LevelOne GEL-5261, User Manual

Page: 271 / 570

Chapter 12
| Security Measures
Configuring the Secure Shell
– 271 –
3.
Import Client’s Public Key to the Switch – See “Importing User Public Keys” on
page 275 to copy a file containing the public key for all the SSH client’s granted
management access to the switch. (Note that these clients must be configured
locally on the switch via the User Accounts page as described on
page 253 .) 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
134108168560989392104094492015542534763164192187295892114317388005553616163105
177594083868631109291232226828519254374603100937187721199696317813662774141689
851320491172048303392543241016379975923714490119380060902539484084827178194372
288402533115952134861022902978982721353267131629432532818915045306393916643
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.
Authentication – One of the following authentication methods is employed:
Password Authentication (for SSH v1.5 or V2 Clients)
a.
The client sends its password to the server.
b.
The switch compares the client's password to those stored in memory.
c.
If a match is found, the connection is allowed.
Note: 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.
Public Key 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:
Authenticating SSH v1.5 Clients
a.
The client sends its RSA 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 its secret key to generate a random
256-
bit string as a challenge, encrypts this string with the user’s public
key, and sends it to the client.
d.
The client uses its private key to decrypt the challenge string, computes
the MD5 checksum, and sends the checksum back to the switch.