This allows marking messages that contain "sensitive" data with a flag.
If it's set then the messages are erased from memory when the message is
freed.
Similar, a flag may be set on vtable entries: incoming/outgoing message
matching the entry will then automatically be flagged this way.
This is supposed to be an easy method to mark messages containing
potentially sensitive data (such as passwords) for proper destruction.
(Note that this of course is only is as safe as the broker in between is
doing something similar. But let's at least not be the ones at fault
here.)
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.
Before this commit bus messages had a single reference count: when it
reached zero the message would be freed. This simple approach meant a
cyclic dependency was typically seen: a message that was enqueued in a
bus connection object would reference the bus connection object but also
itself be referenced by the bus connection object. So far out strategy
to avoid cases like this was: make sure to process the bus connection
regularly so that messages don#t stay queued, and at exit flush/close
the connection so that the message queued would be emptied, and thus the
cyclic dependencies resolved. Im many cases this isn't done properly
however.
With this change, let's address the issue more systematically: let's
break the reference cycle. Specifically, there are now two types of
references to a bus message:
1. A regular one, which keeps both the message and the bus object it is
associated with pinned.
2. A "queue" reference, which is weaker: it pins the message, but not
the bus object it is associated with.
The idea is then that regular user handling uses regular references, but
when a message is enqueued on its connection, then this takes a "queue"
reference instead. This then means that a queued message doesn't imply
the connection itself remains pinned, only regular references to the
connection or a message associated with it do. Thus, if we end up in the
situation where a user allocates a bus and a message and enqueues the
latter in the former and drops all refs to both, then this will detect
this case and free both.
Note that this scheme isn't perfect, it only covers references between
messages and the busses they are associated with. If OTOH a bus message
is enqueued on a different bus than it is associated with cyclic deps
cannot be recognized with this simple algorithm, and thus if you enqueue
a message associated with a bus A on a bus B, and another message
associated with bus B on a bus A, a cyclic ref will be in effect and not
be discovered. However, given that this is an exotic case (though one
that happens, consider systemd-bus-stdio-bridge), it should be OK not to
cover with this, and people have to explicit flush all queues on exit in
that case.
Note that this commit only establishes the separate reference counters
per message. A follow-up commit will start making use of this from the
bus connection object.
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.
Previously we were a bit sloppy with the index and size types of arrays,
we'd regularly use unsigned. While I don't think this ever resulted in
real issues I think we should be more careful there and follow a
stricter regime: unless there's a strong reason not to use size_t for
array sizes and indexes, size_t it should be. Any allocations we do
ultimately will use size_t anyway, and converting forth and back between
unsigned and size_t will always be a source of problems.
Note that on 32bit machines "unsigned" and "size_t" are equivalent, and
on 64bit machines our arrays shouldn't grow that large anyway, and if
they do we have a problem, however that kind of overly large allocation
we have protections for usually, but for overflows we do not have that
so much, hence let's add it.
So yeah, it's a story of the current code being already "good enough",
but I think some extra type hygiene is better.
This patch tries to be comprehensive, but it probably isn't and I missed
a few cases. But I guess we can cover that later as we notice it. Among
smaller fixes, this changes:
1. strv_length()' return type becomes size_t
2. the unit file changes array size becomes size_t
3. DNS answer and query array sizes become size_t
Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=76745
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.
Some kdbus_flag and memfd related parts are left behind, because they
are entangled with the "legacy" dbus support.
test-bus-benchmark is switched to "manual". It was already broken before
(in the non-kdbus mode) but apparently nobody noticed. Hopefully it can
be fixed later.
There are more than enough calls doing string manipulations to deserve
its own files, hence do something about it.
This patch also sorts the #include blocks of all files that needed to be
updated, according to the sorting suggestions from CODING_STYLE. Since
pretty much every file needs our string manipulation functions this
effectively means that most files have sorted #include blocks now.
Also touches a few unrelated include files.
Previously, sd-bus inofficially already supported bus matches that
tested a string against an array of strings ("as"). This was done via an
enhanced way to interpret "arg0=" matches. This is problematic however,
since clients have no way to determine if their respective
implementation understood strv matches or not, thus allowing invalid
matches to be installed without a way to detect that.
This patch changes the logic to only allow such matches with a new
"arg0has=" syntax. This has the benefit that non-conforming
implementations will return a parse error and a client application may
thus efficiently detect support for the match type.
Matches of this type are useful for "udev"-like systems that "tag" objects
with a number of strings, and clients need to be able to match against
any of these "tags".
The name "has" takes inspiration from Python's ".has_key()" construct.
Include <sys/socket.h> from util.h and bus-message.h in order to
build errors like the ones below on kdbus enabled systems.
./src/shared/util.h:976:32: warning: its scope is only this definition or declaration, which is probably not what you want
In file included from src/libsystemd/sd-bus/bus-kernel.c:37:0:
./src/shared/util.h:1081:28: warning: 'struct msghdr' declared inside parameter list
void cmsg_close_all(struct msghdr *mh);
^
CC src/libsystemd/sd-bus/libsystemd_la-bus-creds.lo
In file included from src/libsystemd/sd-bus/bus-creds.c:25:0:
./src/shared/util.h:976:32: warning: 'struct ucred' declared inside parameter list
int getpeercred(int fd, struct ucred *ucred);
^
This patch removes includes that are not used. The removals were found with
include-what-you-use which checks if any of the symbols from a header is
in use.
Previously, we only minimally altered the dbus1 framing for kdbus, and
while the header and its fields where compliant Gvariant objects, and so
was the body, the entire message together was not.
As result of discussions with Ryan Lortie this is now changed, so that
the messages in there entirely are fully compliant GVariants. This
follows the framing description described here:
https://wiki.gnome.org/Projects/GLib/GDBus/Version2
Note that this change changes the framing of *all* messages sent via
kdbus, this means you have to reboot your kdbus system, after compiling
and installing this new version.
kdbus-git gained two new features:
* memfd offsets: This allows to specify a 'start' offset in kdbus_memfd
so you can send partial memfd hunks instead of always
the full memfd
* KDBUS_HELLO_UNPRIVILEGED: If passed during HELLO, the client will be
treated as unprivileged.
kdbus learned to accept both a numerical destination ID as well as a
well-known-name. In that case, kdbus makes sure that the numerical ID is in
fact the owner of the provided name and fails otherwise.
This allows for race-free assertion of a bus name owner while sending a
message, which is a requirement for bus-proxyd.
Add two new fields to sd_bus_message, and set the numerical ID to
verify_destination_id if bus_message_setup_kmsg() is called for a
message with a well-known name.
Also, set the destination's name in the kdbus item to .destination_ptr
if it is non-NULL.
Normal users should not touch these fields, and they're not publicy
accessible.
This broke hashtable lookups for the message cookies on s390x, which is
a 64bit BE machine where accessing 32bit values as 64bit and vice versa
will explode.
Also, while we are at it, be a bit more careful when dealing with the
64bit cookies we expose and the 32bit serial numbers dbus uses in its
payload.
Problem identified by Fridrich Strba.
