Internet on FIRE

/*

 *        BIRD -- OSPF

 *

 *        (c) 1999--2005 Ondrej Filip <feela@network.cz>

 *        (c) 2009--2014 Ondrej Zajicek <santiago@crfreenet.org>

 *        (c) 2009--2014 CZ.NIC z.s.p.o.

 *

 *        Can be freely distributed and used under the terms of the GNU GPL.

 */

#include "ospf.h"

#include "nest/password.h"

#include "lib/md5.h"

#include "lib/socket.h"

void

ospf_pkt_fill_hdr(struct ospf_iface *ifa, void *buf, u8 h_type)

{

  struct ospf_proto *p = ifa->oa->po;

  struct ospf_packet *pkt;

  pkt = (struct ospf_packet *) buf;

  pkt->version = ospf_get_version(p);

  pkt->type = h_type;

  pkt->length = htons(ospf_pkt_maxsize(ifa));

  pkt->routerid = htonl(p->router_id);

  pkt->areaid = htonl(ifa->oa->areaid);

  pkt->checksum = 0;

  pkt->instance_id = ifa->instance_id;

  pkt->autype = ifa->autype;

}

uint

ospf_pkt_maxsize(struct ospf_iface *ifa)

{

  uint headers = SIZE_OF_IP_HEADER;

  /* Relevant just for OSPFv2 */

  if (ifa->autype == OSPF_AUTH_CRYPT)

    headers += OSPF_AUTH_CRYPT_SIZE;

  return ifa->tx_length - headers;

}

/* We assume OSPFv2 in ospf_pkt_finalize() */

static void

ospf_pkt_finalize(struct ospf_iface *ifa, struct ospf_packet *pkt)

{

  struct password_item *passwd = NULL;

  union ospf_auth *auth = (void *) (pkt + 1);

  uint plen = ntohs(pkt->length);

  pkt->checksum = 0;

  pkt->autype = ifa->autype;

  bzero(auth, sizeof(union ospf_auth));

  /* Compatibility note: auth may contain anything if autype is

     none, but nonzero values do not work with Mikrotik OSPF */

  switch (ifa->autype)

  {

  case OSPF_AUTH_SIMPLE:

    passwd = password_find(ifa->passwords, 1);

    if (!passwd)

    {

      log(L_ERR "No suitable password found for authentication");

      return;

    }

    strncpy(auth->password, passwd->password, sizeof(auth->password));

  case OSPF_AUTH_NONE:

    {

      void *body = (void *) (auth + 1);

      uint blen = plen - sizeof(struct ospf_packet) - sizeof(union ospf_auth);

      pkt->checksum = ipsum_calculate(pkt, sizeof(struct ospf_packet), body, blen, NULL);

    }

    break;

  case OSPF_AUTH_CRYPT:

    passwd = password_find(ifa->passwords, 0);

    if (!passwd)

    {

      log(L_ERR "No suitable password found for authentication");

      return;

    }

    /* Perhaps use random value to prevent replay attacks after

       reboot when system does not have independent RTC? */

    if (!ifa->csn)

    {

      ifa->csn = (u32) now;

      ifa->csn_use = now;

    }

    /* We must have sufficient delay between sending a packet and increasing

       CSN to prevent reordering of packets (in a network) with different CSNs */

    if ((now - ifa->csn_use) > 1)

      ifa->csn++;

    ifa->csn_use = now;

    auth->md5.zero = 0;

    auth->md5.keyid = passwd->id;

    auth->md5.len = OSPF_AUTH_CRYPT_SIZE;

    auth->md5.csn = htonl(ifa->csn);

    void *tail = ((void *) pkt) + plen;

    char password[OSPF_AUTH_CRYPT_SIZE];

    strncpy(password, passwd->password, sizeof(password));

    struct md5_context ctx;

    md5_init(&ctx);

    md5_update(&ctx, (char *) pkt, plen);

    md5_update(&ctx, password, OSPF_AUTH_CRYPT_SIZE);

    memcpy((byte *) tail, md5_final(&ctx), MD5_SIZE);

    break;

  default:

    bug("Unknown authentication type");

