The previous releases of zlib were not sensitive to incorrect CRC
inputs with bits set above the low 32. This commit restores that
behavior, so that applications with such bugs will continue to
operate as before.
The issue is that unztell64() does not return the correct value if
the position in the current file (in the ZIP archive) is beyond 4
GB. The cause is that unzReadCurrentFile() does not account for
pfile_in_zip_read_info->stream.total_out at line 1854 of unzip.c
wrapping around (it is a 32-bit variable). So, on line 1860
uTotalOutAfter can be *less* than uTotalOutBefore, propagating the
wraparound to uOutThis, which in turn is added to
pfile_in_zip_read_info->total_out_64. That has the effect of
subtracting 4 GB.
The ARM crc32 instructions will be used only if an architecture is
explicitly specified at compile time that has those instructions.
For example, -march=armv8.1-a or -march=armv8-a+crc, or if the
machine being compiled on has the instructions, -march=native.
Define the macro Z_ARM_CRC32 at compile time to use the ARMv8
(aarch64) crc32x and crc32b instructions. This code does not check
for the presence of the crc32 instructions. Those instructions are
optional for ARMv8.0, though mandatory for ARMv8.1 and later. The
use of the crc32 instructions is about ten times as fast as the
software braided calculation of the CRC-32. This can noticeably
speed up the decompression of gzip streams.
inflateSync() is used to skip invalid deflate data, which means
that the check value that was being computed is no longer useful.
This commit turns off the check value computation, and furthermore
allows a successful return if the compressed data terminated in a
graceful manner. This commit also fixes a bug in the case that
inflateSync() is used before a header is ever processed. In that
case, there is no knowledge of a trailer, so the remainder is
treated as raw.
Use the interleaved method of Kadatch and Jenkins in order to make
use of pipelined instructions through multiple ALUs in a single
core. This also speeds up and simplifies the combination of CRCs,
and updates the functions to pre-calculate and use an operator for
CRC combination.
When the same len2 is used repeatedly, it is faster to use
crc32_combine_gen() to generate an operator, that is then used to
combine CRCs with crc32_combine_op().
There is no assurance that all prefix codes are reachable as
optimal Huffman codes for the numbers of symbols encountered in
a deflate block. This code considers all possible prefix codes,
which might be a larger set than all possible Huffman codes,
depending on the constraints.
This bug was reported by Danilo Ramos of Eideticom, Inc. It has
lain in wait 13 years before being found! The bug was introduced
in zlib 1.2.2.2, with the addition of the Z_FIXED option. That
option forces the use of fixed Huffman codes. For rare inputs with
a large number of distant matches, the pending buffer into which
the compressed data is written can overwrite the distance symbol
table which it overlays. That results in corrupted output due to
invalid distances, and can result in out-of-bound accesses,
crashing the application.
The fix here combines the distance buffer and literal/length
buffers into a single symbol buffer. Now three bytes of pending
buffer space are opened up for each literal or length/distance
pair consumed, instead of the previous two bytes. This assures
that the pending buffer cannot overwrite the symbol table, since
the maximum fixed code compressed length/distance is 31 bits, and
since there are four bytes of pending space for every three bytes
of symbol space.
