From 5fc6bdd478dd8ec63b7cf76a669e115296399c40 Mon Sep 17 00:00:00 2001
From: Jon Chambers <jon@signal.org>
Date: Mon, 9 Jun 2025 14:18:49 -0400
Subject: [PATCH] Add a device capability for sparse post-quantum ratchet
 (SPQR)

---
 .../textsecuregcm/grpc/DeviceCapabilityUtil.java      |  2 ++
 .../textsecuregcm/storage/DeviceCapability.java       |  3 ++-
 service/src/main/proto/org/signal/chat/common.proto   |  1 +
 .../textsecuregcm/grpc/DevicesGrpcServiceTest.java    | 11 ++++++++++-
 4 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/grpc/DeviceCapabilityUtil.java b/service/src/main/java/org/whispersystems/textsecuregcm/grpc/DeviceCapabilityUtil.java
index 0b9bd4ee5..eba69c5a3 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/grpc/DeviceCapabilityUtil.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/grpc/DeviceCapabilityUtil.java
@@ -20,6 +20,7 @@ public class DeviceCapabilityUtil {
       case DEVICE_CAPABILITY_DELETE_SYNC -> DeviceCapability.DELETE_SYNC;
       case DEVICE_CAPABILITY_STORAGE_SERVICE_RECORD_KEY_ROTATION -> DeviceCapability.STORAGE_SERVICE_RECORD_KEY_ROTATION;
       case DEVICE_CAPABILITY_ATTACHMENT_BACKFILL -> DeviceCapability.ATTACHMENT_BACKFILL;
+      case DEVICE_CAPABILITY_SPARSE_POST_QUANTUM_RATCHET -> DeviceCapability.SPARSE_POST_QUANTUM_RATCHET;
       case DEVICE_CAPABILITY_UNSPECIFIED, UNRECOGNIZED -> throw Status.INVALID_ARGUMENT.withDescription("Unrecognized device capability").asRuntimeException();
     };
   }
@@ -31,6 +32,7 @@ public class DeviceCapabilityUtil {
       case DELETE_SYNC -> org.signal.chat.common.DeviceCapability.DEVICE_CAPABILITY_DELETE_SYNC;
       case STORAGE_SERVICE_RECORD_KEY_ROTATION -> org.signal.chat.common.DeviceCapability.DEVICE_CAPABILITY_STORAGE_SERVICE_RECORD_KEY_ROTATION;
       case ATTACHMENT_BACKFILL -> org.signal.chat.common.DeviceCapability.DEVICE_CAPABILITY_ATTACHMENT_BACKFILL;
+      case SPARSE_POST_QUANTUM_RATCHET -> org.signal.chat.common.DeviceCapability.DEVICE_CAPABILITY_SPARSE_POST_QUANTUM_RATCHET;
     };
   }
 }
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/storage/DeviceCapability.java b/service/src/main/java/org/whispersystems/textsecuregcm/storage/DeviceCapability.java
index 9893ff06f..1b43f35fc 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/storage/DeviceCapability.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/storage/DeviceCapability.java
@@ -12,7 +12,8 @@ public enum DeviceCapability {
   TRANSFER("transfer", AccountCapabilityMode.PRIMARY_DEVICE, false, false),
   DELETE_SYNC("deleteSync", AccountCapabilityMode.ALL_DEVICES, true, true),
   STORAGE_SERVICE_RECORD_KEY_ROTATION("ssre2", AccountCapabilityMode.ALL_DEVICES, true, true),
-  ATTACHMENT_BACKFILL("attachmentBackfill", AccountCapabilityMode.PRIMARY_DEVICE, false, true);
+  ATTACHMENT_BACKFILL("attachmentBackfill", AccountCapabilityMode.PRIMARY_DEVICE, false, true),
+  SPARSE_POST_QUANTUM_RATCHET("spqr", AccountCapabilityMode.ALL_DEVICES, true, true);
 
   public enum AccountCapabilityMode {
     /**
diff --git a/service/src/main/proto/org/signal/chat/common.proto b/service/src/main/proto/org/signal/chat/common.proto
index 2f08a2bfa..47e09fb33 100644
--- a/service/src/main/proto/org/signal/chat/common.proto
+++ b/service/src/main/proto/org/signal/chat/common.proto
@@ -101,6 +101,7 @@ enum DeviceCapability {
   reserved 4;
   DEVICE_CAPABILITY_STORAGE_SERVICE_RECORD_KEY_ROTATION = 5;
   DEVICE_CAPABILITY_ATTACHMENT_BACKFILL = 6;
+  DEVICE_CAPABILITY_SPARSE_POST_QUANTUM_RATCHET = 7;
 }
 
 message ZkCredential {
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/grpc/DevicesGrpcServiceTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/grpc/DevicesGrpcServiceTest.java
index cd99b894b..4acff9cc3 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/grpc/DevicesGrpcServiceTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/grpc/DevicesGrpcServiceTest.java
@@ -435,7 +435,8 @@ class DevicesGrpcServiceTest extends SimpleBaseGrpcTest<DevicesGrpcService, Devi
       @CartesianTest.Values(booleans = {true, false}) final boolean storage,
       @CartesianTest.Values(booleans = {true, false}) final boolean transfer,
       @CartesianTest.Values(booleans = {true, false}) final boolean deleteSync,
-      @CartesianTest.Values(booleans = {true, false}) final boolean attachmentBackfill) {
+      @CartesianTest.Values(booleans = {true, false}) final boolean attachmentBackfill,
+      @CartesianTest.Values(booleans = {true, false}) final boolean spqr) {
 
     mockAuthenticationInterceptor().setAuthenticatedDevice(AUTHENTICATED_ACI, deviceId);
 
@@ -460,6 +461,10 @@ class DevicesGrpcServiceTest extends SimpleBaseGrpcTest<DevicesGrpcService, Devi
       requestBuilder.addCapabilities(org.signal.chat.common.DeviceCapability.DEVICE_CAPABILITY_ATTACHMENT_BACKFILL);
     }
 
+    if (spqr) {
+      requestBuilder.addCapabilities(org.signal.chat.common.DeviceCapability.DEVICE_CAPABILITY_SPARSE_POST_QUANTUM_RATCHET);
+    }
+
     final SetCapabilitiesResponse ignored = authenticatedServiceStub().setCapabilities(requestBuilder.build());
 
     final Set<DeviceCapability> expectedCapabilities = new HashSet<>();
@@ -480,6 +485,10 @@ class DevicesGrpcServiceTest extends SimpleBaseGrpcTest<DevicesGrpcService, Devi
       expectedCapabilities.add(DeviceCapability.ATTACHMENT_BACKFILL);
     }
 
+    if (spqr) {
+      expectedCapabilities.add(DeviceCapability.SPARSE_POST_QUANTUM_RATCHET);
+    }
+
     verify(device).setCapabilities(expectedCapabilities);
   }
 }