1 files changed, 123 insertions, 1 deletions

diff --git a/remoting/host/user_authenticator_linux.cc b/remoting/host/user_authenticator_linux.cc
index d3b837c..b1a70cd 100644
--- a/remoting/host/user_authenticator_linux.cc
+++ b/remoting/host/user_authenticator_linux.cc
@@ -2,10 +2,132 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "remoting/host/user_authenticator_pam.h"
+#include "remoting/host/user_authenticator.h"
+
+#include <security/pam_appl.h>
+#include <stdlib.h>
+
+#include <string>
+
+#include "base/basictypes.h"
 
 namespace remoting {
 
+namespace {
+
+// Class to perform a single PAM user authentication.
+//
+// TODO(lambroslambrou): As pam_authenticate() can be blocking, this needs to
+// expose an asynchronous API, with pam_authenticate() called in a background
+// thread.
+class UserAuthenticatorPam : public UserAuthenticator {
+ public:
+  UserAuthenticatorPam() {}
+  virtual ~UserAuthenticatorPam() {}
+  virtual bool Authenticate(const std::string& username,
+                            const std::string& password);
+
+ private:
+  // Conversation function passed to PAM as a callback.
+  static int ConvFunction(int num_msg,
+                          const pam_message** msg,
+                          pam_response** resp,
+                          void* appdata_ptr);
+
+  // Store these for the PAM conversation function.
+  std::string username_;
+  std::string password_;
+
+  DISALLOW_COPY_AND_ASSIGN(UserAuthenticatorPam);
+};
+
+const char kPamServiceName[] = "chromoting";
+
+bool UserAuthenticatorPam::Authenticate(const std::string& username,
+                                        const std::string& password) {
+  username_ = username;
+  password_ = password;
+  pam_conv conversation;
+  conversation.conv = ConvFunction;
+  conversation.appdata_ptr = static_cast<void*>(this);
+  // TODO(lambroslambrou): Allow PAM service name to be configurable.
+  pam_handle_t* pam_handle;
+  if (pam_start(kPamServiceName, username_.c_str(),
+                &conversation, &pam_handle) != PAM_SUCCESS) {
+    return false;
+  }
+
+  // TODO(lambroslambrou): Move to separate thread.
+  int pam_status = pam_authenticate(pam_handle, 0);
+  pam_end(pam_handle, pam_status);
+  return pam_status == PAM_SUCCESS;
+}
+
+// static
+int UserAuthenticatorPam::ConvFunction(int num_msg,
+                                       const pam_message** msg,
+                                       pam_response** resp,
+                                       void* appdata_ptr) {
+  if (num_msg <= 0)
+    return PAM_CONV_ERR;
+  UserAuthenticatorPam* user_auth =
+      static_cast<UserAuthenticatorPam*>(appdata_ptr);
+  // Must allocate with malloc(), as the calling PAM module will
+  // release the memory with free().
+  pam_response* resp_tmp = static_cast<pam_response*>(
+      malloc(num_msg * sizeof(pam_response)));
+  if (resp_tmp == NULL)
+    return PAM_CONV_ERR;
+
+  bool raise_error = false;
+  // On exit from the loop, 'count' will hold the number of initialised items
+  // that the cleanup code needs to look at, in case of error.
+  int count;
+  for (count = 0; count < num_msg; count++) {
+    // Alias for readability.
+    pam_response* resp_item = &resp_tmp[count];
+    resp_item->resp_retcode = 0;
+    resp_item->resp = NULL;
+    switch (msg[count]->msg_style) {
+      case PAM_PROMPT_ECHO_ON:
+        resp_item->resp = strdup(user_auth->username_.c_str());
+        if (resp_item->resp == NULL)
+          raise_error = true;
+        break;
+      case PAM_PROMPT_ECHO_OFF:
+        resp_item->resp = strdup(user_auth->password_.c_str());
+        if (resp_item->resp == NULL)
+          raise_error = true;
+        break;
+      case PAM_TEXT_INFO:
+        // No response needed, as this instructs the PAM client to display
+        // text to the user.  Leave as NULL and continue with next prompt.
+        break;
+      default:
+        // Unexpected style code, so abort.
+        raise_error = true;
+    }
+    if (raise_error)
+      break;
+  }
+
+  if (raise_error) {
+    // Not passing the response back, so free up any memory used.
+    for (int n = 0; n < count; n++) {
+      if (resp_tmp[n].resp) {
+        free(resp_tmp[n].resp);
+      }
+    }
+    free(resp_tmp);
+    return PAM_CONV_ERR;
+  } else {
+    *resp = resp_tmp;
+    return PAM_SUCCESS;
+  }
+}
+
+}  // namespace
+
 // static
 UserAuthenticator* UserAuthenticator::Create() {
   return new UserAuthenticatorPam();