Skip to content

vyos-op-run: T8005: sanitize environment variables to prevent malicious variable injection #46

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
jestabro merged 1 commit into from
Nov 12, 2025
Merged

vyos-op-run: T8005: sanitize environment variables to prevent malicious variable injection #46

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 6 additions & 0 deletions debian/changelog
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,3 +1,9 @@
vyos-utils (0.0.5) unstable; urgency=medium

* Sanitize the environment in vyos-op-run to prevent malicious variable injection

-- Daniil Baturin <daniil@vyos.io> Tue, 11 Nov 2025 13:46:05 +0000

vyos-utils (0.0.4) unstable; urgency=medium

* Add an operational command runner.
Expand Down
34 changes: 33 additions & 1 deletion src/vyos_op_run.ml
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -319,7 +319,39 @@ let run_external_command opts env command_tmpl =
let cmd = render_command opts env command_tmpl in
if opts.dry_run then Printf.printf "%s\n%!" cmd else
let () = Logs.debug @@ fun m -> m "Command to be executed %s" cmd in
let res = Unix.system cmd in
(* Get the user database entry to populate the basic environment from:
we cannot trust an unprivileged user to supply $SHELL
or allow them to impersonate someone else by setting custom $LOGNAME, etc.
*)
let user_pw_entry = Unix.getpwuid @@ Unix.getuid () in
let make_var name value = Printf.sprintf "%s=%s" name value in
let env = [|
(* A knowingly safe executable lookup path.
Since we do not use /usr/local, we do not need to include that.
Executables in VyOS-specific directories are referred to by absolute paths
in the operational command JSON cache,
so we don't need to include those, either.
*)
make_var "PATH" "/usr/sbin:/usr/bin:/sbin:/bin";
(* Standard UNIX variables *)
make_var "HOME" user_pw_entry.pw_dir;
make_var "USER" user_pw_entry.pw_name;
make_var "LOGNAME" user_pw_entry.pw_name;
make_var "SHELL" user_pw_entry.pw_shell;
(* VyOS-specific variables *)
make_var "vyos_data_dir" "/usr/share/vyos";
make_var "vyos_validators_dir" "/usr/libexec/vyos/validators";
make_var "vyos_completion_dir" "/usr/libexec/vyos/completion";
make_var "vyos_libexec_dir" "/usr/libexec/vyos";
make_var "vyos_op_scripts_dir" "/usr/libexec/vyos/op_mode";
|]
in
let shell = "/bin/sh" in
(* We use execve with an absolute path to Bourne shell rather than execvpe
so that a user trying to do PATH=/bad/place vyos-op-run
cannot achieve anything with that trick.
*)
let res = Unix.execve shell [|shell; "-c"; cmd|] env in
match res with
| Unix.WEXITED 0 -> ()
| _ ->
Expand Down