root/net/android/java/src/org/chromium/net/X509Util.java

DEFINITIONS

1. JNINamespace
2. onReceive
3. checkServerTrusted
4. checkServerTrusted
5. SuppressLint
6. checkServerTrusted
7. ensureInitialized
8. buildSystemTrustRootSet
9. createTrustManager
10. reloadTestTrustManager
11. reloadDefaultTrustManager
12. createCertificateFromBytes
13. addTestRootCertificate
14. clearTestRootCertificates
15. verifyKeyUsage
16. verifyServerCertificates
17. setDisableNativeCodeForTest
18. nativeNotifyKeyChainChanged
19. nativeRecordCertVerifyCapabilitiesHistogram
20. nativeGetApplicationContext

// 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.IOException;
import java.security.KeyStore;
import java.security.KeyStoreException;
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.Enumeration;
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;

    /**
     * Hash set of the subject and public key of system roots. This is used to
     * determine whether a chain ends at a well-known root or not.
     *
     * Querying the system KeyStore for the root directly doesn't work as the
     * root of the verified chain may be the server's version of a root rather
     * than the system one. For instance, the server may send a certificate
     * signed by another CA, while the system store contains a self-signed root
     * with the same subject and SPKI.  The chain will terminate at that root
     * but X509TrustManagerExtensions will return the server's version.
     */
    private static Set<Pair<X500Principal, PublicKey>> sSystemTrustRoots;

    /**
     * True if the system trust roots were initialized. (sSystemTrustRoots may
     * still be null if system trust roots cannot be distinguished from
     * user-installed ones.)
     */
    private static boolean sLoadedSystemTrustRoots;

    /**
     * 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 (!sLoadedSystemTrustRoots) {
                try {
                    sSystemTrustRoots = buildSystemTrustRootSet();
                } catch (KeyStoreException e) {
                    // If the device does not have an "AndroidCAStore" KeyStore, don't make the
                    // failure fatal. Instead default conservatively to setting isIssuedByKnownRoot
                    // to false everywhere.
                    Log.w(TAG, "Could not load system trust root set", e);
                }
                if (!sDisableNativeCodeForTest)
                    nativeRecordCertVerifyCapabilitiesHistogram(sSystemTrustRoots != null);
                sLoadedSystemTrustRoots = true;
            }
            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));
            }
        }
    }

    private static Set<Pair<X500Principal, PublicKey>> buildSystemTrustRootSet() throws
            CertificateException, KeyStoreException, NoSuchAlgorithmException {
        // Load the Android CA store.
        KeyStore systemKeyStore = KeyStore.getInstance("AndroidCAStore");
        try {
            systemKeyStore.load(null);
        } catch (IOException e) {
            // No IO operation is attempted.
        }

        // System trust roots have prefix of "system:".
        Set<Pair<X500Principal, PublicKey>> roots = new HashSet<Pair<X500Principal, PublicKey>>();
        Enumeration<String> aliases = systemKeyStore.aliases();
        while (aliases.hasMoreElements()) {
            String alias = aliases.nextElement();
            if (!alias.startsWith("system:"))
                continue;
            Certificate cert = systemKeyStore.getCertificate(alias);
            if (cert != null && cert instanceof X509Certificate) {
                X509Certificate x509Cert = (X509Certificate)cert;
                roots.add(new Pair<X500Principal, PublicKey>(x509Cert.getSubjectX500Principal(),
                                                             x509Cert.getPublicKey()));
            }
        }
        return roots;
    }

    /**
     * Creates a X509TrustManagerImplementation backed up by the given key
     * store. When null is passed as a key store, system default trust store is
     * used.
     * @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) {
                    Log.e(TAG, "Error creating trust manager: " + e);
                }
            }
        }
        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;
        sSystemTrustRoots = null;
        sLoadedSystemTrustRoots = false;
        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.
            }
        }
    }

    /**
     * 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) {
            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 (sSystemTrustRoots != null && verifiedChain.size() > 0) {
                X509Certificate root = verifiedChain.get(verifiedChain.size() - 1);
                isIssuedByKnownRoot = sSystemTrustRoots.contains(
                        new Pair<X500Principal, PublicKey>(root.getSubjectX500Principal(),
                                                           root.getPublicKey()));
            }

            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();

}