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Michael Paquier 44bd0126c7 Add more sanity checks in SASL exchanges 
The following checks are added, to make the SASL infrastructure more
aware of defects when implementing new mechanisms:
- Detect that no output is generated by a mechanism if an exchange fails
in the backend, failing if there is a message waiting to be sent.
- Handle zero-length messages in the frontend.  The backend handles that
already, and SCRAM would complain if sending empty messages as this is
not authorized for this mechanism, but other mechanisms may want this
capability (the SASL specification allows that).
- Make sure that a mechanism generates a message in the middle of the
exchange in the frontend.

SCRAM, as implemented, respects all these requirements already, and the
recent refactoring of SASL done in 9fd8557 helps in documenting that in
a cleaner way.

Analyzed-by: Jacob Champion
Author: Michael Paquier
Reviewed-by: Jacob Champion
Discussion: https://postgr.es/m/3d2a6f5d50e741117d6baf83eb67ebf1a8a35a11.camel@vmware.com
 		2021-07-10 21:45:28 +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 Add more sanity checks in SASL exchanges 2021-07-10 21:45:28 +09:00
auth-scram.c Refactor SASL code with a generic interface for its mechanisms 2021-07-07 10:55:15 +09:00
auth.c Refactor SASL code with a generic interface for its mechanisms 2021-07-07 10:55:15 +09:00
be-fsstubs.c Update copyright for 2021 2021-01-02 13:06:25 -05:00
be-gssapi-common.c Don't assume GSSAPI result strings are null-terminated. 2021-06-23 14:01:32 -04:00
be-secure-common.c Update copyright for 2021 2021-01-02 13:06:25 -05:00
be-secure-gssapi.c Update copyright for 2021 2021-01-02 13:06:25 -05:00
be-secure-openssl.c Disallow SSL renegotiation 2021-05-25 10:10:09 +09:00
be-secure.c Allow matching the DN of a client certificate for authentication 2021-03-29 15:49:39 -04:00
crypt.c Update copyright for 2021 2021-01-02 13:06:25 -05:00
hba.c Fix RADIUS error reporting in hba file parsing 2021-05-31 18:43:48 +02:00
ifaddr.c Update copyright for 2021 2021-01-02 13:06:25 -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 Initial pgindent and pgperltidy run for v14. 2021-05-12 13:14:10 -04:00
pqformat.c Update copyright for 2021 2021-01-02 13:06:25 -05:00
pqmq.c Remove server and libpq support for old FE/BE protocol version 2. 2021-03-04 10:45:55 +02:00
pqsignal.c Use signalfd(2) for epoll latches. 2021-03-01 14:12:02 +13:00

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()).