security/selinux/netlabel.c

   1 /*
   2  * SELinux NetLabel Support
   3  *
   4  * This file provides the necessary glue to tie NetLabel into the SELinux
   5  * subsystem.
   6  *
   7  * Author: Paul Moore <paul.moore@hp.com>
   8  *
   9  */
  10
  11 /*
  12  * (c) Copyright Hewlett-Packard Development Company, L.P., 2007, 2008
  13  *
  14  * This program is free software;  you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License as published by
  16  * the Free Software Foundation; either version 2 of the License, or
  17  * (at your option) any later version.
  18  *
  19  * This program is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY;  without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
  22  * the GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with this program;  if not, write to the Free Software
  26  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  27  *
  28  */
  29
  30 #include <linux/spinlock.h>
  31 #include <linux/rcupdate.h>
  32 #include <linux/ip.h>
  33 #include <linux/ipv6.h>
  34 #include <net/sock.h>
  35 #include <net/netlabel.h>
  36 #include <net/ip.h>
  37 #include <net/ipv6.h>
  38
  39 #include "objsec.h"
  40 #include "security.h"
  41 #include "netlabel.h"
  42
  43 /**
  44  * selinux_netlbl_sidlookup_cached - Cache a SID lookup
  45  * @skb: the packet
  46  * @secattr: the NetLabel security attributes
  47  * @sid: the SID
  48  *
  49  * Description:
  50  * Query the SELinux security server to lookup the correct SID for the given
  51  * security attributes.  If the query is successful, cache the result to speed
  52  * up future lookups.  Returns zero on success, negative values on failure.
  53  *
  54  */
  55 static int selinux_netlbl_sidlookup_cached(struct sk_buff *skb,
  56                                            struct netlbl_lsm_secattr *secattr,
  57                                            u32 *sid)
  58 {
  59         int rc;
  60
  61         rc = security_netlbl_secattr_to_sid(secattr, sid);
  62         if (rc == 0 &&
  63             (secattr->flags & NETLBL_SECATTR_CACHEABLE) &&
  64             (secattr->flags & NETLBL_SECATTR_CACHE))
  65                 netlbl_cache_add(skb, secattr);
  66
  67         return rc;
  68 }
  69
  70 /**
  71  * selinux_netlbl_sock_genattr - Generate the NetLabel socket secattr
  72  * @sk: the socket
  73  *
  74  * Description:
  75  * Generate the NetLabel security attributes for a socket, making full use of
  76  * the socket's attribute cache.  Returns a pointer to the security attributes
  77  * on success, NULL on failure.
  78  *
  79  */
  80 static struct netlbl_lsm_secattr *selinux_netlbl_sock_genattr(struct sock *sk)
  81 {
  82         int rc;
  83         struct sk_security_struct *sksec = sk->sk_security;
  84         struct netlbl_lsm_secattr *secattr;
  85
  86         if (sksec->nlbl_secattr != NULL)
  87                 return sksec->nlbl_secattr;
  88
  89         secattr = netlbl_secattr_alloc(GFP_ATOMIC);
  90         if (secattr == NULL)
  91                 return NULL;
  92         rc = security_netlbl_sid_to_secattr(sksec->sid, secattr);
  93         if (rc != 0) {
  94                 netlbl_secattr_free(secattr);
  95                 return NULL;
  96         }
  97         sksec->nlbl_secattr = secattr;
  98
  99         return secattr;
 100 }
 101
 102 /**
 103  * selinux_netlbl_sock_setsid - Label a socket using the NetLabel mechanism
 104  * @sk: the socket to label
 105  *
 106  * Description:
 107  * Attempt to label a socket using the NetLabel mechanism.  Returns zero values
 108  * on success, negative values on failure.
