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This was tested on ppc64le. Assume the same is true for ppc64.
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the one we are compiled for (#5272)
It's a difference. Not a big one, but let's be correct here.
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this way, we can still call seccomp ourselves, even if seccomp() is
blocked by the filter we are installing.
Fixes: #5300
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We added mmap() and mmap2(), but forgot munmap(). Fix that.
Pointed out by @lucaswerkmeister:
https://github.com/systemd/systemd/pull/4537#issuecomment-273275298
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Add a bit of code that tries to get the right parameter order in place
for some of the better known architectures, and skips
restrict_namespaces for other archs.
This also bypasses the test on archs where we don't know the right
order.
In this case I didn't bother with testing the case where no filter is
applied, since that is hopefully just an issue for now, as there's
nothing stopping us from supporting more archs, we just need to know
which order is right.
Fixes: #5241
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On i386 we block the old mmap() call entirely, since we cannot properly
filter it. Thankfully it hasn't been used by glibc since quite some
time.
Fixes: #5240
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it a NOP
See: #5215
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(#5230)
https://github.com/systemd/systemd/issues/5215#issuecomment-277156262
libseccomp does not allow you to add architectures to a filter that
doesn't match the byte ordering of the architectures already added to
the filter (it would be a mess, not to mention largely pointless) and
since systemd attempts to add an ABI before removing the default native
ABI, you will always fail on Power (either due to ppc or ppc64le). The
fix is to remove the native ABI before adding a new ABI so you don't run
into problems with byte ordering.
You would likely see the same failure on a MIPS system.
Thanks @pcmoore!
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This substantially reworks the seccomp code, to ensure better
compatibility with some architectures, including i386.
So far we relied on libseccomp's internal handling of the multiple
syscall ABIs supported on Linux. This is problematic however, as it does
not define clear semantics if an ABI is not able to support specific
seccomp rules we install.
This rework hence changes a couple of things:
- We no longer use seccomp_rule_add(), but only
seccomp_rule_add_exact(), and fail the installation of a filter if the
architecture doesn't support it.
- We no longer rely on adding multiple syscall architectures to a single filter,
but instead install a separate filter for each syscall architecture
supported. This way, we can install a strict filter for x86-64, while
permitting a less strict filter for i386.
- All high-level filter additions are now moved from execute.c to
seccomp-util.c, so that we can test them independently of the service
execution logic.
- Tests have been added for all types of our seccomp filters.
- SystemCallFilters= and SystemCallArchitectures= are now implemented in
independent filters and installation logic, as they semantically are
very much independent of each other.
Fixes: #4575
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The system call is obsolete after all.
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These groupe reboot()/kexec() and swapon()/swapoff() respectively
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@filesystem groups various file system operations, such as opening files and
directories for read/write and stat()ing them, plus renaming, deleting,
symlinking, hardlinking.
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This new setting permits restricting whether namespaces may be created and
managed by processes started by a unit. It installs a seccomp filter blocking
certain invocations of unshare(), clone() and setns().
RestrictNamespaces=no is the default, and does not restrict namespaces in any
way. RestrictNamespaces=yes takes away the ability to create or manage any kind
of namspace. "RestrictNamespaces=mnt ipc" restricts the creation of namespaces
so that only mount and IPC namespaces may be created/managed, but no other
kind of namespaces.
This setting should be improve security quite a bit as in particular user
namespacing was a major source of CVEs in the kernel in the past, and is
accessible to unprivileged processes. With this setting the entire attack
surface may be removed for system services that do not make use of namespaces.
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Just to make the whole thing easier for users.
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Now that the list is user-visible, @default should be first.
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@resources contains various syscalls that alter resource limits and memory and
scheduling parameters of processes. As such they are good candidates to block
for most services.
@basic-io contains a number of basic syscalls for I/O, similar to the list
seccomp v1 permitted but slightly more complete. It should be useful for
building basic whitelisting for minimal sandboxes
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These system calls clearly fall in the @ipc category, hence should be listed
there, simply to avoid confusion and surprise by the user.
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The system call is already part in @default hence implicitly allowed anyway.
Also, if it is actually blocked then systemd couldn't execute the service in
question anymore, since the application of seccomp is immediately followed by
it.
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Timing and sleep are so basic operations, it makes very little sense to ever
block them, hence don't.
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"Secondary arch" table for mips is entirely speculative…
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This allows us to unify most of the code in apply_protect_kernel_modules() and
apply_private_devices().
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"oldumount()" is not a syscall, but simply a wrapper for it, the actual syscall
nr is called "umount" (and the nr of umount() is called umount2 internally).
