May 2005
Intermediate to advanced
666 pages
21h 5m
English
book
SSH, The Secure Shell: The Definitive Guide, 2nd Edition
by Daniel J. Barrett, Richard E. Silverman, Robert G. Byrnes
Content preview from SSH, The Secure Shell: The Definitive Guide, 2nd Edition
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Access Control: Letting People In
Serverwide access control permits or denies connections from particular hosts or Internet domains, or to specific user accounts on the server machine. It’s applied separately from authentication: for example, even if a user’s identity is legitimate, you might still want to reject connections from her computer. Similarly, if a particular computer or Internet domain has poor security policies, you might want to reject all SSH connection attempts from that domain.
SSH access control is scantily documented and has many subtleties and “gotchas.” The configuration keywords look obvious in meaning, but they aren’t. Our primary goal in this section is to illuminate the murky corners so that you can develop a correct and effective access-control configuration.
Keep in mind that SSH access to an account is permitted only if both the server and the account are configured to allow it. If a server accepts SSH connections to all accounts it serves, individual users may still deny connections to their accounts. [8.2] Likewise, if an account is configured to permit SSH access, the SSH server on its host can nonetheless forbid access. This two-level system applies to all SSH access control, so we won’t state it repeatedly. Figure 5-2 summarizes the two-level access control system.[68]
Figure 5-2. Access control levels
5.5.1 Account Access Control
Ordinarily, any account ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.