lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/AllowAllHostnameVerifierDetector.java

/*
 * Copyright (C) 2015 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.android.tools.lint.checks;

import com.android.annotations.NonNull;
import com.android.annotations.Nullable;
import com.android.tools.lint.client.api.JavaEvaluator;
import com.android.tools.lint.detector.api.Category;
import com.android.tools.lint.detector.api.Detector;
import com.android.tools.lint.detector.api.Implementation;
import com.android.tools.lint.detector.api.Issue;
import com.android.tools.lint.detector.api.JavaContext;
import com.android.tools.lint.detector.api.Location;
import com.android.tools.lint.detector.api.Scope;
import com.android.tools.lint.detector.api.Severity;
import com.android.tools.lint.detector.api.SourceCodeScanner;
import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiField;
import com.intellij.psi.PsiMethod;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import org.jetbrains.uast.UCallExpression;
import org.jetbrains.uast.UExpression;
import org.jetbrains.uast.UastUtils;

public class AllowAllHostnameVerifierDetector extends Detector implements SourceCodeScanner {

    @SuppressWarnings("unchecked")
    private static final Implementation IMPLEMENTATION =
            new Implementation(AllowAllHostnameVerifierDetector.class, Scope.JAVA_FILE_SCOPE);

    public static final Issue ISSUE =
            Issue.create(
                            "AllowAllHostnameVerifier",
                            "Insecure HostnameVerifier",
                            "This check looks for use of HostnameVerifier implementations "
                                    + "whose `verify` method always returns true (thus trusting any hostname) "
                                    + "which could result in insecure network traffic caused by trusting arbitrary "
                                    + "hostnames in TLS/SSL certificates presented by peers.",
                            Category.SECURITY,
                            6,
                            Severity.WARNING,
                            IMPLEMENTATION)
                    .setAndroidSpecific(true);

    // ---- implements SourceCodeScanner ----

    @Override
    @Nullable
    @SuppressWarnings("javadoc")
    public List<String> getApplicableConstructorTypes() {
        return Collections.singletonList("org.apache.http.conn.ssl.AllowAllHostnameVerifier");
    }

    @Override
    public void visitConstructor(
            @NonNull JavaContext context,
            @NonNull UCallExpression node,
            @NonNull PsiMethod constructor) {
        Location location = context.getLocation(node);
        context.report(
                ISSUE,
                node,
                location,
                "Using the AllowAllHostnameVerifier HostnameVerifier is unsafe "
                        + "because it always returns true, which could cause insecure network "
                        + "traffic due to trusting TLS/SSL server certificates for wrong "
                        + "hostnames");
    }

    @Override
    public List<String> getApplicableMethodNames() {
        return Arrays.asList("setHostnameVerifier", "setDefaultHostnameVerifier");
    }

    @Override
    public void visitMethodCall(
            @NonNull JavaContext context,
            @NonNull UCallExpression node,
            @NonNull PsiMethod method) {
        JavaEvaluator evaluator = context.getEvaluator();
        if (evaluator.methodMatches(method, null, false, "javax.net.ssl.HostnameVerifier")) {
            UExpression argument = node.getValueArguments().get(0);
            PsiElement resolvedArgument = UastUtils.tryResolve(argument);
            if (resolvedArgument instanceof PsiField) {
                PsiField field = (PsiField) resolvedArgument;
                if ("ALLOW_ALL_HOSTNAME_VERIFIER".equals(field.getName())) {
                    Location location = context.getLocation(argument);
                    String message =
                            "Using the ALLOW_ALL_HOSTNAME_VERIFIER HostnameVerifier "
                                    + "is unsafe because it always returns true, which could cause "
                                    + "insecure network traffic due to trusting TLS/SSL server "
                                    + "certificates for wrong hostnames";
                    context.report(ISSUE, argument, location, message);
                }
            }
        }
    }
}