let's make sure we collect the right error code from errno, otherwise
we'll see EPERM (i.e. error 1) for all errors readv() returns (since it
returns -1 on error), including EAGAIN.
This is definitely backport material.
A fix-up for 3691bcf3c5.
Fixes: #16699
Prompted by the discussion on #16110, let's migrate more code to
fd_wait_for_event().
This only leaves 7 places where we call into poll()/poll() directly in
our entire codebase. (one of which is fd_wait_for_event() itself)
poll() sets POLLNVAL inside of the poll structures if an invalid fd is
passed. So far we generally didn't check for that, thus not taking
notice of the error. Given that this specific kind of error is generally
indication of a programming error, and given that our code is embedded
into our projects via NSS or because people link against our library,
let's explicitly check for this and convert it to EBADF.
(I ran into a busy loop because of this missing check when some of my
test code accidentally closed an fd it shouldn't close, so this is a
real thing)
We always need to make them unions with a "struct cmsghdr" in them, so
that things properly aligned. Otherwise we might end up at an unaligned
address and the counting goes all wrong, possibly making the kernel
refuse our buffers.
Also, let's make sure we initialize the control buffers to zero when
sending, but leave them uninitialized when reading.
Both the alignment and the initialization thing is mentioned in the
cmsg(3) man page.
We need to use the CMSG_SPACE() macro to size the control buffers, not
CMSG_LEN(). The former is rounded up to next alignment boundary, the
latter is not. The former should be used for allocations, the latter for
encoding how much of it is actually initialized. See cmsg(3) man page
for details about this.
Given how confusing this is, I guess we don't have to be too ashamed
here, in most cases we actually did get this right.
Let's be extra careful whenever we return from recvmsg() and see
MSG_CTRUNC set. This generally means we ran into a programming error, as
we didn't size the control buffer large enough. It's an error condition
we should at least log about, or propagate up. Hence do that.
This is particularly important when receiving fds, since for those the
control data can be of any size. In particular on stream sockets that's
nasty, because if we miss an fd because of control data truncation we
cannot recover, we might not even realize that we are one off.
(Also, when failing early, if there's any chance the socket might be
AF_UNIX let's close all received fds, all the time. We got this right
most of the time, but there were a few cases missing. God, UNIX is hard
to use)
Let's count incoming messages and attach the current counter when we
first read them to the message objects. This allows us to nicely order
messages later on.
Introduced in 6d586a1371.
Reported by Felix Riemann in https://bugzilla.redhat.com/show_bug.cgi?id=1685286.
Reproducer:
for i in `seq 1 100`; do gdbus call --session -d org.freedesktop.systemd1 -m org.freedesktop.systemd1.Manager.StartUnit -o "/$(for x in `seq 0 28000`; do echo -n $x; done)" & done
The dbus external authentication takes as optional argument the UID the
sender wants to authenticate as. This uid is purely optional. The
AF_UNIX socket already conveys the same information through the
auxiliary socket data, so we really don't have to provide that
information.
Unfortunately, there is no way to send empty arguments, since they are
interpreted as "missing argument", which has a different meaning. The
SASL negotiation thus changes from:
AUTH EXTERNAL <uid>
NEGOTIATE_UNIX_FD (optional)
BEGIN
to:
AUTH EXTERNAL
DATA
NEGOTIATE_UNIX_FD (optional)
BEGIN
And thus the replies we expect as a client change from:
OK <server-id>
AGREE_UNIX_FD (optional)
to:
DATA
OK <server-id>
AGREE_UNIX_FD (optional)
Since the old sd-bus server implementation used the wrong reply for
"AUTH" requests that do not carry the arguments inlined, we decided to
make sd-bus clients accept this as well. Hence, sd-bus now allows
"OK <server-id>\r\n" replies instead of "DATA\r\n" replies.
Signed-off-by: David Rheinsberg <david.rheinsberg@gmail.com>
The correct way to reply to "AUTH <protocol>" without any payload is to
send "DATA" rather than "OK". The "DATA" reply triggers the client to
respond with the requested payload.
In fact, adding the data as hex-encoded argument like
"AUTH <protocol> <hex-data>" is an optimization that skips the "DATA"
roundtrip. The standard way to perform an authentication is to send the
"DATA" line.
