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, 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
 237         BUG_ON(uctx && sid);
 238
 239         if (!uctx)
 240                 goto not_from_user;
 241
 242         if (uctx->ctx_doi != XFRM_SC_ALG_SELINUX)
 243                 return -EINVAL;
 244
 245         if (uctx->ctx_len >= PAGE_SIZE)
 246                 return -ENOMEM;
 247
 248         *ctxp = ctx = kmalloc(sizeof(*ctx) +
 249                               uctx->ctx_len,
 250                               GFP_KERNEL);
 251
 252         if (!ctx)
 253                 return -ENOMEM;
 254
 255         ctx->ctx_doi = uctx->ctx_doi;
 256         ctx->ctx_len = uctx->ctx_len;
 257         ctx->ctx_alg = uctx->ctx_alg;
 258
 259         memcpy(ctx->ctx_str,
 260                uctx+1,
 261                ctx->ctx_len);
 262         rc = security_context_to_sid(ctx->ctx_str,
 263                                      ctx->ctx_len,
 264                                      &ctx->ctx_sid);
 265
 266         if (rc)
 267                 goto out;
 268
 269         /*
 270          * Does the subject have permission to set security context?
 271          */
 272         rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 273                           SECCLASS_ASSOCIATION,
 274                           ASSOCIATION__SETCONTEXT, NULL);
 275         if (rc)
 276                 goto out;
 277
 278         return rc;
 279
 280 not_from_user:
 281         rc = security_sid_to_context(sid, &ctx_str, &str_len);
 282         if (rc)
 283                 goto out;
 284
 285         *ctxp = ctx = kmalloc(sizeof(*ctx) +
 286                               str_len,
 287                               GFP_ATOMIC);
 288
 289         if (!ctx) {
 290                 rc = -ENOMEM;
 291                 goto out;
 292         }
 293
 294         ctx->ctx_doi = XFRM_SC_DOI_LSM;
 295         ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
 296         ctx->ctx_sid = sid;
 297         ctx->ctx_len = str_len;
 298         memcpy(ctx->ctx_str,
 299                ctx_str,
 300                str_len);
 301
 302         goto out2;
 303
 304 out:
 305         *ctxp = NULL;
 306         kfree(ctx);
 307 out2:
 308         kfree(ctx_str);
 309         return rc;
 310 }
 311
 312 /*
 313  * LSM hook implementation that allocs and transfers uctx spec to
 314  * xfrm_policy.
 315  */
 316 int selinux_xfrm_policy_alloc(struct xfrm_policy *xp,
 317                 struct xfrm_user_sec_ctx *uctx)
 318 {
 319         int err;
 320
 321         BUG_ON(!xp);
 322         BUG_ON(!uctx);
 323
 324         err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx, 0);
 325         return err;
 326 }
 327
 328
 329 /*
 330  * LSM hook implementation that copies security data structure from old to
 331  * new for policy cloning.
 332  */
 333 int selinux_xfrm_policy_clone(struct xfrm_policy *old, struct xfrm_policy *new)
 334 {
 335         struct xfrm_sec_ctx *old_ctx, *new_ctx;
 336
 337         old_ctx = old->security;
 338
 339         if (old_ctx) {
 340                 new_ctx = new->security = kmalloc(sizeof(*new_ctx) +
 341                                                   old_ctx->ctx_len,
 342                                                   GFP_KERNEL);
 343
 344                 if (!new_ctx)
 345                         return -ENOMEM;
 346
 347                 memcpy(new_ctx, old_ctx, sizeof(*new_ctx));
 348                 memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len);
 349         }
 350         return 0;
 351 }
 352
 353 /*
 354  * LSM hook implementation that frees xfrm_policy security information.
 355  */
 356 void selinux_xfrm_policy_free(struct xfrm_policy *xp)
 357 {
 358         struct xfrm_sec_ctx *ctx = xp->security;
 359         if (ctx)
 360                 kfree(ctx);
 361 }
 362
 363 /*
 364  * LSM hook implementation that authorizes deletion of labeled policies.
 365  */
 366 int selinux_xfrm_policy_delete(struct xfrm_policy *xp)
 367 {
 368         struct task_security_struct *tsec = current->security;
 369         struct xfrm_sec_ctx *ctx = xp->security;
 370         int rc = 0;
 371
 372         if (ctx)
 373                 rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 374                                   SECCLASS_ASSOCIATION,
 375                                   ASSOCIATION__SETCONTEXT, NULL);
 376
 377         return rc;
 378 }
 379
 380 /*
 381  * LSM hook implementation that allocs and transfers sec_ctx spec to
 382  * xfrm_state.
 383  */
 384 int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx,
 385                 u32 secid)
 386 {
 387         int err;
 388
 389         BUG_ON(!x);
 390
 391         err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, secid);
 392         return err;
 393 }
 394
 395 /*
 396  * LSM hook implementation that frees xfrm_state security information.
