This adds support for WaitKillableRecv seccomp flag
(also known as SCMP_FLTATR_CTL_WAITKILL in libseccomp and
as SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV in the kernel).
This requires:
- libseccomp >= 2.6.0
- libseccomp-golang >= 0.11.0
- linux kernel >= 5.19
Note that this flag does not make sense without NEW_LISTENER, and
the kernel returns EINVAL when SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV
is set but SECCOMP_FILTER_FLAG_NEW_LISTENER is not set.
For runc this means that .linux.seccomp.listenerPath should also be set,
and some of the seccomp rules should have SCMP_ACT_NOTIFY action. This
is why the flag is tested separately in seccomp-notify.bats.
At the moment the only adequate CI environment for this functionality is
Fedora 43. On all other platforms (including CentOS 10 and Ubuntu 24.04)
it is skipped similar to this:
> ok 251 runc run [seccomp] (SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) # skip requires libseccomp >= 2.6.0 and API level >= 7 (current version: 2.5.6, API level: 6)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
It is available since Go 1.21 and is defined during compile time
(i.e. based on GOARCH during build).
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
It turns out that on ppc64le (at least), Docker doesn't include any
architectures in the list of allowed architectures. libseccomp
interprets this as "just include the default architecture" but patchbpf
would return a no-op ENOSYS stub, which would lead to the exact issues
that commit 7a8d7162f9 ("seccomp: prepend -ENOSYS stub to all
filters") fixed for other architectures.
So, just always include the running architecture in the list. There's
no real downside.
Ref: https://bugzilla.suse.com/show_bug.cgi?id=1192051#c6
Reported-by: Fabian Vogt <fvogt@suse.com>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Calling the Linux AUDIT_* architecture constants "native" leads to
confusing code when we are getting the actual native architecture of the
running system.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
*os.File is correctly tracked by the garbage collector, and there's no
need to use raw file descriptors for this code.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Amend runc features to print seccomp flags. Two set of flags are added:
* known flags are those that this version of runc is aware of;
* supported flags are those that can be set; normally, this is the same
set as known flags, but due to older version of kernel and/or
libseccomp, some known flags might be unsupported.
This commit also consolidates three different switch statements dealing
with flags into one, in func setFlag. A note is added to this function
telling what else to look for when adding new flags.
Unfortunately, it also adds a list of known flags, that should be
kept in sync with the switch statement.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
In findLastSyscalls, we convert libseccomp.ArchNative to the real
libseccomp architecture, but archToNative already does that, so
this code is redundant.
Remove the redundant code, and move its comment to archToNative.
Fixes: 7a8d7162f
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Add a debug print of seccomp flags value, so the test can check
those (without using something like strace, that is).
Amend the flags setting test with the numeric values expected, and the
logic to check those.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Commit 58ea21daef added support for seccomp flags such as
SPEC_ALLOW, but it does not work as expected, because since commit
7a8d7162f9 we do not use libseccomp-golang's Load(), but
handle flags separately in patchbfp.
This fixes setting SPEC_ALLOW flag.
Add a comment to not forget to amend filterFlags when adding new flags.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Define sizeof(int) as a constant, and also return ENOSYS earlier in the
filter if it doesn't increase the number of instructions we generate
(this is a negligible performance improvement but it does make it easier
to understand the generated filter stub).
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
On s390x, syscalls above 255 are multiplexed using the (now otherwise
unused) setup(2) syscall (syscall number 0). If the kernel supports the
syscall then it will correctly translate the syscall number such that
seccomp will correctly detect it -- however, for unknown syscalls the
syscall number remains unchanged. This can be verified by running the
following program under strace:
int main(void)
{
scmp_filter_ctx ctx = seccomp_init(SCMP_ACT_TRAP);
seccomp_load(ctx);
return syscall(439, AT_FDCWD, "asdf", X_OK, 0);
}
Which will then die with the following signal (on pre-5.8 kernels):
--- SIGSYS {si_signo=SIGSYS, si_code=SYS_SECCOMP,
si_call_addr=0x3ffb3006c22, si_syscall=__NR_setup,
si_arch=AUDIT_ARCH_S390X} ---
(Note that the si_syscall is __NR_setup, not __NR_faccessat2.)
