## Problem
When multiple concurrent callers (e.g., parallel workspace builds) read
the same single-use OAuth2 refresh token from the database and race to
exchange it with the provider, the first caller succeeds but subsequent
callers get `bad_refresh_token`. The losing caller then **clears the
valid new token** from the database, permanently breaking the auth link
until the user manually re-authenticates.
This is reliably reproducible when launching multiple workspaces
simultaneously with GitHub App external auth and user-to-server token
expiration enabled.
## Solution
Two layers of protection:
### 1. Singleflight deduplication (`Config.RefreshToken` +
`ObtainOIDCAccessToken`)
Concurrent callers for the same user/provider share a single refresh
call via `golang.org/x/sync/singleflight`, keyed by `userID`. The
singleflight callback re-reads the link from the database to pick up any
token already refreshed by a prior in-flight call, avoiding redundant
IDP round-trips entirely.
### 2. Optimistic locking on `UpdateExternalAuthLinkRefreshToken`
The SQL `WHERE` clause now includes `AND oauth_refresh_token =
@old_oauth_refresh_token`, so if two replicas (HA) race past
singleflight, the loser's destructive UPDATE is a harmless no-op rather
than overwriting the winner's valid token.
## Changes
| File | Change |
|------|--------|
| `coderd/externalauth/externalauth.go` | Added `singleflight.Group` to
`Config`; split `RefreshToken` into public wrapper +
`refreshTokenInner`; pass `OldOauthRefreshToken` to DB update |
| `coderd/provisionerdserver/provisionerdserver.go` | Wrapped OIDC
refresh in `ObtainOIDCAccessToken` with package-level singleflight |
| `coderd/database/queries/externalauth.sql` | Added optimistic lock
(`WHERE ... AND oauth_refresh_token = @old_oauth_refresh_token`) |
| `coderd/database/queries.sql.go` | Regenerated |
| `coderd/database/querier.go` | Regenerated |
| `coderd/database/dbauthz/dbauthz_test.go` | Updated test params for
new field |
| `coderd/externalauth/externalauth_test.go` | Added
`ConcurrentRefreshDedup` test; updated existing tests for singleflight
DB re-read |
## Testing
- **New test `ConcurrentRefreshDedup`**: 5 goroutines call
`RefreshToken` concurrently, asserts IDP refresh called exactly once,
all callers get same token.
- All existing `TestRefreshToken/*` subtests updated and passing.
- `TestObtainOIDCAccessToken` passing.
- `dbauthz` tests passing.
External auth refresh errors lose the original error thrown on the first
refresh. This PR saves that error to the database to be raised on
subsequent refresh attempts
https://github.com/coder/coder/pull/15608 introduced a buggy behaviour
with dbcrypt enabled.
When clearing an oauth refresh token, we had been setting the value to
the empty string.
The database encryption package considers decrypting an empty string to
be an error, as an empty encrypted string value will still have a nonce
associated with it and thus not actually be empty when stored at rest.
Instead of 'deleting' the refresh token, 'update' it to be the empty
string.
This plays nicely with dbcrypt.
It also adds a 'utility test' in the dbcrypt package to help encrypt a
value. This was useful when manually fixing users affected by this bug
on our dogfood instance.
Once a token refresh fails, we remove the `oauth_refresh_token` from the
database. This will prevent the token from hitting the IDP for
subsequent refresh attempts.
Without this change, a bad script can cause a failing token to hit a
remote IDP repeatedly with each `git` operation. With this change, after
the first hit, subsequent hits will fail locally, and never contact the
IDP.
The solution in both cases is to authenticate the external auth link. So
the resolution is the same as before.
* feat: add endpoints to list all authed external apps
Listing the apps allows users to auth to external apps without going through the create workspace flow.
* chore: rename `git_auth` to `external_auth` in our schema
We're changing Git auth to be external auth. It will support
any OAuth2 or OIDC provider.
To split up the larger change I want to contribute the schema
changes first, and I'll add the feature itself in another PR.
* Fix names
* Fix outdated view
* Rename some additional places
* Fix sort order
* Fix template versions auth route
* Fix types
* Fix dbauthz
Kyle Carberry