Add AndroidKeyStore provider for KeyStore API

This introduces a public API for the Android keystore that is accessible
via java.security.KeyStore API. This allows programs to store
PrivateKeyEntry and TrustedCertificateEntry items visible only to
themselves.

Future work should include:

* Implement KeyStore.CallbackHandlerProtection parameter to allow the
  caller to request that the keystore daemon unlock itself via the
  system password input dialog.

* Implement SecretKeyEntry once that support is in keystore daemon

Change-Id: I382ffdf742d3f9f7647c5f5a429244a340b6bb0a

1 files changed, 463 insertions, 0 deletions

diff --git a/keystore/java/android/security/AndroidKeyStore.java b/keystore/java/android/security/AndroidKeyStore.java
new file mode 100644
index 000000000000..a629f8dfa676
--- /dev/null
+++ b/keystore/java/android/security/AndroidKeyStore.java
@@ -0,0 +1,463 @@
+/*
+ * 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 android.security;
+
+import org.apache.harmony.xnet.provider.jsse.OpenSSLEngine;
+
+import android.util.Log;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.security.InvalidKeyException;
+import java.security.Key;
+import java.security.KeyStoreException;
+import java.security.KeyStoreSpi;
+import java.security.NoSuchAlgorithmException;
+import java.security.PrivateKey;
+import java.security.UnrecoverableKeyException;
+import java.security.cert.Certificate;
+import java.security.cert.CertificateEncodingException;
+import java.security.cert.CertificateException;
+import java.security.cert.CertificateFactory;
+import java.security.cert.X509Certificate;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Date;
+import java.util.Enumeration;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Set;
+
+/**
+ * A java.security.KeyStore interface for the Android KeyStore. This class is
+ * hidden from the Android API, but an instance of it can be created via the
+ * {@link java.security.KeyStore#getInstance(String)
+ * KeyStore.getInstance("AndroidKeyStore")} interface. This returns a
+ * java.security.KeyStore backed by this "AndroidKeyStore" implementation.
+ * <p>
+ * This is built on top of Android's keystore daemon. The convention of alias
+ * use is:
+ * <p>
+ * PrivateKeyEntry will have a Credentials.USER_PRIVATE_KEY as the private key,
+ * Credentials.USER_CERTIFICATE as the first certificate in the chain (the one
+ * that corresponds to the private key), and then a Credentials.CA_CERTIFICATE
+ * entry which will have the rest of the chain concatenated in BER format.
+ * <p>
+ * TrustedCertificateEntry will just have a Credentials.CA_CERTIFICATE entry
+ * with a single certificate.
+ *
+ * @hide
+ */
+public class AndroidKeyStore extends KeyStoreSpi {
+    public static final String NAME = "AndroidKeyStore";
+
+    private android.security.KeyStore mKeyStore;
+
+    @Override
+    public Key engineGetKey(String alias, char[] password) throws NoSuchAlgorithmException,
+            UnrecoverableKeyException {
+        if (!isKeyEntry(alias)) {
+            return null;
+        }
+
+        final OpenSSLEngine engine = OpenSSLEngine.getInstance("keystore");
+        try {
+            return engine.getPrivateKeyById(Credentials.USER_PRIVATE_KEY + alias);
+        } catch (InvalidKeyException e) {
+            UnrecoverableKeyException t = new UnrecoverableKeyException("Can't get key");
+            t.initCause(e);
+            throw t;
+        }
+    }
+
+    @Override
+    public Certificate[] engineGetCertificateChain(String alias) {
+        final X509Certificate leaf = (X509Certificate) engineGetCertificate(alias);
+        if (leaf == null) {
+            return null;
+        }
+
+        final Certificate[] caList;
+
+        final byte[] caBytes = mKeyStore.get(Credentials.CA_CERTIFICATE + alias);
+        if (caBytes != null) {
+            final Collection<X509Certificate> caChain = toCertificates(caBytes);
+
+            caList = new Certificate[caChain.size() + 1];
+
+            final Iterator<X509Certificate> it = caChain.iterator();
+            int i = 1;
+            while (it.hasNext()) {
+                caList[i++] = it.next();
+            }
+        } else {
+            caList = new Certificate[1];
+        }
+
