Fix viewing of encrypted S/MIME messages

* lisp/gnus/mm-decode.el (mm-possibly-verify-or-decrypt): Don't
add a content-type header if there already is one (bug#41659).

diff --git a/lisp/gnus/mm-decode.el b/lisp/gnus/mm-decode.el
index d33bb56dc9ee86437c9dfaa4cfb2bc888ecedaa9..a340418507fb7b58bfee82c399215b1e1296db3b 100644 (file)
--- a/lisp/gnus/mm-decode.el
+++ b/lisp/gnus/mm-decode.el
@@ -1680,8 +1680,14 @@ If RECURSIVE, search recursively."
                    (t (y-or-n-p
                        (format "Decrypt (S/MIME) part? "))))
                   (mm-view-pkcs7 parts from))
-         (goto-char (point-min))
-         (insert "Content-type: text/plain\n\n")
+         ;; Normally there will be a Content-type header here, but
+         ;; some mailers don't add that to the encrypted part, which
+         ;; makes the subsequent re-dissection fail here.
+         (save-restriction
+           (mail-narrow-to-head)
+           (unless (mail-fetch-field "content-type")
+             (goto-char (point-max))
+             (insert "Content-type: text/plain\n\n")))
          (setq parts (mm-dissect-buffer t)))))
      ((equal subtype "signed")
       (unless (and (setq protocol