The
getpeereid()
function returns the effective user and group IDs of the
peer connected to a
Unix Ns -domain
socket.
The argument
s
must be a
Unix Ns -domain
socket
(
unix(4))
of type
SOCK_STREAM
on which either
connect(2)
or
listen(2)
has been called.
The effective user ID is placed in
euid,
and the effective group ID in
egid.
The credentials returned to the
listen(2)
caller are those of its peer at the time it called
connect(2);
the credentials returned to the
connect(2)
caller are those of its peer at the time it called
listen(2).
This mechanism is reliable; there is no way for either side to influence
the credentials returned to its peer except by calling the appropriate
system call (i.e., either
connect(2)
or
listen(2))
under different effective credentials.
One common use of this routine is for a
Unix Ns -domain
server
to verify the credentials of its client.
Likewise, the client can verify the credentials of the server.
