authuser(3) authuser(3)
NAME
authuser - remote authentication library using the Authentication
Server
SYNTAX
#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,ctimeout);
char *auth_tcpuser4(inlocal,inremote,local,remote,ctimeout,rtimeout);
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;
DESCRIPTION
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:
username 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.
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authuser(3) authuser(3)
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
information 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
possible. s is closed by auth_sockuser. The advantage of using
auth_tcpsock 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 yet.
auth_tcpuser3(inlocal,inremote,local,remote,ctimeout) is like
auth_tcpuser2 but returns NULL with errno set to ETIMEDOUT if the
authentication request has not been accepted or refused after ctimeout
seconds.
auth_tcpuser4(inlocal,inremote,local,remote,ctimeout,rtimeout) is like
auth_tcpuser3 but returns NULL with errno set to ETIMEDOUT if the
reply to the authentication request is being sent slower than rtimeout
seconds/character.
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
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authuser(3) authuser(3)
implementations.
RESTRICTIONS
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.
VERSION
authuser version 4.0, February 9, 1992.
AUTHOR
Placed into the public domain by Daniel J. Bernstein.
REFERENCES
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.''
SEE ALSO
tcpclient(1), tcpserver(1), getpeername(3), getsockname(3), tcp(4),
authd(8)
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