What is identd?

[krose at theory.lcs.mit.edu (Kyle Rose)]

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Bill Horne <bhorne at banet.net> writes:

> This is probably a newbie question, but there's nothing in
> the RH 5.2 info or man pages about it.
> 
> My ppp log shows at least one of these errors every time I
> log on:
> 
> <date> <time> localhost inetd[486]: execv
> /usr/sbin/in.identd: no such file or directory.
> 
> Please tell me why, and thanks for your time.

The ident protocol is one which allows a remote machine to determine
which user on your machine is responsible for a connection to their
machine.  If you want to check it out for yourself, telnet to your own 
machine and type netstat -n.  You'll see something like the following:

Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address           Foreign Address State      
tcp        0    128 127.0.0.1:23            127.0.0.1:1287  ESTABLISHED 
tcp        0      0 127.0.0.1:1287          127.0.0.1:23    ESTABLISHED 
tcp        0      0 18.23.3.67:1023         18.52.0.248:22  ESTABLISHED 

If you then telnet again to your own machine on port ident, you can
type in a port pair separated by a comma, and it will spit out the
username associated with that connection.  E.g.,

krose at twilight-symphony:~% telnet 127.0.0.1 ident
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
1287,23
1287 , 23 : USERID : UNIX : krose
Connection closed by foreign host.

This protocol is used by many daemons on remote machines to log the id
of the user making the connection.  It is mostly of use when one
wishes to inform a sysadmin that one of his users is causing trouble
for a remote machine.  If you run your own system, you can of course
hack identd to produce any response you want, which negates the
utility of the protocol. =)

The fact that you're seeing the "no such file or directory" message
suggests that identd is either not installed or is improperly
installed.  This is unfortunate, since many web servers require identd
authentication to proceed, so you will see "Waiting for response..."
forever when trying to view web pages on these hosts.  You should
definitely fix this problem, or write a simple program that produces
fake output, and compile this to /usr/sbin/in.identd.  Such a program
in C might be

#include <stdio.h>

main() {
        int i,j;
        scanf("%d,%d",&i,&j);
        printf("%d , %d : USERID : UNIX : blah\n",i,j);
        return 0;
}

Kyle


- -- 
Kyle R. Rose                      "They can try to bind our arms,
Laboratory for Computer Science    But they cannot chain our minds
MIT NE43-309, 617-253-5883             or hearts..."
http://web.mit.edu/krr/www/                           Stratovarius
krose at theory.lcs.mit.edu                              Forever Free
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