Re: Broken display of clearsigned PGP message

[Andreas Seltenreich <andreas+ding@gate450.dyndns.org>]

Reiner Steib writes:

> I'd suggest to add a rather detailed explanation about this problem
> and the relevant RFC in `mm-uu-pgp-signed-extract-1'.

Ok, I've added a comment and also made the fix a bit more thorough -
Instead of stripping everything until we see what we think is
separating the armor headers, we're now stripping everything that we
know for sure isn't part of the signed text.  That may be a bit
paranoid, but I've heard this is a must in the security business ;-).

regards,
andreas

*** mm-uu.el	28 Sep 2006 03:16:58 +0200	6.29.2.25
--- mm-uu.el	18 Nov 2006 04:03:40 +0100	
***************
*** 373,380 ****
  	   mm-security-handle 'gnus-details
  	   (format "Clear verification not supported by `%s'.\n" mml2015-use))))
        (goto-char (point-min))
!       (if (re-search-forward "\n[\t ]*\n" nil t)
! 	  (delete-region (point-min) (point)))
        (if (re-search-forward mm-uu-pgp-beginning-signature nil t)
  	  (delete-region (match-beginning 0) (point-max)))
        (goto-char (point-min))
--- 373,388 ----
  	   mm-security-handle 'gnus-details
  	   (format "Clear verification not supported by `%s'.\n" mml2015-use))))
        (goto-char (point-min))
!       (forward-line)
!       ;; We need to be careful not to strip beyond the armor headers.
!       ;; Previously, an attacker could replace the text inside our
!       ;; markup with trailing garbage by injecting whitespace into the
!       ;; message.
!       (while (looking-at "Hash:") ; The only header allowed in cleartext
! 	(forward-line))		  ; signatures according to RFC2440.
!       (when (looking-at "[\t ]*$")
! 	(forward-line))
!       (delete-region (point-min) (point))
        (if (re-search-forward mm-uu-pgp-beginning-signature nil t)
  	  (delete-region (match-beginning 0) (point-max)))
        (goto-char (point-min))