This means we can systematically pass the environment variables
through bwrap(1), even if it is setuid and thus is filtering out
security-sensitive environment variables. bwrap ends up being
run with an empty environment instead.
This did not regress in 6d1773d "run: Convert all environment variables
into bwrap arguments", because the LD_LIBRARY_PATH special case in
flatpak_run_add_environment_args() was already not used here; but it's
a bug fix along the same lines as fixing the regression.
Signed-off-by: Simon McVittie <smcv@collabora.com>
This means we can systematically pass the environment variables
through bwrap(1), even if it is setuid and thus is filtering out
security-sensitive environment variables. bwrap ends up being
run with an empty environment instead.
As with the previous commit, this regressed while fixing CVE-2021-21261.
Fixes: 6d1773d2 "run: Convert all environment variables into bwrap arguments"
Signed-off-by: Simon McVittie <smcv@collabora.com>
This means we can systematically pass the environment variables
through bwrap(1), even if it is setuid and thus is filtering out
security-sensitive environment variables. bwrap itself ends up being
run with an empty environment instead.
This fixes a regression when CVE-2021-21261 was fixed: before the
CVE fixes, LD_LIBRARY_PATH would have been passed through like this
and appeared in the `flatpak build` shell, but during the CVE fixes,
the special case that protected LD_LIBRARY_PATH was removed in favour
of the more general flatpak_bwrap_envp_to_args(). That reasoning only
works if we use flatpak_bwrap_envp_to_args(), consistently, everywhere
that we run the potentially-setuid bwrap.
Fixes: 6d1773d2 "run: Convert all environment variables into bwrap arguments"
Resolves: https://github.com/flatpak/flatpak/issues/4080
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=980323
Signed-off-by: Simon McVittie <smcv@collabora.com>
This adds `NULL` protection to the `subpaths` argument to
`flatpak_dir_system_helper_call_deploy()`, just like already exists for
other arguments.
It’s a second layer of defence against bugs like fixed in the previous
commit.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
If an app had no deploy data, and `flatpak_dir_update()` was called with
`opt_subpaths == NULL`, then `arg_subpaths` passed to
`flatpak_dir_system_helper_call_deploy()` would be `NULL`, which causes
an assertion failure from an internal `g_variant_new()` call:
```
g_variant_new_strv: assertion 'length == 0 || strv != NULL' failed
```
Fix that by setting the `subpaths` to an empty array if nothing else is
specified.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
This passes -fsanitize=address in the right place.
Passing it this way instead of CFLAGS allows us to strategically
not add sanitize in specific places as needed.
This is really just syntactic sugar for running `env -u VAR ... COMMAND`,
but env(1) is inconvenient when the form of the COMMAND is not known:
if the COMMAND might contain an equals sign, you end up having to run
`env -u VAR sh -c 'exec "$@"' sh COMMAND`. Let's make this simpler.
This follows up from GHSA-4ppf-fxf6-vxg2 to fix an issue that I noticed
while resolving that vulnerability, but is not required for fixing the
vulnerability.
Signed-off-by: Simon McVittie <smcv@collabora.com>
This follows up from GHSA-4ppf-fxf6-vxg2 to fix missing functionality
that I noticed while resolving that vulnerability, but is not required
for fixing the vulnerability.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Some consumers of environment variables distinguish between present
with an empty value and absent. For example, if an environment variable
represents a search path like VK_ICD_FILENAMES, unsetting it often
results in use of a default, but setting it to the empty string results
in not searching any locations, which is sometimes what is desired.
The shell syntax "${BAR-unset}" expands to the value of ${BAR} if it
is set to anything (even an empty string), or to "unset" if not.
We can use that in the unit test to check that BAR is set to the
empty string in this case.
This follows up from GHSA-4ppf-fxf6-vxg2 to fix an issue that I noticed
while resolving that vulnerability, but is not required for fixing the
vulnerability.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Previously, if you launched a subsandbox while specifying environment
variable overrides, any environment variable overrides that existed
in the parent Flatpak app would take precedence:
host$ flatpak run --env=FOO=1 --command=bash example.app
[📦 example.app ~]$ env | grep FOO
FOO=1
[📦 example.app ~]$ flatpak-spawn --env=FOO=x sh -c 'env | grep FOO'
FOO=1
This does not seem like least-astonishment, and in particular will
cause problems if the app wants to override LD_LIBRARY_PATH in the
subsandbox. Change the precedence so that the environment variables
set by flatpak-spawn will "win":
host$ flatpak run --env=FOO1=1 --env=FOO2=2 --command=bash example.app
[📦 example.app ~]$ env | grep FOO
FOO1=1
FOO2=2
[📦 example.app ~]$ flatpak-spawn --env=FOO1=x sh -c 'env | grep FOO'
FOO1=x
FOO2=2
This follows up from GHSA-4ppf-fxf6-vxg2 to fix an issue that I noticed
while resolving that vulnerability, but is not required for fixing the
vulnerability.
Signed-off-by: Simon McVittie <smcv@collabora.com>
For the portal's use of --env-fd= to be safe, we want the environment
variables that it sets to end up in the environment for the program
that is run by `bwrap` as process 2, but they must not go into the
environment that gets used to run `flatpak run` or `bwrap`. Assert
that this is the case.
