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seccomp.md

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Seccomp security profiles for Docker

The seccomp() system call operates on the Secure Computing (seccomp) state of the calling process.

This operation is available only if the kernel is configured with CONFIG_SECCOMP enabled.

This allows for allowing or denying of certain syscalls in a container.

Passing a profile for a container

Users may pass a seccomp profile using the security-opt option (per-container).

The profile has layout in the following form:

{
    "defaultAction": "SCMP_ACT_ALLOW",
    "syscalls": [
        {
            "name": "getcwd",
            "action": "SCMP_ACT_ERRNO"
        },
        {
            "name": "mount",
            "action": "SCMP_ACT_ERRNO"
        },
        {
            "name": "setns",
            "action": "SCMP_ACT_ERRNO"
        },
        {
            "name": "create_module",
            "action": "SCMP_ACT_ERRNO"
        },
        {
            "name": "chown",
            "action": "SCMP_ACT_ERRNO"
        },
        {
            "name": "chmod",
            "action": "SCMP_ACT_ERRNO"
        }
    ]
}

Then you can run with:

$ docker run --rm -it --security-opt seccomp:/path/to/seccomp/profile.json hello-world

Default Profile

The default seccomp profile provides a sane default for running containers with seccomp. It is moderately protective while providing wide application compatibility.

Overriding the default profile for a container

You can pass unconfined to run a container without the default seccomp profile.

$ docker run --rm -it --security-opt seccomp:unconfined debian:jessie \
    unshare --map-root-user --user sh -c whoami

Syscalls blocked by the default profile

Docker's default seccomp profile is a whitelist which specifies the calls that are allowed. The table below lists the significant (but not all) syscalls that are effectively blocked because they are not on the whitelist. The table includes the reason each syscall is blocked rather than white-listed.

Syscall Description
acct Accounting syscall which could let containers disable their own resource limits or process accounting. Also gated by CAP_SYS_PACCT.
add_key Prevent containers from using the kernel keyring, which is not namespaced.
adjtimex Similar to clock_settime and settimeofday, time/date is not namespaced.
bpf Deny loading potentially persistent bpf programs into kernel, already gated by CAP_SYS_ADMIN.
clock_adjtime Time/date is not namespaced.
clock_settime Time/date is not namespaced.
clone Deny cloning new namespaces. Also gated by CAP_SYS_ADMIN for CLONE_* flags, except CLONE_USERNS.
create_module Deny manipulation and functions on kernel modules.
delete_module Deny manipulation and functions on kernel modules. Also gated by CAP_SYS_MODULE.
finit_module Deny manipulation and functions on kernel modules. Also gated by CAP_SYS_MODULE.
get_kernel_syms Deny retrieval of exported kernel and module symbols.
get_mempolicy Syscall that modifies kernel memory and NUMA settings. Already gated by CAP_SYS_NICE.
init_module Deny manipulation and functions on kernel modules. Also gated by CAP_SYS_MODULE.
ioperm Prevent containers from modifying kernel I/O privilege levels. Already gated by CAP_SYS_RAWIO.
iopl Prevent containers from modifying kernel I/O privilege levels. Already gated by CAP_SYS_RAWIO.
kcmp Restrict process inspection capabilities, already blocked by dropping CAP_PTRACE.
kexec_file_load Sister syscall of kexec_load that does the same thing, slightly different arguments.
kexec_load Deny loading a new kernel for later execution.
keyctl Prevent containers from using the kernel keyring, which is not namespaced.
lookup_dcookie Tracing/profiling syscall, which could leak a lot of information on the host.
mbind Syscall that modifies kernel memory and NUMA settings. Already gated by CAP_SYS_NICE.
modify_ldt Old syscall only used in 16-bit code and a potential information leak.
mount Deny mounting, already gated by CAP_SYS_ADMIN.
move_pages Syscall that modifies kernel memory and NUMA settings.
name_to_handle_at Sister syscall to open_by_handle_at. Already gated by CAP_SYS_NICE.
nfsservctl Deny interaction with the kernel nfs daemon.
open_by_handle_at Cause of an old container breakout. Also gated by CAP_DAC_READ_SEARCH.
perf_event_open Tracing/profiling syscall, which could leak a lot of information on the host.
personality Prevent container from enabling BSD emulation. Not inherently dangerous, but poorly tested, potential for a lot of kernel vulns.
pivot_root Deny pivot_root, should be privileged operation.
process_vm_readv Restrict process inspection capabilities, already blocked by dropping CAP_PTRACE.
process_vm_writev Restrict process inspection capabilities, already blocked by dropping CAP_PTRACE.
ptrace Tracing/profiling syscall, which could leak a lot of information on the host. Already blocked by dropping CAP_PTRACE.
query_module Deny manipulation and functions on kernel modules.
quotactl Quota syscall which could let containers disable their own resource limits or process accounting. Also gated by CAP_SYS_ADMIN.
reboot Don't let containers reboot the host. Also gated by CAP_SYS_BOOT.
restart_syscall Don't allow containers to restart a syscall. Possible seccomp bypass see: https://code.google.com/p/chromium/issues/detail?id=408827.
request_key Prevent containers from using the kernel keyring, which is not namespaced.
set_mempolicy Syscall that modifies kernel memory and NUMA settings. Already gated by CAP_SYS_NICE.
setns Deny associating a thread with a namespace. Also gated by CAP_SYS_ADMIN.
settimeofday Time/date is not namespaced. Also gated by CAP_SYS_TIME.
stime Time/date is not namespaced. Also gated by CAP_SYS_TIME.
swapon Deny start/stop swapping to file/device. Also gated by CAP_SYS_ADMIN.
swapoff Deny start/stop swapping to file/device. Also gated by CAP_SYS_ADMIN.
sysfs Obsolete syscall.
_sysctl Obsolete, replaced by /proc/sys.
umount Should be a privileged operation. Also gated by CAP_SYS_ADMIN.
umount2 Should be a privileged operation.
unshare Deny cloning new namespaces for processes. Also gated by CAP_SYS_ADMIN, with the exception of unshare --user.
uselib Older syscall related to shared libraries, unused for a long time.
ustat Obsolete syscall.
vm86 In kernel x86 real mode virtual machine. Also gated by CAP_SYS_ADMIN.
vm86old In kernel x86 real mode virtual machine. Also gated by CAP_SYS_ADMIN.