![Catherine Zhang](/assets/img/avatar_default.png)
This patch contains a fix for the previous patch that adds security contexts to IPsec policies and security associations. In the previous patch, no authorization (besides the check for write permissions to SAD and SPD) is required to delete IPsec policies and security assocations with security contexts. Thus a user authorized to change SAD and SPD can bypass the IPsec policy authorization by simply deleteing policies with security contexts. To fix this security hole, an additional authorization check is added for removing security policies and security associations with security contexts. Note that if no security context is supplied on add or present on policy to be deleted, the SELinux module allows the change unconditionally. The hook is called on deletion when no context is present, which we may want to change. At present, I left it up to the module. LSM changes: The patch adds two new LSM hooks: xfrm_policy_delete and xfrm_state_delete. The new hooks are necessary to authorize deletion of IPsec policies that have security contexts. The existing hooks xfrm_policy_free and xfrm_state_free lack the context to do the authorization, so I decided to split authorization of deletion and memory management of security data, as is typical in the LSM interface. Use: The new delete hooks are checked when xfrm_policy or xfrm_state are deleted by either the xfrm_user interface (xfrm_get_policy, xfrm_del_sa) or the pfkey interface (pfkey_spddelete, pfkey_delete). SELinux changes: The new policy_delete and state_delete functions are added. Signed-off-by: Catherine Zhang <cxzhang@watson.ibm.com> Signed-off-by: Trent Jaeger <tjaeger@cse.psu.edu> Acked-by: James Morris <jmorris@namei.org> Signed-off-by: David S. Miller <davem@davemloft.net>
405 lines
8.9 KiB
C
405 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 accept;
|
|
}
|
|
}
|
|
|
|
rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
|
|
ASSOCIATION__SENDTO, NULL);
|
|
if (rc)
|
|
goto drop;
|
|
|
|
accept:
|
|
return NF_ACCEPT;
|
|
|
|
drop:
|
|
return NF_DROP;
|
|
}
|