security/selinux/xfrm.c

   1 /*
   2  *  NSA Security-Enhanced Linux (SELinux) security module
   3  *
   4  *  This file contains the SELinux XFRM hook function implementations.
   5  *
   6  *  Authors:  Serge Hallyn <sergeh@us.ibm.com>
   7  *            Trent Jaeger <jaegert@us.ibm.com>
   8  *
   9  *  Updated: Venkat Yekkirala <vyekkirala@TrustedCS.com>
  10  *
  11  *           Granular IPSec Associations for use in MLS environments.
  12  *
  13  *  Copyright (C) 2005 International Business Machines Corporation
  14  *  Copyright (C) 2006 Trusted Computer Solutions, Inc.
  15  *
  16  *      This program is free software; you can redistribute it and/or modify
  17  *      it under the terms of the GNU General Public License version 2,
  18  *      as published by the Free Software Foundation.
  19  */
  20
  21 /*
  22  * USAGE:
  23  * NOTES:
  24  *   1. Make sure to enable the following options in your kernel config:
  25  *      CONFIG_SECURITY=y
  26  *      CONFIG_SECURITY_NETWORK=y
  27  *      CONFIG_SECURITY_NETWORK_XFRM=y
  28  *      CONFIG_SECURITY_SELINUX=m/y
  29  * ISSUES:
  30  *   1. Caching packets, so they are not dropped during negotiation
  31  *   2. Emulating a reasonable SO_PEERSEC across machines
  32  *   3. Testing addition of sk_policy's with security context via setsockopt
  33  */
  34 #include <linux/module.h>
  35 #include <linux/kernel.h>
  36 #include <linux/init.h>
  37 #include <linux/security.h>
  38 #include <linux/types.h>
  39 #include <linux/netfilter.h>
  40 #include <linux/netfilter_ipv4.h>
  41 #include <linux/netfilter_ipv6.h>
  42 #include <linux/ip.h>
  43 #include <linux/tcp.h>
  44 #include <linux/skbuff.h>
  45 #include <linux/xfrm.h>
  46 #include <net/xfrm.h>
  47 #include <net/checksum.h>
  48 #include <net/udp.h>
  49 #include <asm/semaphore.h>
  50
  51 #include "avc.h"
  52 #include "objsec.h"
  53 #include "xfrm.h"
  54
  55
  56 /*
  57  * Returns true if an LSM/SELinux context
  58  */
  59 static inline int selinux_authorizable_ctx(struct xfrm_sec_ctx *ctx)
  60 {
  61         return (ctx &&
  62                 (ctx->ctx_doi == XFRM_SC_DOI_LSM) &&
  63                 (ctx->ctx_alg == XFRM_SC_ALG_SELINUX));
  64 }
  65
  66 /*
  67  * Returns true if the xfrm contains a security blob for SELinux
  68  */
  69 static inline int selinux_authorizable_xfrm(struct xfrm_state *x)
  70 {
  71         return selinux_authorizable_ctx(x->security);
  72 }
  73
  74 /*
  75  * LSM hook implementation that authorizes that a flow can use
  76  * a xfrm policy rule.
  77  */
  78 int selinux_xfrm_policy_lookup(struct xfrm_policy *xp, u32 fl_secid, u8 dir)
  79 {
  80         int rc = 0;
  81         u32 sel_sid = SECINITSID_UNLABELED;
  82         struct xfrm_sec_ctx *ctx;
  83
  84         /* Context sid is either set to label or ANY_ASSOC */
  85         if ((ctx = xp->security)) {
  86                 if (!selinux_authorizable_ctx(ctx))
  87                         return -EINVAL;
  88
  89                 sel_sid = ctx->ctx_sid;
  90         }
  91
  92         rc = avc_has_perm(fl_secid, sel_sid, SECCLASS_ASSOCIATION,
  93                           ASSOCIATION__POLMATCH,
  94                           NULL);
  95
  96         return rc;
  97 }
  98
  99 /*
 100  * LSM hook implementation that authorizes that a state matches
 101  * the given policy, flow combo.
