Radicade/ServerTests/ImageSignatureRequestTests.cs

using System.Text;
using Xunit;

namespace RadicadeServer.Tests;

public class ImageSignatureRequestTests
{
    private static byte[] Metadata(params string[] literals)
    {
        using var stream = new MemoryStream();
        using var writer = new BinaryWriter(stream);
        writer.Write(0xFAB11BAFu);
        writer.Write(27);
        writer.Write(24);
        writer.Write(literals.Length * 8);
        writer.Write(24 + literals.Length * 8);
        writer.Write(literals.Sum(s => Encoding.UTF8.GetByteCount(s)));
        int index = 0;
        foreach (var literal in literals)
        {
            int size = Encoding.UTF8.GetByteCount(literal);
            writer.Write(size);
            writer.Write(index);
            index += size;
        }
        foreach (var literal in literals) writer.Write(Encoding.UTF8.GetBytes(literal));
        return stream.ToArray();
    }

    [Theory]
    [InlineData(".rec.net")]
    [InlineData(".radicade.internal")]
    public void ClientMetadataControlsHeaderEvenOnWrongRoute(string tail)
    {
        var key = ImageSignatureRequest.DetectKeyId(Metadata("https://img.rec.net", tail));
        Assert.Equal("KEY:RSA:p1" + tail, key);
        var url = NameserverRedirect.Rewrite("https://img.rec.net/photo?width=64&sig=p1", "https://private.example");
        url = ImageSignatureRequest.AddKeyId(url, "https://private.example", key);
        Assert.Contains("width=64&sig=p1&rcsig=" + Uri.EscapeDataString(key), url);
        var header = RadicadeServer.Images.ImageAPI.SignatureFor(key, "bare", RadicadeServer.Images.ImageAPI.StockKeyId);
        Assert.StartsWith("key-id=" + key + "; data=", header);
        Assert.Equal(url, ImageSignatureRequest.AddKeyId(url, "https://private.example", key));
    }

    // Rec Room's own metadata does not use the plain v27 header: the four literal-table
    // fields are shuffled into other 32-bit slots, so the reader discovers the layout.
    // This writes the same shape (the 20230831 build puts table offset at 0x74, table
    // size at 0x24, data offset at 0xA0, data size at 0x3C) at 0x100-aligned offsets.
    private static byte[] ShuffledMetadata(params string[] literals)
    {
        // Real metadata files carry tens of thousands of literals; the reader refuses
        // tables that are too small to be one, so the fixture is padded past that floor.
        var padded = literals.Concat(Enumerable.Range(0, 40).Select(i => $"filler literal {i}")).ToArray();
        int tableOffset = 0x100;
        int tableSize = padded.Length * 8;
        int dataOffset = tableOffset + tableSize;
        int dataSize = padded.Sum(s => Encoding.UTF8.GetByteCount(s));
        var file = new byte[dataOffset + dataSize];
        BitConverter.GetBytes(0x2EBE0u).CopyTo(file, 0);
        BitConverter.GetBytes(tableSize).CopyTo(file, 0x24);
        BitConverter.GetBytes(dataSize).CopyTo(file, 0x3C);
        BitConverter.GetBytes(tableOffset).CopyTo(file, 0x74);
        BitConverter.GetBytes(dataOffset).CopyTo(file, 0xA0);
        int index = 0;
        for (int i = 0; i < padded.Length; i++)
        {
            int size = Encoding.UTF8.GetByteCount(padded[i]);
            BitConverter.GetBytes(size).CopyTo(file, tableOffset + 8 * i);
            BitConverter.GetBytes(index).CopyTo(file, tableOffset + 8 * i + 4);
            Encoding.UTF8.GetBytes(padded[i]).CopyTo(file, dataOffset + index);
            index += size;
        }
        return file;
    }

    [Theory]
    [InlineData(".rec.net")]
    [InlineData(".radicade.internal")]
    public void ShuffledHeaderMetadataIsDiscoveredStructurally(string tail)
    {
        var metadata = ShuffledMetadata("https://img.rec.net", tail, "another literal");
        Assert.Equal("KEY:RSA:p1" + tail, ImageSignatureRequest.DetectKeyIdFromGameMetadata(metadata));
        Assert.Equal("KEY:RSA:p1" + tail, ImageSignatureRequest.DetectKeyIdFromGameMetadata(metadata));
        // A plain v27 file keeps working through the same entry point.
        Assert.Equal("KEY:RSA:p1" + tail, ImageSignatureRequest.DetectKeyIdFromGameMetadata(Metadata(tail)));
    }

    [Fact]
    public void ShuffledHeaderAmbiguityAndGarbageStayUndecided()
    {
        Assert.Null(ImageSignatureRequest.DetectKeyIdFromGameMetadata(
            ShuffledMetadata(".rec.net", ".radicade.internal", "x")));
        Assert.Null(ImageSignatureRequest.DetectKeyIdFromGameMetadata(
            ShuffledMetadata("https://img.rec.net", "no key tail here")));
        Assert.Null(ImageSignatureRequest.DetectKeyIdFromGameMetadata(new byte[512]));
        var random = new byte[4096];
        new Random(7).NextBytes(random);
        Assert.Null(ImageSignatureRequest.DetectKeyIdFromGameMetadata(random));
    }

    [Fact]
    public void InvalidOrAmbiguousMetadataDoesNotGuess()
    {
        Assert.Null(ImageSignatureRequest.DetectKeyId(new byte[2]));
        Assert.Null(ImageSignatureRequest.DetectKeyId(Metadata(".rec.net", ".radicade.internal")));
        Assert.Null(ImageSignatureRequest.DetectKeyId(Metadata("https://img.rec.net")));
        var invalid = Metadata(".rec.net");
        Array.Copy(BitConverter.GetBytes(int.MaxValue), 0, invalid, 12, 4);
        Assert.Null(ImageSignatureRequest.DetectKeyId(invalid));
    }

    [Theory]
    [InlineData("https://other.example/images/photo")]
    [InlineData("https://private.example.evil/images/photo")]
    [InlineData("https://private.example/api/photo")]
    [InlineData("http://private.example/images/photo")]
    public void OnlyConfiguredServerImagesReceiveHint(string url)
        => Assert.Equal(url, ImageSignatureRequest.AddKeyId(url, "https://private.example", "KEY:RSA:p1.rec.net"));

    [Fact]
    public void PatchedRouteAndServerBasePathKeepParametersAndReplaceStaleHint()
    {
        var url = ImageSignatureRequest.AddKeyId("https://private.example/base/images/img/photo?rcsig=old&cropSquare=1#f",
            "https://private.example/base/", "KEY:RSA:p1.radicade.internal");
        Assert.Equal("https://private.example/base/images/img/photo?cropSquare=1&rcsig=KEY%3ARSA%3Ap1.radicade.internal#f", url);
    }
}