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.

Debian                                            July 15, 2001                                 GETPEEREID(3bsd)