voice-cat/dotnet/tests/VoiceCat.Tests/MediaTests.cs

using System.Buffers.Binary;
using VoiceCat.Crypto;
using VoiceCat.Protocol;

namespace VoiceCat.Tests;

public class MediaTests
{
    private static readonly byte[] Key = Enumerable.Range(0, 32).Select(i => (byte)i).ToArray();
    private static readonly VoiceFrameHeader Header = new(MediaFrameType.Voice, VoiceFrameFlags.Marker, 0, 0xcafebabe, 0, 960);

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void BothBackendsProduceIdenticalPackets(bool managed)
    {
        using var sender = new MediaEncryptor(Key, managed);
        using var receiver = new MediaDecryptor(Key, !managed);
        byte[] plaintext = Enumerable.Range(0, 100).Select(i => (byte)i).ToArray();
        byte[] packet = Seal(sender, plaintext);
        byte[] output = new byte[plaintext.Length];
        Assert.True(receiver.TryDecrypt(packet, output, out var header, out int written));
        Assert.Equal(Header, header);
        Assert.Equal(plaintext.Length, written);
        Assert.Equal(plaintext, output);
        Assert.False(receiver.TryDecrypt(packet, output, out _, out written));
        Assert.Equal(0, written);
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void ForgedCounterDoesNotPoisonReplayWindow(bool managed)
    {
        using var sender = new MediaEncryptor(Key, managed);
        using var receiver = new MediaDecryptor(Key, managed);
        byte[] output = new byte[8];
        Assert.True(receiver.TryDecrypt(Seal(sender, new byte[8]), output, out _, out _));
        byte[] packet = Seal(sender, new byte[8]);
        byte[] forged = (byte[])packet.Clone();
        BinaryPrimitives.WriteUInt64BigEndian(forged.AsSpan(8), ulong.MaxValue);
        Array.Fill(output, (byte)0xaa);
        Assert.False(receiver.TryDecrypt(forged, output, out var header, out int written));
        Assert.Equal(default, header);
        Assert.Equal(0, written);
        Assert.All(output, value => Assert.Equal(0, value));
        Assert.True(receiver.TryDecrypt(packet, output, out _, out _));
        Assert.True(receiver.TryDecrypt(Seal(sender, new byte[8]), output, out _, out _));
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void TamperingEveryPacketRegionFailsAuthentication(bool managed)
    {
        using var sender = new MediaEncryptor(Key, managed);
        byte[] packet = Seal(sender, new byte[80]);
        for (int i = 0; i < packet.Length; i++)
        {
            using var receiver = new MediaDecryptor(Key, managed);
            byte[] tampered = (byte[])packet.Clone();
            tampered[i] ^= 0x80;
            Assert.False(receiver.TryDecrypt(tampered, new byte[80], out _, out _));
            Assert.True(receiver.TryDecrypt(packet, new byte[80], out _, out _));
        }
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void ReplayWindowAcceptsReorderingAndRejectsOldPackets(bool managed)
    {
        using var sender = new MediaEncryptor(Key, managed);
        using var receiver = new MediaDecryptor(Key, managed);
        var packets = Enumerable.Range(0, 130).Select(_ => Seal(sender, new byte[1])).ToArray();
        byte[] output = new byte[1];
        Assert.True(receiver.TryDecrypt(packets[64], output, out _, out _));
        Assert.False(receiver.TryDecrypt(packets[0], output, out _, out _));
        Assert.True(receiver.TryDecrypt(packets[1], output, out _, out _));
        Assert.False(receiver.TryDecrypt(packets[1], output, out _, out _));
        Assert.True(receiver.TryDecrypt(packets[63], output, out _, out _));
        Assert.True(receiver.TryDecrypt(packets[129], output, out _, out _));
        Assert.False(receiver.TryDecrypt(packets[64], output, out _, out _));
        Assert.True(receiver.TryDecrypt(packets[128], output, out _, out _));
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void CounterCrossesOldSixteenBitBoundary(bool managed)
    {
        using var sender = new MediaEncryptor(Key, managed, 65534);
        using var receiver = new MediaDecryptor(Key, managed);
        for (ulong sequence = 65534; sequence < 65540; sequence++)
        {
            Assert.True(receiver.TryDecrypt(Seal(sender, new byte[1]), new byte[1], out var header, out _));
            Assert.Equal(sequence, header.Sequence);
        }
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void InterleavedRelayUsesRecipientCounter(bool managed)
    {
        byte[] otherKey = Enumerable.Repeat((byte)42, 32).ToArray();
        using var a = new MediaEncryptor(Key, managed);
        using var b = new MediaEncryptor(otherKey, managed);
        using var receiveA = new MediaDecryptor(Key, managed);
        using var receiveB = new MediaDecryptor(otherKey, managed);
        using var relay = new MediaEncryptor(Key, managed);
        using var listener = new MediaDecryptor(Key, managed);
        byte[] plaintext = [1, 2, 3];
        byte[] decoded = new byte[3];
        for (int i = 0; i < 16; i++)
        {
            var sender = i % 2 == 0 ? a : b;
            var receiver = i % 2 == 0 ? receiveA : receiveB;
            Assert.True(receiver.TryDecrypt(Seal(sender, plaintext), decoded, out var header, out _));
            byte[] packet = new byte[39];
            relay.Encrypt(header, decoded, packet);
            Assert.True(listener.TryDecrypt(packet, decoded, out var relayedHeader, out _));
            Assert.Equal((ulong)i, relayedHeader.Sequence);
            Assert.Equal(plaintext, decoded);
        }
    }

    [Theory]
    [InlineData(false)]
    [InlineData(true)]
    public void EmptyPayloadAndLargeCountersWork(bool managed)
    {
        using var sender = new MediaEncryptor(Key, managed, ulong.MaxValue - 1);
        using var receiver = new MediaDecryptor(Key, managed);
        var packet = Seal(sender, []);
        Assert.True(receiver.TryDecrypt(packet, [], out var header, out int written));
        Assert.Equal(ulong.MaxValue - 1, header.Sequence);
        Assert.Equal(0, written);
        Assert.Throws<InvalidOperationException>(() => Seal(sender, []));
    }

    [Fact]
    public void InvalidArgumentsAndDisposedInstancesAreRejected()
    {
        Assert.Throws<ArgumentException>(() => new MediaEncryptor(new byte[31]));
        using var sender = new MediaEncryptor(Key);
        using var receiver = new MediaDecryptor(Key);
        Assert.Throws<ArgumentOutOfRangeException>(() => sender.Encrypt(Header, new byte[1], new byte[36]));
        byte[] packet = Seal(sender, new byte[8]);
        Assert.True(receiver.TryDecrypt(packet, new byte[8], out var header, out _));
        Assert.Equal(0UL, header.Sequence);
        Assert.False(receiver.TryDecrypt(new byte[35], [], out _, out _));
        Assert.Throws<ArgumentOutOfRangeException>(() => receiver.TryDecrypt(packet, [], out _, out _));
        sender.Dispose();
        receiver.Dispose();
        Assert.Throws<ObjectDisposedException>(() => Seal(sender, []));
        Assert.Throws<ObjectDisposedException>(() => receiver.TryDecrypt(packet, new byte[8], out _, out _));
    }

    private static byte[] Seal(MediaEncryptor sender, byte[] plaintext)
    {
        byte[] packet = new byte[VoiceFrameHeader.Size + plaintext.Length + MediaEncryptor.TagSize];
        Assert.Equal(packet.Length, sender.Encrypt(Header, plaintext, packet));
        return packet;
    }
}