Never read off the end of a buffer in base32_encode()

When we "fixed" #18280 in 4e4a7d2b0c199227252a742541461ec4cc35d358
in 0291 it appears that we introduced a bug: The base32_encode
function can read off the end of the input buffer, if the input
buffer size modulo 5 is not equal to 0 or 3.

This is not completely horrible, for two reasons:
   * The extra bits that are read are never actually used: so this
     is only a crash when asan is enabled, in the worst case.  Not a
     data leak.

   * The input sizes passed to base32_encode are only ever multiples
      of 5. They are all either DIGEST_LEN (20), REND_SERVICE_ID_LEN
      (10), sizeof(rand_bytes) in addressmap.c (10), or an input in
      crypto.c that is forced to a multiple of 5.

So this bug can't actually trigger in today's Tor.

Closes bug 21894; bugfix on 0.2.9.1-alpha.

0 files changed, 0 insertions, 0 deletions