Each connection that is an active monitor holds a pointer to its own
link in this list, via BusConnectionData.link_in_monitors. We can't
validly free the list while these pointers exist: that would be a
use-after-free, when each connection gets disconnected and tries to
remove itself from the list.
Instead, let each connection remove itself from the list, then assert
that the list has become empty.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Resolves: https://gitlab.freedesktop.org/dbus/dbus/issues/291
(cherry picked from commit b034b83b59)
Spotted by Mubin. This documentation relates to the code in
add_bus_environment() in bus/activation.c.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Fixes: #275
(cherry picked from commit bf71a58e4a)
We don't actually complete successful authentication, because that
would require us to generate a cookie and compute the correct SHA1,
which is difficult to do in a deterministic authentication script.
However, we do assert that dbus#269 (CVE-2019-12749) has been fixed.
Signed-off-by: Simon McVittie <smcv@collabora.com>
The DBUS_COOKIE_SHA1 authentication mechanism aims to prove ownership
of a shared home directory by having the server write a secret "cookie"
into a .dbus-keyrings subdirectory of the desired identity's home
directory with 0700 permissions, and having the client prove that it can
read the cookie. This never actually worked for non-malicious clients in
the case where server uid != client uid (unless the server and client
both have privileges, such as Linux CAP_DAC_OVERRIDE or traditional
Unix uid 0) because an unprivileged server would fail to write out the
cookie, and an unprivileged client would be unable to read the resulting
file owned by the server.
Additionally, since dbus 1.7.10 we have checked that ~/.dbus-keyrings
is owned by the uid of the server (a side-effect of a check added to
harden our use of XDG_RUNTIME_DIR), further ruling out successful use
by a non-malicious client with a uid differing from the server's.
Joe Vennix of Apple Information Security discovered that the
implementation of DBUS_COOKIE_SHA1 was susceptible to a symbolic link
attack: a malicious client with write access to its own home directory
could manipulate a ~/.dbus-keyrings symlink to cause the DBusServer to
read and write in unintended locations. In the worst case this could
result in the DBusServer reusing a cookie that is known to the
malicious client, and treating that cookie as evidence that a subsequent
client connection came from an attacker-chosen uid, allowing
authentication bypass.
This is mitigated by the fact that by default, the well-known system
dbus-daemon (since 2003) and the well-known session dbus-daemon (in
stable releases since dbus 1.10.0 in 2015) only accept the EXTERNAL
authentication mechanism, and as a result will reject DBUS_COOKIE_SHA1
at an early stage, before manipulating cookies. As a result, this
vulnerability only applies to:
* system or session dbus-daemons with non-standard configuration
* third-party dbus-daemon invocations such as at-spi2-core (although
in practice at-spi2-core also only accepts EXTERNAL by default)
* third-party uses of DBusServer such as the one in Upstart
Avoiding symlink attacks in a portable way is difficult, because APIs
like openat() and Linux /proc/self/fd are not universally available.
However, because DBUS_COOKIE_SHA1 already doesn't work in practice for
a non-matching uid, we can solve this vulnerability in an easier way
without regressions, by rejecting it early (before looking at
~/.dbus-keyrings) whenever the requested identity doesn't match the
identity of the process hosting the DBusServer.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Closes: https://gitlab.freedesktop.org/dbus/dbus/issues/269
Closes: CVE-2019-12749
Linux systems have traditionally set the soft limit to 1024 and the hard
limit to 4096. Recent versions of systemd keep the soft fd limit at
1024 to avoid breaking programs that still use select(), but raise the
hard limit to 512*1024, while in recent Debian versions a complicated
interaction between components gives a soft limit of 1024 and a hard
limit of 1024*1024. If we can, we might as well elevate our soft limit
to match the hard limit, minimizing the chance that we will run out of
file descriptor slots.
Unlike the previous code to raise the hard and soft limits to at least
65536, we do this even if we don't have privileges: privileges are
unnecessary to raise the soft limit up to the hard limit.
If we *do* have privileges, we also continue to raise the hard and soft
limits to at least 65536 if they weren't already that high, making
it harder to carry out a denial of service attack on the system bus on
systems that use the traditional limit (CVE-2014-7824).
