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// Copyright 2012 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.net;
import android.annotation.SuppressLint;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.http.X509TrustManagerExtensions;
import android.os.Build;
import android.security.KeyChain;
import android.util.Log;
import android.util.Pair;
import org.chromium.base.JNINamespace;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.IOException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.CertificateExpiredException;
import java.security.cert.CertificateFactory;
import java.security.cert.CertificateNotYetValidException;
import java.security.cert.X509Certificate;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;
import javax.security.auth.x500.X500Principal;
/**
* Utility functions for verifying X.509 certificates.
*/
@JNINamespace("net")
public class X509Util {
private static final String TAG = "X509Util";
private static final class TrustStorageListener extends BroadcastReceiver {
@Override public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals(KeyChain.ACTION_STORAGE_CHANGED)) {
try {
reloadDefaultTrustManager();
}
catch (CertificateException e) {
Log.e(TAG, "Unable to reload the default TrustManager", e);
}
catch (KeyStoreException e) {
Log.e(TAG, "Unable to reload the default TrustManager", e);
}
catch (NoSuchAlgorithmException e) {
Log.e(TAG, "Unable to reload the default TrustManager", e);
}
}
}
}
/**
* Interface that wraps one of X509TrustManager or
* X509TrustManagerExtensions to support platforms before the latter was
* added.
*/
private static interface X509TrustManagerImplementation {
public List<X509Certificate> checkServerTrusted(X509Certificate[] chain,
String authType,
String host) throws CertificateException;
}
private static final class X509TrustManagerIceCreamSandwich implements
X509TrustManagerImplementation {
private final X509TrustManager mTrustManager;
public X509TrustManagerIceCreamSandwich(X509TrustManager trustManager) {
mTrustManager = trustManager;
}
@Override
public List<X509Certificate> checkServerTrusted(X509Certificate[] chain,
String authType,
String host) throws CertificateException {
mTrustManager.checkServerTrusted(chain, authType);
return Collections.<X509Certificate>emptyList();
}
}
private static final class X509TrustManagerJellyBean implements X509TrustManagerImplementation {
private final X509TrustManagerExtensions mTrustManagerExtensions;
@SuppressLint("NewApi")
public X509TrustManagerJellyBean(X509TrustManager trustManager) {
mTrustManagerExtensions = new X509TrustManagerExtensions(trustManager);
}
@Override
public List<X509Certificate> checkServerTrusted(X509Certificate[] chain,
String authType,
String host) throws CertificateException {
return mTrustManagerExtensions.checkServerTrusted(chain, authType, host);
}
}
private static CertificateFactory sCertificateFactory;
private static final String OID_TLS_SERVER_AUTH = "1.3.6.1.5.5.7.3.1";
private static final String OID_ANY_EKU = "2.5.29.37.0";
// Server-Gated Cryptography (necessary to support a few legacy issuers):
// Netscape:
private static final String OID_SERVER_GATED_NETSCAPE = "2.16.840.1.113730.4.1";
// Microsoft:
private static final String OID_SERVER_GATED_MICROSOFT = "1.3.6.1.4.1.311.10.3.3";
/**
* Trust manager backed up by the read-only system certificate store.
*/
private static X509TrustManagerImplementation sDefaultTrustManager;
/**
* BroadcastReceiver that listens to change in the system keystore to invalidate certificate
* caches.
*/
private static TrustStorageListener sTrustStorageListener;
/**
* Trust manager backed up by a custom certificate store. We need such manager to plant test
* root CA to the trust store in testing.
*/
private static X509TrustManagerImplementation sTestTrustManager;
private static KeyStore sTestKeyStore;
/**
* The system key store. This is used to determine whether a trust anchor is a system trust
* anchor or user-installed.
*/
private static KeyStore sSystemKeyStore;
/**
* The directory where system certificates are stored. This is used to determine whether a
* trust anchor is a system trust anchor or user-installed. The KeyStore API alone is not
* sufficient to efficiently query whether a given X500Principal, PublicKey pair is a trust
* anchor.
*/
private static File sSystemCertificateDirectory;
/**
* An in-memory cache of which trust anchors are system trust roots. This avoids reading and
* decoding the root from disk on every verification. Mirrors a similar in-memory cache in
* Conscrypt's X509TrustManager implementation.
