postgresql

History

Michael Paquier 5513dc6a30 Improve error handling of HMAC computations This is similar to `b69aba7`, except that this completes the work for HMAC with a new routine called pg_hmac_error() that would provide more context about the type of error that happened during a HMAC computation: - The fallback HMAC implementation in hmac.c relies on cryptohashes, so in some code paths it is necessary to return back the error generated by cryptohashes. - For the OpenSSL implementation (hmac_openssl.c), the logic is very similar to cryptohash_openssl.c, where the error context comes from OpenSSL if one of its internal routines failed, with different error codes if something internal to hmac_openssl.c failed or was incorrect. Any in-core code paths that use the centralized HMAC interface are related to SCRAM, for errors that are unlikely going to happen, with only SHA-256. It would be possible to see errors when computing some HMACs with MD5 for example and OpenSSL FIPS enabled, and this commit would help in reporting the correct errors but nothing in core uses that. So, at the end, no backpatch to v14 is done, at least for now. Errors in SCRAM related to the computation of the server key, stored key, etc. need to pass down the potential error context string across more layers of their respective call stacks for the frontend and the backend, so each surrounding routine is adapted for this purpose. Reviewed-by: Sergey Shinderuk Discussion: https://postgr.es/m/Yd0N9tSAIIkFd+qi@paquier.xyz		2022-01-13 16:17:21 +09:00
..
Makefile	Refactor SASL code with a generic interface for its mechanisms	2021-07-07 10:55:15 +09:00
README.SSL	Move EDH support to common files	2018-01-23 07:11:38 -05:00
auth-sasl.c	Improve error handling of cryptohash computations	2022-01-11 09:55:16 +09:00
auth-scram.c	Improve error handling of HMAC computations	2022-01-13 16:17:21 +09:00
auth.c	Clean up messy API for src/port/thread.c.	2022-01-11 13:46:20 -05:00
be-fsstubs.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
be-gssapi-common.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
be-secure-common.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
be-secure-gssapi.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
be-secure-openssl.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
be-secure.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
crypt.c	Improve error handling of cryptohash computations	2022-01-11 09:55:16 +09:00
hba.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
ifaddr.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
pg_hba.conf.sample	pg_hba.conf.sample: Reword connection type section	2021-04-29 07:00:20 +02:00
pg_ident.conf.sample	Reformat the comments in pg_hba.conf and pg_ident.conf	2010-01-26 06:58:39 +00:00
pqcomm.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
pqformat.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
pqmq.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00
pqsignal.c	Update copyright for 2022	2022-01-07 19:04:57 -05:00

README.SSL

src/backend/libpq/README.SSL

SSL
===

>From the servers perspective:


  Receives StartupPacket
           |
           |
 (Is SSL_NEGOTIATE_CODE?) -----------  Normal startup
           |                  No
           |
           | Yes
           |
           |
 (Server compiled with USE_SSL?) ------- Send 'N'
           |                       No        |
           |                                 |
           | Yes                         Normal startup
           |
           |
        Send 'S'
           |
           |
      Establish SSL
           |
           |
      Normal startup





>From the clients perspective (v6.6 client _with_ SSL):


      Connect
         |
         |
  Send packet with SSL_NEGOTIATE_CODE
         |
         |
  Receive single char  ------- 'S' -------- Establish SSL
         |                                       |
         | '<else>'                              |
         |                                  Normal startup
         |
         |
   Is it 'E' for error  ------------------- Retry connection
         |                  Yes             without SSL
         | No
         |
   Is it 'N' for normal ------------------- Normal startup
         |                  Yes
         |
   Fail with unknown

---------------------------------------------------------------------------

Ephemeral DH
============

Since the server static private key ($DataDir/server.key) will
normally be stored unencrypted so that the database backend can
restart automatically, it is important that we select an algorithm
that continues to provide confidentiality even if the attacker has the
server's private key.  Ephemeral DH (EDH) keys provide this and more
(Perfect Forward Secrecy aka PFS).

N.B., the static private key should still be protected to the largest
extent possible, to minimize the risk of impersonations.

Another benefit of EDH is that it allows the backend and clients to
use DSA keys.  DSA keys can only provide digital signatures, not
encryption, and are often acceptable in jurisdictions where RSA keys
are unacceptable.

The downside to EDH is that it makes it impossible to use ssldump(1)
if there's a problem establishing an SSL session.  In this case you'll
need to temporarily disable EDH (see initialize_dh()).