authuser(3zm)                                                    authuser(3zm)

       authuser  -  remote  authentication  library  using  the Authentication

       #include <authuser.h>

       unsigned short auth_tcpport;

       char *auth_xline(user,fd,&inremote);

       int auth_fd(fd,&inremote,&local,&remote);
       int auth_fd2(fd,&inlocal,&inremote,&local,&remote);

       int auth_tcpsock(fd,inlocal,inremote);

       char *auth_tcpuser(inremote,local,remote);
       char *auth_tcpuser2(inlocal,inremote,local,remote);
       char *auth_tcpuser3(inlocal,inremote,local,remote,timeout);

       char *auth_sockuser(s,local,remote);

       char *user;
       int fd;
       int s;
       unsigned long inlocal;
       unsigned long inremote;
       unsigned short local;
       unsigned short remote;
       int timeout;

       Actually should talk  about  'identification',  there  is  no  definite
       authentication in here..

       The  authuser  library  provides a simple interface for finding out the
       remote identity of a connection through the  Authentication  Server  as
       specified  by  RFC  931.  Use the -lauthuser loader option to compile a
       program with this library.

       auth_xline(user,fd,&inremote) returns a line of the  form  X-Auth-User:
       user  or  X-Forgery-By:  username,  depending upon what the host on the
       other side of fd thinks of the user.  This is particularly  appropriate
       for mail and news headers.

       If  the remote host reports that user owns the connection on that side,
       auth_xline will return X-Auth-User: user.  If the remote  host  reports
       that  a  different username owns the connection, auth_xline will return
       X-Forgery-By: username.  If user is NULL, it returns X-Auth-User: user-
       name with the username reported by the remote host.  If fd is not a TCP
       connection or authentication is impossible,  auth_xline  returns  NULL,
       setting errno appropriately.

       The  line is not cr-lf terminated.  It is stored in a static area which
       is overwritten on each  call  to  auth_xline.   auth_xline  places  the
       Internet address of the other host into inremote.

       auth_fd2(fd,&inlocal,&inremote,&local,&remote) retrieves address infor-
       mation from the connection  in  socket  fd.   It  places  the  Internet
       addresses of the connection into inlocal and inremote and the local and
       remote TCP ports into local  and  remote.   auth_fd2  returns  -1  upon
       error, setting errno appropriately.

       auth_tcpuser2(inlocal,inremote,local,remote)  returns  the  name of the
       user on the other end of the TCP connection between remote@inremote and
       local@inlocal.   If authentication is impossible, auth_tcpuser2 returns
       NULL, setting errno appropriately.  The user name is stored in a static
       area  which is overwritten on each call to auth_tcpuser2, auth_tcpuser,
       auth_sockuser, and auth_xline.

       s = auth_tcpsock(fd,inlocal,inremote) sets s to a  non-blocking  socket
       which  is  connecting  to  the  Authentication  Server at inremote.  It
       returns    -1    on     error,     setting     errno     appropriately.
       auth_sockuser(s,local,remote)  makes sure that the socket has connected
       and then does the same job as auth_tcpuser2, returning the name of  the
       user on the other end of the TCP connection between remote@inremote and
       local@inlocal, or NULL (with errno set) if authentication is not possi-
       ble.   s  is closed by auth_sockuser.  The advantage of using auth_tcp-
       sock and auth_sockuser instead of auth_tcpuser2 is that you can perform
       other actions while waiting for the authentication request to complete.
       You can select s for writing to see if it is  ready  for  auth_sockuser

       auth_tcpuser3(inlocal,inremote,local,remote,timeout)       is      like
       auth_tcpuser2 but returns NULL with  errno  set  to  ETIMEDOUT  if  the
       authentication  request  has not been accepted or refused after timeout

       auth_fd(fd,&inremote,&local,&remote) is the same as auth_fd2 but throws
       away  the  inlocal information.  auth_tcpuser(inremote,local,remote) is
       the same as auth_tcpuser2 but may not bind to the proper local  address
       on  hosts  with  multiple IP addresses.  These functions do not perform
       properly on multihomed hosts and should not be used.  They are provided
       only for backwards compatibility.

       The authentication routines check with the remote Authentication Server
       on port auth_tcpport, which defaults to 113 as specified  by  RFC  931.
       You  can  set  auth_tcpport to other values for nonstandard implementa-

       authuser does no backslash interpretation upon the  remote  user  name.
       This is conformance with the proposed revision to RFC 931.

       authuser does not use the operating system type information provided by
       the Authentication Server.

       authuser version 4.0, February 9, 1992.

       Placed into the public domain by Daniel J. Bernstein.

       The authentication server is more secure than passwords in  some  ways,
       but  less  secure  than passwords in many ways.  (It's certainly better
       than no password at all---e.g., for mail or news.)  It is not the final
       solution.   For an excellent discussion of security problems within the
       TCP/IP protocol suite, see Steve Bellovin's article ``Security Problems
       in the TCP/IP Protocol Suite.''

       tcpclient(1),  tcpserver(1),  getpeername(3),  getsockname(3),  tcp(4),

                                  2003-Aug-28                    authuser(3zm)