Commit d9a6b37a authored by Alexander Hansen Færøy's avatar Alexander Hansen Færøy 💬
Browse files

Add diagnostic log message for compression bombs. 

This patch causes `tor_compress_is_compression_bomb()` to emit a
warning-level log message that lets us learn the potential ratio of the
input to output buffer sizes. Hopefully, this will give us a bit of a
better idea whether the compression bomb ratio needs some tuning.

See: tpo/core/tor#40739.
parent d6c89b1a

changes/ticket40739

0 → 100644
+3 −0
Original line number Diff line number Diff line 
  o Minor features (debugging, compression):

    - Log the input and output buffer sizes when we detect a potential

      compression bomb. Diagnostic for ticket 40739.

src/lib/compress/compress.c

+9 −1
Original line number Diff line number Diff line
@@ -66,7 +66,15 @@ tor_compress_is_compression_bomb,(size_t size_in, size_t size_out)) 
  if (size_in == 0 || size_out < CHECK_FOR_COMPRESSION_BOMB_AFTER)

    return 0;



  return (size_out / size_in > MAX_UNCOMPRESSION_FACTOR);

  if (size_out / size_in > MAX_UNCOMPRESSION_FACTOR) {

    log_warn(LD_GENERAL,

             "Detected possible compression bomb with "

             "input size = %"TOR_PRIuSZ " and output size = %"TOR_PRIuSZ,

             size_in, size_out);

    return 1;

  }



  return 0;

}



/** Guess the size that <b>in_len</b> will be after compression or

src/test/test_util.c

+1 −1
Original line number Diff line number Diff line
@@ -2945,7 +2945,7 @@ test_util_gzip_compression_bomb(void *arg) 
  tt_int_op(-1, OP_EQ, tor_compress(&result, &result_len,

                                    one_mb, one_million,

                                    ZLIB_METHOD));

  expect_single_log_msg_containing(

  expect_log_msg_containing(

         "We compressed something and got an insanely high "

         "compression factor; other Tors would think this "

         "was a compression bomb.");