*/
private static Set<Pair<X500Principal, PublicKey>> sSystemTrustAnchorCache;
/**
* True if the system key store has been loaded. If the "AndroidCAStore" KeyStore instance
* was not found, sSystemKeyStore may be null while sLoadedSystemKeyStore is true.
*/
private static boolean sLoadedSystemKeyStore;
/**
* Lock object used to synchronize all calls that modify or depend on the trust managers.
*/
private static final Object sLock = new Object();
/**
* Allow disabling registering the observer and recording histograms for the certificate
* changes. Net unit tests do not load native libraries which prevent this to succeed. Moreover,
* the system does not allow to interact with the certificate store without user interaction.
*/
private static boolean sDisableNativeCodeForTest = false;
/**
* Ensures that the trust managers and certificate factory are initialized.
*/
private static void ensureInitialized() throws CertificateException,
KeyStoreException, NoSuchAlgorithmException {
synchronized (sLock) {
if (sCertificateFactory == null) {
sCertificateFactory = CertificateFactory.getInstance("X.509");
}
if (sDefaultTrustManager == null) {
sDefaultTrustManager = X509Util.createTrustManager(null);
}
if (!sLoadedSystemKeyStore) {
try {
sSystemKeyStore = KeyStore.getInstance("AndroidCAStore");
try {
sSystemKeyStore.load(null);
} catch (IOException e) {
// No IO operation is attempted.
}
sSystemCertificateDirectory =
new File(System.getenv("ANDROID_ROOT") + "/etc/security/cacerts");
} catch (KeyStoreException e) {
// Could not load AndroidCAStore. Continue anyway; isKnownRoot will always
// return false.
}
if (!sDisableNativeCodeForTest)
nativeRecordCertVerifyCapabilitiesHistogram(sSystemKeyStore != null);
sLoadedSystemKeyStore = true;
}
if (sSystemTrustAnchorCache == null) {
sSystemTrustAnchorCache = new HashSet<Pair<X500Principal, PublicKey>>();
}
if (sTestKeyStore == null) {
sTestKeyStore = KeyStore.getInstance(KeyStore.getDefaultType());
try {
sTestKeyStore.load(null);
} catch (IOException e) {
// No IO operation is attempted.
}
}
if (sTestTrustManager == null) {
sTestTrustManager = X509Util.createTrustManager(sTestKeyStore);
}
if (!sDisableNativeCodeForTest && sTrustStorageListener == null) {
sTrustStorageListener = new TrustStorageListener();
nativeGetApplicationContext().registerReceiver(sTrustStorageListener,
new IntentFilter(KeyChain.ACTION_STORAGE_CHANGED));
}
}
}
/**
* Creates a X509TrustManagerImplementation backed up by the given key
* store. When null is passed as a key store, system default trust store is
* used. Returns null if no created TrustManager was suitable.
* @throws KeyStoreException, NoSuchAlgorithmException on error initializing the TrustManager.
*/
private static X509TrustManagerImplementation createTrustManager(KeyStore keyStore) throws
KeyStoreException, NoSuchAlgorithmException {
String algorithm = TrustManagerFactory.getDefaultAlgorithm();
TrustManagerFactory tmf = TrustManagerFactory.getInstance(algorithm);
tmf.init(keyStore);
for (TrustManager tm : tmf.getTrustManagers()) {
if (tm instanceof X509TrustManager) {
try {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
return new X509TrustManagerJellyBean((X509TrustManager) tm);
} else {
return new X509TrustManagerIceCreamSandwich((X509TrustManager) tm);
}
} catch (IllegalArgumentException e) {
String className = tm.getClass().getName();
Log.e(TAG, "Error creating trust manager (" + className + "): " + e);
}
}
}
Log.e(TAG, "Could not find suitable trust manager");
return null;
}
/**
* After each modification of test key store, trust manager has to be generated again.
*/
private static void reloadTestTrustManager() throws KeyStoreException,
NoSuchAlgorithmException {
sTestTrustManager = X509Util.createTrustManager(sTestKeyStore);
}
/**
* After each modification by the system of the key store, trust manager has to be regenerated.
*/
private static void reloadDefaultTrustManager() throws KeyStoreException,
NoSuchAlgorithmException, CertificateException {
sDefaultTrustManager = null;
sSystemTrustAnchorCache = null;
nativeNotifyKeyChainChanged();
ensureInitialized();
}
/**
* Convert a DER encoded certificate to an X509Certificate.
