NAME
SYNTAX
#include
DESCRIPTION
RESTRICTIONS
VERSION
AUTHOR
REFERENCES
SEE ALSO

## NAME

authuser - remote authentication library using the Authentication Server

## SYNTAX

## #include

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; |

## 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, depend- ing 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: user- name. 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.

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 connec- tion 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,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 seconds.

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 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)