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