added URL's "n" parameter scrambler

More info : https://code.videolan.org/videolan/vlc/-/issues/26174#note_286445 ytdl-org/youtube-dl#29326
omansak · Nov 4, 2021 · 3d7374d · 3d7374d
1 parent 703a835
commit 3d7374d
Show file tree

Hide file tree

Showing 9 changed files with 85 additions and 4 deletions.
diff --git a/YoutubeExplode/Bridge/Extractors/DashStreamInfoExtractor.cs b/YoutubeExplode/Bridge/Extractors/DashStreamInfoExtractor.cs
@@ -23,6 +23,8 @@ internal class DashStreamInfoExtractor : IStreamInfoExtractor
 
         // DASH streams don't have signatures
         public string? TryGetSignature() => null;
+        public string? TryGetNSignature() => _memo.Wrap(() => TryGetUrl()?
+            .Pipe(s => Regex.Match(s, @"[\?&]n=(.*?)&").Groups[1].Value));
 
         // DASH streams don't have signatures
         public string? TryGetSignatureParameter() => null;

diff --git a/YoutubeExplode/Bridge/Extractors/IStreamInfoExtractor.cs b/YoutubeExplode/Bridge/Extractors/IStreamInfoExtractor.cs
@@ -8,6 +8,8 @@ internal interface IStreamInfoExtractor
 
         string? TryGetSignature();
 
+        string? TryGetNSignature();
+
         string? TryGetSignatureParameter();
 
         long? TryGetContentLength();
@@ -27,5 +29,6 @@ internal interface IStreamInfoExtractor
         int? TryGetVideoHeight();
 
         int? TryGetFramerate();
+
     }
 }
diff --git a/YoutubeExplode/Bridge/Extractors/PlayerSourceExtractor.cs b/YoutubeExplode/Bridge/Extractors/PlayerSourceExtractor.cs
@@ -88,6 +88,25 @@ internal partial class PlayerSourceExtractor
 
             return new SignatureScrambler(operations);
         });
+
+        public string? TryNScramblerFunction() => _memo.Wrap(() =>
+        {
+            var functionNameRegex = new Regex(@"\.get\(\""n\""\)\)&&\(\w=([a-zA-Z0-9$]{3})\([a-zA-Z0-9]\)");
+            var functionNameRegexMatch = functionNameRegex.Match(_content);
+            if (functionNameRegexMatch.Success)
+            {
+                var unscrambleFunctionName = functionNameRegexMatch.Groups[1].Value;
+                var functionRegexMatchStart = Regex.Match(_content, unscrambleFunctionName + @"=function\((\w)\){var\s+\w=\1.split\(\x22{2}\),\w=");
+                var functionRegexMatchEnd = Regex.Match(_content, @"\+a}return\s\w.join\(\x22{2}\)};");
+
+                if (functionRegexMatchStart.Success && functionRegexMatchEnd.Success)
+                {
+                    return "var " + _content.Substring(functionRegexMatchStart.Index, (functionRegexMatchEnd.Index + functionRegexMatchEnd.Length) - functionRegexMatchStart.Index);
+                }
+            }
+
+            return null;
+        });
     }
 
     internal partial class PlayerSourceExtractor

diff --git a/YoutubeExplode/Bridge/Extractors/PlayerStreamInfoExtractor.cs b/YoutubeExplode/Bridge/Extractors/PlayerStreamInfoExtractor.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Net;
 using System.Text.Json;
 using System.Text.RegularExpressions;
 using YoutubeExplode.Utils;
@@ -44,6 +45,9 @@ internal class PlayerStreamInfoExtractor : IStreamInfoExtractor
             TryGetCipherData()?.GetValueOrDefault("s")
         );
 
+        public string? TryGetNSignature() => _memo.Wrap(() => TryGetUrl()?
+            .Pipe(s => Regex.Match(s, @"[\?&]n=(.*?)&").Groups[1].Value));
+
         public string? TryGetSignatureParameter() => _memo.Wrap(() =>
             TryGetCipherData()?.GetValueOrDefault("sp")
         );

diff --git a/YoutubeExplode/Bridge/Extractors/UrlEncodedStreamInfoExtractor.cs b/YoutubeExplode/Bridge/Extractors/UrlEncodedStreamInfoExtractor.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Net;
 using System.Text.RegularExpressions;
 using YoutubeExplode.Utils;
 using YoutubeExplode.Utils.Extensions;
@@ -26,6 +27,9 @@ internal class UrlEncodedStreamInfoExtractor : IStreamInfoExtractor
             _content.GetValueOrDefault("s")
         );
 
+        public string? TryGetNSignature() => _memo.Wrap(() => TryGetUrl()?
+            .Pipe(s => Regex.Match(s, @"[\?&]n=(.*?)&").Groups[1].Value));
+
         public string? TryGetSignatureParameter() => _memo.Wrap(() =>
             _content.GetValueOrDefault("sp")
         );

