+/**
+ * Authenticates a user using the email and password.
+ *
+ * @since 4.5.0
+ *
+ * @param WP_User|WP_Error|null $user WP_User or WP_Error object if a previous
+ * callback failed authentication.
+ * @param string $email Email address for authentication.
+ * @param string $password Password for authentication.
+ * @return WP_User|WP_Error WP_User on success, WP_Error on failure.
+ */
+function wp_authenticate_email_password( $user, $email, $password ) {
+ if ( $user instanceof WP_User ) {
+ return $user;
+ }
+
+ if ( empty( $email ) || empty( $password ) ) {
+ if ( is_wp_error( $user ) ) {
+ return $user;
+ }
+
+ $error = new WP_Error();
+
+ if ( empty( $email ) ) {
+ $error->add( 'empty_username', __( '<strong>ERROR</strong>: The email field is empty.' ) ); // Uses 'empty_username' for back-compat with wp_signon()
+ }
+
+ if ( empty( $password ) ) {
+ $error->add( 'empty_password', __( '<strong>ERROR</strong>: The password field is empty.' ) );
+ }
+
+ return $error;
+ }
+
+ if ( ! is_email( $email ) ) {
+ return $user;
+ }
+
+ $user = get_user_by( 'email', $email );
+
+ if ( ! $user ) {
+ return new WP_Error( 'invalid_email',
+ __( '<strong>ERROR</strong>: Invalid email address.' ) .
+ ' <a href="' . wp_lostpassword_url() . '">' .
+ __( 'Lost your password?' ) .
+ '</a>'
+ );
+ }
+
+ /** This filter is documented in wp-includes/user.php */
+ $user = apply_filters( 'wp_authenticate_user', $user, $password );
+
+ if ( is_wp_error( $user ) ) {
+ return $user;
+ }
+
+ if ( ! wp_check_password( $password, $user->user_pass, $user->ID ) ) {
+ return new WP_Error( 'incorrect_password',
+ sprintf(
+ /* translators: %s: email address */
+ __( '<strong>ERROR</strong>: The password you entered for the email address %s is incorrect.' ),
+ '<strong>' . $email . '</strong>'
+ ) .
+ ' <a href="' . wp_lostpassword_url() . '">' .
+ __( 'Lost your password?' ) .
+ '</a>'
+ );
+ }
+
+ return $user;
+}
+