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 checks and/or returns the xfrm sid for the
 188  * incoming packet.
 189  */
 190
 191 int selinux_xfrm_decode_session(struct sk_buff *skb, u32 *sid, int ckall)
 192 {
 193         struct sec_path *sp;
 194
 195         *sid = SECSID_NULL;
 196
 197         if (skb == NULL)
 198                 return 0;
 199
 200         sp = skb->sp;
 201         if (sp) {
 202                 int i, sid_set = 0;
 203
 204                 for (i = sp->len-1; i >= 0; i--) {
 205                         struct xfrm_state *x = sp->xvec[i];
 206                         if (selinux_authorizable_xfrm(x)) {
 207                                 struct xfrm_sec_ctx *ctx = x->security;
 208
 209                                 if (!sid_set) {
 210                                         *sid = ctx->ctx_sid;
 211                                         sid_set = 1;
 212
 213                                         if (!ckall)
 214                                                 break;
 215                                 }
 216                                 else if (*sid != ctx->ctx_sid)
 217                                         return -EINVAL;
 218                         }
 219                 }
 220         }
 221
 222         return 0;
 223 }
 224
 225 /*
 226  * Security blob allocation for xfrm_policy and xfrm_state
 227  * CTX does not have a meaningful value on input
 228  */
 229 static int selinux_xfrm_sec_ctx_alloc(struct xfrm_sec_ctx **ctxp,
 230         struct xfrm_user_sec_ctx *uctx, u32 sid)
 231 {
 232         int rc = 0;
 233         struct task_security_struct *tsec = current->security;
 234         struct xfrm_sec_ctx *ctx = NULL;
 235         char *ctx_str = NULL;
 236         u32 str_len;
 237
 238         BUG_ON(uctx && sid);
 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         rc = security_sid_to_context(sid, &ctx_str, &str_len);
 283         if (rc)
 284                 goto out;
 285
 286         *ctxp = ctx = kmalloc(sizeof(*ctx) +
 287                               str_len,
 288                               GFP_ATOMIC);
 289
 290         if (!ctx) {
 291                 rc = -ENOMEM;
 292                 goto out;
 293         }
 294
 295         ctx->ctx_doi = XFRM_SC_DOI_LSM;
 296         ctx->ctx_alg = XFRM_SC_ALG_SELINUX;
 297         ctx->ctx_sid = sid;
 298         ctx->ctx_len = str_len;
 299         memcpy(ctx->ctx_str,
 300                ctx_str,
 301                str_len);
 302
 303         goto out2;
 304
 305 out:
 306         *ctxp = NULL;
 307         kfree(ctx);
 308 out2:
 309         kfree(ctx_str);
 310         return rc;
 311 }
 312
 313 /*
 314  * LSM hook implementation that allocs and transfers uctx spec to
 315  * xfrm_policy.
 316  */
 317 int selinux_xfrm_policy_alloc(struct xfrm_policy *xp,
 318                 struct xfrm_user_sec_ctx *uctx)
 319 {
 320         int err;
 321
 322         BUG_ON(!xp);
 323         BUG_ON(!uctx);
 324
 325         err = selinux_xfrm_sec_ctx_alloc(&xp->security, uctx, 0);
 326         return err;
 327 }
 328
 329
 330 /*
 331  * LSM hook implementation that copies security data structure from old to
 332  * new for policy cloning.
 333  */
 334 int selinux_xfrm_policy_clone(struct xfrm_policy *old, struct xfrm_policy *new)
 335 {
 336         struct xfrm_sec_ctx *old_ctx, *new_ctx;
 337
 338         old_ctx = old->security;
 339
 340         if (old_ctx) {
 341                 new_ctx = new->security = kmalloc(sizeof(*new_ctx) +
 342                                                   old_ctx->ctx_len,
 343                                                   GFP_KERNEL);
 344
 345                 if (!new_ctx)
 346                         return -ENOMEM;
 347
 348                 memcpy(new_ctx, old_ctx, sizeof(*new_ctx));
 349                 memcpy(new_ctx->ctx_str, old_ctx->ctx_str, new_ctx->ctx_len);
 350         }
 351         return 0;
 352 }
 353
 354 /*
 355  * LSM hook implementation that frees xfrm_policy security information.
 356  */
 357 void selinux_xfrm_policy_free(struct xfrm_policy *xp)
 358 {
 359         struct xfrm_sec_ctx *ctx = xp->security;
 360         if (ctx)
 361                 kfree(ctx);
 362 }
 363
 364 /*
 365  * LSM hook implementation that authorizes deletion of labeled policies.
 366  */
 367 int selinux_xfrm_policy_delete(struct xfrm_policy *xp)
 368 {
 369         struct task_security_struct *tsec = current->security;
 370         struct xfrm_sec_ctx *ctx = xp->security;
 371         int rc = 0;
 372
 373         if (ctx)
 374                 rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 375                                   SECCLASS_ASSOCIATION,
 376                                   ASSOCIATION__SETCONTEXT, NULL);
 377
 378         return rc;
 379 }
 380
 381 /*
 382  * LSM hook implementation that allocs and transfers sec_ctx spec to
 383  * xfrm_state.
