Configuring An Ssh Server - H3C S7500 Series Operation Manual

Operation Manual – SSH Terminal Service
H3C S7500 Series Ethernet Switches
Through the above steps, the server and the client get the same session key, which is
to be used to encrypt and decrypt data exchanged between the server and the client
later. The server and the client use session ID in the authentication stage.
3) Authentication stage
The client sends to the server an authentication request, which includes the username
and authentication method, and the server starts to authenticate the client.
SSH provides two authentication methods: password authentication and RSA
authentication.
For password authentication:
The client encrypts the username and password, encapsulates them into a
password authentication request, and sends the request to the server.
Upon receiving the request, the server decrypts the username and password,
compares them against those it maintains, and then informs the client of the
authentication result.
For RSA authentication:
The client sends to the server an RSA authentication request containing its RSA
public key modulus.
The server validates the modulus. If the modulus is invalid, the authentication fails;
otherwise, the server generates a 32-byte random number, converts it to a
multiple precision (MP) integer (MSB first), encrypts it using the RSA public key
from the client, and then sends a challenge to the client.
Upon receiving the challenge, the client decrypts it with its private key and gets an
MP integer, creates an MD5 value using the MP integer and the session ID, and
then encrypts and sends the MD5 value to the server.
After receiving the encrypted MD5 value, the server decrypts it to obtain the MD5
value and compares it with that locally calculated. If they match, the authentication
succeeds.
4) Session request stage. The client sends session request messages to the server
which processes the request messages.
5) Interactive session stage. Both ends exchange data till the session ends.

1.1.2 Configuring an SSH Server

The following table describes SSH server configuration tasks.
Chapter 1 SSH Terminal Service Configuration
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