As with the previous commit, this is probably not actually privilege
escalation due to the use of an activation helper that cleans up its
environment, but let's be extra-careful here.
Reviewed-by: Thiago Macieira <thiago@kde.org>
[adjusted commit message -smcv]
UpdateActivationEnvironment is the one dbus-daemon API call that is
obviously dangerous (it is intended for the session bus),
so the default system.conf does not allow anyone to call it.
It has recently come to the D-Bus maintainers' attention that some
system services incorrectly install D-Bus policy rules that allow
arbitrary method calls to any destination as long as they have a
"safe" object path. This is not actually safe: some system services
that use low-level D-Bus bindings like libdbus, including dbus-daemon
itself, provide the same API on all object paths.
Unauthorized calls to UpdateActivationEnvironment are probably just
resource consumption rather than privilege escalation, because on
the system bus, the modified environment is only used to execute
a setuid wrapper that avoids LD_PRELOAD etc. via normal setuid
handling, and sanitizes its own environment before executing
the real service. However, it's safest to assume the worst and
treat it as a potential privilege escalation.
Accordingly, as a hardening measure to avoid privilege escalation on
systems with these faulty services, stop allowing calls to
("/com/example/Whatever",
"org.freedesktop.DBus.UpdateActivationEnvironment")
and only allow ("/org/freedesktop/DBus",
"org.freedesktop.DBus.UpdateActivationEnvironment").
We deliberately continue to provide read-only APIs like
GetConnectionUnixUser at all object paths, for backwards compatibility.
Reviewed-by: Thiago Macieira <thiago@kde.org>
[adjusted commit message to note that this is probably only DoS -smcv]
This reverts commit 54d26df52b.
It appears this change may cause intermittent slow or failed boot,
more commonly on slower/older machines, in at least Mageia and
possibly also Debian. This would indicate that while the system
is under load, system services are not completing authentication
within 5 seconds.
This change was not the main part of fixing CVE-2014-3639, but does
help to mitigate that attack. As such, increasing this timeout makes
the denial of service attack described by CVE-2014-3639 somewhat
more effective: a local user connecting to the system bus repeatedly
from many parallel processes can cause other users' attempts to
connect to take longer.
If your machine boots reliably with the shorter timeout, and
resilience against local denial of service attacks is important
to you, putting this in /etc/dbus-1/system-local.conf
or a file matching /etc/dbus-1/system.d/*.conf can restore
the lower limit:
<busconfig>
<limit name="auth_timeout">5000</limit>
</busconfig>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=86431
This makes bus_context_check_security_policy follow convention of
setting errors if function indicates failure and has error parameter.
Notable implication is that AccessDenied error will be sent if sending message
to addressed recipient is denied due to receive rule. Previously, message
was silently dropped.
This also fixes assertion failure when message is denied at addressed recipient
while sending pending auto activation messages.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=86194
This ensures that our rlimit is actually high enough to avoid the
denial of service described in CVE-2014-3636 part A.
CVE-2014-7824 has been allocated for this incomplete fix.
Restore the original rlimit for activated services, to avoid
them getting undesired higher limits.
(Thanks to Alban Crequy for various adjustments which have been
included in this commit.)
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=85105
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=69702
Reviewed-by: Patrick Welche <prlw1@cam.ac.uk>
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>
Tested-by: Patrick Welche <prlw1@cam.ac.uk>
Otherwise, this would fail on, for instance, QNX.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=69702
Reviewed-by: Patrick Welche <prlw1@cam.ac.uk>
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>
Tested-by: Patrick Welche <prlw1@cam.ac.uk>
[originally part of the previous commit -smcv]
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=69702
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=69702
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>
Tested-by: Patrick Welche <prlw1@cam.ac.uk>
We know that Linux, FreeBSD and OpenBSD are "first class citizens"
for credentials-passing, with NetBSD not far behind: people have
turned up on the bug tracking system and told us that tests passed.
On other Unixes, we can't really assert that it works, until someone
who runs them tells us that it worked for them.
Additions to these lists are welcome.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=69702
Reviewed-by: Patrick Welche <prlw1@cam.ac.uk>
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>
Tested-by: Patrick Welche <prlw1@cam.ac.uk>
As is already noted in a comment in
_dbus_babysitter_set_child_exit_error(), if the grandchild fails
to exec() the desired process, we get both CHILD_EXEC_FAILED (with
an errno) and CHILD_EXITED (with a status), and we want to report
the former, since it is more informative. However, clearing
sitter->errnum meant we lose the errno value.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=24821
Reviewed-by: Ross Lagerwall
That implementation no longer exists, so neither 0xABCDEF nor 0xABCDEF2
has any special meaning any more.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=54972
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>
As an implementation detail, dbus-daemon handles this situation by
artificially triggering a timeout (even if its configured timeout for
method calls is in fact infinite). However, using the same debug message
for both is misleading, and can lead people who are debugging a service
crash to blame dbus-daemon instead, wasting their time.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=76112
Some functions in dbus-transport-socket.c make a (wrapped)
socket syscall, then call other APIs, then test the result and
errno of the socket syscall.
This would break horribly if those "other APIs" overwrote errno with
their own value (... and this is part of why errno is an awful API).
Notably, if running under DBUS_VERBOSE, _dbus_verbose() is basically
fprintf(), which sets errno; and our Unix fd-passing support
makes calls of the form _dbus_verbose ("Read/wrote %i unix fds\n", n)
between the syscall and the result processing.
Maybe one day we'll convert all of dbus' syscall wrappers to either
raise a DBusError, or use the "negative errno" convention that systemd
borrowed from the Linux kernel, and in particular, we would need to
do that if we ever ported it to a platform where socket error reporting
was not basically errno. However, in practice everyone uses something
derived from BSD sockets, so "this sets errno, you know what errno is"
is a good enough internal API if we make sure to use it correctly.
Nothing calls _dbus_get_is_errno_nonzero(), so I just removed it instead
of converting it to the new calling convention.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=83625
Heavily based on a patch from Lennart Poettering.
This is useful for authentication frameworks such as polkit, but this
flag is supposed to be generic, and not be bound to any implementation
of such a framework.
The dbus specification already clarifies that unknown flags must be
ignored, the reference implementation and the other implementations we
checked indeed ignore any new flags, hence we should be fine with
compatibility here.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=83449
Because test-dbus and test-bus lives in subdirectory dbus/bus, we need
to define make 'check' in top level source directory.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=73689
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Historically, CMake used the glob *.conf.in whereas Autotools listed
the files explicitly. This used to be equivalent, but broke down
when we added example-*.conf.in which are just snippets rather than
complete configuration files (they're intended to go in session.d
or system.d, or otherwise get included by the main config file).
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=73689
Reviewed-by: Ralf Habacker <ralf.habacker@freenet.de>
