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Enforce the rule that COMPRESS_OK means progress was made.

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If COMPRESS_OK occurs but data is neither consumed nor generated,
treat it as a BUG and a COMPRESS_ERROR.

This change is meant to prevent infinite loops in the case where
we've made a mistake in one of our compression backends.

Closes ticket 22672.
This commit is contained in:
Nick Mathewson 2017-06-20 12:26:57 -04:00
parent 945256188a
commit 9328bd524e
2 changed files with 30 additions and 11 deletions
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5
changes/bug22672 Normal file
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@ -0,0 +1,5 @@
o Minor features (compression, defensive programming):
- Detect and break out of infinite loops in our compression code.
We don't think that any such loops exist now, but it's best to be
safe. Closes ticket 22672.

36
src/common/compress.c
View File

@ -548,28 +548,42 @@ tor_compress_process(tor_compress_state_t *state,
int finish)
{
tor_assert(state != NULL);
const size_t in_len_orig = *in_len;
const size_t out_len_orig = *out_len;
tor_compress_output_t rv;
switch (state->method) {
case GZIP_METHOD:
case ZLIB_METHOD:
return tor_zlib_compress_process(state->u.zlib_state,
out, out_len, in, in_len,
finish);
rv = tor_zlib_compress_process(state->u.zlib_state,
out, out_len, in, in_len,
finish);
break;
case LZMA_METHOD:
return tor_lzma_compress_process(state->u.lzma_state,
out, out_len, in, in_len,
finish);
rv =tor_lzma_compress_process(state->u.lzma_state,
out, out_len, in, in_len,
finish);
break;
case ZSTD_METHOD:
return tor_zstd_compress_process(state->u.zstd_state,
out, out_len, in, in_len,
finish);
rv = tor_zstd_compress_process(state->u.zstd_state,
out, out_len, in, in_len,
finish);
break;
case NO_METHOD:
return tor_cnone_compress_process(out, out_len, in, in_len,
finish);
rv = tor_cnone_compress_process(out, out_len, in, in_len,
finish);
break;
default:
case UNKNOWN_METHOD:
goto err;
}
if (BUG((rv == TOR_COMPRESS_OK) &&
*in_len == in_len_orig &&
*out_len == out_len_orig)) {
return TOR_COMPRESS_ERROR;
}
return rv;
err:
return TOR_COMPRESS_ERROR;
}