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Re: User namespaces and keys [message #41856 is a reply to message #41855]

Wed, 23 February 2011 15:53

Serge E. Hallyn
Messages: 26
Registered: February 2011

Junior Member

Quoting Eric W. Biederman (ebiederm@xmission.com):
> David Howells <dhowells@redhat.com> writes:
>
> > Serge E. Hallyn <serge@hallyn.com> wrote:
> >
> >> > I guess we need to look at how to mix keys and namespaces again.
> >>
> >> From strictly kernel pov, at the moment, keys are strictly usable only
> >> by the user in your own user namespace.
> >
> > I'm not sure that's currently completely true. Key quota maintenance is
> > namespaced, and the key's owner UID/GID belong to that namespace, so that's
> > okay, but:
> >
> > (*) key_task_permission() does not distinguish UIDs and GIDs from different
> > namespaces.
> >
> > (*) A key can be referred to by its serial number, no matter whose namespace
> > it is in, and will yield up its given UID/GID, even if these aren't
> > actually meaningful in your namespace.
> >
> > This means request_key() can successfully upcall at the moment.
> >
> > I wonder if I should make the following changes:
> >
> > (1) If the key and the accessor are in different user namespaces, then skip
> > the UID and GID comparisons in key_task_permission(). That means that to
> > be able to access the key you'd have to possess the key and the key would
> > have to grant you Possessor access, or the key would have to grant you
> > Other access.
> >
> > (2) If the key and someone viewing the key description are in different
> > namespaces, then indicate that the UID and the GID are -1, irrespective of
> > the actual values.
> >
> > (3) When an upcall is attempting to instantiate a key, it is allowed to access
> > the keys of requestor using the requestor's credentials (UID, GID, groups,
> > security label). Ensure that this will be done in the requestor's user
> > namespace.
> >
> > Nothing should need to be done here, since search_process_keyrings()
> > switches to the requestor's creds.
> >
> > Oh, and are security labels user-namespaced?
>
> Not at this time. The user namespace as currently merged is little more
> than a place holder for a proper implementation. Serge is busily
> fleshing out that proper implementation.
>
> Until we reach the point where all checks that have historically been
> "if (uid1 == uid2)" become "if ((uidns1 == uidns2) && (uid1 == uid2))"
> there will be problems.
>
> The security labels and probably lsm's in general need to be per user
> namespace but we simply have not gotten that far. For the short term I
> will be happy when we get a minimally usable user namespace.

Note also that when Eric brought this up at the LSM mini-conf two or three
years ago, there was pretty general, strong objection to the idea.

Like Eric says, I think that'll have to wait. In the meantime, isolating
user namespace sandboxes (or containers) using simple LSM configurations
is a very good idea.

-serge
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[Message index]

