Fix decoding mail parts with multiple base64-encoded text blocks (#9290)

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Fix newmail_notifier notification focus in Chrome (#9467)
 - Fix fatal error when parsing some TNEF attachments (#9462)
 - Fix double scrollbar when composing a mail with many plain text lines (#7760)
+- Fix decoding mail parts with multiple base64-encoded text blocks (#9290)
 
 ## Release 1.6.7
 

program/lib/Roundcube/rcube_imap_generic.php

@@ -3049,7 +3049,14 @@ protected static function decodeContent($chunk, $mode, $is_last = false, &$prev
                 $prev = '';
             }
 
-            return base64_decode($chunk);
+            // There might be multiple base64 blocks in a single message part,
+            // we have to pass them separately to base64_decode() (#9290)
+            $result = '';
+            foreach (preg_split('|=+|', $chunk, -1, \PREG_SPLIT_NO_EMPTY) as $_chunk) {
+                $result .= base64_decode($_chunk);
+            }
+
+            return $result;
         }
 
         // QUOTED-PRINTABLE

tests/Framework/ImapGeneric.php

@@ -151,6 +151,26 @@ function test_decode_content_base64()
         $this->runDecodeContent($content, $encoded, 1, 6000);
     }
 
+    /**
+     * Test for decodeContent() with base64 encoding (multiple bodies)
+     */
+    public function test_decode_content_base64_multiple()
+    {
+        $expected = $content = str_repeat('a', 100);
+        $encoded = chunk_split(base64_encode($content), 72, "\r\n");
+
+        $expected .= ($content = str_repeat('b', 101));
+        $encoded .= chunk_split(base64_encode($content), 72, "\r\n");
+
+        $expected .= ($content = str_repeat('c', 102));
+        $encoded .= chunk_split(base64_encode($content), 72, "\r\n");
+
+        $expected .= ($content = str_repeat('d', 103));
+        $encoded .= chunk_split(base64_encode($content), 72, "\r\n");
+
+        $this->runDecodeContent($expected, $encoded, 1);
+    }
+
     /**
      * Test for decodeContent() with quoted-printable encoding
      */