Add a fallback token verifier (#2216)

This allows us to switch the proxy to a different client ID without
disrupting the service. This is a temporary measure and will be removed
once the switch is complete.

core/src/main/java/google/registry/config/RegistryConfig.java

@@ -1192,6 +1192,12 @@ public final class RegistryConfig {
       return config.auth.oauthClientId;
     }
 
+    @Provides
+    @Config("fallbackOauthClientId")
+    public static String provideFallbackOauthClientId(RegistryConfigSettings config) {
+      return config.auth.fallbackOauthClientId;
+    }
+
     /**
      * Provides the OAuth scopes required for accessing Google APIs using the default credential.
      */

core/src/main/java/google/registry/config/RegistryConfigSettings.java

@@ -61,6 +61,7 @@ public class RegistryConfigSettings {
   public static class Auth {
     public List<String> allowedServiceAccountEmails;
     public String oauthClientId;
+    public String fallbackOauthClientId;
   }
 
   /** Configuration options for accessing Google APIs. */

core/src/main/java/google/registry/config/files/default-config.yaml

@@ -321,6 +321,10 @@ auth:
   # the same as this one.
   oauthClientId: iap-oauth-clientid
 
+  # Same as above, but serve as a fallback, so we can switch the client ID of
+  # the proxy without downtime.
+  fallbackOauthClientId: fallback-oauth-clientid
+
 credentialOAuth:
   # OAuth scopes required for accessing Google APIs using the default
   # credential.

core/src/main/java/google/registry/request/auth/AuthModule.java

@@ -55,6 +55,9 @@ public class AuthModule {
   @Qualifier
   @interface RegularOidc {}
 
+  @Qualifier
+  @interface RegularOidcFallback {}
+
   @Provides
   @IapOidc
   @Singleton
@@ -71,6 +74,14 @@ public class AuthModule {
     return TokenVerifier.newBuilder().setAudience(clientId).setIssuer(REGULAR_ISSUER_URL).build();
   }
 
+  @Provides
+  @RegularOidcFallback
+  @Singleton
+  TokenVerifier provideFallbackRegularTokenVerifier(
+      @Config("fallbackOauthClientId") String clientId) {
+    return TokenVerifier.newBuilder().setAudience(clientId).setIssuer(REGULAR_ISSUER_URL).build();
+  }
+
   @Provides
   @IapOidc
   @Singleton

core/src/main/java/google/registry/request/auth/OidcTokenAuthenticationMechanism.java

@@ -25,6 +25,7 @@ import google.registry.model.console.User;
 import google.registry.model.console.UserDao;
 import google.registry.request.auth.AuthModule.IapOidc;
 import google.registry.request.auth.AuthModule.RegularOidc;
+import google.registry.request.auth.AuthModule.RegularOidcFallback;
 import google.registry.request.auth.AuthSettings.AuthLevel;
 import java.util.Optional;
 import javax.annotation.Nullable;
@@ -53,6 +54,8 @@ public abstract class OidcTokenAuthenticationMechanism implements Authentication
 
   protected final TokenVerifier tokenVerifier;
 
+  protected final Optional<TokenVerifier> fallbackTokenVerifier;
+
   protected final TokenExtractor tokenExtractor;
 
   private final ImmutableSet<String> serviceAccountEmails;
@@ -60,9 +63,11 @@ public abstract class OidcTokenAuthenticationMechanism implements Authentication
   protected OidcTokenAuthenticationMechanism(
       ImmutableSet<String> serviceAccountEmails,
       TokenVerifier tokenVerifier,
+      @Nullable TokenVerifier fallbackTokenVerifier,
       TokenExtractor tokenExtractor) {
     this.serviceAccountEmails = serviceAccountEmails;
     this.tokenVerifier = tokenVerifier;
+    this.fallbackTokenVerifier = Optional.ofNullable(fallbackTokenVerifier);
     this.tokenExtractor = tokenExtractor;
   }
 
@@ -77,7 +82,7 @@ public abstract class OidcTokenAuthenticationMechanism implements Authentication
     if (rawIdToken == null) {
       return AuthResult.NOT_AUTHENTICATED;
     }
-    JsonWebSignature token;
+    JsonWebSignature token = null;
     try {
       token = tokenVerifier.verify(rawIdToken);
     } catch (Exception e) {
@@ -86,8 +91,25 @@ public abstract class OidcTokenAuthenticationMechanism implements Authentication
           RegistryEnvironment.get().equals(RegistryEnvironment.PRODUCTION)
               ? "Raw token redacted in prod"
               : rawIdToken);
+    }
+
+    if (token == null) {
+      if (fallbackTokenVerifier.isPresent()) {
+        try {
+          token = fallbackTokenVerifier.get().verify(rawIdToken);
+        } catch (Exception e) {
+          logger.atInfo().withCause(e).log(
+              "Failed OIDC fallback verification attempt:\n%s",
+              RegistryEnvironment.get().equals(RegistryEnvironment.PRODUCTION)
+                  ? "Raw token redacted in prod"
+                  : rawIdToken);
           return AuthResult.NOT_AUTHENTICATED;
         }
+      } else {
+        return AuthResult.NOT_AUTHENTICATED;
+      }
+    }
+
     String email = (String) token.getPayload().get("email");
     if (email == null) {
       logger.atWarning().log("No email address from the OIDC token:\n%s", token.getPayload());
@@ -141,7 +163,7 @@ public abstract class OidcTokenAuthenticationMechanism implements Authentication
         @Config("allowedServiceAccountEmails") ImmutableSet<String> serviceAccountEmails,
         @IapOidc TokenVerifier tokenVerifier,
         @IapOidc TokenExtractor tokenExtractor) {
-      super(serviceAccountEmails, tokenVerifier, tokenExtractor);
+      super(serviceAccountEmails, tokenVerifier, null, tokenExtractor);
     }
   }
 
