As soon as the initial executable in the container is executed as a non root user,
permitted and effective capabilities are dropped. Drop them earlier than this, so
that they are dropped before executing the file. The main effect of this is that
if `CAP_DAC_OVERRIDE` is set (the default) the user will not be able to execute
files they do not have permission to execute, which previously they could.
The old behaviour was somewhat surprising and the new one is definitely correct,
but it is not in any meaningful way exploitable, and I do not think it is
necessary to backport this fix. It is unlikely to have any negative effects as
almost all executables have world execute permission anyway.
Use the bounding set not the effective set as the canonical set of capabilities, as
effective will now vary.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
The quotactl syscall is being whitelisted in default seccomp profile,
gated by CAP_SYS_ADMIN.
Signed-off-by: Panagiotis Moustafellos <pmoust@elastic.co>
Changes most references of syscall to golang.org/x/sys/
Ones aren't changes include, Errno, Signal and SysProcAttr
as they haven't been implemented in /x/sys/.
Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>
[s390x] switch utsname from unsigned to signed
per 33267e036f
char in s390x in the /x/sys/unix package is now signed, so
change the buildtags
Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>
This reverts commit 7e3a596a63.
Unfortunately, it was pointed out in https://github.com/moby/moby/pull/29076#commitcomment-21831387
that the `socketcall` syscall takes a pointer to a struct so it is not possible to
use seccomp profiles to filter it. This means these cannot be blocked as you can
use `socketcall` to call them regardless, as we currently allow 32 bit syscalls.
Users who wish to block these should use a seccomp profile that blocks all
32 bit syscalls and then just block the non socketcall versions.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
From personality(2):
Have uname(2) report a 2.6.40+ version number rather than a 3.x version
number. Added as a stopgap measure to support broken applications that
could not handle the kernel version-numbering switch from 2.6.x to 3.x.
This allows both "UNAME26|PER_LINUX" and "UNAME26|PER_LINUX32".
Fixes: #32839
Signed-off-by: Ian Campbell <ian.campbell@docker.com>
Previously building with seccomp disabled would cause build failures
because of a mismatch in the type signatures of DefaultProfile().
Signed-off-by: Aleksa Sarai <asarai@suse.de>
These are arm variants with different argument ordering because of
register alignment requirements.
fix#30516
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
Linux supports many obsolete address families, which are usually available in
common distro kernels, but they are less likely to be properly audited and
may have security issues
This blocks all socket families in the socket (and socketcall where applicable) syscall
except
- AF_UNIX - Unix domain sockets
- AF_INET - IPv4
- AF_INET6 - IPv6
- AF_NETLINK - Netlink sockets for communicating with the ekrnel
- AF_PACKET - raw sockets, which are only allowed with CAP_NET_RAW
All other socket families are blocked, including Appletalk (native, not
over IP), IPX (remember that!), VSOCK and HVSOCK, which should not generally
be used in containers, etc.
Note that users can of course provide a profile per container or in the daemon
config if they have unusual use cases that require these.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
Only open_by_handle_at requires CAP_DAC_READ_SEARCH.
This allows systemd to run with only `--cap-add SYS_ADMIN`
rather than having to also add `--cap-add DAC_READ_SEARCH`
as well which it does not really need.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
Do not gate with CAP_IPC_LOCK as unprivileged use is now
allowed in Linux. This returns it to how it was in 1.11.
Fixes#23587
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
To implement seccomp for s390x the following changes are required:
1) seccomp_default: Add s390 compat mode
On s390x (64 bit) we can run s390 (32 bit) programs in 32 bit
compat mode. Therefore add this information to arches().
2) seccomp_default: Use correct flags parameter for sys_clone on s390x
On s390x the second parameter for the clone system call is the flags
parameter. On all other architectures it is the first one.
See kernel code kernel/fork.c:
#elif defined(CONFIG_CLONE_BACKWARDS2)
SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
int __user *, parent_tidptr,
So fix the docker default seccomp rule and check for the second
parameter on s390/s390x.
