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;
  81         u32 sel_sid;
  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         else
  92                 /*
  93                  * All flows should be treated as polmatch'ing an
  94                  * otherwise applicable "non-labeled" policy. This
  95                  * would prevent inadvertent "leaks".
  96                  */
  97                 return 0;
  98
  99         rc = avc_has_perm(fl_secid, sel_sid, SECCLASS_ASSOCIATION,
 100                           ASSOCIATION__POLMATCH,
 101                           NULL);
 102
 103         if (rc == -EACCES)
 104                 rc = -ESRCH;
 105
 106         return rc;
 107 }
 108
 109 /*
 110  * LSM hook implementation that authorizes that a state matches
 111  * the given policy, flow combo.
 112  */
 113
 114 int selinux_xfrm_state_pol_flow_match(struct xfrm_state *x, struct xfrm_policy *xp,
 115                         struct flowi *fl)
 116 {
 117         u32 state_sid;
 118         u32 pol_sid;
 119         int err;
 120
 121         if (xp->security) {
 122                 if (!x->security)
 123                         /* unlabeled SA and labeled policy can't match */
 124                         return 0;
 125                 else
 126                         state_sid = x->security->ctx_sid;
 127                 pol_sid = xp->security->ctx_sid;
 128         } else
 129                 if (x->security)
 130                         /* unlabeled policy and labeled SA can't match */
 131                         return 0;
 132                 else
 133                         /* unlabeled policy and unlabeled SA match all flows */
 134                         return 1;
 135
 136         err = avc_has_perm(state_sid, pol_sid, SECCLASS_ASSOCIATION,
 137                           ASSOCIATION__POLMATCH,
 138                           NULL);
 139
 140         if (err)
 141                 return 0;
 142
 143         err = avc_has_perm(fl->secid, state_sid, SECCLASS_ASSOCIATION,
 144                           ASSOCIATION__SENDTO,
 145                           NULL)? 0:1;
 146
 147         return err;
 148 }
 149
 150 /*
 151  * LSM hook implementation that authorizes that a particular outgoing flow
 152  * can use a given security association.
 153  */
 154
 155 int selinux_xfrm_flow_state_match(struct flowi *fl, struct xfrm_state *xfrm,
 156                                   struct xfrm_policy *xp)
 157 {
 158         int rc = 0;
 159         u32 sel_sid = SECINITSID_UNLABELED;
 160         struct xfrm_sec_ctx *ctx;
 161
 162         if (!xp->security)
 163                 if (!xfrm->security)
 164                         return 1;
 165                 else
 166                         return 0;
 167         else
 168                 if (!xfrm->security)
 169                         return 0;
 170
 171         /* Context sid is either set to label or ANY_ASSOC */
 172         if ((ctx = xfrm->security)) {
 173                 if (!selinux_authorizable_ctx(ctx))
 174                         return 0;
 175
 176                 sel_sid = ctx->ctx_sid;
 177         }
 178
 179         rc = avc_has_perm(fl->secid, sel_sid, SECCLASS_ASSOCIATION,
 180                           ASSOCIATION__SENDTO,
 181                           NULL)? 0:1;
 182
 183         return rc;
 184 }
 185
 186 /*
 187  * LSM hook implementation that determines the sid for the session.
