Add TestRule to enable access to deprecated BC algorithms

Android restricts access to a number of deprecated BouncyCastle
algorithms to APKs that target SDK version <= 27. However, those
algorithms still need testing. Rather than set the target SDK version
to be <= 27 (which could have other side effects) tests use
Providers.setMaximumAllowableApiLevelForBcDeprecation(int) to raise
the level to make them accessible at the current target SDK version
and resets it the default value afterwards.

This change adds a JUnit test rule to implement that behavior and
uses it to replace duplicate setUp() and tearDown() code across a
number of tests. It also insulates the tests from having to access
the internal sun.security.jca.Providers and dalvik.system.VMRuntime
classes.

This is intended to be used by external/conscrypt so that the
conscrypt-tests module can stop depending on core-all-systems-module.

Bug: 141539296
Test: atest CtsLibcoreTestCases
Change-Id: If41b5c221c392e9b6d14d500537115d3380c4999

2 files changed, 127 insertions, 0 deletions

diff --git a/test-rules/src/main/java/libcore/junit/util/EnableDeprecatedBouncyCastleAlgorithmsRule.java b/test-rules/src/main/java/libcore/junit/util/EnableDeprecatedBouncyCastleAlgorithmsRule.java
new file mode 100644
index 0000000000..bfd45ef07c
--- /dev/null
+++ b/test-rules/src/main/java/libcore/junit/util/EnableDeprecatedBouncyCastleAlgorithmsRule.java
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2019 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 libcore.junit.util;
+
+import dalvik.system.VMRuntime;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.util.function.Supplier;
+import org.junit.rules.TestRule;
+import org.junit.runner.Description;
+import org.junit.runners.model.Statement;
+import sun.security.jca.Providers;
+
+/**
+ * Allows tests to temporarily enable deprecated BouncyCastle algorithms to verify that their
+ * behavior has not changed.
+ *
+ * <p>To use add the following to the test class.
+ *
+ * <pre>
+ * &#64;Rule
+ * public TestRule enableDeprecatedBCAlgorithmsRule =
+ *     EnableDeprecatedBouncyCastleAlgorithmsRule.getInstance();
+ * </pre>
+ *
+ * <p>It will give all test methods access to the deprecated algorithms.
+ */
+public class EnableDeprecatedBouncyCastleAlgorithmsRule implements TestRule {
+
+    private static final TestRule INSTANCE = new EnableDeprecatedBouncyCastleAlgorithmsRule();
+
+    public static TestRule getInstance() {
+        return INSTANCE;
+    }
+
+    private EnableDeprecatedBouncyCastleAlgorithmsRule() {
+    }
+
+    @Override
+    public Statement apply(final Statement statement, Description description) {
+        return new Statement() {
+            @Override
+            public void evaluate() throws Throwable {
+                int currentMaximum =
+                        Providers.getMaximumAllowableApiLevelForBcDeprecation();
+                try {
+                    int newMaximum = VMRuntime.getRuntime().getTargetSdkVersion();
+                    Providers.setMaximumAllowableApiLevelForBcDeprecation(newMaximum);
+                    statement.evaluate();
+                } finally {
+                    Providers.setMaximumAllowableApiLevelForBcDeprecation(currentMaximum);
+                }
+            }
+        };
+    }
+}
diff --git a/test-rules/src/test/java/libcore/junit/util/EnableDeprecatedBouncyCastleAlgorithmsRuleTest.java b/test-rules/src/test/java/libcore/junit/util/EnableDeprecatedBouncyCastleAlgorithmsRuleTest.java
new file mode 100644
index 0000000000..a08ed848c4
--- /dev/null
+++ b/test-rules/src/test/java/libcore/junit/util/EnableDeprecatedBouncyCastleAlgorithmsRuleTest.java
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2019 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 libcore.junit.util;
+
+import dalvik.system.VMRuntime;
+import libcore.junit.util.SwitchTargetSdkVersionRule.TargetSdkVersion;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.RuleChain;
+import org.junit.rules.TestRule;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+import sun.security.jca.Providers;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests for {@link EnableDeprecatedBouncyCastleAlgorithmsRule}.
+ */
+@RunWith(JUnit4.class)
+public class EnableDeprecatedBouncyCastleAlgorithmsRuleTest {
+
+    /**
+     * Chain the rules together so that changes to the target sdk version will be visible in the
+     * bouncy castle rules.
+     */
+    @Rule
+    public TestRule chain = RuleChain
+            .outerRule(SwitchTargetSdkVersionRule.getInstance())
+            .around(EnableDeprecatedBouncyCastleAlgorithmsRule.getInstance());
+
+    @Test
+    @TargetSdkVersion(23)
+    public void testRunningAsIfTargetedAtSDKVersion23() {
+        assertEquals(23, Providers.getMaximumAllowableApiLevelForBcDeprecation());
+    }
+
+    @Test
+    public void testRunningAsIfTargetedAtCurrentSDKVersion() {
+        assertEquals(VMRuntime.getRuntime().getTargetSdkVersion(),
+                Providers.getMaximumAllowableApiLevelForBcDeprecation());
+    }
+}