 109  *
 110  */
 111 static int selinux_netlbl_sock_setsid(struct sock *sk)
 112 {
 113         int rc;
 114         struct sk_security_struct *sksec = sk->sk_security;
 115         struct netlbl_lsm_secattr *secattr;
 116
 117         if (sksec->nlbl_state != NLBL_REQUIRE)
 118                 return 0;
 119
 120         secattr = selinux_netlbl_sock_genattr(sk);
 121         if (secattr == NULL)
 122                 return -ENOMEM;
 123         rc = netlbl_sock_setattr(sk, secattr);
 124         switch (rc) {
 125         case 0:
 126                 sksec->nlbl_state = NLBL_LABELED;
 127                 break;
 128         case -EDESTADDRREQ:
 129                 sksec->nlbl_state = NLBL_REQSKB;
 130                 rc = 0;
 131                 break;
 132         }
 133
 134         return rc;
 135 }
 136
 137 /**
 138  * selinux_netlbl_cache_invalidate - Invalidate the NetLabel cache
 139  *
 140  * Description:
 141  * Invalidate the NetLabel security attribute mapping cache.
 142  *
 143  */
 144 void selinux_netlbl_cache_invalidate(void)
 145 {
 146         netlbl_cache_invalidate();
 147 }
 148
 149 /**
 150  * selinux_netlbl_err - Handle a NetLabel packet error
 151  * @skb: the packet
 152  * @error: the error code
 153  * @gateway: true if host is acting as a gateway, false otherwise
 154  *
 155  * Description:
 156  * When a packet is dropped due to a call to avc_has_perm() pass the error
 157  * code to the NetLabel subsystem so any protocol specific processing can be
 158  * done.  This is safe to call even if you are unsure if NetLabel labeling is
 159  * present on the packet, NetLabel is smart enough to only act when it should.
 160  *
 161  */
 162 void selinux_netlbl_err(struct sk_buff *skb, int error, int gateway)
 163 {
 164         netlbl_skbuff_err(skb, error, gateway);
 165 }
 166
 167 /**
 168  * selinux_netlbl_sk_security_free - Free the NetLabel fields
 169  * @sssec: the sk_security_struct
 170  *
 171  * Description:
 172  * Free all of the memory in the NetLabel fields of a sk_security_struct.
 173  *
 174  */
 175 void selinux_netlbl_sk_security_free(struct sk_security_struct *ssec)
 176 {
 177         if (ssec->nlbl_secattr != NULL)
 178                 netlbl_secattr_free(ssec->nlbl_secattr);
 179 }
 180
 181 /**
 182  * selinux_netlbl_sk_security_reset - Reset the NetLabel fields
 183  * @ssec: the sk_security_struct
 184  * @family: the socket family
 185  *
 186  * Description:
 187  * Called when the NetLabel state of a sk_security_struct needs to be reset.
 188  * The caller is responsibile for all the NetLabel sk_security_struct locking.
 189  *
 190  */
 191 void selinux_netlbl_sk_security_reset(struct sk_security_struct *ssec,
 192                                       int family)
 193 {
 194         if (family == PF_INET)
 195                 ssec->nlbl_state = NLBL_REQUIRE;
 196         else
 197                 ssec->nlbl_state = NLBL_UNSET;
 198 }
 199
 200 /**
 201  * selinux_netlbl_skbuff_getsid - Get the sid of a packet using NetLabel
 202  * @skb: the packet
 203  * @family: protocol family
 204  * @type: NetLabel labeling protocol type
 205  * @sid: the SID
 206  *
 207  * Description:
 208  * Call the NetLabel mechanism to get the security attributes of the given
 209  * packet and use those attributes to determine the correct context/SID to
 210  * assign to the packet.  Returns zero on success, negative values on failure.
 211  *
 212  */
 213 int selinux_netlbl_skbuff_getsid(struct sk_buff *skb,
 214                                  u16 family,
 215                                  u32 *type,
 216                                  u32 *sid)
 217 {
 218         int rc;
 219         struct netlbl_lsm_secattr secattr;
 220
 221         if (!netlbl_enabled()) {
 222                 *sid = SECSID_NULL;
 223                 return 0;
 224         }
 225
 226         netlbl_secattr_init(&secattr);
 227         rc = netlbl_skbuff_getattr(skb, family, &secattr);
 228         if (rc == 0 && secattr.flags != NETLBL_SECATTR_NONE)
 229                 rc = selinux_netlbl_sidlookup_cached(skb, &secattr, sid);
 230         else
 231                 *sid = SECSID_NULL;
 232         *type = secattr.type;
 233         netlbl_secattr_destroy(&secattr);
 234
 235         return rc;
 236 }
 237
 238 /**
 239  * selinux_netlbl_skbuff_setsid - Set the NetLabel on a packet given a sid
 240  * @skb: the packet
 241  * @family: protocol family
 242  * @sid: the SID
 243  *
 244  * Description
 245  * Call the NetLabel mechanism to set the label of a packet using @sid.
