DKIM tweaks, see #1962, #1964, #1965

src/PHPMailer.php

@@ -769,11 +769,22 @@ class PHPMailer
     const STOP_CRITICAL = 2;
 
     /**
-     * SMTP RFC standard line ending.
+     * The SMTP standard CRLF line break.
+     * If you want to change line break format, change static::$LE, not this.
+     */
+    const CRLF = "\r\n";
+
+    /**
+     * "Folding White Space" a white space string used for line folding.
+     */
+    const FWS = ' ';
+
+    /**
+     * SMTP RFC standard line ending; Carriage Return, Line Feed.
      *
      * @var string
      */
-    protected static $LE = "\r\n";
+    protected static $LE = self::CRLF;
 
     /**
      * The maximum line length supported by mail().
@@ -1446,7 +1457,7 @@ public function preSend()
         ) {
             //SMTP mandates RFC-compliant line endings
             //and it's also used with mail() on Windows
-            static::setLE("\r\n");
+            static::setLE(self::CRLF);
         } else {
             //Maintain backward compatibility with legacy Linux command line mailers
             static::setLE(PHP_EOL);
@@ -1553,7 +1564,7 @@ public function preSend()
                     $this->encodeHeader($this->secureHeader($this->Subject)),
                     $this->MIMEBody
                 );
-                $this->MIMEHeader = rtrim($this->MIMEHeader, "\r\n ") . static::$LE .
+                $this->MIMEHeader = static::stripTrailingWSP($this->MIMEHeader) . static::$LE .
                     static::normalizeBreaks($header_dkim) . static::$LE;
             }
 
@@ -1620,7 +1631,7 @@ public function postSend()
      */
     protected function sendmailSend($header, $body)
     {
-        $header = rtrim($header, "\r\n ") . static::$LE . static::$LE;
+        $header = static::stripTrailingWSP($header) . static::$LE . static::$LE;
 
         // CVE-2016-10033, CVE-2016-10045: Don't pass -f if characters will be escaped.
         if (!empty($this->Sender) && self::isShellSafe($this->Sender)) {
@@ -1750,7 +1761,7 @@ protected static function isPermittedPath($path)
      */
     protected function mailSend($header, $body)
     {
-        $header = rtrim($header, "\r\n ") . static::$LE . static::$LE;
+        $header = static::stripTrailingWSP($header) . static::$LE . static::$LE;
 
         $toArr = [];
         foreach ($this->to as $toaddr) {
@@ -1839,7 +1850,7 @@ public function setSMTPInstance(SMTP $smtp)
      */
     protected function smtpSend($header, $body)
     {
-        $header = rtrim($header, "\r\n ") . static::$LE . static::$LE;
+        $header = static::stripTrailingWSP($header) . static::$LE . static::$LE;
         $bad_rcpt = [];
         if (!$this->smtpConnect($this->SMTPOptions)) {
             throw new Exception($this->lang('smtp_connect_failed'), self::STOP_CRITICAL);
@@ -2511,7 +2522,8 @@ public function getMailMIME()
      */
     public function getSentMIMEMessage()
     {
-        return rtrim($this->MIMEHeader . $this->mailHeader, "\n\r") . static::$LE . static::$LE . $this->MIMEBody;
+        return static::stripTrailingWSP($this->MIMEHeader . $this->mailHeader) .
+            static::$LE . static::$LE . $this->MIMEBody;
     }
 
     /**
@@ -4355,7 +4367,7 @@ public static function normalizeBreaks($text, $breaktype = null)
             $breaktype = static::$LE;
         }
         // Normalise to \n
-        $text = str_replace(["\r\n", "\r"], "\n", $text);
+        $text = str_replace([self::CRLF, "\r"], "\n", $text);
         // Now convert LE as needed
         if ("\n" !== $breaktype) {
             $text = str_replace("\n", $breaktype, $text);
@@ -4364,6 +4376,18 @@ public static function normalizeBreaks($text, $breaktype = null)
         return $text;
     }
 
+    /**
+     * Remove trailing breaks from a string
+     *
+     * @param string $text
+     *
+     * @return string The text to remove breaks from.
+     */
+    public static function stripTrailingWSP($text)
+    {
+        return rtrim($text, " \r\n\t");
+    }
+
     /**
      * Return the current line break format string.
      *
@@ -4478,7 +4502,7 @@ public function DKIM_HeaderC($signHeader)
         //Unfold header lines
         $signHeader = preg_replace('/\r\n[ \t]+/', ' ', $signHeader);
         //Break headers out into an array
-        $lines = explode("\r\n", $signHeader);
+        $lines = explode(self::CRLF, static::normalizeBreaks($signHeader, self::CRLF));
         foreach ($lines as $key => $line) {
             //If the header is missing a :, skip it as it's invalid
             //This is likely to happen because the explode() above will also split
@@ -4498,7 +4522,7 @@ public function DKIM_HeaderC($signHeader)
             $lines[$key] = trim($heading, " \t") . ':' . trim($value, " \t");
         }
 
-        return implode("\r\n", $lines);
+        return implode(self::CRLF, $lines);
     }
 
     /**
@@ -4515,13 +4539,13 @@ public function DKIM_HeaderC($signHeader)
     public function DKIM_BodyC($body)
     {
         if (empty($body)) {
-            return "\r\n";
+            return self::CRLF;
         }
         // Normalize line endings to CRLF
-        $body = static::normalizeBreaks($body, "\r\n");
+        $body = static::normalizeBreaks($body, self::CRLF);
 
         //Reduce multiple trailing line breaks to a single one
-        return rtrim($body, "\r\n") . "\r\n";
+        return static::stripTrailingWSP($body) . self::CRLF;
     }
 
     /**
@@ -4542,6 +4566,7 @@ public function DKIM_Add($headers_line, $subject, $body)
         $DKIMquery = 'dns/txt'; // Query method
         $DKIMtime = time();
         //Always sign these headers without being asked
+        //Recommended list from https://tools.ietf.org/html/rfc6376#section-5.4.1
         $autoSignHeaders = [
             'From',
             'To',
@@ -4625,9 +4650,9 @@ public function DKIM_Add($headers_line, $subject, $body)
                 //Fold long values
                 if (strlen($copiedHeader) > self::STD_LINE_LENGTH - 3) {
                     $copiedHeaderFields .= substr(
-                        chunk_split($copiedHeader, self::STD_LINE_LENGTH - 3, static::$LE . ' '),
+                        chunk_split($copiedHeader, self::STD_LINE_LENGTH - 3, static::$LE . self::FWS),
                         0,
-                        -strlen(static::$LE . ' ')
+                        -strlen(static::$LE . self::FWS)
                     );
                 } else {
                     $copiedHeaderFields .= $copiedHeader;
@@ -4666,7 +4691,7 @@ public function DKIM_Add($headers_line, $subject, $body)
             $headerValues . static::$LE . $dkimSignatureHeader
         );
         $signature = $this->DKIM_Sign($canonicalizedHeaders);
-        $signature = trim(chunk_split($signature, self::STD_LINE_LENGTH - 3, static::$LE . ' '));
+        $signature = trim(chunk_split($signature, self::STD_LINE_LENGTH - 3, static::$LE . self::FWS));
 
         return static::normalizeBreaks($dkimSignatureHeader . $signature) . static::$LE;
     }