounter)
@@ -89,15 +90,9 @@ func (cs *ConnectionState) VerifyRelay(l *slog.Logger, messageCounter uint64, pa
 		return ErrAlreadySeen
 	}
 
-	// The entire body is sent as AD, not encrypted.
-	// The packet consists of a 16-byte parsed Nebula header, Associated Data-protected payload, and a trailing 16-byte AEAD signature value.
-	// The packet is guaranteed to be at least 16 bytes at this point, b/c it got past the h.Parse() call above. If it's
-	// otherwise malformed (meaning, there is no trailing 16 byte AEAD value), then this will result in at worst a 0-length slice
-	// which will gracefully fail in the DecryptDanger call.
 	signedPayload := packet[:len(packet)-cs.dKey.Overhead()]
 	signatureValue := packet[len(packet)-cs.dKey.Overhead():]
-	var err error
-	_, err = cs.dKey.DecryptDanger(nil, signedPayload, signatureValue, messageCounter, nb)
+	_, err := cs.dKey.DecryptDanger(nil, signedPayload, signatureValue, messageCounter, nb)
 	if err != nil {
 		return err
 	}

outside.go

@@ -102,6 +102,14 @@ func (f *Interface) readOutsidePackets(via ViaSender, out []byte, packet []byte,
 		return
 	}
 
+	if len(packet) < header.Len+hostinfo.ConnectionState.dKey.Overhead() {
+		f.messageMetrics.RxInvalid(1)
+		if f.l.Enabled(context.Background(), slog.LevelDebug) {
+			f.l.Debug("packet too small", "from", via, "length", len(packet))
+		}
+		return
+	}
+
 	// All remaining packets are encrypted
 	if isMessageRelay {
 		// Relay packets are special, this branch should always early-return