NAME

     getpeereid — get the effective credentials of a UNIX-domain peer

LIBRARY

     Utility functions from BSD systems (libbsd, -lbsd)

SYNOPSIS

     #include <sys/types.h>
     #include <unistd.h>
     (See libbsd(7) for include usage.)

     int
     getpeereid(int s, uid_t *euid, gid_t *egid);

DESCRIPTION

     The getpeereid() function returns the effective user and group IDs of the peer connected to
     a UNIX-domain socket.  The argument s must be a UNIX-domain socket (unix(4)) of type
     SOCK_STREAM on which either connect(2) or listen(2) have been called.  The effective used 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-domain server to verify the credentials of its
     client.  Likewise, the client can verify the credentials of the server.

IMPLEMENTATION NOTES

     On FreeBSD, getpeereid() is implemented in terms of the LOCAL_PEERCRED unix(4) socket
     option.

RETURN VALUES

     The getpeereid() function returns the value 0 if successful; otherwise the value -1 is
     returned and the global variable errno is set to indicate the error.

ERRORS

     The getpeereid() function fails if:

     [EBADF]            The argument s is not a valid descriptor.

     [ENOTSOCK]         The argument s is a file, not a socket.

     [ENOTCONN]         The argument s does not refer to a socket on which connect(2) or
                        listen(2) have been called.

     [EINVAL]           The argument s does not refer to a socket of type SOCK_STREAM, or the
                        kernel returned invalid data.

SEE ALSO

     connect(2), getpeername(2), getsockname(2), getsockopt(2), listen(2), unix(4)

HISTORY

     The getpeereid() function appeared in FreeBSD 4.6, NetBSD 5.0 and OpenBSD 3.0.