oidc ignore client/audience support

.chloggen/oidc-ignore-audience.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: oidcauthextension
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add ignore_audience config option for ignoring oidc audience
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [36568]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: go-oidc SkipClientIDCheck is set based on config ignore_audience
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

extension/oidcauthextension/README.md

@@ -23,6 +23,7 @@ extensions:
     issuer_url: http://localhost:8080/auth/realms/opentelemetry
     issuer_ca_path: /etc/pki/tls/cert.pem
     audience: account
+    ignore_audience: <bool> # false if unspecified
     username_claim: email
 
 receivers:

extension/oidcauthextension/config.go

@@ -15,9 +15,13 @@ type Config struct {
 
 	// Audience of the token, used during the verification.
 	// For example: "https://accounts.google.com" or "https://login.salesforce.com".
-	// Required.
+	// Required unless IgnoreAudience is true.
 	Audience string `mapstructure:"audience"`
 
+	// When true, this skips validating the audience field.
+	// Optional.
+	IgnoreAudience bool `mapstructure:"ignore_audience"`
+
 	// The local path for the issuer CA's TLS server cert.
 	// Optional.
 	IssuerCAPath string `mapstructure:"issuer_ca_path"`
@@ -32,7 +36,7 @@ type Config struct {
 }
 
 func (c *Config) Validate() error {
-	if c.Audience == "" {
+	if c.Audience == "" && !c.IgnoreAudience {
 		return errNoAudienceProvided
 	}
 	if c.IssuerURL == "" {

extension/oidcauthextension/extension.go

@@ -68,6 +68,7 @@ func (e *oidcExtension) start(ctx context.Context, _ component.Host) error {
 	}
 	e.verifier = e.provider.Verifier(&oidc.Config{
 		ClientID: e.cfg.Audience,
+		SkipClientIDCheck: e.cfg.IgnoreAudience,
 	})
 	return nil
 }

extension/oidcauthextension/extension_test.go

@@ -69,6 +69,70 @@ func TestOIDCAuthenticationSucceeded(t *testing.T) {
 	// TODO(jpkroehling): assert that the authentication routine set the subject/membership to the resource
 }
 
+func TestOIDCAuthenticationSucceededIgnoreAudienceMismatch(t *testing.T) {
+	// prepare
+	oidcServer, err := newOIDCServer()
+	require.NoError(t, err)
+	oidcServer.Start()
+	defer oidcServer.Close()
+
+	config := &Config{
+		IssuerURL:   oidcServer.URL,
+		Audience:    "unit-test",
+		IgnoreAudience: true,
+	}
+	p := newExtension(config, zap.NewNop())
+
+	err = p.Start(context.Background(), componenttest.NewNopHost())
+	require.NoError(t, err)
+
+	payload, _ := json.Marshal(map[string]any{
+		"iss":         oidcServer.URL,
+		"aud":         "not-unit-test",
+		"exp":         time.Now().Add(time.Minute).Unix(),
+	})
+	token, err := oidcServer.token(payload)
+	require.NoError(t, err)
+
+	// test
+	ctx, err := p.Authenticate(context.Background(), map[string][]string{"authorization": {fmt.Sprintf("Bearer %s", token)}})
+
+	// verify
+	assert.NoError(t, err)
+	assert.NotNil(t, ctx)
+}
+
+func TestOIDCAuthenticationFailAudienceMismatch(t *testing.T) {
+	// prepare
+	oidcServer, err := newOIDCServer()
+	require.NoError(t, err)
+	oidcServer.Start()
+	defer oidcServer.Close()
+
+	config := &Config{
+		IssuerURL:   oidcServer.URL,
+		Audience:    "unit-test",
+	}
+	p := newExtension(config, zap.NewNop())
+
+	err = p.Start(context.Background(), componenttest.NewNopHost())
+	require.NoError(t, err)
+
+	payload, _ := json.Marshal(map[string]any{
+		"iss":         oidcServer.URL,
+		"aud":         "not-unit-test",
+		"exp":         time.Now().Add(time.Minute).Unix(),
+	})
+	token, err := oidcServer.token(payload)
+	require.NoError(t, err)
+
+	// test
+	_, err = p.Authenticate(context.Background(), map[string][]string{"authorization": {fmt.Sprintf("Bearer %s", token)}})
+
+	// verify
+	assert.Error(t, err)
+}
+
 func TestOIDCProviderForConfigWithTLS(t *testing.T) {
 	// prepare the CA cert for the TLS handler
 	cert := x509.Certificate{
@@ -423,6 +487,20 @@ func TestMissingClient(t *testing.T) {
 	assert.Equal(t, errNoAudienceProvided, err)
 }
 
+func TestIgnoreMissingClient(t *testing.T) {
+	// prepare
+	config := &Config{
+		IssuerURL: "http://example.com/",
+		IgnoreAudience: true,
+	}
+
+	// test
+	err := config.Validate()
+
+	// verify
+	assert.Nil(t, err)
+}
+
 func TestMissingIssuerURL(t *testing.T) {
 	// prepare
 	config := &Config{