// SPDX-License-Identifier: GPL-2.0-only
/*
* Security-Enhanced Linux (SELinux) security module
*
* This file contains the SELinux XFRM hook function implementations.
*
* Authors: Serge Hallyn <[email protected]>
* Trent Jaeger <[email protected]>
*
* Updated: Venkat Yekkirala <[email protected]>
*
* Granular IPSec Associations for use in MLS environments.
*
* Copyright (C) 2005 International Business Machines Corporation
* Copyright (C) 2006 Trusted Computer Solutions, Inc.
*/
/*
* 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/slab.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 <linux/atomic.h>
#include "avc.h"
#include "objsec.h"
#include "xfrm.h"
/* Labeled XFRM instance counter */
atomic_t selinux_xfrm_refcount __read_mostly = ATOMIC_INIT(0);
/*
* Returns true if the context is 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);
}
/*
* Allocates a xfrm_sec_state and populates it using the supplied security
* xfrm_user_sec_ctx context.
*/
static int selinux_xfrm_alloc_user(struct xfrm_sec_ctx **ctxp,
struct xfrm_user_sec_ctx *uctx,
gfp_t gfp)
{
int rc;
struct xfrm_sec_ctx *ctx = NULL;
u32 str_len;
if (ctxp == NULL || uctx == NULL ||
uctx->ctx_doi != XFRM_SC_DOI_LSM ||
uctx->ctx_alg != XFRM_SC_ALG_SELINUX)
return -EINVAL;
str_len = uctx->ctx_len;
if (str_len >= PAGE_SIZE)
return -ENOMEM;
ctx = kmalloc(struct_size(ctx, ctx_str, str_len + 1), gfp);
if (!ctx)
return -ENOMEM;
ctx->ctx_doi = XFRM_SC_DOI_LSM;
ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
ctx->ctx_len = str_len;
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, gfp);
if (rc)
goto err;
rc = avc_has_perm(current_sid(), ctx->ctx_sid,
SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT, NULL);
if (rc)
goto err;
*ctxp = ctx;
atomic_inc(&selinux_xfrm_refcount);
return 0;
err:
kfree(ctx);
return rc;
}
/*
* Free the xfrm_sec_ctx structure.
*/
static void selinux_xfrm_free(struct xfrm_sec_ctx *ctx)
{
if (!ctx)
return;
atomic_dec(&selinux_xfrm_refcount);
kfree(ctx);
}
/*
* Authorize the deletion of a labeled SA or policy rule.
*/
static int selinux_xfrm_delete(struct xfrm_sec_ctx *ctx)
{
if (!ctx)
return 0;
return avc_has_perm(current_sid(), ctx->ctx_sid,
SECCLASS_ASSOCIATION, ASSOCIATION__SETCONTEXT,
NULL);
}
/*
* LSM hook implementation that authorizes that a flow can use a xfrm policy
* rule.
*/
int selinux_xfrm_policy_lookup(struct xfrm_sec_ctx *ctx, u32 fl_secid)
{
int rc;
/* All flows should be treated as polmatch'ing an otherwise applicable
* "non-labeled" policy. This would prevent inadvertent "leaks". */
if (!ctx)
return 0;
/* Context sid is either set to label or ANY_ASSOC */
if (!selinux_authorizable_ctx(ctx))
return -EINVAL;
rc = avc_has_perm(fl_secid, ctx->ctx_sid,
SECCLASS_ASSOCIATION, ASSOCIATION__POLMATCH, NULL);
return (rc == -EACCES ? -ESRCH : 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,
const struct flowi_common *flic)
{
u32 state_sid;
u32 flic_sid;
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;
flic_sid = flic->flowic_secid;
if (flic_sid != state_sid)
return 0;
/* 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 (avc_has_perm(flic_sid, state_sid,
SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO,
NULL) ? 0 : 1);
}
static u32 selinux_xfrm_skb_sid_egress(struct sk_buff *skb)
{
struct dst_entry *dst = skb_dst(skb);
struct xfrm_state *x;
if (dst == NULL)
return SECSID_NULL;
x = dst->xfrm;
if (x == NULL || !selinux_authorizable_xfrm(x))
return SECSID_NULL;
return x->security->ctx_sid;
}
static int selinux_xfrm_skb_sid_ingress(struct sk_buff *skb,
u32 *sid, int ckall)
{
u32 sid_session = SECSID_NULL;
struct sec_path *sp = skb_sec_path(skb);
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;
if (sid_session == SECSID_NULL) {
sid_session = ctx->ctx_sid;
if (!ckall)
goto out;
} else if (sid_session != ctx->ctx_sid) {
*sid = SECSID_NULL;
return -EINVAL;
}
}
}
}
out:
*sid = sid_session;
return 0;
}
/*
* 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)
{
if (skb == NULL) {
*sid = SECSID_NULL;
return 0;
}
return selinux_xfrm_skb_sid_ingress(skb, sid, ckall);
}
int selinux_xfrm_skb_sid(struct sk_buff *skb, u32 *sid)
{
int rc;
rc = selinux_xfrm_skb_sid_ingress(skb, sid, 0);
if (rc == 0 && *sid == SECSID_NULL)
*sid = selinux_xfrm_skb_sid_egress(skb);
return rc;
}
/*
* LSM hook implementation that allocs and transfers uctx spec to xfrm_policy.
