From 2db5d6b832df231383f73f105f6cb532f0ce1d8f Mon Sep 17 00:00:00 2001 From: Jacek Migacz Date: Mon, 5 May 2025 17:46:57 +0200 Subject: [PATCH] Fix arbitrary code execution via Lisp macro expansion Resolves: RHEL-69394 --- emacs-CVE-2024-53920.patch | 242 +++++++++++++++++++++++++++++++++++++ emacs.spec | 7 +- 2 files changed, 248 insertions(+), 1 deletion(-) create mode 100644 emacs-CVE-2024-53920.patch diff --git a/emacs-CVE-2024-53920.patch b/emacs-CVE-2024-53920.patch new file mode 100644 index 0000000..f50cfd8 --- /dev/null +++ b/emacs-CVE-2024-53920.patch @@ -0,0 +1,242 @@ +--- + emacs-27.2/doc/emacs/misc.texi | 33 +++++++++++++++++ + emacs-27.2/lisp/emacs-lisp/macroexp.el | 10 ++++- + emacs-27.2/lisp/files.el | 60 +++++++++++++++++++++++++++++--- + emacs-27.2/lisp/ielm.el | 3 + + emacs-27.2/lisp/progmodes/elisp-mode.el | 58 +++++++++++++++++++++++++----- + emacs-27.2/lisp/simple.el | 1 + 6 files changed, 189 insertions(+), 20 deletions(-) + +--- emacs-27.2/doc/emacs/misc.texi ++++ emacs-27.2/doc/emacs/misc.texi 2025-03-03 09:18:41.368169799 +0000 +@@ -279,6 +279,39 @@ trusted and the default checking for the + you can set @code{enable-local-variables} to @code{:all}. @xref{Safe + File Variables}. + ++@cindex trusted files and directories ++Loading a file of Emacs Lisp code with @code{load-file} or ++@code{load-library} (@pxref{Lisp Libraries}) can execute some of the ++Lisp code in the file being loaded, so you should only load Lisp files ++whose source you trust. However, some Emacs features can in certain ++situations execute Lisp code even without your explicit command or ++request. For example, Flymake, the on-the-fly syntax checker for Emacs ++(@pxref{Top,,, flymake, GNU Flymake}), if it is enabled, can ++automatically execute some of the code in a Lisp file you visit as part ++of its syntax-checking job. Similarly, some completion commands ++(@pxref{Completion}) in buffers visiting Lisp files sometimes need to ++expand Lisp macros for best results. In these cases, just visiting a ++Lisp file and performing some editing in it could trigger execution of ++Lisp code. If the visited file came from an untrusted source, it could ++include dangerous or even malicious code that Emacs would execute in ++those situations. ++ ++To protect against this, Emacs disables execution of Lisp code by ++Flymake, completion, and some other features, unless the visited file is ++@dfn{trusted}. It is up to you to specify which files on your system ++should be trusted, by customizing the user option ++@code{trusted-content}. ++ ++@defopt trusted-content ++The value of this option is @code{nil} by default, which means no file ++is trusted. You can customize the variable to be a list of one or more ++names of trusted files and directories. A file name that ends in a ++slash @file{/} is interpreted as a directory, which means all its files ++and subdirectories are also trusted. A special value @code{:all} means ++@emph{all} the files and directories on your system should be trusted; ++@strong{this is not recommended}, as it opens a gaping security hole. ++@end defopt ++ + @xref{Security Considerations,,, elisp, The Emacs Lisp Reference + Manual}, for more information about security considerations when using + Emacs as part of a larger application. +--- emacs-27.2/lisp/emacs-lisp/macroexp.el ++++ emacs-27.2/lisp/emacs-lisp/macroexp.el 2025-03-03 09:18:41.368169799 +0000 +@@ -94,12 +94,20 @@ each clause." + (macroexp--all-forms clause skip) + clause))) + ++(defvar macroexp-inhibit-compiler-macros nil ++ "Inhibit application of compiler macros if non-nil.") ++ + (defun macroexp--compiler-macro (handler form) ++ "Apply compiler macro HANDLER to FORM and return the result. ++Unless `macroexp-inhibit-compiler-macros' is non-nil, in which ++case return FORM unchanged." ++ (if macroexp-inhibit-compiler-macros ++ form + (condition-case err + (apply handler form (cdr form)) + (error + (message "Compiler-macro error for %S: %S" (car form) err) +- form))) ++ form)))) + + (defun macroexp--funcall-if-compiled (_form) + "Pseudo function used internally by macroexp to delay warnings. +--- emacs-27.2/lisp/files.el ++++ emacs-27.2/lisp/files.el 2025-03-03 