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programs/gunzip: allocate at least one byte for decompressed data

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libdeflate's 'gunzip' program fails if the uncompressed file size is a
nonzero multiple of 4 GiB because then the ISIZE field in the gzip file
is 0, so gunzip allocates no space for the decompressed data.  Then when
libdeflate returns LIBDEFLATE_INSUFFICIENT_SPACE, gunzip doubles the
buffer size which stays 0, causing it to report "file corrupt or too
large to be processed by this program".

While neither libdeflate nor its 'gunzip' program is designed for single
gzip streams this large anyway, this particular bug can easily be fixed
by always allocating at least one byte for the decompressed data.
This commit is contained in:
Eric Biggers 2019-05-21 21:13:59 -07:00
parent bc40841abf
commit e90463fb04
1 changed files with 9 additions and 0 deletions
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9
programs/gzip.c
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@ -200,7 +200,16 @@ do_decompress(struct libdeflate_decompressor *decompressor,
goto out; goto out;
} }
/*
* Use the ISIZE field as a hint for the decompressed data size. It may
* need to be increased later, however, because the file may contain
* multiple gzip members and the particular ISIZE we happen to use may
* not be the largest; or the real size may be >= 4 GiB, causing ISIZE
* to overflow. In any case, make sure to allocate at least one byte.
*/
uncompressed_size = load_u32_gzip(&compressed_data[compressed_size - 4]); uncompressed_size = load_u32_gzip(&compressed_data[compressed_size - 4]);
if (uncompressed_size == 0)
uncompressed_size = 1;
do { do {
if (uncompressed_data == NULL) { if (uncompressed_data == NULL) {