*/
int selinux_xfrm_policy_alloc(struct xfrm_sec_ctx **ctxp,
struct xfrm_user_sec_ctx *uctx,
gfp_t gfp)
{
return selinux_xfrm_alloc_user(ctxp, uctx, gfp);
}
/*
* LSM hook implementation that copies security data structure from old to new
* for policy cloning.
*/
int selinux_xfrm_policy_clone(struct xfrm_sec_ctx *old_ctx,
struct xfrm_sec_ctx **new_ctxp)
{
struct xfrm_sec_ctx *new_ctx;
if (!old_ctx)
return 0;
new_ctx = kmemdup(old_ctx, sizeof(*old_ctx) + old_ctx->ctx_len,
GFP_ATOMIC);
if (!new_ctx)
return -ENOMEM;
atomic_inc(&selinux_xfrm_refcount);
*new_ctxp = new_ctx;
return 0;
}
/*
* LSM hook implementation that frees xfrm_sec_ctx security information.
*/
void selinux_xfrm_policy_free(struct xfrm_sec_ctx *ctx)
{
selinux_xfrm_free(ctx);
}
/*
* LSM hook implementation that authorizes deletion of labeled policies.
*/
int selinux_xfrm_policy_delete(struct xfrm_sec_ctx *ctx)
{
return selinux_xfrm_delete(ctx);
}
/*
* LSM hook implementation that allocates a xfrm_sec_state, populates it using
* the supplied security context, and assigns it to the xfrm_state.
*/
int selinux_xfrm_state_alloc(struct xfrm_state *x,
struct xfrm_user_sec_ctx *uctx)
{
return selinux_xfrm_alloc_user(&x->security, uctx, GFP_KERNEL);
}
/*
* LSM hook implementation that allocates a xfrm_sec_state and populates based
* on a secid.
*/
int selinux_xfrm_state_alloc_acquire(struct xfrm_state *x,
struct xfrm_sec_ctx *polsec, u32 secid)
{
int rc;
struct xfrm_sec_ctx *ctx;
char *ctx_str = NULL;
u32 str_len;
if (!polsec)
return 0;
if (secid == 0)
return -EINVAL;
rc = security_sid_to_context(secid, &ctx_str,
&str_len);
if (rc)
return rc;
ctx = kmalloc(struct_size(ctx, ctx_str, 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 = secid;
ctx->ctx_len = str_len;
memcpy(ctx->ctx_str, ctx_str, str_len);
x->security = ctx;
atomic_inc(&selinux_xfrm_refcount);
out:
kfree(ctx_str);
return rc;
}
/*
* LSM hook implementation that frees xfrm_state security information.
*/
void selinux_xfrm_state_free(struct xfrm_state *x)
{
selinux_xfrm_free(x->security);
}
/*
* LSM hook implementation that authorizes deletion of labeled SAs.
*/
int selinux_xfrm_state_delete(struct xfrm_state *x)
{
return selinux_xfrm_delete(x->security);
}
/*
* 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 sk_sid, struct sk_buff *skb,
struct common_audit_data *ad)
{
int i;
struct sec_path *sp = skb_sec_path(skb);
u32 peer_sid = SECINITSID_UNLABELED;
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;
peer_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. */
return avc_has_perm(sk_sid, peer_sid,
SECCLASS_ASSOCIATION, ASSOCIATION__RECVFROM, ad);
}
/*
* 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 sk_sid, struct sk_buff *skb,
struct common_audit_data *ad, u8 proto)
{
struct dst_entry *dst;
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. */
return 0;
default:
break;
}
dst = skb_dst(skb);
if (dst) {
struct dst_entry *iter;
for (iter = dst; iter != NULL; iter = xfrm_dst_child(iter)) {
struct xfrm_state *x = iter->xfrm;
if (x && selinux_authorizable_xfrm(x))
return 0;
}
}
/* 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. */
return avc_has_perm(sk_sid, SECINITSID_UNLABELED,
SECCLASS_ASSOCIATION, ASSOCIATION__SENDTO, ad);
}
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