Fix directory traversal in the HlsSegmentController in a fairly rudimentary but working way.

GHSL-2021-050: Issue 1,2,3 Arbitrary file read and directory traversal.
The segment id's can probably just be verified to be an actual ID or to not contain any forward or backward slashes

1 files changed, 20 insertions, 0 deletions

diff --git a/Jellyfin.Api/Controllers/HlsSegmentController.cs b/Jellyfin.Api/Controllers/HlsSegmentController.cs
index d0ed45acb..5a8542048 100644
--- a/Jellyfin.Api/Controllers/HlsSegmentController.cs
+++ b/Jellyfin.Api/Controllers/HlsSegmentController.cs
@@ -62,6 +62,13 @@ namespace Jellyfin.Api.Controllers
             // TODO: Deprecate with new iOS app
             var file = segmentId + Path.GetExtension(Request.Path);
             file = Path.Combine(_serverConfigurationManager.GetTranscodePath(), file);
+            var transcodePath = _serverConfigurationManager.GetTranscodePath();
+            file = Path.GetFullPath(Path.Combine(transcodePath, file));
+            var fileDir = Path.GetDirectoryName(file);
+            if (string.IsNullOrEmpty(fileDir) || !fileDir.StartsWith(transcodePath))
+            {
+                return BadRequest("Invalid segment.");
+            }
 
             return FileStreamResponseHelpers.GetStaticFileResult(file, MimeTypes.GetMimeType(file)!, false, HttpContext);
         }
@@ -82,6 +89,13 @@ namespace Jellyfin.Api.Controllers
         {
             var file = playlistId + Path.GetExtension(Request.Path);
             file = Path.Combine(_serverConfigurationManager.GetTranscodePath(), file);
+            var transcodePath = _serverConfigurationManager.GetTranscodePath();
+            file = Path.GetFullPath(Path.Combine(transcodePath, file));
+            var fileDir = Path.GetDirectoryName(file);
+            if (string.IsNullOrEmpty(fileDir) || !fileDir.StartsWith(transcodePath) || Path.GetExtension(file) != ".m3u8")
+            {
+                return BadRequest("Invalid segment.");
+            }
 
             return GetFileResult(file, file);
         }
@@ -131,6 +145,12 @@ namespace Jellyfin.Api.Controllers
             var transcodeFolderPath = _serverConfigurationManager.GetTranscodePath();
 
             file = Path.Combine(transcodeFolderPath, file);
+            file = Path.GetFullPath(Path.Combine(transcodeFolderPath, file));
+            var fileDir = Path.GetDirectoryName(file);
+            if (string.IsNullOrEmpty(fileDir) || !fileDir.StartsWith(transcodeFolderPath))
+            {
+                return BadRequest("Invalid segment.");
+            }
 
             var normalizedPlaylistId = playlistId;