Decipher signatures only if they require it

Author: flagbug

YoutubeExtractor/YoutubeExtractor/DownloadUrlResolver.cs

@@ -45,6 +45,7 @@ public static void DecryptDownloadUrl(VideoInfo videoInfo)
                 }
 
                 videoInfo.DownloadUrl = HttpHelper.ReplaceQueryStringParameter(videoInfo.DownloadUrl, SignatureQuery, decrypted);
+                videoInfo.RequiresDecryption = false;
             }
         }
 
@@ -88,7 +89,7 @@ public static IEnumerable<VideoInfo> GetDownloadUrls(string videoUrl, bool decry
 
                 string videoTitle = GetVideoTitle(json);
 
-                IEnumerable<Uri> downloadUrls = ExtractDownloadUrls(json);
+                IEnumerable<ExtractionInfo> downloadUrls = ExtractDownloadUrls(json);
 
                 IEnumerable<VideoInfo> infos = GetVideoInfos(downloadUrls, videoTitle).ToList();
 
@@ -98,7 +99,7 @@ public static IEnumerable<VideoInfo> GetDownloadUrls(string videoUrl, bool decry
                 {
                     info.HtmlPlayerVersion = htmlPlayerVersion;
 
-                    if (decryptSignature)
+                    if (decryptSignature && info.RequiresDecryption)
                     {
                         DecryptDownloadUrl(info);
                     }
@@ -168,7 +169,7 @@ public static bool TryNormalizeYoutubeUrl(string url, out string normalizedUrl)
             return true;
         }
 
-        private static IEnumerable<Uri> ExtractDownloadUrls(JObject json)
+        private static IEnumerable<ExtractionInfo> ExtractDownloadUrls(JObject json)
         {
             string[] splitByUrls = GetStreamMap(json).Split(',');
             string[] adaptiveFmtSplitByUrls = GetAdaptiveStreamMap(json).Split(',');
@@ -179,8 +180,11 @@ private static IEnumerable<Uri> ExtractDownloadUrls(JObject json)
                 IDictionary<string, string> queries = HttpHelper.ParseQueryString(s);
                 string url;
 
+                bool requiresDecryption = false;
+
                 if (queries.ContainsKey("s") || queries.ContainsKey("sig"))
                 {
+                    requiresDecryption = queries.ContainsKey("s");
                     string signature = queries.ContainsKey("s") ? queries["s"] : queries["sig"];
 
                     url = string.Format("{0}&{1}={2}", queries["url"], SignatureQuery, signature);
@@ -198,7 +202,7 @@ private static IEnumerable<Uri> ExtractDownloadUrls(JObject json)
                 url = HttpHelper.UrlDecode(url);
                 url = HttpHelper.UrlDecode(url);
 
-                yield return new Uri(url);
+                yield return new ExtractionInfo { RequiresDecryption = requiresDecryption, Uri = new Uri(url) };
             }
         }
 
@@ -242,13 +246,13 @@ private static string GetStreamMap(JObject json)
             return streamMapString;
         }
 
-        private static IEnumerable<VideoInfo> GetVideoInfos(IEnumerable<Uri> downloadUrls, string videoTitle)
+        private static IEnumerable<VideoInfo> GetVideoInfos(IEnumerable<ExtractionInfo> extractionInfos, string videoTitle)
         {
             var downLoadInfos = new List<VideoInfo>();
 
-            foreach (Uri url in downloadUrls)
+            foreach (ExtractionInfo extractionInfo in extractionInfos)
             {
-                string itag = HttpHelper.ParseQueryString(url.Query)["itag"];
+                string itag = HttpHelper.ParseQueryString(extractionInfo.Uri.Query)["itag"];
 
                 int formatCode = int.Parse(itag);
 
@@ -258,16 +262,17 @@ private static IEnumerable<VideoInfo> GetVideoInfos(IEnumerable<Uri> downloadUrl
                 {
                     info = new VideoInfo(info)
                     {
-                        DownloadUrl = url.ToString(),
-                        Title = videoTitle
+                        DownloadUrl = extractionInfo.Uri.ToString(),
+                        Title = videoTitle,
+                        RequiresDecryption = extractionInfo.RequiresDecryption
                     };
                 }
 
                 else
                 {
                     info = new VideoInfo(formatCode)
                     {
-                        DownloadUrl = url.ToString()
+                        DownloadUrl = extractionInfo.Uri.ToString()
                     };
                 }
 
@@ -313,5 +318,12 @@ private static void ThrowYoutubeParseException(Exception innerException)
                                             "This may be due to a change of the Youtube page structure.\n" +
                                             "Please report this bug at www.github.com/flagbug/YoutubeExtractor/issues", innerException);
         }
+
+        private class ExtractionInfo
+        {
+            public bool RequiresDecryption { get; set; }
+
+            public Uri Uri { get; set; }
+        }
     }
 }

YoutubeExtractor/YoutubeExtractor/VideoInfo.cs

@@ -134,6 +134,14 @@ public bool CanExtractAudio
 
         public bool Is3D { get; private set; }
 
+        /// <summary>
+        /// Gets a value indicating whether this video info requires a signature decryption before
+        /// the download URL can be used.
+        ///
+        /// This can be achieved with the <see cref="DownloadUrlResolver.DecryptDownloadUrl"/>
+        /// </summary>
+        public bool RequiresDecryption { get; internal set; }
+
         /// <summary>
         /// Gets the resolution of the video.
         /// </summary>