  }

}

/* We assume OSPFv2 in ospf_pkt_checkauth() */

static int

ospf_pkt_checkauth(struct ospf_neighbor *n, struct ospf_iface *ifa, struct ospf_packet *pkt, int len)

{

  struct ospf_proto *p = ifa->oa->po;

  union ospf_auth *auth = (void *) (pkt + 1);

  struct password_item *pass = NULL;

  const char *err_dsc = NULL;

  uint err_val = 0;

  uint plen = ntohs(pkt->length);

  u8 autype = pkt->autype;

  if (autype != ifa->autype)

    DROP("authentication method mismatch", autype);

  switch (autype)

  {

  case OSPF_AUTH_NONE:

    return 1;

  case OSPF_AUTH_SIMPLE:

    pass = password_find(ifa->passwords, 1);

    if (!pass)

      DROP1("no password found");

    if (!password_verify(pass, auth->password, sizeof(auth->password)))

      DROP("wrong password", pass->id);

    return 1;

  case OSPF_AUTH_CRYPT:

    if (auth->md5.len != OSPF_AUTH_CRYPT_SIZE)

      DROP("invalid MD5 digest length", auth->md5.len);

    if (plen + OSPF_AUTH_CRYPT_SIZE > len)

      DROP("length mismatch", len);

    u32 rcv_csn = ntohl(auth->md5.csn);

    if (n && (rcv_csn < n->csn))

      // DROP("lower sequence number", rcv_csn);

    {

      /* We want to report both new and old CSN */

      LOG_PKT_AUTH("Authentication failed for nbr %R on %s - "

                   "lower sequence number (rcv %u, old %u)",

                   n->rid, ifa->ifname, rcv_csn, n->csn);

      return 0;

    }

    pass = password_find_by_id(ifa->passwords, auth->md5.keyid);

    if (!pass)

      DROP("no suitable password found", auth->md5.keyid);

    byte *tail = ((byte *) pkt) + plen;

    char received[OSPF_AUTH_CRYPT_SIZE];

    memcpy(received, tail, OSPF_AUTH_CRYPT_SIZE);

    strncpy(tail, pass->password, OSPF_AUTH_CRYPT_SIZE);

    struct md5_context ctx;

    md5_init(&ctx);

    md5_update(&ctx, (byte *) pkt, plen + OSPF_AUTH_CRYPT_SIZE);

    char *computed = md5_final(&ctx);

    if (memcmp(received, computed, OSPF_AUTH_CRYPT_SIZE))

      DROP("wrong MD5 digest", pass->id);

    if (n)

      n->csn = rcv_csn;

    return 1;

  default:

    bug("Unknown authentication type");

  }

drop:

  LOG_PKT_AUTH("Authentication failed for nbr %R on %s - %s (%u)",

               (n ? n->rid : ntohl(pkt->routerid)), ifa->ifname, err_dsc, err_val);

  return 0;

}

/**

 * ospf_rx_hook

 * @sk: socket we received the packet.

 * @len: size of the packet

 *

 * This is the entry point for messages from neighbors. Many checks (like

 * authentication, checksums, size) are done before the packet is passed to

 * non generic functions.

 */

int

ospf_rx_hook(sock *sk, int len)

{

  /* We want just packets from sk->iface. Unfortunately, on BSD we cannot filter

     out other packets at kernel level and we receive all packets on all sockets */

  if (sk->lifindex != sk->iface->index)

    return 1;

  DBG("OSPF: RX hook called (iface %s, src %I, dst %I)\n",

      sk->iface->name, sk->faddr, sk->laddr);

  /* Initially, the packet is associated with the 'master' iface */

  struct ospf_iface *ifa = sk->data;

  struct ospf_proto *p = ifa->oa->po;

  const char *err_dsc = NULL;

  uint err_val = 0;

  /* Should not happen */

  if (ifa->state <= OSPF_IS_LOOP)

    return 1;

  int src_local, dst_local, dst_mcast;

  src_local = ipa_in_net(sk->faddr, ifa->addr->prefix, ifa->addr->pxlen);

  dst_local = ipa_equal(sk->laddr, ifa->addr->ip);

  dst_mcast = ipa_equal(sk->laddr, ifa->all_routers) || ipa_equal(sk->laddr, ifa->des_routers);

  if (ospf_is_v2(p))

  {

    /* First, we eliminate packets with strange address combinations.

