Override domain in KT gRPC errors with chat domain

service/src/main/java/org/whispersystems/textsecuregcm/grpc/ErrorUtil.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2026 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.grpc;
+
+import com.google.protobuf.InvalidProtocolBufferException;
+import com.google.rpc.ErrorInfo;
+import java.io.UncheckedIOException;
+import java.util.Optional;
+
+public class ErrorUtil {
+  public static Optional<ErrorInfo> errorInfo(final com.google.rpc.Status statusProto) {
+    return statusProto.getDetailsList().stream()
+        .filter(any -> any.is(ErrorInfo.class))
+        .map(errorInfo -> {
+          try {
+            return errorInfo.unpack(ErrorInfo.class);
+          } catch (final InvalidProtocolBufferException e) {
+            throw new UncheckedIOException(e);
+          }
+        })
+        .findFirst();
+  }
+}

service/src/main/java/org/whispersystems/textsecuregcm/grpc/KeyTransparencyGrpcService.java

@@ -6,22 +6,19 @@
 package org.whispersystems.textsecuregcm.grpc;
 
 import com.google.common.annotations.VisibleForTesting;
-import io.grpc.Status;
-import org.signal.keytransparency.client.AciMonitorRequest;
-import org.signal.keytransparency.client.ConsistencyParameters;
+import com.google.protobuf.Any;
+import com.google.rpc.ErrorInfo;
+import com.google.rpc.Status;
+import io.grpc.StatusRuntimeException;
+import io.grpc.protobuf.StatusProto;
 import org.signal.keytransparency.client.DistinguishedRequest;
 import org.signal.keytransparency.client.DistinguishedResponse;
-import org.signal.keytransparency.client.E164MonitorRequest;
 import org.signal.keytransparency.client.E164SearchRequest;
 import org.signal.keytransparency.client.MonitorRequest;
-import org.signal.keytransparency.client.MonitorResponse;
 import org.signal.keytransparency.client.MonitorResponseV2;
 import org.signal.keytransparency.client.SearchRequest;
-import org.signal.keytransparency.client.SearchResponse;
 import org.signal.keytransparency.client.SearchResponseV2;
 import org.signal.keytransparency.client.SimpleKeyTransparencyQueryServiceGrpc;
-import org.signal.keytransparency.client.UsernameHashMonitorRequest;
-import org.whispersystems.textsecuregcm.controllers.AccountController;
 import org.whispersystems.textsecuregcm.controllers.RateLimitExceededException;
 import org.whispersystems.textsecuregcm.identity.AciServiceIdentifier;
 import org.whispersystems.textsecuregcm.keytransparency.KeyTransparencyServiceClient;
@@ -88,4 +85,28 @@ public class KeyTransparencyGrpcService extends
 
     return request;
   }
+
+  @Override
+  public Throwable mapException(final Throwable throwable) {
+    // Reconstruct the exception so that we can override the backing service domain with chat's own domain.
+    if (throwable instanceof StatusRuntimeException s) {
+      final ErrorInfo.Builder errInfoBuilder = ErrorInfo.newBuilder()
+          .setDomain(GrpcExceptions.DOMAIN);
+
+      final Status statusProto = StatusProto.fromStatusAndTrailers(s.getStatus(), s.getTrailers());
+
+      ErrorUtil.errorInfo(statusProto)
+          .map(ErrorInfo::getReason)
+          .ifPresent(errInfoBuilder::setReason);
+
+      return StatusProto.toStatusRuntimeException(Status.newBuilder()
+          // See https://github.com/signalapp/key-transparency-server/blob/30b7a2a40604fbe04545d47f26e4c5a35f5d3161/cmd/kt-server/errors.go#L32
+          // for a list of error codes that the key transparency service can generate.
+          .setCode(statusProto.getCode())
+          .setMessage(statusProto.getMessage())
+          .addDetails(Any.pack(errInfoBuilder.build()))
+          .build());
+    }
+    return throwable;
+  }
 }

service/src/main/java/org/whispersystems/textsecuregcm/grpc/MetricServerInterceptor.java

@@ -127,7 +127,7 @@ public class MetricServerInterceptor implements ServerInterceptor {
     @Override
     public void close(final Status status, final Metadata responseHeaders) {
       if (!status.isOk()) {
-        reason = errorInfo(StatusProto.fromStatusAndTrailers(status, responseHeaders))
+        reason = ErrorUtil.errorInfo(StatusProto.fromStatusAndTrailers(status, responseHeaders))
             .map(ErrorInfo::getReason)
             .orElse(DEFAULT_ERROR_REASON);
       }
@@ -232,16 +232,4 @@ public class MetricServerInterceptor implements ServerInterceptor {
     }
   }
 
-  private static Optional<ErrorInfo> errorInfo(final com.google.rpc.Status statusProto) {
-    return statusProto.getDetailsList().stream()
-        .filter(any -> any.is(ErrorInfo.class))
-        .map(errorInfo -> {
-          try {
-            return errorInfo.unpack(ErrorInfo.class);
-          } catch (final InvalidProtocolBufferException e) {
-            throw new UncheckedIOException(e);
-          }
-        })
-        .findFirst();
-  }
 }

service/src/test/java/org/whispersystems/textsecuregcm/grpc/KeyTransparencyGrpcServiceTest.java

@@ -5,10 +5,14 @@
 
 package org.whispersystems.textsecuregcm.grpc;
 
