Re: OPENSSH 3.4p1-3 on AIX 4.3.3

From: Alf Nicolaysen <Alf.Nicolaysen(at)de.ibm.com>
Date: Fri Feb 14 2003 - 08:11:33 EST

Hi, Neil.

What you guessed is right. The RhostsAuthentication is set to yes and the ignorerhosts is set to no. The Reversemapping was commented out in the sshd_config, I commented it in, but unfortunately without changes to the result. Teh debug output from the server is exactly the same, except another port (which of course I can not determine).

The DNSLookup AND the ReverseLookup are working fine, as they are doing for all other applications. But I guess you are right, Errormessage points to that DNS-Problem which I cannot see on one of the machines.

regards

Alf Nicolaysen

Neil Martin <Neil@Car-Part.com> on 14.02.2003 13:47:54

To: Alf Nicolaysen/Germany/Contr/IBM@IBMDE cc:
Subject: Re: OPENSSH 3.4p1-3 on AIX 4.3.3

Alf,

I am assuming the you have RhostsAuthentication  set to yes and IgnoreRhosts set to no in the servers sshd_config.  If so do you have reverse dns setup properly for that client?  Also what is the setting of the servers VerifyReverseMapping since it looks like you are failing on the reverse dns lookup.

Neil
Alf Nicolaysen wrote:

Neil,

thx for your answer so far. I tested it immediately and: It did not work! Here`s the output for the server in debug modus:

debug1: Server will not fork when running in debugging mode. Connection from 9.164.18.128 port 982

debug1: Client protocol version 1.5; client software version OpenSSH_3.4p1
debug1: match: OpenSSH_3.4p1 pat OpenSSH*
debug1: Local version string SSH-1.99-OpenSSH_3.4p1
debug2: Network child is on pid 27530
debug1: Sent 768 bit server key and 1024 bit host key.
debug1: Encryption type: 3des
debug2: monitor_read: 28 used once, disabling now
debug2: monitor_read: 30 used once, disabling nowdebug1: cipher_init: set

keylen (16 -> 32)

debug1: cipher_init: set keylen (16 -> 32)
debug1: Received session key; encryption turned on.
debug1: Installing crc compensation attack detector.
debug2: monitor_read: 6 used once, disabling now
debug1: Attempting authentication for nicolays.

Failed none for nicolays from 9.164.18.128 port 982 Could not reverse map address 9.164.18.128. debug2: auth_rhosts2: clientuser nicolays hostname 9.164.18.128 ipaddr 9.164.18.128
debug1: temporarily_use_uid: 201/1 (e=7) debug1: restore_uid
Failed rhosts for nicolays from 9.164.18.128 port 982 ruser nicolays debug1: rcvd SSH_CMSG_AUTH_TIS
Failed challenge-response for nicolays from 9.164.18.128 port 982

As you can, the client uses an privileged Port and shows up protocol 1.5. At the end of this output, two things are suspicious:

1)Seems to have name-resolution problems with this IP-Adress 9.164.18.128
(the client of course), but DNS is ok
2)Why at the end the server tries to authenticate via the TIS-Auth??

Further ist says "Failed rhosts for nicolays from 9.164.18.128 port 982" What does it exactly mean? Couldn't the server READ the rhosts, in this case .shosts? Or couldn't he simply not find it? Or wrong permissions ?
(Strictmode is set to default = no)

Any more help is very much appreciated.

Thx in advance

Alf Nicolaysen

Neil Martin <Neil@Car-Part.com> on 13.02.2003 21:51:54

To: Alf Nicolaysen/Germany/Contr/IBM@IBMDE cc:
Subject: Re: OPENSSH 3.4p1-3 on AIX 4.3.3

Alf,

I got that working under 3.5 on Solaris using .rhosts by doing something like ssh -o "RhostsAuthentication yes" - o "UsePrivilegedPort yes" - o "Procotol 1". It should work for .shosts

It appears that the version 2 Protocol will not allow rhosts authentication. In order to use the privileged port (low ports) you will need to set the suid bit on ssh or run ssh from the root account. This is very dangerous and insecure since someone would just need to spoof one of your clients IP's and they are in. The recommended method
(under 2.0 of the protocol) would be to use ssh-agent to remember your
clients pass phrases. This is less vulnerable to spoofing.

Hope this helps.

Neil
Alf Nicolaysen wrote:

Hi all!

I try to substitute a normal rsh/rlogin environment to a ssh-environment on some AIX 4.3.3 machines. For this environment I want to establish a PasswordAuthentication (with all his security risks) and, if present, a secure login without password using .shosts. Here starts the problem.

There

is no way, as far as I tested, to use a .shosts file. In any case this

file

will be ignored, regardless of modes, ownerships or user.

There a two ways of loging into a machine: 1) A normal ssh to a machine

and

i have to give the password.
2) I first copy the id_rsa.pub of the user into the authorized_keys of the second machine and then i can login into the machine without password.

With RhostsAuthentication, I get the only worthful message into the debug message:

debug1: Rhosts Authentication disabled, originating port 33754 not

trusted.

How can the server machine trust a non-privileged port, that is choosen randomly??

What went wrong here?

regards

Alf Nicolaysen Received on Fri Feb 14 13:48:33 2003