https://github.com/hartwork/antijack
:ninja: seccomp-based anti-TTY-hijacking proof-of-concept (prevents TIOCSTI and TIOCLINUX)
https://github.com/hartwork/antijack
c99 command-injection doas ioctl libseccomp linux seccomp seccomp-filter seccomp-filtering seccomp-tools security sudo syscall-filter syscalls tioclinux tiocsti tty
Last synced: about 1 month ago
JSON representation
:ninja: seccomp-based anti-TTY-hijacking proof-of-concept (prevents TIOCSTI and TIOCLINUX)
- Host: GitHub
- URL: https://github.com/hartwork/antijack
- Owner: hartwork
- License: apache-2.0
- Created: 2023-03-14T19:12:44.000Z (over 2 years ago)
- Default Branch: main
- Last Pushed: 2025-08-18T17:38:50.000Z (2 months ago)
- Last Synced: 2025-08-18T19:28:48.039Z (2 months ago)
- Topics: c99, command-injection, doas, ioctl, libseccomp, linux, seccomp, seccomp-filter, seccomp-filtering, seccomp-tools, security, sudo, syscall-filter, syscalls, tioclinux, tiocsti, tty
- Language: C
- Homepage:
- Size: 78.1 KB
- Stars: 11
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: COPYING
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README
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# What is antijack?
**antijack** was inspired by [ttyjack](https://github.com/jwilk/ttyjack)
and is its counterpart in some sense, hence the name.
**antijack**'s mission is threefold:
- demo execution of a program in a way where it *cannot* inject
commands via ioctls `TIOCSTI` and/or `TIOCLINUX`
into the surrounding controlling terminal,
e.g. try `antijack ttyjack echo nope`.
- generate and dump a seccomp syscall filter (a BPF program)
that blocks ioctls `TIOCSTI` and `TIOCLINUX`
into a file for use with
e.g. [bubblewrap](https://github.com/containers/bubblewrap)
a la `bwrap --seccomp 3 [..] 3< <(antijack --dump /dev/stdout)`.
- demo mitigation at syscall level for Linux leveraging
[libseccomp](https://github.com/seccomp/libseccomp).
**May not be enough!**, more on that below.
It should be noted that:
- Alternative options for mitigation include:
- `setsid(2)` (or `setsid(1)`) with drawbacks or
- use of a PTY.
- With security in mind, we need to ask
"why should access to the controlling terminal be granted?"
not "why should it be taken away?"
Use of a PTY by default is a consequence of that.
The fact that `TIOCLINUX` attacks came to awareness later than `TIOCSTI`
indicates that when the next attack like these will be discovered,
those who are blocking single ioctls will have to adjust while
those using a PTY may already by protected.
- The defaults for `su` and `sudo` are known-vulnerable as of 2023-03-16.
- For `su` it takes `--pty`.
- For `sudo` it takes `Defaults use_pty` in `/etc/sudoers`.
- Both util-linux and GNU coreutils have reverted their
use of [libseccomp](https://github.com/seccomp/libseccomp) for mitigation:
- https://github.com/util-linux/util-linux/commit/23f75093264aae5d58d61016cb1a29d8ebdfa157
- https://github.com/coreutils/coreutils/commit/f5d7c0842ef7adc2be6e85f9ef66b35ebbbd6a61
- The syscall filter is easy to mis-implement,
e.g. see [CVE-2019-10063](https://nvd.nist.gov/vuln/detail/CVE-2019-10063)
and/or
[commit 5f6bd3aa6e6a15f644923afa66fb0068736e2b8d](https://github.com/hartwork/antijack/commit/5f6bd3aa6e6a15f644923afa66fb0068736e2b8d).
# Requirements
- C99 compiler
- Linux build and target host
- glibc ≥ 2.32
- GNU make
- [libseccomp](https://github.com/seccomp/libseccomp)
# How to compile
```
$ make
```
# Example output (on `x86_64`)
```
$ antijack --help
usage: antijack [-v|--verbose] [-o|--dump PATH.bpf] [--] [COMMAND [ARG ..]]
or: antijack -h|--help
$ antijack -v -- ttyjack echo nope
[*] Initializing libseccomp...
[+] Done.
[*] Adding rule block TIOCSTI ioctls...
[+] Done.
