Max Nikulin <maniku...@gmail.com> writes: > On 22/08/2023 16:46, Ihor Radchenko wrote: >> See the updated version of the patches attached. > > Thank you, I do not see apparent issues with code any more. Commit > message needs an update, apostrophes in the doc string should be > escaped. Feel free to ignore other comments since there are other issues > and investing excessive time into polishing of this one is not reasonable.
Thanks for the feedback! I have updated the patch, except for the comments I reply to below. >> + `(org-make-shell-command \"command\" \"-l\" >> + \"value with spaces\" >> + (,org-shell-arg-tag-unescaped \"$HOME\") >> + (mapcar #'identity files))) > > Is `mapcar' necessary here? Anyway `delq' is called on another result of > `mapcar', so the function should not do any destructive list modification. The idea was to highlight that `files' is a list. I now changed this to files ; list variable > An idea that may be ignored: make the constant internal and add > (defsubst org-make-shell-command-unescaped (arg) > (list org--shell-arg-tag-unescaped arg)) > > to avoid `, noise in `(,org-shell-arg-tag-unescaped STRING). Good idea. I also converted `org-make-shell-command' into defsubst that cannot be reliably adviced. To reduce attack vectors further. >> +will shell-escape \"-l\", \"value with spaces\", and each non-nil member of > > There is nothing to escape in "-l". I deliberately list all the arguments, detailing which are escaped and which are not. > Perhaps it deserves a mention that COMMAND is passed unquoted to be > suitable for commands with arguments as defcustom user option values. To > escape it pass nil as fist argument and add COMMAND before ARGS. >> - (org-fill-template > > Should an explicit warning be added to `org-fill-template' that enough > care is required to escape values if it is used to build a shell command? I don't think so. `org-fill-template' is usually not used to build shell command. ob-sqlite is the only instance of such use in Org code. Other backends use different Elisp means to build shell command strings. So, adding warning to `org-fill-template' docstring will not achieve much. The new version of the org-macs patch attached.
>From 9e0128b205f568795d8c4688a7a94c175b1b2007 Mon Sep 17 00:00:00 2001 Message-ID: <9e0128b205f568795d8c4688a7a94c175b1b2007.1693295856.git.yanta...@posteo.net> From: Ihor Radchenko <yanta...@posteo.net> Date: Mon, 21 Aug 2023 09:57:50 +0300 Subject: [PATCH] org-macs: New common API function to quote shell arguments * lisp/org-macs.el (org-shell-arg-tag-unescaped): New auxiliary constant. (org-make-shell-command): New function that returns shell command built from individual shell arguments, escaping them to prevent malicious code execution. Link: https://orgmode.org/list/ub549k$q11$1...@ciao.gmane.io --- lisp/org-macs.el | 51 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 51 insertions(+) diff --git a/lisp/org-macs.el b/lisp/org-macs.el index 907e8bed7..6bcd393ce 100644 --- a/lisp/org-macs.el +++ b/lisp/org-macs.el @@ -1593,6 +1593,57 @@ (defun org-sxhash-safe (obj &optional counter) (puthash hash obj org-sxhash-objects) (puthash obj hash org-sxhash-hashes))))) +;; We use `gensym' to avoid malicious code know in advance the symbol +;; used to prevent escaping. +(defconst org-shell-arg-tag-unescaped (gensym "literal") + "Symbol to be used to mark shell arguments that should not be escaped. +See `org-make-shell-command'.") +;; We are deliberately using `defsubst' below, to make it harder to +;; advice this function. +(defsubst org-shell-arg-unescaped (string-arg) + "Mark STRING-ARG argument to be unescaped in `org-make-shell-command'." + (list org-shell-arg-tag-unescaped string-arg)) +(defsubst org-make-shell-command (command &rest args) + "Build safe shell command string to run COMMAND with ARGS. + +The resulting shell command is safe against malicious shell expansion. + +This function is used to avoid unexpected shell expansion when +building shell command using header arguments from Org babel blocks. + +ARGS can be nil, strings, the return value of (org-shell-arg-unescaped +STRING), or a list of such elements. For example, + + (let ((files \\='(\"a.txt\" \"b.txt\" nil \"$HOME.txt\"))) + (org-make-shell-command \"command\" \"-l\" + \"value with spaces\" + (org-shell-arg-unescaped \"$HOME\") + files ; list variable + )) + +will shell-escape \"-l\", \"value with spaces\", and each non-nil member of +FILES list, but leave \"$HOME\" to be shell-expanded. + +COMMAND itself can contain shell expansion constructs - no escaping +will be performed." + (concat + command (when command " ") + (mapconcat + #'identity + (delq + nil + (mapcar + (lambda (str-def) + (pcase str-def + (`nil nil) + ((pred stringp) (shell-quote-argument str-def)) + (`(,(pred (eq org-shell-arg-tag-unescaped)) ,(and (pred stringp) str)) + str) + ((pred listp) (apply #'org-make-shell-command nil str-def)) + (_ (error "Unknown ARG specification: %S" str-def)))) + args)) + " "))) + (defun org-compile-file (source process ext &optional err-msg log-buf spec) "Compile a SOURCE file using PROCESS. -- 2.42.0
-- Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at <https://orgmode.org/>. Support Org development at <https://liberapay.com/org-mode>, or support my work at <https://liberapay.com/yantar92>