sd_bus_query_sender_creds, sd_bus_query_sender_privilege - Query bus message sender credentials/privileges
int sd_bus_query_sender_creds(sd_bus_message *m, uint64_t mask, sd_bus_creds **creds);
sd_bus_error* sd_bus_query_sender_privilege(sd_bus_message *m, int capability);
sd_bus_query_sender_creds() returns the credentials of the message m. The mask parameter is a combo of SD_BUS_CREDS_* flags that indicate which credential info the caller is interested in. See sd_bus_creds_new_from_pid(3) for a list of possible flags. First, this message checks if the requested credentials are attached to the message itself. If not, but the message contains the pid of the sender and the caller specified the SD_BUS_CREDS_AUGMENT flag, this function tries to figure out the missing credentials via other means (starting from the pid). If the pid isn't available but the message has a sender, this function calls sd_bus_get_name_creds(3) to get the requested credentials. If the message has no sender (when a direct connection is used), this function calls sd_bus_get_owner_creds(3) to get the requested credentials. On success, the requested credentials are stored in creds. Ownership of the credentials object in creds is transferred to the caller and should be freed by calling sd_bus_creds_unref(3).
sd_bus_query_sender_privilege() checks if the message m has the requested privileges. If capability is a non-negative integer, this function checks if the message has the capability with the same value. See capabilities(7) for a list of capabilities. If capability is a negative integer, this function returns whether the sender of the message runs as the same user as the receiver of the message, or if the sender of the message runs as root and the receiver of the message does not run as root. On success and if the message has the requested privileges, this function returns a positive integer. If the message does not have the requested privileges, this function returns zero.
On success, these functions return a non-negative integer. On failure, they return a negative errno-style error code.
Returned errors may indicate the following problems:
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.