     * In OSPFv2, they might be for other ospf_ifaces (with different IP

     * prefix) on the same real iface, so we don't log it. We enforce

     * that (src_local || dst_local), therefore we are eliminating all

     * such cases.

     */

    if (dst_mcast && !src_local)

      return 1;

    if (!dst_mcast && !dst_local)

      return 1;

    /* Ignore my own broadcast packets */

    if (ifa->cf->real_bcast && ipa_equal(sk->faddr, ifa->addr->ip))

      return 1;

  }

  else

  {

    /* In OSPFv3, src_local and dst_local mean link-local.

     * RFC 5340 says that local (non-vlink) packets use

     * link-local src address, but does not enforce it. Strange.

     */

    if (dst_mcast && !src_local)

      LOG_PKT_WARN("Multicast packet received from non-link-local %I via %s",

                   sk->faddr, ifa->ifname);

  }

  /* Second, we check packet length, checksum, and the protocol version */

  struct ospf_packet *pkt = (void *) sk_rx_buffer(sk, &len);

  if (pkt == NULL)

    DROP("bad IP header", len);

  if (ifa->check_ttl && (sk->rcv_ttl < 255))

    DROP("wrong TTL", sk->rcv_ttl);

  if (len < sizeof(struct ospf_packet))

    DROP("too short", len);

  if (pkt->version != ospf_get_version(p))

    DROP("version mismatch", pkt->version);

  uint plen = ntohs(pkt->length);

  if ((plen < sizeof(struct ospf_packet)) || ((plen % 4) != 0))

    DROP("invalid length", plen);

  if (sk->flags & SKF_TRUNCATED)

  {

    /* If we have dynamic buffers and received truncated message, we expand RX buffer */

    uint bs = plen + 256;

    bs = BIRD_ALIGN(bs, 1024);

    if (!ifa->cf->rx_buffer && (bs > sk->rbsize))

      sk_set_rbsize(sk, bs);

    DROP("truncated", plen);

  }

  if (plen > len)

    DROP("length mismatch", plen);

  if (ospf_is_v2(p) && (pkt->autype != OSPF_AUTH_CRYPT))

  {

    uint hlen = sizeof(struct ospf_packet) + sizeof(union ospf_auth);

    uint blen = plen - hlen;

    void *body = ((void *) pkt) + hlen;

    if (!ipsum_verify(pkt, sizeof(struct ospf_packet), body, blen, NULL))

      DROP1("invalid checksum");

  }

  /* Third, we resolve associated iface and handle vlinks. */

  u32 areaid = ntohl(pkt->areaid);

  u32 rid = ntohl(pkt->routerid);

  u8 instance_id = pkt->instance_id;

  if (areaid == ifa->oa->areaid)

  {

    /* Matching area ID */

    if (instance_id != ifa->instance_id)

      return 1;

    /* It is real iface, source should be local (in OSPFv2) */

    if (ospf_is_v2(p) && !src_local)

      DROP1("strange source address");

    goto found;

  }

  else if ((areaid == 0) && !dst_mcast)

  {

    /* Backbone area ID and possible vlink packet */

    if ((p->areano == 1) || !oa_is_ext(ifa->oa))

      return 1;

    struct ospf_iface *iff = NULL;

    WALK_LIST(iff, p->iface_list)

    {

      if ((iff->type == OSPF_IT_VLINK) &&

          (iff->voa == ifa->oa) &&

          (iff->instance_id == instance_id) &&

          (iff->vid == rid))

      {

        /* Vlink should be UP */

        if (iff->state != OSPF_IS_PTP)

          return 1;

        ifa = iff;

        goto found;

      }

    }

    /*

     * Cannot find matching vlink. It is either misconfigured vlink; NBMA or

     * PtMP with misconfigured area ID, or packet for some other instance (that

     * is possible even if instance_id == ifa->instance_id, because it may be

     * also vlink packet in the other instance, which is different namespace).

