The existing cryptohash facility was causing problems in some code paths
related to MD5 (frontend and backend) that relied on the fact that the
only type of error that could happen would be an OOM, as the MD5
implementation used in PostgreSQL ~13 (the in-core implementation is
used when compiling with or without OpenSSL in those older versions),
could fail only under this circumstance.
The new cryptohash facilities can fail for reasons other than OOMs, like
attempting MD5 when FIPS is enabled (upstream OpenSSL allows that up to
1.0.2, Fedora and Photon patch OpenSSL 1.1.1 to allow that), so this
would cause incorrect reports to show up.
This commit extends the cryptohash APIs so as callers of those routines
can fetch more context when an error happens, by using a new routine
called pg_cryptohash_error(). The error states are stored within each
implementation's internal context data, so as it is possible to extend
the logic depending on what's suited for an implementation. The default
implementation requires few error states, but OpenSSL could report
various issues depending on its internal state so more is needed in
cryptohash_openssl.c, and the code is shaped so as we are always able to
grab the necessary information.
The core code is changed to adapt to the new error routine, painting
more "const" across the call stack where the static errors are stored,
particularly in authentication code paths on variables that provide
log details. This way, any future changes would warn if attempting to
free these strings. The MD5 authentication code was also a bit blurry
about the handling of "logdetail" (LOG sent to the postmaster), so
improve the comments related that, while on it.
The origin of the problem is 87ae969, that introduced the centralized
cryptohash facility. Extra changes are done for pgcrypto in v14 for the
non-OpenSSL code path to cope with the improvements done by this
commit.
Reported-by: Michael Mühlbeyer
Author: Michael Paquier
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/89B7F072-5BBE-4C92-903E-D83E865D9367@trivadis.com
Backpatch-through: 14
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
The same code pattern was repeated four times when compiling a SHA-2
hash. This refactoring has the advantage to issue a compilation warning
if a new value is added to pg_cryptohash_type, so as anybody doing an
addition in this area would need to consider if support for a new SQL
function is needed or not.
Author: Sehrope Sarkuni, Michael Paquier
Discussion: https://postgr.es/m/YA7DvLRn2xnTgsMc@paquier.xyz
87ae969 has created two new files called cryptohash{_openssl}.c in
src/common/, whose names overlap with the existing backend file called
cryptohashes.c dedicated to the SQL wrappers for SHA2 and MD5. This
file is renamed to cryptohashfuncs.c to be more consistent with the
surroundings and reduce the confusion with the new cryptohash interface
of src/common/.
Author: Michael Paquier
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/X8hHhaQgbMbW+aGU@paquier.xyz
Peter Eisentraut
Bruce Momjian
Michael Paquier