linux-kernel - Re: RFC: KEYS: Is this too-big a behavioural change for a system call?

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Message-ID: <alpine.LRH.2.02.1401311200310.11589@tundra.namei.org>
Date:	Fri, 31 Jan 2014 12:07:09 +1100 (EST)
From:	James Morris <jmorris@...ei.org>
To:	David Howells <dhowells@...hat.com>
cc:	torvalds@...ux-foundation.org, ghudson@....edu, simo@...hat.com,
	sgallagh@...hat.com, keys@...ux-nfs.org,
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: RFC: KEYS: Is this too-big a behavioural change for a system
 call?

On Thu, 30 Jan 2014, David Howells wrote:

>  (5) Don't implicitly create a new anonymous keyring and don't implicitly set
>      the session keyring to the user-session keyring, but rather just fall back
>      to using the user-session keyring if there isn't a session keyring.
> 

> 
> That said, I do think that the Kerberos people have a valid point.  The current
> behaviour is poor.  I'm inclined to implement (5) or (6), probably (5).
> 
> This won't make any difference to most processes, ie.:
> 
>  (*) Those run from pam_keyinit-managed login shells.
> 
>  (*) Those that don't make use of libkrb5 or keyrings.
> 

So there are existing apps which will see semantic changes?

If so, we can't accept this change.

> In many ways, I'd like to just get rid of the user and user-session keyrings
> from the kernel entirely and have them created and maintained by pam_keyinit.
> The special keyring IDs:
> 
> 	KEY_SPEC_USER_KEYRING
> 	KEY_SPEC_USER_SESSION_KEYRING
> 
> and:
> 
> 	KEY_REQKEY_DEFL_USER_KEYRING
> 	KEY_REQKEY_DEFL_USER_SESSION_KEYRING
> 
> would then search your session keyring for keyrings called "_uid" and
> "_uid_ses" and return those.  Unfortunately, I think this is probably a
> much-too-big change at this point.
> 
> Any thoughts?

Getting it right is more important than the size of the change.

What about creating a new system call with the desired behavior, and 
deprecating the current one (or at least, making it a wrapper for the new 
call).

-- 
James Morris
<jmorris@...ei.org>
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