Minor refactoring to use the filePair struct for both init sock and log pipe
Co-authored-by: Julia Nedialkova <julianedialkova@hotmail.com>
Signed-off-by: Georgi Sabev <georgethebeatle@gmail.com>
Refactor configuring logging into a reusable component
so that it can be nicely used in both main() and init process init()
Co-authored-by: Georgi Sabev <georgethebeatle@gmail.com>
Co-authored-by: Giuseppe Capizzi <gcapizzi@pivotal.io>
Co-authored-by: Claudia Beresford <cberesford@pivotal.io>
Signed-off-by: Danail Branekov <danailster@gmail.com>
Add support for children processes logging (including nsexec).
A pipe is used to send logs from children to parent in JSON.
The JSON format used is the same used by logrus JSON formatted,
i.e. children process can use standard logrus APIs.
Signed-off-by: Marco Vedovati <mvedovati@suse.com>
secure_getenv is a Glibc extension and so this code does not compile
on Musl libc any more after this patch.
secure_getenv is only intended to be used in setuid binaries, in
order that they should not trust their environment. It simply returns
NULL if the binary is running setuid. If runc was installed setuid,
the user can already do anything as root, so it is game over, so this
check is not needed.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
There are some circumstances where sendfile(2) can fail (one example is
that AppArmor appears to block writing to deleted files with sendfile(2)
under some circumstances) and so we need to have a userspace fallback.
It's fairly trivial (and handles short-writes).
Signed-off-by: Aleksa Sarai <asarai@suse.de>
The usage of memfd_create(2) and other copying techniques is quite
wasteful, despite attempts to minimise it with _LIBCONTAINER_STATEDIR.
memfd_create(2) added ~10M of memory usage to the cgroup associated with
the container, which can result in some setups getting OOM'd (or just
hogging the hosts' memory when you have lots of created-but-not-started
containers sticking around).
The easiest way of solving this is by creating a read-only bind-mount of
the binary, opening that read-only bindmount, and then umounting it to
ensure that the host won't accidentally be re-mounted read-write. This
avoids all copying and cleans up naturally like the other techniques
used. Unfortunately, like the O_TMPFILE fallback, this requires being
able to create a file inside _LIBCONTAINER_STATEDIR (since bind-mounting
over the most obvious path -- /proc/self/exe -- is a *very bad idea*).
Unfortunately detecting this isn't fool-proof -- on a system with a
read-only root filesystem (that might become read-write during "runc
init" execution), we cannot tell whether we have already done an ro
remount. As a partial mitigation, we store a _LIBCONTAINER_CLONED_BINARY
environment variable which is checked *alongside* the protection being
present.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
Writing a file to tmpfs actually incurs a memcg penalty, and thus the
benefit of being able to disable memfd_create(2) with
_LIBCONTAINER_DISABLE_MEMFD_CLONE is fairly minimal -- though it should
be noted that quite a few distributions don't use tmpfs for /tmp (and
instead have it as a regular directory or subvolume of the host
filesystem).
Since runc must have write access to the state directory anyway (and the
state directory is usually not on a tmpfs) we can use that instead of
/tmp -- avoiding potential memcg costs with no real downside.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
In order to get around the memfd_create(2) requirement, 0a8e4117e7
("nsenter: clone /proc/self/exe to avoid exposing host binary to
container") added an O_TMPFILE fallback. However, this fallback was
flawed in two ways:
* It required O_TMPFILE which is relatively new (having been added to
Linux 3.11).
* The fallback choice was made at compile-time, not runtime. This
results in several complications when it comes to running binaries
on different machines to the ones they were built on.
The easiest way to resolve these things is to have fallbacks work in a
more procedural way (though it does make the code unfortunately more
complicated) and to add a new fallback that uses mkotemp(3).
Signed-off-by: Aleksa Sarai <asarai@suse.de>
For a variety of reasons, sendfile(2) can end up doing a short-copy so
we need to just loop until we hit the binary size. Since /proc/self/exe
is tautologically our own binary, there's no chance someone is going to
modify it underneath us (or changing the size).
Signed-off-by: Aleksa Sarai <asarai@suse.de>
My first attempt to simplify this and make it less costly focussed on
the way constructors are called. I was under the impression that the ELF
specification mandated that arg, argv, and actually even envp need to be
passed to functions located in the .init_arry section (aka
"constructors"). Actually, the specifications is (cf. [2]):
SHT_INIT_ARRAY
This section contains an array of pointers to initialization functions,
as described in ``Initialization and Termination Functions'' in Chapter
5. Each pointer in the array is taken as a parameterless procedure with
a void return.
which means that this becomes a libc specific decision. Glibc passes
down those args, musl doesn't. So this approach can't work. However, we
can at least remove the environment parsing part based on POSIX since
[1] mandates that there should be an environ variable defined in
unistd.h which provides access to the environment. See also the relevant
Open Group specification [1].
