/*
* Copyright (C) 2008 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.net.http;
import android.os.SystemClock;
import android.security.Sha1MessageDigest;
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;
import java.security.cert.CertPath;
import java.security.GeneralSecurityException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Random;
/**
* Validator cache used to speed-up certificate chain validation. The idea is
* to keep each secure domain name associated with a cryptographically secure
* hash of the certificate chain successfully used to validate the domain. If
* we establish connection with the domain more than once and each time receive
* the same list of certificates, we do not have to re-validate.
*
* {@hide}
*/
class CertificateValidatorCache {
// TODO: debug only!
public static long mSave = 0;
public static long mCost = 0;
// TODO: debug only!
/**
* The cache-entry lifetime in milliseconds (here, 10 minutes)
*/
private static final long CACHE_ENTRY_LIFETIME = 10 * 60 * 1000;
/**
* The certificate factory
*/
private static CertificateFactory sCertificateFactory;
/**
* The certificate validator cache map (domain to a cache entry)
*/
private HashMap<Integer, CacheEntry> mCacheMap;
/**
* Random salt
*/
private int mBigScrew;
/**
* @param certificate The array of server certificates to compute a
* secure hash from
* @return The secure hash computed from server certificates
*/
public static byte[] secureHash(Certificate[] certificates) {
byte[] secureHash = null;
// TODO: debug only!
long beg = SystemClock.uptimeMillis();
// TODO: debug only!
if (certificates != null && certificates.length != 0) {
byte[] encodedCertPath = null;
try {
synchronized (CertificateValidatorCache.class) {
if (sCertificateFactory == null) {
try {
sCertificateFactory =
CertificateFactory.getInstance("X.509");
} catch(GeneralSecurityException e) {
if (HttpLog.LOGV) {
HttpLog.v("CertificateValidatorCache:" +
" failed to create the certificate factory");
}
}
}
}
CertPath certPath =
sCertificateFactory.generateCertPath(Arrays.asList(certificates));
if (certPath != null) {
encodedCertPath = certPath.getEncoded();
if (encodedCertPath != null) {
Sha1MessageDigest messageDigest =
new Sha1MessageDigest();
secureHash = messageDigest.digest(encodedCertPath);
}
}
} catch (GeneralSecurityException e) {}
}
// TODO: debug only!
long end = SystemClock.uptimeMillis();
mCost += (end - beg);
// TODO: debug only!
return secureHash;
}
/**
* Creates a new certificate-validator cache
*/
public CertificateValidatorCache() {
Random random = new Random();
mBigScrew = random.nextInt();
mCacheMap = new HashMap<Integer, CacheEntry>();
}
/**
* @param domain The domain to check against
* @param secureHash The secure hash to check against
* @return True iff there is a valid (not expired) cache entry
* associated with the domain and the secure hash
*/
public boolean has(String domain, byte[] secureHash) {
boolean rval = false;
if (domain != null && domain.length() != 0) {
if (secureHash != null && secureHash.length != 0) {
CacheEntry cacheEntry = (CacheEntry)mCacheMap.get(
new Integer(mBigScrew ^ domain.hashCode()));
if (cacheEntry != null) {
if (!cacheEntry.expired()) {
rval = cacheEntry.has(domain, secureHash);
// TODO: debug only!
if (rval) {
mSave += cacheEntry.mSave;
}
// TODO: debug only!
} else {
mCacheMap.remove(cacheEntry);
}
}
}
}
return rval;
}
/**
* Adds the (domain, secureHash) tuple to the cache
* @param domain The domain to be added to the cache
* @param secureHash The secure hash to be added to the cache
* @return True iff succeeds
*/
public boolean put(String domain, byte[] secureHash, long save) {
if (domain != null && domain.length() != 0) {
if (secureHash != null && secureHash.length != 0) {
mCacheMap.put(
new Integer(mBigScrew ^ domain.hashCode()),
new CacheEntry(domain, secureHash, save));
return true;
}
}
return false;
}
/**
* Certificate-validator cache entry. We have one per domain
*/
private class CacheEntry {
/**
* The hash associated with this cache entry
*/
private byte[] mHash;
/**
* The time associated with this cache entry
*/
private long mTime;
// TODO: debug only!
public long mSave;
// TODO: debug only!
/**
* The host associated with this cache entry
*/
private String mDomain;
/**
* Creates a new certificate-validator cache entry
* @param domain The domain to be associated with this cache entry
* @param secureHash The secure hash to be associated with this cache
* entry
*/
public CacheEntry(String domain, byte[] secureHash, long save) {
mDomain = domain;
mHash = secureHash;
// TODO: debug only!
mSave = save;
// TODO: debug only!
mTime = SystemClock.uptimeMillis();
}
/**
* @return True iff the cache item has expired
*/
public boolean expired() {
return CACHE_ENTRY_LIFETIME < SystemClock.uptimeMillis() - mTime;
}
/**
* @param domain The domain to check
* @param secureHash The secure hash to check
* @return True iff the given domain and hash match those associated
* with this entry
*/
public boolean has(String domain, byte[] secureHash) {
if (domain != null && 0 < domain.length()) {
if (!mDomain.equals(domain)) {
return false;
}
}
int hashLength = secureHash.length;
if (secureHash != null && 0 < hashLength) {
if (hashLength == mHash.length) {
for (int i = 0; i < hashLength; ++i) {
if (secureHash[i] != mHash[i]) {
return false;
}
}
return true;
}
}
return false;
}
}
};
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