From 455add44508a5e8ae7b7e9fdffe756d47441db62 Mon Sep 17 00:00:00 2001
From: Bart Butler <bartbutler@protonmail.com>
Date: Thu, 21 May 2020 15:00:57 -0700
Subject: [PATCH] Add Content-Location attachment header support

---
 src/PHPMailer.php | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/PHPMailer.php b/src/PHPMailer.php
index ba4bcd472..763599be0 100644
--- a/src/PHPMailer.php
+++ b/src/PHPMailer.php
@@ -60,6 +60,9 @@ class PHPMailer
     const ICAL_METHOD_COUNTER = 'COUNTER';
     const ICAL_METHOD_DECLINECOUNTER = 'DECLINECOUNTER';
 
+    const CONTENT_ID = 'Content-ID';
+    const CONTENT_LOCATION = 'Content-Location';
+
     /**
      * Email priority.
      * Options: null (default), 1 = High, 3 = Normal, 5 = low.
@@ -3292,6 +3295,7 @@ public function addAttachment(
                 5 => false, //isStringAttachment
                 6 => $disposition,
                 7 => $name,
+                8 => static::CONTENT_ID,
             ];
         } catch (Exception $exc) {
             $this->setError($exc->getMessage());
@@ -3358,6 +3362,7 @@ protected function attachAll($disposition_type, $boundary)
                 $type = $attachment[4];
                 $disposition = $attachment[6];
                 $cid = $attachment[7];
+                $cidType = $attachment[8];
                 if ('inline' === $disposition && array_key_exists($cid, $cidUniq)) {
                     continue;
                 }
@@ -3384,9 +3389,17 @@ protected function attachAll($disposition_type, $boundary)
                     $mime[] = sprintf('Content-Transfer-Encoding: %s%s', $encoding, static::$LE);
                 }
 
-                //Only set Content-IDs on inline attachments
-                if ((string) $cid !== '' && $disposition === 'inline') {
-                    $mime[] = 'Content-ID: <' . $this->encodeHeader($this->secureHeader($cid)) . '>' . static::$LE;
+                //Only set Content-ID/Content-Location headers on inline attachments
+                if (
+                    (string) $cid !== ''
+                    && $disposition === 'inline'
+                    && in_array($cidType, [static::CONTENT_ID, static::CONTENT_LOCATION], true)
+                ) {
+                    $encodedCid = $this->encodeHeader($this->secureHeader($cid));
+                    if ($cidType === static::CONTENT_ID) {
+                        $encodedCid = '<' . $encodedCid . '>';
+                    }
+                    $mime[] = $cidType . ': ' . $encodedCid . static::$LE;
                 }
 
                 //Allow for bypassing the Content-Disposition header
@@ -3782,6 +3795,7 @@ public function addStringAttachment(
                 5 => true, //isStringAttachment
                 6 => $disposition,
                 7 => 0,
+                8 => '',
             ];
         } catch (Exception $exc) {
             $this->setError($exc->getMessage());
@@ -3813,6 +3827,7 @@ public function addStringAttachment(
      * @param string $type        File MIME type (by default mapped from the `$path` filename's extension)
      * @param string $disposition Disposition to use: `inline` (default) or `attachment`
      *                            (unlikely you want this – {@see `addAttachment()`} instead)
+     * @param string $cidType     static::CONTENT_ID (default) or static::CONTENT_LOCATION
      *
      * @return bool True on successfully adding an attachment
      * @throws Exception
@@ -3824,7 +3839,8 @@ public function addEmbeddedImage(
         $name = '',
         $encoding = self::ENCODING_BASE64,
         $type = '',
-        $disposition = 'inline'
+        $disposition = 'inline',
+        $cidType = self::CONTENT_ID
     ) {
         try {
             if (!static::fileIsAccessible($path)) {
@@ -3855,6 +3871,7 @@ public function addEmbeddedImage(
                 5 => false, //isStringAttachment
                 6 => $disposition,
                 7 => $cid,
+                8 => $cidType,
             ];
         } catch (Exception $exc) {
             $this->setError($exc->getMessage());
@@ -3883,6 +3900,7 @@ public function addEmbeddedImage(
      * @param string $encoding    File encoding (see $Encoding), defaults to 'base64'
      * @param string $type        MIME type - will be used in preference to any automatically derived type
      * @param string $disposition Disposition to use
+     * @param string $cidType     static::CONTENT_ID (default) or static::CONTENT_LOCATION
      *
      * @throws Exception
      *
@@ -3894,7 +3912,8 @@ public function addStringEmbeddedImage(
         $name = '',
         $encoding = self::ENCODING_BASE64,
         $type = '',
-        $disposition = 'inline'
+        $disposition = 'inline',
+        $cidType = self::CONTENT_ID
     ) {
         try {
             //If a MIME type is not specified, try to work it out from the name
@@ -3916,6 +3935,7 @@ public function addStringEmbeddedImage(
                 5 => true, //isStringAttachment
                 6 => $disposition,
                 7 => $cid,
+                8 => $cidType,
             ];
         } catch (Exception $exc) {
             $this->setError($exc->getMessage());