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Re: lynx-dev symlinks to other users' files; broken symlinks

From: Philip Webb
Subject: Re: lynx-dev symlinks to other users' files; broken symlinks
Date: Sat, 10 Oct 1998 17:40:10 -0400 (EDT)

981010 Benjamin Sittler wrote: 
> Symlinks to other people's files are often used here at the New Mexico
> Tech Computer Center so that a large group of users can share a single,
> easily-updated configuration file for Lynx, FVWM, or some other package.
> There are several of these widely-used configuration files, none of them
> controlled by the computer center (they have their default system.fvwmrc
> and lynx.cfg, though, so you can still use these programs without a copy
> or symlink to someone's .fvwmrc or .lynxrc.)  This is great, as it allows
> users to easily adopt each other's settings, without the synchronization
> problems introduced by copying.  Obviously, this requires a relation
> of trust between the user maintaining the file & the users symlinking to it

this appears to be a case where User A deliberately permits User B
to make a symlink to User A's file, presumably setting  -rwxrwxrwx :
User A MUST give permission or anyone could symlink to anyone else's files.
that can never raise security concerns about malicious misuse:
User A fully expects User B to write into User A's file sometimes.
> Broken symlinks (that is, symlinks to non-existent files) are also
> quite common, as the systems at the computer center do not have totally
> homogeneous filesystem layouts.  It's often useful to link to a
> machine-local configuration file, and fall back on a global system default
> configuration file if the machine-local configuration file does not exist.

you've lost me with your sudden jump to talking about "machines":
do you mean virtual machines a la VM-CMS or networked machines of some kind?

> EG User A might have a custom configuration for lynx that he's trying
> on his own machine, and so he has a symlink pointing from .lynxrc
> in his home directory to wherever the custom .lynxrc is on his machine.
> But he'd still like to use Lynx on other machines, and doesn't want
> to worry about his (possibly-broken) custom configuration
> except when using his own machines.

so what are these machines & how does he get to use other people's?
> Ideally, he'd like Lynx to use the global lynx.cfg (only) on most machines,
> but also his personal lynx.cfg on his machine.  This means
> that on most machines, .lynxrc will be a broken symlink
> (probably to a directory that doesn't even exist elsewhere.)

i have no problem at all with symlinks which point to non-existent files:
the issue is how symlinks can threaten security on a properly managed system.
> There are many more arcane reasons to allow lynx to use symlinked files
> owned by other users, and to gracefully ignore broken symlinks.
> Send me private email if you are interested in them,
> as this message is rather long already.
i'm certainly grateful for your thoughts, which are relevant to lynx-dev.
i've been deliberately shining a light into some dark corners
where cobwebs have been collecting for too long.

SUPPORT     ___________//___,  Philip Webb : address@hidden
ELECTRIC   /] [] [] [] [] []|  Centre for Urban & Community Studies
TRANSIT    `-O----------O---'  University of Toronto

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