SD_BUS_CREDS_NEW_FROM_PID(3)

NAME
sd_bus_creds_new_from_pid, sd_bus_creds_get_mask, sd_bus_creds_get_augmented_mask, sd_bus_creds_ref, sd_bus_creds_unref, sd_bus_creds_unrefp - Retrieve credentials object for the specified PID

SYNOPSIS

#include <systemd/sd-bus.h>

int sd_bus_creds_new_from_pid(pid_t pid, uint64_t creds_mask, sd_bus_creds **ret);

uint64_t sd_bus_creds_get_mask(sd_bus_creds *c);

uint64_t sd_bus_creds_get_augmented_mask(sd_bus_creds *c);

sd_bus_creds *sd_bus_creds_ref(sd_bus_creds *c);

sd_bus_creds *sd_bus_creds_unref(sd_bus_creds *c);

void sd_bus_creds_unrefp(sd_bus_creds **c);

SD_BUS_CREDS_PID, SD_BUS_CREDS_PPID, SD_BUS_CREDS_TID, SD_BUS_CREDS_UID, SD_BUS_CREDS_EUID, SD_BUS_CREDS_SUID, SD_BUS_CREDS_FSUID, SD_BUS_CREDS_GID, SD_BUS_CREDS_EGID, SD_BUS_CREDS_SGID, SD_BUS_CREDS_FSGID, SD_BUS_CREDS_SUPPLEMENTARY_GIDS, SD_BUS_CREDS_COMM, SD_BUS_CREDS_TID_COMM, SD_BUS_CREDS_EXE, SD_BUS_CREDS_CMDLINE, SD_BUS_CREDS_CGROUP, SD_BUS_CREDS_UNIT, SD_BUS_CREDS_SLICE, SD_BUS_CREDS_USER_UNIT, SD_BUS_CREDS_USER_SLICE, SD_BUS_CREDS_SESSION, SD_BUS_CREDS_OWNER_UID, SD_BUS_CREDS_EFFECTIVE_CAPS, SD_BUS_CREDS_PERMITTED_CAPS, SD_BUS_CREDS_INHERITABLE_CAPS, SD_BUS_CREDS_BOUNDING_CAPS, SD_BUS_CREDS_SELINUX_CONTEXT, SD_BUS_CREDS_AUDIT_SESSION_ID, SD_BUS_CREDS_AUDIT_LOGIN_UID, SD_BUS_CREDS_TTY, SD_BUS_CREDS_UNIQUE_NAME, SD_BUS_CREDS_WELL_KNOWN_NAMES, SD_BUS_CREDS_DESCRIPTION, SD_BUS_CREDS_AUGMENT, _SD_BUS_CREDS_ALL

DESCRIPTION

sd_bus_creds_new_from_pid() creates a new credentials object and fills it with information about the process pid. The pointer to this object will be stored in the ret pointer. Note that credential objects may also be created and retrieved via sd_bus_get_name_creds(3), sd_bus_get_owner_creds(3) and sd_bus_message_get_creds(3).

The information that will be stored is determined by creds_mask. It may contain a subset of ORed constants SD_BUS_CREDS_PID, SD_BUS_CREDS_PPID, SD_BUS_CREDS_TID, SD_BUS_CREDS_UID, SD_BUS_CREDS_EUID, SD_BUS_CREDS_SUID, SD_BUS_CREDS_FSUID, SD_BUS_CREDS_GID, SD_BUS_CREDS_EGID, SD_BUS_CREDS_SGID, SD_BUS_CREDS_FSGID, SD_BUS_CREDS_SUPPLEMENTARY_GIDS, SD_BUS_CREDS_COMM, SD_BUS_CREDS_TID_COMM, SD_BUS_CREDS_EXE, SD_BUS_CREDS_CMDLINE, SD_BUS_CREDS_CGROUP, SD_BUS_CREDS_UNIT, SD_BUS_CREDS_SLICE, SD_BUS_CREDS_USER_UNIT, SD_BUS_CREDS_USER_SLICE, SD_BUS_CREDS_SESSION, SD_BUS_CREDS_OWNER_UID, SD_BUS_CREDS_EFFECTIVE_CAPS, SD_BUS_CREDS_PERMITTED_CAPS, SD_BUS_CREDS_INHERITABLE_CAPS, SD_BUS_CREDS_BOUNDING_CAPS, SD_BUS_CREDS_SELINUX_CONTEXT, SD_BUS_CREDS_AUDIT_SESSION_ID, SD_BUS_CREDS_AUDIT_LOGIN_UID, SD_BUS_CREDS_TTY, SD_BUS_CREDS_UNIQUE_NAME, SD_BUS_CREDS_WELL_KNOWN_NAMES, and SD_BUS_CREDS_DESCRIPTION. Use the special value _SD_BUS_CREDS_ALL to request all supported fields. The SD_BUS_CREDS_AUGMENT constant may not be ORed into the mask for invocations of sd_bus_creds_new_from_pid().