 188  */
 189
 190 int selinux_xfrm_decode_session(struct sk_buff *skb, u32 *sid, int ckall)
 191 {
 192         struct sec_path *sp;
 193
 194         *sid = SECSID_NULL;
 195
 196         if (skb == NULL)
 197                 return 0;
 198
 199         sp = skb->sp;
 200         if (sp) {
 201                 int i, sid_set = 0;
 202
 203                 for (i = sp->len-1; i >= 0; i--) {
 204                         struct xfrm_state *x = sp->xvec[i];
 205                         if (selinux_authorizable_xfrm(x)) {
 206                                 struct xfrm_sec_ctx *ctx = x->security;
 207
 208                                 if (!sid_set) {
 209                                         *sid = ctx->ctx_sid;
 210                                         sid_set = 1;
 211
 212                                         if (!ckall)
 213                                                 break;
 214                                 }
 215                                 else if (*sid != ctx->ctx_sid)
 216                                         return -EINVAL;
 217                         }
 218                 }
 219         }
 220
 221         return 0;
 222 }
 223
 224 /*
 225  * Security blob allocation for xfrm_policy and xfrm_state
 226  * CTX does not have a meaningful value on input
 227  */
 228 static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp,
 229         struct xfrm_user_sec_ctx *uctx, struct xfrm_sec_ctx *pol, u32 sid)
 230 {
 231         int rc = 0;
 232         struct task_security_struct *tsec = current->security;
 233         struct xfrm_sec_ctx *ctx = NULL;
 234         char *ctx_str = NULL;
 235         u32 str_len;
 236         u32 ctx_sid;
 237
 238         BUG_ON(uctx && pol);
 239
 240         if (!uctx)
 241                 goto not_from_user;
 242
 243         if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX)
 244                 return -EINVAL;
 245
 246         if (uctx->ctx_len >= PAGE_SIZE)
 247                 return -ENOMEM;
 248
 249         *ctxp = ctx = kmalloc(sizeof(*ctx) +
 250                               uctx->ctx_len,
 251                               GFP_KERNEL);
 252
 253         if (!ctx)
 254                 return -ENOMEM;
 255
 256         ctx->ctx_doi = uctx->ctx_doi;
 257         ctx->ctx_len = uctx->ctx_len;
 258         ctx->ctx_alg = uctx->ctx_alg;
 259
 260         memcpy(ctx->ctx_str,
 261                uctx+1,
 262                ctx->ctx_len);
 263         rc = security_context_to_sid(ctx->ctx_str,
 264                                      ctx->ctx_len,
 265                                      &ctx->ctx_sid);
 266
 267         if (rc)
 268                 goto out;
 269
 270         /*
 271          * Does the subject have permission to set security context?
 272          */
 273         rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 274                           SECCLASS_ASSOCIATION,
 275                           ASSOCIATION__SETCONTEXT, NULL);
 276         if (rc)
 277                 goto out;
 278
 279         return rc;
 280
 281 not_from_user:
 282         if (pol) {
 283                 rc = security_sid_mls_copy(pol->ctx_sid, sid, &ctx_sid);
 284                 if (rc)
 285                         goto out;
 286         }
 287         else
 288                 ctx_sid = sid;
 289
 290         rc = security_sid_to_context(ctx_sid, &ctx_str, &str_len);
 291         if (rc)
 292                 goto out;
 293
 294         *ctxp = ctx = kmalloc(sizeof(*ctx) +
 295                               str_len,
 296                               GFP_ATOMIC);
 297
 298         if (!ctx) {
 299                 rc = -ENOMEM;
 300                 goto out;
 301         }
 302
 303         ctx->ctx_doi = XFRM_SC_DOI_LSM;
 304         ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
 305         ctx->ctx_sid = ctx_sid;
 306         ctx->ctx_len = str_len;
 307         memcpy(ctx->ctx_str,
 308                ctx_str,
 309                str_len);
 310
 311         goto out2;
 312
 313 out:
 314         *ctxp = NULL;
 315         kfree(ctx);
 316 out2:
 317         kfree(ctx_str);
 318         return rc;
 319 }
 320
 321 /*
 322  * LSM hook implementation that allocs and transfers uctx spec to
 323  * xfrm_policy.
