[MLSXFRM]: Flow based matching of xfrm policy and state

[linux-2.6.22.y-op.git] / security / selinux / xfrm.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;
}