z
The client selects an authentication type from the method list to perform authentication again.
The above process repeats until the authentication succeeds, or the connection is torn down when
the authentication times reach the upper limit.
provides two authentication methods: password authen
z
SSH
tication and publickey authentication.
z
z
tal signatures. The client sends to the
server a
hentication request containing its user name, public key and algorithm. The server
S
authentication, the server sends back to
H_SMSG_SUCCESS packet and goes on to the interactive session stage with the
G_FAILURE packet, indicating that
ds a session request to the server,
ic
Data
ge
y:
nds the command to be executed to the server.
executes the command, and then encrypts and sends the result to the
SSH Ser
configured as an SSH server
5-2
In 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 with those it maintains,
and then informs the client of the authentication result.
The publickey authentication method authenticates clients using digital signatures. Currently, the
device supports only RSA to implement digi
publickey aut
verifies the public key. If the public key is invalid, the authentication fails; otherwise, the server
generates a digital signature to authenticate the client, and then sends back a message to inform
the success or failure of the authentication.
ession request
After passing authentication, the client sends a session request to the server, while the server listens to
and processes the request from the client. If the client passes
the client an SS
client. Otherwise, the server sends back to the client an SSH_SMS
the processing fails or it cannot resolve the request. The client sen
wh h processes the request and establishes a session.
exchan
In this stage, the server and the client exchanges data in this wa
z
The client encrypts and se
z
The server decrypts and
client.
z
The client decrypts and displays the result on the terminal.
ver and Client
To use SSH for secure login to a switch from a device, the switch must be
and the device must be configured as an SSH client. As shown in
Figure 5
, Host A, Host B, and Host
s acting as the SSH server.
D are configured as SSH clients to securely access the Switch A, which i
