linux-stable/security/selinux/xfrm.c
Venkat Yekkirala e0d1caa7b0 [MLSXFRM]: Flow based matching of xfrm policy and state
This implements a seemless mechanism for xfrm policy selection and
state matching based on the flow sid. This also includes the necessary
SELinux enforcement pieces.

Signed-off-by: Venkat Yekkirala <vyekkirala@TrustedCS.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-09-22 14:53:24 -07:00

530 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/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 flow can use
* a xfrm policy rule.
*/
int selinux_xfrm_policy_lookup(struct xfrm_policy *xp, u32 fl_secid, 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(fl_secid, sel_sid, SECCLASS_ASSOCIATION,
ASSOCIATION__POLMATCH,
NULL);
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;
u32 pol_sid;
int err;
if (x->security)
state_sid = x->security->ctx_sid;
else
state_sid = SECINITSID_UNLABELED;
if (xp->security)
pol_sid = xp->security->ctx_sid;
else
pol_sid = SECINITSID_UNLABELED;
err = avc_has_perm(state_sid, pol_sid, SECCLASS_ASSOCIATION,
ASSOCIATION__POLMATCH,
NULL);
if (err)
return 0;
return selinux_xfrm_flow_state_match(fl, x);
}
/*
* LSM hook implementation that authorizes that a particular outgoing flow
* can use a given security association.
*/
int selinux_xfrm_flow_state_match(struct flowi *fl, struct xfrm_state *xfrm)
{
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 = xfrm->security)) {
if (!selinux_authorizable_ctx(ctx))
return 0;
sel_sid = ctx->ctx_sid;
}
rc = avc_has_perm(fl->secid, sel_sid, SECCLASS_ASSOCIATION,
ASSOCIATION__SENDTO,
NULL)? 0:1;
return rc;
}
/*
* LSM hook implementation that determines the sid for the session.
*/
int selinux_xfrm_decode_session(struct sk_buff *skb, struct flowi *fl)
{
struct sec_path *sp;
fl->secid = 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) {
fl->secid = ctx->ctx_sid;
sid_set = 1;
}
else if (fl->secid != 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, struct xfrm_sec_ctx *pol, 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;
u32 ctx_sid;
BUG_ON(uctx && pol);
if (pol)
goto from_policy;
BUG_ON(!uctx);
if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX)
return -EINVAL;
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;
from_policy:
BUG_ON(!pol);
rc = security_sid_mls_copy(pol->ctx_sid, sid, &ctx_sid);
if (rc)
goto out;
rc = security_sid_to_context(ctx_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 = ctx_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);
err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx, NULL, 0);
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,
struct xfrm_sec_ctx *pol, u32 secid)
{
int err;
BUG_ON(!x);
err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, pol, secid);
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,
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;
}
}
}
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 xfrm_policy_lookup hook.
*/
int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
struct avc_audit_data *ad)
{
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, ad);
out:
return rc;
}