[legacy] Fix bug in zstd-0.5 decoder #1696
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The match length and literal length extra bytes could either by 2 bytes or 3 bytes in version 0.5. All earlier verions were always 3 bytes, and later version didn't have dumps. The bug, introduced by commit 0fd322f, was triggered when the last dump was a 2-byte dump, because we didn't separate that case from a 3-byte dump, and thought we were over-reading. I've tested this fix with every zstd version < 1.0.0 on the buggy file, and we are now always successfully decompressing with the right checksum. Fixes facebook#1693.
Cyan4973
approved these changes
Jul 22, 2019
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The match length and literal length extra bytes could either
by 2 bytes or 3 bytes in version 0.5. All earlier verions were
always 3 bytes, and later version didn't have dumps.
The bug, introduced by commit 0fd322f,
was triggered when the last dump was a 2-byte dump, because we didn't
separate that case from a 3-byte dump, and thought we were over-reading.
I've tested this fix with every zstd version < 1.0.0 on the buggy file,
and we are now always successfully decompressing with the right
checksum.
Fixes #1693.