This allows you to reuse an existing user namespace to set up all the
other namespaces, entering that instead of creating a new one. The
reason you want to do this is that you can then also reuse other
namespaces that are owned by the user namespace. Typically you use
this to partially re-enter a previoulsy created bubblewrap sandbox.
This also adds --userns2 which is similar to --userns, but this is
switched into at the end instead of the start. Bubblewrap sometimes
creates nested such user namespaces[1], and to be able to reuse such a
setup we need to similarly reuse both namespaces via --userns2.
Technically using setns() is probably safe even in the privileged
case, because we got passed in a file descriptor to the namespace, and
that can only be gotten if you have ptrace permissions against the
target, and then you could do whatever to the namespace
anyway. However, for practical reasons this isn't useable for bwrap,
because (as described in a comment in acquire_privs()) setuid mode
causes root to own the namespaces that it creates. So as you will not
be able to access these namespaces for reuse anyway, its best to
disable it (in case of unexpected security issues).
[1] This is to work around an issue with mounting devpts without uid 0
mapped in the user namespace, where the outer namespace owns all the
other namespaces but the inner one has the right mappings.
Now that we're properly getting rid of root in these we can mark it
dumpable, which enables use of some /proc files, like /proc/$pid/root that
was previously not accessible for pid1 in the sandbox.
It turns out we have this check in drop_privs():
if (getuid () == 0 && setuid (opt_sandbox_uid) < 0)
Which is supposed to drop back to the regular uid in the case
we're in setuid mode and we're in the monitor_child() or do_init()
processes.
Unfortunately we're setuid, not plain root, so uid is not 0, but euid is zero.
This caused the monitoring processes to be running partially as root
which shows up weird in /proc.
Fix this by checking euid for 0 instead.
Make sure the namespace information that is written to info.json
and json-status.json matches the namespace id inside the sandbox.
Closes: #323
Approved by: alexlarsson
When writing the info-fd or the json-status-fd and a new pid name-
space is created, write the namespace id to the info/json. The
namespace id is encoded in the inode (and device) number of the
symbolic link in /proc/<pid>/ns/<namespace>, see namespaces(7)
for more information.
We obtain the information before we drop privileges, which is needed
when bwrap is run as setuid because then the namespace information
is not readable after having dropped the privileges.
Additionally we no retain the CAP_SYS_PTRACE capability because
that is needed to de-reference the links in /proc/<pid>/ns.
The user namespace information is omitted, because at the time when
we obtain the namespace id information, the user namespace is not yet
the new one, i.e. unshare (CLONE_NEWUSER), comes later.
Closes: #323
Approved by: alexlarsson
When optional cgroup unsharing was requested and the test for it
succeeds, set opt_unshare_cgroup to TRUE so it can be used later
to inspect if cgroup unsharing is enabled.
Closes: #323
Approved by: alexlarsson
Fedora 27 has been EOL for a while now... bump it to 29.
It'd be nice to test against FCOS, though it's not currently supported
by PAPR. It's in maintenance mode, but I might add support for it as a
stopgap. Medium-term though, I want to deprecate PAPR in favour of other
CI solutions.
Anyway, for now hopefully this should fix the CI on this repo.
Closes: #327
Approved by: alexlarsson
An attacker could pre-create /tmp/.bubblewrap-$UID and make it a
non-directory, non-symlink (in which case mounting our tmpfs would fail,
causing denial of service), or make it a symlink under their control
(potentially allowing bad things if the protected_symlinks sysctl is
not enabled).
Instead, temporarily mount the tmpfs on a directory that we are sure
exists and is not attacker-controlled. /tmp (the directory itself, not
a subdirectory) will do.
Fixes: #304
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=923557
Signed-off-by: Simon McVittie <smcv@debian.org>
Closes: #305
Approved by: cgwalters
The exit code is only reported if it exited after a successful exec.
This is accomplished with a pipe, where the write end is closed on exec.
To distinguish between pipe-close pre-exec and at-exec,
data is written to the pipe immediately before calling exec
so if it is closed before exec the pipe is empty
and if it is closed during exec it contains a 1 byte value.
To further distinguish between a successful exec and a failed exec,
on exec failure a second value is written.
Signed-off-by: Richard Maw <richard.maw@codethink.co.uk>
Closes: #257
Closes: #293
Approved by: cgwalters
For the non-suid case, we were assuming that the host system would have
merged /usr (e.g. /bin -> /usr/bin). This isn't yet the case for all
distros, so let's handle both.
Closes: #290
Approved by: smcv
These ignore source files not existing which allows bwrap using
applications to avoid repeatedly checking if files exist.
Closes: #283
Approved by: alexlarsson
Some variables like base_path ("/run/user/%d/.bubblewrap") are
declared with the cleanup attribute in main(), but this cleanup is not
run when in the parent process, since it calls exit() in monitor_child().
Use return statements instead of exit() so that cleanup attributes
will be run.
Closes: #271
Approved by: smcv
Keep a reference to the previous working directory and use it for the
umount.
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
Closes: #256
Approved by: cgwalters
Skip these mounts when the process will keep CAP_SYS_ADMIN as it will
anyway able to umount them.