 102  */
 103
 104 int selinux_xfrm_state_pol_flow_match(struct xfrm_state *x, struct xfrm_policy *xp,
 105                         struct flowi *fl)
 106 {
 107         u32 state_sid;
 108         u32 pol_sid;
 109         int err;
 110
 111         if (x->security)
 112                 state_sid = x->security->ctx_sid;
 113         else
 114                 state_sid = SECINITSID_UNLABELED;
 115
 116         if (xp->security)
 117                 pol_sid = xp->security->ctx_sid;
 118         else
 119                 pol_sid = SECINITSID_UNLABELED;
 120
 121         err = avc_has_perm(state_sid, pol_sid, SECCLASS_ASSOCIATION,
 122                           ASSOCIATION__POLMATCH,
 123                           NULL);
 124
 125         if (err)
 126                 return 0;
 127
 128         return selinux_xfrm_flow_state_match(fl, x);
 129 }
 130
 131 /*
 132  * LSM hook implementation that authorizes that a particular outgoing flow
 133  * can use a given security association.
 134  */
 135
 136 int selinux_xfrm_flow_state_match(struct flowi *fl, struct xfrm_state *xfrm)
 137 {
 138         int rc = 0;
 139         u32 sel_sid = SECINITSID_UNLABELED;
 140         struct xfrm_sec_ctx *ctx;
 141
 142         /* Context sid is either set to label or ANY_ASSOC */
 143         if ((ctx = xfrm->security)) {
 144                 if (!selinux_authorizable_ctx(ctx))
 145                         return 0;
 146
 147                 sel_sid = ctx->ctx_sid;
 148         }
 149
 150         rc = avc_has_perm(fl->secid, sel_sid, SECCLASS_ASSOCIATION,
 151                           ASSOCIATION__SENDTO,
 152                           NULL)? 0:1;
 153
 154         return rc;
 155 }
 156
 157 /*
 158  * LSM hook implementation that determines the sid for the session.
 159  */
 160
 161 int selinux_xfrm_decode_session(struct sk_buff *skb, u32 *sid, int ckall)
 162 {
 163         struct sec_path *sp;
 164
 165         *sid = SECSID_NULL;
 166
 167         if (skb == NULL)
 168                 return 0;
 169
 170         sp = skb->sp;
 171         if (sp) {
 172                 int i, sid_set = 0;
 173
 174                 for (i = sp->len-1; i >= 0; i--) {
 175                         struct xfrm_state *x = sp->xvec[i];
 176                         if (selinux_authorizable_xfrm(x)) {
 177                                 struct xfrm_sec_ctx *ctx = x->security;
 178
 179                                 if (!sid_set) {
 180                                         *sid = ctx->ctx_sid;
 181                                         sid_set = 1;
 182
 183                                         if (!ckall)
 184                                                 break;
 185                                 }
 186                                 else if (*sid != ctx->ctx_sid)
 187                                         return -EINVAL;
 188                         }
 189                 }
 190         }
 191
 192         return 0;
 193 }
 194
 195 /*
 196  * Security blob allocation for xfrm_policy and xfrm_state
 197  * CTX does not have a meaningful value on input
 198  */
 199 static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp,
 200         struct xfrm_user_sec_ctx *uctx, struct xfrm_sec_ctx *pol, u32 sid)
 201 {
 202         int rc = 0;
 203         struct task_security_struct *tsec = current->security;
 204         struct xfrm_sec_ctx *ctx = NULL;
 205         char *ctx_str = NULL;
 206         u32 str_len;
 207         u32 ctx_sid;
 208
 209         BUG_ON(uctx && pol);
 210
 211         if (!uctx)
 212                 goto not_from_user;
 213
 214         if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX)
 215                 return -EINVAL;
 216
 217         if (uctx->ctx_len >= PAGE_SIZE)
 218                 return -ENOMEM;
 219
 220         *ctxp = ctx = kmalloc(sizeof(*ctx) +
 221                               uctx->ctx_len,
 222                               GFP_KERNEL);
 223
 224         if (!ctx)
 225                 return -ENOMEM;
 226
 227         ctx->ctx_doi = uctx->ctx_doi;
 228         ctx->ctx_len = uctx->ctx_len;
 229         ctx->ctx_alg = uctx->ctx_alg;
 230
 231         memcpy(ctx->ctx_str,
 232                uctx+1,
 233                ctx->ctx_len);
 234         rc = security_context_to_sid(ctx->ctx_str,
 235                                      ctx->ctx_len,
 236                                      &ctx->ctx_sid);
 237
 238         if (rc)
 239                 goto out;
 240
 241         /*
 242          * Does the subject have permission to set security context?
