kernel-ark/security/keys/sysctl.c
David Howells f36f8c75ae KEYS: Add per-user_namespace registers for persistent per-UID kerberos caches
Add support for per-user_namespace registers of persistent per-UID kerberos
caches held within the kernel.

This allows the kerberos cache to be retained beyond the life of all a user's
processes so that the user's cron jobs can work.

The kerberos cache is envisioned as a keyring/key tree looking something like:

	struct user_namespace
	  \___ .krb_cache keyring		- The register
		\___ _krb.0 keyring		- Root's Kerberos cache
		\___ _krb.5000 keyring		- User 5000's Kerberos cache
		\___ _krb.5001 keyring		- User 5001's Kerberos cache
			\___ tkt785 big_key	- A ccache blob
			\___ tkt12345 big_key	- Another ccache blob

Or possibly:

	struct user_namespace
	  \___ .krb_cache keyring		- The register
		\___ _krb.0 keyring		- Root's Kerberos cache
		\___ _krb.5000 keyring		- User 5000's Kerberos cache
		\___ _krb.5001 keyring		- User 5001's Kerberos cache
			\___ tkt785 keyring	- A ccache
				\___ krbtgt/REDHAT.COM@REDHAT.COM big_key
				\___ http/REDHAT.COM@REDHAT.COM user
				\___ afs/REDHAT.COM@REDHAT.COM user
				\___ nfs/REDHAT.COM@REDHAT.COM user
				\___ krbtgt/KERNEL.ORG@KERNEL.ORG big_key
				\___ http/KERNEL.ORG@KERNEL.ORG big_key

What goes into a particular Kerberos cache is entirely up to userspace.  Kernel
support is limited to giving you the Kerberos cache keyring that you want.

The user asks for their Kerberos cache by:

	krb_cache = keyctl_get_krbcache(uid, dest_keyring);

The uid is -1 or the user's own UID for the user's own cache or the uid of some
other user's cache (requires CAP_SETUID).  This permits rpc.gssd or whatever to
mess with the cache.

The cache returned is a keyring named "_krb.<uid>" that the possessor can read,
search, clear, invalidate, unlink from and add links to.  Active LSMs get a
chance to rule on whether the caller is permitted to make a link.

Each uid's cache keyring is created when it first accessed and is given a
timeout that is extended each time this function is called so that the keyring
goes away after a while.  The timeout is configurable by sysctl but defaults to
three days.

Each user_namespace struct gets a lazily-created keyring that serves as the
register.  The cache keyrings are added to it.  This means that standard key
search and garbage collection facilities are available.

The user_namespace struct's register goes away when it does and anything left
in it is then automatically gc'd.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Simo Sorce <simo@redhat.com>
cc: Serge E. Hallyn <serge.hallyn@ubuntu.com>
cc: Eric W. Biederman <ebiederm@xmission.com>
2013-09-24 10:35:19 +01:00

77 lines
1.8 KiB
C

/* Key management controls
*
* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/key.h>
#include <linux/sysctl.h>
#include "internal.h"
static const int zero, one = 1, max = INT_MAX;
ctl_table key_sysctls[] = {
{
.procname = "maxkeys",
.data = &key_quota_maxkeys,
.maxlen = sizeof(unsigned),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *) &one,
.extra2 = (void *) &max,
},
{
.procname = "maxbytes",
.data = &key_quota_maxbytes,
.maxlen = sizeof(unsigned),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *) &one,
.extra2 = (void *) &max,
},
{
.procname = "root_maxkeys",
.data = &key_quota_root_maxkeys,
.maxlen = sizeof(unsigned),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *) &one,
.extra2 = (void *) &max,
},
{
.procname = "root_maxbytes",
.data = &key_quota_root_maxbytes,
.maxlen = sizeof(unsigned),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *) &one,
.extra2 = (void *) &max,
},
{
.procname = "gc_delay",
.data = &key_gc_delay,
.maxlen = sizeof(unsigned),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *) &zero,
.extra2 = (void *) &max,
},
#ifdef CONFIG_PERSISTENT_KEYRINGS
{
.procname = "persistent_keyring_expiry",
.data = &persistent_keyring_expiry,
.maxlen = sizeof(unsigned),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *) &zero,
.extra2 = (void *) &max,
},
#endif
{ }
};