As was previously the case on the system bus, we'll drop the limits back
to our initial limits before we execute a subprocess for traditional
(non-systemd) activation, if enabled.
systemd activation doesn't involve us starting subprocesses at all,
so in both cases activated services will still inherit the same limits
they did previously.
This change also fixes a bug when the hard limit is very large but
the soft limit is not, for example seen as a regression when upgrading
to systemd >= 240 (Debian #928877). In such environments, dbus-daemon
would previously have changed its fd limit to 64K soft/64K hard. Because
this hard limit is less than its original hard limit, it was unable to
restore its original hard limit as intended when carrying out traditional
activation, leaving activated subprocesses with unintended limits (while
logging a warning).
Reviewed-by: Lennart Poettering <lennart@poettering.net>
[smcv: Correct a comment based on Lennart's review, reword commit message]
Signed-off-by: Simon McVittie <smcv@collabora.com>
(cherry picked from commit 7eacbfece7)
[smcv: Mention that this also fixes Debian #928877]
The CMake config file installed by DBus will run in the context of other
projects. Consequently, changing the value of the PKG_CONFIG_DIR,
PKG_CONFIG_PATH or PKG_CONFIG_LIBDIR environment variables will affect
any further calls to pkg-config made by such projects, which can cause
problems.
A common case of this happening are pkg-config files installed in
usr/share/pkgconfig for .pc files that are architecture-independent, as
for example systemd does.
Avoid clobbering the environment variables by saving and restoring their
values. Note that for some of the variables, setting them to an empty
string is different from not setting them at all.
Signed-off-by: Clemens Lang <clemens.lang@bmw-carit.de>
(cherry picked from commit 3525cc045d)
Closes: dbus#267
MSYS2 has enough of a Unixish environment to run Autotools, but
apparently not enough of a Unixish environment to have functional
permissions.
Closes: dbus#216
(cherry picked from commit 14f46d14a0)
EAGAIN and EWOULDBLOCK are documented to possibly be numerically equal,
for instance in errno(3), and a simple logical OR check will trigger the
-Wlogical-op warning of GCC. The GCC developers consider the warning to
work as-designed in this case:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69602
Avoid such a warning by explicitly checking if the values are identical.
Fixes: https://gitlab.freedesktop.org/dbus/dbus/issues/225
Signed-off-by: David King <dking@redhat.com>
Reviewed-by: Simon McVittie <smcv@collabora.com>
(cherry picked from commit a653191342)
Switch the order of the argument checks to avoid the
-Wduplicated-branches warning.
Signed-off-by: David King <dking@redhat.com>
Reviewed-by: Simon McVittie <smcv@collabora.com>
(cherry picked from commit c0bf0d185d)
Group names in desktop files may contain all ASCII characters, except
control characters and '[' and ']'. Rather than accepting all values,
thanks to a logical operator confusion found by GCC warning
-Wlogical-op, instead explicitly reject the invalid values.
Signed-off-by: David King <dking@redhat.com>
Fixes: https://gitlab.freedesktop.org/dbus/dbus/issues/208
(cherry picked from commit 3ef9e789c1)
AX_CODE_COVERAGE recently changed the way it embedded its Makefile rules
in the output file: instead of using @CODE_COVERAGE_RULES@, users
are now meant to include aminclude_static.am.
The new AX_CODE_COVERAGE is only in the latest autoconf-archive release,
version 2019.01.06, which is inconveniently new, so bundle everything
we need for the moment.
This requires us to stop using the deprecated CODE_COVERAGE_LDFLAGS
(which we still used to support older versions of autoconf-archive)
and replace them with CODE_COVERAGE_LIBS.
Signed-off-by: Simon McVittie <smcv@collabora.com>
(cherry picked from commit 2938c2125e)
Closes: dbus#265
We want to make autoconf fail early and with a user-comprehensible
message if autoconf-archive isn't installed, rather than generating
a configure script with syntax errors, or a configure script that runs
successfully but doesn't do what we intended.
However, autoconf-archive doesn't actually guarantee not to use
AX_-prefixed shell variable names without m4_pattern_allow'ing them
(unlike Autoconf, Automake, Libtool and pkg-config, which explicitly use
m4_pattern_allow for variables with AC_, AM_, LT_ and PKG_ prefixes), so
it isn't safe to assume that they won't be used. In particular, recent
versions of AX_CHECK_GNU_MAKE appear to be using
$AX_CHECK_GNU_MAKE_HEADLINE as a shell variable.
