This doesn't verify that they're atomic, but does verify that they
return the right things.
This commit adds a new test function _dbus_test_check (a) to make
writing tests easier. It checks the given boolean expression and
generates a "not ok" test result if the expression is false.
Due to the current design of the test api, the test is only compiled
if embedded tests were enabled at the time of configuration.
It was also necessary to move the test_atomic target definitions in
test/Makefile.am to the --enable-embedded-tests section to avoid a
make distcheck build error.
The test case itself has been authored by smcv.
Co-authored-by: Simon McVittie <smcv@collabora.com>
This needs new atomic primitives: we don't have "set to a value",
and in fact that's a bit annoying to implement in terms of gcc
intrinsics. "Set to 0" and "set to nonzero" are easy, though.
Currently, if the "dbus" security class or the associated AV doesn't
exist, dbus-daemon fails to initialize and exits immediately. Also the
security classes or access vector cannot be reordered in the policy.
This can be a problem for people developing their own policy or trying
to access a machine where, for some reasons, there is not policy defined
at all.
The code here copy the behaviour of the selinux_check_access() function.
We cannot use this function here as it doesn't allow us to define the
AVC entry reference.
See the discussion at https://marc.info/?l=selinux&m=152163374332372&w=2
Resolves: https://gitlab.freedesktop.org/dbus/dbus/issues/198
Commit 724adb2f6 mangled the dbus_message_append_args() code example.
This fixes it by breaking the lines and aligning at the right places.
Signed-off-by: Felipe Franciosi <felipe@nutanix.com>
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
Clients listening for a signal can match against the 'sender', expecting
it to come from a connection with a specific name. With this change,
dbus-send can send signals to them.
Instead of exposing _dbus_sha_test() as a private exported symbol,
we can expose _dbus_sha_compute(), which is the only thing called by
the test that isn't already exported.
Signed-off-by: Simon McVittie <smcv@collabora.com>
This lets us expose symbols in the embedded-tests build without
expanding the symbol table of the production library.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Some CI environments run build-time tests as root with CAP_AUDIT_WRITE.
In this case we need to close the audit socket so that it will not be
reported as leaked.
Signed-off-by: Simon McVittie <smcv@collabora.com>
The audit module is initialized every time a new BusContext is created,
which is only once in the real dbus-daemon, but can happen several times
in some unit tests.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Some CI systems do the entire build as uid 0 in a throwaway container.
If this is done in a build directory for which the messagebus user
does not have search (+x) permission, then they will be unable to
execute the just-built dbus-daemon binary.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Some CI systems do the build as root in a disposable container, and
run tests without ever having installed dbus. This means we can't
expect to be able to drop privileges from root to the DBUS_USER (usually
named messagebus or dbus) unless we have checked that the
DBUS_USER exists.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Some of these appear to hang, but making this diagnostic appear in the
log reveals the truth: it's just very slow.
Signed-off-by: Simon McVittie <smcv@collabora.com>
If we retry processing the message in response to OOM, but we don't
clear this buffer first, then the assertion at the beginning will fail.
Signed-off-by: Simon McVittie <smcv@collabora.com>
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
