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Old 12-22-2007, 09:28 AM   #1
CaptainReboot
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Question Unable to us SU to root when logged in via SSH


Hi guys,
I have sshd running and it has been running perfectly for some time. Logging in via SSH using root is disabled and root access is gained by logging in using a normal user account, issuing the 'su' command and entering the root password at the prompt.

All of a sudden, I am unable to use the su command. When entering 'su' the system asks me for the root password which, when entered, returns an 'Authorisation Failure' message. When I use the machine locally the root account works fine, it seems to only be when using an SSH connection.

This is very strange since I don't remember changing a thing. Does anyone have any bright ideas???

Many thanks in advance.
 
Old 12-22-2007, 09:41 AM   #2
jschiwal
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Look in your /etc/security/access.conf file. It may prohibit access for root on remote connections.

Check /etc/sudoers.
Look for the line:
Code:
%wheel  ALL=(ALL) SETENV: ALL
It may have been reconfigured during a security fix.
Check if the above line looks like this instead:
Code:
%wheel  LOCAL=(ALL) SETENV: ALL
Also, read the log in /var/log/messages and if you have it /var/log/secure. It may have recorded your su attempt when using ssh and indicate why su was rejected.
 
Old 12-22-2007, 09:43 AM   #3
shafey
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Dear CaptainReboot
please check the error when you run su at /var/log/message and /var/log/secure
and post errors here
 
Old 12-22-2007, 01:58 PM   #4
CaptainReboot
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Thanks for your response, but I'm afraid I haven't found anything based on your responses.

The sudoers file doesn't contain anything different to what it used to, /var/log/messages shows nothing and I don't have a /var/log/secure.

I've checked out /var/log/auth.log and can see the following:

Dec 22 18:47:35 localhost su[1305]: (pam_unix) authentication failure; logname= uid=1000 euid=0 tty=pts/0 ruser=<MY USERNAME> rhost= user=root
Dec 22 18:47:37 localhost su[1305]: pam_authenticate: Authentication failure
Dec 22 18:47:37 localhost su[1305]: FAILED su for root by <MY USERNAME>
Dec 22 18:47:37 localhost su[1305]: - pts/0 <MY USERNAME>:root

Last edited by CaptainReboot; 12-22-2007 at 02:00 PM.
 
Old 12-23-2007, 08:31 AM   #5
CaptainReboot
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This is really strange!

I've discovered my problem only exists when using PuTTY from a Windows box. If I ssh from a machine running Linux it all works fine!

Has anyone else seen anything similar to this when using Putty?
 
Old 12-29-2007, 06:36 AM   #6
shafey
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Dear

I guess You need to reconfigure SSH server or putty client
please check your ssh configuration and putty client program " allowed keys "
 
  


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