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OpenSSL 1.1.1 and newer versions have added support for RSA-PSS certificates, which requires the use of a specific routine in OpenSSL to determine which hash function to use when compiling it when using channel binding in SCRAM-SHA-256. X509_get_signature_nid(), that is the original routine the channel binding code has relied on, is not able to determine which hash algorithm to use for such certificates. However, X509_get_signature_info(), new to OpenSSL 1.1.1, is able to do it. This commit switches the channel binding logic to rely on X509_get_signature_info() over X509_get_signature_nid(), which would be the choice when building with 1.1.1 or newer. The error could have been triggered on the client or the server, hence libpq and the backend need to have their related code paths patched. Note that attempting to load an RSA-PSS certificate with OpenSSL 1.1.0 or older leads to a failure due to an unsupported algorithm. The discovery of relying on X509_get_signature_info() comes from Jacob, the tests have been written by Heikki (with few tweaks from me), while I have bundled the whole together while adding the bits needed for MSVC and meson. This issue exists since channel binding exists, so backpatch all the way down. Some tests are added in 15~, triggered if compiling with OpenSSL 1.1.1 or newer, where the certificate and key files can easily be generated for RSA-PSS. Reported-by: Gunnar "Nick" Bluth Author: Jacob Champion, Heikki Linnakangas Discussion: https://postgr.es/m/17760-b6c61e752ec07060@postgresql.org Backpatch-through: 11 |
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| .. | ||
| auth-sasl.c | ||
| auth-scram.c | ||
| auth.c | ||
| be-fsstubs.c | ||
| be-gssapi-common.c | ||
| be-secure-common.c | ||
| be-secure-gssapi.c | ||
| be-secure-openssl.c | ||
| be-secure.c | ||
| crypt.c | ||
| hba.c | ||
| ifaddr.c | ||
| Makefile | ||
| pg_hba.conf.sample | ||
| pg_ident.conf.sample | ||
| pqcomm.c | ||
| pqformat.c | ||
| pqmq.c | ||
| pqsignal.c | ||
| 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()).