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clean up message; explain a magic number in a comment

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This commit is contained in:
Nick Mathewson 2011-01-15 12:12:10 -05:00
parent d14b0d54d2
commit 1fcfc18628
1 changed files with 12 additions and 3 deletions
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15
src/common/torgzip.c
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@ -58,9 +58,18 @@ method_bits(compress_method_t method)
}
/* These macros define the maximum allowable compression factor. Anything of
* size greater than <b>check_for_compression_bomb_after</b> is not allowed to
* size greater than CHECK_FOR_COMPRESSION_BOMB_AFTER is not allowed to
* have an uncompression factor (uncompressed size:compressed size ratio) of
* any greater than MAX_UNCOMPRESSION_FACTOR. */
* any greater than MAX_UNCOMPRESSION_FACTOR.
*
* Picking a value for MAX_UNCOMPRESSION_FACTOR is a trade-off: we want it to
* be small to limit the attack multiplier, but we also want it to be large
* enough so that no legitimate document --even ones we might invent in the
* future -- ever compresses by a factor of greater than
* MAX_UNCOMPRESSION_FACTOR. Within those parameters, there's a reasonably
* large range of possible values. IMO, anything over 8 is probably safe; IMO
* anything under 50 is probably sufficient.
*/
#define MAX_UNCOMPRESSION_FACTOR 25
#define CHECK_FOR_COMPRESSION_BOMB_AFTER (1024*64)
@ -291,7 +300,7 @@ tor_gzip_uncompress(char **out, size_t *out_len,
goto err;
}
if (is_compression_bomb(in_len, out_size)) {
log_warn(LD_GENERAL, "Input looks look a possible zlib bomb; "
log_warn(LD_GENERAL, "Input looks like a possible zlib bomb; "
"not proceeding.");
goto err;
}