     */

    return 1;

  }

  else

  {

    /* Non-matching area ID but cannot be vlink packet */

    if (instance_id != ifa->instance_id)

      return 1;

    DROP("area mismatch", areaid);

  }

found:

  if (ifa->stub)            /* This shouldn't happen */

    return 1;

  if (ipa_equal(sk->laddr, ifa->des_routers) && (ifa->sk_dr == 0))

    return 1;

  if (rid == p->router_id)

    DROP1("my own router ID");

  if (rid == 0)

    DROP1("zero router ID");

  /* In OSPFv2, neighbors are identified by either IP or Router ID, based on network type */

  uint t = ifa->type;

  struct ospf_neighbor *n;

  if (ospf_is_v2(p) && ((t == OSPF_IT_BCAST) || (t == OSPF_IT_NBMA) || (t == OSPF_IT_PTMP)))

    n = find_neigh_by_ip(ifa, sk->faddr);

  else

    n = find_neigh(ifa, rid);

  if (!n && (pkt->type != HELLO_P))

  {

    OSPF_TRACE(D_PACKETS, "Non-HELLO packet received from unknown nbr %R on %s, src %I",

               rid, ifa->ifname, sk->faddr);

    return 1;

  }

  /* ospf_pkt_checkauth() has its own error logging */

  if (ospf_is_v2(p) && !ospf_pkt_checkauth(n, ifa, pkt, len))

    return 1;

  switch (pkt->type)

  {

  case HELLO_P:

    ospf_receive_hello(pkt, ifa, n, sk->faddr);

    break;

  case DBDES_P:

    ospf_receive_dbdes(pkt, ifa, n);

    break;

  case LSREQ_P:

    ospf_receive_lsreq(pkt, ifa, n);

    break;

  case LSUPD_P:

    ospf_receive_lsupd(pkt, ifa, n);

    break;

  case LSACK_P:

    ospf_receive_lsack(pkt, ifa, n);

    break;

  default:

    DROP("invalid packet type", pkt->type);

  };

  return 1;

drop:

  LOG_PKT("Bad packet from %I via %s - %s (%u)",

          sk->faddr, ifa->ifname, err_dsc, err_val);

  return 1;

}

/*

void

ospf_tx_hook(sock * sk)

{

  struct ospf_iface *ifa= (struct ospf_iface *) (sk->data);

//  struct proto *p = (struct proto *) (ifa->oa->p);

  log(L_ERR "OSPF: TX hook called on %s", ifa->ifname);

}

*/

void

ospf_err_hook(sock * sk, int err)

{

  struct ospf_iface *ifa= (struct ospf_iface *) (sk->data);

  struct ospf_proto *p = ifa->oa->po;

  log(L_ERR "%s: Socket error on %s: %M", p->p.name, ifa->ifname, err);

}

void

ospf_verr_hook(sock *sk, int err)

{

  struct ospf_proto *p = (struct ospf_proto *) (sk->data);

  log(L_ERR "%s: Vlink socket error: %M", p->p.name, err);

}

void

ospf_send_to(struct ospf_iface *ifa, ip_addr dst)

{

  sock *sk = ifa->sk;

  struct ospf_packet *pkt = (struct ospf_packet *) sk->tbuf;

  int plen = ntohs(pkt->length);

  if (ospf_is_v2(ifa->oa->po))

  {

    if (ifa->autype == OSPF_AUTH_CRYPT)

      plen += OSPF_AUTH_CRYPT_SIZE;

    ospf_pkt_finalize(ifa, pkt);

  }

  int done = sk_send_to(sk, plen, dst, 0);

  if (!done)

    log(L_WARN "OSPF: TX queue full on %s", ifa->ifname);

}

void

ospf_send_to_agt(struct ospf_iface *ifa, u8 state)

{

  struct ospf_neighbor *n;

  WALK_LIST(n, ifa->neigh_list)

    if (n->state >= state)

      ospf_send_to(ifa, n->ip);

}

void

ospf_send_to_bdr(struct ospf_iface *ifa)

{

  if (ipa_nonzero(ifa->drip))

    ospf_send_to(ifa, ifa->drip);

  if (ipa_nonzero(ifa->bdrip))

    ospf_send_to(ifa, ifa->bdrip);

}