 384  */
 385 int selinux_xfrm_state_alloc(struct xfrm_state *x, struct xfrm_user_sec_ctx *uctx,
 386                 u32 secid)
 387 {
 388         int err;
 389
 390         BUG_ON(!x);
 391
 392         err = selinux_xfrm_sec_ctx_alloc(&x->security, uctx, secid);
 393         return err;
 394 }
 395
 396 /*
 397  * LSM hook implementation that frees xfrm_state security information.
 398  */
 399 void selinux_xfrm_state_free(struct xfrm_state *x)
 400 {
 401         struct xfrm_sec_ctx *ctx = x->security;
 402         if (ctx)
 403                 kfree(ctx);
 404 }
 405
 406 /*
 407  * SELinux internal function to retrieve the context of a UDP packet
 408  * based on its security association.
 409  *
 410  * Retrieve via setsockopt IP_PASSSEC and recvmsg with control message
 411  * type SCM_SECURITY.
 412  */
 413 u32 selinux_socket_getpeer_dgram(struct sk_buff *skb)
 414 {
 415         struct sec_path *sp;
 416
 417         if (skb == NULL)
 418                 return SECSID_NULL;
 419
 420         if (skb->sk->sk_protocol != IPPROTO_UDP)
 421                 return SECSID_NULL;
 422
 423         sp = skb->sp;
 424         if (sp) {
 425                 int i;
 426
 427                 for (i = sp->len-1; i >= 0; i--) {
 428                         struct xfrm_state *x = sp->xvec[i];
 429                         if (selinux_authorizable_xfrm(x)) {
 430                                 struct xfrm_sec_ctx *ctx = x->security;
 431                                 return ctx->ctx_sid;
 432                         }
 433                 }
 434         }
 435
 436         return SECSID_NULL;
 437 }
 438
 439  /*
 440   * LSM hook implementation that authorizes deletion of labeled SAs.
 441   */
 442 int selinux_xfrm_state_delete(struct xfrm_state *x)
 443 {
 444         struct task_security_struct *tsec = current->security;
 445         struct xfrm_sec_ctx *ctx = x->security;
 446         int rc = 0;
 447
 448         if (ctx)
 449                 rc = avc_has_perm(tsec->sid, ctx->ctx_sid,
 450                                   SECCLASS_ASSOCIATION,
 451                                   ASSOCIATION__SETCONTEXT, NULL);
 452
 453         return rc;
 454 }
 455
 456 /*
 457  * LSM hook that controls access to unlabelled packets.  If
 458  * a xfrm_state is authorizable (defined by macro) then it was
 459  * already authorized by the IPSec process.  If not, then
 460  * we need to check for unlabelled access since this may not have
 461  * gone thru the IPSec process.
 462  */
 463 int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb,
 464                                 struct avc_audit_data *ad)
 465 {
 466         int i, rc = 0;
 467         struct sec_path *sp;
 468         u32 sel_sid = SECINITSID_UNLABELED;
 469
 470         sp = skb->sp;
 471
 472         if (sp) {
 473                 for (i = 0; i < sp->len; i++) {
 474                         struct xfrm_state *x = sp->xvec[i];
 475
 476                         if (x && selinux_authorizable_xfrm(x)) {
 477                                 struct xfrm_sec_ctx *ctx = x->security;
 478                                 sel_sid = ctx->ctx_sid;
 479                                 break;
 480                         }
 481                 }
 482         }
 483
 484         rc = avc_has_perm(isec_sid, sel_sid, SECCLASS_ASSOCIATION,
 485                           ASSOCIATION__RECVFROM, ad);
 486
 487         return rc;
 488 }
 489
 490 /*
 491  * POSTROUTE_LAST hook's XFRM processing:
 492  * If we have no security association, then we need to determine
 493  * whether the socket is allowed to send to an unlabelled destination.
 494  * If we do have a authorizable security association, then it has already been
 495  * checked in xfrm_policy_lookup hook.
 496  */
 497 int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb,
 498                                         struct avc_audit_data *ad)
 499 {
 500         struct dst_entry *dst;
 501         int rc = 0;
 502
 503         dst = skb->dst;
 504
 505         if (dst) {
 506                 struct dst_entry *dst_test;
 507
 508                 for (dst_test = dst; dst_test != 0;
 509                      dst_test = dst_test->child) {
 510                         struct xfrm_state *x = dst_test->xfrm;
 511
 512                         if (x && selinux_authorizable_xfrm(x))
 513                                 goto out;
 514                 }
 515         }
 516
 517         rc = avc_has_perm(isec_sid, SECINITSID_UNLABELED, SECCLASS_ASSOCIATION,
 518                           ASSOCIATION__SENDTO, ad);
 519 out:
 520         return rc;
 521 }