 243          */
 244         rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 245                           SECCLASS_ASSOCIATION,
 246                           ASSOCIATION__SETCONTEXT, NULL);
 247         if (rc)
 248                 goto out;
 249
 250         return rc;
 251
 252 not_from_user:
 253         if (pol) {
 254                 rc = security_sid_mls_copy(pol->ctx_sid, sid, &ctx_sid);
 255                 if (rc)
 256                         goto out;
 257         }
 258         else
 259                 ctx_sid = sid;
 260
 261         rc = security_sid_to_context(ctx_sid, &ctx_str, &str_len);
 262         if (rc)
 263                 goto out;
 264
 265         *ctxp = ctx = kmalloc(sizeof(*ctx) +
 266                               str_len,
 267                               GFP_ATOMIC);
 268
 269         if (!ctx) {
 270                 rc = -ENOMEM;
 271                 goto out;
 272         }
 273
 274
 275         ctx->ctx_doi = XFRM_SC_DOI_LSM;
 276         ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
 277         ctx->ctx_sid = ctx_sid;
 278         ctx->ctx_len = str_len;
 279         memcpy(ctx->ctx_str,
 280                ctx_str,
 281                str_len);
 282
 283         goto out2;
 284
 285 out:
 286         *ctxp = NULL;
 287         kfree(ctx);
 288 out2:
 289         kfree(ctx_str);
 290         return rc;
 291 }
 292
 293 /*
 294  * LSM hook implementation that allocs and transfers uctx spec to
 295  * xfrm_policy.
 296  */
 297 int selinux_xfrm_policy_alloc(struct xfrm_policy *xp,
 298                 struct xfrm_user_sec_ctx *uctx, struct sock *sk)
 299 {
 300         int err;
 301         u32 sid;
 302
 303         BUG_ON(!xp);
 304         BUG_ON(uctx && sk);
 305
 306         if (sk) {
 307                 struct sk_security_struct *ssec = sk->sk_security;
 308                 sid = ssec->sid;
 309         }
 310         else
 311                 sid = SECSID_NULL;
 312
 313         err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx, NULL, sid);
 314         return err;
 315 }
 316
 317
 318 /*
 319  * LSM hook implementation that copies security data structure from old to
 320  * new for policy cloning.
 321  */
 322 int selinux_xfrm_policy_clone(struct xfrm_policy *old, struct xfrm_policy *new)
 323 {
 324         struct xfrm_sec_ctx *old_ctx, *new_ctx;
 325
 326         old_ctx = old->security;
 327
 328         if (old_ctx) {
 329                 new_ctx = new->security = kmalloc(sizeof(*new_ctx) +
 330                                                   old_ctx->ctx_len,
 331                                                   GFP_KERNEL);
 332
 333                 if (!new_ctx)
 334                         return -ENOMEM;
 335
 336                 memcpy(new_ctx, old_ctx, sizeof(*new_ctx));
 337                 memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len);
 338         }
 339         return 0;
 340 }
 341
 342 /*
 343  * LSM hook implementation that frees xfrm_policy security information.
 344  */
 345 void selinux_xfrm_policy_free(struct xfrm_policy *xp)
 346 {
 347         struct xfrm_sec_ctx *ctx = xp->security;
 348         if (ctx)
 349                 kfree(ctx);
 350 }
 351
 352 /*
 353  * LSM hook implementation that authorizes deletion of labeled policies.
 354  */
 355 int selinux_xfrm_policy_delete(struct xfrm_policy *xp)
 356 {
 357         struct task_security_struct *tsec = current->security;
 358         struct xfrm_sec_ctx *ctx = xp->security;
 359         int rc = 0;
 360
 361         if (ctx)
 362                 rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 363                                   SECCLASS_ASSOCIATION,
 364                                   ASSOCIATION__SETCONTEXT, NULL);
 365
 366         return rc;
 367 }
 368
 369 /*
 370  * LSM hook implementation that allocs and transfers sec_ctx spec to
 371  * xfrm_state.
 372  */
 373 int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx,
 374                 struct xfrm_sec_ctx *pol, u32 secid)
 375 {
 376         int err;
 377
 378         BUG_ON(!x);
 379
 380         err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, pol, secid);
 381         return err;
 382 }
 383
 384 /*
 385  * LSM hook implementation that frees xfrm_state security information.
 386  */
 387 void selinux_xfrm_state_free(struct xfrm_state *x)
 388 {
 389         struct xfrm_sec_ctx *ctx = x->security;
 390         if (ctx)
 391                 kfree(ctx);
 392 }
 393
 394 /*
 395  * SELinux internal function to retrieve the context of a connected
 396  * (sk->sk_state == TCP_ESTABLISHED) TCP socket based on its security
 397  * association used to connect to the remote socket.
 398  *
 399  * Retrieve via getsockopt SO_PEERSEC.
