Date: Thu, 20 Nov 2014 08:49:23 +0000 From: Vitor Ventura <ventura.vitor@...il.com> To: oss-security@...ts.openwall.com Subject: Re: Re: Linux user namespaces can bypass group-based restrictions I was wondering if this might pose a problem to android's application file sandboxing. If an application can run a native lib that could exploits this it might have access to other aplication files. A 0h24 qui, 20 de Nov de 2014, Andy Lutomirski <luto@...capital.net> escreveu: > On 11/17/2014 10:43 AM, Andy Lutomirski wrote: > > This is a heads-up, as there is no fix right now. > > > > On Linux, if you can unshare your user namespace (which is the case on > > many distributions), then you can map your fsuid and fsgid into the > > new namespace and, inside that namespace, drop all of your other > > groups. > > > > This may allow you to access files protected by POSIX ACLs as "other", > > even if the ACL should have prohibited it based on one of your > > supplementary group IDs. > > > > This does not appear to allow you to violate negative sudoers > > group entries and the like, since sudo(8) would be confined to the > > user namespace as well and will therefore not gain privilege. > > > > To those who care about credit: this was discovered by some > > combination of me, Theodore Ts'o, Eric Biederman, Alan Cox, and Casey > > Schaufler. > > > > See here for some more discussion: > > http://thread.gmane.org/gmane.linux.man/7385/ > > > > Disabling CONFIG_USER_NS works around this issue. > > Does this need a CVE? Fedora and Ubuntu are likely to be affected in > their default configurations. I don't know about the other distributions. > > --Andy > > > > > --Andy > > > >
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