sys/netinet/ip_ipsec.c

   1 /*-
   2  * Copyright (c) 1982, 1986, 1988, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 #include <sys/cdefs.h>
  31 __FBSDID("$FreeBSD$");
  32
  33 #include "opt_ipsec.h"
  34 #include "opt_sctp.h"
  35
  36 #include <sys/param.h>
  37 #include <sys/systm.h>
  38 #include <sys/errno.h>
  39 #include <sys/kernel.h>
  40 #include <sys/malloc.h>
  41 #include <sys/mbuf.h>
  42 #include <sys/protosw.h>
  43 #include <sys/socket.h>
  44 #include <sys/socketvar.h>
  45 #include <sys/sysctl.h>
  46
  47 #include <net/if.h>
  48 #include <net/route.h>
  49 #include <net/vnet.h>
  50
  51 #include <netinet/in.h>
  52 #include <netinet/in_systm.h>
  53 #include <netinet/in_var.h>
  54 #include <netinet/ip.h>
  55 #include <netinet/in_pcb.h>
  56 #include <netinet/ip_var.h>
  57 #include <netinet/ip_options.h>
  58 #include <netinet/ip_ipsec.h>
  59 #ifdef SCTP
  60 #include <netinet/sctp_crc32.h>
  61 #endif
  62
  63 #include <machine/in_cksum.h>
  64
  65 #ifdef IPSEC
  66 #include <netipsec/ipsec.h>
  67 #include <netipsec/xform.h>
  68 #include <netipsec/key.h>
  69 #endif /*IPSEC*/
  70
  71 extern  struct protosw inetsw[];
  72
  73 #ifdef IPSEC
  74 #ifdef IPSEC_FILTERTUNNEL
  75 static VNET_DEFINE(int, ip4_ipsec_filtertunnel) = 1;
  76 #else
  77 static VNET_DEFINE(int, ip4_ipsec_filtertunnel) = 0;
  78 #endif
  79 #define V_ip4_ipsec_filtertunnel VNET(ip4_ipsec_filtertunnel)
  80
  81 SYSCTL_DECL(_net_inet_ipsec);
  82 SYSCTL_VNET_INT(_net_inet_ipsec, OID_AUTO, filtertunnel,
  83         CTLFLAG_RW, &VNET_NAME(ip4_ipsec_filtertunnel), 0,
  84         "If set filter packets from an IPsec tunnel.");
  85 #endif /* IPSEC */
  86
  87 /*
  88  * Check if we have to jump over firewall processing for this packet.
  89  * Called from ip_input().
  90  * 1 = jump over firewall, 0 = packet goes through firewall.
  91  */
  92 int
  93 ip_ipsec_filtertunnel(struct mbuf *m)
  94 {
  95 #if defined(IPSEC)
  96
  97         /*
  98          * Bypass packet filtering for packets previously handled by IPsec.
  99          */
 100         if (!V_ip4_ipsec_filtertunnel &&
 101             m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL) != NULL)
 102                 return 1;
 103 #endif
 104         return 0;
 105 }
 106
 107 /*
 108  * Check if this packet has an active SA and needs to be dropped instead
 109  * of forwarded.
 110  * Called from ip_input().
 111  * 1 = drop packet, 0 = forward packet.
 112  */
 113 int
 114 ip_ipsec_fwd(struct mbuf *m)
 115 {
 116 #ifdef IPSEC
 117         struct m_tag *mtag;
 118         struct tdb_ident *tdbi;
 119         struct secpolicy *sp;
 120         int s, error;
 121
 122         mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
 123         s = splnet();
 124         if (mtag != NULL) {
 125                 tdbi = (struct tdb_ident *)(mtag + 1);
 126                 sp = ipsec_getpolicy(tdbi, IPSEC_DIR_INBOUND);
 127         } else {
 128                 sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_INBOUND,
 129                                            IP_FORWARDING, &error);
 130         }
 131         if (sp == NULL) {       /* NB: can happen if error */
 132                 splx(s);
 133                 /*XXX error stat???*/
 134                 DPRINTF(("ip_input: no SP for forwarding\n"));  /*XXX*/
 135                 return 1;
 136         }
 137
 138         /*
 139          * Check security policy against packet attributes.
 140          */
 141         error = ipsec_in_reject(sp, m);
 142         KEY_FREESP(&sp);
 143         splx(s);
 144         if (error) {
 145                 IPSTAT_INC(ips_cantforward);
 146                 return 1;
 147         }
 148 #endif /* IPSEC */
 149         return 0;
 150 }
 151
 152 /*
 153  * Check if protocol type doesn't have a further header and do IPSEC
 154  * decryption or reject right now.  Protocols with further headers get
 155  * their IPSEC treatment within the protocol specific processing.
 156  * Called from ip_input().
 157  * 1 = drop packet, 0 = continue processing packet.