This commit fixes sd-bus to properly send the "DATA" line. Surprisingly
no existing implementation depends on this, as they all pass the data
directly as argument to "AUTH". This will not work if we want to pass
an empty argument, though.
Signed-off-by: David Rheinsberg <david.rheinsberg@gmail.com>
dbus-daemon might have a slightly different idea of what a valid msg is
than us (for example regarding valid msg and field sizes). Let's hence
try to proceed if we can and thus drop messages rather than fail the
connection if we fail to validate a message.
Hopefully the differences in what is considered valid are not visible
for real-life usecases, but are specific to exploit attempts only.
Whenever we invoke external, foreign code from code that has
RLIMIT_NOFILE's soft limit bumped to high values, revert it to 1024
first. This is a safety precaution for compatibility with programs using
select() which cannot operate with fds > 1024.
This commit adds the call to rlimit_nofile_safe() to all invocations of
exec{v,ve,l}() and friends that either are in code that we know runs
with RLIMIT_NOFILE bumped up (which is PID 1 and all journal code for
starters) or that is part of shared code that might end up there.
The calls are placed as early as we can in processes invoking a flavour
of execve(), but after the last time we do fd manipulations, so that we
can still take benefit of the high fd limits for that.
The switch to memory_startswith() changed the logic to only look for a space or
NUL byte after the matched word, but matching the full size should also be
acceptable.
This changed the behavior of parsing of "AUTH\r\n", where m will be set to 4,
since even though the word will match, the check for it being followed by ' '
or NUL will make line_begins() return false.
Tested:
- Using netcat to connect to the private socket directly:
$ echo -ne '\0AUTH\r\n' | sudo nc -U /run/systemd/private
REJECTED EXTERNAL ANONYMOUS
- Running the Ignition blackbox test:
$ sudo sh -c 'PATH=$PWD/bin/amd64:$PATH ./tests.test'
PASS
Fixes: d27b725abf
These lines are generally out-of-date, incomplete and unnecessary. With
SPDX and git repository much more accurate and fine grained information
about licensing and authorship is available, hence let's drop the
per-file copyright notice. Of course, removing copyright lines of others
is problematic, hence this commit only removes my own lines and leaves
all others untouched. It might be nicer if sooner or later those could
go away too, making git the only and accurate source of authorship
information.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
This adds some paranoia code that moves some of the fds we allocate for
longer periods of times to fds > 2 if they are allocated below this
boundary. This is a paranoid safety thing, in order to avoid that
external code might end up erroneously use our fds under the assumption
they were valid stdin/stdout/stderr. Think: some app closes
stdin/stdout/stderr and then invokes 'fprintf(stderr, …' which causes
writes on our fds.
This both adds the helper to do the moving as well as ports over a
number of users to this new logic. Since we don't want to litter all our
code with invocations of this I tried to strictly focus on fds we keep
open for long periods of times only and only in code that is frequently
loaded into foreign programs (under the assumptions that in our own
codebase we are smart enough to always keep stdin/stdout/stderr
allocated to avoid this pitfall). Specifically this means all code used
by NSS and our sd-xyz API:
1. our logging APIs
2. sd-event
3. sd-bus
4. sd-resolve
5. sd-netlink
This changed was inspired by this:
https://github.com/systemd/systemd/issues/8075#issuecomment-363689755
This shows that apparently IRL there are programs that do close
stdin/stdout/stderr, and we should accomodate for that.
Note that this won't fix any bugs, this just makes sure that buggy
programs are less likely to interfere with out own code.
we still invoke ssh unnecessarily when there in incompatible or erreneous input
The fallow-up to finish that would make the code a bit more verbose,
as it would require repeating this bit:
```
r = bus_connect_transport(arg_transport, arg_host, false, &bus);
if (r < 0) {
log_error_errno(r, "Failed to create bus connection: %m");
goto finish;
}
sd_bus_set_allow_interactive_authorization(bus, arg_ask_password);
```
in every verb, after parsing.
v2: add waitpid() to avoid a zombie process, switch to SIGTERM from SIGKILL
v3: refactor, wait in bus_start_address()
log.h really should only include the bare minimum of other headers, as
it is really pulled into pretty much everything else and already in
itself one of the most basic pieces of code we have.
Let's hence drop inclusion of:
1. sd-id128.h because it's entirely unneeded in current log.h
2. errno.h, dito.
