linux/security/selinux
Venkat Yekkirala 5b368e61c2 IPsec: correct semantics for SELinux policy matching
Currently when an IPSec policy rule doesn't specify a security
context, it is assumed to be "unlabeled" by SELinux, and so
the IPSec policy rule fails to match to a flow that it would
otherwise match to, unless one has explicitly added an SELinux
policy rule allowing the flow to "polmatch" to the "unlabeled"
IPSec policy rules. In the absence of such an explicitly added
SELinux policy rule, the IPSec policy rule fails to match and
so the packet(s) flow in clear text without the otherwise applicable
xfrm(s) applied.

The above SELinux behavior violates the SELinux security notion of
"deny by default" which should actually translate to "encrypt by
default" in the above case.

This was first reported by Evgeniy Polyakov and the way James Morris
was seeing the problem was when connecting via IPsec to a
confined service on an SELinux box (vsftpd), which did not have the
appropriate SELinux policy permissions to send packets via IPsec.

With this patch applied, SELinux "polmatching" of flows Vs. IPSec
policy rules will only come into play when there's a explicit context
specified for the IPSec policy rule (which also means there's corresponding
SELinux policy allowing appropriate domains/flows to polmatch to this context).

Secondly, when a security module is loaded (in this case, SELinux), the
security_xfrm_policy_lookup() hook can return errors other than access denied,
such as -EINVAL.  We were not handling that correctly, and in fact
inverting the return logic and propagating a false "ok" back up to
xfrm_lookup(), which then allowed packets to pass as if they were not
associated with an xfrm policy.

The solution for this is to first ensure that errno values are
correctly propagated all the way back up through the various call chains
from security_xfrm_policy_lookup(), and handled correctly.

Then, flow_cache_lookup() is modified, so that if the policy resolver
fails (typically a permission denied via the security module), the flow
cache entry is killed rather than having a null policy assigned (which
indicates that the packet can pass freely).  This also forces any future
lookups for the same flow to consult the security module (e.g. SELinux)
for current security policy (rather than, say, caching the error on the
flow cache entry).

This patch: Fix the selinux side of things.

This makes sure SELinux polmatching of flow contexts to IPSec policy
rules comes into play only when an explicit context is associated
with the IPSec policy rule.

Also, this no longer defaults the context of a socket policy to
the context of the socket since the "no explicit context" case
is now handled properly.

Signed-off-by: Venkat Yekkirala <vyekkirala@TrustedCS.com>
Signed-off-by: James Morris <jmorris@namei.org>
2006-10-11 23:59:37 -07:00
..
include IPsec: correct semantics for SELinux policy matching 2006-10-11 23:59:37 -07:00
ss NetLabel: use SECINITSID_UNLABELED for a base SID 2006-10-11 23:59:32 -07:00
avc.c [PATCH] support for context based audit filtering 2006-05-01 06:06:24 -04:00
exports.c [PATCH] selinux: rename selinux_ctxid_to_string 2006-09-26 08:48:52 -07:00
hooks.c [PATCH] MLSXFRM: fix mis-labelling of child sockets 2006-09-29 15:58:21 -07:00
Kconfig Still more typo fixes 2006-10-03 22:36:44 +02:00
Makefile [PATCH] support for context based audit filtering 2006-05-01 06:06:24 -04:00
netif.c [PATCH] SELinux: convert to kzalloc 2005-10-30 17:37:11 -08:00
netlink.c [NETLINK]: Add "groups" argument to netlink_kernel_create 2005-08-29 16:01:11 -07:00
nlmsgtab.c Merge branch 'audit.b3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current 2006-03-25 09:24:53 -08:00
selinuxfs.c [PATCH] r/o bind mount prepwork: inc_nlink() helper 2006-10-01 00:39:30 -07:00
xfrm.c IPsec: correct semantics for SELinux policy matching 2006-10-11 23:59:37 -07:00