diff --git a/YoutubeExplode/Bridge/SignatureScrambling/NSignatureScrambler.cs b/YoutubeExplode/Bridge/SignatureScrambling/NSignatureScrambler.cs
@@ -0,0 +1,24 @@
+using NiL.JS.BaseLibrary;
+using NiL.JS.Core;
+using NiL.JS.Extensions;
+using System.Text.RegularExpressions;
+
+namespace YoutubeExplode.Bridge.SignatureScrambling
+{
+    internal class NSignatureScrambler
+    {
+        public string? Unscramble(string jsFunction, string input) => UnscrambleNSignature(jsFunction, input);
+
+        private string? UnscrambleNSignature(string jsFunction, string signature)
+        {
+            var functionNameRegex = Regex.Match(jsFunction, @"var\s(\w*)=");
+            if (!string.IsNullOrWhiteSpace(jsFunction) && functionNameRegex.Success)
+            {
+                var context = new Context();
+                context.Eval(jsFunction);
+                return context.GetVariable(functionNameRegex.Groups[1].Value).As<Function>().Call(new Arguments { signature }).Value.ToString();
+            }
+            return signature;
+        }
+    }
+}
diff --git a/YoutubeExplode/Utils/Url.cs b/YoutubeExplode/Utils/Url.cs
@@ -8,9 +8,10 @@ namespace YoutubeExplode.Utils
 {
     internal static class Url
     {
-        public static string SetQueryParameter(string url, string key, string value)
+        public static string SetQueryParameter(string url, string key, string value, bool forceEqual = false)
         {
-            var existingMatch = Regex.Match(url, $"[?&]({Regex.Escape(key)}=?.*?)(?:&|/|$)");
+            // bug if key is "n", returns "ns" not "n"
+            var existingMatch = Regex.Match(url, $"[?&]({Regex.Escape(key)}={(forceEqual ? "?" : string.Empty)}.*?)(?:&|/|$)");
 
             // Parameter has already been set to something
             if (existingMatch.Success)

diff --git a/YoutubeExplode/Videos/Streams/StreamClient.cs b/YoutubeExplode/Videos/Streams/StreamClient.cs
@@ -46,7 +46,23 @@ public StreamClient(HttpClient httpClient)
             return Url.SetQueryParameter(
                 streamUrl,
                 signatureParameter ?? "signature",
-                signatureScrambler.Unscramble(signature)
+                signatureScrambler.Unscramble(signature),
+                true
+            );
+        }
+
+        private string UnscrambleNSignatureStreamUrl(
+            string streamUrl,
+            string? signature,
+            string? jsFunction)
+        {
+            if (string.IsNullOrWhiteSpace(signature) || string.IsNullOrWhiteSpace(jsFunction))
+                return streamUrl;
+
+            return Url.SetQueryParameter(
+                streamUrl,
+                "n",
+                new NSignatureScrambler().Unscramble(jsFunction, signature) ?? signature
             );
         }
 
@@ -69,6 +85,7 @@ public StreamClient(HttpClient httpClient)
             ICollection<IStreamInfo> streamInfos,
             IEnumerable<IStreamInfoExtractor> streamInfoExtractors,
             SignatureScrambler signatureScrambler,
+            string? nSignatureScramblerFunction,
             CancellationToken cancellationToken = default)
         {
             foreach (var streamInfoExtractor in streamInfoExtractors)
@@ -85,6 +102,8 @@ public StreamClient(HttpClient httpClient)
                 var signature = streamInfoExtractor.TryGetSignature();
                 var signatureParameter = streamInfoExtractor.TryGetSignatureParameter();
                 var url = UnscrambleStreamUrl(signatureScrambler, urlRaw, signature, signatureParameter);
+                // Unscramble N Signature URL
+                url = UnscrambleNSignatureStreamUrl(url, streamInfoExtractor.TryGetNSignature(), nSignatureScramblerFunction);
 
                 // Get content length
                 var contentLength =
@@ -192,6 +211,7 @@ public StreamClient(HttpClient httpClient)
                 : null;
 
             var signatureScrambler = playerSource?.TryGetSignatureScrambler() ?? SignatureScrambler.Null;
+            var nSignatureScrambler = playerSource?.TryNScramblerFunction();
 
             var playerResponseFromWatchPage = watchPage.TryGetPlayerResponse();
             if (playerResponseFromWatchPage is not null)
@@ -212,6 +232,7 @@ public StreamClient(HttpClient httpClient)
                         streamInfos,
                         watchPage.GetStreams(),
                         signatureScrambler,
+                        nSignatureScrambler,
                         cancellationToken
                     );
 
@@ -220,6 +241,7 @@ public StreamClient(HttpClient httpClient)
                         streamInfos,
                         playerResponseFromWatchPage.GetStreams(),
                         signatureScrambler,
+                        nSignatureScrambler,
                         cancellationToken
                     );
 
@@ -234,6 +256,7 @@ public StreamClient(HttpClient httpClient)
                             streamInfos,
                             dashManifest.GetStreams(),
                             signatureScrambler,
+                            nSignatureScrambler,
                             cancellationToken
                         );
                     }
@@ -311,7 +334,7 @@ public StreamClient(HttpClient httpClient)
 
             var segmentSize = isThrottled
                 ? 9_898_989 // breakpoint after which the throttling kicks in
-                : (long?) null; // no segmentation for non-throttled streams
+                : (long?)null; // no segmentation for non-throttled streams
 
             var stream = new SegmentedHttpStream(
                 _httpClient,

diff --git a/YoutubeExplode/YoutubeExplode.csproj b/YoutubeExplode/YoutubeExplode.csproj
@@ -13,6 +13,7 @@
   <ItemGroup>
     <PackageReference Include="AngleSharp" Version="0.14.0" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="all" />
+    <PackageReference Include="NiL.JS" Version="2.5.1514" />
     <PackageReference Include="Nullable" Version="1.3.0" PrivateAssets="all" />
   </ItemGroup>