/*	$OpenBSD: dnssec.c,v 1.16 2003/06/03 14:28:16 ho Exp $	*/

/*
 * Copyright (c) 2001 Håkan Olsson.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <arpa/inet.h>
#include <stdlib.h>

#include <openssl/rsa.h>

#ifdef LWRES
#include <lwres/netdb.h>
#include <dns/keyvalues.h>
#else
#include <netdb.h>
#endif

#include "sysdep.h"

#include "dnssec.h"
#include "exchange.h"
#include "ipsec_num.h"
#include "libcrypto.h"
#include "log.h"
#include "message.h"
#include "transport.h"
#include "util.h"

#ifndef DNS_UFQDN_SEPARATOR
#define DNS_UFQDN_SEPARATOR "._ipsec."
#endif

/* adapted from <dns/rdatastruct.h> / RFC 2535  */
struct dns_rdata_key {
  u_int16_t flags;
  u_int8_t protocol;
  u_int8_t algorithm;
  u_int16_t datalen;
  unsigned char *data;
};

void *
dns_get_key (int type, struct message *msg, int *keylen)
{
  struct exchange *exchange = msg->exchange;
  struct rrsetinfo *rr;
  struct dns_rdata_key key_rr;
  char name[MAXHOSTNAMELEN];
  in_addr_t ip4;
  u_int8_t algorithm;
  u_int8_t *id, *umark;
  size_t id_len;
  int ret, i;

  switch (type)
    {
    case IKE_AUTH_RSA_SIG:
      algorithm = DNS_KEYALG_RSA;
      break;

    case IKE_AUTH_RSA_ENC:
    case IKE_AUTH_RSA_ENC_REV:
      /* XXX Not yet. */
      /* algorithm = DNS_KEYALG_RSA; */
      return 0;

    case IKE_AUTH_DSS:
      /* XXX Not yet. */
      /* algorithm = DNS_KEYALG_DSS; */
      return 0;

    case IKE_AUTH_PRE_SHARED:
    default:
      return 0;
    }

  id = exchange->initiator ? exchange->id_r : exchange->id_i;
  id_len = exchange->initiator ? exchange->id_r_len : exchange->id_i_len;
  memset (name, 0, sizeof name);

  if (!id || id_len == 0)
    {
      log_print ("dns_get_key: ID is missing");
      return 0;
    }

  /* Exchanges (and SAs) don't carry the ID in ISAKMP form */
  id -= ISAKMP_GEN_SZ;
  id_len += ISAKMP_GEN_SZ - ISAKMP_ID_DATA_OFF;

  switch (GET_ISAKMP_ID_TYPE (id))
    {
    case IPSEC_ID_IPV4_ADDR:
      /* We want to lookup a KEY RR in the reverse zone.  */
      if (id_len < sizeof ip4)
	return 0;
      memcpy (&ip4, id + ISAKMP_ID_DATA_OFF, sizeof ip4);
      snprintf (name, sizeof name, "%d.%d.%d.%d.in-addr.arpa.", ip4 >> 24,
	       (ip4 >> 16) & 0xFF, (ip4 >> 8) & 0xFF, ip4 & 0xFF);
      break;

    case IPSEC_ID_IPV6_ADDR:
      /* XXX Not yet. */
      return 0;
      break;

    case IPSEC_ID_FQDN:
      if ((id_len + 1) >= sizeof name)
	return 0;
      /* ID is not NULL-terminated. Add trailing dot and terminate.  */
      memcpy (name, id + ISAKMP_ID_DATA_OFF, id_len);
      *(name + id_len) = '.';
      *(name + id_len + 1) = '\0';
      break;

    case IPSEC_ID_USER_FQDN:
      /*
       * Some special handling here. We want to convert the ID
       * 'user@host.domain' string into 'user._ipsec.host.domain.'.
       */
      if ((id_len + sizeof (DNS_UFQDN_SEPARATOR)) >= sizeof name)
	return 0;
      /* Look for the '@' separator.  */
      for (umark = id + ISAKMP_ID_DATA_OFF; (umark - id) < id_len; umark++)
	if (*umark == '@')
	  break;
      if (*umark != '@')
	{
	  LOG_DBG((LOG_MISC, 50, "dns_get_key: bad UFQDN ID"));
	  return 0;
	}
      *umark++ = '\0';
      /* id is now terminated. 'umark', however, is not.  */
      snprintf (name, sizeof name, "%s%s", id + ISAKMP_ID_DATA_OFF,
		DNS_UFQDN_SEPARATOR);
      memcpy (name + strlen (name), umark, id_len - strlen (id) - 1);
      *(name + id_len + sizeof (DNS_UFQDN_SEPARATOR) - 2) = '.';
      *(name + id_len + sizeof (DNS_UFQDN_SEPARATOR) - 1) = '\0';
      break;

    default:
      return 0;
    }

  LOG_DBG ((LOG_MISC, 50, "dns_get_key: trying KEY RR for %s", name));
  ret = getrrsetbyname (name, C_IN, T_KEY, 0, &rr);

  if (ret)
    {
      LOG_DBG ((LOG_MISC, 30, "dns_get_key: no DNS responses (error %d)",
		ret));
      return 0;
    }

