Description¶

These functions return credential information from an sd_bus_creds object. Credential objects may be created with sd_bus_creds_new_from_pid(3), in which case they describe the credentials of the process identified by the specified PID, with sd_bus_get_name_creds(3), in which case they describe the credentials of a bus peer identified by the specified bus name, with sd_bus_get_owner_creds(3), in which case they describe the credentials of the creator of a bus, or with sd_bus_message_get_creds(3), in which case they describe the credentials of the sender of the message.

Not all credential fields are part of every "sd_bus_creds" object. Use sd_bus_creds_get_mask(3) to determine the mask of fields available.

sd_bus_creds_get_pid() will retrieve the PID (process identifier). Similarly, sd_bus_creds_get_ppid() will retrieve the parent PID. Note that PID 1 has no parent process, in which case -ENXIO is returned.

sd_bus_creds_get_tid() will retrieve the TID (thread identifier).

sd_bus_creds_get_uid() will retrieve the numeric UID (user identifier). Similarly, sd_bus_creds_get_euid() returns the effective UID, sd_bus_creds_get_suid() the saved UID and sd_bus_creds_get_fsuid() the file system UID.

sd_bus_creds_get_gid() will retrieve the numeric GID (group identifier). Similarly, sd_bus_creds_get_egid() returns the effective GID, sd_bus_creds_get_sgid() the saved GID and sd_bus_creds_get_fsgid() the file system GID.

sd_bus_creds_get_supplementary_gids() will retrieve the supplementary GIDs list.

sd_bus_creds_get_comm() will retrieve the comm field (truncated name of the executable, as stored in /proc/pid/comm).

sd_bus_creds_get_tid_comm() will retrieve the comm field of the thread (as stored in /proc/pid/task/tid/comm).

sd_bus_creds_get_exe() will retrieve the path to the program executable (as stored in the /proc/pid/exe link, but with the " (deleted)" suffix removed). Note that kernel threads do not have an executable path, in which case -ENXIO is returned. Note that this property should not be used for more than explanatory information, in particular it should not be used for security-relevant decisions. That's because the executable might have been replaced or removed by the time the value can be processed. Moreover, the kernel exports this information in an ambiguous way (i.e. a deleted executable cannot be safely distinguished from one whose name suffix is " (deleted)").

sd_bus_creds_get_cmdline() will retrieve an array of command line arguments (as stored in /proc/pid/cmdline). Note that kernel threads do not have a command line, in which case -ENXIO is returned.

sd_bus_creds_get_cgroup() will retrieve the control group path. See Control Groups v2.

sd_bus_creds_get_unit() will retrieve the systemd unit name (in the system instance of systemd) that the process is a part of. See systemd.unit(5). For processes that are not part of a unit, returns -ENXIO.

sd_bus_creds_get_user_unit() will retrieve the systemd unit name (in the user instance of systemd) that the process is a part of. See systemd.unit(5). For processes that are not part of a user unit, returns -ENXIO.

sd_bus_creds_get_slice() will retrieve the systemd slice (a unit in the system instance of systemd) that the process is a part of. See systemd.slice(5). Similarly, sd_bus_creds_get_user_slice() retrieves the systemd slice of the process, in the user instance of systemd.

sd_bus_creds_get_session() will retrieve the identifier of the login session that the process is a part of. Please note the login session may be limited to a stub process or two. User processes may instead be started from their systemd user manager, e.g. GUI applications started using DBus activation, as well as service processes which are shared between multiple logins of the same user. For processes that are not part of a session, returns -ENXIO.

sd_bus_creds_get_owner_uid() will retrieve the numeric UID (user identifier) of the user who owns the user unit or login session that the process is a part of. See systemd-logind.service(8). For processes that are not part of a user unit or session, returns -ENXIO.

sd_bus_creds_has_effective_cap() will check whether the capability specified by capability was set in the effective capabilities mask. A positive return value means that it was set, zero means that it was not set, and a negative return value indicates an error. See capabilities(7) and the AmbientCapabilities= and CapabilityBoundingSet= settings in systemd.exec(5).

sd_bus_creds_has_permitted_cap() is similar to sd_bus_creds_has_effective_cap(), but will check the permitted capabilities mask.

sd_bus_creds_has_inheritable_cap() is similar to sd_bus_creds_has_effective_cap(), but will check the inheritable capabilities mask.

sd_bus_creds_has_bounding_cap() is similar to sd_bus_creds_has_effective_cap(), but will check the bounding capabilities mask.

sd_bus_creds_get_selinux_context() will retrieve the SELinux security context (label) of the process.

sd_bus_creds_get_audit_session_id() will retrieve the audit session identifier of the process. Returns -ENXIO for processes that are not part of an audit session.

sd_bus_creds_get_audit_login_uid() will retrieve the audit user login identifier (the identifier of the user who is "responsible" for the session). Returns -ENXIO for processes that are not part of an audit session.

sd_bus_creds_get_tty() will retrieve the controlling TTY, without the prefixing "/dev/". Returns -ENXIO for processes that have no controlling TTY.

sd_bus_creds_get_unique_name() will retrieve the D-Bus unique name. See The D-Bus specification.

sd_bus_creds_get_well_known_names() will retrieve the set of D-Bus well-known names. See The D-Bus specification.

sd_bus_creds_get_description() will retrieve a descriptive name of the bus connection of the peer. This name is useful to discern multiple bus connections by the same peer, and may be altered by the peer with the sd_bus_set_description(3) call.

All functions that take a const char** parameter will store the answer there as an address of a NUL-terminated string. It will be valid as long as c remains valid, and should not be freed or modified by the caller.

All functions that take a char*** parameter will store the answer there as an address of an array of strings. Each individual string is NUL-terminated, and the array is NULL-terminated as a whole. It will be valid as long as c remains valid, and should not be freed or modified by the caller.

Return Value¶

On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style error code.

Notes¶

Functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config(1) file.

The code described here uses getenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not call setenv(3) from a parallel thread. It is recommended to only do calls to setenv() from an early phase of the program when no other threads have been started.

See Also¶

systemd(1), sd-bus(3), sd_bus_creds_new_from_pid(2), fork(2), execve(2), credentials(7), free(3), proc(5), systemd.journal-fields(7)