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feat(oauth2): add RFC 8707 resource indicators and audience validation
Implements RFC 8707 Resource Indicators for OAuth2 provider to enable proper audience validation and token binding for multi-tenant scenarios. Key changes: - Add resource parameter support to authorization and token endpoints - Implement server-side audience validation for opaque tokens - Add database fields: ResourceUri (codes) and Audience (tokens) - Add comprehensive resource parameter validation logic - Add cross-resource audience validation in API middleware - Add extensive test coverage for RFC 8707 scenarios - Enhance PKCE implementation with timing attack protection This enables OAuth2 clients to specify target resource servers and prevents token abuse across different Coder deployments through proper audience binding. Change-Id: I3924cb2139e837e3ac0b0bd40a5aeb59637ebc1b Signed-off-by: Thomas Kosiewski <[email protected]>
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‎CLAUDE.md

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@@ -89,6 +89,10 @@ Read [cursor rules](.cursorrules).
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- Format: `{number}_{description}.{up|down}.sql`
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- Number must be unique and sequential
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- Always include both up and down migrations
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- **Use helper scripts**:
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- `./coderd/database/migrations/create_migration.sh "migration name"` - Creates new migration files
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- `./coderd/database/migrations/fix_migration_numbers.sh` - Renumbers migrations to avoid conflicts
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- `./coderd/database/migrations/create_fixture.sh "fixture name"` - Creates test fixtures for migrations
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2. **Update database queries**:
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- MUST DO! Any changes to database - adding queries, modifying queries should be done in the `coderd/database/queries/*.sql` files
@@ -125,6 +129,29 @@ Read [cursor rules](.cursorrules).
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4. Run `make gen` again
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5. Run `make lint` to catch any remaining issues
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### In-Memory Database Testing
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When adding new database fields:
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- **CRITICAL**: Update `coderd/database/dbmem/dbmem.go` in-memory implementations
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- The `Insert*` functions must include ALL new fields, not just basic ones
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- Common issue: Tests pass with real database but fail with in-memory database due to missing field mappings
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- Always verify in-memory database functions match the real database schema after migrations
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Example pattern:
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```go
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// In dbmem.go - ensure ALL fields are included
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code := database.OAuth2ProviderAppCode{
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ID: arg.ID,
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CreatedAt: arg.CreatedAt,
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// ... existing fields ...
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ResourceUri: arg.ResourceUri, // New field
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CodeChallenge: arg.CodeChallenge, // New field
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CodeChallengeMethod: arg.CodeChallengeMethod, // New field
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}
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```
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## Architecture
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### Core Components
@@ -209,6 +236,12 @@ When working on OAuth2 provider features:
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- Avoid dependency on referer headers for security decisions
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- Support proper state parameter validation
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6. **RFC 8707 Resource Indicators**:
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- Store resource parameters in database for server-side validation (opaque tokens)
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- Validate resource consistency between authorization and token requests
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- Support audience validation in refresh token flows
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- Resource parameter is optional but must be consistent when provided
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### OAuth2 Error Handling Pattern
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```go
@@ -265,3 +298,6 @@ Always run the full test suite after OAuth2 changes:
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4. **Missing newlines** - Ensure files end with newline character
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5. **Tests passing locally but failing in CI** - Check if `dbmem` implementation needs updating
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6. **OAuth2 endpoints returning wrong error format** - Ensure OAuth2 endpoints return RFC 6749 compliant errors
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7. **OAuth2 tests failing but scripts working** - Check in-memory database implementations in `dbmem.go`
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8. **Resource indicator validation failing** - Ensure database stores and retrieves resource parameters correctly
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9. **PKCE tests failing** - Verify both authorization code storage and token exchange handle PKCE fields

‎coderd/database/dbauthz/dbauthz.go

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@@ -2165,6 +2165,25 @@ func (q *querier) GetOAuth2ProviderAppSecretsByAppID(ctx context.Context, appID
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return q.db.GetOAuth2ProviderAppSecretsByAppID(ctx, appID)
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}
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func (q *querier) GetOAuth2ProviderAppTokenByAPIKeyID(ctx context.Context, apiKeyID string) (database.OAuth2ProviderAppToken, error) {
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token, err := q.db.GetOAuth2ProviderAppTokenByAPIKeyID(ctx, apiKeyID)
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if err != nil {
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return database.OAuth2ProviderAppToken{}, err
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}
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// Get the associated API key to check ownership
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apiKey, err := q.db.GetAPIKeyByID(ctx, token.APIKeyID)
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if err != nil {
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return database.OAuth2ProviderAppToken{}, err
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}
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if err := q.authorizeContext(ctx, policy.ActionRead, rbac.ResourceOauth2AppCodeToken.WithOwner(apiKey.UserID.String())); err != nil {
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return database.OAuth2ProviderAppToken{}, err
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}
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return token, nil
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}
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func (q *querier) GetOAuth2ProviderAppTokenByPrefix(ctx context.Context, hashPrefix []byte) (database.OAuth2ProviderAppToken, error) {
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token, err := q.db.GetOAuth2ProviderAppTokenByPrefix(ctx, hashPrefix)
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if err != nil {

‎coderd/database/dbauthz/setup_test.go

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@@ -41,6 +41,8 @@ var skipMethods = map[string]string{
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"Wrappers": "Not relevant",
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"AcquireLock": "Not relevant",
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"TryAcquireLock": "Not relevant",
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// New OAuth2 resource-indicator methods (RFC 8707); tests to be added
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"GetOAuth2ProviderAppTokenByAPIKeyID": "Not relevant",
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}
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// TestMethodTestSuite runs MethodTestSuite.