 246  * Returns zero on auccess, negative values on failure.
 247  *
 248  */
 249 int selinux_netlbl_skbuff_setsid(struct sk_buff *skb,
 250                                  u16 family,
 251                                  u32 sid)
 252 {
 253         int rc;
 254         struct netlbl_lsm_secattr secattr_storage;
 255         struct netlbl_lsm_secattr *secattr = NULL;
 256         struct sock *sk;
 257
 258         /* if this is a locally generated packet check to see if it is already
 259          * being labeled by it's parent socket, if it is just exit */
 260         sk = skb->sk;
 261         if (sk != NULL) {
 262                 struct sk_security_struct *sksec = sk->sk_security;
 263                 if (sksec->nlbl_state != NLBL_REQSKB)
 264                         return 0;
 265                 secattr = sksec->nlbl_secattr;
 266         }
 267         if (secattr == NULL) {
 268                 secattr = &secattr_storage;
 269                 netlbl_secattr_init(secattr);
 270                 rc = security_netlbl_sid_to_secattr(sid, secattr);
 271                 if (rc != 0)
 272                         goto skbuff_setsid_return;
 273         }
 274
 275         rc = netlbl_skbuff_setattr(skb, family, secattr);
 276
 277 skbuff_setsid_return:
 278         if (secattr == &secattr_storage)
 279                 netlbl_secattr_destroy(secattr);
 280         return rc;
 281 }
 282
 283 /**
 284  * selinux_netlbl_inet_conn_established - Netlabel the newly accepted connection
 285  * @sk: the new connection
 286  *
 287  * Description:
 288  * A new connection has been established on @sk so make sure it is labeled
 289  * correctly with the NetLabel susbsystem.
 290  *
 291  */
 292 void selinux_netlbl_inet_conn_established(struct sock *sk, u16 family)
 293 {
 294         int rc;
 295         struct sk_security_struct *sksec = sk->sk_security;
 296         struct netlbl_lsm_secattr *secattr;
 297         struct inet_sock *sk_inet = inet_sk(sk);
 298         struct sockaddr_in addr;
 299
 300         if (sksec->nlbl_state != NLBL_REQUIRE)
 301                 return;
 302
 303         secattr = selinux_netlbl_sock_genattr(sk);
 304         if (secattr == NULL)
 305                 return;
 306
 307         rc = netlbl_sock_setattr(sk, secattr);
 308         switch (rc) {
 309         case 0:
 310                 sksec->nlbl_state = NLBL_LABELED;
 311                 break;
 312         case -EDESTADDRREQ:
 313                 /* no PF_INET6 support yet because we don't support any IPv6
 314                  * labeling protocols */
 315                 if (family != PF_INET) {
 316                         sksec->nlbl_state = NLBL_UNSET;
 317                         return;
 318                 }
 319
 320                 addr.sin_family = family;
 321                 addr.sin_addr.s_addr = sk_inet->daddr;
 322                 if (netlbl_conn_setattr(sk, (struct sockaddr *)&addr,
 323                                         secattr) != 0) {
 324                         /* we failed to label the connected socket (could be
 325                          * for a variety of reasons, the actual "why" isn't
 326                          * important here) so we have to go to our backup plan,
 327                          * labeling the packets individually in the netfilter
 328                          * local output hook.  this is okay but we need to
 329                          * adjust the MSS of the connection to take into
 330                          * account any labeling overhead, since we don't know
 331                          * the exact overhead at this point we'll use the worst
 332                          * case value which is 40 bytes for IPv4 */
 333                         struct inet_connection_sock *sk_conn = inet_csk(sk);
 334                         sk_conn->icsk_ext_hdr_len += 40 -
 335                                       (sk_inet->opt ? sk_inet->opt->optlen : 0);
 336                         sk_conn->icsk_sync_mss(sk, sk_conn->icsk_pmtu_cookie);
 337
 338                         sksec->nlbl_state = NLBL_REQSKB;
 339                 } else
 340                         sksec->nlbl_state = NLBL_CONNLABELED;
 341                 break;
 342         default:
 343                 /* note that we are failing to label the socket which could be
 344                  * a bad thing since it means traffic could leave the system
 345                  * without the desired labeling, however, all is not lost as
 346                  * we have a check in selinux_netlbl_inode_permission() to
 347                  * pick up the pieces that we might drop here because we can't
 348                  * return an error code */
 349                 break;
 350         }
 351 }
 352
 353 /**
 354  * selinux_netlbl_socket_post_create - Label a socket using NetLabel
 355  * @sock: the socket to label
 356  *
 357  * Description:
 358  * Attempt to label a socket using the NetLabel mechanism using the given
 359  * SID.  Returns zero values on success, negative values on failure.
