Understanding Operating Systems (6th Edition)

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- Understanding Operating System, 6Th Edition by Flynn

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When did Unix move away from storing clear text passwords in passwd? Also, when was the shadow file introduced?


They explain why and how early Unix systems acquired most the features that are still seen today as the important features of password storage but done better. It spread out gradually to other Unix variants partly via the third party shadow suite whose descendent is still used on Linux today and wasn't available everywhere until the mids or so.

Operating System: Definition, Objective , Function and Types

Over the years, there have been improvements to the hashing algorithm. It removed the limitation to 8 password characters and 2 salt characters and had increased slowness. The SHAbased algorithms that are the de facto standard today are based on the same principle, but with slightly better internal design and, most importantly, a configurable slowness factor.

Understanding Operating System, 6Th Edition

I am not a big fan of copy-paste so have a look at the history section in the wikipedia's passwd page ;. EDIT: As it seems it's not a good practice to just share a link with the exact information that you want. So apart from the link let me also quote the wikipedia's relevant section here:.

But, vendors who had performed ports from earlier UNIX releases did not always include the new password shadowing features in their releases, leaving users of those systems exposed to password file attacks. System administrators may also arrange for the storage of passwords in distributed databases such as NIS and LDAP, rather than in files on each connected system. In the case of NIS, the shadow password mechanism is often still used on the NIS servers; in other distributed mechanisms the problem of access to the various user authentication components is handled by the security mechanisms of the underlying data repository.

In the author of the original Shadow Password Suite, Julie Haugh, experienced a computer break-in and wrote the initial release of the Shadow Suite containing the login, passwd and su commands.

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The original release, written for the SCO Xenix operating system, quickly got ported to other platforms. The Shadow Suite was ported to Linux in one year after the original announcement of the Linux project, and was included in many early distributions, and continues to be included in many current Linux distributions. I don't yet have a primary source, but according to this TrustedSec post emphasis mine :. Early systems stored passwords in plaintext but eventually this was replaced by more secure forms of password storage.

Robert Morris developed crypt based on the m cipher machine and it appeared in Version 3 Unix , though Crypt was not used to store passwords until 6th Edition Unix From the original paper by Thompson and Morris , we can confirm that plaintext storage was originally used:. The UNIX system was first implemented with a password file that contained the actual passwords of all the users, and for that reason the password file had to be heavily protected against being either read or written.

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