With its current design, a careless use of pg_cryptohash_final() could
would result in an out-of-bound write in memory as the size of the
destination buffer to store the result digest is not known to the
cryptohash internals, without the caller knowing about that. This
commit adds a new argument to pg_cryptohash_final() to allow such sanity
checks, and implements such defenses.
The internals of SCRAM for HMAC could be tightened a bit more, but as
everything is based on SCRAM_KEY_LEN with uses particular to this code
there is no need to complicate its interface more than necessary, and
this comes back to the refactoring of HMAC in core. Except that, this
minimizes the uses of the existing DIGEST_LENGTH variables, relying
instead on sizeof() for the result sizes. In ossp-uuid, this also makes
the code more defensive, as it already relied on dce_uuid_t being at
least the size of a MD5 digest.
This is in philosophy similar to cfc40d3 for base64.c and aef8948 for
hex.c.
Reported-by: Ranier Vilela
Author: Michael Paquier, Ranier Vilela
Reviewed-by: Kyotaro Horiguchi
Discussion: https://postgr.es/m/CAEudQAoqEGmcff3J4sTSV-R_16Monuz-UpJFbf_dnVH=APr02Q@mail.gmail.com
This adjusts some code related to recent changes for cryptohash
functions:
- Add a variable in md5.h to track down the size of a computed result,
moved from pgcrypto. Note that pg_md5_hash() assumed a result of this
size already.
- Call explicit_bzero() on the hashed data when freeing the context for
fallback implementations. For MD5, particularly, it would be annoying
to leave some non-zeroed data around.
- Clean up some code related to recent changes of uuid-ossp. .gitignore
still included md5.c and a comment was incorrect.
Discussion: https://postgr.es/m/X9HXKTgrvJvYO7Oh@paquier.xyz
This commit heavily reorganizes the MD5 implementations that exist in
the tree in various aspects.
First, MD5 is added to the list of options available in cryptohash.c and
cryptohash_openssl.c. This means that if building with OpenSSL, EVP is
used for MD5 instead of the fallback implementation that Postgres had
for ages. With the recent refactoring work for cryptohash functions,
this change is straight-forward. If not building with OpenSSL, a
fallback implementation internal to src/common/ is used.
Second, this reduces the number of MD5 implementations present in the
tree from two to one, by moving the KAME implementation from pgcrypto to
src/common/, and by removing the implementation that existed in
src/common/. KAME was already structured with an init/update/final set
of routines by pgcrypto (see original pgcrypto/md5.h) for compatibility
with OpenSSL, so moving it to src/common/ has proved to be a
straight-forward move, requiring no actual manipulation of the internals
of each routine. Some benchmarking has not shown any performance gap
between both implementations.
Similarly to the fallback implementation used for SHA2, the fallback
implementation of MD5 is moved to src/common/md5.c with an internal
header called md5_int.h for the init, update and final routines. This
gets then consumed by cryptohash.c.
The original routines used for MD5-hashed passwords are moved to a
separate file called md5_common.c, also in src/common/, aimed at being
shared between all MD5 implementations as utility routines to keep
compatibility with any code relying on them.
Like the SHA2 changes, this commit had its round of tests on both Linux
and Windows, across all versions of OpenSSL supported on HEAD, with and
even without OpenSSL.
Author: Michael Paquier
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/20201106073434.GA4961@paquier.xyz