@@ -161,8 +183,9 @@ public abstract class OidcTokenAuthenticationMechanism implements Authentication
     protected RegularOidcAuthenticationMechanism(
         @Config("allowedServiceAccountEmails") ImmutableSet<String> serviceAccountEmails,
         @RegularOidc TokenVerifier tokenVerifier,
+        @RegularOidcFallback TokenVerifier fallbackTokenVerifier,
         @RegularOidc TokenExtractor tokenExtractor) {
-      super(serviceAccountEmails, tokenVerifier, tokenExtractor);
+      super(serviceAccountEmails, tokenVerifier, fallbackTokenVerifier, tokenExtractor);
     }
   }
 }

core/src/test/java/google/registry/request/auth/OidcTokenAuthenticationMechanismTest.java

@@ -19,7 +19,6 @@ import static com.google.common.truth.Truth.assertThat;
 import static google.registry.request.auth.AuthModule.BEARER_PREFIX;
 import static google.registry.request.auth.AuthModule.IAP_HEADER_NAME;
 import static google.registry.testing.DatabaseHelper.insertInDb;
-import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
@@ -70,7 +69,7 @@ public class OidcTokenAuthenticationMechanismTest {
 
   private AuthResult authResult;
   private OidcTokenAuthenticationMechanism authenticationMechanism =
-      new OidcTokenAuthenticationMechanism(serviceAccounts, tokenVerifier, e -> rawToken) {};
+      new OidcTokenAuthenticationMechanism(serviceAccounts, tokenVerifier, null, e -> rawToken) {};
 
   @RegisterExtension
   public final JpaTestExtensions.JpaUnitTestExtension jpaExtension =
@@ -78,7 +77,7 @@ public class OidcTokenAuthenticationMechanismTest {
 
   @BeforeEach
   void beforeEach() throws Exception {
-    when(tokenVerifier.verify(eq(rawToken))).thenReturn(jwt);
+    when(tokenVerifier.verify(rawToken)).thenReturn(jwt);
     payload.setEmail(email);
     payload.setSubject(gaiaId);
     insertInDb(user);
@@ -98,18 +97,30 @@ public class OidcTokenAuthenticationMechanismTest {
   @Test
   void testAuthenticate_noTokenFromRequest() {
     authenticationMechanism =
-        new OidcTokenAuthenticationMechanism(serviceAccounts, tokenVerifier, e -> null) {};
+        new OidcTokenAuthenticationMechanism(serviceAccounts, tokenVerifier, null, e -> null) {};
     authResult = authenticationMechanism.authenticate(request);
     assertThat(authResult).isEqualTo(AuthResult.NOT_AUTHENTICATED);
   }
 
   @Test
   void testAuthenticate_invalidToken() throws Exception {
-    when(tokenVerifier.verify(eq(rawToken))).thenThrow(new VerificationException("Bad token"));
+    when(tokenVerifier.verify(rawToken)).thenThrow(new VerificationException("Bad token"));
     authResult = authenticationMechanism.authenticate(request);
     assertThat(authResult).isEqualTo(AuthResult.NOT_AUTHENTICATED);
   }
 
+  @Test
+  void testAuthenticate_fallbackVerifier() throws Exception {
+    TokenVerifier fallbackVerifier = mock(TokenVerifier.class);
+    when(tokenVerifier.verify(rawToken)).thenThrow(new VerificationException("Bad token"));
+    when(fallbackVerifier.verify(rawToken)).thenReturn(jwt);
+    authenticationMechanism =
+        new OidcTokenAuthenticationMechanism(
+            serviceAccounts, tokenVerifier, fallbackVerifier, e -> rawToken) {};
+    authResult = authenticationMechanism.authenticate(request);
+    assertThat(authResult.isAuthenticated()).isEqualTo(true);
+  }
+
   @Test
   void testAuthenticate_noEmailAddress() throws Exception {
     payload.setEmail(null);
@@ -223,5 +234,12 @@ public class OidcTokenAuthenticationMechanismTest {
     String provideOauthClientId() {
       return "client-id";
     }
+
+    @Provides
+    @Singleton
+    @Config("fallbackOauthClientId")
+    String provideFallbackOauthClientId() {
+      return "fallback-client-id";
+    }
   }
 }