09:20:04.078645249 +0000 +@@ -591,10 +596,57 @@ buffer contents as untrusted. + (other :tag "Query" other)) + :group 'find-file) + +-(defvar enable-dir-local-variables t +- "Non-nil means enable use of directory-local variables. +-Some modes may wish to set this to nil to prevent directory-local +-settings being applied, but still respect file-local ones.") ++(defcustom trusted-content nil ++ "List of files and directories whose content we trust. ++Be extra careful here since trusting means that Emacs might execute the ++code contained within those files and directories without an explicit ++request by the user. ++One important case when this might happen is when `flymake-mode' is ++enabled (for example, when it is added to a mode hook). ++Each element of the list should be a string: ++- If it ends in \"/\", it is considered as a directory name and means that ++ Emacs should trust all the files whose name has this directory as a prefix. ++- Otherwise, it is considered a file name. ++Use abbreviated file names. For example, an entry \"~/mycode/\" means ++that Emacs will trust all the files in your directory \"mycode\". ++This variable can also be set to `:all', in which case Emacs will trust ++all files, which opens a gaping security hole. Emacs Lisp authors ++should note that this value must never be set by a major or minor mode." ++ :type '(choice (repeat :tag "List" file) ++ (const :tag "Trust everything (DANGEROUS!)" :all)) ++ :version "27.2") ++(put 'trusted-content 'risky-local-variable t) ++ ++(defun trusted-content-p () ++ "Return non-nil if we trust the contents of the current buffer. ++Here, \"trust\" means that we are willing to run code found inside of it. ++See also `trusted-content'." ++ ;; We compare with `buffer-file-truename' i.s.o `buffer-file-name' ++ ;; to try and avoid marking as trusted a file that's merely accessed ++ ;; via a symlink that happens to be inside a trusted dir. ++ (and (not untrusted-content) ++ (or ++ (eq trusted-content :all) ++ (and ++ buffer-file-truename ++ (with-demoted-errors "trusted-content-p: %S" ++ (let ((exists (file-exists-p buffer-file-truename))) ++ (or ++ ;; We can't avoid trusting the user's init file. ++ (if (and exists user-init-file) ++ (file-equal-p buffer-file-truename user-init-file) ++ (equal buffer-file-truename user-init-file)) ++ (let ((file (abbreviate-file-name buffer-file-truename)) ++ (trusted nil)) ++ (dolist (tf trusted-content) ++ (when (or (if exists (file-equal-p tf file) (equal tf file)) ++ ;; We don't use `file-in-directory-p' here, because ++ ;; we want to err on the conservative side: "guilty ++ ;; until proven innocent". ++ (and (string-suffix-p "/" tf) ++ (string-prefix-p tf file))) ++ (setq trusted t))) ++ trusted)))))))) + + ;; This is an odd variable IMO. + ;; You might wonder why it is needed, when we could just do: +--- emacs-27.2/lisp/ielm.el ++++ emacs-27.2/lisp/ielm.el 2025-03-03 09:18:41.372169725 +0000 +@@ -616,7 +616,8 @@ See `inferior-emacs-lisp-mode' for detai + (unless (comint-check-proc "*ielm*") + (with-current-buffer (get-buffer-create "*ielm*") + (unless (zerop (buffer-size)) (setq old-point (point))) +- (inferior-emacs-lisp-mode))) ++ (inferior-emacs-lisp-mode) ++ (setq-local trusted-content :all))) + (pop-to-buffer-same-window "*ielm*") + (when old-point (push-mark old-point)))) + +--- emacs-27.2/lisp/progmodes/elisp-mode.el ++++ emacs-27.2/lisp/progmodes/elisp-mode.el 2025-03-03 09:18:41.372169725 +0000 +@@ -333,6 +333,43 @@ Blank lines separate paragraphs. Semico + + (defvar warning-minimum-log-level) + ++(defvar elisp--local-macroenv ++ `((cl-eval-when . ,(lambda (&rest args) `(progn . ,(cdr args)))) ++ (eval-when-compile . ,(lambda (&rest args) `(progn . ,args))) ++ (eval-and-compile . ,(lambda (&rest args) `(progn . ,args)))) ++ "Environment to use while tentatively expanding macros. ++This is used to try and avoid the most egregious problems linked to the ++use of `macroexpand-all' as a way to find the \"underlying raw code\".") ++ ++(defvar elisp--macroexpand-untrusted-warning t) ++ ++(defun elisp--safe-macroexpand-all (sexp) ++ (if (not (trusted-content-p)) ++ ;; FIXME: We should try and do better here, either using a notion ++ ;; of "safe" macros, or with `bwrap', or ... ++ (progn ++ (when elisp--macroexpand-untrusted-warning ++ (setq-local elisp--macroexpand-untrusted-warning nil) ;Don't spam! ++ (let ((inhibit-message t)) ;Only log. ++ (message "Completion of local vars is disabled in %s (untrusted content)" ++ (buffer-name)))) ++ sexp) ++ (let ((macroexpand-advice ++ (lambda (expander form &rest args) ++ (condition-case err ++ (apply expander form args) ++ (error ++ (message "Ignoring macroexpansion error: %S" err) form))))) ++ (unwind-protect ++ ;; Silence any macro expansion errors when ++ ;; attempting completion at point (bug#58148). ++ (let ((inhibit-message t) ++ (macroexp-inhibit-compiler-macros t) ++ (warning-minimum-log-level :emergency)) ++ (advice-add 'macroexpand-1 :around macroexpand-advice) ++ (macroexpand-all sexp elisp--local-macroenv)) ++ (advice-remove 'macroexpand-1 macroexpand-advice))))) ++ + (defun elisp--local-variables () + "Return a list of locally let-bound variables at point." + (save-excursion +@@ -348,17 +385,8 @@ Blank lines separate paragraphs. Semico + (car (read-from-string + (concat txt "elisp--witness--lisp" closer))) + ((invalid-read-syntax end-of-file) nil))) +- (macroexpand-advice (lambda (expander form &rest args) +- (condition-case nil +- (apply expander form args) +- (error form)))) +- (sexp +- (unwind-protect +- (let ((warning-minimum-log-level :emergency)) +- (advice-add 'macroexpand :around macroexpand-advice) +- (macroexpand-all sexp)) +- (advice-remove 'macroexpand macroexpand-advice))) +- (vars (elisp--local-variables-1 nil sexp))) ++ (vars (elisp--local-variables-1 ++ nil (elisp--safe-macroexpand-all sexp)))) + (delq nil + (mapcar (lambda (var) + (and (symbolp var) +@@ -1721,6 +1749,14 @@ directory of the buffer being compiled, + "A Flymake backend for elisp byte compilation. + Spawn an Emacs process that byte-compiles a file representing the + current buffer state and calls REPORT-FN when done." ++ (unless (trusted-content-p) ++ ;; FIXME: Use `bwrap' and friends to compile untrusted content. ++ ;; FIXME: We emit a message *and* signal an error, because by default ++ ;; Flymake doesn't display the warning it puts into "*flmake log*". ++ (message "Disabling elisp-flymake-byte-compile in %s (untrusted content)" ++ (buffer-name)) ++ (error "Disabling elisp-flymake-byte-compile in %s (untrusted content)" ++ (buffer-name))) + (when elisp-flymake--byte-compile-process + (when (process-live-p elisp-flymake--byte-compile-process) + (kill-process elisp-flymake--byte-compile-process))) +--- emacs-27.2/lisp/simple.el ++++ emacs-27.2/lisp/simple.el 2025-03-03 09:18:41.372169725 +0000 +@@ -1621,6 +1621,7 @@ display the result of expression evaluat + (eldoc-mode 1) + (add-hook 'completion-at-point-functions + #'elisp-completion-at-point nil t) ++ (setq-local trusted-content :all) + (run-hooks 'eval-expression-minibuffer-setup-hook)) + (read-from-minibuffer prompt initial-contents + read-expression-map t diff --git a/emacs.spec b/emacs.spec index 9e3bd87..95ba9b0 100644 --- a/emacs.spec +++ b/emacs.spec @@ -5,7 +5,7 @@ Summary: GNU Emacs text editor Name: emacs Epoch: 1 Version: 26.1 -Release: 13%{?dist} +Release: 14%{?dist} License: GPLv3+ and CC0-1.0 URL: http://www.gnu.org/software/emacs/ Group: Applications/Editors @@ -33,6 +33,7 @@ Patch8: emacs-consider-org-file-contents-unsafe.patch Patch9: emacs-org-link-expand-abbrev-unsafe-elisp.patch Patch10: emacs-mark-contents-untrusted.patch Patch11: emacs-man-el-shell-injection-vulnerability.patch +Patch12: emacs-CVE-2024-53920.patch BuildRequires: atk-devel BuildRequires: cairo-devel @@ -195,6 +196,7 @@ packages that add functionality to Emacs. %patch9 -p1 -b .org-link-expand-abbrev-unsafe-elisp %patch10 -p1 -b .mark-contents-untrusted %patch11 -p1 -b .emacs-man-el-shell-injection-vulnerability +%patch12 -p1 -b .CVE-2024-53920 autoconf # We prefer our emacs.desktop file @@ -481,6 +483,9 @@ fi %dir %{_datadir}/emacs/site-lisp/site-start.d %changelog +* Mon May 05 2025 Jacek Migacz - 1:26.1-14 +- Fix arbitrary code execution via Lisp macro expansion (RHEL-69394) + * Wed Feb 19 2025 Jacek Migacz - 1:26.1-13 - Fix man.el shell injection vulnerability (RHEL-79016)