Make client certificate requests optional.

This prevents things from always failing if the server requires a client
SSL certificate.

Note that the solution used to determine if a certificate request was
made for a given request is approximate; it is timestamp based and can
theoretically give a false positive. In practice, this is very unlikely,
since another cert request had to have happened around the same time,
AND the response must be a 401/403.

Change-Id: Ieb77cf91db3bd52ba4adf1fb07357fef7e204ba5

emailcommon/src/com/android/emailcommon/utility/EmailClientConnectionManager.java

@@ -17,6 +17,10 @@
 
 package com.android.emailcommon.utility;
 
+import android.content.Context;
+import android.net.SSLCertificateSocketFactory;
+import android.util.Log;
+
 import com.android.emailcommon.Logging;
 import com.android.emailcommon.utility.SSLUtils.KeyChainKeyManager;
 import com.android.emailcommon.utility.SSLUtils.TrackingKeyManager;
@@ -27,10 +31,6 @@ import org.apache.http.conn.scheme.SchemeRegistry;
 import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
 import org.apache.http.params.HttpParams;
 
-import android.content.Context;
-import android.net.SSLCertificateSocketFactory;
-import android.util.Log;
-
 import java.security.cert.CertificateException;
 
 import javax.net.ssl.KeyManager;
@@ -43,11 +43,18 @@ public class EmailClientConnectionManager extends ThreadSafeClientConnManager {
 
     private static final boolean LOG_ENABLED = false;
 
+    /**
+     * A {@link KeyManager} to track client certificate requests from servers.
+     */
+    private final TrackingKeyManager mTrackingKeyManager;
+
     /**
      * Not publicly instantiable except via {@link #newInstance(HttpParams)}
      */
-    private EmailClientConnectionManager(HttpParams params, SchemeRegistry registry) {
+    private EmailClientConnectionManager(
+            HttpParams params, SchemeRegistry registry, TrackingKeyManager keyManager) {
         super(params, registry);
+        mTrackingKeyManager = keyManager;
     }
 
     public static EmailClientConnectionManager newInstance(HttpParams params) {
@@ -64,7 +71,7 @@ public class EmailClientConnectionManager extends ThreadSafeClientConnManager {
         registry.register(new Scheme("httpts",
                 SSLUtils.getHttpSocketFactory(true /*insecure*/, keyManager), 443));
 
-        return new EmailClientConnectionManager(params, registry);
+        return new EmailClientConnectionManager(params, registry, keyManager);
     }
 
     /**
@@ -129,4 +136,13 @@ public class EmailClientConnectionManager extends ThreadSafeClientConnManager {
         String safeAlias = SSLUtils.escapeForSchemeName(clientCertAlias);
         return (trustAllServerCerts ? "httpts" : "https") + "+clientCert+" + safeAlias;
     }
+
+    /**
+     * @param since A timestamp in millis from epoch from which to check
+     * @return whether or not this connection manager has detected any unsatisfied requests for
+     *     a client SSL certificate by any servers
+     */
+    public synchronized boolean hasDetectedUnsatisfiedCertReq(long since) {
+        return mTrackingKeyManager.getLastCertReqTime() >= since;
+    }
 }

emailcommon/src/com/android/emailcommon/utility/SSLUtils.java

@@ -16,14 +16,15 @@
 
 package com.android.emailcommon.utility;
 
-import com.google.common.annotations.VisibleForTesting;
-
 import android.content.Context;
 import android.net.SSLCertificateSocketFactory;
 import android.security.KeyChain;
 import android.security.KeyChainException;
 import android.util.Log;
 
+import com.google.common.annotations.VisibleForTesting;
+
+import java.net.InetAddress;
 import java.net.Socket;
 import java.security.Principal;
 import java.security.PrivateKey;
@@ -137,35 +138,46 @@ public class SSLUtils {
     }
 
     /**
-     * A dummy {@link KeyManager} which throws a {@link CertificateRequestedException} if the
-     * server requests a certificate.
+     * A dummy {@link KeyManager} which keeps track of the last time a server has requested
+     * a client certificate.
      */
     public static class TrackingKeyManager extends StubKeyManager {
+        private volatile long mLastTimeCertRequested = 0L;
+
         @Override
         public String chooseClientAlias(String[] keyTypes, Principal[] issuers, Socket socket) {
             if (LOG_ENABLED) {
+                InetAddress address = socket.getInetAddress();
                 Log.i(TAG, "TrackingKeyManager: requesting a client cert alias for "
-                        + Arrays.toString(keyTypes));
+                        + address.getCanonicalHostName());
             }
-            throw new CertificateRequestedException();
+            mLastTimeCertRequested = System.currentTimeMillis();
+            return null;
         }
 
         @Override
         public X509Certificate[] getCertificateChain(String alias) {
+            if (LOG_ENABLED) {
+                Log.i(TAG, "TrackingKeyManager: returning a null cert chain");
+            }
             return null;
         }
 
         @Override
         public PrivateKey getPrivateKey(String alias) {
+            if (LOG_ENABLED) {
+                Log.i(TAG, "TrackingKeyManager: returning a null private key");
+            }
             return null;
         }
-    }
 
-    /**
-     * An exception indicating that a server requested a client certificate but none was
-     * available to be presented.
-     */
-    public static class CertificateRequestedException extends RuntimeException {
+        /**
+         * @return the last time that this {@link KeyManager} detected a request by a server
+         *     for a client certificate (in millis since epoch).
+         */
+        public long getLastCertReqTime() {
+            return mLastTimeCertRequested;
+        }
     }
 
     /**