PrivateKeyDetector.java

/*
 * Copyright (C) 2012 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.tools.lint.detector.api.Category;
import com.android.tools.lint.detector.api.Context;
import com.android.tools.lint.detector.api.Detector;
import com.android.tools.lint.detector.api.Issue;
import com.android.tools.lint.detector.api.LintUtils;
import com.android.tools.lint.detector.api.Location;
import com.android.tools.lint.detector.api.Project;
import com.android.tools.lint.detector.api.Scope;
import com.android.tools.lint.detector.api.Severity;
import com.android.tools.lint.detector.api.Speed;
import com.google.common.base.Charsets;
import com.google.common.io.Files;

import java.io.File;
import java.io.IOException;

/**
 * Looks for packaged private key files.
 */
public class PrivateKeyDetector extends Detector {
    /** Packaged private key files */
    public static final Issue ISSUE = Issue.create(
            "PackagedPrivateKey", //$NON-NLS-1$
            "Looks for packaged private key files",

            "In general, you should not package private key files inside your app.",

            Category.SECURITY,
            8,
            Severity.WARNING,
            PrivateKeyDetector.class,
            Scope.ALL_RESOURCES_SCOPE);

    /** Constructs a new {@link PrivateKeyDetector} check */
    public PrivateKeyDetector() {
    }

    private boolean isPrivateKeyFile(File file) {
        if (!file.isFile() ||
            (!LintUtils.endsWith(file.getPath(), "pem") && //NON-NLS-1$
             !LintUtils.endsWith(file.getPath(), "key"))) { //NON-NLS-1$
            return false;
        }

        try {
            String firstLine = Files.readFirstLine(file, Charsets.US_ASCII);
            return firstLine != null &&
                firstLine.startsWith("---") && //NON-NLS-1$
                firstLine.contains("PRIVATE KEY"); //NON-NLS-1$
        } catch (IOException ex) {
            // Don't care
        }

        return false;
    }

    private void checkFolder(Context context, File dir) {
        if (dir.isDirectory()) {
            File[] files = dir.listFiles();
            if (files != null) {
                for (File file : files) {
                    if (file.isDirectory()) {
                        checkFolder(context, file);
                    } else {
                        if (isPrivateKeyFile(file)) {
                            String fileName = file.getParentFile().getName() + File.separator
                                + file.getName();
                            String message = String.format(
                                "The %1$s file seems to be a private key file. " +
                                "Please make sure not to embed this in your APK file.", fileName);
                            context.report(ISSUE, Location.create(file), message, null);
                        }
                    }
                }
            }
        }
    }

    @Override
    public void afterCheckProject(@NonNull Context context) {
        if (!context.getProject().getReportIssues()) {
            // If this is a library project not being analyzed, ignore it
            return;
        }

        Project project = context.getProject();
        File projectFolder = project.getDir();

        checkFolder(context, new File(projectFolder, "res"));
        checkFolder(context, new File(projectFolder, "assets"));

        for (File srcFolder : project.getJavaSourceFolders()) {
            checkFolder(context, srcFolder);
        }
    }

    @Override
    public boolean appliesTo(@NonNull Context context, @NonNull File file) {
        return true;
    }

    @Override
    public @NonNull Speed getSpeed() {
        return Speed.NORMAL;
    }
}