Date: Tue, 3 Jul 2018 20:48:54 +0200 From: Jann Horn <jannh@...gle.com> To: hanno@...eck.de Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com> Subject: Re: Patch for SymlinksIfOwnerMatches On Tue, Jul 3, 2018 at 8:29 PM Hanno Böck <hanno@...eck.de> wrote: > There's a nasty problem in many webserver configurations on multiuser > systems, I've blogged about it a while ago . 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 . > > 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: > https://github.com/hannob/symlinkown > > 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. > >  > https://blog.hboeck.de/archives/873-The-tricky-security-issue-with-FollowSymLinks-and-Apache.html >  > https://securityaffairs.co/wordpress/55990/deep-web/freedom-hosting-ii-hack.html Does upstream's /proc/sys/fs/protected_symlinks not work for that?
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