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The AES code uses av_aes_block, a union consisting of uint64_t[2], uint32_t[4], uint8_t[4][4] and uint8_t[16]. subshift() performs byte-wise manipulations of two av_aes_blocks, but when encrypting, it does so with a shift of two bytes; more precisely, it uses "av_aes_block *s1 = (av_aes_block *) (s0[0].u8 - s)" and lateron uses the uint8_t[16] member to access s0. Yet av_aes_block requires to be suitably aligned for the uint64_t[2] member, which s0[0].u8 - 2 is certainly not. This is in violation of 6.3.2.3 (7) of C11. UBSan reports this in the aes_ctr, mov-3elist-encrypted, mov-frag-encrypted, mov-tenc-only-encrypted and srtp tests. Furthermore, there is another issue here: The pointer points outside of s0; this works, because all the accesses lateron use an index >= 3. (Clang-)UBSan reports this as "runtime error: index -2 out of bounds for type 'uint8_t[16]'". This commit fixes both of these issues: The latter issue is fixed by applying an offset of "+ 3" during the cast and subtracting this from the indices used lateron. The former issue is solved by not casting to av_aes_block* at all; instead simply cast to unsigned char*. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
FFmpeg README
FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.
Libraries
libavcodecprovides implementation of a wider range of codecs.libavformatimplements streaming protocols, container formats and basic I/O access.libavutilincludes hashers, decompressors and miscellaneous utility functions.libavfilterprovides means to alter decoded audio and video through a directed graph of connected filters.libavdeviceprovides an abstraction to access capture and playback devices.libswresampleimplements audio mixing and resampling routines.libswscaleimplements color conversion and scaling routines.
Tools
- ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
- ffplay is a minimalistic multimedia player.
- ffprobe is a simple analysis tool to inspect multimedia content.
- Additional small tools such as
aviocat,ismindexandqt-faststart.
Documentation
The offline documentation is available in the doc/ directory.
The online documentation is available in the main website and in the wiki.
Examples
Coding examples are available in the doc/examples directory.
License
FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.
Contributing
Patches should be submitted to the ffmpeg-devel mailing list using
git format-patch or git send-email. Github pull requests should be
avoided because they are not part of our review process and will be ignored.