  LOG_DBG ((LOG_MISC, 80,
	    "dns_get_key: rrset class %d type %d ttl %d nrdatas %d nrsigs %d",
	    rr->rri_rdclass, rr->rri_rdtype, rr->rri_ttl, rr->rri_nrdatas,
	    rr->rri_nsigs));

  /* We don't accept unvalidated data. */
  if (!(rr->rri_flags & RRSET_VALIDATED))
    {
      LOG_DBG ((LOG_MISC, 10, "dns_get_key: got unvalidated response"));
      freerrset (rr);
      return 0;
    }

  /* Sanity. */
  if (rr->rri_nrdatas == 0 || rr->rri_rdtype != T_KEY)
    {
      LOG_DBG ((LOG_MISC, 30, "dns_get_key: no KEY RRs received"));
      freerrset (rr);
      return 0;
    }

  memset (&key_rr, 0, sizeof key_rr);

  /*
   * Find a key with the wanted algorithm, if any.
   * XXX If there are several keys present, we currently only find the first.
   */
  for (i = 0; i < rr->rri_nrdatas && key_rr.datalen == 0; i++)
    {
      key_rr.flags     = ntohs ((u_int16_t) *rr->rri_rdatas[i].rdi_data);
      key_rr.protocol  = *(rr->rri_rdatas[i].rdi_data + 2);
      key_rr.algorithm = *(rr->rri_rdatas[i].rdi_data + 3);

      if (key_rr.protocol != DNS_KEYPROTO_IPSEC)
	{
	  LOG_DBG ((LOG_MISC, 50, "dns_get_key: ignored non-IPsec key"));
	  continue;
	}

      if (key_rr.algorithm != algorithm)
	{
	  LOG_DBG ((LOG_MISC, 50, "dns_get_key: ignored key with other alg"));
	  continue;
	}

      key_rr.datalen = rr->rri_rdatas[i].rdi_length - 4;
      if (key_rr.datalen <= 0)
	{
	  LOG_DBG ((LOG_MISC, 50, "dns_get_key: ignored bad key"));
	  key_rr.datalen = 0;
	  continue;
	}

      /* This key seems to fit our requirements... */
      key_rr.data = (char *)malloc (key_rr.datalen);
      if (!key_rr.data)
	{
	  log_error ("dns_get_key: malloc (%d) failed", key_rr.datalen);
	  freerrset (rr);
	  return 0;
	}
      memcpy (key_rr.data, rr->rri_rdatas[i].rdi_data + 4, key_rr.datalen);
      *keylen = key_rr.datalen;
    }

  freerrset (rr);

  if (key_rr.datalen)
    return key_rr.data;
  else
    return 0;
}

int
dns_RSA_dns_to_x509 (u_int8_t *key, int keylen, RSA **rsa_key)
{
  RSA *rsa;
  int key_offset;
  u_int8_t e_len;

  if (!key || keylen <= 0)
    {
      log_print ("dns_RSA_dns_to_x509: invalid public key");
      return -1;
    }

  rsa = RSA_new ();
  if (rsa == NULL)
    {
      log_error ("dns_RSA_dns_to_x509: failed to allocate new RSA struct");
      return -1;
    }

  e_len = *key;
  key_offset = 1;

  if (e_len == 0)
    {
      if (keylen < 3)
	{
	  log_print ("dns_RSA_dns_to_x509: invalid public key");
	  RSA_free (rsa);
	  return -1;
	}
      e_len  = *(key + key_offset++) << 8;
      e_len += *(key + key_offset++);
    }

  if (e_len > (keylen - key_offset))
    {
      log_print ("dns_RSA_dns_to_x509: invalid public key");
      RSA_free (rsa);
      return -1;
    }

  rsa->e = BN_bin2bn (key + key_offset, e_len, NULL);
  key_offset += e_len;

  /* XXX if (keylen <= key_offset) -> "invalid public key" ? */

  rsa->n = BN_bin2bn (key + key_offset, keylen - key_offset, NULL);

  *rsa_key = rsa;

  LOG_DBG ((LOG_MISC, 30, "dns_RSA_dns_to_x509: got %d bits RSA key",
	    BN_num_bits (rsa->n)));

  return 0;
}

#if notyet
int
dns_RSA_x509_to_dns (RSA *rsa_key, u_int8_t *key, int *keylen)
{
  return 0;
}
#endif