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Let's tighten our sandbox a bit more: with this change ProtectSystem= gains a
new setting "strict". If set, the entire directory tree of the system is
mounted read-only, but the API file systems /proc, /dev, /sys are excluded
(they may be managed with PrivateDevices= and ProtectKernelTunables=). Also,
/home and /root are excluded as those are left for ProtectHome= to manage.
In this mode, all "real" file systems (i.e. non-API file systems) are mounted
read-only, and specific directories may only be excluded via
ReadWriteDirectories=, thus implementing an effective whitelist instead of
blacklist of writable directories.
While we are at, also add /efi to the list of paths always affected by
ProtectSystem=. This is a follow-up for
b52a109ad38cd37b660ccd5394ff5c171a5e5355 which added /efi as alternative for
/boot. Our namespacing logic should respect that too.
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ProtectControlGroups=
If enabled, these will block write access to /sys, /proc/sys and
/proc/sys/fs/cgroup.
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This adds the boolean RemoveIPC= setting to service, socket, mount and swap
units (i.e. all unit types that may invoke processes). if turned on, and the
unit's user/group is not root, all IPC objects of the user/group are removed
when the service is shut down. The life-cycle of the IPC objects is hence bound
to the unit life-cycle.
This is particularly relevant for units with dynamic users, as it is essential
that no objects owned by the dynamic users survive the service exiting. In
fact, this patch adds code to imply RemoveIPC= if DynamicUser= is set.
In order to communicate the UID/GID of an executed process back to PID 1 this
adds a new "user lookup" socket pair, that is inherited into the forked
processes, and closed before the exec(). This is needed since we cannot do NSS
from PID 1 due to deadlock risks, However need to know the used UID/GID in
order to clean up IPC owned by it if the unit shuts down.
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Fix man links
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ExecStop=/ExecStopPost= commands
This should simplify monitoring tools for services, by passing the most basic
information about service result/exit information via environment variables,
thus making it unnecessary to retrieve them explicitly via the bus.
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This setting adds minimal user namespacing support to a service. When set the invoked
processes will run in their own user namespace. Only a trivial mapping will be
set up: the root user/group is mapped to root, and the user/group of the
service will be mapped to itself, everything else is mapped to nobody.
If this setting is used the service runs with no capabilities on the host, but
configurable capabilities within the service.
This setting is particularly useful in conjunction with RootDirectory= as the
need to synchronize /etc/passwd and /etc/group between the host and the service
OS tree is reduced, as only three UID/GIDs need to match: root, nobody and the
user of the service itself. But even outside the RootDirectory= case this
setting is useful to substantially reduce the attack surface of a service.
Example command to test this:
systemd-run -p PrivateUsers=1 -p User=foobar -t /bin/sh
This runs a shell as user "foobar". When typing "ps" only processes owned by
"root", by "foobar", and by "nobody" should be visible.
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As suggested by @mbiebl we already use the "!" special char in unit file
assignments for negation, hence we should not use it in a different context for
privileged execution. Let's use "+" instead.
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service is running
This adds a new boolean setting DynamicUser= to service files. If set, a new
user will be allocated dynamically when the unit is started, and released when
it is stopped. The user ID is allocated from the range 61184..65519. The user
will not be added to /etc/passwd (but an NSS module to be added later should
make it show up in getent passwd).
For now, care should be taken that the service writes no files to disk, since
this might result in files owned by UIDs that might get assigned dynamically to
a different service later on. Later patches will tighten sandboxing in order to
ensure that this cannot happen, except for a few selected directories.
A simple way to test this is:
systemd-run -p DynamicUser=1 /bin/sleep 99999
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This patch renames Read{Write,Only}Directories= and InaccessibleDirectories=
to Read{Write,Only}Paths= and InaccessiblePaths=, previous names are kept
as aliases but they are not advertised in the documentation.
Renamed variables:
`read_write_dirs` --> `read_write_paths`
`read_only_dirs` --> `read_only_paths`
`inaccessible_dirs` --> `inaccessible_paths`
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Despite the name, `Read{Write,Only}Directories=` already allows for
regular file paths to be masked. This commit adds the same behavior
to `InaccessibleDirectories=` and makes it explicit in the doc.
