This function was creating a lot of new pointers and strings without
properly checking the array bounds. This commit adds several calls
to enforce(), making sure that the pointers stay within bounds.
Strings are now created using the helper function
string_from_unterminated() to prevent overreads in the constructor of
std::string.
This fixes#400
This commit fixes the heap-buffer-overflow in PngChunk::parseTXTChunk.
According to the specification:
http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html
There must be 2 null separators when we start to analyze the language tag.
- cdataBuf must be at least 8 bytes long otherwise decodeIHDRChunk
reads out of bounds
- pngImage::readMetadata now skips png chunks where the offset for
IHDR chunks is invalid
- added assertion into PngChunk::decodeIHDRChunk() to ensure dataBuf
size
- consider that key is advanced by 8 bytes if stripHeader is true
=> length is reduced by same amount
Fixed by adding offset to the check in the loop
- Rewrote loop so that keysize is checked before the next
iteration (preventing an out of bounds read)
