Merge ~azzar1/unity:fix-1733557 into unity:master

[Andrea Azzarone]

locksreen: cancel authentication if externally unlocked

The lockscreen can be externellay unlocked. This happens e.g. when
you unlock the session from LightDM or from the CLI. We need to
cancel the authentication in order to ensure that the next one does
not fail.

Fixes: https://bugs.launchpad.net/unity/+bug/1733557

[Rael Gugelmin Cunha (rael-gc)]

Just a reminder that this issue affects 16.04 and 18.04 too.

[Marco Trevisan (Treviño) (3v1n0)]

Looks fine

review: Approve

diff --git a/lockscreen/LockScreenController.cpp b/lockscreen/LockScreenController.cpp
index 8f6e7bc..907a130 100644
--- a/lockscreen/LockScreenController.cpp
+++ b/lockscreen/LockScreenController.cpp
@@ -536,6 +536,8 @@ void Controller::OnUnlockRequested()
 
   HideBlankWindow();
   HideShields();
+
+  user_authenticator_->AuthenticateCancel();
 }
 
 void Controller::HideShields()
diff --git a/lockscreen/UserAuthenticator.h b/lockscreen/UserAuthenticator.h
index e30ce2f..60e8684 100644
--- a/lockscreen/UserAuthenticator.h
+++ b/lockscreen/UserAuthenticator.h
@@ -43,6 +43,7 @@ public:
 
   // Authenticate the user in a background thread.
   virtual bool AuthenticateStart(std::string const& username, AuthenticateEndCallback const&) = 0;
+  virtual void AuthenticateCancel() = 0;
 
   sigc::signal<void> start_failed;
   sigc::signal<void, std::string, PromiseAuthCodePtr const&> echo_on_requested;
diff --git a/lockscreen/UserAuthenticatorPam.cpp b/lockscreen/UserAuthenticatorPam.cpp
index 463d8f9..d1d6c27 100644
--- a/lockscreen/UserAuthenticatorPam.cpp
+++ b/lockscreen/UserAuthenticatorPam.cpp
@@ -50,6 +50,7 @@ bool UserAuthenticatorPam::AuthenticateStart(std::string const& username,
   }
 
   first_prompt_ = true;
+  cancelled_ = false;
   username_ = username;
   authenticate_cb_ = authenticate_cb;
 
@@ -64,6 +65,18 @@ bool UserAuthenticatorPam::AuthenticateStart(std::string const& username,
   return !error;
 }
 
+void UserAuthenticatorPam::AuthenticateCancel()
+{
+  if (!pam_handle_)
+  {
+    LOG_DEBUG(logger) << "Unable to cancel authentication because none has been started";
+    return;
+  }
+
+  LOG_DEBUG(logger) << "Cancelling the authentication";
+  cancelled_ = true;
+}
+
 gpointer UserAuthenticatorPam::AuthenticationThreadFunc(gpointer data)
 {
   auto self = static_cast<UserAuthenticatorPam*>(data);
@@ -92,7 +105,10 @@ gpointer UserAuthenticatorPam::AuthenticationThreadFunc(gpointer data)
 
   pam_end(self->pam_handle_, self->status_);
   self->pam_handle_ = nullptr;
-  self->source_manager_.AddTimeout(0, [self] {   self->authenticate_cb_(self->status_ == PAM_SUCCESS); return false; });
+
+  if (!self->cancelled_)
+    self->source_manager_.AddTimeout(0, [self] {   self->authenticate_cb_(self->status_ == PAM_SUCCESS); return false; });
+
   return nullptr;
 }
 
@@ -188,9 +204,17 @@ int UserAuthenticatorPam::ConversationFunction(int num_msg,
     auto future = promise->get_future();
     pam_response* resp_item = &tmp_response[i++];
     resp_item->resp_retcode = 0;
-    resp_item->resp = strdup(future.get().c_str());
+    resp_item->resp = nullptr;
+
+    std::future_status status;
+    do
+    {
+        status = future.wait_for(std::chrono::seconds(1));
+        if (status == std::future_status::ready)
+          resp_item->resp = strdup(future.get().c_str());
+    } while (status != std::future_status::ready && !user_auth->cancelled_);
 
-    if (!resp_item->resp)
+    if (!resp_item->resp || user_auth->cancelled_)
     {
       raise_error = true;
       break;
diff --git a/lockscreen/UserAuthenticatorPam.h b/lockscreen/UserAuthenticatorPam.h
index 82273cd..4043cd4 100644
--- a/lockscreen/UserAuthenticatorPam.h
+++ b/lockscreen/UserAuthenticatorPam.h
@@ -39,6 +39,7 @@ class UserAuthenticatorPam : public UserAuthenticator
 public:
   UserAuthenticatorPam() = default;
   bool AuthenticateStart(std::string const& username, AuthenticateEndCallback const&) override;
+  void AuthenticateCancel() override;
 
 private:
   UserAuthenticatorPam(UserAuthenticatorPam const&) = delete;
@@ -57,6 +58,7 @@ private:
 
   int status_ = 0;
   bool first_prompt_ = true;
+  bool cancelled_ = false;
   pam_handle* pam_handle_ = nullptr;
   glib::SourceManager source_manager_;
 };