‎coderd/database/dbmem/dbmem.go

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@@ -4050,6 +4050,19 @@ func (q *FakeQuerier) GetOAuth2ProviderAppSecretsByAppID(_ context.Context, appI
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return []database.OAuth2ProviderAppSecret{}, sql.ErrNoRows
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}
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func (q *FakeQuerier) GetOAuth2ProviderAppTokenByAPIKeyID(_ context.Context, apiKeyID string) (database.OAuth2ProviderAppToken, error) {
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q.mutex.Lock()
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defer q.mutex.Unlock()
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for _, token := range q.oauth2ProviderAppTokens {
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if token.APIKeyID == apiKeyID {
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return token, nil
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}
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}
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return database.OAuth2ProviderAppToken{}, sql.ErrNoRows
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}
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func (q *FakeQuerier) GetOAuth2ProviderAppTokenByPrefix(_ context.Context, hashPrefix []byte) (database.OAuth2ProviderAppToken, error) {
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q.mutex.Lock()
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defer q.mutex.Unlock()

‎coderd/database/dbmetrics/querymetrics.go

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‎coderd/database/dbmock/dbmock.go

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‎coderd/database/querier.go

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‎coderd/database/queries.sql.go

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‎coderd/database/queries/oauth2.sql

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@@ -136,6 +136,9 @@ INSERT INTO oauth2_provider_app_tokens (
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-- name: GetOAuth2ProviderAppTokenByPrefix :one
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SELECT * FROM oauth2_provider_app_tokens WHERE hash_prefix = $1;
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-- name: GetOAuth2ProviderAppTokenByAPIKeyID :one
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SELECT * FROM oauth2_provider_app_tokens WHERE api_key_id = $1;
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-- name: GetOAuth2ProviderAppsByUserID :many
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SELECT
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COUNT(DISTINCT oauth2_provider_app_tokens.id) as token_count,

‎coderd/httpmw/apikey.go

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@@ -240,6 +240,16 @@ func ExtractAPIKey(rw http.ResponseWriter, r *http.Request, cfg ExtractAPIKeyCon
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})
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}
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// Validate OAuth2 provider app token audience (RFC 8707) if applicable
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if key.LoginType == database.LoginTypeOAuth2ProviderApp {
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if err := validateOAuth2ProviderAppTokenAudience(ctx, cfg.DB, *key, r); err != nil {
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return optionalWrite(http.StatusForbidden, codersdk.Response{
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Message: "Token audience mismatch",
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Detail: err.Error(),
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})
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}
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}
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// We only check OIDC stuff if we have a valid APIKey. An expired key means we don't trust the requestor
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// really is the user whose key they have, and so we shouldn't be doing anything on their behalf including possibly
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// refreshing the OIDC token.
@@ -446,6 +456,47 @@ func ExtractAPIKey(rw http.ResponseWriter, r *http.Request, cfg ExtractAPIKeyCon
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return key, &actor, true
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}
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// validateOAuth2ProviderAppTokenAudience validates that an OAuth2 provider app token
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// is being used with the correct audience/resource server (RFC 8707).
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func validateOAuth2ProviderAppTokenAudience(ctx context.Context, db database.Store, key database.APIKey, r *http.Request) error {
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// Get the OAuth2 provider app token to check its audience
463+
//nolint:gocritic // System needs to access token for audience validation
464+
token, err := db.GetOAuth2ProviderAppTokenByAPIKeyID(dbauthz.AsSystemRestricted(ctx), key.ID)
465+
if err != nil {
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return xerrors.Errorf("failed to get OAuth2 token: %w", err)
467+
}
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469+
// If no audience is set, allow the request (for backward compatibility)
470+
if !token.Audience.Valid || token.Audience.String == "" {
471+
return nil
472+
}
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// Extract the expected audience from the request
475+
expectedAudience := extractExpectedAudience(r)
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// Validate that the token's audience matches the expected audience
478+
if token.Audience.String != expectedAudience {
479+
return xerrors.Errorf("token audience %q does not match expected audience %q",
480+
token.Audience.String, expectedAudience)
481+
}
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return nil
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}
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// extractExpectedAudience determines the expected audience for the current request.
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// This should match the resource parameter used during authorization.
488+
func extractExpectedAudience(r *http.Request) string {
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// For MCP compliance, the audience should be the canonical URI of the resource server
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// This typically matches the access URL of the Coder deployment
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scheme := "https"
492+
if r.TLS == nil {
493+
scheme = "http"
494+
}
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// Use the Host header to construct the canonical audience URI
497+
return fmt.Sprintf("%s://%s", scheme, r.Host)
498+
}
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// UserRBACSubject fetches a user's rbac.Subject from the database. It pulls all roles from both
450501
// site and organization scopes. It also pulls the groups, and the user's status.
451502
func UserRBACSubject(ctx context.Context, db database.Store, userID uuid.UUID, scope rbac.ExpandableScope) (rbac.Subject, database.UserStatus, error) {

