linux/security/selinux/xfrm.c
Paul Moore d621d35e57 SELinux: Enable dynamic enable/disable of the network access checks
This patch introduces a mechanism for checking when labeled IPsec or SECMARK
are in use by keeping introducing a configuration reference counter for each
subsystem.  In the case of labeled IPsec, whenever a labeled SA or SPD entry
is created the labeled IPsec/XFRM reference count is increased and when the
entry is removed it is decreased.  In the case of SECMARK, when a SECMARK
target is created the reference count is increased and later decreased when the
target is removed.  These reference counters allow SELinux to quickly determine
if either of these subsystems are enabled.

NetLabel already has a similar mechanism which provides the netlbl_enabled()
function.

This patch also renames the selinux_relabel_packet_permission() function to
selinux_secmark_relabel_packet_permission() as the original name and
description were misleading in that they referenced a single packet label which
is not the case.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>
2008-01-30 08:17:26 +11:00

500 lines
11 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>
*
* Updated: Venkat Yekkirala <vyekkirala@TrustedCS.com>
*
* Granular IPSec Associations for use in MLS environments.
*
* Copyright (C) 2005 International Business Machines Corporation
* Copyright (C) 2006 Trusted Computer Solutions, Inc.
*
* 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/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 <asm/atomic.h>
#include "avc.h"
#include "objsec.h"
#include "xfrm.h"
/* Labeled XFRM instance counter */
atomic_t selinux_xfrm_refcount = ATOMIC_INIT(0);
/*
* 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 flow can use
* a xfrm policy rule.
*/
int selinux_xfrm_policy_lookup(struct xfrm_policy *xp, u32 fl_secid, u8 dir)
{
int rc;
u32 sel_sid;
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;
}
else
/*
* All flows should be treated as polmatch'ing an
* otherwise applicable "non-labeled" policy. This
* would prevent inadvertent "leaks".
*/
return 0;
rc = avc_has_perm(fl_secid, sel_sid, SECCLASS_ASSOCIATION,
ASSOCIATION__POLMATCH,
NULL);
if (rc == -EACCES)
rc = -ESRCH;
return rc;
}
/*
* LSM hook implementation that authorizes that a state matches
* the given policy, flow combo.
*/
int selinux_xfrm_state_pol_flow_match(struct xfrm_state *x, struct xfrm_policy *xp,
struct flowi *fl)
{
u32 state_sid;
int rc;
if (!xp->security)
if (x->security)
/* unlabeled policy and labeled SA can't match */
return 0;
else
/* unlabeled policy and unlabeled SA match all flows */
return 1;
else
if (!x->security)
/* unlabeled SA and labeled policy can't match */
return 0;
else
if (!selinux_authorizable_xfrm(x))
/* Not a SELinux-labeled SA */
return 0;
state_sid = x->security->ctx_sid;
if (fl->secid != state_sid)
return 0;
rc = avc_has_perm(fl->secid, state_sid, SECCLASS_ASSOCIATION,
ASSOCIATION__SENDTO,
NULL)? 0:1;
/*
* We don't need a separate SA Vs. policy polmatch check
* since the SA is now of the same label as the flow and
* a flow Vs. policy polmatch check had already happened
* in selinux_xfrm_policy_lookup() above.
*/
return rc;
}
/*
* LSM hook implementation that checks and/or returns the xfrm sid for the
* incoming packet.
*/
int selinux_xfrm_decode_session(struct sk_buff *skb, u32 *sid, int ckall)
{
struct sec_path *sp;
*sid = SECSID_NULL;
if (skb == NULL)
return 0;
sp = skb->sp;
if (sp) {
int i, sid_set = 0;
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;
if (!sid_set) {
*sid = ctx->ctx_sid;
sid_set = 1;
if (!ckall)
break;
}
else if (*sid != ctx->ctx_sid)
return -EINVAL;
}
}
}
return 0;
}
/*
* 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, u32 sid)
{
int rc = 0;
struct task_security_struct *tsec = current->security;
struct xfrm_sec_ctx *ctx = NULL;
char *ctx_str = NULL;
u32 str_len;
BUG_ON(uctx && sid);
if (!uctx)
goto not_from_user;
if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX)
return -EINVAL;
str_len = uctx->ctx_len;
if (str_len >= PAGE_SIZE)
return -ENOMEM;
*ctxp = ctx = kmalloc(sizeof(*ctx) +
str_len + 1,
GFP_KERNEL);
if (!ctx)
return -ENOMEM;
ctx->ctx_doi = uctx->ctx_doi;
ctx->ctx_len = str_len;
ctx->ctx_alg = uctx->ctx_alg;
memcpy(ctx->ctx_str,
uctx+1,
str_len);
ctx->ctx_str[str_len] = 0;
rc = security_context_to_sid(ctx->ctx_str,
str_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;
not_from_user:
rc = security_sid_to_context(sid, &ctx_str, &str_len);
if (rc)
goto out;
*ctxp = ctx = kmalloc(sizeof(*ctx) +
str_len,
GFP_ATOMIC);
if (!ctx) {
rc = -ENOMEM;
goto out;
}
ctx->ctx_doi = XFRM_SC_DOI_LSM;
ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
ctx->ctx_sid = sid;
ctx->ctx_len = str_len;
memcpy(ctx->ctx_str,
ctx_str,
str_len);
goto out2;
out:
*ctxp = NULL;
kfree(ctx);
out2:
kfree(ctx_str);
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);
BUG_ON(!uctx);
err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx, 0);
if (err == 0)
atomic_inc(&selinux_xfrm_refcount);
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);
if (rc == 0)
atomic_dec(&selinux_xfrm_refcount);
}
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,
u32 secid)
{
int err;
BUG_ON(!x);
err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, secid);
if (err == 0)
atomic_inc(&selinux_xfrm_refcount);
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);
}
/*
* 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);
if (rc == 0)
atomic_dec(&selinux_xfrm_refcount);
}
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,
struct avc_audit_data *ad)
{
int i, rc = 0;
struct sec_path *sp;
u32 sel_sid = SECINITSID_UNLABELED;
sp = skb->sp;
if (sp) {
for (i = 0; i < sp->len; i++) {
struct xfrm_state *x = sp->xvec[i];
if (x && selinux_authorizable_xfrm(x)) {
struct xfrm_sec_ctx *ctx = x->security;
sel_sid = ctx->ctx_sid;
break;
}
}
}
/*
* This check even when there's no association involved is
* intended, according to Trent Jaeger, to make sure a
* process can't engage in non-ipsec communication unless
* explicitly allowed by policy.
*/
rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION,
ASSOCIATION__RECVFROM, ad);
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 the selinux_xfrm_state_pol_flow_match hook above.
*/
int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
struct avc_audit_data *ad, u8 proto)
{
struct dst_entry *dst;
int rc = 0;
dst = skb->dst;
if (dst) {
struct dst_entry *dst_test;
for (dst_test = dst; dst_test != NULL;
dst_test = dst_test->child) {
struct xfrm_state *x = dst_test->xfrm;
if (x && selinux_authorizable_xfrm(x))
goto out;
}
}
switch (proto) {
case IPPROTO_AH:
case IPPROTO_ESP:
case IPPROTO_COMP:
/*
* We should have already seen this packet once before
* it underwent xfrm(s). No need to subject it to the
* unlabeled check.
*/
goto out;
default:
break;
}
/*
* This check even when there's no association involved is
* intended, according to Trent Jaeger, to make sure a
* process can't engage in non-ipsec communication unless
* explicitly allowed by policy.
*/
rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
ASSOCIATION__SENDTO, ad);
out:
return rc;
}