CrOS - Login Screen - Accept numeric passwords

The login screen in ChromeOS currently only performs one authentication
attempt. Either against the user's PIN or password depending on a flag
passed by the UI. When the combined 'PIN or password' input field is
used, any input consisting of only digits is treated as a PIN. If the
user's password is composed of only digits (The minimum is 8 digits.),
trying to use the password on the login screen fails.

This issue does not exist on the lock screen, where two authentication
attempts are made when the input is composed of only digits. It first
tries to authenticate against the PIN, and, in case of failure, it
tries again against the password.

Since the introduction of PIN 'automatic unlock' / 'auto submit', the
default UI has been separated into dedicated PIN and password fields
with a button to toggle between both.

This CL fixes an issue that caused the input from the dedicated password
field to be treated as a PIN instead of a password. It also improves
tests on LoginAuthUserView.

Note that the issue still exists for the combined 'PIN or password'
field and it should be addressed in the near future.

Bug: 1122939
Change-Id: I719c441d023e9b2c37b901d101e4939732061a8b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2512916Reviewed-by: Thomas Tellier <tellier@google.com>
Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Renato Silva <rrsilva@google.com>
Cr-Commit-Position: refs/heads/master@{#846085}

ash/login/ui/login_auth_user_view.cc

@@ -1530,7 +1530,7 @@ void LoginAuthUserView::OnAuthSubmit(const base::string16& password) {
 
   Shell::Get()->login_screen_controller()->AuthenticateUserWithPasswordOrPin(
       current_user().basic_user_info.account_id, base::UTF16ToUTF8(password),
-      HasAuthMethod(AUTH_PIN),
+      ShouldAuthenticateWithPin(),
       base::BindOnce(&LoginAuthUserView::OnAuthComplete,
                      weak_factory_.GetWeakPtr()));
 }
@@ -1623,6 +1623,11 @@ bool LoginAuthUserView::HasAuthMethod(AuthMethods auth_method) const {
   return (auth_methods_ & auth_method) != 0;
 }
 
+bool LoginAuthUserView::ShouldAuthenticateWithPin() const {
+  return input_field_mode_ == InputFieldMode::PIN_AND_PASSWORD ||
+         input_field_mode_ == InputFieldMode::PIN_WITH_TOGGLE;
+}
+
 void LoginAuthUserView::AttemptAuthenticateWithChallengeResponse() {
   challenge_response_view_->SetState(
       ChallengeResponseView::State::kAuthenticating);

ash/login/ui/login_auth_user_view.h

@@ -216,6 +216,9 @@ class ASH_EXPORT LoginAuthUserView : public NonAccessibleView {
   // bool has_tap = HasAuthMethod(AUTH_TAP).
   bool HasAuthMethod(AuthMethods auth_method) const;
 
+  // Whether the authentication attempt should use the user's PIN.
+  bool ShouldAuthenticateWithPin() const;
+
   // TODO(crbug/899812): remove this and pass a handler in via the Callbacks
   // struct instead.
   void AttemptAuthenticateWithExternalBinary();