Instead, specifically forbid the names of the finite list of macros
that we actually use.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Resolves: dbus#249
(cherry picked from commit ee09cc0acd)
This gives us a way to build on a more recent host OS if we want to.
For Gitlab-CI it's disabled by default.
Signed-off-by: Simon McVittie <smcv@collabora.com>
(cherry picked from commit 28c27349e2)
The version of gcc in trusty is too old for AddressSanitizer, which we
want to be able to start using, and Travis-CI finally supports Ubuntu
16.04 'xenial' now. This lets us remove some workarounds, but we need
to update others.
Signed-off-by: Simon McVittie <smcv@collabora.com>
(cherry picked from commit 0c553afcd9)
This file hadn't kept up with reality, and needs updating for Gitlab.
Take the opportunity to rewrite it.
Much of the text, particularly about commit messages, was taken from
Wayland's contributing guide (thanks to Ander Conselvan de Oliveira,
Bryce Harrington, Eric Engestrom, Pekka Paalanen and Daniel Stone).
Signed-off-by: Simon McVittie <smcv@collabora.com>
This is technically a denial of service because the dbus-daemon will
run out of memory eventually, but it's a very slow and noisy one,
because all the rejected messages are also very likely to have
been logged to the system log.
Detected by AddressSanitizer.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Resolves: https://gitlab.freedesktop.org/dbus/dbus/issues/234
Reviewed-by: pwithnall
The timeout we're using here is 0.5s (500ms), but the actual time taken
is unbounded, because the OS scheduler might not schedule our process
for an arbitrary length of time after we become runnable.
We previously allowed up to 1 second, but in the CI jobs for dbus!9
and dbus!18 we've seen this take up to 3.4 seconds (presumably
because other tests, or other jobs running on the same shared
infrastructure, starved this process). Allow up to 10 seconds to guard
against spurious failures.
The timeout used in the production system.conf is 150 seconds (2½
minutes), and we're only using the shorter 500ms timeout here to make
the test complete more quickly, so ±10 seconds is relatively
insignificant: the main thing is that it's finite.
Signed-off-by: Simon McVittie <smcv@collabora.com>
(cherry picked from commit 20e6eb7cd1)
Doing a runtime check in configure.ac (AC_RUN_IFELSE) has several
disadvantages:
* It doesn't work when cross-compiling. For example, if we build macOS
binaries on a Linux system, we'd assume that poll() works, but in
fact it won't.
* It checks the build system capabilities, but that is not necessarily
appropriate if (for example) a macOS 10.10 user builds binaries that
could be used by macOS 10.12 or macOS 10.9 users.
* It checks for one specific failure mode, but macOS seems to have a
history of various implementation issues in poll().
* If we want it to work in CMake, we have to duplicate it in the CMake
build system.
None of these is a showstopper on its own, but the combination of all
of them makes the current approach to avoiding the broken poll() on
macOS look unreliable. libcurl, a widely-portable library making
extensive use of sockets, specifically doesn't use poll() on Darwin
(macOS, iOS, etc.) or on Interix; let's follow their example here.
See also https://bugzilla.gnome.org/show_bug.cgi?id=302672 and
https://daniel.haxx.se/blog/2016/10/11/poll-on-mac-10-12-is-broken/
for some relevant history.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Resolves: https://gitlab.freedesktop.org/dbus/dbus/issues/232
(cherry picked from commit 0414ea65ca)
freedesktop.org Gitlab doesn't currently have enough test runners
available to run all of this every time. For higher-risk changes
(for example those that change the build system) we can run the
complete set through the web UI.
Signed-off-by: Simon McVittie <smcv@collabora.com>
(cherry picked from commit a2f416c289)
This uses the same shell scripts as Travis-CI, with slightly different
settings. We use Docker containers for all our Gitlab-CI runs, so take
the opportunity to use Debian 9 'stretch' as our baseline, and
relegate Ubuntu 14.04 'trusty' to to a secondary build.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=108177
Acked-by: Philip Withnall <withnall@endlessm.com>
(cherry picked from commit 60933c09e9)
Travis-CI workers have cmake preinstalled, but Gitlab-CI Docker images
typically don't.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=108177
Acked-by: Philip Withnall <withnall@endlessm.com>
(cherry picked from commit 907832e008)
