Error prone checks for mutability flags on PI

Add a mutability flag check for all method calls that create a PendingIntent.

Bug: 160794467
Test: atest error_prone_android_framework_test:com.google.errorprone.bugpatterns.android.PendingIntentMutabilityCheckerTest
Change-Id: I26a51a6dddb2793e9a56e72876f3f9d2aea4e3fb

1 files changed, 81 insertions, 0 deletions

diff --git a/errorprone/java/com/google/errorprone/bugpatterns/android/PendingIntentMutabilityChecker.java b/errorprone/java/com/google/errorprone/bugpatterns/android/PendingIntentMutabilityChecker.java
new file mode 100644
index 000000000000..2561b41028cc
--- /dev/null
+++ b/errorprone/java/com/google/errorprone/bugpatterns/android/PendingIntentMutabilityChecker.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.errorprone.bugpatterns.android;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.matchers.FieldMatchers.staticField;
+import static com.google.errorprone.matchers.Matchers.anyOf;
+import static com.google.errorprone.matchers.Matchers.contains;
+import static com.google.errorprone.matchers.Matchers.methodInvocation;
+import static com.google.errorprone.matchers.Matchers.staticMethod;
+
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+
+import java.util.regex.Pattern;
+
+/**
+ * Any method calls to create a PendingIntent require that one of the
+ * mutability flags, FLAG_MUTABLE or FLAG_IMMUTABLE, be explicitly specified.
+ * This checker verifies that one of these mutability flags are used when
+ * creating PendingIntents.
+ */
+@AutoService(BugChecker.class)
+@BugPattern(
+        name = "AndroidFrameworkPendingIntentMutability",
+        summary = "Verifies that FLAG_MUTABLE or FLAG_IMMUTABLE is always set",
+        severity = WARNING)
+public final class PendingIntentMutabilityChecker extends BugChecker
+        implements MethodInvocationTreeMatcher {
+
+    private static final Matcher<ExpressionTree> PENDING_INTENT_METHOD = methodInvocation(
+            staticMethod()
+            .onClass("android.app.PendingIntent")
+            .withNameMatching(Pattern.compile(
+                    "^(getActivity|getActivityAsUser|getActivities|getActivitiesAsUser|"
+                    + "getBroadcast|getBroadcastAsUser|getService|getForegroundService).*")));
+
+    private static final Matcher<ExpressionTree> VALID_FLAGS = anyOf(
+            staticField("android.app.PendingIntent", "FLAG_MUTABLE"),
+            staticField("android.app.PendingIntent", "FLAG_IMMUTABLE"));
+
+    private static final Matcher<ExpressionTree> CONTAINS_VALID_FLAGS = contains(
+            ExpressionTree.class, VALID_FLAGS);
+
+    @Override
+    public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+        if (PENDING_INTENT_METHOD.matches(tree, state)) {
+            final ExpressionTree arg = tree.getArguments().get(3);
+            if (!(VALID_FLAGS.matches(arg, state) || CONTAINS_VALID_FLAGS.matches(arg, state))) {
+                return buildDescription(arg)
+                        .setMessage("To improve security, PendingIntents must declare one of"
+                                + " FLAG_MUTABLE or FLAG_IMMUTABLE explicitly; see"
+                                + " go/immutable-pendingintents for more details")
+                        .build();
+            }
+        }
+        return Description.NO_MATCH;
+    }
+}