Do not cache failed futures for async security policies indefinitely.

binder/src/androidTest/java/io/grpc/binder/BinderSecurityTest.java

@@ -26,6 +26,7 @@
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.MoreExecutors;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.protobuf.Empty;
 import io.grpc.CallOptions;
 import io.grpc.ManagedChannel;
@@ -45,6 +46,8 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.atomic.AtomicReference;
+
 import javax.annotation.Nullable;
 import org.junit.After;
 import org.junit.Before;
@@ -76,6 +79,7 @@ public void setupServiceDefinitionsAndMethods() {
             MethodDescriptor.newBuilder(marshaller, marshaller)
                 .setFullMethodName(name)
                 .setType(MethodDescriptor.MethodType.UNARY)
+                .setSampledToLocalTracing(true)
                 .build();
         ServerCallHandler<Empty, Empty> callHandler =
             ServerCalls.asyncUnaryCall(
@@ -139,12 +143,16 @@ private void assertCallSuccess(MethodDescriptor<Empty, Empty> method) {
         .isNotNull();
   }
 
-  private void assertCallFailure(MethodDescriptor<Empty, Empty> method, Status status) {
+  @CanIgnoreReturnValue
+  private StatusRuntimeException assertCallFailure(
+      MethodDescriptor<Empty, Empty> method, Status status) {
     try {
       ClientCalls.blockingUnaryCall(channel, method, CallOptions.DEFAULT, null);
-      fail();
+      fail("Expected call to " + method.getFullMethodName() + " to fail but it succeeded.");
+      throw new AssertionError();  // impossible
     } catch (StatusRuntimeException sre) {
       assertThat(sre.getStatus().getCode()).isEqualTo(status.getCode());
+      return sre;
     }
   }
 
@@ -172,6 +180,70 @@ public void testServerDisallowsCalls() throws Exception {
     }
   }
 
+  @Test
+  public void testFailedFuturesPropagateOriginalException() throws Exception {
+    String errorMessage = "something went wrong";
+    IllegalStateException originalException = new IllegalStateException(errorMessage);
+    createChannel(
+        ServerSecurityPolicy.newBuilder()
+            .servicePolicy("foo", new AsyncSecurityPolicy() {
+              @Override
+              ListenableFuture<Status> checkAuthorizationAsync(int uid) {
+                return Futures.immediateFailedFuture(originalException);
+              }
+            })
+            .build(),
+        SecurityPolicies.internalOnly());
+    MethodDescriptor<Empty, Empty> method = methods.get("foo/method0");
+
+    StatusRuntimeException sre = assertCallFailure(method, Status.INTERNAL);
+    assertThat(sre.getStatus().getDescription()).contains(errorMessage);
+  }
+
+  @Test
+  public void testFailedFuturesAreNotCachedPermanently() throws Exception {
+    AtomicReference<Boolean> firstAttempt = new AtomicReference<>(true);
+    createChannel(
+        ServerSecurityPolicy.newBuilder()
+            .servicePolicy("foo", new AsyncSecurityPolicy() {
+              @Override
+              ListenableFuture<Status> checkAuthorizationAsync(int uid) {
+                if (firstAttempt.getAndSet(false)) {
+                  return Futures.immediateFailedFuture(new IllegalStateException());
+                }
+                return Futures.immediateFuture(Status.OK);
+              }
+            })
+            .build(),
+        SecurityPolicies.internalOnly());
+    MethodDescriptor<Empty, Empty> method = methods.get("foo/method0");
+
+    assertCallFailure(method, Status.INTERNAL);
+    assertCallSuccess(method);
+  }
+
+  @Test
+  public void testCancelledFuturesAreNotCachedPermanently() throws Exception {
+    AtomicReference<Boolean> firstAttempt = new AtomicReference<>(true);
+    createChannel(
+        ServerSecurityPolicy.newBuilder()
+            .servicePolicy("foo", new AsyncSecurityPolicy() {
+              @Override
+              ListenableFuture<Status> checkAuthorizationAsync(int uid) {
+                if (firstAttempt.getAndSet(false)) {
+                  return Futures.immediateCancelledFuture();
+                }
+                return Futures.immediateFuture(Status.OK);
+              }
+            })
+            .build(),
+        SecurityPolicies.internalOnly());
+    MethodDescriptor<Empty, Empty> method = methods.get("foo/method0");
+
+    assertCallFailure(method, Status.INTERNAL);
+    assertCallSuccess(method);
+  }
+
   @Test
   public void testClientDoesntTrustServer() throws Exception {
     createChannel(SecurityPolicies.serverInternalOnly(), policy((uid) -> false));

binder/src/main/java/io/grpc/binder/internal/BinderTransportSecurity.java

@@ -19,6 +19,7 @@
 import com.google.common.util.concurrent.FutureCallback;
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.MoreExecutors;
 
 import io.grpc.Attributes;
 import io.grpc.Internal;
@@ -32,6 +33,7 @@
 import io.grpc.Status;
 import io.grpc.internal.GrpcAttributes;
 
+import java.util.concurrent.CancellationException;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
@@ -110,9 +112,13 @@ public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
       Status authStatus;
       try {
         authStatus = Futures.getDone(authStatusFuture);
-      } catch (ExecutionException e) {
+      } catch (ExecutionException | CancellationException e) {
         // Failed futures are treated as an internal error rather than a security rejection.
         authStatus = Status.INTERNAL.withCause(e);
+        @Nullable String message = e.getMessage();
+        if (message != null) {
+          authStatus = authStatus.withDescription(message);
+        }
       }
 
       if (authStatus.isOk()) {
@@ -179,6 +185,8 @@ ListenableFuture<Status> checkAuthorization(MethodDescriptor<?, ?> method) {
       if (useCache) {
         @Nullable ListenableFuture<Status> authorization = serviceAuthorization.get(serviceName);
         if (authorization != null) {
+          // Authorization check exists and is a pending or successful future (even if for a
+          // failed authorization).
           return authorization;
         }
       }
@@ -193,6 +201,15 @@ ListenableFuture<Status> checkAuthorization(MethodDescriptor<?, ?> method) {
           serverPolicyChecker.checkAuthorizationForServiceAsync(uid, serviceName);
       if (useCache) {
         serviceAuthorization.putIfAbsent(serviceName, authorization);
+        Futures.addCallback(authorization, new FutureCallback<Status>() {
+          @Override
+          public void onSuccess(Status result) {}
+
+          @Override
+          public void onFailure(Throwable t) {
+            serviceAuthorization.remove(serviceName, authorization);
+          }
+        }, MoreExecutors.directExecutor());
       }
       return authorization;
     }