Merge pull request 'Validate signup email and password strength' (#155) from feature/150-signup-credential-validation into main

Reviewed-on: #155

src/Auth/RegistrationPage.php

@@ -124,6 +124,28 @@ class RegistrationPage {
 		// needed whenever the form itself is on screen.
 		if ( $canRegister && '' === $successType ) {
 			wp_enqueue_script( 'us-scheduler-register' );
+
+			// The browser gate reads the same numbers the server enforces, so the
+			// two cannot drift into disagreeing about what it accepted.
+			wp_localize_script(
+				'us-scheduler-register',
+				'usSchedulerPassword',
+				[
+					'minLength' => PasswordPolicy::MIN_LENGTH,
+					'minScore'  => PasswordPolicy::MIN_SCORE,
+					'strings'   => [
+						'short'    => sprintf(
+							/* translators: %d: minimum number of characters. */
+							__( 'At least %d characters, please.', 'unsupervised-schedular' ),
+							PasswordPolicy::MIN_LENGTH
+						),
+						'veryWeak' => __( 'Too weak — a stranger could guess this.', 'unsupervised-schedular' ),
+						'weak'     => __( 'Still too weak. Try a longer phrase.', 'unsupervised-schedular' ),
+						'medium'   => __( 'Good enough.', 'unsupervised-schedular' ),
+						'strong'   => __( 'Strong password.', 'unsupervised-schedular' ),
+					],
+				]
+			);
 		}
 
 		ob_start();
@@ -248,10 +270,6 @@ class RegistrationPage {
 		$password    = Val::string( wp_unslash( $_POST['password'] ?? '' ) );
 		$displayName = sanitize_text_field( Val::string( wp_unslash( $_POST['display_name'] ?? '' ) ) );
 
-		if ( strlen( $password ) < 8 ) {
-			return esc_html__( 'Please choose a password of at least 8 characters.', 'unsupervised-schedular' );
-		}
-
 		// The email is fixed by a personal invite; group-link signups and
 		// self-signups supply their own.
 		if ( $inviteValid && ! $invite->isGroup() ) {
@@ -263,6 +281,15 @@ class RegistrationPage {
 			}
 		}
 
+		// After the email, so the password can be checked against it. The browser
+		// scores the password with zxcvbn and refuses to submit a weak one, but
+		// that is advice a client can decline to take — this is the check that
+		// holds. See PasswordPolicy for why the two halves differ.
+		$passwordError = PasswordPolicy::validate( $password, $email, $displayName );
+		if ( null !== $passwordError ) {
+			return esc_html( $passwordError );
+		}
+
 		$policyForms = $this->signupPolicies();
 		// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.MissingUnslash, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- each element is coerced to a positive int in the array_map callback; slashes cannot survive integer coercion.
 		$accepted = array_map( static fn( mixed $v ): int => absint( Val::int( $v ) ), (array) ( $_POST['accept'] ?? [] ) );