[CHANGE] Added old cipher implementation

Manager.YouTube/Models/Innertube/ClientState.cs

@@ -35,6 +35,9 @@ public class ClientState : AdditionalJsonData
     [JsonPropertyName("SERVER_VERSION")]
     public string? ServerVersion { get; set; }
 
+    [JsonPropertyName("PLAYER_JS_URL")]
+    public string? PlayerJsUrl { get; set; }
+
     [JsonPropertyName("INNERTUBE_CONTEXT")]
     public InnerTubeContext? InnerTubeContext { get; set; }
 

Manager.YouTube/Util/Cipher/CipherDecoder.cs

@@ -0,0 +1,90 @@
+using System.Text;
+using System.Text.RegularExpressions;
+using Manager.YouTube.Util.Cipher.Operations;
+
+namespace Manager.YouTube.Util.Cipher;
+
+public partial class CipherDecoder
+{
+    public required string Version { get; init; }
+    public required string OriginalRelativeUrl { get; init; }
+    public readonly IReadOnlyCollection<ICipherOperation> Operations;
+
+    private CipherDecoder(IEnumerable<ICipherOperation> operations)
+    {
+        Operations = operations.ToList();
+        if (Operations.Count == 0)
+        {
+            throw new ArgumentNullException(nameof(operations), "No decipher operations given.");
+        }
+    }
+
+    public static async Task<CipherDecoder> CreateAsync(string relativeUrl, string version, YouTubeClient? client = null)
+    {
+        var operations = await GetCipherOperations(relativeUrl, client);
+        var decoder = new CipherDecoder(operations)
+        {
+            OriginalRelativeUrl = relativeUrl,
+            Version = version
+        };
+        return decoder;
+    }
+
+    private static async Task<IEnumerable<ICipherOperation>> GetCipherOperations(string relativeUrl, YouTubeClient? client = null)
+    {
+        var downloadRequest = new HttpRequestMessage(HttpMethod.Get, new Uri($"{NetworkService.Origin}/{relativeUrl}"));
+        var downloadResponse = await NetworkService.DownloadBytesAsync(downloadRequest, client);
+        if (!downloadResponse.IsSuccess)
+        {
+            return [];
+        }
+
+        var playerJs = Encoding.UTF8.GetString(downloadResponse.Value.Data);
+        if (string.IsNullOrWhiteSpace(playerJs))
+        {
+            return [];
+        }
+        
+        var functionBody = FunctionBodyRegex().Match(playerJs).Groups[0].ToString();
+        var definitionBody = DefinitionBodyRegex().Match(functionBody).Groups[1].Value;
+        var decipherDefinition = Regex.Match(playerJs, $@"var\s+{definitionBody}=\{{(\w+:function\(\w+(,\w+)?\)\{{(.*?)\}}),?\}};", RegexOptions.Singleline).Groups[0].ToString();
+
+        List<ICipherOperation> operations = [];
+        foreach (var statement in functionBody.Split(';'))
+        {
+            // Get the name of the function called in this statement
+            var calledFuncName = StatementFunctionNameRegex().Match(statement).Groups[1].Value;
+            if (string.IsNullOrWhiteSpace(calledFuncName))
+                continue;
+
+            if (Regex.IsMatch(decipherDefinition, $@"{Regex.Escape(calledFuncName)}:\bfunction\b\([a],b\).(\breturn\b)?.?\w+\."))
+            {
+                var index = int.Parse(OperationIndexRegex().Match(statement).Groups[1].Value);
+                operations.Add(new CipherSlice(index));
+            }
+            else if (Regex.IsMatch(decipherDefinition, $@"{Regex.Escape(calledFuncName)}:\bfunction\b\(\w+\,\w\).\bvar\b.\bc=a\b"))
+            {
+                var index = int.Parse(OperationIndexRegex().Match(statement).Groups[1].Value);
+                operations.Add(new CipherSwap(index));
+            }
+            else if (Regex.IsMatch(decipherDefinition, $@"{Regex.Escape(calledFuncName)}:\bfunction\b\(\w+\)"))
+            {
+                operations.Add(new CipherReverse());
+            }
+        }
+
+        return [];
+    }
+
+    
+    [GeneratedRegex(@"(\w+)=function\(\w+\){(\w+)=\2\.split\(\x22{2}\);.*?return\s+\2\.join\(\x22{2}\)}")]
+    private static partial Regex FunctionBodyRegex();
+    [GeneratedRegex("([\\$_\\w]+).\\w+\\(\\w+,\\d+\\);")]
+    private static partial Regex DefinitionBodyRegex();
+    
+    
+    [GeneratedRegex(@"\(\w+,(\d+)\)")]
+    private static partial Regex OperationIndexRegex();
+    [GeneratedRegex(@"\w+(?:.|\[)(\""?\w+(?:\"")?)\]?\(")]
+    private static partial Regex StatementFunctionNameRegex();
+}

