Re: Directory/File Access Permissions for COPY and Generic File Access Functions

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Stephen Frost <sfrost(at)snowman(dot)net>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Adam Brightwell <adam(dot)brightwell(at)crunchydatasolutions(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Directory/File Access Permissions for COPY and Generic File Access Functions
Date: 2014-10-29 16:09:00
Message-ID: 25457.1414598940@sss.pgh.pa.us
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Stephen Frost <sfrost(at)snowman(dot)net> writes:
> * Robert Haas (robertmhaas(at)gmail(dot)com) wrote:
>> I think the question is "just how innumerable are those attack
>> routes"? So, we can prevent a symlink from being used via O_NOFOLLOW.
>> But what about hard links?

> You can't hard link to files you don't own.

That restriction exists on only some platforms. Current OS X for instance
seems perfectly willing to allow it (suggesting that most BSDen probably
do likewise), and I see no language supporting your claim in the POSIX
spec for link(2).

This points up the fact that platform-specific security holes are likely
to be a huge part of the problem. I won't even speculate about our odds
of building something that's secure on Windows.

regards, tom lane

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