As a result, the -ENOSYS handling we had previously did not work
completely correctly on s390x because any syscall not supported by the
kernel would be treated as syscall number 0 rather than the actual
syscall number.
Always returning -ENOSYS will not cause any issues because in all of the
cases where this multiplexing occurs, seccomp will see the remapped
syscall number -- and no userspace program will call setup(2)
intentionally (the syscall has not existed in Linux for decades and was
originally a hack used early in Linux init prior to spawning pid1 -- so
you will get -ENOSYS from the kernel anyway).
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
This commit implements support for the SCMP_ACT_NOTIFY action. It
requires libseccomp-2.5.0 to work but runc still works with older
libseccomp if the seccomp policy does not use the SCMP_ACT_NOTIFY
action.
A new synchronization step between runc[INIT] and runc run is introduced
to pass the seccomp fd. runc run fetches the seccomp fd with pidfd_get
from the runc[INIT] process and sends it to the seccomp agent using
SCM_RIGHTS.
As suggested by @kolyshkin, we also make writeSync() a wrapper of
writeSyncWithFd() and wrap the error there. To avoid pointless errors,
we made some existing code paths just return the error instead of
re-wrapping it. If we don't do it, error will look like:
writing syncT <act>: writing syncT: <err>
By adjusting the code path, now they just look like this
writing syncT <act>: <err>
Signed-off-by: Alban Crequy <alban@kinvolk.io>
Signed-off-by: Rodrigo Campos <rodrigo@kinvolk.io>
Co-authored-by: Rodrigo Campos <rodrigo@kinvolk.io>
Go 1.17 introduce this new (and better) way to specify build tags.
For more info, see https://golang.org/design/draft-gobuild.
As a way to seamlessly switch from old to new build tags, gofmt (and
gopls) from go 1.17 adds the new tags along with the old ones.
Later, when go < 1.17 is no longer supported, the old build tags
can be removed.
Now, as I started to use latest gopls (v0.7.1), it adds these tags
while I edit. Rather than to randomly add new build tags, I guess
it is better to do it once for all files.
Mind that previous commits removed some tags that were useless,
so this one only touches packages that can at least be built
on non-linux.
Brought to you by
go1.17 fmt ./...
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
For files that end with _linux.go or _linux_test.go, there is no need to
specify linux build tag, as it is assumed from the file name.
In addition, rename libcontainer/notify_linux_v2.go -> libcontainer/notify_v2_linux.go
for the file name to make sense.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Do this for all errors except one from unix.*.
This fixes a bunch of errorlint warnings, like these
libcontainer/generic_error.go:25:15: type assertion on error will fail on wrapped errors. Use errors.As to check for specific errors (errorlint)
if le, ok := err.(Error); ok {
^
libcontainer/factory_linux_test.go:145:14: type assertion on error will fail on wrapped errors. Use errors.As to check for specific errors (errorlint)
lerr, ok := err.(Error)
^
libcontainer/state_linux_test.go:28:11: type assertion on error will fail on wrapped errors. Use errors.As to check for specific errors (errorlint)
_, ok := err.(*stateTransitionError)
^
libcontainer/seccomp/patchbpf/enosys_linux.go:88:4: switch on an error will fail on wrapped errors. Use errors.Is to check for specific errors (errorlint)
switch err {
^
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
gofumpt (mvdan.cc/gofumpt) is a fork of gofmt with stricter rules.
Brought to you by
git ls-files \*.go | grep -v ^vendor/ | xargs gofumpt -s -w
Looking at the diff, all these changes make sense.
Also, replace gofmt with gofumpt in golangci.yml.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
There is a potential deadlock where the ExportBPF method call writes to
a pipe but the pipe is not read until after the method call returns.