+import com.google.protobuf.Any;
 import com.google.protobuf.ByteString;
+import com.google.rpc.ErrorInfo;
 import io.grpc.Channel;
 import io.grpc.ServerInterceptor;
 import io.grpc.Status;
+import io.grpc.StatusRuntimeException;
+import io.grpc.protobuf.StatusProto;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
@@ -32,7 +36,6 @@ import org.whispersystems.textsecuregcm.controllers.RateLimitExceededException;
 import org.whispersystems.textsecuregcm.keytransparency.KeyTransparencyServiceClient;
 import org.whispersystems.textsecuregcm.limits.RateLimiter;
 import org.whispersystems.textsecuregcm.limits.RateLimiters;
-import reactor.core.publisher.Mono;
 
 import java.time.Duration;
 import java.util.List;
@@ -40,6 +43,8 @@ import java.util.Optional;
 import java.util.stream.Stream;
 
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
@@ -54,6 +59,7 @@ import static org.whispersystems.textsecuregcm.controllers.KeyTransparencyContro
 import static org.whispersystems.textsecuregcm.controllers.KeyTransparencyControllerTest.USERNAME_HASH;
 import static org.whispersystems.textsecuregcm.grpc.GrpcTestUtils.assertRateLimitExceeded;
 import static org.whispersystems.textsecuregcm.grpc.GrpcTestUtils.assertStatusException;
+import static org.whispersystems.textsecuregcm.grpc.GrpcTestUtils.extractErrorInfo;
 import static org.whispersystems.textsecuregcm.grpc.KeyTransparencyGrpcService.COMMITMENT_INDEX_LENGTH;
 
 @SuppressWarnings({"OptionalUsedAsFieldOrParameterType", "ResultOfMethodCallIgnored"})
@@ -63,6 +69,9 @@ public class KeyTransparencyGrpcServiceTest extends SimpleBaseGrpcTest<KeyTransp
   @Mock
   private RateLimiter rateLimiter;
 
+  // The key transparency service uses a different domain from the chat server.
+  private static final String KEY_TRANSPARENCY_DOMAIN = "key-transparency";
+
   @Override
   protected KeyTransparencyGrpcService createServiceBeforeEachTest() {
     final RateLimiters rateLimiters = mock(RateLimiters.class);
@@ -79,9 +88,8 @@ public class KeyTransparencyGrpcServiceTest extends SimpleBaseGrpcTest<KeyTransp
   }
 
   @Test
-  void searchSuccess() throws RateLimitExceededException {
+  void searchSuccess() {
     when(keyTransparencyServiceClient.search(any())).thenReturn(SearchResponseV2.getDefaultInstance());
-    Mockito.doNothing().when(rateLimiter).validate(any(String.class));
     final SearchRequest request = SearchRequest.newBuilder()
         .setAci(ByteString.copyFrom(ACI.toCompactByteArray()))
         .setAciIdentityKey(ByteString.copyFrom(ACI_IDENTITY_KEY.serialize()))
@@ -156,11 +164,38 @@ public class KeyTransparencyGrpcServiceTest extends SimpleBaseGrpcTest<KeyTransp
     verifyNoInteractions(keyTransparencyServiceClient);
   }
 
+  @Test
+  void overrideBackingServiceErrorDomain() {
+    final StatusRuntimeException keyTransparencyException = StatusProto.toStatusRuntimeException(
+        com.google.rpc.Status.newBuilder()
+            .setCode(Status.Code.UNAVAILABLE.value())
+            .addDetails(Any.pack(ErrorInfo.newBuilder()
+                .setDomain(KEY_TRANSPARENCY_DOMAIN)
+                .setReason("UNAVAILABLE")
+                .build()))
+            .build());
+
+    when(keyTransparencyServiceClient.search(any())).thenThrow(keyTransparencyException);
+
+    final SearchRequest request = SearchRequest.newBuilder()
+        .setAci(ByteString.copyFrom(ACI.toCompactByteArray()))
+        .setAciIdentityKey(ByteString.copyFrom(ACI_IDENTITY_KEY.serialize()))
+        .setConsistency(ConsistencyParameters.newBuilder()
+            .setDistinguished(10)
+            .build())
+        .build();
+
+    final StatusRuntimeException exception =
+        assertThrows(StatusRuntimeException.class, () -> unauthenticatedServiceStub().searchV2(request));
+
+    assertEquals(GrpcExceptions.DOMAIN, extractErrorInfo(exception).getDomain(),
+        "errors from the key transparency service must report the chat server's error domain");
+  }
+
   @Test
   void monitorSuccess() {
     when(keyTransparencyServiceClient.monitor(any())).thenReturn(MonitorResponseV2.getDefaultInstance());
-    when(rateLimiter.validateReactive(any(String.class)))
-        .thenReturn(Mono.empty());
+
     final AciMonitorRequest aciMonitorRequest = AciMonitorRequest.newBuilder()
         .setAci(ByteString.copyFrom(ACI.toCompactByteArray()))
         .setCommitmentIndex(ByteString.copyFrom(new byte[COMMITMENT_INDEX_LENGTH]))
@@ -250,8 +285,6 @@ public class KeyTransparencyGrpcServiceTest extends SimpleBaseGrpcTest<KeyTransp
   @Test
   void distinguishedSuccess() {
     when(keyTransparencyServiceClient.distinguished(any())).thenReturn(DistinguishedResponse.getDefaultInstance());
-    when(rateLimiter.validateReactive(any(String.class)))
-        .thenReturn(Mono.empty());
     final DistinguishedRequest request = DistinguishedRequest.newBuilder().build();
 
     assertDoesNotThrow(() -> unauthenticatedServiceStub().distinguishedV2(request));