kernel-ark/security/selinux/xfrm.c
James Morris 4e5ab4cb85 [SECMARK]: Add new packet controls to SELinux
Add new per-packet access controls to SELinux, replacing the old
packet controls.

Packets are labeled with the iptables SECMARK and CONNSECMARK targets,
then security policy for the packets is enforced with these controls.

To allow for a smooth transition to the new controls, the old code is
still present, but not active by default.  To restore previous
behavior, the old controls may be activated at runtime by writing a
'1' to /selinux/compat_net, and also via the kernel boot parameter
selinux_compat_net.  Switching between the network control models
requires the security load_policy permission.  The old controls will
probably eventually be removed and any continued use is discouraged.

With this patch, the new secmark controls for SElinux are disabled by
default, so existing behavior is entirely preserved, and the user is
not affected at all.

It also provides a config option to enable the secmark controls by
default (which can always be overridden at boot and runtime).  It is
also noted in the kconfig help that the user will need updated
userspace if enabling secmark controls for SELinux and that they'll
probably need the SECMARK and CONNMARK targets, and conntrack protocol
helpers, although such decisions are beyond the scope of kernel
configuration.

Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-06-17 21:30:05 -07:00

399 lines
8.9 KiB
C

/*
* NSA Security-Enhanced Linux (SELinux) security module
*
* This file contains the SELinux XFRM hook function implementations.
*
* Authors: Serge Hallyn <sergeh@us.ibm.com>
* Trent Jaeger <jaegert@us.ibm.com>
*
* Copyright (C) 2005 International Business Machines Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2,
* as published by the Free Software Foundation.
*/
/*
* USAGE:
* NOTES:
* 1. Make sure to enable the following options in your kernel config:
* CONFIG_SECURITY=y
* CONFIG_SECURITY_NETWORK=y
* CONFIG_SECURITY_NETWORK_XFRM=y
* CONFIG_SECURITY_SELINUX=m/y
* ISSUES:
* 1. Caching packets, so they are not dropped during negotiation
* 2. Emulating a reasonable SO_PEERSEC across machines
* 3. Testing addition of sk_policy's with security context via setsockopt
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/security.h>
#include <linux/types.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/skbuff.h>
#include <linux/xfrm.h>
#include <net/xfrm.h>
#include <net/checksum.h>
#include <net/udp.h>
#include <asm/semaphore.h>
#include "avc.h"
#include "objsec.h"
#include "xfrm.h"
/*
* Returns true if an LSM/SELinux context
*/
static inline int selinux_authorizable_ctx(struct xfrm_sec_ctx *ctx)
{
return (ctx &&
(ctx->ctx_doi == XFRM_SC_DOI_LSM) &&
(ctx->ctx_alg == XFRM_SC_ALG_SELINUX));
}
/*
* Returns true if the xfrm contains a security blob for SELinux
*/
static inline int selinux_authorizable_xfrm(struct xfrm_state *x)
{
return selinux_authorizable_ctx(x->security);
}
/*
* LSM hook implementation that authorizes that a socket can be used
* with the corresponding xfrm_sec_ctx and direction.
*/
int selinux_xfrm_policy_lookup(struct xfrm_policy *xp, u32 sk_sid, u8 dir)
{
int rc = 0;
u32 sel_sid = SECINITSID_UNLABELED;
struct xfrm_sec_ctx *ctx;
/* Context sid is either set to label or ANY_ASSOC */
if ((ctx = xp->security)) {
if (!selinux_authorizable_ctx(ctx))
return -EINVAL;
sel_sid = ctx->ctx_sid;
}
rc = avc_has_perm(sk_sid, sel_sid, SECCLASS_ASSOCIATION,
((dir == FLOW_DIR_IN) ? ASSOCIATION__RECVFROM :
((dir == FLOW_DIR_OUT) ? ASSOCIATION__SENDTO :
(ASSOCIATION__SENDTO | ASSOCIATION__RECVFROM))),
NULL);
return rc;
}
/*
* Security blob allocation for xfrm_policy and xfrm_state
* CTX does not have a meaningful value on input
*/
static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp, struct xfrm_user_sec_ctx *uctx)
{
int rc = 0;
struct task_security_struct *tsec = current->security;
struct xfrm_sec_ctx *ctx;
BUG_ON(!uctx);
BUG_ON(uctx->ctx_doi != XFRM_SC_ALG_SELINUX);
if (uctx->ctx_len >= PAGE_SIZE)
return -ENOMEM;
*ctxp = ctx = kmalloc(sizeof(*ctx) +
uctx->ctx_len,
GFP_KERNEL);
if (!ctx)
return -ENOMEM;
ctx->ctx_doi = uctx->ctx_doi;
ctx->ctx_len = uctx->ctx_len;
ctx->ctx_alg = uctx->ctx_alg;
memcpy(ctx->ctx_str,
uctx+1,
ctx->ctx_len);
rc = security_context_to_sid(ctx->ctx_str,
ctx->ctx_len,
&ctx->ctx_sid);
if (rc)
goto out;
/*
* Does the subject have permission to set security context?
*/
rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
SECCLASS_ASSOCIATION,
ASSOCIATION__SETCONTEXT, NULL);
if (rc)
goto out;
return rc;
out:
*ctxp = NULL;
kfree(ctx);
return rc;
}
/*
* LSM hook implementation that allocs and transfers uctx spec to
* xfrm_policy.
*/
int selinux_xfrm_policy_alloc(struct xfrm_policy *xp, struct xfrm_user_sec_ctx *uctx)
{
int err;
BUG_ON(!xp);
err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx);