*/
public static X509Certificate createCertificateFromBytes(byte[] derBytes) throws
CertificateException, KeyStoreException, NoSuchAlgorithmException {
ensureInitialized();
return (X509Certificate) sCertificateFactory.generateCertificate(
new ByteArrayInputStream(derBytes));
}
public static void addTestRootCertificate(byte[] rootCertBytes) throws CertificateException,
KeyStoreException, NoSuchAlgorithmException {
ensureInitialized();
X509Certificate rootCert = createCertificateFromBytes(rootCertBytes);
synchronized (sLock) {
sTestKeyStore.setCertificateEntry(
"root_cert_" + Integer.toString(sTestKeyStore.size()), rootCert);
reloadTestTrustManager();
}
}
public static void clearTestRootCertificates() throws NoSuchAlgorithmException,
CertificateException, KeyStoreException {
ensureInitialized();
synchronized (sLock) {
try {
sTestKeyStore.load(null);
reloadTestTrustManager();
} catch (IOException e) {
// No IO operation is attempted.
}
}
}
private static final char[] HEX_DIGITS = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'a', 'b', 'c', 'd', 'e', 'f',
};
private static String hashPrincipal(X500Principal principal) throws NoSuchAlgorithmException {
// Android hashes a principal as the first four bytes of its MD5 digest, encoded in
// lowercase hex and reversed. Verified in 4.2, 4.3, and 4.4.
byte[] digest = MessageDigest.getInstance("MD5").digest(principal.getEncoded());
char[] hexChars = new char[8];
for (int i = 0; i < 4; i++) {
hexChars[2 * i] = HEX_DIGITS[(digest[3 - i] >> 4) & 0xf];
hexChars[2 * i + 1] = HEX_DIGITS[digest[3 - i] & 0xf];
}
return new String(hexChars);
}
private static boolean isKnownRoot(X509Certificate root)
throws NoSuchAlgorithmException, KeyStoreException {
// Could not find the system key store. Conservatively report false.
if (sSystemKeyStore == null)
return false;
// Check the in-memory cache first; avoid decoding the anchor from disk
// if it has been seen before.
Pair<X500Principal, PublicKey> key =
new Pair<X500Principal, PublicKey>(root.getSubjectX500Principal(), root.getPublicKey());
if (sSystemTrustAnchorCache.contains(key))
return true;
// Note: It is not sufficient to call sSystemKeyStore.getCertificiateAlias. If the server
// supplies a copy of a trust anchor, X509TrustManagerExtensions returns the server's
// version rather than the system one. getCertificiateAlias will then fail to find an anchor
// name. This is fixed upstream in https://android-review.googlesource.com/#/c/91605/
//
// TODO(davidben): When the change trickles into an Android release, query sSystemKeyStore
// directly.
// System trust anchors are stored under a hash of the principal. In case of collisions,
// a number is appended.
String hash = hashPrincipal(root.getSubjectX500Principal());
for (int i = 0; true; i++) {
String alias = hash + '.' + i;
if (!new File(sSystemCertificateDirectory, alias).exists())
break;
Certificate anchor = sSystemKeyStore.getCertificate("system:" + alias);
// It is possible for this to return null if the user deleted a trust anchor. In
// that case, the certificate remains in the system directory but is also added to
// another file. Continue iterating as there may be further collisions after the
// deleted anchor.
if (anchor == null)
continue;
if (!(anchor instanceof X509Certificate)) {
// This should never happen.
String className = anchor.getClass().getName();
Log.e(TAG, "Anchor " + alias + " not an X509Certificate: " + className);
continue;
}
// If the subject and public key match, this is a system root.
X509Certificate anchorX509 = (X509Certificate)anchor;
if (root.getSubjectX500Principal().equals(anchorX509.getSubjectX500Principal()) &&
root.getPublicKey().equals(anchorX509.getPublicKey())) {
sSystemTrustAnchorCache.add(key);
return true;
}
}
return false;
}
/**
* If an EKU extension is present in the end-entity certificate, it MUST contain either the
* anyEKU or serverAuth or netscapeSGC or Microsoft SGC EKUs.
*
* @return true if there is no EKU extension or if any of the EKU extensions is one of the valid
* OIDs for web server certificates.
*
* TODO(palmer): This can be removed after the equivalent change is made to the Android default
* TrustManager and that change is shipped to a large majority of Android users.