+        caList[0] = leaf;
+
+        return caList;
+    }
+
+    @Override
+    public Certificate engineGetCertificate(String alias) {
+        byte[] certificate = mKeyStore.get(Credentials.USER_CERTIFICATE + alias);
+        if (certificate != null) {
+            return toCertificate(certificate);
+        }
+
+        certificate = mKeyStore.get(Credentials.CA_CERTIFICATE + alias);
+        if (certificate != null) {
+            return toCertificate(certificate);
+        }
+
+        return null;
+    }
+
+    private static X509Certificate toCertificate(byte[] bytes) {
+        try {
+            final CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
+            return (X509Certificate) certFactory
+                    .generateCertificate(new ByteArrayInputStream(bytes));
+        } catch (CertificateException e) {
+            Log.w(NAME, "Couldn't parse certificate in keystore", e);
+            return null;
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Collection<X509Certificate> toCertificates(byte[] bytes) {
+        try {
+            final CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
+            return (Collection<X509Certificate>) certFactory
+                    .generateCertificates(new ByteArrayInputStream(bytes));
+        } catch (CertificateException e) {
+            Log.w(NAME, "Couldn't parse certificates in keystore", e);
+            return new ArrayList<X509Certificate>();
+        }
+    }
+
+    private Date getModificationDate(String alias) {
+        final long epochMillis = mKeyStore.getmtime(alias);
+        if (epochMillis == -1L) {
+            return null;
+        }
+
+        return new Date(epochMillis);
+    }
+
+    @Override
+    public Date engineGetCreationDate(String alias) {
+        Date d = getModificationDate(Credentials.USER_PRIVATE_KEY + alias);
+        if (d != null) {
+            return d;
+        }
+
+        d = getModificationDate(Credentials.USER_CERTIFICATE + alias);
+        if (d != null) {
+            return d;
+        }
+
+        return getModificationDate(Credentials.CA_CERTIFICATE + alias);
+    }
+
+    @Override
+    public void engineSetKeyEntry(String alias, Key key, char[] password, Certificate[] chain)
+            throws KeyStoreException {
+        if ((password != null) && (password.length > 0)) {
+            throw new KeyStoreException("entries cannot be protected with passwords");
+        }
+
+        if (key instanceof PrivateKey) {
+            setPrivateKeyEntry(alias, (PrivateKey) key, chain);
+        } else {
+            throw new KeyStoreException("Only PrivateKeys are supported");
+        }
+    }
+
+    private void setPrivateKeyEntry(String alias, PrivateKey key, Certificate[] chain)
+            throws KeyStoreException {
+        // Make sure the PrivateKey format is the one we support.
+        final String keyFormat = key.getFormat();
+        if ((keyFormat == null) || (!"PKCS#8".equals(keyFormat))) {
+            throw new KeyStoreException(
+                    "Only PrivateKeys that can be encoded into PKCS#8 are supported");
+        }
+
+        // Make sure we can actually encode the key.
+        final byte[] keyBytes = key.getEncoded();
+        if (keyBytes == null) {
+            throw new KeyStoreException("PrivateKey has no encoding");
+        }
+
+        // Make sure the chain exists since this is a PrivateKey
+        if ((chain == null) || (chain.length == 0)) {
+            throw new KeyStoreException("Must supply at least one Certificate with PrivateKey");
+        }
+
+        // Do chain type checking.
+        X509Certificate[] x509chain = new X509Certificate[chain.length];
+        for (int i = 0; i < chain.length; i++) {
+            if (!"X.509".equals(chain[i].getType())) {
+                throw new KeyStoreException("Certificates must be in X.509 format: invalid cert #"
+                        + i);
+            }
+
+            if (!(chain[i] instanceof X509Certificate)) {
+                throw new KeyStoreException("Certificates must be in X.509 format: invalid cert #"
+                        + i);
+            }
+
+            x509chain[i] = (X509Certificate) chain[i];
+        }
+
+        final byte[] userCertBytes;
+        try {
