bug#60295: [PATCH] Fix htmlfontify.el command injection vulnerability

[Stefan Kangas <stefankangas@gmail.com>]

tags 60295 + security
thanks

lux <lx@shellcodes.org> writes:

> From b97db7fc0d38595507ca78018724c769e873a469 Mon Sep 17 00:00:00 2001
> From: Xi Lu <lx@shellcodes.org>
> 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)))

Eli, is it okay to install this patch on the Emacs 29 branch?  It looks
safe, as it only adds shell quoting to a filename before it is fed to
`shell-command-to-string'.

But on master maybe we could avoid calling the shell altogether by using
something like this:

    (defun file-binary-p (filename)
      "Return t if FILENAME names a binary file.
    Return nil if FILENAME does not name a binary file, or if there
    was trouble determining whether FILENAME is a binary file."
      (when (and (file-readable-p filename)
                 (not (file-directory-p filename)))
        (catch 'binaryp
          (with-current-buffer (find-file-noselect filename t)
            (unwind-protect
                (throw 'binaryp (eq buffer-file-coding-system 'binary))
              (kill-buffer))))))