sd_bus_creds_get_well_known_names() fails with -ENODATA in case the
message has no names attached, which is intended behavior if the
remote connection didn't own any names at the time of sending.
The function already deals with 'sender_names' being an empty strv,
so we can just continue in such cases.
Messages to destinations that are not currently owned by any bus connection
will cause kdbus related function to return with either -ENXIO or -ESRCH.
Such conditions should not make the proxyd terminate but send a sane
SD_BUS_ERROR_NAME_HAS_NO_OWNER error reply to the proxied connection.
When dbus client connects to systemd-bus-proxyd through
Unix domain socket proxy takes client's smack label and sets for itself.
It is done before and independent of dropping privileges.
The reason of such soluton is fact that tests of access rights
performed by lsm may take place inside kernel, not only
in userspace of recipient of message.
The bus-proxyd needs CAP_MAC_ADMIN to manipulate its label.
In case of systemd running in system mode, CAP_MAC_ADMIN
should be added to CapabilityBoundingSet in service file of bus-proxyd.
In case of systemd running in user mode ('systemd --user')
it can be achieved by addition
Capabilities=cap_mac_admin=i and SecureBits=keep-caps
to user@.service file
and setting cap_mac_admin+ei on bus-proxyd binary.
The ID returned really doesn't identify the owner, but the bus instance,
hence fix this misnaming.
Also, update "busctl status" to show the ID in its output.
If the format string contains %m, clearly errno must have a meaningful
value, so we might as well use log_*_errno to have ERRNO= logged.
Using:
find . -name '*.[ch]' | xargs sed -r -i -e \
's/log_(debug|info|notice|warning|error|emergency)\((".*%m.*")/log_\1_errno(errno, \2/'
Plus some whitespace, linewrap, and indent adjustments.
As a followup to 086891e5c1 "log: add an "error" parameter to all
low-level logging calls and intrdouce log_error_errno() as log calls
that take error numbers", use sed to convert the simple cases to use
the new macros:
find . -name '*.[ch]' | xargs sed -r -i -e \
's/log_(debug|info|notice|warning|error|emergency)\("(.*)%s"(.*), strerror\(-([a-zA-Z_]+)\)\);/log_\1_errno(-\4, "\2%m"\3);/'
Multi-line log_*() invocations are not covered.
And we also should add log_unit_*_errno().
- actually return permission errors to clients
- use the right ucreds field
- fix error paths when we cannot keep track of locally acquired names
due to OOM
- avoid unnecessary global variables
- log when the policy denies access
- enforce correct policy rule order
- always request all the metadata its we need to make decisions
Also:
- adds support for euid, suid, fsuid, egid, sgid, fsgid fields.
- makes augmentation of creds with data from /proc explicitly
controllable to give apps better control over this, given that this is
racy.
- enables augmentation for kdbus connections (previously we only did it
for dbus1). This is useful since with recent kdbus versions it is
possible for clients to control the metadata they want to send.
- changes sd_bus_query_sender_privilege() to take the euid of the client
into consideration, if known
- when we don't have permissions to read augmentation data from /proc,
don't fail, just don't add the data in
The access check call was broken (as it tried to read a service name
from the UpdateActivationEnvironment() method call which doesn't carry
any). Also, it's unnecessary to make any access checks here, as we just
forward the call to PID 1 which should do the access checks necessary.
There are issues to investigate on with policies shipped by some
packages, which we'll address later. Move that topic out of the
way for now to bring sd-bus in sync with upstream kdbus.
In order to check for matching policy entries at message transfers, we
have to consider the following:
* check the currently owned names of both the sending and the receiving
peer. If the sending peer is connected via kdbus, the currently owned
names are already attached to the message. If it was originated by the
connection we're proxying for, we store the owned names in our own strv
so we can check against them.
* Walk the list of names to check which name would allow the message to
pass, and explicitly use that name as destination of the message. If the
destination is on kdbus, store both the connection's unique name and the
chosen well-known-name in the message. That way, the kernel will make sure
the supplied name is owned by the supplied unique name, at the time of
sending, and return -EREMCHG otherwise.
* Make the policy checks optional by retrieving the bus owner creds, and
when the uid matches the current user's uid and is non-null, don't check
the bus policy.
We need to figure out which of the possible names satisfied the policy,
so we cannot do the iteration in check_policy_item() but have to leave it
to the users.
Test cases amended accordingly.
In kdbus a "server id" is mostly a misnomer, as there isn't any "server"
involved anymore. Let's rename this to "owner" id hence, since it is an
ID that is picked by the owner of a bus or direct connection. This
matches nicely the sd_bus_get_owner_creds() call we already have.
Catch up with some changes in kdbus.h:
* KDBUS_{ITEM,ATTACH}_CONN_NAME were renamed to
KDBUS_{ITEM,ATTACH}_CONN_DESCRIPTION, so the term 'name' is not
overloaded as much.
* The item types were re-ordered a little so they are lined up to the
order of the corresponding KDBUS_ATTACH flags
* A new item type KDBUS_ITEM_OWNED_NAME was introduced, designated to
store a struct kdbus_name in item->name. KDBUS_ITEM_NAME soley
stores data in item->str now
* Some kerneldoc fixes
We should use the data if we can (if stdin/stdout is an AF_UNIX socket),
but still work if we can't (if stdin/stdout are pipes, like in the SSH
case).
This effectively reverts 55534fb5e4
Clean up the function namespace by renaming the following:
sd_bus_get_owner_uid() → sd_bus_get_name_creds_uid()
sd_bus_get_owner_machine_id() → sd_bus_get_name_machine_id()
sd_bus_get_peer_creds() → sd_bus_get_owner_creds()
In kdbus.h, the following details changed:
* All commands gained a 'kernel_flags' field to report the flags supported
by the driver. Before, this was done in the 'flags' field in a
bidirectional way, which turned out to be a problem for the code in
sd-bus, as many parts of it reuse the same ioctl struct more than once
and consider them to be owned by userspace.
* Name listings are now returned by a new struct instead of reusing struct
kdbus_cmd_name for that matter. This way, we don't add more unneeded
fields to it and make the API cleaner.
* 'conn_flags' was renamed to 'flags' in struct kdbus_cmd_hello to make
the API a bit more unified.
'GetConnectionUnixProcessID', 'GetConnectionUnixUser' and
'GetConnectionSELinuxSecurityContext' methods should return
'NameHasNoOwner' error (if chosen name is not available on bus)
with more detailed description - like dbus-1:
Could not get PID of name 'org.freedesktop.test': no such name.
Could not get UID of name 'org.freedesktop.test': no such name.
Could not get security context of name 'org.freedesktop.test': no such name.
Otherwise we have only laconic message without proper dbus error:
Error System.Error.ENXIO: No such device or address
The KDBUS_CMD_FREE ioctl now uses a struct rather than a direct pointer
to the offset to free.
The KDBUS_CMD_MSG_CANCEL ioctl has also changes, but there's no user of
it yet in systemd.
In pty.c there was both an include of our pty.h and the system installed pty.h.
The latter contains only two functions openpty and forkpty. We use neither so
I assume it was a typo and removed it. We still compile and pass all tests.
The kdbus logic name registry logic was changed to transport the actual
name to acquire, release or report in a kdbus item.
This brings the name API a little more in line with other calls, and allows
for later augmentation.
Follow that change on the systemd side.
Veres Lajos