"sysctl()" is not a syscall, but "_syscall()" is. Fix this in the table.
Without these changes libseccomp cannot actually translate the tables in full.
This wasn't noticed before as the code was written defensively for this case.
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This adds a new seccomp_init_conservative() helper call that is mostly just a
wrapper around seccomp_init(), but turns off NNP and adds in all secondary
archs, for best compatibility with everything else.
Pretty much all of our code used the very same constructs for these three
steps, hence unifying this in one small function makes things a lot shorter.
This also changes incorrect usage of the "scmp_filter_ctx" type at various
places. libseccomp defines it as typedef to "void*", i.e. it is a pointer type
(pretty poor choice already!) that casts implicitly to and from all other
pointer types (even poorer choice: you defined a confusing type now, and don't
even gain any bit of type safety through it...). A lot of the code assumed the
type would refer to a structure, and hence aded additional "*" here and there.
Remove that.
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A variety of fixes:
- rename the SystemCallFilterSet structure to SyscallFilterSet. So far the main
instance of it (the syscall_filter_sets[] array) used to abbreviate
"SystemCall" as "Syscall". Let's stick to one of the two syntaxes, and not
mix and match too wildly. Let's pick the shorter name in this case, as it is
sufficiently well established to not confuse hackers reading this.
- Export explicit indexes into the syscall_filter_sets[] array via an enum.
This way, code that wants to make use of a specific filter set, can index it
directly via the enum, instead of having to search for it. This makes
apply_private_devices() in particular a lot simpler.
- Provide two new helper calls in seccomp-util.c: syscall_filter_set_find() to
find a set by its name, seccomp_add_syscall_filter_set() to add a set to a
seccomp object.
- Update SystemCallFilter= parser to use extract_first_word(). Let's work on
deprecating FOREACH_WORD_QUOTED().
- Simplify apply_private_devices() using this functionality
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Add seccomp support for the s390 architecture (31-bit and 64-bit)
to systemd.
This requires libseccomp >= 2.3.1.
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In https://github.com/systemd/systemd/pull/4004 , a runtime detection
method for seccomp was added. However, it does not detect the case
where CONFIG_SECCOMP=y but CONFIG_SECCOMP_FILTER=n. This is possible
if the architecture does not support filtering yet.
Add a check for that case too.
While at it, change get_proc_field usage to use PR_GET_SECCOMP prctl,
as that should save a few system calls and (unnecessary) allocations.
Previously, reading of /proc/self/stat was done as recommended by
prctl(2) as safer. However, given that we need to do the prctl call
anyway, lets skip opening, reading and parsing the file.
Code for checking inspired by
https://outflux.net/teach-seccomp/autodetect.html
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permit bus clients to pin units to avoid automatic GC
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Fixes #3882
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A lot of basic code wants to know the stack size, and it is safe if they do,
hence let's permit getrlimit() (but not setrlimit()) by default.
See: #3970
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This adds three new seccomp syscall groups: @keyring for kernel keyring access,
@cpu-emulation for CPU emulation features, for exampe vm86() for dosemu and
suchlike, and @debug for ptrace() and related calls.
Also, the @clock group is updated with more syscalls that alter the system
clock. capset() is added to @privileged, and pciconfig_iobase() is added to
@raw-io.
Finally, @obsolete is a cleaned up. A number of syscalls that never existed on
Linux and have no number assigned on any architecture are removed, as they only
exist in the man pages and other operating sytems, but not in code at all.
create_module() is moved from @module to @obsolete, as it is an obsolete system
call. mem_getpolicy() is removed from the @obsolete list, as it is not
obsolete, but simply a NUMA API.
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Implement sets of system calls to help constructing system call
filters. A set starts with '@' to distinguish from a system call.
Closes: #3053, #3157
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This should be handled fine now by .dir-locals.el, so need to carry that
stuff in every file.
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The next step of a general cleanup of our includes. This one mostly
adds missing includes but there are a few removals as well.
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Sort the includes accoding to the new coding style.
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string-util.[ch]
There are more than enough calls doing string manipulations to deserve
its own files, hence do something about it.
This patch also sorts the #include blocks of all files that needed to be
updated, according to the sorting suggestions from CODING_STYLE. Since
pretty much every file needs our string manipulation functions this
effectively means that most files have sorted #include blocks now.
Also touches a few unrelated include files.
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And make use of it where appropriate for executing services and for
nspawn.
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architecture support for system calls
Also, turn system call filter bus properties into complex types instead
of concatenated strings.
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