		userns: targeted capabilities v5 By: serge on Thu, 17 February 2011 15:02
		[PATCH 2/9] security: Make capabilities relative to the user namespace. By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: ebiederm on Fri, 18 February 2011 03:46
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: Daniel Lezcano on Fri, 18 February 2011 23:44
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: David Howells on Wed, 23 February 2011 12:01
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: serge on Wed, 23 February 2011 13:43
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: David Howells on Wed, 23 February 2011 11:40
		Re: [PATCH 2/9] security: Make capabilities relative to the user namespace. By: David Howells on Wed, 23 February 2011 16:59
		[PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: serge on Thu, 17 February 2011 15:04
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: ebiederm on Fri, 18 February 2011 01:29
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: serge on Thu, 24 February 2011 03:24
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: akpm on Thu, 24 February 2011 05:08
		Re: [PATCH 9/9] userns: check user namespace for task->file uid equivalence checks By: Daniel Lezcano on Sat, 19 February 2011 19:22
		[PATCH 7/9] add a user namespace owner of ipc ns By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 7/9] add a user namespace owner of ipc ns By: ebiederm on Fri, 18 February 2011 03:19
		Re: [PATCH 7/9] add a user namespace owner of ipc ns By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 7/9] add a user namespace owner of ipc ns By: Daniel Lezcano on Sat, 19 February 2011 17:57
		[PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: serge on Thu, 17 February 2011 15:02
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: ebiederm on Fri, 18 February 2011 03:31
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: Daniel Lezcano on Fri, 18 February 2011 16:57
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: David Howells on Wed, 23 February 2011 17:16
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: ebiederm on Wed, 23 February 2011 21:21
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: David Howells on Wed, 23 February 2011 23:19
		Re: [PATCH 1/9] Add a user_namespace as creator/owner of uts_namespace By: ebiederm on Wed, 23 February 2011 23:54
		[PATCH 3/9] allow sethostname in a container By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 3/9] allow sethostname in a container By: ebiederm on Fri, 18 February 2011 03:05
		Re: [PATCH 3/9] allow sethostname in a container By: Daniel Lezcano on Fri, 18 February 2011 23:46
		[PATCH 4/9] allow killing tasks in your own or child userns By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: ebiederm on Fri, 18 February 2011 03:00
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: serge on Thu, 24 February 2011 00:48
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: akpm on Thu, 24 February 2011 00:54
		Re: [PATCH 4/9] allow killing tasks in your own or child userns By: Daniel Lezcano on Sat, 19 February 2011 10:55
		[PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: ebiederm on Fri, 18 February 2011 01:57
		Re: [PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: akpm on Sat, 19 February 2011 00:01
		Re: [PATCH 6/9] user namespaces: convert all capable checks in kernel/sys.c By: Daniel Lezcano on Sat, 19 February 2011 17:52
		[PATCH 5/9] Allow ptrace from non-init user namespaces By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: ebiederm on Fri, 18 February 2011 02:59
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: serge on Fri, 18 February 2011 04:36
		[PATCH] userns: ptrace: incorporate feedback from Eric By: serge on Thu, 24 February 2011 00:49
		Re: [PATCH] userns: ptrace: incorporate feedback from Eric By: akpm on Thu, 24 February 2011 00:56
		Re: [PATCH] userns: ptrace: incorporate feedback from Eric By: serge on Thu, 24 February 2011 03:15
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: akpm on Fri, 18 February 2011 23:59
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: serge on Thu, 24 February 2011 00:43
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: Daniel Lezcano on Sat, 19 February 2011 17:49
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: David Howells on Wed, 23 February 2011 17:05
		Re: [PATCH 5/9] Allow ptrace from non-init user namespaces By: David Howells on Wed, 23 February 2011 17:11
		[PATCH 8/9] user namespaces: convert several capable() calls By: serge on Thu, 17 February 2011 15:03
		Re: [PATCH 8/9] user namespaces: convert several capable() calls By: ebiederm on Fri, 18 February 2011 01:51
		Re: [PATCH 8/9] user namespaces: convert several capable() calls By: Daniel Lezcano on Sat, 19 February 2011 19:07
		Re: userns: targeted capabilities v5 By: akpm on Fri, 18 February 2011 00:21
		Re: userns: targeted capabilities v5 By: ebiederm on Fri, 18 February 2011 03:53
		Re: userns: targeted capabilities v5 By: serge on Fri, 18 February 2011 04:28
		User namespaces and keys By: David Howells on Wed, 23 February 2011 12:05
		Re: User namespaces and keys By: serge on Wed, 23 February 2011 13:58
		Re: User namespaces and keys By: ebiederm on Wed, 23 February 2011 14:46
		Re: User namespaces and keys By: David Howells on Wed, 23 February 2011 15:06
		Re: User namespaces and keys By: ebiederm on Wed, 23 February 2011 15:45
		Re: User namespaces and keys By: Serge E. Hallyn on Wed, 23 February 2011 15:53
		Re: User namespaces and keys By: Casey Schaufler on Wed, 23 February 2011 19:24
		Re: User namespaces and keys By: ebiederm on Wed, 23 February 2011 20:55
		Re: User namespaces and keys By: Casey Schaufler on Wed, 23 February 2011 21:37
		Re: User namespaces and keys By: ebiederm on Thu, 24 February 2011 06:56

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