Re: [capabilities] Allow normal inheritance for a configurable set of capabilities

Casey Schaufler
2015-02-02T19:00:22Z

On 2/2/2015 10:08 AM, Serge Hallyn wrote:
> Quoting Casey Schaufler (casey@schaufler-ca.com):
>> I'm game to participate in such an effort. The POSIX scheme
>> is workable, but given that it's 20 years old and hasn't
>> developed real traction it's hard to call it successful.
> Over the years we've several times discussed possible reasons for this
> and how to help. I personally think it's two things: 1. lack of
> toolchain and fs support. The fact that we cannot to this day enable
> ping using capabilities by default because of cpio, tar and non-xattr
> filesystems is disheartening. 2. It's hard for users and applications
> to know what caps they need. yes the API is a bear to use, but we can
> hide that behind fancier libraries. But using capabilities requires too
> much in-depth knowledge of precisely what caps you might need for
> whatever operations library may now do when you asked for something.

The fix for that is to a change to the audit system. If the audit system
reported the capabilities relevant to the decision you'd have what you
need. If you failed because you didn't have CAP_CHMOD or you succeeded
because you had CAP_SYS_ADMIN it should show up in the audit record.
Other systems have used this approach.

You could, of course, create a separate capability result log, and I
believe that Nokia had done something along those lines. I think that
adding it to the audit trail is a more rational approach.