This should result in no change when the error is printed, but make the
errors returned unwrappable, meaning errors.As and errors.Is will work.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
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>
Multiple conditions were previously allowed to be placed upon the
same syscall argument. Restore this behavior.
Signed-off-by: Matthew Heon <mheon@redhat.com>
Use unix.Prctl() instead of manually reimplementing it using
unix.RawSyscall. Also use unix.SECCOMP_MODE_FILTER instead of locally
defining it.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Since syscall is outdated and broken for some architectures,
use x/sys/unix instead.
There are still some dependencies on the syscall package that will
remain in syscall for the forseeable future:
Errno
Signal
SysProcAttr
Additionally:
- os still uses syscall, so it needs to be kept for anything
returning *os.ProcessState, such as process.Wait.
Signed-off-by: Christy Perez <christy@linux.vnet.ibm.com>
The `bufio.Scanner.Scan` method returns false either by reaching the
end of the input or an error. After Scan returns false, the Err method
will return any error that occurred during scanning, except that if it
was io.EOF, Err will return nil.
We should check the error when Scan return false(out of the for loop).
Signed-off-by: Wang Long <long.wanglong@huawei.com>
This commit allows additional architectures to be added to Seccomp filters
created by containers. This allows containers to make syscalls using these
architectures. For example, in a container on an AMD64 system, only AMD64
syscalls would be usable unless x86 was added to the filter using this patch,
which would allow both 32-bit and 64-bit syscalls to be used.
Signed-off-by: Matthew Heon <mheon@redhat.com>
This removes the existing, native Go seccomp filter generation and replaces it
with Libseccomp. Libseccomp is a C library which provides architecture
independent generation of Seccomp filters for the Linux kernel.
This adds a dependency on v2.2.1 or above of Libseccomp.
Signed-off-by: Matthew Heon <mheon@redhat.com>
Kir Kolyshkin