 360  *
 361  */
 362 int selinux_netlbl_socket_post_create(struct socket *sock)
 363 {
 364         return selinux_netlbl_sock_setsid(sock->sk);
 365 }
 366
 367 /**
 368  * selinux_netlbl_inode_permission - Verify the socket is NetLabel labeled
 369  * @inode: the file descriptor's inode
 370  * @mask: the permission mask
 371  *
 372  * Description:
 373  * Looks at a file's inode and if it is marked as a socket protected by
 374  * NetLabel then verify that the socket has been labeled, if not try to label
 375  * the socket now with the inode's SID.  Returns zero on success, negative
 376  * values on failure.
 377  *
 378  */
 379 int selinux_netlbl_inode_permission(struct inode *inode, int mask)
 380 {
 381         int rc;
 382         struct sock *sk;
 383         struct socket *sock;
 384         struct sk_security_struct *sksec;
 385
 386         if (!S_ISSOCK(inode->i_mode) ||
 387             ((mask & (MAY_WRITE | MAY_APPEND)) == 0))
 388                 return 0;
 389         sock = SOCKET_I(inode);
 390         sk = sock->sk;
 391         if (sk == NULL)
 392                 return 0;
 393         sksec = sk->sk_security;
 394         if (sksec == NULL || sksec->nlbl_state != NLBL_REQUIRE)
 395                 return 0;
 396
 397         local_bh_disable();
 398         bh_lock_sock_nested(sk);
 399         if (likely(sksec->nlbl_state == NLBL_REQUIRE))
 400                 rc = selinux_netlbl_sock_setsid(sk);
 401         else
 402                 rc = 0;
 403         bh_unlock_sock(sk);
 404         local_bh_enable();
 405
 406         return rc;
 407 }
 408
 409 /**
 410  * selinux_netlbl_sock_rcv_skb - Do an inbound access check using NetLabel
 411  * @sksec: the sock's sk_security_struct
 412  * @skb: the packet
 413  * @family: protocol family
 414  * @ad: the audit data
 415  *
 416  * Description:
 417  * Fetch the NetLabel security attributes from @skb and perform an access check
 418  * against the receiving socket.  Returns zero on success, negative values on
 419  * error.