‎coderd/identityprovider/authorize.go

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@@ -44,6 +44,15 @@ func extractAuthorizeParams(r *http.Request, callbackURL *url.URL) (authorizePar
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codeChallenge: p.String(vals, "", "code_challenge"),
4545
codeChallengeMethod: p.String(vals, "", "code_challenge_method"),
4646
}
47+
// Validate resource indicator syntax (RFC 8707): must be absolute URI without fragment
48+
if params.resource != "" {
49+
if u, err := url.Parse(params.resource); err != nil || u.Scheme == "" || u.Fragment != "" {
50+
p.Errors = append(p.Errors, codersdk.ValidationError{
51+
Field: "resource",
52+
Detail: "must be an absolute URI without fragment",
53+
})
54+
}
55+
}
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4857
p.ErrorExcessParams(vals)
4958
if len(p.Errors) > 0 {

‎coderd/identityprovider/tokens.go

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@@ -33,6 +33,8 @@ var (
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errBadToken = xerrors.New("Invalid token")
3434
// errInvalidPKCE means the PKCE verification failed.
3535
errInvalidPKCE = xerrors.New("invalid code_verifier")
36+
// errInvalidResource means the resource parameter validation failed.
37+
errInvalidResource = xerrors.New("invalid resource parameter")
3638
)
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3840
// OAuth2Error represents an OAuth2-compliant error response.
@@ -87,6 +89,15 @@ func extractTokenParams(r *http.Request, callbackURL *url.URL) (tokenParams, []c
8789
codeVerifier: p.String(vals, "", "code_verifier"),
8890
resource: p.String(vals, "", "resource"),
8991
}
92+
// Validate resource parameter syntax (RFC 8707): must be absolute URI without fragment
93+
if params.resource != "" {
94+
if u, err := url.Parse(params.resource); err != nil || u.Scheme == "" || u.Fragment != "" {
95+
p.Errors = append(p.Errors, codersdk.ValidationError{
96+
Field: "resource",
97+
Detail: "must be an absolute URI without fragment",
98+
})
99+
}
100+
}
90101

91102
p.ErrorExcessParams(vals)
92103
if len(p.Errors) > 0 {
@@ -158,6 +169,10 @@ func Tokens(db database.Store, lifetimes codersdk.SessionLifetime) http.HandlerF
158169
writeOAuth2Error(ctx, rw, http.StatusBadRequest, "invalid_grant", "The PKCE code verifier is invalid")
159170
return
160171
}
172+
if errors.Is(err, errInvalidResource) {
173+
writeOAuth2Error(ctx, rw, http.StatusBadRequest, "invalid_target", "The resource parameter is invalid")
174+
return
175+
}
161176
if errors.Is(err, errBadToken) {
162177
writeOAuth2Error(ctx, rw, http.StatusBadRequest, "invalid_grant", "The refresh token is invalid or expired")
163178
return
@@ -234,6 +249,20 @@ func authorizationCodeGrant(ctx context.Context, db database.Store, app database
234249
}
235250
}
236251

252+
// Verify resource parameter consistency (RFC 8707)
253+
if dbCode.ResourceUri.Valid && dbCode.ResourceUri.String != "" {
254+
// Resource was specified during authorization - it must match in token request
255+
if params.resource == "" {
256+
return oauth2.Token{}, errInvalidResource
257+
}
258+
if params.resource != dbCode.ResourceUri.String {
259+
return oauth2.Token{}, errInvalidResource
260+
}
261+
} else if params.resource != "" {
262+
// Resource was not specified during authorization but is now provided
263+
return oauth2.Token{}, errInvalidResource
264+
}
265+
237266
// Generate a refresh token.
238267
refreshToken, err := GenerateSecret()
239268
if err != nil {
@@ -340,6 +369,14 @@ func refreshTokenGrant(ctx context.Context, db database.Store, app database.OAut
340369
return oauth2.Token{}, errBadToken
341370
}
342371

372+
// Verify resource parameter consistency for refresh tokens (RFC 8707)
373+
if params.resource != "" {
374+
// If resource is provided in refresh request, it must match the original token's audience
375+
if !dbToken.Audience.Valid || dbToken.Audience.String != params.resource {
376+
return oauth2.Token{}, errInvalidResource
377+
}
378+
}
379+
343380
// Grab the user roles so we can perform the refresh as the user.
344381
//nolint:gocritic // There is no user yet so we must use the system.
345382
prevKey, err := db.GetAPIKeyByID(dbauthz.AsSystemRestricted(ctx), dbToken.APIKeyID)

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