*/
static boolean verifyKeyUsage(X509Certificate certificate) throws CertificateException {
List<String> ekuOids;
try {
ekuOids = certificate.getExtendedKeyUsage();
} catch (NullPointerException e) {
// getExtendedKeyUsage() can crash due to an Android platform bug. This probably
// happens when the EKU extension data is malformed so return false here.
// See http://crbug.com/233610
return false;
}
if (ekuOids == null)
return true;
for (String ekuOid : ekuOids) {
if (ekuOid.equals(OID_TLS_SERVER_AUTH) ||
ekuOid.equals(OID_ANY_EKU) ||
ekuOid.equals(OID_SERVER_GATED_NETSCAPE) ||
ekuOid.equals(OID_SERVER_GATED_MICROSOFT)) {
return true;
}
}
return false;
}
public static AndroidCertVerifyResult verifyServerCertificates(byte[][] certChain,
String authType,
String host)
throws KeyStoreException, NoSuchAlgorithmException {
if (certChain == null || certChain.length == 0 || certChain[0] == null) {
throw new IllegalArgumentException("Expected non-null and non-empty certificate " +
"chain passed as |certChain|. |certChain|=" + Arrays.deepToString(certChain));
}
try {
ensureInitialized();
} catch (CertificateException e) {
return new AndroidCertVerifyResult(CertVerifyStatusAndroid.VERIFY_FAILED);
}
X509Certificate[] serverCertificates = new X509Certificate[certChain.length];
try {
for (int i = 0; i < certChain.length; ++i) {
serverCertificates[i] = createCertificateFromBytes(certChain[i]);
}
} catch (CertificateException e) {
return new AndroidCertVerifyResult(CertVerifyStatusAndroid.VERIFY_UNABLE_TO_PARSE);
}
// Expired and not yet valid certificates would be rejected by the trust managers, but the
// trust managers report all certificate errors using the general CertificateException. In
// order to get more granular error information, cert validity time range is being checked
// separately.
try {
serverCertificates[0].checkValidity();
if (!verifyKeyUsage(serverCertificates[0])) {
return new AndroidCertVerifyResult(
CertVerifyStatusAndroid.VERIFY_INCORRECT_KEY_USAGE);
}
} catch (CertificateExpiredException e) {
return new AndroidCertVerifyResult(CertVerifyStatusAndroid.VERIFY_EXPIRED);
} catch (CertificateNotYetValidException e) {
return new AndroidCertVerifyResult(CertVerifyStatusAndroid.VERIFY_NOT_YET_VALID);
} catch (CertificateException e) {
return new AndroidCertVerifyResult(CertVerifyStatusAndroid.VERIFY_FAILED);
}
synchronized (sLock) {
// If no trust manager was found, fail without crashing on the null pointer.
if (sDefaultTrustManager == null)
return new AndroidCertVerifyResult(CertVerifyStatusAndroid.VERIFY_FAILED);
List<X509Certificate> verifiedChain;
try {
verifiedChain = sDefaultTrustManager.checkServerTrusted(serverCertificates,
authType, host);
} catch (CertificateException eDefaultManager) {
try {
verifiedChain = sTestTrustManager.checkServerTrusted(serverCertificates,
authType, host);
} catch (CertificateException eTestManager) {
// Neither of the trust managers confirms the validity of the certificate chain,
// log the error message returned by the system trust manager.
Log.i(TAG, "Failed to validate the certificate chain, error: " +
eDefaultManager.getMessage());
return new AndroidCertVerifyResult(
CertVerifyStatusAndroid.VERIFY_NO_TRUSTED_ROOT);
}
}
boolean isIssuedByKnownRoot = false;
if (verifiedChain.size() > 0) {
X509Certificate root = verifiedChain.get(verifiedChain.size() - 1);
isIssuedByKnownRoot = isKnownRoot(root);
}
return new AndroidCertVerifyResult(CertVerifyStatusAndroid.VERIFY_OK,
isIssuedByKnownRoot, verifiedChain);
}
}
public static void setDisableNativeCodeForTest(boolean disabled) {
sDisableNativeCodeForTest = disabled;
}
/**
* Notify the native net::CertDatabase instance that the system database has been updated.
*/
private static native void nativeNotifyKeyChainChanged();
/**
* Record histograms on the platform's certificate verification capabilities.
*/
private static native void nativeRecordCertVerifyCapabilitiesHistogram(
boolean foundSystemTrustRoots);
/**
* Returns the application context.
*/
private static native Context nativeGetApplicationContext();
}
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