The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/netinet/ip_ipsec.c

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    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: releng/10.4/sys/netinet/ip_ipsec.c 291355 2015-11-26 02:24:45Z gnn $");
   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/vnet.h>
   49 
   50 #include <netinet/in.h>
   51 #include <netinet/in_systm.h>
   52 #include <netinet/in_var.h>
   53 #include <netinet/ip.h>
   54 #include <netinet/in_pcb.h>
   55 #include <netinet/ip_var.h>
   56 #include <netinet/ip_options.h>
   57 #include <netinet/ip_ipsec.h>
   58 #ifdef SCTP
   59 #include <netinet/sctp_crc32.h>
   60 #endif
   61 
   62 #include <machine/in_cksum.h>
   63 
   64 #ifdef IPSEC
   65 #include <netipsec/ipsec.h>
   66 #include <netipsec/xform.h>
   67 #include <netipsec/key.h>
   68 #endif /*IPSEC*/
   69 
   70 extern  struct protosw inetsw[];
   71 
   72 #ifdef IPSEC
   73 #ifdef IPSEC_FILTERTUNNEL
   74 static VNET_DEFINE(int, ip4_ipsec_filtertunnel) = 1;
   75 #else
   76 static VNET_DEFINE(int, ip4_ipsec_filtertunnel) = 0;
   77 #endif
   78 #define V_ip4_ipsec_filtertunnel VNET(ip4_ipsec_filtertunnel)
   79 
   80 SYSCTL_DECL(_net_inet_ipsec);
   81 SYSCTL_VNET_INT(_net_inet_ipsec, OID_AUTO, filtertunnel,
   82         CTLFLAG_RW, &VNET_NAME(ip4_ipsec_filtertunnel), 0,
   83         "If set filter packets from an IPsec tunnel.");
   84 #endif /* IPSEC */
   85 
   86 /*
   87  * Check if we have to jump over firewall processing for this packet.
   88  * Called from ip_input().
   89  * 1 = jump over firewall, 0 = packet goes through firewall.
   90  */
   91 int
   92 ip_ipsec_filtertunnel(struct mbuf *m)
   93 {
   94 #ifdef IPSEC
   95 
   96         /*
   97          * Bypass packet filtering for packets previously handled by IPsec.
   98          */
   99         if (!V_ip4_ipsec_filtertunnel &&
  100             m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL) != NULL)
  101                 return 1;
  102 #endif
  103         return 0;
  104 }
  105 
  106 /*
  107  * Check if this packet has an active SA and needs to be dropped instead
  108  * of forwarded.
  109  * Called from ip_input().
  110  * 1 = drop packet, 0 = forward packet.
  111  */
  112 int
  113 ip_ipsec_fwd(struct mbuf *m)
  114 {
  115 #ifdef IPSEC
  116         struct m_tag *mtag;
  117         struct tdb_ident *tdbi;
  118         struct secpolicy *sp;
  119         int error;
  120 
  121         mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
  122         if (mtag != NULL) {
  123                 tdbi = (struct tdb_ident *)(mtag + 1);
  124                 sp = ipsec_getpolicy(tdbi, IPSEC_DIR_INBOUND);
  125         } else {
  126                 sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_INBOUND,
  127                                            IP_FORWARDING, &error);   
  128         }
  129         if (sp == NULL) {       /* NB: can happen if error */
  130                 /*XXX error stat???*/
  131                 DPRINTF(("ip_input: no SP for forwarding\n"));  /*XXX*/
  132                 return 1;
  133         }
  134 
  135         /*
  136          * Check security policy against packet attributes.
  137          */
  138         error = ipsec_in_reject(sp, m);
  139         KEY_FREESP(&sp);
  140         if (error) {
  141                 IPSTAT_INC(ips_cantforward);
  142                 return 1;
  143         }
  144 #endif /* IPSEC */
  145         return 0;
  146 }
  147 
  148 /*
  149  * Check if protocol type doesn't have a further header and do IPSEC
  150  * decryption or reject right now.  Protocols with further headers get
  151  * their IPSEC treatment within the protocol specific processing.
  152  * Called from ip_input().
  153  * 1 = drop packet, 0 = continue processing packet.
