Commit 1fcfc186 authored by Nick Mathewson's avatar Nick Mathewson 🦀
Browse files

clean up message; explain a magic number in a comment

parent d14b0d54

src/common/torgzip.c

+12 −3
Original line number Diff line number Diff line
@@ -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;

        }