Date: Fri, 12 Jul 2019 14:40:19 +0000 From: Jordan Glover <Golden_Miller83@...tonmail.ch> To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com> Cc: Simon McVittie <smcv@...ian.org> Subject: Re: Privileged File Access from Desktop Applications On Friday, July 12, 2019 12:37 AM, Perry E. Metzger <perry@...rmont.com> wrote: > On Thu, 11 Jul 2019 21:20:15 +0100 Simon McVittie smcv@...ian.org > wrote: > > > On Thu, 11 Jul 2019 at 11:47:10 -0400, Perry E. Metzger wrote: > > > > > having to add file i/o subsystems inside of dbus(!) probably does > > > add lots of threats > > > > I think you might be misunderstanding the scope of D-Bus. > > Not really. The whole point is that instead of having the operating > system alone as part of your file security implementation you now > have a brand new service, an IPC mechanism, and loads of other stuff, > instead of having your app just do open(2) and write(2) etc. Do you mean that IPC and D-bus aren't part of the OS? Then what is? > It seems architecturally bad from a security perspective. The number > the number of trusted entities, the number of moving parts, the number > of mechanisms, and thus the number of ways things can go wrong keeps > going up. This is a mistake. And btw, this is a major piece of > mechanism being added just to handle the problem of someone wanting to > pop open an editor inside a GUI to edit a system config file, which is > not a major attack vector. But, now I have to worry about this new > file access service providing an attack surface that didn't exist > before. > > What's the right way to handle this stuff? Capabilities, > probably. It's what they're designed for. They're completely not designed for this case. Setting CAP_DAC_OVERRIDE or CAP_SYS_ADMIN is very close to SUID root. See: https://grsecurity.net/false_boundaries_and_arbitrary_code_execution.php Jordan
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