This patch introduces `/run/systemd/inaccessible/{reg,dir,chr,blk,fifo,sock}`
{dile,device}nodes and mounts on the appropriate one the paths specified
in `InacessibleDirectories=`.
Based on Luca's patch from https://github.com/systemd/systemd/pull/3327
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It takes a boolean value. If true, access to SCHED_RR, SCHED_FIFO and
SCHED_DEADLINE is blocked, which my be used to lock up the system.
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executed services
This permits services to detect whether their stdout/stderr is connected to the
journal, and if so talk to the journal directly, thus permitting carrying of
metadata.
As requested by the gtk folks: #2473
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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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This patch implements the new magic character '!'. By putting '!' in front
of a command, systemd executes it with full privileges ignoring paramters
such as User, Group, SupplementaryGroups, CapabilityBoundingSet,
AmbientCapabilities, SecureBits, SystemCallFilter, SELinuxContext,
AppArmorProfile, SmackProcessLabel, and RestrictAddressFamilies.
Fixes partially https://github.com/systemd/systemd/issues/3414
Related to https://github.com/coreos/rkt/issues/2482
Testing:
1. Create a user 'bob'
2. Create the unit file /etc/systemd/system/exec-perm.service
(You can use the example below)
3. sudo systemctl start ext-perm.service
4. Verify that the commands starting with '!' were not executed as bob,
4.1 Looking to the output of ls -l /tmp/exec-perm
4.2 Each file contains the result of the id command.
`````````````````````````````````````````````````````````````````
[Unit]
Description=ext-perm
[Service]
Type=oneshot
TimeoutStartSec=0
User=bob
ExecStartPre=!/usr/bin/sh -c "/usr/bin/rm /tmp/exec-perm*" ;
/usr/bin/sh -c "/usr/bin/id > /tmp/exec-perm-start-pre"
ExecStart=/usr/bin/sh -c "/usr/bin/id > /tmp/exec-perm-start" ;
!/usr/bin/sh -c "/usr/bin/id > /tmp/exec-perm-star-2"
ExecStartPost=/usr/bin/sh -c "/usr/bin/id > /tmp/exec-perm-start-post"
ExecReload=/usr/bin/sh -c "/usr/bin/id > /tmp/exec-perm-reload"
ExecStop=!/usr/bin/sh -c "/usr/bin/id > /tmp/exec-perm-stop"
ExecStopPost=/usr/bin/sh -c "/usr/bin/id > /tmp/exec-perm-stop-post"
[Install]
WantedBy=multi-user.target]
`````````````````````````````````````````````````````````````````
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New exec boolean MemoryDenyWriteExecute, when set, installs
a seccomp filter to reject mmap(2) with PAGE_WRITE|PAGE_EXEC
and mprotect(2) with PAGE_EXEC.
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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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Definitions of ReadWriteDirectories=, ReadOnlyDirectories=, InaccessibleDirectories=,
WorkingDirectory=, and RootDirecory= were not clear. This patch specifies when
they are relative to the host's root directory and when they are relative to the service's
root directory.
Fixes #3248
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Private /dev will not be managed by udev or others, so we can make it
noexec and readonly after we have made all device nodes. As /dev/shm
needs to be writable, we can't use bind_remount_recursive().
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As suggested in:
https://github.com/systemd/systemd/pull/3124#discussion_r61068789
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Fixes: #1603
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The manpage of seccomp specify that using seccomp with
SECCOMP_SET_MODE_FILTER will return EACCES if the caller do not have
CAP_SYS_ADMIN set, or if the no_new_privileges bit is not set. Hence,
without NoNewPrivilege set, it is impossible to use a SystemCall*
directive with a User directive set in system mode.
Now, NoNewPrivileges is set if we are in user mode, or if we are in
system mode and we don't have CAP_SYS_ADMIN, and SystemCall*
directives are used.
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Among other fixes, add information about more architectures that are supported
these days.
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The setting is hardly useful (since its effect is generally reduced to zero due
to file system caps), and with the advent of ambient caps an actually useful
replacement exists, hence let's get rid of this.