 158  */
 159 int
 160 ip_ipsec_input(struct mbuf *m)
 161 {
 162 #ifdef IPSEC
 163         struct ip *ip = mtod(m, struct ip *);
 164         struct m_tag *mtag;
 165         struct tdb_ident *tdbi;
 166         struct secpolicy *sp;
 167         int s, error;
 168         /*
 169          * enforce IPsec policy checking if we are seeing last header.
 170          * note that we do not visit this with protocols with pcb layer
 171          * code - like udp/tcp/raw ip.
 172          */
 173         if ((inetsw[ip_protox[ip->ip_p]].pr_flags & PR_LASTHDR) != 0) {
 174                 /*
 175                  * Check if the packet has already had IPsec processing
 176                  * done.  If so, then just pass it along.  This tag gets
 177                  * set during AH, ESP, etc. input handling, before the
 178                  * packet is returned to the ip input queue for delivery.
 179                  */
 180                 mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
 181                 s = splnet();
 182                 if (mtag != NULL) {
 183                         tdbi = (struct tdb_ident *)(mtag + 1);
 184                         sp = ipsec_getpolicy(tdbi, IPSEC_DIR_INBOUND);
 185                 } else {
 186                         sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_INBOUND,
 187                                                    IP_FORWARDING, &error);
 188                 }
 189                 if (sp != NULL) {
 190                         /*
 191                          * Check security policy against packet attributes.
 192                          */
 193                         error = ipsec_in_reject(sp, m);
 194                         KEY_FREESP(&sp);
 195                 } else {
 196                         /* XXX error stat??? */
 197                         error = EINVAL;
 198                         DPRINTF(("ip_input: no SP, packet discarded\n"));/*XXX*/
 199                         return 1;
 200                 }
 201                 splx(s);
 202                 if (error)
 203                         return 1;
 204         }
 205 #endif /* IPSEC */
 206         return 0;
 207 }
 208
 209 /*
 210  * Compute the MTU for a forwarded packet that gets IPSEC encapsulated.
 211  * Called from ip_forward().
 212  * Returns MTU suggestion for ICMP needfrag reply.
 213  */
 214 int
 215 ip_ipsec_mtu(struct mbuf *m, int mtu)
 216 {
 217         /*
 218          * If the packet is routed over IPsec tunnel, tell the
 219          * originator the tunnel MTU.
 220          *      tunnel MTU = if MTU - sizeof(IP) - ESP/AH hdrsiz
 221          * XXX quickhack!!!
 222          */
 223         struct secpolicy *sp = NULL;
 224         int ipsecerror;
 225         int ipsechdr;
 226         struct route *ro;
 227         sp = ipsec_getpolicybyaddr(m,
 228                                    IPSEC_DIR_OUTBOUND,
 229                                    IP_FORWARDING,
 230                                    &ipsecerror);
 231         if (sp != NULL) {
 232                 /* count IPsec header size */
 233                 ipsechdr = ipsec_hdrsiz(m, IPSEC_DIR_OUTBOUND, NULL);
 234
 235                 /*
 236                  * find the correct route for outer IPv4
 237                  * header, compute tunnel MTU.
 238                  */
 239                 if (sp->req != NULL &&
 240                     sp->req->sav != NULL &&
 241                     sp->req->sav->sah != NULL) {
 242                         ro = &sp->req->sav->sah->route_cache.sa_route;
 243                         if (ro->ro_rt && ro->ro_rt->rt_ifp) {
 244                                 mtu =
 245                                     ro->ro_rt->rt_rmx.rmx_mtu ?
 246                                     ro->ro_rt->rt_rmx.rmx_mtu :
 247                                     ro->ro_rt->rt_ifp->if_mtu;
 248                                 mtu -= ipsechdr;
 249                         }
 250                 }
 251                 KEY_FREESP(&sp);
 252         }
 253         return mtu;
 254 }
 255
 256 /*
 257  *
 258  * Called from ip_output().
 259  * 1 = drop packet, 0 = continue processing packet,
 260  * -1 = packet was reinjected and stop processing packet
 261  */
 262 int
 263 ip_ipsec_output(struct mbuf **m, struct inpcb *inp, int *flags, int *error)
 264 {
 265 #ifdef IPSEC
 266         struct secpolicy *sp = NULL;
 267         struct ip *ip = mtod(*m, struct ip *);
 268         struct tdb_ident *tdbi;
 269         struct m_tag *mtag;
 270         int s;
 271         /*
 272          * Check the security policy (SP) for the packet and, if
 273          * required, do IPsec-related processing.  There are two
 274          * cases here; the first time a packet is sent through
 275          * it will be untagged and handled by ipsec4_checkpolicy.
 276          * If the packet is resubmitted to ip_output (e.g. after
 277          * AH, ESP, etc. processing), there will be a tag to bypass
 278          * the lookup and related policy checking.