Fields can be retrieved from the credentials object using sd_bus_creds_get_pid(3) and other functions which correspond directly to the constants listed above.

A mask of fields which were actually successfully retrieved can be retrieved with sd_bus_creds_get_mask(). If the credentials object was created with sd_bus_creds_new_from_pid(), this will be a subset of fields requested in creds_mask.

Similar to sd_bus_creds_get_mask(), the function sd_bus_creds_get_augmented_mask() returns a bitmask of field constants. The mask indicates which credential fields have been retrieved in a non-atomic fashion. For credential objects created via sd_bus_creds_new_from_pid(), this mask will be identical to the mask returned by sd_bus_creds_get_mask(). However, for credential objects retrieved via sd_bus_get_name_creds(), this mask will be set for the credential fields that could not be determined atomically at peer connection time, and which were later added by reading augmenting credential data from /proc/. Similarly, for credential objects retrieved via sd_bus_get_owner_creds(), the mask is set for the fields that could not be determined atomically at bus creation time, but have been augmented. Similarly, for credential objects retrieved via sd_bus_message_get_creds(), the mask is set for the fields that could not be determined atomically at message sending time, but have been augmented. The mask returned by sd_bus_creds_get_augmented_mask() is always a subset of (or identical to) the mask returned by sd_bus_creds_get_mask() for the same object. The latter call hence returns all credential fields available in the credential object, the former then marks the subset of those that have been augmented. Note that augmented fields are unsuitable for authorization decisions, as they may be retrieved at different times, thus being subject to races. Hence, augmented fields should be used exclusively for informational purposes.

sd_bus_creds_ref() creates a new reference to the credentials object c. This object will not be destroyed until sd_bus_creds_unref() has been called as many times plus once more. Once the reference count has dropped to zero, c cannot be used anymore, so further calls to sd_bus_creds_ref(c) or sd_bus_creds_unref(c) are illegal.

sd_bus_creds_unref() destroys a reference to c.

sd_bus_creds_unrefp() is similar to sd_bus_creds_unref() but takes a pointer to a pointer to an sd_bus_creds object. This call is useful in conjunction with GCC's and LLVM's Clean-up Variable Attribute[1]. Note that this function is defined as inline function.

sd_bus_creds_ref(), sd_bus_creds_unref() and sd_bus_creds_unrefp() execute no operation if the passed in bus credentials object is NULL.

RETURN VALUE

On success, sd_bus_creds_new_from_pid() returns 0 or a positive integer. On failure, it returns a negative errno-style error code.

sd_bus_creds_get_mask() returns the mask of successfully acquired fields.

sd_bus_creds_get_augmented_mask() returns the mask of fields that have been augmented from data in /proc/, and are thus not suitable for authorization decisions.

sd_bus_creds_ref() always returns the argument.

sd_bus_creds_unref() always returns NULL.

REFERENCE OWNERSHIP

Function sd_bus_creds_new_from_pid() creates a new object and the caller owns the sole reference. When not needed anymore, this reference should be destroyed with sd_bus_creds_unref(3).

  Errors

Returned errors may indicate the following problems:

-ESRCH
    Specified pid could not be found.

-EINVAL
    Specified parameter is invalid (NULL in case of output parameters).

-ENOMEM
    Memory allocation failed.

-EOPNOTSUPP
    One of the requested fields is unknown to the local system.

NOTES

These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd pkg-config(1) file.

SEE ALSO

systemd(1), sd-bus(3), sd_bus_creds_get_pid(3), sd_bus_get_name_creds(3), sd_bus_get_owner_creds(3), sd_bus_message_get_creds(3)

NOTES

1.  Clean-up Variable Attribute
    https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html