ExportBPF might fill the pipe buffer, in which case it will block
waiting for a read on the other side which can't happen until the method
returns.
Here we concurrently read from the pipe into a buffer to ensure
ExportBPF will always return.
Co-authored-by: Kieron Browne <kbrowne@vmware.com>
Co-authored-by: Danail Branekov <danailster@gmail.com>
Signed-off-by: Kieron Browne <kbrowne@vmware.com>
Signed-off-by: Danail Branekov <danailster@gmail.com>
The correct way to do that conversion according to
https://pkg.go.dev/syscall#Errno is:
```
err = nil
if errno != 0 {
err = errno
}
```
In this case the error check will always report a false positive in
unix.RawSyscall(unix.SYS_SECCOMP, ...), probably nobody has faced this
problem because the code takes the other path in most of the cases.
Fixes: 7a8d7162f9 ("seccomp: prepend -ENOSYS stub to all filters")
Signed-off-by: Mauricio Vásquez <mauricio@kinvolk.io>
Having -EPERM is the default was a fairly significant mistake from a
future-proofing standpoint in that it makes any new syscall return a
non-ignorable error (from glibc's point of view). We need to correct
this now because faccessat2(2) is something glibc critically needs to
have support for, but they're blocked on container runtimes because we
return -EPERM unconditionally (leading to confusion in glibc). This is
also a problem we're probably going to keep running into in the future.
Unfortunately there are several issues which stop us from having a clean
solution to this problem:
1. libseccomp has several limitations which require us to emulate
behaviour we want:
a. We cannot do logic based on syscall number, meaning we cannot
specify a "largest known syscall number";
b. libseccomp doesn't know in which kernel version a syscall was
added, and has no API for "minimum kernel version" so we cannot
simply ask libseccomp to generate sane -ENOSYS rules for us.
c. Additional seccomp rules for the same syscall are not treated as
distinct rules -- if rules overlap, seccomp will merge them. This
means we cannot add per-syscall -EPERM fallbacks;
d. There is no inverse operation for SCMP_CMP_MASKED_EQ;
e. libseccomp does not allow you to specify multiple rules for a
single argument, making it impossible to invert OR rules for
arguments.
2. The runtime-spec does not have any way of specifying:
a. The errno for the default action;
b. The minimum kernel version or "newest syscall at time of profile
creation"; nor
c. Which syscalls were intentionally excluded from the allow list
(weird syscalls that are no longer used were excluded entirely,
but Docker et al expect those syscalls to get EPERM not ENOSYS).
3. Certain syscalls should not return -ENOSYS (especially only for
certain argument combinations) because this could also trigger glibc
confusion. This means we have to return -EPERM for certain syscalls
but not as a global default.
4. There is not an obvious (and reasonable) upper limit to syscall
numbers, so we cannot create a set of rules for each syscall above
the largest syscall number in libseccomp. This means we must handle
inverse rules as described below.
5. Any syscall can be specified multiple times, which can make
generation of hotfix rules much harder.
As a result, we have to work around all of these things by coming up
with a heuristic to stop the bleeding. In the future we could hopefully
improve the situation in the runtime-spec and libseccomp.
The solution applied here is to prepend a "stub" filter which returns
-ENOSYS if the requested syscall has a larger syscall number than any
syscall mentioned in the filter. The reason for this specific rule is
that syscall numbers are (roughly) allocated sequentially and thus newer
syscalls will (usually) have a larger syscall number -- thus causing our
filters to produce -ENOSYS if the filter was written before the syscall
existed.
Sadly this is not a perfect solution because syscalls can be added
out-of-order and the syscall table can contain holes for several
releases. Unfortuntely we do not have a nicer solution at the moment
because there is no library which provides information about which Linux
version a syscall was introduced in. Until that exists, this workaround
will have to be good enough.
The above behaviour only happens if the default action is a blocking
action (in other words it is not SCMP_ACT_LOG or SCMP_ACT_ALLOW). If the
default action is permissive then we don't do any patching.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Kir Kolyshkin