Subject: [PATCH] Fix htmlfontify.el command injection vulnerability
From: lux <[email-masked]>
To: [email-masked]
Date: Sat, 24 Dec 2022 17:03:09 +0800
List-Id: <debbugs-submit.debbugs.gnu.org>

Test information:
Emacs version: GNU Emacs 29.0.60
OS: Fedora Linux 37

htmlfontify.el has a command injection vulnerability:

(defcustom hfy-istext-command "file %s | sed -e 's@^[^:]*:[ \t]*@@'"
  :tag   "istext-command"
  :type  '(string))

(defun hfy-text-p (srcdir file)
  (let* ((cmd (format hfy-istext-command (expand-file-name file
srcdir))) (rsp (shell-command-to-string    cmd)))
    ...))

Parameter 'file' and parameter 'srcdir' come from external input, and 
parameters are not escape. So, if file name or directory name contains
shell characters and will be executed.

For example:

$ mkdir vul_test
$ cd vul_test
$ echo hello > ";uname>hack.txt#"
$ ls
;uname>hack.txt#

In Emacs, type M-x htmlfontify-copy-and-link-dir, and inputing vul_test
path, at this time, hack.txt is added to the vul_test directory:

$ ls
;uname>hack.txt#  hack.txt#
$ cat hack.txt\#
Linux

The attachment is the patch file, thanks.

From b97db7fc0d38595507ca78018724c769e873a469 Mon Sep 17 00:00:00 2001
From: Xi Lu <[email-masked]>
Date: Sat, 24 Dec 2022 16:28:54 +0800
Subject: [PATCH] Fix htmlfontify.el command injection vulnerability.

* lisp/htmlfontify.el
(hfy-text-p): Fix command injection vulnerability.
---
 lisp/htmlfontify.el | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lisp/htmlfontify.el b/lisp/htmlfontify.el
index df4c6ab079..389b92939c 100644
--- a/lisp/htmlfontify.el
+++ b/lisp/htmlfontify.el
@@ -1850,7 +1850,7 @@ hfy-make-directory
 
 (defun hfy-text-p (srcdir file)
   "Is SRCDIR/FILE text?  Use `hfy-istext-command' to determine this."
-  (let* ((cmd (format hfy-istext-command (expand-file-name file srcdir)))
+  (let* ((cmd (format hfy-istext-command (shell-quote-argument (expand-file-name file srcdir))))
          (rsp (shell-command-to-string    cmd)))
     (string-match "text" rsp)))
 
-- 
2.38.1