FreeBSD Man Pages

getpeereid(3)

NAME

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

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <sys/types.h>
     #include <unistd.h>

     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 mech-
     anism is reliable; there is no way for either side to influence the cre-
     dentials 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 creden-
     tials 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)

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