seccomp

seccomp (short for secure computing mode) is a computer security facility in the Linux kernel. seccomp allows a process to make a one-way transition into a "secure" state where it cannot make any system calls except exit(), sigreturn(), read() and write() to already-open file descriptors. Should it attempt any other system calls, the kernel will terminate the process with SIGKILL or SIGSYS.[1][2] In this sense, it does not virtualize the system's resources but isolates the process from them entirely.

seccomp
Original author(s)Andrea Arcangeli
Initial releaseMarch 8, 2005 (2005-03-08)
Written inC
Operating systemLinux
TypeSandboxing
LicenseGNU General Public License
Websitecode.google.com/archive/p/seccompsandbox/wikis/overview.wiki

seccomp mode is enabled via the prctl(2) system call using the PR_SET_SECCOMP argument, or (since Linux kernel 3.17[3]) via the seccomp(2) system call.[4] seccomp mode used to be enabled by writing to a file, /proc/self/seccomp, but this method was removed in favor of prctl().[5] In some kernel versions, seccomp disables the RDTSC x86 instruction, which returns the number of elapsed processor cycles since power-on, used for high-precision timing.[6]

seccomp-bpf is an extension to seccomp[7] that allows filtering of system calls using a configurable policy implemented using Berkeley Packet Filter rules. It is used by OpenSSH and vsftpd as well as the Google Chrome/Chromium web browsers on Chrome OS and Linux.[8] (In this regard seccomp-bpf achieves similar functionality, but with more flexibility and higher performance, to the older systrace—which seems to be no longer supported for Linux.)

History

seccomp was first devised by Andrea Arcangeli in January 2005 for use in public grid computing and was originally intended as a means of safely running untrusted compute-bound programs. It was merged into the Linux kernel mainline in kernel version 2.6.12, which was released on March 8, 2005.[9]

Software using seccomp or seccomp-bpf
  • Android uses a seccomp-bpf filter in the zygote since Android 8.0 Oreo.[10]
  • systemd's sandboxing options based on seccomp.[11]
  • QEMU, the Quick Emulator, the core component to the modern virtualization together with KVM uses seccomp on the parameter --sandbox[12]
  • Docker. Docker is a software that allows to run applications inside of isolated containers. Docker can associate a seccomp profile with the container using the --security-opt parameter.
  • Arcangeli's CPUShare was the only known user of seccomp for a while.[13] Writing in February 2009, Linus Torvalds expresses doubt whether seccomp is actually used by anyone.[14] However, a Google engineer replied that Google is exploring using seccomp for sandboxing its Chrome web browser.[15][16]
  • Firejail is an open source Linux sandbox program that utilizes Linux Namespaces, Seccomp, and other kernel-level security features to sandbox Linux and Wine applications.[17]
  • As of Chrome version 20, seccomp-bpf is used to sandbox Adobe Flash Player.[18]
  • As of Chrome version 23, seccomp-bpf is used to sandbox the renderers.[19]
  • Snap specify the shape of their application sandbox using 'interfaces' which snapd translates to seccomp, AppArmor and other security constructs[20]
  • vsftpd uses seccomp-bpf sandboxing as of version 3.0.0.[21]
  • OpenSSH has supported seccomp-bpf since version 6.0.[22]
  • Mbox uses ptrace along with seccomp-bpf to create a secure sandbox with less overhead than ptrace alone.[23]
  • LXD, an Ubuntu "hypervisor" for containers[24][25]
  • Firefox and Firefox OS, which use seccomp-bpf[26][27]
  • Tor supports seccomp since 0.2.5.1-alpha[28]
  • Lepton, a JPEG compression tool developed by Dropbox uses seccomp[29]
  • Kafel is a configuration language, which converts readable policies into seccompb-bpf bytecode[30]
  • Subgraph OS uses seccomp-bpf[31][32]
  • Flatpak uses seccomp for process isolation[33]
  • Bubblewrap is a lightweight sandbox application developed from Flatpak[34]
  • minijail uses seccomp for process isolation[35]
gollark: It's mostly used on SC, though, where ender chest bulk item-stealing is against the rules.
gollark: The thing is designed to only leave items in insecure public ender chests for ~0.1 seconds at most.
gollark: How fast did they check each channel, 10 times a second?
gollark: You would have to scan too fast.
gollark: While it *could* be intercepted, it would be impractical to do so.

