mirror of
https://github.com/postgres/postgres.git
synced 2025-11-13 00:03:54 -05:00
44bd0126c7
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
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()).