  154  */
  155 int
  156 ip_ipsec_input(struct mbuf *m)
  157 {
  158 #ifdef IPSEC
  159         struct ip *ip = mtod(m, struct ip *);
  160         struct m_tag *mtag;
  161         struct tdb_ident *tdbi;
  162         struct secpolicy *sp;
  163         int error;
  164         /*
  165          * enforce IPsec policy checking if we are seeing last header.
  166          * note that we do not visit this with protocols with pcb layer
  167          * code - like udp/tcp/raw ip.
  168          */
  169         if ((inetsw[ip_protox[ip->ip_p]].pr_flags & PR_LASTHDR) != 0) {
  170                 /*
  171                  * Check if the packet has already had IPsec processing
  172                  * done.  If so, then just pass it along.  This tag gets
  173                  * set during AH, ESP, etc. input handling, before the
  174                  * packet is returned to the ip input queue for delivery.
  175                  */ 
  176                 mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
  177                 if (mtag != NULL) {
  178                         tdbi = (struct tdb_ident *)(mtag + 1);
  179                         sp = ipsec_getpolicy(tdbi, IPSEC_DIR_INBOUND);
  180                 } else {
  181                         sp = ipsec_getpolicybyaddr(m, IPSEC_DIR_INBOUND,
  182                                                    IP_FORWARDING, &error);   
  183                 }
  184                 if (sp != NULL) {
  185                         /*
  186                          * Check security policy against packet attributes.
  187                          */
  188                         error = ipsec_in_reject(sp, m);
  189                         KEY_FREESP(&sp);
  190                 } else {
  191                         /* XXX error stat??? */
  192                         error = EINVAL;
  193                         DPRINTF(("ip_input: no SP, packet discarded\n"));/*XXX*/
  194                         return 1;
  195                 }
  196                 if (error)
  197                         return 1;
  198         }
  199 #endif /* IPSEC */
  200         return 0;
  201 }
  202 
  203 /*
  204  * Compute the MTU for a forwarded packet that gets IPSEC encapsulated.
  205  * Called from ip_forward().
  206  * Returns MTU suggestion for ICMP needfrag reply.
  207  */
  208 int
  209 ip_ipsec_mtu(struct mbuf *m, int mtu)
  210 {
  211         /*
  212          * If the packet is routed over IPsec tunnel, tell the
  213          * originator the tunnel MTU.
  214          *      tunnel MTU = if MTU - sizeof(IP) - ESP/AH hdrsiz
  215          * XXX quickhack!!!
  216          */
  217         return (mtu - ipsec_hdrsiz(m, IPSEC_DIR_OUTBOUND, NULL));
  218 }
  219 
  220 /*
  221  * 
  222  * Called from ip_output().
  223  * 1 = drop packet, 0 = continue processing packet,
  224  * -1 = packet was reinjected and stop processing packet
  225  */
  226 int
  227 ip_ipsec_output(struct mbuf **m, struct inpcb *inp, int *flags, int *error)
  228 {
  229 #ifdef IPSEC
  230         struct secpolicy *sp = NULL;
  231         struct tdb_ident *tdbi;
  232         struct m_tag *mtag;
  233 
  234         if (!key_havesp(IPSEC_DIR_OUTBOUND))
  235                 return 0;
  236 
  237         /*
  238          * Check the security policy (SP) for the packet and, if
  239          * required, do IPsec-related processing.  There are two
  240          * cases here; the first time a packet is sent through
  241          * it will be untagged and handled by ipsec4_checkpolicy.
  242          * If the packet is resubmitted to ip_output (e.g. after
  243          * AH, ESP, etc. processing), there will be a tag to bypass
  244          * the lookup and related policy checking.