+            userCertBytes = x509chain[0].getEncoded();
+        } catch (CertificateEncodingException e) {
+            throw new KeyStoreException("Couldn't encode certificate #1", e);
+        }
+
+        /*
+         * If we have a chain, store it in the CA certificate slot for this
+         * alias as concatenated DER-encoded certificates. These can be
+         * deserialized by {@link CertificateFactory#generateCertificates}.
+         */
+        final byte[] chainBytes;
+        if (chain.length > 1) {
+            /*
+             * The chain is passed in as {user_cert, ca_cert_1, ca_cert_2, ...}
+             * so we only need the certificates starting at index 1.
+             */
+            final byte[][] certsBytes = new byte[x509chain.length - 1][];
+            int totalCertLength = 0;
+            for (int i = 0; i < certsBytes.length; i++) {
+                try {
+                    certsBytes[i] = x509chain[i + 1].getEncoded();
+                    totalCertLength += certsBytes[i].length;
+                } catch (CertificateEncodingException e) {
+                    throw new KeyStoreException("Can't encode Certificate #" + i, e);
+                }
+            }
+
+            /*
+             * Serialize this into one byte array so we can later call
+             * CertificateFactory#generateCertificates to recover them.
+             */
+            chainBytes = new byte[totalCertLength];
+            int outputOffset = 0;
+            for (int i = 0; i < certsBytes.length; i++) {
+                final int certLength = certsBytes[i].length;
+                System.arraycopy(certsBytes[i], 0, chainBytes, outputOffset, certLength);
+                outputOffset += certLength;
+                certsBytes[i] = null;
+            }
+        } else {
+            chainBytes = null;
+        }
+
+        /*
+         * Make sure we clear out all the types we know about before trying to
+         * write.
+         */
+        deleteAllTypesForAlias(alias);
+
+        if (!mKeyStore.importKey(Credentials.USER_PRIVATE_KEY + alias, keyBytes)) {
+            throw new KeyStoreException("Couldn't put private key in keystore");
+        } else if (!mKeyStore.put(Credentials.USER_CERTIFICATE + alias, userCertBytes)) {
+            throw new KeyStoreException("Couldn't put certificate #1 in keystore");
+        } else if (chainBytes != null
+                && !mKeyStore.put(Credentials.CA_CERTIFICATE + alias, chainBytes)) {
+            throw new KeyStoreException("Couldn't put certificate chain in keystore");
+        }
+    }
+
+    @Override
+    public void engineSetKeyEntry(String alias, byte[] userKey, Certificate[] chain)
+            throws KeyStoreException {
+        throw new RuntimeException("Operation not supported because key encoding is unknown");
+    }
+
+    @Override
+    public void engineSetCertificateEntry(String alias, Certificate cert) throws KeyStoreException {
+        if (isKeyEntry(alias)) {
+            throw new KeyStoreException("Entry exists and is not a trusted certificate");
+        }
+
+        final byte[] encoded;
+        try {
+            encoded = cert.getEncoded();
+        } catch (CertificateEncodingException e) {
+            throw new KeyStoreException(e);
+        }
+
+        if (!mKeyStore.put(Credentials.CA_CERTIFICATE + alias, encoded)) {
+            throw new KeyStoreException("Couldn't insert certificate; is KeyStore initialized?");
+        }
+    }
+
+    @Override
+    public void engineDeleteEntry(String alias) throws KeyStoreException {
+        if (!deleteAllTypesForAlias(alias)) {
+            throw new KeyStoreException("No such entry " + alias);
+        }
+    }
+
+    /**
+     * Delete all types (private key, certificate, CA certificate) for a
+     * particular {@code alias}. All three can exist for any given alias.
+     * Returns {@code true} if there was at least one of those types.
+     */
+    private boolean deleteAllTypesForAlias(String alias) {
+        /*
+         * Make sure every type is deleted. There can be all three types, so
+         * don't use a conditional here.
+         */
+        return mKeyStore.delKey(Credentials.USER_PRIVATE_KEY + alias)