 324  */
 325 int selinux_xfrm_policy_alloc(struct xfrm_policy *xp,
 326                 struct xfrm_user_sec_ctx *uctx, struct sock *sk)
 327 {
 328         int err;
 329         u32 sid;
 330
 331         BUG_ON(!xp);
 332         BUG_ON(uctx && sk);
 333
 334         if (sk) {
 335                 struct sk_security_struct *ssec = sk->sk_security;
 336                 sid = ssec->sid;
 337         }
 338         else
 339                 sid = SECSID_NULL;
 340
 341         err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx, NULL, sid);
 342         return err;
 343 }
 344
 345
 346 /*
 347  * LSM hook implementation that copies security data structure from old to
 348  * new for policy cloning.
 349  */
 350 int selinux_xfrm_policy_clone(struct xfrm_policy *old, struct xfrm_policy *new)
 351 {
 352         struct xfrm_sec_ctx *old_ctx, *new_ctx;
 353
 354         old_ctx = old->security;
 355
 356         if (old_ctx) {
 357                 new_ctx = new->security = kmalloc(sizeof(*new_ctx) +
 358                                                   old_ctx->ctx_len,
 359                                                   GFP_KERNEL);
 360
 361                 if (!new_ctx)
 362                         return -ENOMEM;
 363
 364                 memcpy(new_ctx, old_ctx, sizeof(*new_ctx));
 365                 memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len);
 366         }
 367         return 0;
 368 }
 369
 370 /*
 371  * LSM hook implementation that frees xfrm_policy security information.
 372  */
 373 void selinux_xfrm_policy_free(struct xfrm_policy *xp)
 374 {
 375         struct xfrm_sec_ctx *ctx = xp->security;
 376         if (ctx)
 377                 kfree(ctx);
 378 }
 379
 380 /*
 381  * LSM hook implementation that authorizes deletion of labeled policies.
 382  */
 383 int selinux_xfrm_policy_delete(struct xfrm_policy *xp)
 384 {
 385         struct task_security_struct *tsec = current->security;
 386         struct xfrm_sec_ctx *ctx = xp->security;
 387         int rc = 0;
 388
 389         if (ctx)
 390                 rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 391                                   SECCLASS_ASSOCIATION,
 392                                   ASSOCIATION__SETCONTEXT, NULL);
 393
 394         return rc;
 395 }
 396
 397 /*
 398  * LSM hook implementation that allocs and transfers sec_ctx spec to
 399  * xfrm_state.
 400  */
 401 int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx,
 402                 struct xfrm_sec_ctx *pol, u32 secid)
 403 {
 404         int err;
 405
 406         BUG_ON(!x);
 407
 408         err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, pol, secid);
 409         return err;
 410 }
 411
 412 /*
 413  * LSM hook implementation that frees xfrm_state security information.
 414  */
 415 void selinux_xfrm_state_free(struct xfrm_state *x)
 416 {
 417         struct xfrm_sec_ctx *ctx = x->security;
 418         if (ctx)
 419                 kfree(ctx);
 420 }
 421
 422 /*
 423  * SELinux internal function to retrieve the context of a connected
 424  * (sk->sk_state == TCP_ESTABLISHED) TCP socket based on its security
 425  * association used to connect to the remote socket.
 426  *
 427  * Retrieve via getsockopt SO_PEERSEC.
 428  */
 429 u32 selinux_socket_getpeer_stream(struct sock *sk)
 430 {
 431         struct dst_entry *dst, *dst_test;
 432         u32 peer_sid = SECSID_NULL;
 433
 434         if (sk->sk_state != TCP_ESTABLISHED)
 435                 goto out;
 436
 437         dst = sk_dst_get(sk);
 438         if (!dst)
 439                 goto out;
 440
 441         for (dst_test = dst; dst_test != 0;
 442              dst_test = dst_test->child) {
 443                 struct xfrm_state *x = dst_test->xfrm;
 444
 445                 if (x && selinux_authorizable_xfrm(x)) {
 446                         struct xfrm_sec_ctx *ctx = x->security;
 447                         peer_sid = ctx->ctx_sid;
 448                         break;
 449                 }
 450         }
 451         dst_release(dst);
 452
 453 out:
 454         return peer_sid;
 455 }
 456
 457 /*
 458  * SELinux internal function to retrieve the context of a UDP packet
 459  * based on its security association used to connect to the remote socket.