This fix the case of running bwrap inside of a bwrap with a new pid
namespace and mount /proc.
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
Closes: #256
Approved by: cgwalters
This is preparatory work for supporting recursive bwrap. Without this, using
`mount()` on the second `/` won't work, since it won't be a mount point.
Closes: #256
Approved by: cgwalters
This shouldn't matter unless someone wants to run an inadvisably-named
executable, but it's best-practice for commands that pass on some
of their arguments to a subsequent command.
It allows an invocation like:
bwrap --ro-bind /container / -- "$@"
to search PATH in the container for an executable named according to
"$1", even if $1 has a pathological value like
"--this-has-a-stupid-name--", or even a value that might be
deliberately trying to break bwrap's parsing like "--bind".
Fixes: #259
Signed-off-by: Simon McVittie <smcv@collabora.com>
Closes: #261
Approved by: cgwalters
For NFS mounts if we call mkdir() on a read-only mount (such as when
we've created a read-only bind mount) the kernel will nor return EEXIST
even when the directory exists, instead returning EROFS.
So, we add (and use) an ensure_dir() helper that stats before calling
mkdir.
Closes: #258
Approved by: giuseppe
According to PEP 394, the python command is meant to be Python 2
until at least 2020, so in practice this script will be run with
Python 2 for now (except on Arch Linux); but it seems good to be
more future-proof.
In Python 3, os.write() takes a bytestring (bytes object), not a
text string (str/unicode object). In Python 2 ≥ 2.6, the b'' syntax
is supported and gives a str object, because that was a bytestring
in Python 2; either way, b'1' is an acceptable argument to os.write().
In Python ≥ 3.4, the result of os.pipe() is close-on-exec
(non-inheritable) by default, so undo that where needed.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Closes: #246
Approved by: giuseppe
This means we can use it with an installed bwrap, which seems a more
common use of a demo script than a just-compiled bwrap, and is
consistent with the shell scripts.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Closes: #246
Approved by: giuseppe
On systems without the /usr merge, it's almost certainly in /usr,
so this script would have failed.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Closes: #246
Approved by: giuseppe
Per open(2) man page:
When O_PATH is specified in flags, flag bits other than O_CLOEXEC
, O_DIRECTORY, and O_NOFOLLOW are ignored.
Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Closes: #244
Approved by: cgwalters
The options --file, --bind-data and --ro-bind-data take a file
descriptor as first argument. This FD is then used to set up the new
root file system. These FDs are then closed after this step. However,
when the privileged mode is used, this step is run in a child process,
hence leaking the FDs in the parent process.
To avoid future omissions, this patch walk through all the file
descriptors tied to an option and try to close them. To avoid a double
close, it marks FDs closed by setup_newroot as such.
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Closes: #243
Approved by: cgwalters
This means we can compile on Debian 8 'jessie', currently the
"oldstable" distribution. It's consistent with what would happen
if we knew PR_CAP_AMBIENT at compile-time but the kernel didn't support
it at runtime.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Closes: #242
Approved by: cgwalters
README.md and the demos are documentation that could be useful to
install, the spec file can be used by rpmbuild -ta, and the autogen.sh
and editor and uncrustify configuration could be useful for distro
packagers contributing patches upstream from a tree based on tarball
imports.
I arbitrarily left out CI configuration for PAPR and Travis-CI, since
these always take their source code from git anyway.
git.mk is excluded because it contains comments saying it should be.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Closes: #236
Approved by: giuseppe
The first attempt caused a use-after-free because the arguments parsed
from --args are passed to parse_args_recurse(), and the other cases
there may take those pointers (without copying) into SetupOp structures,
which persist after data is freed.
Fix that by treating data more like the argv to main(): an allocation
which exists throughout the life of the program. Do that by hoisting its
declaration out as a global, and then pulling the allocated data into a
cleanup_free variable in main(), to tie its lifecycle to main().
The alternative is to strdup() each one of the argv elements when they
are used in parse_args_recurse(), but that would mean a lot more
allocations and frees, and a lot of code churn.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
https://github.com/projectatomic/bubblewrap/issues/224
Closes: #237
Approved by: smcv
A new test was added in commit c09c1e53, but the total number of tests
wasn’t incremented. Fix that.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Closes: #237
Approved by: smcv
We've got a lot of new features and bugfixes since 0.1.8. Let's cut a new
release before we start landing even more things like the `pivot_root()` PR.
Closes: #232
Approved by: smcv
It may not always be obvious what the source of any particular error
message is. For instance, "Can't find source path" errors could be
perceived as coming from either the shell, loader, bubblewrap, or the
wrapped application, especially when a previously-configured program
stops working due to some external circumstances.
Thus, disambiguate the source of bubblewrap's error messages by
printing them with a "bwrap: " prefix.
Closes: #234
Approved by: cgwalters
I was looking at what fds flatpak injects, and realized this is actually just a
bubblewrap bug; there's no reason for us to leak this to the child, so don't.
It took me a while to work out/remember that our `close_extra_fds()` bits are
only intended to handle processes *other* than the final target, i.e. we want to
close fds in our init process. For the final child process, we need to support
passing arbitrary fds though, so `close_extra_fds()` can't apply to the child.
Closes: #221
Approved by: smcv