3) seccomp_default: Add s390 specific syscalls
For s390 we currently have three additional system calls that should
be added to the seccomp whitelist:
- Other architectures can read/write unprivileged from/to PCI MMIO memory.
On s390 the instructions are privileged and therefore we need system
calls for that purpose:
* s390_pci_mmio_write()
* s390_pci_mmio_read()
- Runtime instrumentation:
* s390_runtime_instr()
4) test_integration: Do not run seccomp default profile test on s390x
The generated profile that we check in is for amd64 and i386
architectures and does not work correctly on s390x.
See also: 75385dc216 ("Do not run the seccomp tests that use
default.json on non x86 architectures")
5) Dockerfile.s390x: Add "seccomp" to DOCKER_BUILDTAGS
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
In #22554 I aligned seccomp and capabilities, however the case of
the chown calls and CAP_CHOWN was less clearcut, as these are
simple calls that the capabilities will block if they are not
allowed. They are needed when no new privileges is not set in
order to allow docker to call chown before the container is
started, so there was a workaround but this did not include
all the chown syscalls, and Arm was failing on some seccomp
tests because it was using a different syscall from just the
fchown that was allowed in this case. It is simpler to just
allow all the chown calls in the default seccomp profile and
let the capabilities subsystem block them.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
In order to do this, allow the socketcall syscall in the default
seccomp profile. This is a multiplexing syscall for the socket
operations, which is becoming obsolete gradually, but it is used
in some architectures. libseccomp has special handling for it for
x86 where it is common, so we did not need it in the profile,
but does not have any handling for ppc64le. It turns out that the
Debian images we use for tests do use the socketcall, while the
newer images such as Ubuntu 16.04 do not. Enabling this does no
harm as we allow all the socket operations anyway, and we allow
the similar ipc call for similar reasons already.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
Currently the default seccomp profile is fixed. This changes it
so that it varies depending on the Linux capabilities selected with
the --cap-add and --cap-drop options. Without this, if a user adds
privileges, eg to allow ptrace with --cap-add sys_ptrace then still
cannot actually use ptrace as it is still blocked by seccomp, so
they will probably disable seccomp or use --privileged. With this
change the syscalls that are needed for the capability are also
allowed by the seccomp profile based on the selected capabilities.
While this patch makes it easier to do things with for example
cap_sys_admin enabled, as it will now allow creating new namespaces
and use of mount, it still allows less than --cap-add cap_sys_admin
--security-opt seccomp:unconfined would have previously. It is not
recommended that users run containers with cap_sys_admin as this does
give full access to the host machine.
It also cleans up some architecture specific system calls to be
only selected when needed.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
These syscalls are already blocked by the default capabilities:
mlock mlock2 mlockall require CAP_IPC_LOCK
vhangup requires CAP_SYS_TTY_CONFIG
There is therefore no reason to allow them in the default profile
as they cannot be used anyway.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
This adds the following new syscalls that are supported in libseccomp 2.3.0,
including calls added up to kernel 4.5-rc4:
mlock2 - same as mlock but with a flag
copy_file_range - copy file contents, like splice but with reflink support.
The following are not added, and mentioned in docs:
userfaultfd - userspace page fault handling, mainly designed for process migration
The following are not added, only apply to less common architectures:
switch_endian
membarrier
breakpoint
set_tls
I plan to review the other architectures, some of which can now have seccomp
enabled in the build as they are now supported.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
Fixes#20818
This syscall was blocked as there was some concern that it could be
used to bypass filtering of other syscall arguments. However none of the
potential syscalls where this could be an issue (poll, nanosleep,
clock_nanosleep, futex) are blocked in the default profile anyway.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
On 32 bit x86 this is a multiplexing syscall for the system V
ipc syscalls such as shmget, and so needs to be allowed for
shared memory access for 32 bit binaries.
Fixes#20733
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
We generally want to filter the personality(2) syscall, as it
allows disabling ASLR, and turning on some poorly supported
emulations that have been the target of CVEs. However the use
cases for reading the current value, setting the default
PER_LINUX personality, and setting PER_LINUX32 for 32 bit
emulation are fine.
See issue #20634
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
