feat!: support PKCE in the oauth2 client's auth/exchange flow #21215
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Used in coder primary auth
Emyrk
commented
Dec 11, 2025
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Breaking Change: Existing oauth apps might now use PKCE. If an unknown type was being used, and it does not support PKCE, it will break.
To fix, set the PKCE methods on the external auth to
nonePKCE challenge used in primary coderd oauth2 flow.
Closes #21213
Implementation from: golang/oauth2@55cd552
What this does
This adds PKCE support when Coder is the OAuth client to an external IdP.
OIDC
PKCE support is automatically detected from the
well-knownconfiguration endpoint. If it is supported, Coder will use it.coder/cli/server.go
Lines 189 to 195 in 53fc864
OAuth (github login & external auth).
Known Oauth types have defaults set based on manual testing. We need to manually test to expand coverage.
We assume PKCE is supported by all unknown oauth IdP's. This can fixed in the configuration
Example to disable:
Manual tests
Tested to work on:
{"message":"Failed exchanging Oauth code.","detail":"oauth2: \"bad_verification_code\" \"The code passed is incorrect or expired.\" \"https://docs.github.com/apps/managing-oauth-apps/troubleshooting-oauth-app-access-token-request-errors/#bad-verification-code\""}{"message":"Failed exchanging Oauth code.","detail":"oauth2: \"invalid_grant\" \"The provided authorization grant is invalid, expired, revoked, does not match the redirection URI used in the authorization request, or was issued to another client.\""}{"message":"Failed exchanging Oauth code.","detail":"oauth2: \"unauthorized_client\" \"failed PKCE code challenge\""}{"message":"Failed exchanging Oauth code.","detail":"oauth2: \"invalid_grant\" \"Invalid authorization code\""}