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User Authentication
3-61
3
be configured locally on the switch via the User Accounts page as described on
page 3-53.) The clients are subsequently authenticated using these keys. The
current firmware only accepts public key files based on standard UNIX format as
shown in the following example for an RSA Version 1 key:
1024 35 1341081685609893921040944920155425347631641921872958921143173880
055536161631051775940838686311092912322268285192543746031009371877211996
963178136627741416898513204911720483033925432410163799759237144901193800
609025394840848271781943722884025331159521348610229029789827213532671316
29432532818915045306393916643 steve@192.168.1.19
4. Set the Optional Parameters – On the SSH Settings page, configure the optional
parameters, including the authentication timeout, the number of retries, and the
server key size.
5. Enable SSH Service – On the SSH Settings page, enable the SSH server on the
switch.
6. Challenge-Response Authentication – When an SSH client attempts to contact
the switch, the SSH server uses the host key pair to negotiate a session key and
encryption method. Only clients that have a private key corresponding to the
public keys stored on the switch can access it. The following exchanges take
place during this process:
a. The client sends its public key to the switch.
b. The switch compares the client's public key to those stored in memory.
c. If a match is found, the switch uses the public key to encrypt a random
sequence of bytes, and sends this string to the client.
d. The client uses its private key to decrypt the bytes, and sends the decrypted
bytes back to the switch.
e. The switch compares the decrypted bytes to the original bytes it sent. If the
two sets match, this means that the client's private key corresponds to an
authorized public key, and the client is authenticated.
Notes: 1.
To use SSH with only password authentication, the host public key must still
be given to the client, either during initial connection or manually entered into
the known host file. However, you do not need to configure the client’s keys.
2. The SSH server supports up to four client sessions. The maximum number
of client sessions includes both current Telnet sessions and SSH sessions.
Generating the Host Key Pair
A host public/private key pair is used to provide secure communications between an
SSH client and the switch. After generating this key pair, you must provide the host
public key to SSH clients and import the client’s public key to the switch as
described in the preceding section (Command Usage).