I am pretty sure this was unused and our man page already recommended against
its use, hence this should be a safe thing to remove.
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The new parser supports:
<value> - specify both limits to the same value
<soft:hard> - specify both limits
the size or time specific suffixes are supported, for example
LimitRTTIME=1sec
LimitAS=4G:16G
The patch introduces parse_rlimit_range() and rlim type (size, sec,
usec, etc.) specific parsers. No code is duplicated now.
The patch also sync docs for DefaultLimitXXX= and LimitXXX=.
References: https://github.com/systemd/systemd/issues/1769
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Dependency engine improvements
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For all units ensure there's an "Automatic Dependencies" section in the
man page, and explain which dependencies are automatically added in all
cases, and which ones are added on top if DefaultDependencies=yes is
set.
This is also done for systemd.exec(5), systemd.resource-control(5) and
systemd.unit(5) as these pages describe common behaviour of various unit
types.
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This directive allows passing environment variables from the system
manager to spawned services. Variables in the system manager can be set
inside a container by passing `--set-env=...` options to systemd-spawn.
Tested with an on-disk test.service unit. Tested using multiple variable
names on a single line, with an empty setting to clear the current list
of variables, with non-existing variables.
Tested using `systemd-run -p PassEnvironment=VARNAME` to confirm it
works with transient units.
Confirmed that `systemctl show` will display the PassEnvironment
settings.
Checked that man pages are generated correctly.
No regressions in `make check`.
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Let's make sure "LimitCPU=30min" can be parsed properly, following the
usual logic how we parse time values. Similar for LimitRTTIME=.
While we are at it, extend a bit on the man page section about resource
limits.
Fixes: #1772
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doc: typo and ortho fixes
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Let's make things more user-friendly and support for example
LimitAS=16G
rather than force users to always use LimitAS=16106127360.
The change is relevant for options:
[Default]Limit{FSIZE,DATA,STACK,CORE,RSS,AS,MEMLOCK,MSGQUEUE}
The patch introduces config_parse_bytes_limit(), it's the same as
config_parse_limit() but uses parse_size() tu support the suffixes.
Addresses: https://github.com/systemd/systemd/issues/1772
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Document support for commas as a separator and possibility of specifying
ranges of CPU indices.
Tested by regenerating the manpages locally and reading them on man.
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If set to ~ the working directory is set to the home directory of the
user configured in User=.
This change also exposes the existing switch for the working directory
that allowed making missing working directories non-fatal.
This also changes "machinectl shell" to make use of this to ensure that
the invoked shell is by default in the user's home directory.
Fixes #1268.
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When generating utmp/wtmp entries, optionally add both LOGIN_PROCESS and
INIT_PROCESS entries or even all three of LOGIN_PROCESS, INIT_PROCESS
and USER_PROCESS entries, instead of just a single INIT_PROCESS entry.
With this change systemd may be used to not only invoke a getty directly
in a SysV-compliant way but alternatively also a login(1) implementation
or even forego getty and login entirely, and invoke arbitrary shells in
a way that they appear in who(1) or w(1).
This is preparation for a later commit that adds a "machinectl shell"
operation to invoke a shell in a container, in a way that is compatible
with who(1) and w(1).
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If a line doesn't contain an = separator, it is skipped, rather than
raising an error.
This is potentially useful, so let's document this behaviour.
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This did not really work out as we had hoped. Trying to do this upstream
introduced several problems that probably makes it better suited as a
downstream patch after all. At any rate, it is not releaseable in the
current state, so we at least need to revert this before the release.
* by adjusting the path to binaries, but not do the same thing to the
search path we end up with inconsistent man-pages. Adjusting the search
path too would be quite messy, and it is not at all obvious that this is
worth the effort, but at any rate it would have to be done before we
could ship this.
* this means that distributed man-pages does not make sense as they depend
on config options, and for better or worse we are still distributing
man pages, so that is something that definitely needs sorting out before
we could ship with this patch.
* we have long held that split-usr is only minimally supported in order
to boot, and something we hope will eventually go away. So before we start
adding even more magic/effort in order to make this work nicely, we should
probably question if it makes sense at all.
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