[*] Adding rule block TIOCLINUX ioctls...
[+] Done.
[*] Loading seccomp rules into the kernel...
#
# pseudo filter code start
#
# filter for arch x86_64 (3221225534)
if ($arch == 3221225534)
# filter for syscall "ioctl" (16) [priority: 65532]
if ($syscall == 16)
if ($a1.hi32 & 0x00000000 == 0)
if ($a1.lo32 & 0xffffffff == 21532)
action KILL_PROCESS;
if ($a1.lo32 & 0xffffffff == 21522)
action KILL_PROCESS;
# default action
action ALLOW;
# invalid architecture action
action KILL;
#
# pseudo filter code end
#
[+] Done.
[*] Releasing libseccomp...
[+] Done.
[*] Running ttyjack...
Bad system call
$ antijack --dump filter.bpf
$ wc -c < filter.bpf
112
```
# Related CVEs (not mine)
- [CVE-2005-4890](https://nvd.nist.gov/vuln/detail/CVE-2005-4890) for `su` of util-linux and `sudo`
- [CVE-2006-7098](https://nvd.nist.gov/vuln/detail/CVE-2006-7098) for Apache
- [CVE-2007-1400](https://nvd.nist.gov/vuln/detail/CVE-2007-1400) for [plash](https://github.com/mseaborn/plash)
- [CVE-2011-1408](https://nvd.nist.gov/vuln/detail/CVE-2011-1408) for `ikiwiki-mass-rebuild` of ikiwiki
- [CVE-2013-6409](https://nvd.nist.gov/vuln/detail/CVE-2013-6409) for [adequate](https://packages.debian.org/sid/adequate)
- [CVE-2016-2568](https://nvd.nist.gov/vuln/detail/CVE-2016-2568) for `pkexec` of Polkit
- [CVE-2016-2779](https://nvd.nist.gov/vuln/detail/CVE-2016-2779) for `runuser` of util-linux
- [CVE-2016-2781](https://nvd.nist.gov/vuln/detail/CVE-2016-2781) for `chroot` of GNU Coreutils
- [CVE-2016-7545](https://nvd.nist.gov/vuln/detail/CVE-2016-7545) for `policycoreutils` of SELinux
- [CVE-2016-9016](https://nvd.nist.gov/vuln/detail/CVE-2016-9016) for Firejail
- [CVE-2016-10124](https://nvd.nist.gov/vuln/detail/CVE-2016-10124) for `lxc-attach` of LXC
- [CVE-2016-?????](https://debbugs.gnu.org/cgi/bugreport.cgi?bug=24541) for `runcon` of GNU Coreutils
- [CVE-2017-5226](https://nvd.nist.gov/vuln/detail/CVE-2017-5226) for bubblewrap (or Flatpak)
- [CVE-2019-7303](https://nvd.nist.gov/vuln/detail/CVE-2019-7303) for `snapd` of Snap
- [CVE-2019-10063](https://nvd.nist.gov/vuln/detail/CVE-2019-10063) for Flatpak
- [CVE-2019-11460](https://nvd.nist.gov/vuln/detail/CVE-2019-11460) for `gnome-desktop` of GNOME
- [CVE-2019-11461](https://nvd.nist.gov/vuln/detail/CVE-2019-11461) for Nautilus of GNOME
- [CVE-2020-13753](https://nvd.nist.gov/vuln/detail/CVE-2020-13753) for WebKitGTK
- [CVE-2021-?????](https://hackerone.com/reports/1283871) for Homebrew
- [CVE-2023-28100](https://nvd.nist.gov/vuln/detail/CVE-2023-28100) for Flatpak
- [CVE-2023-28339](https://nvd.nist.gov/vuln/detail/CVE-2023-28339) for OpenDoas
- [CVE-2023-?????](https://github.com/slicer69/doas/issues/110) for doas (except on OpenBSD >=6.2)
- [CVE-2023-46277](https://nvd.nist.gov/vuln/detail/CVE-2023-46277) for pleaser/please
- [CVE-2023-?????](https://github.com/illiliti/ssu/issues/13) for ssu
- [CVE-2023-?????](https://github.com/memorysafety/sudo-rs/issues/159) for sudo-rs
---
[Sebastian Pipping](https://github.com/hartwork), Berlin, 2023