Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Scaricare il pdf (Pagina 139)

Chapter 11.

Kerberos

Kerberos is a network authentication protocol created by MIT which uses secret-key cryptography

to secure passwords over the network. Encrypting passwords with Kerberos can help to thwart unau-

thorized users trying to intercept passwords on the network, thus adding an extra layer of system

security.

11.1. Advantages of Kerberos

Most conventional network systems use password-based authentication schemes. When a user needs

to authenticate to a service running on a network server, they type in their password for each service

that requires authentication. Their password is sent over the network, and the server veriﬁes their

identity using the password.

However, the transmission of password information in some authenticated services is done in clear

text. Any system cracker with access to the network and a packet analyzer, also known as a packet

sniffer, can intercept any passwords sent in this manner.

The primary design goal of Kerberos is to eliminate the clear-text passwords transfered across a net-

work. The proper use of Kerberos dramatically lessens the threat of packet sniffers intercepting pass-

words on your network .

11.2. Kerberos Disadvantages

Kerberos removes a common and severe security threat. However, it may be difﬁcult to implement for

various reasons:

• Migrating user passwords from a standard UNIX password database, such as /etc/passwd or

/etc/shadow, to a Kerberos password database can be tedious as there is no automated mechanism

to perform this task. Refer to the Kerberos FAQ Question 2.23 or see Section 11.8 for more detailed

information concerning this issue.

• Kerberos has only partial compatibility with the Pluggable Authentication Modules (PAM) system

used by most servers running Red Hat Linux. For more information on this issue, see Section 11.5.

• For an application to use Kerberos, its source must be modiﬁed to make the appropriate calls into

the Kerberos libraries. For some applications, this can be quite problematic due to size or frequency

that krb libraries must be called. For other applications, changes must be made to the way in which

the server and client side communicate. Again, this may require extensive programming. Closed-

source applications that do not have Kerberos support by default are often the most problematic.

• Kerberos assumes that you are using trusted hosts on an untrusted network. Its primary goal is to

prevent clear-text passwords from being sent across that network. However, if anyone other than

the proper user has physical access to any of the hosts, especially the one that issues tickets used

for authentication, the entire Kerberos authentication system is at risk of being compromised.

• Kerberos is an all or nothing solution. If you decide to use Kerberos on your network, you must

remember any passwords transferred to a service which does not use Kerberos for authentication

run the risk of being captured by packet sniffers. Thus, your network gains no beneﬁt from the

use of Kerberos. To secure your network with Kerberos, you must either kerberize all applications

which send clear-text passwords or do not use those applications on your network at all.

1 2 ... 134 135 136 137 138 139 140 141 142 143 144 ... 281 282

Nessun commento

Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE Guida di Installazione Pagina 139