libbzip2 - BZ2_bzBuffToBuffDecompress issue

["Zorn, Nicholas - 0991 - MITLL" <zorn@ll.mit.edu>]

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Hello bzip2 developers,

I believe I found a potential issue inside the convenience function
BZ_API(BZ2_bzBuffToBuffDecompress).

If the size of the buffer allocated to receive the decompressed data is
bigger than the uncompressed data (which is completely normal/expected,
given you likely do not know how big the decompressed data will be), one can
never receive BZ_OK as a return value – one will only ever get
BZ_UNEXPECTED_EOF. But more importantly, the destLen value will not be
updated, making the returned data essentially unusable.

So I made some minor modifications to the code (starting at line 1337 in
bzlib.c), commented below. I have been using it continuously and without
error inside an application for over a year.

   output_overflow_or_eof:
   if (strm.avail_out > 0) {
       *destLen -= strm.avail_out; // NVZ added this line 08 Nov 2018
       BZ2_bzDecompressEnd ( &strm );
       return BZ_OK; // NVZ changed this return value from BZ_UNEXPECTED_EOF
on 08 Nov 2018
   } else {
      BZ2_bzDecompressEnd ( &strm );
      return BZ_OUTBUFF_FULL;
   };

Feel free to ignore or shut this down. Otherwise, I hope I may have been
able to identify an area for potential improvement in a great library. It’s
also nice to see people picking up the torch and continuing to support it.

Thank you.
-------------------------------------------
Nick V. Zorn
Technical Staff
MIT Lincoln Laboratory
-------------------------------------------


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