3. sys/signalfd.h which we can replace by a simple struct forward
declaration
4. process-util.h which was needed for getpid_cached() which we now hide
in a funciton log_emergency_level() instead, which nicely abstracts
the details away.
5. sys/socket.h which was needed for struct iovec, but a simple struct
forward declaration suffices for that too.
Ultimately this actually makes our source tree larger (since users of
the functionality above must now include it themselves, log.h won't do
that for them), but I think it helps to untangle our web of includes a
tiny bit.
(Background: I'd like to isolate the generic bits of src/basic/ enough
so that we can do a git submodule import into casync for it)
This adds a "watch-bind" feature to sd-bus connections. If set and the
AF_UNIX socket we are connecting to doesn't exist yet, we'll establish
an inotify watch instead, and wait for the socket to appear. In other
words, a missing AF_UNIX just makes connecting slower.
This is useful for daemons such as networkd or resolved that shall be
able to run during early-boot, before dbus-daemon is up, and want to
connect to dbus-daemon as soon as it becomes ready.
This adds a new safe_fork() wrapper around fork() and makes use of it
everywhere. The new wrapper does a couple of things we previously did
manually and separately in a safer, more correct and automatic way:
1. Optionally resets signal handlers/mask in the child
2. Sets a name on all processes we fork off right after forking off (and
the patch assigns useful names for all processes we fork off now,
following a systematic naming scheme: always enclosed in () – in order
to indicate that these are not proper, exec()ed processes, but only
forked off children, and if the process is long-running with only our
own code, without execve()'ing something else, it gets am "sd-" prefix.)
3. Optionally closes all file descriptors in the child
4. Optionally sets a PR_SET_DEATHSIG to SIGTERM in the child, in a safe
way so that the parent dying before this happens being handled
safely.
5. Optionally reopens the logs
6. Optionally connects stdin/stdout/stderr to /dev/null
7. Debug logs about the forked off processes.
Quoting Lennart Poettering in
https://github.com/systemd/systemd/pull/6464#issuecomment-319029293:
> If the kernel allows us to query that data we should also be Ok with passing
> it on to our own caller, regardless if selinux is technically on or off...
The advantage is that this allows gcc to be smarter and reduce linkage:
(before)$ ldd build/libnss_systemd.so.2
linux-vdso.so.1 (0x00007ffeb46ff000)
librt.so.1 => /lib64/librt.so.1 (0x00007f2f60da6000)
libcap.so.2 => /lib64/libcap.so.2 (0x00007f2f60ba1000)
libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f2f60978000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f2f60759000)
libc.so.6 => /lib64/libc.so.6 (0x00007f2f60374000)
/lib64/ld-linux-x86-64.so.2 (0x00007f2f61294000)
libpcre2-8.so.0 => /lib64/libpcre2-8.so.0 (0x00007f2f600f0000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007f2f5feec000)
(after )$ ldd build/libnss_systemd.so.2
linux-vdso.so.1 (0x00007ffe5f543000)
librt.so.1 => /lib64/librt.so.1 (0x00007f427dcaa000)
libcap.so.2 => /lib64/libcap.so.2 (0x00007f427daa5000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f427d886000)
libc.so.6 => /lib64/libc.so.6 (0x00007f427d4a1000)
/lib64/ld-linux-x86-64.so.2 (0x00007f427e196000)
Note that this only works in conjuction with the previous commit: either
of the two commits alone does not have the desired effect on linkage.
Replaces #6464.
As it turns out the authentication phase times out too often than is
good, mostly due to PRNG pools not being populated during boot. Hence,
let's increase the authentication timeout from 25s to 90s, to cover for
that.
(Note that we leave the D-Bus method call timeout at 25s, matching the
reference implementation's value. And if the auth phase managed to
complete then the pools should be populated enough and mehtod calls
shouldn't take needlessly long anymore).
Fixes: #6418
If a message is too large to fit into the output buffer, it will be
transmitted to the kernel in several chunks. However, the FDs must
only ever be transmitted once or they will bereceived by the remote
end repeatedly.
The D-Bus specification disallows several sets of FDs attached to
one message, however, the reference implementation of D-Bus will
not reject such a message, rather it will reassign the duplicate
FDs to subsequent FD-carrying messages.
This attaches the FD array only to the first byte of the message.