Let's use chase_symlinks() everywhere, and stop using GNU
canonicalize_file_name() everywhere. For most cases this should not change
behaviour, however increase exposure of our function to get better tested. Most
importantly in a few cases (most notably nspawn) it can take the correct root
directory into account when chasing symlinks.
Given that other file systems (notably: xfs) support reflinks these days, let's
extend the file system snapshotting logic to fall back to plan copies or
reflinks when full btrfs subvolume snapshots are not available.
This essentially makes "systemd-nspawn --ephemeral" and "systemd-nspawn
--template=" available on non-btrfs subvolumes. Of course, both operations will
still be slower on non-btrfs than on btrfs (simply because reflinking each file
individually in a directory tree is still slower than doing this in one step
for a whole subvolume), but it's probably good enough for many cases, and we
should provide the users with the tools, they have to figure out what's good
for them.
Note that "machinectl clone" already had a fallback like this in place, this
patch generalizes this, and adds similar support to our other cases.
@filesystem groups various file system operations, such as opening files and
directories for read/write and stat()ing them, plus renaming, deleting,
symlinking, hardlinking.
In contrast to all other unit types device units when queued just track
external state, they cannot effect state changes on their own. Hence unless a
client or other job waits for them there's no reason to keep them in the job
queue. This adds a concept of GC'ing jobs of this type as soon as no client or
other job waits for them anymore.
To ensure this works correctly we need to track which clients actually
reference a job (i.e. which ones enqueued it). Unfortunately that's pretty
nasty to do for direct connections, as sd_bus_track doesn't work for
them. For now, work around this, by simply remembering in a boolean that a job
was requested by a direct connection, and reset it when we notice the direct
connection is gone. This means the GC logic works fine, except that jobs are
not immediately removed when direct connections disconnect.
In the longer term, a rework of the bus logic should fix this properly. For now
this should be good enough, as GC works for fine all cases except this one, and
thus is a clear improvement over the previous behaviour.
Fixes: #1921
core: add new RestrictNamespaces= unit file setting
Merging, not rebasing, because this touches many files and there were tree-wide cleanups in the mean time.
We don't have plural in the name of any other -util files and this
inconsistency trips me up every time I try to type this file name
from memory. "formats-util" is even hard to pronounce.
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.
Fixes:
$ ./libtool --mode execute valgrind --leak-check=full ./journalctl >/dev/null
==22309== Memcheck, a memory error detector
==22309== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==22309== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==22309== Command: /home/vagrant/systemd/.libs/lt-journalctl
==22309==
Hint: You are currently not seeing messages from other users and the system.
Users in groups 'adm', 'systemd-journal', 'wheel' can see all messages.
Pass -q to turn off this notice.
==22309==
==22309== HEAP SUMMARY:
==22309== in use at exit: 8,680 bytes in 4 blocks
==22309== total heap usage: 5,543 allocs, 5,539 frees, 9,045,618 bytes allocated
==22309==
==22309== 488 (56 direct, 432 indirect) bytes in 1 blocks are definitely lost in loss record 2 of 4
==22309== at 0x4C2BBAD: malloc (vg_replace_malloc.c:299)
==22309== by 0x6F37A0A: __new_var_obj_p (__libobj.c:36)
==22309== by 0x6F362F7: __acl_init_obj (acl_init.c:28)
==22309== by 0x6F37731: __acl_from_xattr (__acl_from_xattr.c:54)
==22309== by 0x6F36087: acl_get_file (acl_get_file.c:69)
==22309== by 0x4F15752: acl_search_groups (acl-util.c:172)
==22309== by 0x113A1E: access_check_var_log_journal (journalctl.c:1836)
==22309== by 0x113D8D: access_check (journalctl.c:1889)
==22309== by 0x115681: main (journalctl.c:2236)
==22309==
==22309== LEAK SUMMARY:
==22309== definitely lost: 56 bytes in 1 blocks
==22309== indirectly lost: 432 bytes in 1 blocks
==22309== possibly lost: 0 bytes in 0 blocks
==22309== still reachable: 8,192 bytes in 2 blocks
==22309== suppressed: 0 bytes in 0 blocks
If we encounter the (unlikely) situation where the combined path to the
new root and a path to a mount to be moved together exceed maximum path length,
we shouldn't crash, but fail this path instead.
@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
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.
Rewrite the function to be slightly simpler. In particular, if a specific
match is found (like ConditionVirtualization=yes), simply return an answer
immediately, instead of relying that "yes" will not be matched by any of
the virtualization names below.
No functional change.
"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.
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.
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
This is a follow-up for fb8b0869a7, and makes a
couple of minor clean-up changes:
- The field name in the timestamp file is changed from "TimestampNSec=" to
"TIMESTAMP_NSEC=". This is done simply to reflect the fact that we parse the
file with the env var file parser, and hence the contents should better
follow the usual capitalization of env vars, i.e. be all uppercase.
- Needless negation of the errno parameter log_error_errno() and friends has
been removed.
- Instead of manually calculating the nsec remainder of the timestamp, use
timespec_store().
- We now check whether we were able to write the timestamp file in full with
fflush_and_check() the way we usually do it.
It may be desired by users to know what targets a particular service is
installed into. Improve user friendliness by teaching the is-enabled
command to show such information when used with --full.
This patch makes use of the newly added UnitFileFlags and adds
UNIT_FILE_DRY_RUN flag into it. Since the API had already been modified,
it's now easy to add the new dry-run feature for other commands as
well. As a next step, --dry-run could be added to systemctl, which in
turn might pave the way for a long requested dry-run feature when
running systemctl start.
We should substitute DefaultInstance if the instance is not specified.
Test case:
[Install]
DefaultInstance=bond1
WantedBy= foobar-n-%n.device
WantedBy= foobar-N-%N.device
$ systemctl --root=/ enable testing4@.service
Created symlink /etc/systemd/system/foobar-n-testing4@bond1.service.device.wants/testing4@bond1.service → /etc/systemd/system/testing4@.service.
Created symlink /etc/systemd/system/foobar-N-testing4@bond1.device.wants/testing4@bond1.service → /etc/systemd/system/testing4@.service.
(before, the symlink would be created with empty %n, %N parts).