Manager.YouTube/Util/Cipher/CipherDecoderCollection.cs

@@ -0,0 +1,11 @@
+using System.Collections.ObjectModel;
+
+namespace Manager.YouTube.Util.Cipher;
+
+public class CipherDecoderCollection : KeyedCollection<string, CipherDecoder>
+{
+    protected override string GetKeyForItem(CipherDecoder item)
+    {
+        return item.Version;
+    }
+}

Manager.YouTube/Util/Cipher/CipherManager.cs

@@ -0,0 +1,46 @@
+using DotBased.Logging;
+using DotBased.Monads;
+
+namespace Manager.YouTube.Util.Cipher;
+
+public static class CipherManager
+{
+    private static readonly CipherDecoderCollection LoadedCiphers = [];
+    private static readonly ILogger Logger = LogService.RegisterLogger(typeof(CipherManager));
+
+    public static async Task<Result<CipherDecoder>> GetDecoder(YouTubeClient client)
+    {
+        var relativePlayerJsUrl = client.State?.PlayerJsUrl;
+        if (string.IsNullOrEmpty(relativePlayerJsUrl))
+        {
+            return ResultError.Fail("Could not get player js url.");
+        }
+        var version = GetCipherVersion(relativePlayerJsUrl);
+
+        Logger.Debug($"Getting cipher decoder for version: {version}");
+        if (LoadedCiphers.TryGetValue(version, out var cipher))
+        {
+            return cipher;
+        }
+        
+        try
+        {
+            var decoder = await CipherDecoder.CreateAsync(relativePlayerJsUrl, version);
+            LoadedCiphers.Add(decoder);
+        }
+        catch (Exception e)
+        {
+            Logger.Error(e, "Could not create cipher decoder. Version: {DecoderVersion}", version);
+        }
+        
+        return ResultError.Fail($"Could not create cipher decoder for {relativePlayerJsUrl} (v: {version})");
+    }
+
+    private static string GetCipherVersion(string relativePlayerUrl)
+    {
+        var split = relativePlayerUrl.Split('/');
+        var v = split[2];
+        var lang = split[4];
+        return $"{v}_{lang}";
+    }
+}

Manager.YouTube/Util/Cipher/Operations/CipherReverse.cs

@@ -0,0 +1,18 @@
+using System.Text;
+
+namespace Manager.YouTube.Util.Cipher.Operations;
+
+public class CipherReverse : ICipherOperation
+{
+    public string Decipher(string cipherSignature)
+    {
+        var buffer = new StringBuilder(cipherSignature.Length);
+
+        for (var i = cipherSignature.Length - 1; i >= 0; i--)
+        {
+            buffer.Append(cipherSignature[i]);
+        }
+
+        return buffer.ToString();
+    }
+}

Manager.YouTube/Util/Cipher/Operations/CipherSlice.cs

@@ -0,0 +1,6 @@
+namespace Manager.YouTube.Util.Cipher.Operations;
+
+public class CipherSlice(int indexToSlice) : ICipherOperation
+{
+    public string Decipher(string cipherSignature) => cipherSignature[indexToSlice..];
+}

Manager.YouTube/Util/Cipher/Operations/CipherSwap.cs

@@ -0,0 +1,12 @@
+using System.Text;
+
+namespace Manager.YouTube.Util.Cipher.Operations;
+
+public class CipherSwap(int indexToSwap) : ICipherOperation
+{
+    public string Decipher(string cipherSignature) => new StringBuilder(cipherSignature)
+    {
+        [0] = cipherSignature[indexToSwap],
+        [indexToSwap] = cipherSignature[0]
+    }.ToString();
+}

Manager.YouTube/Util/Cipher/Operations/ICipherOperation.cs

@@ -0,0 +1,6 @@
+namespace Manager.YouTube.Util.Cipher.Operations;
+
+public interface ICipherOperation
+{
+    string Decipher(string cipherSignature);
+}