SSH Configuration Guide for Gentoo Infrastructure Servers
1.
Gentoo Infrastructure guidelines for running SSH
General Guidelines
SSH is currently the only approved method of obtaining a remote shell on a server. rsh, telnet and other insecure methods are not allowed. When configuring SSH, the following guidelines should be adhered to:
- SSHv2 only -- never configure sshd to support version 1 of the SSH protocol. It has known weaknesses with the way it encrypts data.
- DSA keys -- DSA keys are preferred over RSA keys
- No root login -- remote root login is not allowed. Users should login using their regular ID and then use sudo and/or su
- No password authentication -- where possible users should be required to use DSA keys to authenticate.
Note:
Unless specified above, the default values used in /etc/ssh/sshd_config are acceptable and should not be overridden without prior approval from the Gentoo Infrastructure project manager.
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Sample sshd_config file
Here is a sample /etc/ssh/sshd_config file which may be used to quickly set up SSH on a new Gentoo Infrastructure server.
Code Listing 1.1: /etc/ssh/sshd_config |
Port 22
Protocol 2
ServerKeyBits 2048
SyslogFacility AUTH
LogLevel INFO
LoginGraceTime 60
PermitRootLogin no
RSAAuthentication no
PubkeyAuthentication yes
PasswordAuthentication no
PermitEmptyPasswords no
PAMAuthenticationViaKbdInt no
Compression yes
KeepAlive yes
ClientAliveInterval 30
ClientAliveCountMax 4
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Note: In the example above, password authentication has been disabled in favor of key-based authentication. |
Note: Where server resources (especially CPU utilization) are limited, compression may be set to 'no' to prevent the server from dedicating CPU cycles to compressing data sent to clients |
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