Prevent merging .eml file attachments

src/HasParsedMessage.php

@@ -13,6 +13,7 @@
 use ZBateson\MailMimeParser\Header\Part\ContainerPart;
 use ZBateson\MailMimeParser\Header\Part\NameValuePart;
 use ZBateson\MailMimeParser\Message as MailMimeMessage;
+use ZBateson\MailMimeParser\Message\IMessagePart;
 
 trait HasParsedMessage
 {
@@ -121,10 +122,7 @@ public function attachments(): array
         $attachments = [];
 
         foreach ($this->parse()->getAllAttachmentParts() as $part) {
-            // If the attachment's content type is message/rfc822, we're
-            // working with a forwarded message. We will parse the
-            // forwarded message and merge in its attachments.
-            if (strtolower($part->getContentType()) === 'message/rfc822') {
+            if ($this->isForwardedMessage($part)) {
                 $message = new FileMessage($part->getContent());
 
                 $attachments = array_merge($attachments, $message->attachments());
@@ -157,6 +155,16 @@ public function attachmentCount(): int
         return $this->parse()->getAttachmentCount();
     }
 
+    /**
+     * Determine if the attachment should be treated as an embedded forwarded message.
+     */
+    protected function isForwardedMessage(IMessagePart $part): bool
+    {
+        return empty($part->getFilename())
+            && strtolower((string) $part->getContentType()) === 'message/rfc822'
+            && strtolower((string) $part->getContentDisposition()) !== 'attachment';
+    }
+
     /**
      * Get addresses from the given header.
      *

tests/Unit/FileMessageTest.php

@@ -217,7 +217,7 @@
     expect($attachments[0]->filename())->toBe('inline_image.png');
 });
 
-test('it can extract attachments from forwarded messages', function () {
+test('it merges attachments from an inline forwarded message', function () {
     // Create a forwarded message that contains an attachment
     $forwardedMessage = <<<'EOT'
     From: "Original Sender" <[email protected]>
@@ -243,7 +243,7 @@
     --ORIGINAL_BOUNDARY--
     EOT;
 
-    // Create the main message that forwards the above message
+    // Create the main message that forwards the above message inline (no filename/disposition on message/rfc822)
     $contents = <<<EOT
     From: "Forwarder" <[email protected]>
     To: "Final Recipient" <[email protected]>
@@ -259,8 +259,7 @@
     Here is the forwarded message with its attachment.
 
     --FORWARD_BOUNDARY
-    Content-Type: message/rfc822; name="forwarded-message.eml"
-    Content-Disposition: attachment; filename="forwarded-message.eml"
+    Content-Type: message/rfc822
 
     $forwardedMessage
     --FORWARD_BOUNDARY
@@ -290,6 +289,79 @@
     expect($attachments[1]->contentType())->toBe('application/zip');
 });
 
+test('it does not merge attached .eml files', function () {
+    // Forwarded message that itself contains an attachment
+    $forwardedMessage = <<<'EOT'
+    From: "Original Sender" <[email protected]>
+    To: "Original Recipient" <[email protected]>
+    Subject: Original Message with Attachment
+    Date: Tue, 18 Feb 2025 10:00:00 -0500
+    Message-ID: <[email protected]>
+    MIME-Version: 1.0
+    Content-Type: multipart/mixed; boundary="ORIGINAL_BOUNDARY"
+
+    --ORIGINAL_BOUNDARY
+    Content-Type: text/plain; charset="UTF-8"
+
+    This is the original message with an attachment.
+
+    --ORIGINAL_BOUNDARY
+    Content-Type: application/pdf; name="original-document.pdf"
+    Content-Disposition: attachment; filename="original-document.pdf"
+    Content-Transfer-Encoding: base64
+
+    JVBERi0xLjUKJeLjz9MKMyAwIG9iago8PC9MZW5ndGggNCAgIC9GaWx0ZXIvQXNjaWlIYXgg
+    ICAgPj5zdHJlYW0Kc3R1ZmYKZW5kc3RyZWFtCmVuZG9iajAK
+    --ORIGINAL_BOUNDARY--
+    EOT;
+
+    // Top-level message that attaches the forwarded message as an .eml (should not merge)
+    $contents = <<<EOT
+    From: "Forwarder" <[email protected]>
+    To: "Final Recipient" <[email protected]>
+    Subject: Fwd: Original Message with Attachment (as .eml)
+    Date: Wed, 19 Feb 2025 12:34:56 -0500
+    Message-ID: <[email protected]>
+    MIME-Version: 1.0
+    Content-Type: multipart/mixed; boundary="FORWARD_BOUNDARY"
+
+    --FORWARD_BOUNDARY
+    Content-Type: text/plain; charset="UTF-8"
+
+    Here is the forwarded message attached as an .eml file.
+
+    --FORWARD_BOUNDARY
+    Content-Type: message/rfc822; name="forwarded-message.eml"
+    Content-Disposition: attachment; filename="forwarded-message.eml"
+
+    $forwardedMessage
+    --FORWARD_BOUNDARY
+    Content-Type: application/zip; name="additional-file.zip"
+    Content-Disposition: attachment; filename="additional-file.zip"
+    Content-Transfer-Encoding: base64
+
+    UEsDBAoAAAAAAKxVVVMAAAAAAAAAAAAAAAAJAAAAdGVzdC50eHRQSwECFAAKAAAAAACs
+    VVVTAAAAAAAAAAAAAAAACQAAAAAAAAAAAAAAAAAAAHRlc3QudHh0UEsFBgAAAAABAAEA
+    NwAAAB8AAAAAAA==
+    --FORWARD_BOUNDARY--
+    EOT;
+
+    $message = new FileMessage($contents);
+
+    $attachments = $message->attachments();
+
+    // Expect exactly two top-level attachments: the attached .eml itself and the zip
+    expect($attachments)->toHaveCount(2);
+
+    // .eml is preserved as-is (no merging of its inner PDF)
+    expect($attachments[0]->contentType())->toBe('message/rfc822');
+    expect($attachments[0]->filename())->toBe('forwarded-message.eml');
+
+    // The top-level zip attachment remains
+    expect($attachments[1]->contentType())->toBe('application/zip');
+    expect($attachments[1]->filename())->toBe('additional-file.zip');
+});
+
 test('it can handle multiple levels of forwarded messages with attachments', function () {
     // Create the deepest nested message with an attachment
     $deepestMessage = <<<'EOT'