  245          */
  246         mtag = m_tag_find(*m, PACKET_TAG_IPSEC_PENDING_TDB, NULL);
  247         if (mtag != NULL) {
  248                 tdbi = (struct tdb_ident *)(mtag + 1);
  249                 sp = ipsec_getpolicy(tdbi, IPSEC_DIR_OUTBOUND);
  250                 if (sp == NULL)
  251                         *error = -EINVAL;       /* force silent drop */
  252                 m_tag_delete(*m, mtag);
  253         } else {
  254                 sp = ipsec4_checkpolicy(*m, IPSEC_DIR_OUTBOUND, *flags,
  255                                         error, inp);
  256         }
  257         /*
  258          * There are four return cases:
  259          *    sp != NULL                    apply IPsec policy
  260          *    sp == NULL, error == 0        no IPsec handling needed
  261          *    sp == NULL, error == -EINVAL  discard packet w/o error
  262          *    sp == NULL, error != 0        discard packet, report error
  263          */
  264         if (sp != NULL) {
  265                 /* Loop detection, check if ipsec processing already done */
  266                 KASSERT(sp->req != NULL, ("ip_output: no ipsec request"));
  267                 for (mtag = m_tag_first(*m); mtag != NULL;
  268                      mtag = m_tag_next(*m, mtag)) {
  269                         if (mtag->m_tag_cookie != MTAG_ABI_COMPAT)
  270                                 continue;
  271                         if (mtag->m_tag_id != PACKET_TAG_IPSEC_OUT_DONE &&
  272                             mtag->m_tag_id != PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED)
  273                                 continue;
  274                         /*
  275                          * Check if policy has an SA associated with it.
  276                          * This can happen when an SP has yet to acquire
  277                          * an SA; e.g. on first reference.  If it occurs,
  278                          * then we let ipsec4_process_packet do its thing.
  279                          */
  280                         if (sp->req->sav == NULL)
  281                                 break;
  282                         tdbi = (struct tdb_ident *)(mtag + 1);
  283                         if (tdbi->spi == sp->req->sav->spi &&
  284                             tdbi->proto == sp->req->sav->sah->saidx.proto &&
  285                             bcmp(&tdbi->dst, &sp->req->sav->sah->saidx.dst,
  286                                  sizeof (union sockaddr_union)) == 0) {
  287                                 /*
  288                                  * No IPsec processing is needed, free
  289                                  * reference to SP.
  290                                  *
  291                                  * NB: null pointer to avoid free at
  292                                  *     done: below.
  293                                  */
  294                                 KEY_FREESP(&sp), sp = NULL;
  295                                 goto done;
  296                         }
  297                 }
  298 
  299                 /*
  300                  * Do delayed checksums now because we send before
  301                  * this is done in the normal processing path.
  302                  */
  303                 if ((*m)->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
  304                         in_delayed_cksum(*m);
  305                         (*m)->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
  306                 }
  307 #ifdef SCTP
  308                 if ((*m)->m_pkthdr.csum_flags & CSUM_SCTP) {
  309                         struct ip *ip = mtod(*m, struct ip *);
  310 
  311                         sctp_delayed_cksum(*m, (uint32_t)(ip->ip_hl << 2));
  312                         (*m)->m_pkthdr.csum_flags &= ~CSUM_SCTP;
  313                 }
  314 #endif
  315 
  316                 /* NB: callee frees mbuf */
  317                 *error = ipsec4_process_packet(*m, sp->req, *flags, 0);
  318                 if (*error == EJUSTRETURN) {
  319                         /*
  320                          * We had a SP with a level of 'use' and no SA. We
  321                          * will just continue to process the packet without
  322                          * IPsec processing and return without error.
  323                          */
  324                         *error = 0;
  325                         goto done;
  326                 }
  327                 /*
  328                  * Preserve KAME behaviour: ENOENT can be returned
  329                  * when an SA acquire is in progress.  Don't propagate
  330                  * this to user-level; it confuses applications.
  331                  *
  332                  * XXX this will go away when the SADB is redone.
  333                  */
  334                 if (*error == ENOENT)
  335                         *error = 0;
  336                 goto reinjected;
  337         } else {        /* sp == NULL */
  338 
  339                 if (*error != 0) {
  340                         /*
  341                          * Hack: -EINVAL is used to signal that a packet
  342                          * should be silently discarded.  This is typically
  343                          * because we asked key management for an SA and
  344                          * it was delayed (e.g. kicked up to IKE).
  345                          */
  346                         if (*error == -EINVAL)
  347                                 *error = 0;
  348                         goto bad;
  349                 } else {
  350                         /* No IPsec processing for this packet. */
  351                 }
  352         }
  353 done:
  354         if (sp != NULL)
  355                 KEY_FREESP(&sp);
  356         return 0;
  357 reinjected:
  358         if (sp != NULL)
  359                 KEY_FREESP(&sp);
  360         return -1;
  361 bad:
  362         if (sp != NULL)
  363                 KEY_FREESP(&sp);
  364         return 1;
  365 #endif /* IPSEC */
  366         return 0;
  367 }

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