feat(postgres): support SASL OAUTHBEARER authentication - #4400
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PostgreSQL 18 added the `oauth` HBA method, which authenticates over SASL
OAUTHBEARER (RFC 7628) instead of a password. `sasl::authenticate` accepted
only SCRAM-SHA-256 and SCRAM-SHA-256-PLUS, so such a server was unreachable.
This is the token-first flow only: the caller supplies a bearer token and the
driver performs the SASL exchange. SQLx does not contact an identity provider,
so the discovery and device-authorization flows of RFC 7628 are not
implemented; this matches the scope other drivers limit themselves to.
let options = PgConnectOptions::new().oauth_token_provider(|| async {
Ok(refresh_my_token().await?)
});
The provider is called once per connection attempt rather than stored, so a
pool that reconnects after the token expired presents a fresh one.
`oauth_token` sets a fixed token where that is enough.
Notes:
- OAUTHBEARER defines no channel binding and the server rejects the `p`
specifier, so the gs2 header is always `n,,` and this does not go through
the `-PLUS` machinery.
- The token is checked against the `b64token` grammar of RFC 6750 before it
reaches the wire, which is what the server enforces too. The grammar
excludes the kvsep byte, whitespace and NUL, so a token that passes cannot
forge additional key/value pairs or truncate the message.
- `PgOAuthToken` has a hand-written `Debug` that prints nothing, because
`PgConnectOptions` derives `Debug` and a bearer token is a credential. The
token also never appears in an error.
- No connection-string option is added: a URL ends up in shell history, in
`ps` output and in logs.
- `SaslInitialResponse` now carries the mechanism name instead of a `plus`
flag that was always `false`.
- No new dependencies.
geoHeil
marked this pull request as draft
August 29, 2026 09:30
geoHeil
marked this pull request as ready for review
August 29, 2026 11:24
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Closes #4399.
PG18 docker verified
audmatchesselect current_user, version()returnedtestuser | PostgreSQL 18.6audnames another serviceError::Database, code 28000audclaim absentaudis an array containing the expected value