return err;
}
/*
* LSM hook implementation that copies security data structure from old to
* new for policy cloning.
*/
int selinux_xfrm_policy_clone(struct xfrm_policy *old, struct xfrm_policy *new)
{
struct xfrm_sec_ctx *old_ctx, *new_ctx;
old_ctx = old->security;
if (old_ctx) {
new_ctx = new->security = kmalloc(sizeof(*new_ctx) +
old_ctx->ctx_len,
GFP_KERNEL);
if (!new_ctx)
return -ENOMEM;
memcpy(new_ctx, old_ctx, sizeof(*new_ctx));
memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len);
}
return 0;
}
/*
* LSM hook implementation that frees xfrm_policy security information.
*/
void selinux_xfrm_policy_free(struct xfrm_policy *xp)
{
struct xfrm_sec_ctx *ctx = xp->security;
if (ctx)
kfree(ctx);
}
/*
* LSM hook implementation that authorizes deletion of labeled policies.
*/
int selinux_xfrm_policy_delete(struct xfrm_policy *xp)
{
struct task_security_struct *tsec = current->security;
struct xfrm_sec_ctx *ctx = xp->security;
int rc = 0;
if (ctx)
rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
SECCLASS_ASSOCIATION,
ASSOCIATION__SETCONTEXT, NULL);
return rc;
}
/*
* LSM hook implementation that allocs and transfers sec_ctx spec to
* xfrm_state.
*/
int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx)
{
int err;
BUG_ON(!x);
err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx);
return err;
}
/*
* LSM hook implementation that frees xfrm_state security information.
*/
void selinux_xfrm_state_free(struct xfrm_state *x)
{
struct xfrm_sec_ctx *ctx = x->security;
if (ctx)
kfree(ctx);
}
/*
* SELinux internal function to retrieve the context of a connected
* (sk->sk_state == TCP_ESTABLISHED) TCP socket based on its security
* association used to connect to the remote socket.
*
* Retrieve via getsockopt SO_PEERSEC.
*/
u32 selinux_socket_getpeer_stream(struct sock *sk)
{
struct dst_entry *dst, *dst_test;
u32 peer_sid = SECSID_NULL;
if (sk->sk_state != TCP_ESTABLISHED)
goto out;
dst = sk_dst_get(sk);
if (!dst)
goto out;
for (dst_test = dst; dst_test != 0;
dst_test = dst_test->child) {
struct xfrm_state *x = dst_test->xfrm;
if (x && selinux_authorizable_xfrm(x)) {
struct xfrm_sec_ctx *ctx = x->security;
peer_sid = ctx->ctx_sid;
break;
}
}
dst_release(dst);
out:
return peer_sid;
}
/*
* SELinux internal function to retrieve the context of a UDP packet
* based on its security association used to connect to the remote socket.
*
* Retrieve via setsockopt IP_PASSSEC and recvmsg with control message
* type SCM_SECURITY.
*/
u32 selinux_socket_getpeer_dgram(struct sk_buff *skb)
{
struct sec_path *sp;
if (skb == NULL)
return SECSID_NULL;
if (skb->sk->sk_protocol != IPPROTO_UDP)
return SECSID_NULL;
sp = skb->sp;
if (sp) {
int i;
for (i = sp->len-1; i >= 0; i--) {
struct xfrm_state *x = sp->xvec[i];
if (selinux_authorizable_xfrm(x)) {
struct xfrm_sec_ctx *ctx = x->security;
return ctx->ctx_sid;
}
}
}
return SECSID_NULL;
}
/*
* LSM hook implementation that authorizes deletion of labeled SAs.
*/
int selinux_xfrm_state_delete(struct xfrm_state *x)
{
struct task_security_struct *tsec = current->security;
struct xfrm_sec_ctx *ctx = x->security;
int rc = 0;
if (ctx)
rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
SECCLASS_ASSOCIATION,
ASSOCIATION__SETCONTEXT, NULL);
return rc;
}
/*
* LSM hook that controls access to unlabelled packets. If
* a xfrm_state is authorizable (defined by macro) then it was
* already authorized by the IPSec process. If not, then
* we need to check for unlabelled access since this may not have
* gone thru the IPSec process.
*/
int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb)
{
int i, rc = 0;
struct sec_path *sp;
sp = skb->sp;
if (sp) {
/*
* __xfrm_policy_check does not approve unless xfrm_policy_ok
* says that spi's match for policy and the socket.
*
* Only need to verify the existence of an authorizable sp.
*/
for (i = 0; i < sp->len; i++) {
struct xfrm_state *x = sp->xvec[i];
if (x && selinux_authorizable_xfrm(x))
goto accept;
}
}
/* check SELinux sock for unlabelled access */
rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
ASSOCIATION__RECVFROM, NULL);
if (rc)
goto drop;
accept:
return 0;
drop:
return rc;
}
/*
* POSTROUTE_LAST hook's XFRM processing:
* If we have no security association, then we need to determine
* whether the socket is allowed to send to an unlabelled destination.
* If we do have a authorizable security association, then it has already been
* checked in xfrm_policy_lookup hook.
*/
int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb)
{
struct dst_entry *dst;
int rc = 0;
dst = skb->dst;
if (dst) {
struct dst_entry *dst_test;
for (dst_test = dst; dst_test != 0;
dst_test = dst_test->child) {
struct xfrm_state *x = dst_test->xfrm;
if (x && selinux_authorizable_xfrm(x))
goto out;
}
}
rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
ASSOCIATION__SENDTO, NULL);
out:
return rc;
}