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Lets go further and make /lib/modules/ inaccessible for services that do
not have business with modules, this is a minor improvment but it may
help on setups with custom modules and they are limited... in regard of
kernel auto-load feature.
This change introduce NameSpaceInfo struct which we may embed later
inside ExecContext but for now lets just reduce the argument number to
setup_namespace() and merge ProtectKernelModules feature.
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As with previous patch simplify ProtectHome and don't care about
duplicates, they will be sorted by most restrictive mode and cleaned.
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ProtectSystem= with all its different modes and other options like
PrivateDevices= + ProtectKernelTunables= + ProtectHome= are orthogonal,
however currently it's a bit hard to parse that from the implementation
view. Simplify it by giving each mode its own table with all paths and
references to other Protect options.
With this change some entries are duplicated, but we do not care since
duplicate mounts are first sorted by the most restrictive mode then
cleaned.
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Make ALSA entries, latency interface, mtrr, apm/acpi, suspend interface,
filesystems configuration and IRQ tuning readonly.
Most of these interfaces now days should be in /sys but they are still
available through /proc, so just protect them. This patch does not touch
/proc/net/...
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Move out mount calculation on its own function. Actually the logic is
smart enough to later drop nop and duplicates mounts, this change
improves code readability.
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src/core/namespace.c | 47 ++++++++++++++++++++++++++++++++++++-----------
1 file changed, 36 insertions(+), 11 deletions(-)
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Instead of having all these paths everywhere, put the ones that are
protected by ProtectKernelTunables= into their own table. This way it
is easy to add paths and track which ones are protected.
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There's no point in mounting these, if they are outside of the root directory
we'll move to.
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already is one
Let's not stack mounts needlessly.
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This adds logic to chase symlinks for all mount points that shall be created in
a namespace environment in userspace, instead of leaving this to the kernel.
This has the advantage that we can correctly handle absolute symlinks that
shall be taken relative to a specific root directory. Moreover, we can properly
handle mounts created on symlinked files or directories as we can merge their
mounts as necessary.
(This also drops the "done" flag in the namespace logic, which was never
actually working, but was supposed to permit a partial rollback of the
namespace logic, which however is only mildly useful as it wasn't clear in
which case it would or would not be able to roll back.)
Fixes: #3867
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Let's create the new namespace only after we validated and processed all
parameters, right before we start with actually mounting things.
This way, the window where we can roll back is larger (not that it matters
IRL...)
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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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Previously, if ReadWritePaths= was nested inside a ReadOnlyPaths=
specification, then we'd first recursively apply the ReadOnlyPaths= paths, and
make everything below read-only, only in order to then flip the read-only bit
again for the subdirs listed in ReadWritePaths= below it.
This is not only ugly (as for the dirs in question we first turn on the RO bit,
only to turn it off again immediately after), but also problematic in
containers, where a container manager might have marked a set of dirs read-only
and this code will undo this is ReadWritePaths= is set for any.
With this patch behaviour in this regard is altered: ReadOnlyPaths= will not be
applied to the children listed in ReadWritePaths= in the first place, so that
we do not need to turn off the RO bit for those after all.
This means that ReadWritePaths=/ReadOnlyPaths= may only be used to turn on the
RO bit, but never to turn it off again. Or to say this differently: if some
dirs are marked read-only via some external tool, then ReadWritePaths= will not
undo it.
This is not only the safer option, but also more in-line with what the man page
currently claims:
"Entries (files or directories) listed in ReadWritePaths= are
accessible from within the namespace with the same access rights as
from outside."
To implement this change bind_remount_recursive() gained a new "blacklist"
string list parameter, which when passed may contain subdirs that shall be
excluded from the read-only mounting.
A number of functions are updated to add more debug logging to make this more
digestable.
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If /foo is marked to be read-only, and /foo/bar too, then the latter may be
suppressed as it has no effect.
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If a dir is marked to be inaccessible then everything below it should be masked
by it.
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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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Assorted fixes
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Fix bug introduced by #3263: mount(2) return value is 0 or -1, not errno.
Thanks to Evgeny Vereshchagin (@evverx) for reporting.
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We generally try to avoid strerror(), due to its threads-unsafety, let's do
this here, too.
Also, let's be tiny bit more explanatory with the log messages, and let's
shorten a few things.
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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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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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Drop all dangling old /dev mounts before mounting a new private /dev tree.
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This feature will not be used anytime soon, so remove a bit of cruft.
The BusPolicy= config directive will stay around as compat noop.
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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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socket-util.[ch]
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There are more than enough to deserve their own .c file, hence move them
over.
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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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Also, make it slightly more powerful, by accepting a flags argument, and
make it safe for handling if more than one cmsg attribute happens to be
attached.
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Let's also clean up single-line while and for blocks.
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The previous coccinelle semantic patch that improved usage of
log_error_errno()'s return value, only looked for log_error_errno()
invocations with a single parameter after the error parameter. Update
the patch to handle arbitrary numbers of additional arguments.
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Turns this:
r = -errno;
log_error_errno(errno, "foo");
into this:
r = log_error_errno(errno, "foo");
and this:
r = log_error_errno(errno, "foo");
return r;
into this:
return log_error_errno(errno, "foo");
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It's only marginally shorter then the usual for() loop, but certainly
more readable.
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A small typo in ee818b8 caused /home to be put in read-only instead of
/usr when ProtectSystem was enabled (ie: not set to "no").
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When a service is chrooted with the option RootDirectory=/opt/..., then
the options PrivateDevices, PrivateTmp, ProtectHome, ProtectSystem must
mount the directories under $RootDirectory/{dev,tmp,home,usr,boot}.
The test-ns tool can test setup_namespace() with and without chroot:
$ sudo TEST_NS_PROJECTS=/home/lennart/projects ./test-ns
$ sudo TEST_NS_CHROOT=/home/alban/debian-tree TEST_NS_PROJECTS=/home/alban/debian-tree/home/alban/Documents ./test-ns
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Previously all bind mount mounts were applied in the order specified,
followed by all tmpfs mounts in the order specified. This is
problematic, if bind mounts shall be placed within tmpfs mounts.
This patch hence reworks the custom mount point logic, and alwas applies
them in strict prefix-first order. This means the order of mounts
specified on the command line becomes irrelevant, the right operation
will always be executed.
While we are at it this commit also adds native support for overlayfs
mounts, as supported by recent kernels.
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Try to keep syscalls as minimal as possible.
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The comparison function we use for qsorting paths is overly indifferent.
Consider these 3 paths for sorting:
/foo
/bar
/foo/foo
qsort() may compare:
"/foo" with "/bar" => 0, indifference
"/bar" with "/foo/foo" => 0, indifference
and assume transitively that "/foo" and "/foo/foo" are also indifferent.
But this is wrong, we want "/foo" sorted before "/foo/foo".
The comparison function must be transitive.
Use path_compare(), which behaves properly.
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1184016
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CID #1237550.
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