Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Tue, 3 Jul 2018 20:48:54 +0200
From: Jann Horn <>
Cc: Kernel Hardening <>
Subject: Re: Patch for SymlinksIfOwnerMatches

On Tue, Jul 3, 2018 at 8:29 PM Hanno Böck <> wrote:
> There's a nasty problem in many webserver configurations on multiuser
> systems, I've blogged about it a while ago [1]. With a symlink it's
> often possible to read out configuration files of other users. This was
> famously used in the freedom hosting II hack [2].
> grsecurity had a workaround for this: By not allowing file operations
> to follow symlinks if the owner of the link and the target don't match
> it can block this kind of attack.
> I saw a need to keep this feature alive in a post-grsecurity world, so
> a while ago I extracted it from the grsecurity patch. I've now made
> that public:
> I'm not sure about upstreaming, I think it's a worthy feature, but it
> might need some work in polishing it. But for now I'll just share it
> and I will hopefully be able to keep the patch working for future
> kernels.
> [1]
> [2]

Does upstream's /proc/sys/fs/protected_symlinks not work for that?

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.