A pass over the whole branch before merge, mostly in libink since
that is the new code and the part exposed to the wire. Grouped here
rather than scattered so the review is easy to read in one place.
libink parser and dispatch:
- Bound reader lengths so a 32-bit size_t can't wrap a wire length
past the guard and read out of bounds. Reachable pre-auth on any
bus, so it matters on the 32-bit targets Finit runs on.
- Drop a peer when a reply send fails instead of limping on with a
half-written frame; a built-in whose send failed used to fall
through and put a second frame on the wire.
initctl:
- Copy a D-Bus error name out of the reply before closing the client;
the reply points into memory the close frees. Both error paths now
share one helper so this can't creep back.
Authorization:
- Take the caller's groups from the kernel (SO_PEERCRED plus
SO_PEERGROUPS) rather than getpwuid()/getgrouplist(), which go
through NSS and can block PID 1 on a slow LDAP or SSSD backend.
The check is now a lookup against the group resolved once at init,
with no NSS and no 256 KiB array on the stack. A caller reaching
us through a broker carries no group set, so system-bus privileged
methods are root-only; the local bus keeps group support. See
libink/README.md for the note on lifting that.
Shutdown:
- Call dbus_exit() from the shutdown path so the server, its peers,
and the socket are let go cleanly. The teardown existed but nobody
called it.
Tests, CI, docs:
- A fuzz target for the message parser, run as a quick sweep in the
suite and properly under libFuzzer in CI, with the corpus carried
between runs. The -as-uid tests drop groups the way a login does
so SO_PEERGROUPS sees the right set, and widen the test socket to
reach the per-method check behind the 0660 gate. Bring the GitHub
actions up to versions that run on Node 24, and tidy a few small
things a /simplify pass turned up.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
On the local bus SO_PEERCRED says who is calling and the kernel is the
one saying it. Behind a broker one connection carries every caller,
so that credential describes dbus-daemon and nothing else, and every
privileged method was refused there, root included.
Ask the bus driver instead. libink parks the call and hands us the
sender; we ask GetConnectionUnixUser and answer when the reply lands,
through the same event loop as everything else. Nothing blocks:
blocking in PID 1 is why libuEv exists. That needs calls libink can
make on a connection it already has, so it gained those too.
Answers are cached, since a bus never reuses a unique name while it
runs. Not across a restart though: a new dbus-daemon numbers from
scratch and :1.7 becomes somebody else, so the cache goes when the
broker does. A sender name too long to key on is refused rather than
truncated, two callers sharing a truncated key would share an
identity.
Privilege is no longer uid 0 alone. The socket is already owned by
the --with-group group, so refusing its members every method that
changes anything left a wheel user able to open the bus and unable to
reboot. Both gates now say the same thing.
Group membership needs NSS, which the C library loads with dlopen(),
so the lookup is compiled out where Finit is built to link statically.
That leaves such a build root-only, which is worth saying out loud
rather than leaving to be discovered.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
libink was written against the only bus it had, its own, where the
peer on the other end is the client. A broker is not: it routes for
senders it names itself, expects a DESTINATION on anything addressed
through it, and answers on its own schedule rather than next.
Runlevels go on the wire as S and N rather than the digits Finit
keeps internally, since that is what a caller outside Finit means by
one.
The library stays a convenience library, linked into finit and
initctl and installed nowhere: the ABI promise waits until libink is
its own project.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
Runlevel and version are state, not actions, so they belong behind
org.freedesktop.DBus.Properties rather than another method each.
Finit also claims org.finit on the system bus when it finds one, so
ordinary D-Bus clients can reach it without knowing about
/run/finit/bus. Opportunistic on purpose: no dbus-daemon is a normal
state for the systems Finit runs on, not an error to report.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
Finit had no way to answer the question every service manager gets
asked: what is running, and change it. D-Bus is how the rest of
userspace asks, but linking libdbus, sd-bus or GIO into PID 1 buys a
dependency, an allocator and a main loop we do not control.
So libink: the wire format, an object tree, and a bus of Finit's own
at /run/finit/bus, gated like INIT_SOCKET. It speaks the standard
org.freedesktop.DBus, .Peer, .Introspectable interfaces, and Finit's
own Manager1, Service1 and Cond1 on top. Methods that change
something are marked privileged and answered only for a caller the
kernel vouched for, via SO_PEERCRED.
Server and client both, since initctl is the first thing that needs
to talk to it, and its Start/Stop/Restart/Reload now go over the bus
rather than the legacy socket.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
Joachim Wiberg