[vlc-commits] [Git][videolan/vlc][master] 3 commits: youtube.lua: fix crash on unexpected "n" descrambling transformation code

[David (@dfuhrmann)]

David pushed to branch master at VideoLAN / VLC


Commits:
14944410 by Pierre Ynard at 2022-09-01T20:09:08+00:00
youtube.lua: fix crash on unexpected "n" descrambling transformation code

It was possible, when encountering different code from what was expected
for some known transformations, to void the code parsing pointer instead
of advancing it, resulting in a subsequent crash of the script and total
playback failure. Add a fallback and check, to prevent and gracefully
deal with this, and still allow playback, even if throttled, in case of
descrambling failure.

- - - - -
b735ef2c by Pierre Ynard at 2022-09-01T20:09:08+00:00
youtube.lua: don't silently fail on "n" descrambling script parsing

The descrambling script section was updated from a simple and linear
chain of calls, to a complex execution tree with conditional branches.
Failure to recognize and parse this call structure (or lack thereof)
resulted in a silent no-op. Add a check to properly report an error.

Ref #27227

- - - - -
90dcfa0e by Pierre Ynard at 2022-09-01T20:09:08+00:00
youtube.lua: bump up severity of "n" parameter throttling warning

Due to the severely increased complexity of "n" descrambling code, a
quick fix is unfortunately not foreseeable. For now, let users know more
clearly what's going on and what's to expect or not.

Ref #27227

- - - - -


1 changed file:

- share/lua/playlist/youtube.lua


Changes:

=====================================
share/lua/playlist/youtube.lua
=====================================
@@ -370,7 +370,7 @@ function n_descramble( nparam, js )
     -- as such into a table.
     local data = {}
     datac = datac..","
-    while datac ~= "" do
+    while datac and datac ~= "" do
         local el = nil
         -- Transformation functions
         if string.match( datac, "^function%(" ) then
@@ -396,6 +396,7 @@ function n_descramble( nparam, js )
                el == trans.compound1.func or
                el == trans.compound2.func then
                 datac = string.match( datac, '^.-},e%.split%(""%)%)},(.*)$' )
+                        or string.match( datac, "^.-},(.*)$" )
             else
                 datac = string.match( datac, "^.-},(.*)$" )
             end
@@ -459,6 +460,10 @@ function n_descramble( nparam, js )
     -- as a second argument. We parse and emulate those calls to follow
     -- the descrambling script.
     -- c[40](c[14],c[2]),c[25](c[48]),c[14](c[1],c[24],c[42]()), [...]
+    if not string.match( script, "c%[(%d+)%]%(c%[(%d+)%]([^)]-)%)" ) then
+        vlc.msg.dbg( "Couldn't parse and execute YouTube video throttling parameter descrambling rules" )
+        return nil
+    end
     for ifunc, itab, args in string.gmatch( script, "c%[(%d+)%]%(c%[(%d+)%]([^)]-)%)" ) do
         local iarg1 = string.match( args, "^,c%[(%d+)%]" )
         local iarg2 = string.match( args, "^,[^,]-,c%[(%d+)%]" )
@@ -703,8 +708,8 @@ function pick_stream( stream_map, js_url )
         if dn then
             url = string.gsub( url, "([?&])n=[^&]+", "%1n="..vlc.strings.encode_uri_component( dn ), 1 )
         else
-            vlc.msg.dbg( "Couldn't descramble YouTube throttling URL parameter: data transfer will get throttled" )
-            vlc.msg.err( "Couldn't process youtube video URL, please check for updates to this script" )
+            vlc.msg.err( "Couldn't descramble YouTube throttling URL parameter: data transfer will get throttled" )
+            --vlc.msg.err( "Couldn't process youtube video URL, please check for updates to this script" )
         end
     end
 



View it on GitLab: https://code.videolan.org/videolan/vlc/-/compare/49ff728d48005aac6d87ecfb8f8114fe07dedd51...90dcfa0e78081770ecbd0a072b96a277aea4a214

-- 
View it on GitLab: https://code.videolan.org/videolan/vlc/-/compare/49ff728d48005aac6d87ecfb8f8114fe07dedd51...90dcfa0e78081770ecbd0a072b96a277aea4a214
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