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143 lines
10 KiB
Markdown
143 lines
10 KiB
Markdown
<!-- [metadata]>
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+++
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title = "Seccomp security profiles for Docker"
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description = "Enabling seccomp in Docker"
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keywords = ["seccomp, security, docker, documentation"]
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[menu.main]
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parent= "smn_secure_docker"
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weight=90
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+++
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<![end-metadata]-->
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# Seccomp security profiles for Docker
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Secure computing mode (Seccomp) is a Linux kernel feature. You can use it to
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restrict the actions available within the container. The `seccomp()` system
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call operates on the seccomp state of the calling process. You can use this
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feature to restrict your application's access.
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This feature is available only if Docker has been built with seccomp and the
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kernel is configured with `CONFIG_SECCOMP` enabled. To check if your kernel
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supports seccomp:
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```bash
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$ cat /boot/config-`uname -r` | grep CONFIG_SECCOMP=
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CONFIG_SECCOMP=y
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```
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> **Note**: seccomp profiles require seccomp 2.2.1 and are only
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> available starting with Debian 9 "Stretch", Ubuntu 15.10 "Wily", and
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> Fedora 22. To use this feature on Ubuntu 14.04, Debian Wheezy, or
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> Debian Jessie, you must download the [latest static Docker Linux binary](../installation/binaries.md).
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> This feature is currently *not* available on other distributions.
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## Passing a profile for a container
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The default seccomp profile provides a sane default for running containers with
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seccomp and disables around 44 system calls out of 300+. It is moderately protective while providing wide application
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compatibility. The default Docker profile (found [here](https://github.com/docker/docker/blob/master/profiles/seccomp/default.json) has a JSON layout in the following form:
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```json
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{
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"defaultAction": "SCMP_ACT_ERRNO",
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"architectures": [
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"SCMP_ARCH_X86_64",
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"SCMP_ARCH_X86",
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"SCMP_ARCH_X32"
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],
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"syscalls": [
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{
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"name": "accept",
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"action": "SCMP_ACT_ALLOW",
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"args": []
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},
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{
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"name": "accept4",
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"action": "SCMP_ACT_ALLOW",
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"args": []
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},
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...
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]
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}
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```
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When you run a container, it uses the default profile unless you override
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it with the `security-opt` option. For example, the following explicitly
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specifies the default policy:
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```
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$ docker run --rm -it --security-opt seccomp:/path/to/seccomp/profile.json hello-world
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```
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### Significant syscalls blocked by the default profile
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Docker's default seccomp profile is a whitelist which specifies the calls that
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are allowed. The table below lists the significant (but not all) syscalls that
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are effectively blocked because they are not on the whitelist. The table includes
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the reason each syscall is blocked rather than white-listed.
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| Syscall | Description |
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|---------------------|---------------------------------------------------------------------------------------------------------------------------------------|
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| `acct` | Accounting syscall which could let containers disable their own resource limits or process accounting. Also gated by `CAP_SYS_PACCT`. |
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| `add_key` | Prevent containers from using the kernel keyring, which is not namespaced. |
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| `adjtimex` | Similar to `clock_settime` and `settimeofday`, time/date is not namespaced. |
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| `bpf` | Deny loading potentially persistent bpf programs into kernel, already gated by `CAP_SYS_ADMIN`. |
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| `clock_adjtime` | Time/date is not namespaced. |
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| `clock_settime` | Time/date is not namespaced. |
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| `clone` | Deny cloning new namespaces. Also gated by `CAP_SYS_ADMIN` for CLONE_* flags, except `CLONE_USERNS`. |