 400  */
 401 u32 selinux_socket_getpeer_stream(struct sock *sk)
 402 {
 403         struct dst_entry *dst, *dst_test;
 404         u32 peer_sid = SECSID_NULL;
 405
 406         if (sk->sk_state != TCP_ESTABLISHED)
 407                 goto out;
 408
 409         dst = sk_dst_get(sk);
 410         if (!dst)
 411                 goto out;
 412
 413         for (dst_test = dst; dst_test != 0;
 414              dst_test = dst_test->child) {
 415                 struct xfrm_state *x = dst_test->xfrm;
 416
 417                 if (x && selinux_authorizable_xfrm(x)) {
 418                         struct xfrm_sec_ctx *ctx = x->security;
 419                         peer_sid = ctx->ctx_sid;
 420                         break;
 421                 }
 422         }
 423         dst_release(dst);
 424
 425 out:
 426         return peer_sid;
 427 }
 428
 429 /*
 430  * SELinux internal function to retrieve the context of a UDP packet
 431  * based on its security association used to connect to the remote socket.
 432  *
 433  * Retrieve via setsockopt IP_PASSSEC and recvmsg with control message
 434  * type SCM_SECURITY.
 435  */
 436 u32 selinux_socket_getpeer_dgram(struct sk_buff *skb)
 437 {
 438         struct sec_path *sp;
 439
 440         if (skb == NULL)
 441                 return SECSID_NULL;
 442
 443         if (skb->sk->sk_protocol != IPPROTO_UDP)
 444                 return SECSID_NULL;
 445
 446         sp = skb->sp;
 447         if (sp) {
 448                 int i;
 449
 450                 for (i = sp->len-1; i >= 0; i--) {
 451                         struct xfrm_state *x = sp->xvec[i];
 452                         if (selinux_authorizable_xfrm(x)) {
 453                                 struct xfrm_sec_ctx *ctx = x->security;
 454                                 return ctx->ctx_sid;
 455                         }
 456                 }
 457         }
 458
 459         return SECSID_NULL;
 460 }
 461
 462  /*
 463   * LSM hook implementation that authorizes deletion of labeled SAs.
 464   */
 465 int selinux_xfrm_state_delete(struct xfrm_state *x)
 466 {
 467         struct task_security_struct *tsec = current->security;
 468         struct xfrm_sec_ctx *ctx = x->security;
 469         int rc = 0;
 470
 471         if (ctx)
 472                 rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 473                                   SECCLASS_ASSOCIATION,
 474                                   ASSOCIATION__SETCONTEXT, NULL);
 475
 476         return rc;
 477 }
 478
 479 /*
 480  * LSM hook that controls access to unlabelled packets.  If
 481  * a xfrm_state is authorizable (defined by macro) then it was
 482  * already authorized by the IPSec process.  If not, then
 483  * we need to check for unlabelled access since this may not have
 484  * gone thru the IPSec process.
 485  */
 486 int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb,
 487                                 struct avc_audit_data *ad)
 488 {
 489         int i, rc = 0;
 490         struct sec_path *sp;
 491         u32 sel_sid = SECINITSID_UNLABELED;
 492
 493         sp = skb->sp;
 494
 495         if (sp) {
 496                 for (i = 0; i < sp->len; i++) {
 497                         struct xfrm_state *x = sp->xvec[i];
 498
 499                         if (x && selinux_authorizable_xfrm(x)) {
 500                                 struct xfrm_sec_ctx *ctx = x->security;
 501                                 sel_sid = ctx->ctx_sid;
 502                                 break;
 503                         }
 504                 }
 505         }
 506
 507         rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION,
 508                           ASSOCIATION__RECVFROM, ad);
 509
 510         return rc;
 511 }
 512
 513 /*
 514  * POSTROUTE_LAST hook's XFRM processing:
 515  * If we have no security association, then we need to determine
 516  * whether the socket is allowed to send to an unlabelled destination.
 517  * If we do have a authorizable security association, then it has already been
 518  * checked in xfrm_policy_lookup hook.
 519  */
 520 int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
 521                                         struct avc_audit_data *ad)
 522 {
 523         struct dst_entry *dst;
 524         int rc = 0;
 525
 526         dst = skb->dst;
 527
 528         if (dst) {
 529                 struct dst_entry *dst_test;
 530
 531                 for (dst_test = dst; dst_test != 0;
 532                      dst_test = dst_test->child) {
 533                         struct xfrm_state *x = dst_test->xfrm;
 534
 535                         if (x && selinux_authorizable_xfrm(x))
 536                                 goto out;
 537                 }
 538         }
 539
 540         rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
 541                           ASSOCIATION__SENDTO, ad);
 542 out:
 543         return rc;
 544 }