getpeereid(3) [debian man page]

GETPEEREID(3)						   BSD Library Functions Manual 					     GETPEEREID(3)

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 <bsd/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 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 cre-
     dentials 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 indi-
     cate 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.

BSD
								   July 15, 2001							       BSD

UNIX(4) 						   BSD Kernel Interfaces Manual 						   UNIX(4)

NAME

     unix -- UNIX-domain protocol family

SYNOPSIS

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

DESCRIPTION

     The UNIX-domain protocol family is a collection of protocols that provides local (on-machine) interprocess communication through the normal
     socket(2) mechanisms.  The UNIX-domain family supports the SOCK_STREAM and SOCK_DGRAM socket types and uses filesystem pathnames for address-
     ing.

ADDRESSING

     UNIX-domain addresses are variable-length filesystem pathnames of at most 104 characters.	The include file <sys/un.h> defines this address:

	   struct sockaddr_un {
		   u_char  sun_len;
		   u_char  sun_family;
		   char    sun_path[104];
	   };

     Binding a name to a UNIX-domain socket with bind(2) causes a socket file to be created in the filesystem.	This file is not removed when the
     socket is closed--unlink(2) must be used to remove the file.

     The UNIX-domain protocol family does not support broadcast addressing or any form of ``wildcard'' matching on incoming messages.  All
     addresses are absolute- or relative-pathnames of other UNIX-domain sockets.  Normal filesystem access-control mechanisms are also applied
     when referencing pathnames; e.g., the destination of a connect(2) or sendto(2) must be writable.

PROTOCOLS

     The UNIX-domain protocol family is comprised of simple transport protocols that support the SOCK_STREAM and SOCK_DGRAM abstractions.
     SOCK_STREAM sockets also support the communication of UNIX file descriptors through the use of the msg_control field in the msg argument to
     sendmsg(2) and recvmsg(2).

     Any valid descriptor may be sent in a message.  The file descriptor(s) to be passed are described using a struct cmsghdr that is defined in
     the include file <sys/socket.h>.  The type of the message is SCM_RIGHTS, and the data portion of the messages is an array of integers repre-
     senting the file descriptors to be passed.  The number of descriptors being passed is defined by the length field of the message; the length
     field is the sum of the size of the header plus the size of the array of file descriptors.

     The received descriptor is a duplicate of the sender's descriptor, as if it were created with a call to dup(2).  Per-process descriptor
     flags, set with fcntl(2), are not passed to a receiver.  Descriptors that are awaiting delivery, or that are purposely not received, are
     automatically closed by the system when the destination socket is closed.

     The effective credentials (i.e., the user ID and group list) the of a peer on a SOCK_STREAM socket may be obtained using the LOCAL_PEERCRED
     socket option.  This may be used by a server to obtain and verify the credentials of its client, and vice versa by the client to verify the
     credentials of the server.  These will arrive in the form of a filled in struct xucred (defined in sys/ucred.h).  The credentials presented
     to the server (the listen(2) caller) are those of the client when it called connect(2); the credentials presented to the client (the
     connect(2) caller) are those of the server when it called listen(2).  This mechanism is reliable; there is no way for either party to influ-
     ence the credentials presented to its peer except by calling the appropriate system call (e.g., connect(2) or listen(2)) under different
     effective credentials.

SEE ALSO

     socket(2), intro(4)

     "An Introductory 4.3 BSD Interprocess Communication Tutorial", PS1, 7.

     "An Advanced 4.3 BSD Interprocess Communication Tutorial", PS1, 8.

BSD
								   June 9, 1993 							       BSD