Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!munnari.oz.au!uniwa!DIALix!bernie
From: bernie@DIALix.oz.au (Bernd Felsche)
Newsgroups: comp.unix.questions
Subject: Re: passwd access method?
Summary: Filesystem lock
Message-ID: <557@DIALix.oz.au>
Date: 30 Aug 90 06:15:23 GMT
Expires: 31 Aug 90 00:00:00 GMT
References: <14920004@hpdmd48.boi.hp.com>
Reply-To: bernie@DIALix.oz.au (Bernd Felsche)
Organization: DIALix Services, Perth Western Australia
Lines: 28

In article <14920004@hpdmd48.boi.hp.com> markw@hpdmd48.boi.hp.com (Mark Wolfe) writes:
>
[intro deleted]>
>    My question is this:
>    Is there a proper way to access the passwd file to insure file inegrity and
>security? I use the lockf call to reduce the chance of simultaneous access doing
>some unknown damage to the file. Is this sufficient, or are there other checks
>I should be making to insure multiple accesses leave the file in a good state?

Historically speaking, the standard used to be to mkdir /etc/ptmp
before editing /etc/passwd, and the do an rmdir /etc/ptmp after
writing out mod's.  This works for all users because even root
can't mknod a special file if it already exists.

The other advantage is that the existence of /etc/ptmp can be
checked in shell scripts, whereas file locks are more difficult to
identify.
>
>    I guess I'm trying to find out if there is some standard (even defacto
>standard) method of accessing the password file, or does everyone that does 
>this invent their own method.
>

As far as I know, this is the standard method, but I'm not sure too
many people know about it.


bernie