Описание
PostgreSQL JDBC Driver: Silent channel-binding authentication downgrade via unsupported certificate algorithms
Impact
channelBinding=require connections can be silently downgraded from SCRAM-SHA-256-PLUS (with channel binding) to plain SCRAM-SHA-256 (without it), losing the man-in-the-middle protection the setting is meant to guarantee. An attacker who can intercept the TLS connection triggers the downgrade with a certificate whose signature algorithm has no tls-server-end-point channel-binding hash. Examples are Ed25519, Ed448, and post-quantum algorithms.
Two issues combine in releases 42.7.4 through 42.7.11:
- The bundled
com.ongres.scram:scram-client(3.1 or 3.2) returns an empty byte array instead of failing when it cannot derive the binding hash for such a certificate. This is the library issue tracked as GHSA-p9jg-fcr6-3mhf. - pgJDBC does not enforce
channelBinding=requirewhere it matters.ScramAuthenticatorchecks only that the server advertised a-PLUSmechanism; it neither rejects the empty binding nor checks that the negotiated mechanism uses channel binding. The connection therefore downgrades silently, and would do so even against a fixedscram-client, because the missing enforcement is in pgJDBC's own code.
Only connections that set channelBinding=require are affected. Under the default prefer policy, and under allow or disable, falling back to plain SCRAM is the documented behaviour. Releases before 42.7.4 are unaffected, because they do not support channel binding.
Patches
Fixed in pgJDBC 42.7.12. pgJDBC now enforces channel binding in its own code, independently of the scram-client version:
- Under
channelBinding=require, it fails the connection when no channel-binding data can be extracted from the server certificate, instead of passing an empty value to the SCRAM client. The error names the certificate signature algorithm. - After negotiation, it requires the selected mechanism to use channel binding (a
-PLUSmechanism) wheneverchannelBinding=requireis set, regardless of how negotiation resolved.
Upgrade to 42.7.12 or later.
Workarounds
No pgJDBC setting restores channel-binding enforcement on an affected release; upgrading is the fix.
If you cannot upgrade immediately, verify the server certificate at the TLS layer so that a man-in-the-middle cannot present a substitute certificate. Set sslmode=verify-full with a truststore that contains only your server's CA. This defence is independent of channel binding and blocks the same attacker. Connections that rely on channelBinding=require in place of certificate verification have no equivalent workaround and should upgrade.
References
- GHSA-p9jg-fcr6-3mhf — the related
com.ongres.scram:scram-clientissue (root cause of the empty channel-binding value). scram-client3.3 release (library fix): https://github.com/ongres/scram/releases/tag/3.3- pgJDBC fix in 42.7.12: commit
Пакеты
org.postgresql:postgresql
>= 42.7.4, < 42.7.12
42.7.12
Связанные уязвимости
pgjdbc is an open source postgresql JDBC Driver. In releases 42.7.4 through 42.7.11, channelBinding=require connections can be silently downgraded from SCRAM-SHA-256-PLUS with channel binding to plain SCRAM-SHA-256 without it, losing the man-in-the-middle protection the setting is meant to guarantee. An attacker who can intercept the TLS connection can trigger the downgrade with a certificate whose signature algorithm has no tls-server-end-point channel-binding hash, because the bundled com.ongres.scram:scram-client returns an empty byte array instead of failing and pgJDBC ScramAuthenticator checks only that the server advertised a PLUS mechanism, without rejecting the empty binding or checking that the negotiated mechanism uses channel binding. This issue is fixed in version 42.7.12.
pgjdbc is an open source postgresql JDBC Driver. In releases 42.7.4 through 42.7.11, channelBinding=require connections can be silently downgraded from SCRAM-SHA-256-PLUS with channel binding to plain SCRAM-SHA-256 without it, losing the man-in-the-middle protection the setting is meant to guarantee. An attacker who can intercept the TLS connection can trigger the downgrade with a certificate whose signature algorithm has no tls-server-end-point channel-binding hash, because the bundled com.ongres.scram:scram-client returns an empty byte array instead of failing and pgJDBC ScramAuthenticator checks only that the server advertised a PLUS mechanism, without rejecting the empty binding or checking that the negotiated mechanism uses channel binding. This issue is fixed in version 42.7.12.
pgjdbc is an open source postgresql JDBC Driver. In releases 42.7.4 through 42.7.11, channelBinding=require connections can be silently downgraded from SCRAM-SHA-256-PLUS with channel binding to plain SCRAM-SHA-256 without it, losing the man-in-the-middle protection the setting is meant to guarantee. An attacker who can intercept the TLS connection can trigger the downgrade with a certificate whose signature algorithm has no tls-server-end-point channel-binding hash, because the bundled com.ongres.scram:scram-client returns an empty byte array instead of failing and pgJDBC ScramAuthenticator checks only that the server advertised a PLUS mechanism, without rejecting the empty binding or checking that the negotiated mechanism uses channel binding. This issue is fixed in version 42.7.12.
pgjdbc is an open source postgresql JDBC Driver. In releases 42.7.4 th ...