[1]: http://pubs.opengroup.org/onlinepubs/9699919799/
[2]: http://www.sco.com/developers/gabi/latest/ch4.sheader.html#init_array
Fixes: CVE-2019-5736
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
There are quite a few circumstances where /proc/self/exe pointing to a
pretty important container binary is a _bad_ thing, so to avoid this we
have to make a copy (preferably doing self-clean-up and not being
writeable).
We require memfd_create(2) -- though there is an O_TMPFILE fallback --
but we can always extend this to use a scratch MNT_DETACH overlayfs or
tmpfs. The main downside to this approach is no page-cache sharing for
the runc binary (which overlayfs would give us) but this is far less
complicated.
This is only done during nsenter so that it happens transparently to the
Go code, and any libcontainer users benefit from it. This also makes
ExtraFiles and --preserve-fds handling trivial (because we don't need to
worry about it).
Fixes: CVE-2019-5736
Co-developed-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Aleksa Sarai <asarai@suse.de>
Cgroup namespace can be configured in `config.json` as other
namespaces. Here is an example:
```
"namespaces": [
{
"type": "pid"
},
{
"type": "network"
},
{
"type": "ipc"
},
{
"type": "uts"
},
{
"type": "mount"
},
{
"type": "cgroup"
}
],
```
Note that if you want to run a container which has shared cgroup ns with
another container, then it's strongly recommended that you set
proper `CgroupsPath` of both containers(the second container's cgroup
path must be the subdirectory of the first one). Or there might be
some unexpected results.
Signed-off-by: Yuanhong Peng <pengyuanhong@huawei.com>
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
This PR decomposes `libcontainer/configs.Config.Rootless bool` into `RootlessEUID bool` and
`RootlessCgroups bool`, so as to make "runc-in-userns" to be more compatible with "rootful" runc.
`RootlessEUID` denotes that runc is being executed as a non-root user (euid != 0) in
the current user namespace. `RootlessEUID` is almost identical to the former `Rootless`
except cgroups stuff.
`RootlessCgroups` denotes that runc is unlikely to have the full access to cgroups.
`RootlessCgroups` is set to false if runc is executed as the root (euid == 0) in the initial namespace.
Otherwise `RootlessCgroups` is set to true.
(Hint: if `RootlessEUID` is true, `RootlessCgroups` becomes true as well)
When runc is executed as the root (euid == 0) in an user namespace (e.g. by Docker-in-LXD, Podman, Usernetes),
`RootlessEUID` is set to false but `RootlessCgroups` is set to true.
So, "runc-in-userns" behaves almost same as "rootful" runc except that cgroups errors are ignored.
This PR does not have any impact on CLI flags and `state.json`.
Note about CLI:
* Now `runc --rootless=(auto|true|false)` CLI flag is only used for setting `RootlessCgroups`.
* Now `runc spec --rootless` is only required when `RootlessEUID` is set to true.
For runc-in-userns, `runc spec` without `--rootless` should work, when sufficient numbers of
UID/GID are mapped.
Note about `$XDG_RUNTIME_DIR` (e.g. `/run/user/1000`):
* `$XDG_RUNTIME_DIR` is ignored if runc is being executed as the root (euid == 0) in the initial namespace, for backward compatibility.
(`/run/runc` is used)
* If runc is executed as the root (euid == 0) in an user namespace, `$XDG_RUNTIME_DIR` is honored if `$USER != "" && $USER != "root"`.
This allows unprivileged users to allow execute runc as the root in userns, without mounting writable `/run/runc`.
Note about `state.json`:
* `rootless` is set to true when `RootlessEUID == true && RootlessCgroups == true`.
Signed-off-by: Akihiro Suda <suda.akihiro@lab.ntt.co.jp>
Technically, this change should not be necessary, as the kernel
documentation claims that if you call clone(flags|CLONE_NEWUSER), the
new user namespace will be the owner of all other namespaces created in
@flags. Unfortunately this isn't always the case, due to various
additional semantics and kernel bugs.
One particular instance is SELinux, which acts very strangely towards
the IPC namespace and mqueue. If you unshare the IPC namespace *before*
you map a user in the user namespace, the IPC namespace's internal
kern-mount for mqueue will be labelled incorrectly and the container
won't be able to access it. The only way of solving this is to unshare
IPC *after* the user has been mapped and we have changed to that user.
I've also heard of this happening to the NET namespace while talking to
some LXC folks, though I haven't personally seen that issue.
This change matches our handling of user namespaces to be the same as
how LXC handles these problems.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
With the addition of our new{uid,gid}map support, we used to call
execvp(3) from inside nsexec. This would mean that the path resolution
for the binaries would happen in nsexec. Move the resolution to the
initial setup code, and pass the absolute path to nsexec.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
After quite a bit of debugging, I found that previous versions of this
patchset did not include newgidmap in a rootless setting. Fix this by
passing it whenever group mappings are applied, and also providing some
better checking for try_mapping_tool. This commit also includes some
stylistic improvements.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
Take advantage of the newuidmap/newgidmap tools to allow multiple
users/groups to be mapped into the new user namespace in the rootless
case.
