branch: externals-release/org
commit f4cc61636947b5c2f0afc67174dd369fe3277aa8
Author: Ihor Radchenko <[email protected]>
Commit: Ihor Radchenko <[email protected]>
org-link-expand-abbrev: Do not evaluate arbitrary unsafe Elisp code
* lisp/ol.el (org-link-expand-abbrev): Refuse expanding %(...) link
abbrevs that specify unsafe function. Instead, display a warning, and
do not expand the abbrev. Clear all the text properties from the
returned link, to avoid any potential vulnerabilities caused by
properties that may contain arbitrary Elisp.
---
lisp/ol.el | 40 +++++++++++++++++++++++++++++-----------
1 file changed, 29 insertions(+), 11 deletions(-)
diff --git a/lisp/ol.el b/lisp/ol.el
index 7a7f4f5589..8a556c7b97 100644
--- a/lisp/ol.el
+++ b/lisp/ol.el
@@ -1152,17 +1152,35 @@ Abbreviations are defined in `org-link-abbrev-alist'."
(if (not as)
link
(setq rpl (cdr as))
- (cond
- ((symbolp rpl) (funcall rpl tag))
- ((string-match "%(\\([^)]+\\))" rpl)
- (replace-match
- (save-match-data
- (funcall (intern-soft (match-string 1 rpl)) tag))
- t t rpl))
- ((string-match "%s" rpl) (replace-match (or tag "") t t rpl))
- ((string-match "%h" rpl)
- (replace-match (url-hexify-string (or tag "")) t t rpl))
- (t (concat rpl tag)))))))
+ ;; Drop any potentially dangerous text properties like
+ ;; `modification-hooks' that may be used as an attack vector.
+ (substring-no-properties
+ (cond
+ ((symbolp rpl) (funcall rpl tag))
+ ((string-match "%(\\([^)]+\\))" rpl)
+ (let ((rpl-fun-symbol (intern-soft (match-string 1 rpl))))
+ ;; Using `unsafep-function' is not quite enough because
+ ;; Emacs considers functions like `genenv' safe, while
+ ;; they can potentially be used to expose private system
+ ;; data to attacker if abbreviated link is clicked.
+ (if (or (eq t (get rpl-fun-symbol 'org-link-abbrev-safe))
+ (eq t (get rpl-fun-symbol 'pure)))
+ (replace-match
+ (save-match-data
+ (funcall (intern-soft (match-string 1 rpl)) tag))
+ t t rpl)
+ (org-display-warning
+ (format "Disabling unsafe link abbrev: %s
+You may mark function safe via (put '%s 'org-link-abbrev-safe t)"
+ rpl (match-string 1 rpl)))
+ (setq org-link-abbrev-alist-local (delete as
org-link-abbrev-alist-local)
+ org-link-abbrev-alist (delete as org-link-abbrev-alist))
+ link
+ )))
+ ((string-match "%s" rpl) (replace-match (or tag "") t t rpl))
+ ((string-match "%h" rpl)
+ (replace-match (url-hexify-string (or tag "")) t t rpl))
+ (t (concat rpl tag))))))))
(defun org-link-open (link &optional arg)
"Open a link object LINK.
