Libwebp Alternatives

libwebp reviews and mentions

• Google assigns a CVE for libwebp and gives it a 10.0 score
  5 projects | news.ycombinator.com | 26 Sep 2023

  The thing that concerns me most is looking at the fix it is very difficult to see why this fix is correct. It also appears as there is lots of code without explicit bounds checks. It makes me worried because while the logic may be safe this makes the logic very complex. I wonder what the cost would be to add an explicit, local bounds check at every array access. This would serve as a backup that is much easier to verify. I suspect the cost would be relatively small. Small enough that I personally would be happy to pay it.

  https://github.com/webmproject/libwebp/commit/902bc919033134...

  This is also a great reminded that fuzzing isn't a solution to memory unsafe languages and libraries. If anything the massive amount of bugs found via fuzzing should scare us as it is likely only scratching the surface of the vulnerabilities that still lie in the code, a couple too many branches away from being likely to be found by fuzzing.

• The WebP 0day
  6 projects | news.ycombinator.com | 21 Sep 2023

  Millions of people in the world are affected by this library. There is a call for libraries used by millions around the world to NOT use C. I love C. But this risk ratio is off the charts and they ought to not use C for such critical libraries.

  I think this is the fix https://github.com/webmproject/libwebp/commit/dce8397fec159c...

  "malloc fail"? :facepalm:

  6 projects | news.ycombinator.com | 21 Sep 2023

  There's a follow-up fix, according to Debian[0]: https://github.com/webmproject/libwebp/commit/95ea5226c87044...

  [0]: https://security-tracker.debian.org/tracker/CVE-2023-4863

  6 projects | news.ycombinator.com | 21 Sep 2023

  This is the fix: https://github.com/webmproject/libwebp/commit/902bc919033134...

• CVE-2023-4863: Heap buffer overflow in WebP (Chrome)
  18 projects | news.ycombinator.com | 12 Sep 2023

  https://github.com/webmproject/libwebp/commit/95ea5226c87044...

  This could mean Google optimized their fuzzers for libwebp after finding that bug and now they're finding more.

  18 projects | news.ycombinator.com | 12 Sep 2023

  It's 2023, surely this is not yet another bug related to memory unsafety that could be avoided if we'd stop writing critical code that deals with extremely complex untrusted input (media codecs) in memory unsafe languages?

  Yep, of course it is: https://github.com/webmproject/libwebp/commit/902bc919033134...

  I guess libwebp could be excused as it was started when there were no alternatives, but even for new projects today we're still committing the same mistake[1][2][3].

  [1] -- https://code.videolan.org/videolan/dav1d

  [2] -- https://github.com/AOMediaCodec/libavif

  [3] -- https://github.com/AOMediaCodec/libiamf

  Yep. Keep writing these in C; surely nothing will go wrong.

  18 projects | news.ycombinator.com | 12 Sep 2023

  The breakage [0] was introduced by the creator [1] of the project. If you want to audit 1674 commits over the past 12 years, it'd be easier to just audit the full project.

  [0] https://github.com/webmproject/libwebp/commit/21735e06f7c1cb...

  [1] https://github.com/webmproject/libwebp/commit/c3f41cb47e5f32...

  18 projects | news.ycombinator.com | 12 Sep 2023

  The original commit in question: https://github.com/webmproject/libwebp/commit/f75dfbf23d1df1...

  The commit that fixes this bug: https://github.com/webmproject/libwebp/commit/902bc919033134...

  The original commit optimizes a Huffman decoder. The decoder uses a well-known optimization: it reads N bits in advance and determines how many bits have to be actually consumed and which symbol should be decoded, or, if it's an N-bit prefix of multiple symbols, which table should be consulted for remaining bits.

  The old version did use lookup tables for short symbols, but longer symbols needed a graph traversal. The new version improved this by using an array of lookup tables. Each entry contains (nbits, value) where `nbits` is # bits to be consumed and `value` is normally a symbol, but if `nbits` exceeds N `value` is interpreted as a table index and `nbits` is reinterpreted as the longest code length in that subtree. So each subsequent table should have `2^(nbits - N)` entries (the root table is always fixed to 2^N entries).

  The new version calculated the maximum number of entries based on the number of symbols (kTableSize). Of course, the Huffman tree comes from an untrusted source and you can easily imagine the case where `nbits` is very big. VP8 Lossless specifically allows up to 15 bits, so the largest possible table has 2^N + 2^15 entries when every single LUT is mapped to its own secondary table, and doing this doesn't need that many symbols (you only need 16-N symbols for each table). So if the Huffman tree was crafted in the way that maximizes the number of entries, it will overflow the allocation.

  To be fair, I can see why this happened; the Huffman decoding step is one of the most computationally intensive part of many compression format and any small improvement matters. The Huffman decoder optimization described above is well known, but the longer code case is commonly considered less important to optimize because longer code should rarely appear in general. The original commit message refuted this, and was able to be merged.

  18 projects | news.ycombinator.com | 12 Sep 2023
• Convenient CPU feature detection and dispatch in the Magnum Engine
  9 projects | /r/cpp | 2 Aug 2022
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