[balsa] IMAP: fix multipart crypto operations

[Albrecht Dreß <albrecht src gnome org>]

commit f4fcbcffa24eab2283e2da38c447421c2c249d1d
Author: Albrecht Dreß <albrecht dress arcor de>
Date:   Sun Jan 24 16:41:09 2021 +0100

    IMAP: fix multipart crypto operations
    
    Enforce loading the whole IMAP message iff the MIME type is
    multipart/(encrypted|multipart).  Rationale: loading only the first part
    of such messages prevents decryption or signature check.
    
    Signed-off-by: Albrecht Dreß <albrecht dress arcor de>

 libbalsa/mailbox_imap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/libbalsa/mailbox_imap.c b/libbalsa/mailbox_imap.c
index c672b1686..dbe4091d8 100644
--- a/libbalsa/mailbox_imap.c
+++ b/libbalsa/mailbox_imap.c
@@ -2235,7 +2235,9 @@ libbalsa_mailbox_imap_fetch_structure(LibBalsaMailbox *mailbox,
        LIBBALSA_MESSAGE_GET_LENGTH(message)<8192 ||
         (headers != NULL &&
          (headers->content_type == NULL ||
-          !g_mime_content_type_is_type(headers->content_type, "multipart", "*"))) ){
+          !g_mime_content_type_is_type(headers->content_type, "multipart", "*") ||
+                 g_mime_content_type_is_type(headers->content_type, "multipart", "signed") ||
+                 g_mime_content_type_is_type(headers->content_type, "multipart", "encrypted"))) ){
         /* we could optimize this part a little bit: we do not need to
          * keep reopening the stream. */
         GMimeStream *stream =