 397  */
 398 void selinux_xfrm_state_free(struct xfrm_state *x)
 399 {
 400         struct xfrm_sec_ctx *ctx = x->security;
 401         if (ctx)
 402                 kfree(ctx);
 403 }
 404
 405 /*
 406  * SELinux internal function to retrieve the context of a connected
 407  * (sk->sk_state == TCP_ESTABLISHED) TCP socket based on its security
 408  * association used to connect to the remote socket.
 409  *
 410  * Retrieve via getsockopt SO_PEERSEC.
 411  */
 412 u32 selinux_socket_getpeer_stream(struct sock *sk)
 413 {
 414         struct dst_entry *dst, *dst_test;
 415         u32 peer_sid = SECSID_NULL;
 416
 417         if (sk->sk_state != TCP_ESTABLISHED)
 418                 goto out;
 419
 420         dst = sk_dst_get(sk);
 421         if (!dst)
 422                 goto out;
 423
 424         for (dst_test = dst; dst_test != 0;
 425              dst_test = dst_test->child) {
 426                 struct xfrm_state *x = dst_test->xfrm;
 427
 428                 if (x && selinux_authorizable_xfrm(x)) {
 429                         struct xfrm_sec_ctx *ctx = x->security;
 430                         peer_sid = ctx->ctx_sid;
 431                         break;
 432                 }
 433         }
 434         dst_release(dst);
 435
 436 out:
 437         return peer_sid;
 438 }
 439
 440 /*
 441  * SELinux internal function to retrieve the context of a UDP packet
 442  * based on its security association used to connect to the remote socket.
 443  *
 444  * Retrieve via setsockopt IP_PASSSEC and recvmsg with control message
 445  * type SCM_SECURITY.
 446  */
 447 u32 selinux_socket_getpeer_dgram(struct sk_buff *skb)
 448 {
 449         struct sec_path *sp;
 450
 451         if (skb == NULL)
 452                 return SECSID_NULL;
 453
 454         if (skb->sk->sk_protocol != IPPROTO_UDP)
 455                 return SECSID_NULL;
 456
 457         sp = skb->sp;
 458         if (sp) {
 459                 int i;
 460
 461                 for (i = sp->len-1; i >= 0; i--) {
 462                         struct xfrm_state *x = sp->xvec[i];
 463                         if (selinux_authorizable_xfrm(x)) {
 464                                 struct xfrm_sec_ctx *ctx = x->security;
 465                                 return ctx->ctx_sid;
 466                         }
 467                 }
 468         }
 469
 470         return SECSID_NULL;
 471 }
 472
 473  /*
 474   * LSM hook implementation that authorizes deletion of labeled SAs.
 475   */
 476 int selinux_xfrm_state_delete(struct xfrm_state *x)
 477 {
 478         struct task_security_struct *tsec = current->security;
 479         struct xfrm_sec_ctx *ctx = x->security;
 480         int rc = 0;
 481
 482         if (ctx)
 483                 rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 484                                   SECCLASS_ASSOCIATION,
 485                                   ASSOCIATION__SETCONTEXT, NULL);
 486
 487         return rc;
 488 }
 489
 490 /*
 491  * LSM hook that controls access to unlabelled packets.  If
 492  * a xfrm_state is authorizable (defined by macro) then it was
 493  * already authorized by the IPSec process.  If not, then
 494  * we need to check for unlabelled access since this may not have
 495  * gone thru the IPSec process.
 496  */
 497 int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb,
 498                                 struct avc_audit_data *ad)
 499 {
 500         int i, rc = 0;
 501         struct sec_path *sp;
 502         u32 sel_sid = SECINITSID_UNLABELED;
 503
 504         sp = skb->sp;
 505
 506         if (sp) {
 507                 for (i = 0; i < sp->len; i++) {
 508                         struct xfrm_state *x = sp->xvec[i];
 509
 510                         if (x && selinux_authorizable_xfrm(x)) {
 511                                 struct xfrm_sec_ctx *ctx = x->security;
 512                                 sel_sid = ctx->ctx_sid;
 513                                 break;
 514                         }
 515                 }
 516         }
 517
 518         rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION,
 519                           ASSOCIATION__RECVFROM, ad);
 520
 521         return rc;
 522 }
 523
 524 /*
 525  * POSTROUTE_LAST hook's XFRM processing:
 526  * If we have no security association, then we need to determine
 527  * whether the socket is allowed to send to an unlabelled destination.
 528  * If we do have a authorizable security association, then it has already been
 529  * checked in xfrm_policy_lookup hook.
 530  */
 531 int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
 532                                         struct avc_audit_data *ad)
 533 {
 534         struct dst_entry *dst;
 535         int rc = 0;
 536
 537         dst = skb->dst;
 538
 539         if (dst) {
 540                 struct dst_entry *dst_test;
 541
 542                 for (dst_test = dst; dst_test != 0;
 543                      dst_test = dst_test->child) {
 544                         struct xfrm_state *x = dst_test->xfrm;
 545
 546                         if (x && selinux_authorizable_xfrm(x))
 547                                 goto out;
 548                 }
 549         }
 550
 551         rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
 552                           ASSOCIATION__SENDTO, ad);
 553 out:
 554         return rc;
 555 }