+                | mKeyStore.delete(Credentials.USER_CERTIFICATE + alias)
+                | mKeyStore.delete(Credentials.CA_CERTIFICATE + alias);
+    }
+
+    private Set<String> getUniqueAliases() {
+        final String[] rawAliases = mKeyStore.saw("");
+        if (rawAliases == null) {
+            return new HashSet<String>();
+        }
+
+        final Set<String> aliases = new HashSet<String>(rawAliases.length);
+        for (String alias : rawAliases) {
+            final int idx = alias.indexOf('_');
+            if ((idx == -1) || (alias.length() <= idx)) {
+                Log.e(NAME, "invalid alias: " + alias);
+                continue;
+            }
+
+            aliases.add(new String(alias.substring(idx + 1)));
+        }
+
+        return aliases;
+    }
+
+    @Override
+    public Enumeration<String> engineAliases() {
+        return Collections.enumeration(getUniqueAliases());
+    }
+
+    @Override
+    public boolean engineContainsAlias(String alias) {
+        return mKeyStore.contains(Credentials.USER_PRIVATE_KEY + alias)
+                || mKeyStore.contains(Credentials.USER_CERTIFICATE + alias)
+                || mKeyStore.contains(Credentials.CA_CERTIFICATE + alias);
+    }
+
+    @Override
+    public int engineSize() {
+        return getUniqueAliases().size();
+    }
+
+    @Override
+    public boolean engineIsKeyEntry(String alias) {
+        return isKeyEntry(alias);
+    }
+
+    private boolean isKeyEntry(String alias) {
+        return mKeyStore.contains(Credentials.USER_PRIVATE_KEY + alias);
+    }
+
+    @Override
+    public boolean engineIsCertificateEntry(String alias) {
+        return !isKeyEntry(alias) && mKeyStore.contains(Credentials.CA_CERTIFICATE + alias);
+    }
+
+    @Override
+    public String engineGetCertificateAlias(Certificate cert) {
+        if (cert == null) {
+            return null;
+        }
+
+        final Set<String> nonCaEntries = new HashSet<String>();
+
+        /*
+         * First scan the PrivateKeyEntry types. The KeyStoreSpi documentation
+         * says to only compare the first certificate in the chain which is
+         * equivalent to the USER_CERTIFICATE prefix for the Android keystore
+         * convention.
+         */
+        final String[] certAliases = mKeyStore.saw(Credentials.USER_CERTIFICATE);
+        for (String alias : certAliases) {
+            final byte[] certBytes = mKeyStore.get(Credentials.USER_CERTIFICATE + alias);
+            if (certBytes == null) {
+                continue;
+            }
+
+            final Certificate c = toCertificate(certBytes);
+            nonCaEntries.add(alias);
+
+            if (cert.equals(c)) {
+                return alias;
+            }
+        }
+
+        /*
+         * Look at all the TrustedCertificateEntry types. Skip all the
+         * PrivateKeyEntry we looked at above.
+         */
+        final String[] caAliases = mKeyStore.saw(Credentials.CA_CERTIFICATE);
+        for (String alias : caAliases) {
+            if (nonCaEntries.contains(alias)) {
+                continue;
+            }
+
+            final byte[] certBytes = mKeyStore.get(Credentials.CA_CERTIFICATE + alias);
+            if (certBytes == null) {
+                continue;
+            }
+
+            final Certificate c = toCertificate(mKeyStore.get(Credentials.CA_CERTIFICATE + alias));
+            if (cert.equals(c)) {
+                return alias;
+            }
+        }
+
+        return null;
+    }
+
+    @Override
+    public void engineStore(OutputStream stream, char[] password) throws IOException,
+            NoSuchAlgorithmException, CertificateException {
+        throw new UnsupportedOperationException("Can not serialize AndroidKeyStore to OutputStream");
+    }
+
+    @Override
+    public void engineLoad(InputStream stream, char[] password) throws IOException,
+            NoSuchAlgorithmException, CertificateException {
+        if (stream != null) {
+            throw new IllegalArgumentException("InputStream not supported");
+        }
+
+        if (password != null) {
+            throw new IllegalArgumentException("password not supported");
+        }
+
+        // Unfortunate name collision.
+        mKeyStore = android.security.KeyStore.getInstance();
+    }
+
+}