 279          */
 280         mtag = m_tag_find(*m, PACKET_TAG_IPSEC_PENDING_TDB, NULL);
 281         s = splnet();
 282         if (mtag != NULL) {
 283                 tdbi = (struct tdb_ident *)(mtag + 1);
 284                 sp = ipsec_getpolicy(tdbi, IPSEC_DIR_OUTBOUND);
 285                 if (sp == NULL)
 286                         *error = -EINVAL;       /* force silent drop */
 287                 m_tag_delete(*m, mtag);
 288         } else {
 289                 sp = ipsec4_checkpolicy(*m, IPSEC_DIR_OUTBOUND, *flags,
 290                                         error, inp);
 291         }
 292         /*
 293          * There are four return cases:
 294          *    sp != NULL                    apply IPsec policy
 295          *    sp == NULL, error == 0        no IPsec handling needed
 296          *    sp == NULL, error == -EINVAL  discard packet w/o error
 297          *    sp == NULL, error != 0        discard packet, report error
 298          */
 299         if (sp != NULL) {
 300                 /* Loop detection, check if ipsec processing already done */
 301                 KASSERT(sp->req != NULL, ("ip_output: no ipsec request"));
 302                 for (mtag = m_tag_first(*m); mtag != NULL;
 303                      mtag = m_tag_next(*m, mtag)) {
 304                         if (mtag->m_tag_cookie != MTAG_ABI_COMPAT)
 305                                 continue;
 306                         if (mtag->m_tag_id != PACKET_TAG_IPSEC_OUT_DONE &&
 307                             mtag->m_tag_id != PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED)
 308                                 continue;
 309                         /*
 310                          * Check if policy has an SA associated with it.
 311                          * This can happen when an SP has yet to acquire
 312                          * an SA; e.g. on first reference.  If it occurs,
 313                          * then we let ipsec4_process_packet do its thing.
 314                          */
 315                         if (sp->req->sav == NULL)
 316                                 break;
 317                         tdbi = (struct tdb_ident *)(mtag + 1);
 318                         if (tdbi->spi == sp->req->sav->spi &&
 319                             tdbi->proto == sp->req->sav->sah->saidx.proto &&
 320                             bcmp(&tdbi->dst, &sp->req->sav->sah->saidx.dst,
 321                                  sizeof (union sockaddr_union)) == 0) {
 322                                 /*
 323                                  * No IPsec processing is needed, free
 324                                  * reference to SP.
 325                                  *
 326                                  * NB: null pointer to avoid free at
 327                                  *     done: below.
 328                                  */
 329                                 KEY_FREESP(&sp), sp = NULL;
 330                                 splx(s);
 331                                 goto done;
 332                         }
 333                 }
 334
 335                 /*
 336                  * Do delayed checksums now because we send before
 337                  * this is done in the normal processing path.
 338                  */
 339                 if ((*m)->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
 340                         in_delayed_cksum(*m);
 341                         (*m)->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
 342                 }
 343 #ifdef SCTP
 344                 if ((*m)->m_pkthdr.csum_flags & CSUM_SCTP) {
 345                         sctp_delayed_cksum(*m, (uint32_t)(ip->ip_hl << 2));
 346                         (*m)->m_pkthdr.csum_flags &= ~CSUM_SCTP;
 347                 }
 348 #endif
 349                 ip->ip_len = htons(ip->ip_len);
 350                 ip->ip_off = htons(ip->ip_off);
 351
 352                 /* NB: callee frees mbuf */
 353                 *error = ipsec4_process_packet(*m, sp->req, *flags, 0);
 354                 if (*error == EJUSTRETURN) {
 355                         /*
 356                          * We had a SP with a level of 'use' and no SA. We
 357                          * will just continue to process the packet without
 358                          * IPsec processing and return without error.
 359                          */
 360                         *error = 0;
 361                         ip->ip_len = ntohs(ip->ip_len);
 362                         ip->ip_off = ntohs(ip->ip_off);
 363                         goto done;
 364                 }
 365                 /*
 366                  * Preserve KAME behaviour: ENOENT can be returned
 367                  * when an SA acquire is in progress.  Don't propagate
 368                  * this to user-level; it confuses applications.
 369                  *
 370                  * XXX this will go away when the SADB is redone.
 371                  */
 372                 if (*error == ENOENT)
 373                         *error = 0;
 374                 splx(s);
 375                 goto reinjected;
 376         } else {        /* sp == NULL */
 377                 splx(s);
 378
 379                 if (*error != 0) {
 380                         /*
 381                          * Hack: -EINVAL is used to signal that a packet
 382                          * should be silently discarded.  This is typically
 383                          * because we asked key management for an SA and
 384                          * it was delayed (e.g. kicked up to IKE).
 385                          */
 386                         if (*error == -EINVAL)
 387                                 *error = 0;
 388                         goto bad;
 389                 } else {
 390                         /* No IPsec processing for this packet. */
 391                 }
 392         }
 393 done:
 394         if (sp != NULL)
 395                 KEY_FREESP(&sp);
 396         return 0;
 397 reinjected:
 398         if (sp != NULL)
 399                 KEY_FREESP(&sp);
 400         return -1;
 401 bad:
 402         if (sp != NULL)
 403                 KEY_FREESP(&sp);
 404         return 1;
 405 #endif /* IPSEC */
 406         return 0;
 407 }