hlsdemux: Implement pkcs7 unpadding

Every encrypted fragment will be a multiple of 128 bits, the last byte
contains the number of bytes that were added as padding in the end
and should be removed.

https://bugzilla.gnome.org/show_bug.cgi?id=701673

1 files changed, 7 insertions, 0 deletions

diff --git a/ext/hls/gsthlsdemux.c b/ext/hls/gsthlsdemux.c
index ec9b25ae4..2dfb8560a 100644
--- a/ext/hls/gsthlsdemux.c
+++ b/ext/hls/gsthlsdemux.c
@@ -1243,6 +1243,7 @@ gst_hls_demux_decrypt_fragment (GstHLSDemux * demux,
   GstMapInfo key_info, encrypted_info, decrypted_info;
   gnutls_cipher_hd_t aes_ctx;
   gnutls_datum_t key_d, iv_d;
+  gsize unpadded_size;
 
   GST_INFO_OBJECT (demux, "Fetching key %s", key);
   key_fragment = gst_uri_downloader_fetch_uri (demux->downloader, key);
@@ -1269,10 +1270,16 @@ gst_hls_demux_decrypt_fragment (GstHLSDemux * demux,
       decrypted_info.data, decrypted_info.size);
   gnutls_cipher_deinit (aes_ctx);
 
+  /* Handle pkcs7 unpadding here */
+  unpadded_size =
+      decrypted_info.size - decrypted_info.data[decrypted_info.size - 1];
+
   gst_buffer_unmap (decrypted_buffer, &decrypted_info);
   gst_buffer_unmap (encrypted_buffer, &encrypted_info);
   gst_buffer_unmap (key_buffer, &key_info);
 
+  gst_buffer_resize (decrypted_buffer, 0, unpadded_size);
+
   gst_buffer_unref (key_buffer);
   gst_buffer_unref (encrypted_buffer);
   g_object_unref (key_fragment);