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@@ -71,8 +71,7 @@ containers with seccomp. It is moderately protective while
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providing wide application compatibility.
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providing wide application compatibility.
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-Overriding the default profile for a container
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-----------------------------------------------
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+### Overriding the default profile for a container
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You can pass `unconfined` to run a container without the default seccomp
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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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profile.
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@@ -81,3 +80,66 @@ profile.
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$ docker run --rm -it --security-opt seccomp:unconfined debian:jessie \
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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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unshare --map-root-user --user sh -c whoami
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```
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```
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+
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+### Syscalls blocked by the default profile
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+
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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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+
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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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Jessica Frazelle