Solved

Login problems

Posted on 2000-03-11
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Last Modified: 2010-04-20
I'm looking for some suggestions regarding a problem that just cropped up on my linux server.

What's happening is:  Attempts to login to the machine (telnet, rlogin, console, IMAP) fails.  Telnet doesn't even show the "username" prompt, console and rlogin attempts freeze up after the password: prompt.

sendmail is receiving mail, and I can retrieve it with POP, but not IMAP.  I can connect with FTP just fine.

I figure I should see a pattern here, but don't and would love it if someone could point it out to me.

All the files are local (no NFS)...

summary:

not working:
rlogin (stops after password entered)
console (stops after password entered)
telnet (not even a username: prompt)
IMAP fails to connect

working:
sendmail receive
POP3 fetch
FTP
WWW
ipfwd
samba

Anyone?
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Question by:wormzer
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9 Comments
 
LVL 3

Expert Comment

by:jyu_88
ID: 2608213
for all users or just one particular user? If just one user, then could be invalid shell.

telnet no prompt, could be telnetd is not running or inetd is not running or could fork new processes due to exhausted recoures (max # of processes, etc.)? Is this server a busy or heavy-loaded one?






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Author Comment

by:wormzer
ID: 2608228
No loads
All users
telnetd is running (spits out RedHat... welcome, just no "username" prompt.

You're where I was when I first noticed the problem. :)
0
 
LVL 8

Expert Comment

by:stefanx
ID: 2608244
I've found that in.telnetd attempts to do a reverse lookup on the source address first. When it cannot resolve (for example from a host within a masqueraded network), then it appears to hang. Give it about 3 minutes though and it eventually gives you a login prompt. Sendmail and pop3 don't do this, or at least don't wait that long for name resolution - imap, I don't know - have never used it.

If this is indeed your problem, install bind and set up zone files for your private IP's (if you are trying from a masqueraded network)

Hope that helps.
0
What is a Denial of Service (DoS)?

A DoS is a malicious attempt to prevent the normal operation of a computer system. You may frequently see the terms 'DDoS' (Distributed Denial of Service) and 'DoS' used interchangeably, but there are some subtle differences.

 
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Author Comment

by:wormzer
ID: 2608267
Adjusted points to 500
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Author Comment

by:wormzer
ID: 2608268
console logins don't work either is the thing.  No matter how long I wait.  It's something to do with /sbin/login I think.  I'm finally able to check on it some more so we'll see how it goes.

Also, masquerading and samba are both working.  I'll add them to my list above.
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Author Comment

by:wormzer
ID: 2608269
Edited text of question.
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Accepted Solution

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jlevie earned 500 total points
ID: 2608295
Have you changed anything recently, like upgraded some libraries or something related to pam? You didn't say what Linux, but on RedHat /bin/login is dynamically linked to a bunch of things. Also if /etc/pam.d/login gets screwed up it could cause this behaviour.  
0
 
LVL 1

Author Comment

by:wormzer
ID: 2608310
ugh.  It turns out that someone hacked in and screwed up the security stuff.  Nevermind.  I guess I'm going to have to go through that scrub that I've been putting off.

Thanks for all the help -- I'll just distribute the points to everyone who tried to help.
0
 
LVL 1

Author Comment

by:wormzer
ID: 2608314
Sorry -- for some reason I thought you could distribute points.  jlevie came the closest, so I gave them to him.

Thanks everyone.

Scrub... scrub...
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