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| `create_module` | Deny manipulation and functions on kernel modules. |
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| `delete_module` | Deny manipulation and functions on kernel modules. Also gated by `CAP_SYS_MODULE`. |
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| `finit_module` | Deny manipulation and functions on kernel modules. Also gated by `CAP_SYS_MODULE`. |
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| `get_kernel_syms` | Deny retrieval of exported kernel and module symbols. |
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| `get_mempolicy` | Syscall that modifies kernel memory and NUMA settings. Already gated by `CAP_SYS_NICE`. |
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| `init_module` | Deny manipulation and functions on kernel modules. Also gated by `CAP_SYS_MODULE`. |
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| `ioperm` | Prevent containers from modifying kernel I/O privilege levels. Already gated by `CAP_SYS_RAWIO`. |
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| `iopl` | Prevent containers from modifying kernel I/O privilege levels. Already gated by `CAP_SYS_RAWIO`. |
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| `kcmp` | Restrict process inspection capabilities, already blocked by dropping `CAP_PTRACE`. |
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| `kexec_file_load` | Sister syscall of `kexec_load` that does the same thing, slightly different arguments. |
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| `kexec_load` | Deny loading a new kernel for later execution. |
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| `keyctl` | Prevent containers from using the kernel keyring, which is not namespaced. |
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| `lookup_dcookie` | Tracing/profiling syscall, which could leak a lot of information on the host. |
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| `mbind` | Syscall that modifies kernel memory and NUMA settings. Already gated by `CAP_SYS_NICE`. |
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| `modify_ldt` | Old syscall only used in 16-bit code and a potential information leak. |
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| `mount` | Deny mounting, already gated by `CAP_SYS_ADMIN`. |
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| `move_pages` | Syscall that modifies kernel memory and NUMA settings. |
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| `name_to_handle_at` | Sister syscall to `open_by_handle_at`. Already gated by `CAP_SYS_NICE`. |
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| `nfsservctl` | Deny interaction with the kernel nfs daemon. |
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| `open_by_handle_at` | Cause of an old container breakout. Also gated by `CAP_DAC_READ_SEARCH`. |
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| `perf_event_open` | Tracing/profiling syscall, which could leak a lot of information on the host. |
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| `personality` | Prevent container from enabling BSD emulation. Not inherently dangerous, but poorly tested, potential for a lot of kernel vulns. |
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| `pivot_root` | Deny `pivot_root`, should be privileged operation. |
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| `process_vm_readv` | Restrict process inspection capabilities, already blocked by dropping `CAP_PTRACE`. |
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| `process_vm_writev` | Restrict process inspection capabilities, already blocked by dropping `CAP_PTRACE`. |
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| `ptrace` | Tracing/profiling syscall, which could leak a lot of information on the host. Already blocked by dropping `CAP_PTRACE`. |
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| `query_module` | Deny manipulation and functions on kernel modules. |
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| `quotactl` | Quota syscall which could let containers disable their own resource limits or process accounting. Also gated by `CAP_SYS_ADMIN`. |
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| `reboot` | Don't let containers reboot the host. Also gated by `CAP_SYS_BOOT`. |
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| `restart_syscall` | Don't allow containers to restart a syscall. Possible seccomp bypass see: https://code.google.com/p/chromium/issues/detail?id=408827. |
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| `request_key` | Prevent containers from using the kernel keyring, which is not namespaced. |
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| `set_mempolicy` | Syscall that modifies kernel memory and NUMA settings. Already gated by `CAP_SYS_NICE`. |
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| `setns` | Deny associating a thread with a namespace. Also gated by `CAP_SYS_ADMIN`. |
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| `settimeofday` | Time/date is not namespaced. Also gated by `CAP_SYS_TIME`. |
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| `stime` | Time/date is not namespaced. Also gated by `CAP_SYS_TIME`. |
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| `swapon` | Deny start/stop swapping to file/device. Also gated by `CAP_SYS_ADMIN`. |
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| `swapoff` | Deny start/stop swapping to file/device. Also gated by `CAP_SYS_ADMIN`. |
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| `sysfs` | Obsolete syscall. |
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| `_sysctl` | Obsolete, replaced by /proc/sys. |
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| `umount` | Should be a privileged operation. Also gated by `CAP_SYS_ADMIN`. |
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| `umount2` | Should be a privileged operation. |
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| `unshare` | Deny cloning new namespaces for processes. Also gated by `CAP_SYS_ADMIN`, with the exception of `unshare --user`. |
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| `uselib` | Older syscall related to shared libraries, unused for a long time. |
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| `ustat` | Obsolete syscall. |
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| `vm86` | In kernel x86 real mode virtual machine. Also gated by `CAP_SYS_ADMIN`. |
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| `vm86old` | In kernel x86 real mode virtual machine. Also gated by `CAP_SYS_ADMIN`. |
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## Run without the default seccomp profile
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You can pass `unconfined` to run a container without the default seccomp
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profile.
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```
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$ docker run --rm -it --security-opt seccomp:unconfined debian:jessie \
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unshare --map-root-user --user sh -c whoami
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```
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