For completeness, we're testing both --env= and --env-fd= here,
even though the earlier commit
"portal: Do not use caller-supplied variables in environment"
always uses --env-fd=.
Part-of: https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2
Signed-off-by: Simon McVittie <smcv@collabora.com>
If the caller specifies a variable that can be used to inject arbitrary
code into processes, we must not allow it to enter the environment
block used to run `flatpak run`, which runs unsandboxed.
This change requires the previous commit "context: Add --env-fd option",
which adds infrastructure used here.
To be secure, this change also requires the previous commit
"run: Convert all environment variables into bwrap arguments", which
protects a non-setuid bwrap(1) from the same attack.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Part-of: https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2
This avoids some of them being filtered out by a setuid bwrap. It also
means that if they came from an untrusted source, they cannot be used
to inject arbitrary code into a non-setuid bwrap via mechanisms like
LD_PRELOAD.
Because they get bundled into a memfd or temporary file, they do not
actually appear in argv, ensuring that they remain inaccessible to
processes running under a different uid (which is important if their
values are tokens or other secrets).
Signed-off-by: Simon McVittie <smcv@collabora.com>
Part-of: https://github.com/flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2
Iterate the `GMainContext` manually instead. This makes the exit
condition from the loop much more obvious, and eliminates the potential
class of problems where `g_main_loop_quit()` is called before
`g_main_loop_run()` and has no effect.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
On systems with no XDG_RUNTIME_DIR, PulseAudio falls back to creating
a temporary directory in /tmp, then creating a symlink in
legacy directory ~/.pulse or its more modern replacement ~/.config/pulse.
The symlink is named according to the machine ID, falling back to the
hostname.
Resolves: #4058
Might-resolve: #2169
Signed-off-by: Simon McVittie <smcv@collabora.com>
As with flatpak run --parent-expose-pids, this will only work if we have
a working, non-setuid bwrap. Systems where user namespace creation is
restricted and bwrap needs to be setuid (Debian 10, RHEL/CentOS 7,
Arch Linux linux-hardened kernel) will have degraded functionality.
This option is similar to --expose-pids, except that instead of making
the subsandbox use a nested pid namespace inside the parent's, it makes
the subsandbox share the parent's pid namespace as-is, so that process
IDs in the parent and the subsandbox are interchangeable. This will
be useful if the parent and the subsandbox communicate via protocols
that assume a global view of the process ID namespace, for example
passing process IDs across an AF_UNIX socket or in shared memory.
In particular, this will be useful for Steam's pressure-vessel container
tool: the IPC between the Steam client and the "game overlay" loaded into
Steam games uses process IDs, and becomes confused if they don't match up.
This weakens the security boundary between a subsandbox and the parent,
but that's OK in some cases, especially if the subsandbox is being used
as a way to get a different runtime /usr (flatpak-spawn --latest-version
or #4018) rather than as a security boundary.
Signed-off-by: Simon McVittie <smcv@collabora.com>
If network access is allowed, then we should probably allow name
resolution too.
This should be enough to make nss-resolve work inside flatpak. However,
it cannot be tested with GNOME runtimes, because GNOME runtimes do not
contain systemd. It also cannot be tested with the Fedora 33 flatpak
runtime, because this runtime contains systemd 246, where nss-resolve
uses D-Bus rather than varlink to communicate with systemd-resolved. And
there is no rawhide runtime, and will be no Fedora 34 runtime until F34
is branched. So currently it's not possible to actually test this
without building a custom runtime, which I have not attempted to do. I
have built flatpak myself and verified the resolved socket is mounted
properly inside the sandbox, but it would be better to test if it
actually works with a runtime that contains systemd 247.
Related: https://bugzilla.redhat.com/show_bug.cgi?id=1912131
This brings us closer to matching what happens in libpulse.so.0.
This path is the default for a system-wide PulseAudio instance, which
is discouraged on non-embedded systems but is easy to check for.
In particular, SteamOS, an "appliance"-style gaming OS, uses this
socket.
Adapted from Steam's pressure-vessel container tool, which reuses
various Flatpak modules, including this function.
Signed-off-by: Simon McVittie <smcv@collabora.com>
fusermount requires /etc/mtab, but not all Debian buildd chroots
have that file, either as a regular file or as a symlink to
/proc/self/mounts.
(This is similar to commit b07b48e2, but for C code.)
Signed-off-by: Simon McVittie <smcv@debian.org>
This reduces the amount of shell in use, and the number of subprocesses
spawned by that, so our system environment generator is as fast as
possible when used in the critical startup path.
It adds a new system environment generator so that the system flatpak
installation can be used outside of a user session. In particular, this
allows enumeration of system-installed flatpaks in gnome-initial-setup
in order to set parental controls on them.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
This is the environment needed to use flatpaks; a following commit will
hook this up to the systemd environment generator.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
In addition to the old summary.idx.sig we now create an identical file
in `summaries/$DIGEST.idx.sig`, where the digest is of the summary
index itself. This means it will have a unique name and there will
never be issues where downloading the index and signature will race
during an update.
We keep the new and the previous digested sigs every update to avoid
removing the previous one while its in use.
As suggested by simon in https://github.com/flatpak/flatpak/issues/3983
and https://github.com/ostreedev/ostree/issues/2250
