SSH Tectia 
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    About This Document >>
    Installing SSH Tectia Server for IBM z/OS >>
    Using SSH Tectia Server for IBM z/OS >>
    Configuring the Server >>
    Configuring the Client
        Securing the Client
            Client Configuration
    Authentication >>
    Troubleshooting SSH Tectia Server for IBM z/OS >>
    Examples of Use >>
    Man Pages >>
    Log Messages >>

Client Configuration

Connecting to servers whose admin you do not trust and who may be malicious is a significant security risk. Avoid it. However, there are a few ways to reduce the risk.

Disabling X11 Forwarding

X11 forwarding exposes your X server (the client side in this context) to a malicious root user on the server machine.

If you are connecting to a host you do not trust, or where you do not need execute X applications, disable X11 forwarding.

In your ssh2_config file, add the following line:

ForwardX11          no

On the command line, the -x option has the same effect:

% ssh2 -x host

Disabling Agent Forwarding

By default, when you have an agent running, the agent connection will be forwarded to the server side. This is for convenience, so that a system admin (or a power user) can easily hop from machine to machine.

If the server's administrator is malicious, he can use your agent to sign requests. This will not allow access to the private key, but will cause a security risk, because the malicious admin can then connect with your credentials anywhere where they are accepted.

So, if you do not trust the server, disable agent forwarding in your ssh2_config file:

ForwardAgent        no

On the command line, the -a option has the same effect:

% ssh2 -a host

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