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Alex SedovandGitHub d3012d5169 feat: add RFC 8707 resource indicator via resource config (#161 )

* feat: add RFC 8707 resource indicator via resource config

`Config.Resource` is an alternative to `audience` for IdPs that implement
RFC 8707. `buildAuthURL` sends it as the `resource` parameter on the
authorization request, before `extraAuthParams` so an operator-configured
`resource` key there cannot override or duplicate it. `exchangeTokens`
repeats it on both the `authorization_code` and `refresh_token` grants
(RFC 8707 §2.2), so a refreshed token keeps the audience binding of the
original grant.

Only one resource is accepted. RFC 8707 permits a list, but no provider
that supports the parameter handles a list usefully: one rejects any
request naming more than one resource with HTTP 400 `invalid_target`;
node-oidc-provider accepts several and issues an opaque token bound to
none of them.

`Config.Validate()` requires an absolute URI of at most 256 characters
with no fragment, wildcard, or control characters. `http`/`https` values
go through `isValidSecureURL`, so HTTPS is required outside loopback;
other schemes (`urn:`) pass as-is.

When `resource` is set and `audience` is not, `audience` defaults to the
resource for access-token validation; `strictAudienceValidation` applies
the same way whichever of the two is set. That default is validation-only.
A new `TraefikOidc.explicitAudience` mirrors `Config.Audience` verbatim,
and `buildAuthURL` keys the non-standard `audience` request parameter (the
Auth0 custom-API pattern) on it rather than on `audience`, so a
resource-derived default is never sent as an unsolicited `audience`
parameter alongside `resource` — a combination that misbehaves against
providers such as Ory Hydra, which give `audience` a different meaning.
`audience_test.go` and `url_helpers_ultra_test.go` set `audience` on the
struct directly, bypassing `New()`, and now set `explicitAudience` too.

docs/CONFIGURATION.md carries only the reference-table row and a short
pointer; the new docs/RFC8707.md holds the request behaviour, the
single-resource rationale, the `resource`/`audience` relationship, and a
provider-support table from interop testing: node-oidc-provider supports
it; Zitadel accepts and silently ignores it (`oidc.AuthRequest` has no
`resource` field, confirmed against a live instance); Authentik returns
`invalid_target`; Keycloak has no support through 26.6; Ory Hydra/Fosite
uses its own `audience` parameter; Azure AD/Entra ID v2 is reported to
reject `resource` combined with v2-style `scope`; Auth0 and AWS Cognito
claims are unverified. README.md, docs/index.html, and .traefik.yml each
point at docs/RFC8707.md instead of repeating it, and the comments on
`Config.Resource`, in main.go, and in url_helpers.go defer to it as well.

rfc8707_resource_test.go covers the authorization-URL parameter (set,
unset, query-bearing value percent-encoded rather than merged,
`extraAuthParams` unable to override), both grants sending `resource` in
the form body, the `Config.Validate()` rules table, audience defaulting
through `New()`, and a regression pair: a resource-derived audience
default is not sent as `audience`, while an explicitly configured one
still is.

* fix: accept Resource in place of Audience for bearer-auth validation

`NewWithContext` rejected `EnableBearerAuth=true` whenever
`config.Audience` was empty, even though `t.audience` already falls back
to `config.Resource` in that case. The check now fails only when both
`Audience` and `Resource` are empty, and the error names both fields.
`TestStartupValidation_BearerAcceptsResourceInPlaceOfAudience` covers the
`Resource`-only configuration.

`docs/RFC8707.md` links the `audience` parameter note to
`docs/AUTH0_AUDIENCE_GUIDE.md` instead of restating it, and drops the
provider table's GitHub row and the interop-testing paragraph, which are
covered elsewhere.

2026-09-10 14:49:53 +01:00

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RFC 8707 Resource Indicators

resource (Config.Resource) is an alternative to audience for IdPs that implement RFC 8707. See docs/CONFIGURATION.md for the config reference; this document covers exactly what request is made and which providers support it.

What the plugin sends

One resource parameter on the authorization request (buildAuthURL), added before extraAuthParams so an operator-configured resource key there cannot override or duplicate it.
The same resource parameter on both the authorization_code and refresh_token grants (exchangeTokens), per RFC 8707 §2.2 — so a refreshed token keeps the same audience binding as the original grant.

Only a single resource is supported, not a list. RFC 8707 allows a server to accept multiple resource values and scope the issued token to a subset of them, but no provider found to support the parameter at all handles that usefully: one provider tested rejects a request naming more than one resource with HTTP 400 invalid_target; node-oidc-provider accepts multiple resources but issues an opaque access token bound to none of them. A single value avoids both failure modes.

Relationship to `audience`

resource and audience both feed the same access-token audience check — strictAudienceValidation applies identically to either — but they produce different requests on the wire:

audience, when explicitly configured, is sent as a non-standard audience request parameter (see docs/AUTH0_AUDIENCE_GUIDE.md).
resource is sent as the RFC 8707 resource parameter instead.
If resource is set and audience is not, the expected-audience check defaults to the resource value, but this is validation-only: it does not cause an audience parameter to be sent. Setting both is allowed — e.g. as a hedge against a provider that ignores resource — in which case both parameters are sent.

Provider support

Verified 2026-09-02 (Zitadel reverified separately against a live instance). RFC 8707 requires a server that does not support resource to ignore it, but not every implementation does — verify against your specific provider and version before relying on it.

Provider	Support	Notes
node-oidc-provider	Supported	Via its `resourceIndicators` feature.
Zitadel	Ignored, not rejected	`oidc.AuthRequest` has no `resource` field; confirmed against a live instance — `/oauth/v2/authorize` returns the same `302` with or without `resource`, including a spec-invalid value.
Authentik	Rejected	Returns `invalid_target` ("Resource indicators are not supported").
Keycloak	Not supported (through 26.6)	Its own guidance is an audience mapper plus `scope` instead (keycloak/keycloak#41526).
Ory Hydra / Fosite	Not implemented	Uses its own non-standard `audience` request parameter instead.
Azure AD / Entra ID v2.0 (MSAL)	Reported to reject	When combined with v2-style `scope`, rather than ignoring it (writeup). Do not enable against an Entra ID v2 tenant without confirming. The v1.0 endpoint has a separate, pre-RFC `resource` parameter with similar but not identical semantics.
Auth0	Not verified	Documents a Resource Parameter Compatibility Profile mapping `resource` → `audience` (Auth0 docs).
AWS Cognito	Not verified	Announced Oct 2025 for user-pool authorization-code/implicit grants (announcement).
Okta, Google, GitLab	Unverified	No confirming documentation found either way.

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RFC 8707 Resource Indicators

What the plugin sends

Relationship to audience

Provider support

3.9 KiB

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Relationship to `audience`