Add Android support for SSL client authentication to the browser layer.

chrome/browser/ui/android/ssl_client_certificate_selector.cc

 // Copyright (c) 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.
 
+#include "base/logging.h"
 #include "chrome/browser/ssl/ssl_client_certificate_selector.h"
+#include "chrome/browser/ui/android/ssl_client_certificate_request.h"
+#include "content/public/browser/browser_thread.h"
+#include "net/base/ssl_cert_request_info.h"
 
-#include "base/logging.h"
+// On other platforms, the list of client certificates compatible with
+// the SSLCertRequestInfo is built using system APIs that do not require
+// user interaction. After this, ShowSSLClientCertificateSelector() is
+// merely used to display a tab sub-window asking the user to select
+// one of these certificates.
+
+// On Android, things are a bit different, because getting the list of
+// compatible client certificates is only possible using an API that shows
+// a system UI dialog. More precisely:
+//
+// - The application must call KeyChain.choosePrivateKeyAlias() and
+//   pass it the request parameters directly.
+//
+// - This API always launches a system activity (CertInstaller), that
+//   will display a list of compatible installed client certificates,
+//   if any, or prompt the user to install one manually otherwise.
+//
+// - Also, the first time this API is called, the CertInstaller will
+//   first prompt the user to enter the secure storage's password
+//   (which is the user's PIN code / password by default). This establishes
+//   a trust relationship between the KeyChain system application, and
+//   the application calling the API. It persists until the application
+//   is killed.
+//
+// - The client certificate selection result is sent back to the
+//   application through a UI thread callback. It only contains a
+//   string alias for the selected certificate, or 'null' to indicate
+//   that the user has canceled the selection, or couldn't unlock
+//   access to the secure storage.
+//
+// Note that:
+//
+// - There is no way, when the result if 'null', to know from the
+//   application if the user cancelled the request, or couldn't access
+//   the secure storage.
+//
+// - There is no way to cancel a request once it has started. Each call
+//   to KeyChain.choosePrivateKeyAlias() launches a new activity, which
+//   runs in a completely different process, and steals the focus from
+//   the browser.
 
 namespace chrome {
 
-// Client Auth is not implemented on Android yet.
+using browser::android::SSLClientCertificateRequest;
+
 void ShowSSLClientCertificateSelector(
     content::WebContents* contents,
     const net::HttpNetworkSession* network_session,
     net::SSLCertRequestInfo* cert_request_info,
-    const base::Callback<void(net::X509Certificate*)>& callback) {
-  NOTIMPLEMENTED();
+    const chrome::SelectCertificateCallback& callback) {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  // Create a new request, then try to start it.
+  scoped_refptr<SSLClientCertificateRequest> request(
+      new SSLClientCertificateRequest(cert_request_info, callback));
+  if (!request->Start()) {
+    LOG(ERROR) << "Could not start client certificate request!";
+    // Note: the destructor will call callback(NULL) automatically.
+  }
 }
 
 }  // namespace chrome