References
  1. Corbet, Jonathan (2015-09-02). "A seccomp overview". lwn. Retrieved 2017-10-05.
  2. "Documentation/prctl/seccomp_filter.txt". Retrieved 2017-10-05.
  3. "Linux kernel 3.17, Section 11. Security". kernelnewbies.org. 2013-10-05. Retrieved 2015-03-31.
  4. "seccomp: add "seccomp" syscall". kernel/git/torvalds/linux.git - Linux kernel source tree. kernel.org. 2014-06-25. Retrieved 2014-08-22.
  5. Arcangeli, Andrea (2007-06-14). "[PATCH 1 of 2] move seccomp from /proc to a prctl". Retrieved 2013-08-02.
  6. Tinnes, Julien (2009-05-28). "Time-stamp counter disabling oddities in the Linux kernel". cr0 blog. Retrieved 2013-08-02.
  7. Corbet, Jonathan (2012-01-11). "Yet another new approach to seccomp". lwn. Retrieved 2013-08-02.
  8. Tinnes, Julien (2012-11-19). "A safer playground for your Linux and Chrome OS renderers". The Chromium Blog. Retrieved 2013-08-02.
  9. "[PATCH] seccomp: secure computing support". Linux kernel history. Kernel.org git repositories. 2005-03-08. Archived from the original on 2013-04-15. Retrieved 2013-08-02.
  10. "Seccomp filter in Android O". Android Developers Blog.
  11. "systemd.exec — Execution environment configuration". freedesktop.org. Retrieved 2017-10-14.
  12. Otubo, Eduardo (2017-09-15). "QEMU Sandboxing new model pull request". qemu-devel mailing list archive.
  13. van de Ven, Arjan (2009-02-28). "Re: [stable] [PATCH 2/2] x86-64: seccomp: fix 32/64 syscall hole". Linux Kernel Mailing List. Retrieved 2013-08-02.
  14. Torvalds, Linus (2009-02-28). "Re: [PATCH 2/2] x86-64: seccomp: fix 32/64 syscall hole". Linux Kernel Mailing List. Retrieved 2013-08-02.
  15. Gutschke, Markus (2009-05-06). "Re: [PATCH 2/2] x86-64: seccomp: fix 32/64 syscall hole". Retrieved 2013-08-02.
  16. Gutschke, Markus (2009-05-06). "Re: [PATCH 2/2] x86-64: seccomp: fix 32/64 syscall hole". Linux Kernel Mailing List. Retrieved 2013-08-02.
  17. "Firejail". Firejail. Retrieved 2016-11-26.
  18. Evans, Chris (2012-07-04). "Chrome 20 on Linux and Flash sandboxing". Retrieved 2013-08-02.
  19. Tinnes, Julien (2012-09-06). "Introducing Chrome's next-generation Linux sandbox". cr0 blog. Retrieved 2013-08-02.
  20. "Snap security policy". Archived from the original on 2017-02-04. Retrieved 2017-02-03.
  21. Evans, Chris (2012-04-09). "vsftpd-3.0.0 and seccomp filter sandboxing is here!". Retrieved 2013-08-02.
  22. "Openssh 6.0 release notes". Retrieved 2013-10-14.
  23. "MBOX". Retrieved 2014-05-20.
  24. "LXD an "hypervisor" for containers (based on liblxc)". Retrieved 2014-11-08.
  25. "Where We're Going With LXD". Retrieved 2014-11-08.
  26. Destuynder, Guillaume (2012-09-13). "Firefox Seccomp sandbox". Mozilla Bugzilla. Retrieved 2015-01-13.
  27. Destuynder, Guillaume (2012-09-13). "Firefox Seccomp sandbox". Mozilla Wiki. Retrieved 2015-01-13.
  28. "Tor ChangeLog".
  29. "Lepton image compression: saving 22% losslessly from images at 15MB/s". Dropbox Tech Blog. Retrieved 2016-07-15.
  30. "Kafel: A language and library for specifying syscall filtering policies".
  31. "Subgraph OS". Subgraph. Retrieved 2016-12-18.
  32. "LoganCIJ16: Future of OS". YouTube. Retrieved 2016-12-18.
  33. "The flatpak security model – part 1: The basics". Retrieved 2017-01-21.
  34. "bubblewrap". Retrieved 2018-04-14.
  35. "Minijail [LWN.net]". lwn.net. Retrieved 2017-04-11.
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