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5fe55a0fe4
The grammar was a little shaky and confusing here, so word-smith it a bit. Also, adjust the comments in pg_ident.conf.sample to use the same terminology as the SGML docs, in particular "DATABASE-USERNAME" not "PG-USERNAME". Back-patch appropriate subsets. I did not risk changing pg_ident.conf.sample in released branches, but it still seems OK to change it in v18. Reported-by: Alexey Shishkin <alexey.shishkin@enterprisedb.com> Author: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: David G. Johnston <david.g.johnston@gmail.com> Discussion: https://postgr.es/m/175206279327.3157504.12519088928605422253@wrigleys.postgresql.org Backpatch-through: 13
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()).