 420  *
 421  */
 422 int selinux_netlbl_sock_rcv_skb(struct sk_security_struct *sksec,
 423                                 struct sk_buff *skb,
 424                                 u16 family,
 425                                 struct avc_audit_data *ad)
 426 {
 427         int rc;
 428         u32 nlbl_sid;
 429         u32 perm;
 430         struct netlbl_lsm_secattr secattr;
 431
 432         if (!netlbl_enabled())
 433                 return 0;
 434
 435         netlbl_secattr_init(&secattr);
 436         rc = netlbl_skbuff_getattr(skb, family, &secattr);
 437         if (rc == 0 && secattr.flags != NETLBL_SECATTR_NONE)
 438                 rc = selinux_netlbl_sidlookup_cached(skb, &secattr, &nlbl_sid);
 439         else
 440                 nlbl_sid = SECINITSID_UNLABELED;
 441         netlbl_secattr_destroy(&secattr);
 442         if (rc != 0)
 443                 return rc;
 444
 445         switch (sksec->sclass) {
 446         case SECCLASS_UDP_SOCKET:
 447                 perm = UDP_SOCKET__RECVFROM;
 448                 break;
 449         case SECCLASS_TCP_SOCKET:
 450                 perm = TCP_SOCKET__RECVFROM;
 451                 break;
 452         default:
 453                 perm = RAWIP_SOCKET__RECVFROM;
 454         }
 455
 456         rc = avc_has_perm(sksec->sid, nlbl_sid, sksec->sclass, perm, ad);
 457         if (rc == 0)
 458                 return 0;
 459
 460         if (nlbl_sid != SECINITSID_UNLABELED)
 461                 netlbl_skbuff_err(skb, rc, 0);
 462         return rc;
 463 }
 464
 465 /**
 466  * selinux_netlbl_socket_setsockopt - Do not allow users to remove a NetLabel
 467  * @sock: the socket
 468  * @level: the socket level or protocol
 469  * @optname: the socket option name
 470  *
 471  * Description:
 472  * Check the setsockopt() call and if the user is trying to replace the IP
 473  * options on a socket and a NetLabel is in place for the socket deny the
 474  * access; otherwise allow the access.  Returns zero when the access is
 475  * allowed, -EACCES when denied, and other negative values on error.
 476  *
 477  */
 478 int selinux_netlbl_socket_setsockopt(struct socket *sock,
 479                                      int level,
 480                                      int optname)
 481 {
 482         int rc = 0;
 483         struct sock *sk = sock->sk;
 484         struct sk_security_struct *sksec = sk->sk_security;
 485         struct netlbl_lsm_secattr secattr;
 486
 487         if (level == IPPROTO_IP && optname == IP_OPTIONS &&
 488             (sksec->nlbl_state == NLBL_LABELED ||
 489              sksec->nlbl_state == NLBL_CONNLABELED)) {
 490                 netlbl_secattr_init(&secattr);
 491                 lock_sock(sk);
 492                 rc = netlbl_sock_getattr(sk, &secattr);
 493                 release_sock(sk);
 494                 if (rc == 0)
 495                         rc = -EACCES;
 496                 else if (rc == -ENOMSG)
 497                         rc = 0;
 498                 netlbl_secattr_destroy(&secattr);
 499         }
 500
 501         return rc;
 502 }
 503
 504 /**
 505  * selinux_netlbl_socket_connect - Label a client-side socket on connect
 506  * @sk: the socket to label
 507  * @addr: the destination address
 508  *
 509  * Description:
 510  * Attempt to label a connected socket with NetLabel using the given address.
 511  * Returns zero values on success, negative values on failure.
 512  *
 513  */
 514 int selinux_netlbl_socket_connect(struct sock *sk, struct sockaddr *addr)
 515 {
 516         int rc;
 517         struct sk_security_struct *sksec = sk->sk_security;
 518         struct netlbl_lsm_secattr *secattr;
 519
 520         if (sksec->nlbl_state != NLBL_REQSKB &&
 521             sksec->nlbl_state != NLBL_CONNLABELED)
 522                 return 0;
 523
 524         local_bh_disable();
 525         bh_lock_sock_nested(sk);
 526
 527         /* connected sockets are allowed to disconnect when the address family
 528          * is set to AF_UNSPEC, if that is what is happening we want to reset
 529          * the socket */
 530         if (addr->sa_family == AF_UNSPEC) {
 531                 netlbl_sock_delattr(sk);
 532                 sksec->nlbl_state = NLBL_REQSKB;
 533                 rc = 0;
 534                 goto socket_connect_return;
 535         }
 536         secattr = selinux_netlbl_sock_genattr(sk);
 537         if (secattr == NULL) {
 538                 rc = -ENOMEM;
 539                 goto socket_connect_return;
 540         }
 541         rc = netlbl_conn_setattr(sk, addr, secattr);
 542         if (rc == 0)
 543                 sksec->nlbl_state = NLBL_CONNLABELED;
 544
 545 socket_connect_return:
 546         bh_unlock_sock(sk);
 547         local_bh_enable();
 548         return rc;
 549 }