Configuring Ssh2.0; Overview; Ssh Operation - H3C S5120-HI Security Configuration Manual

Configuring SSH2.0

Overview

Secure Shell (SSH) offers an approach to logging in to a remote device securely. Using encryption and
strong authentication, SSH protects devices against attacks such as IP spoofing and plain text password
interception.
The switch can not only work as an SSH server to support connections with SSH clients, but also work as
an SSH client to allow users to establish SSH connections with a remote device acting as the SSH server.
When acting as an SSH server, the switch supports SSH2.0 and SSH1. When acting as an SSH client,
the switch supports SSH2.0 only.
When acting as an SSH server, the switch supports SSH2.0 and SSH1 in non-FIPS mode and supports
SSH2 in FIPS mode. When acting as an SSH client, the switch supports SSH2.0 only.
Unless otherwise noted, SSH in this document refers to SSH2.0.

SSH operation

To establish an SSH connection and communicate with each other through the connection, an SSH client
and the SSH server go through the stages listed in
Table 15 Stages in session establishment and interaction between an SSH client and the server
Stages
Version negotiation
Key and algorithm negotiation
Authentication
Session request
Interaction
Version negotiation
The server opens port 22 to listen to connection requests from clients.
1.
The client sends a TCP connection request to the server.
2.
After the TCP connection is established, the server sends a packet that carries a version information
3.
string to the client. The version information string is in the format SSH-<primary protocol version
number>.<secondary protocol version number>-<software version number>. The primary and
secondary protocol version numbers constitute the protocol version number. The software version
number is used for debugging.
Table 15.
Description
SSH1 and SSH2.0 are supported. The two parties negotiate a version to
use.
SSH supports multiple algorithms. The two parties negotiate algorithms
for communication, and use the DH key exchange algorithm to generate
the same session key and session ID.
The SSH server authenticates the client in response to the client's
authentication request.
After passing authentication, the client sends a session request to the
server.
After the server grants the request, the client and the server start to
communicate with each other.
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