 460  *
 461  * Retrieve via setsockopt IP_PASSSEC and recvmsg with control message
 462  * type SCM_SECURITY.
 463  */
 464 u32 selinux_socket_getpeer_dgram(struct sk_buff *skb)
 465 {
 466         struct sec_path *sp;
 467
 468         if (skb == NULL)
 469                 return SECSID_NULL;
 470
 471         if (skb->sk->sk_protocol != IPPROTO_UDP)
 472                 return SECSID_NULL;
 473
 474         sp = skb->sp;
 475         if (sp) {
 476                 int i;
 477
 478                 for (i = sp->len-1; i >= 0; i--) {
 479                         struct xfrm_state *x = sp->xvec[i];
 480                         if (selinux_authorizable_xfrm(x)) {
 481                                 struct xfrm_sec_ctx *ctx = x->security;
 482                                 return ctx->ctx_sid;
 483                         }
 484                 }
 485         }
 486
 487         return SECSID_NULL;
 488 }
 489
 490  /*
 491   * LSM hook implementation that authorizes deletion of labeled SAs.
 492   */
 493 int selinux_xfrm_state_delete(struct xfrm_state *x)
 494 {
 495         struct task_security_struct *tsec = current->security;
 496         struct xfrm_sec_ctx *ctx = x->security;
 497         int rc = 0;
 498
 499         if (ctx)
 500                 rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 501                                   SECCLASS_ASSOCIATION,
 502                                   ASSOCIATION__SETCONTEXT, NULL);
 503
 504         return rc;
 505 }
 506
 507 /*
 508  * LSM hook that controls access to unlabelled packets.  If
 509  * a xfrm_state is authorizable (defined by macro) then it was
 510  * already authorized by the IPSec process.  If not, then
 511  * we need to check for unlabelled access since this may not have
 512  * gone thru the IPSec process.
 513  */
 514 int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb,
 515                                 struct avc_audit_data *ad)
 516 {
 517         int i, rc = 0;
 518         struct sec_path *sp;
 519         u32 sel_sid = SECINITSID_UNLABELED;
 520
 521         sp = skb->sp;
 522
 523         if (sp) {
 524                 for (i = 0; i < sp->len; i++) {
 525                         struct xfrm_state *x = sp->xvec[i];
 526
 527                         if (x && selinux_authorizable_xfrm(x)) {
 528                                 struct xfrm_sec_ctx *ctx = x->security;
 529                                 sel_sid = ctx->ctx_sid;
 530                                 break;
 531                         }
 532                 }
 533         }
 534
 535         rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION,
 536                           ASSOCIATION__RECVFROM, ad);
 537
 538         return rc;
 539 }
 540
 541 /*
 542  * POSTROUTE_LAST hook's XFRM processing:
 543  * If we have no security association, then we need to determine
 544  * whether the socket is allowed to send to an unlabelled destination.
 545  * If we do have a authorizable security association, then it has already been
 546  * checked in xfrm_policy_lookup hook.
 547  */
 548 int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
 549                                         struct avc_audit_data *ad)
 550 {
 551         struct dst_entry *dst;
 552         int rc = 0;
 553
 554         dst = skb->dst;
 555
 556         if (dst) {
 557                 struct dst_entry *dst_test;
 558
 559                 for (dst_test = dst; dst_test != 0;
 560                      dst_test = dst_test->child) {
 561                         struct xfrm_state *x = dst_test->xfrm;
 562
 563                         if (x && selinux_authorizable_xfrm(x))
 564                                 goto out;
 565                 }
 566         }
 567
 568         rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
 569                           ASSOCIATION__SENDTO, ad);
 570 out:
 571         return rc;
 572 }