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   1  <?php
   2  /**
   3   * Handle Trackbacks and Pingbacks Sent to WordPress
   4   *
   5   * @since 0.71
   6   *
   7   * @package WordPress
   8   * @subpackage Trackbacks
   9   */
  10  
  11  if ( empty( $wp ) ) {
  12      require_once  __DIR__ . '/wp-load.php';
  13      wp( array( 'tb' => '1' ) );
  14  }
  15  
  16  // Always run as an unauthenticated user.
  17  wp_set_current_user( 0 );
  18  
  19  /**
  20   * Response to a trackback.
  21   *
  22   * Responds with an error or success XML message.
  23   *
  24   * @since 0.71
  25   *
  26   * @param int|bool $error         Whether there was an error.
  27   *                                Default 0. Accepts 0 or 1, true or false.
  28   * @param string   $error_message Error message if an error occurred. Default empty string.
  29   * @return void Never returns if `$error` is truthy, as the function dies after
  30   *              sending the error response.
  31   * @phpstan-return ( $error is 0|false ? void : never )
  32   */
  33  function trackback_response( $error = 0, $error_message = '' ) {
  34      header( 'Content-Type: text/xml; charset=' . get_option( 'blog_charset' ) );
  35  
  36      if ( $error ) {
  37          echo '<?xml version="1.0" encoding="utf-8"?' . ">\n";
  38          echo "<response>\n";
  39          echo "<error>1</error>\n";
  40          echo '<message>' . esc_xml( $error_message ) . "</message>\n";
  41          echo '</response>';
  42          die();
  43      } else {
  44          echo '<?xml version="1.0" encoding="utf-8"?' . ">\n";
  45          echo "<response>\n";
  46          echo "<error>0</error>\n";
  47          echo '</response>';
  48      }
  49  }
  50  
  51  if ( ! isset( $_GET['tb_id'] ) || ! $_GET['tb_id'] ) {
  52      $post_id = explode( '/', $_SERVER['REQUEST_URI'] );
  53      $post_id = (int) $post_id[ count( $post_id ) - 1 ];
  54  }
  55  
  56  $trackback_url = isset( $_POST['url'] ) ? sanitize_url( $_POST['url'] ) : '';
  57  $charset       = isset( $_POST['charset'] ) ? sanitize_text_field( $_POST['charset'] ) : '';
  58  
  59  // These three are stripslashed here so they can be properly escaped after mb_convert_encoding().
  60  $title     = isset( $_POST['title'] ) ? sanitize_text_field( wp_unslash( $_POST['title'] ) ) : '';
  61  $excerpt   = isset( $_POST['excerpt'] ) ? sanitize_textarea_field( wp_unslash( $_POST['excerpt'] ) ) : '';
  62  $blog_name = isset( $_POST['blog_name'] ) ? sanitize_text_field( wp_unslash( $_POST['blog_name'] ) ) : '';
  63  
  64  if ( $charset ) {
  65      $charset = str_replace( array( ',', ' ' ), '', strtoupper( trim( $charset ) ) );
  66  
  67      // Validate the specified "sender" charset is available on the receiving site.
  68      if ( function_exists( 'mb_list_encodings' ) && ! in_array( $charset, mb_list_encodings(), true ) ) {
  69          $charset = '';
  70      }
  71  }
  72  
  73  if ( ! $charset ) {
  74      $charset = 'ASCII, UTF-8, ISO-8859-1, JIS, EUC-JP, SJIS';
  75  }
  76  
  77  // No valid uses for UTF-7.
  78  if ( str_contains( $charset, 'UTF-7' ) ) {
  79      die;
  80  }
  81  
  82  // For international trackbacks.
  83  if ( function_exists( 'mb_convert_encoding' ) ) {
  84      $title     = mb_convert_encoding( $title, get_option( 'blog_charset' ), $charset );
  85      $excerpt   = mb_convert_encoding( $excerpt, get_option( 'blog_charset' ), $charset );
  86      $blog_name = mb_convert_encoding( $blog_name, get_option( 'blog_charset' ), $charset );
  87  }
  88  
  89  // Escape values to use in the trackback.
  90  $title     = wp_slash( $title );
  91  $excerpt   = wp_slash( $excerpt );
  92  $blog_name = wp_slash( $blog_name );
  93  
  94  if ( is_single() || is_page() ) {
  95      $post_id = $posts[0]->ID;
  96  }
  97  
  98  if ( ! isset( $post_id ) || ! (int) $post_id ) {
  99      trackback_response( 1, __( 'I really need an ID for this to work.' ) );
 100  }
 101  
 102  if ( empty( $title ) && empty( $trackback_url ) && empty( $blog_name ) ) {
 103      // If it doesn't look like a trackback at all.
 104      wp_redirect( get_permalink( $post_id ) );
 105      exit;
 106  }
 107  
 108  if ( ! empty( $trackback_url ) && ! empty( $title ) ) {
 109      /**
 110       * Fires before the trackback is added to a post.
 111       *
 112       * @since 4.7.0
 113       *
 114       * @param int    $post_id       Post ID related to the trackback.
 115       * @param string $trackback_url Trackback URL.
 116       * @param string $charset       Character set.
 117       * @param string $title         Trackback title.
 118       * @param string $excerpt       Trackback excerpt.
 119       * @param string $blog_name     Site name.
 120       */
 121      do_action( 'pre_trackback_post', $post_id, $trackback_url, $charset, $title, $excerpt, $blog_name );
 122  
 123      header( 'Content-Type: text/xml; charset=' . get_option( 'blog_charset' ) );
 124  
 125      if ( ! pings_open( $post_id ) ) {
 126          trackback_response( 1, __( 'Sorry, trackbacks are closed for this item.' ) );
 127      }
 128  
 129      $title   = wp_html_excerpt( $title, 250, '&#8230;' );
 130      $excerpt = wp_html_excerpt( $excerpt, 252, '&#8230;' );
 131  
 132      $comment_post_id      = (int) $post_id;
 133      $comment_author       = $blog_name;
 134      $comment_author_email = '';
 135      $comment_author_url   = $trackback_url;
 136      $comment_content      = "<strong>$title</strong>\n\n$excerpt";
 137      $comment_type         = 'trackback';
 138  
 139      $dupe = $wpdb->get_results(
 140          $wpdb->prepare(
 141              "SELECT * FROM $wpdb->comments WHERE comment_post_ID = %d AND comment_author_url = %s",
 142              $comment_post_id,
 143              $comment_author_url
 144          )
 145      );
 146  
 147      if ( $dupe ) {
 148          trackback_response( 1, __( 'There is already a ping from that URL for this post.' ) );
 149      }
 150  
 151      $commentdata = array(
 152          'comment_post_ID' => $comment_post_id,
 153      );
 154  
 155      $commentdata += compact(
 156          'comment_author',
 157          'comment_author_email',
 158          'comment_author_url',
 159          'comment_content',
 160          'comment_type'
 161      );
 162  
 163      $result = wp_new_comment( $commentdata );
 164  
 165      if ( is_wp_error( $result ) ) {
 166          trackback_response( 1, $result->get_error_message() );
 167      }
 168  
 169      $trackback_id = $wpdb->insert_id;
 170  
 171      /**
 172       * Fires after a trackback is added to a post.
 173       *
 174       * @since 1.2.0
 175       *
 176       * @param int $trackback_id Trackback ID.
 177       */
 178      do_action( 'trackback_post', $trackback_id );
 179  
 180      trackback_response( 0 );
 181  }