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
[ rebased to handle intelrdt changes. ]
Signed-off-by: Aleksa Sarai <asarai@suse.de>
This allows the libcontainer to automatically clean up runc:[1:CHILD]
processes created as part of nsenter.
Signed-off-by: Alex Fang <littlelightlittlefire@gmail.com>
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>
This enables the support for the rootless container mode. There are many
restrictions on what rootless containers can do, so many different runC
commands have been disabled:
* runc checkpoint
* runc events
* runc pause
* runc ps
* runc restore
* runc resume
* runc update
The following commands work:
* runc create
* runc delete
* runc exec
* runc kill
* runc list
* runc run
* runc spec
* runc state
In addition, any specification options that imply joining cgroups have
also been disabled. This is due to support for unprivileged subtree
management not being available from Linux upstream.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
Effectively, !dumpable makes implementing rootless containers quite
hard, due to a bunch of different operations on /proc/self no longer
being possible without reordering everything.
!dumpable only really makes sense when you are switching between
different security contexts, which is only the case when we are joining
namespaces. Unfortunately this means that !dumpable will still have
issues in this instance, and it should only be necessary to set
!dumpable if we are not joining USER namespaces (new kernels have
protections that make !dumpable no longer necessary). But that's a topic
for another time.
This also includes code to unset and then re-set dumpable when doing the
USER namespace mappings. This should also be safe because in principle
processes in a container can't see us until after we fork into the PID
namespace (which happens after the user mapping).
In rootless containers, it is not possible to set a non-dumpable
process's /proc/self/oom_score_adj (it's owned by root and thus not
writeable). Thus, it needs to be set inside nsexec before we set
ourselves as non-dumpable.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
This sets the init processes that join and setup the container's
namespaces as non-dumpable before they setns to the container's pid (or
any other ) namespace.
This settings is automatically reset to the default after the Exec in
the container so that it does not change functionality for the
applications that are running inside, just our init processes.
This prevents parent processes, the pid 1 of the container, to ptrace
the init process before it drops caps and other sets LSMs.
This patch also ensures that the stateDirFD being used is still closed
prior to exec, even though it is set as O_CLOEXEC, because of the order
in the kernel.
https://github.com/torvalds/linux/blob/v4.9/fs/exec.c#L1290-L1318
The order during the exec syscall is that the process is set back to
dumpable before O_CLOEXEC are processed.
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
This implements {createTTY, detach} and all of the combinations and
negations of the two that were previously implemented. There are some
valid questions about out-of-OCI-scope topics like !createTTY and how
things should be handled (why do we dup the current stdio to the
process, and how is that not a security issue). However, these will be
dealt with in a separate patchset.
In order to allow for late console setup, split setupRootfs into the
"preparation" section where all of the mounts are created and the
"finalize" section where we pivot_root and set things as ro. In between
the two we can set up all of the console mountpoints and symlinks we
need.
We use two-stage synchronisation to ensures that when the syscalls are
reordered in a suboptimal way, an out-of-place read() on the parentPipe
will not gobble the ancilliary information.
This patch is part of the console rewrite patchset.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
config.cloneflag is not mandatory, when using `runc exec`,
config.cloneflag can be empty, and even then it won't be
`-1` but `0`.
So this validation is totally wrong and unneeded.
Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
Without this patch applied, RHEL's SELinux policies cause container
creation to not really work. Unfortunately this might be an issue for
rootless containers (opencontainers/runc#774) but we'll cross that
bridge when we come to it.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
Depending on your SELinux setup, the order in which you join namespaces
can be important. In general, user namespaces should *always* be joined
and unshared first because then the other namespaces are correctly
pinned and you have the right priviliges within them. This also is very
useful for rootless containers, as well as older kernels that had
essentially broken unshare(2) and clone(2) implementations.
This also includes huge refactorings in how we spawn processes for
complicated reasons that I don't want to get into because it will make
me spiral into a cloud of rage. The reasoning is in the giant comment in
clone_parent. Have fun.
In addition, because we now create multiple children with CLONE_PARENT,
we cannot wait for them to SIGCHLD us in the case of a death. Thus, we
have to resort to having a child kindly send us their exit code before
they die. Hopefully this all works okay, but at this point there's not
much more than we can do.
Signed-off-by: Aleksa Sarai <asarai@suse.de>
Aleksa Sarai
Jonathan Rudenberg
Akihiro Suda
Georgi Sabev
Danail Branekov
Marco Vedovati
Justin Cormack
Christian Brauner
Yuanhong Peng
Mrunal Patel
Michael Crosby
Akihiro Suda
Yan Zhu
Antonio Murdaca
Giuseppe Scrivano
Alex Fang
yangshukui
Christy Perez
Qiang Huang
Daniel, Dao Quang Minh
rajasec