Add Digital Asset Links verification for postMessage API

chrome/android/java/src/org/chromium/chrome/browser/customtabs/OriginVerifier.java

Index: chrome/android/java/src/org/chromium/chrome/browser/customtabs/OriginVerifier.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/customtabs/OriginVerifier.java b/chrome/android/java/src/org/chromium/chrome/browser/customtabs/OriginVerifier.java
new file mode 100644
index 0000000000000000000000000000000000000000..bb06112596396d834c2eb19920528ab1dc714351
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/customtabs/OriginVerifier.java
@@ -0,0 +1,167 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.customtabs;
+
+import android.content.pm.PackageInfo;
+import android.content.pm.PackageManager;
+import android.net.Uri;
+import android.support.annotation.NonNull;
+
+import org.chromium.base.ContextUtils;
+import org.chromium.base.Log;
+import org.chromium.base.VisibleForTesting;
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+import org.chromium.chrome.browser.IntentHandler;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.cert.CertificateEncodingException;
+import java.security.cert.CertificateException;
+import java.security.cert.CertificateFactory;
+import java.security.cert.X509Certificate;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Used to verify postMessage origin for a designated package name.
+ *
+ * Uses Digital Asset Links to confirm that the given origin is associated with the package name as

[Benoit L, 2017/04/07 15:04:54]

nit: Add a comment about caching?

[Yusuf, 2017/04/07 23:38:41]

Done.

+ * a postMessage origin.
+ */
+@JNINamespace("customtabs")
+class OriginVerifier {
+    private static final String TAG = "OriginVerifier";
+    private static final char[] HEX_CHAR_LOOKUP = "0123456789ABCDEF".toCharArray();
+    private static Map<String, Uri> sCachedOriginMap;
+    private long mNativeOriginVerifier = 0;
+    private final OriginVerificationListener mListener;
+    private final String mPackageName;
+    private final String mSignatureFingerprint;
+    private Uri mOrigin;
+
+    /**
+     * To be used for prepopulating verified origin for testing functionality.
+     * @param packageName The package name to prepopulate for.
+     * @param origin The origin to add as verified.
+     */
+    @VisibleForTesting
+    static void prePopulateVerifiedOriginForTesting(String packageName, Uri origin) {
+        cacheVerifiedOriginIfNeeded(packageName, origin);
+    }
+
+    private static Uri getPostMessageOriginFromVerifiedOrigin(
+            String packageName, Uri verifiedOrigin) {
+        return Uri.parse(IntentHandler.ANDROID_APP_REFERRER_SCHEME + "://"
+                + verifiedOrigin.getHost() + packageName);
+    }
+
+    private static void cacheVerifiedOriginIfNeeded(String packageName, Uri origin) {
+        if (sCachedOriginMap == null) sCachedOriginMap = new HashMap<>();
+        if (!sCachedOriginMap.containsKey(packageName)) {
+            sCachedOriginMap.put(packageName, origin);
+        }
+    }
+
+    private Uri getCachedOriginIfExists() {
+        if (sCachedOriginMap == null) return null;
+        return sCachedOriginMap.get(mPackageName);
+    }
+
+    public interface OriginVerificationListener {
+        void onOriginVerified(String packageName, Uri origin, boolean result);
+    }
+
+    /**
+     * Main constructor.
+     * Use {@link OriginVerifier#start(Uri)}
+     * @param listener The listener who will get the verification result.
+     * @param packageName The package for the Android application for verification.
+     */
+    public OriginVerifier(OriginVerificationListener listener, String packageName) {
+        mListener = listener;
+        mPackageName = packageName;
+        mSignatureFingerprint = getCertificateSHA256FingerprintForPackage(mPackageName);
+    }
+
+    /**
+     * Verify the claimed origin for the cached package name asynchronously.
+     * @param origin The postMessage origin the application is claiming to have. Can't be null
+     */
+    public void start(@NonNull Uri origin) {
+        mOrigin = origin;
+
+        // If this origin is cached as verified already, use that.
+        Uri cachedOrigin = getCachedOriginIfExists();
+        if (cachedOrigin != null && cachedOrigin.equals(origin)) {
+            originVerified(true);
+            return;
+        }
+
+        if (mNativeOriginVerifier != 0) cleanUp();
+        mNativeOriginVerifier = nativeInit();
+        if (mNativeOriginVerifier == 0) return;
+        nativeVerifyOrigin(
+                mNativeOriginVerifier, mPackageName, mSignatureFingerprint, mOrigin.toString());
+    }
+
+    private void cleanUp() {
+        nativeDestroy(mNativeOriginVerifier);
+        mNativeOriginVerifier = 0;
+    }
+
+    private String getCertificateSHA256FingerprintForPackage(String packageName) {
+        PackageManager pm = ContextUtils.getApplicationContext().getPackageManager();
+        PackageInfo packageInfo = null;
+        try {
+            packageInfo = pm.getPackageInfo(packageName, PackageManager.GET_SIGNATURES);
+        } catch (PackageManager.NameNotFoundException e) {
+            return null;
+        }
+        InputStream input = new ByteArrayInputStream(packageInfo.signatures[0].toByteArray());
+        X509Certificate certificate = null;
+        String hexString = null;
+        try {
+            certificate =
+                    (X509Certificate) CertificateFactory.getInstance("X509").generateCertificate(
+                            input);
+            hexString = byteArrayToHexString(
+                    MessageDigest.getInstance("SHA256").digest(certificate.getEncoded()));
+        } catch (CertificateException | NoSuchAlgorithmException e) {
+            if (e instanceof CertificateEncodingException) {

[Benoit L, 2017/04/07 15:04:54]

You can put multiple catch blocks, provided that the first one is for the
derived exception, not the base one.
Seems cleaner than using instanceof.

[Yusuf, 2017/04/07 23:38:41]

Done.

+                Log.w(TAG, "Certificate type X509 encoding failed");
+            }
+            return null;
+        }
+        return hexString;
+    }
+
+    private static String byteArrayToHexString(byte[] byteArray) {
+        StringBuilder hexString = new StringBuilder(byteArray.length * 2);

[Benoit L, 2017/04/07 15:04:54]

This length computation doesn't account for the delimiter.
Should it be 
byteArray.length * 3 - 1
?

[Yusuf, 2017/04/07 23:38:41]

Done.

+        for (int i = 0; i < byteArray.length; ++i) {
+            hexString.append(HEX_CHAR_LOOKUP[(byteArray[i] & 0xf0) >>> 4]);
+            hexString.append(HEX_CHAR_LOOKUP[byteArray[i] & 0xf]);
+            if (i < (byteArray.length - 1)) hexString.append(':');
+        }
+        return hexString.toString();
+    }
+
+    @CalledByNative
+    private void originVerified(boolean originVerified) {
+        if (originVerified) {
+            cacheVerifiedOriginIfNeeded(mPackageName, mOrigin);
+            mOrigin = getPostMessageOriginFromVerifiedOrigin(mPackageName, mOrigin);
+        }
+        mListener.onOriginVerified(mPackageName, mOrigin, originVerified);
+        cleanUp();
+    }
+
+    private native long nativeInit();
+    private native void nativeVerifyOrigin(long nativeOriginVerifier, String packageName,
+            String signatureFingerprint, String origin);
+    private native void nativeDestroy(long nativeOriginVerifier);
+}