Add a check for missing uak in `OptionalAccess`

service/src/main/java/org/whispersystems/textsecuregcm/auth/OptionalAccess.java

@@ -73,6 +73,11 @@ public class OptionalAccess {
       return;
     }
 
+    // At this point, any successful authentication requires a real access key on the target account
+    if (targetAccount.get().getUnidentifiedAccessKey().isEmpty()) {
+      throw new NotAuthorizedException(Response.Status.UNAUTHORIZED);
+    }
+
     // Otherwise, access is gated by the caller having the unidentified-access key matching the target account.
     if (MessageDigest.isEqual(accessKey.get().getAccessKey(), targetAccount.get().getUnidentifiedAccessKey().get())) {
       return;

service/src/test/java/org/whispersystems/textsecuregcm/auth/OptionalAccessTest.java

@@ -6,6 +6,7 @@
 package org.whispersystems.textsecuregcm.auth;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
@@ -115,6 +116,22 @@ class OptionalAccessTest {
     OptionalAccess.verify(Optional.empty(), Optional.of(new Anonymous(Base64.getEncoder().encodeToString("1234".getBytes()))), Optional.of(account));
   }
 
+  @Test
+  void testUnidentifiedTargetMissingAccessKey() {
+    Account account = mock(Account.class);
+    when(account.getUnidentifiedAccessKey()).thenReturn(Optional.empty());
+    when(account.isEnabled()).thenReturn(true);
+    try {
+      OptionalAccess.verify(
+          Optional.empty(),
+          Optional.of(new Anonymous(Base64.getEncoder().encodeToString("1234".getBytes()))),
+          Optional.of(account));
+      throw new AssertionError("should fail");
+    } catch (WebApplicationException e) {
+      assertEquals(e.getResponse().getStatus(), 401);
+    }
+  }
+
   @Test
   void testUnidentifiedInactive() {
     Account account = mock(Account.class);