tinc/src/protocol.c

/*
    protocol.c -- handle the meta-protocol
    Copyright (C) 1999,2000 Ivo Timmermans <itimmermans@bigfoot.com>,
                       2000 Guus Sliepen <guus@sliepen.warande.net>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

    $Id: protocol.c,v 1.28.4.72 2001/01/06 18:03:40 guus Exp $
*/

#include "config.h"

#include <sys/types.h>

#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <sys/socket.h>
#include <unistd.h>
#include <stdio.h>
#include <stdarg.h>

#include <utils.h>
#include <xalloc.h>
#include <avl_tree.h>

#include <netinet/in.h>

#ifdef HAVE_OPENSSL_SHA_H
# include <openssl/sha.h>
#else
# include <sha.h>
#endif

#ifdef HAVE_OPENSSL_RAND_H
# include <openssl/rand.h>
#else
# include <rand.h>
#endif

#ifdef HAVE_OPENSSL_EVP_H
# include <openssl/evp.h>
#else
# include <evp.h>
#endif


#include "conf.h"
#include "net.h"
#include "netutl.h"
#include "protocol.h"
#include "meta.h"
#include "connection.h"

#include "system.h"

int check_id(char *id)
{
  int i;

  for (i = 0; i < strlen(id); i++)
    if(!isalnum(id[i]) && id[i] != '_')
      return -1;
  
  return 0;
}

/* Generic request routines - takes care of logging and error
   detection as well */

int send_request(connection_t *cl, const char *format, ...)
{
  va_list args;
  char buffer[MAXBUFSIZE];
  int len, request;

cp
  /* Use vsnprintf instead of vasprintf: faster, no memory
     fragmentation, cleanup is automatic, and there is a limit on the
     input buffer anyway */

  va_start(args, format);
  len = vsnprintf(buffer, MAXBUFSIZE, format, args);
  request = va_arg(args, int);
  va_end(args);

  if(len < 0 || len > MAXBUFSIZE-1)
    {
      syslog(LOG_ERR, _("Output buffer overflow while sending %s to %s (%s)"), request_name[request], cl->name, cl->hostname);
      return -1;
    }

  len++;

  if(debug_lvl >= DEBUG_PROTOCOL)
    syslog(LOG_DEBUG, _("Sending %s to %s (%s)"), request_name[request], cl->name, cl->hostname);

cp
  return send_meta(cl, buffer, len);
}

int receive_request(connection_t *cl)
{
  int request;
cp  
  if(sscanf(cl->buffer, "%d", &request) == 1)
    {
      if((request < 0) || (request > 255) || (request_handlers[request] == NULL))
        {
          syslog(LOG_ERR, _("Unknown request from %s (%s)"),
		 cl->name, cl->hostname);
          return -1;
        }
      else
        {
          if(debug_lvl >= DEBUG_PROTOCOL)
            syslog(LOG_DEBUG, _("Got %s from %s (%s)"),
		   request_name[request], cl->name, cl->hostname);
	}

      if((cl->allow_request != ALL) && (cl->allow_request != request))
        {
          syslog(LOG_ERR, _("Unauthorized request from %s (%s)"), cl->name, cl->hostname);
          return -1;
        }

      if(request_handlers[request](cl))
	/* Something went wrong. Probably scriptkiddies. Terminate. */
        {
          syslog(LOG_ERR, _("Error while processing %s from %s (%s)"),
		 request_name[request], cl->name, cl->hostname);
          return -1;
        }
    }
  else
    {
      syslog(LOG_ERR, _("Bogus data received from %s (%s)"),
	     cl->name, cl->hostname);
      return -1;
    }
cp
  return 0;
}

/* Connection protocol:

   Client               Server
   send_id(u)
                        send_challenge(R)
   send_chal_reply(H)
                        send_id(u)
   send_challenge(R)
                        send_chal_reply(H)
   ---------------------------------------
   send_metakey(R)
                        send_metakey(R)
   ---------------------------------------
   send_ack(u)
                        send_ack(u)
   ---------------------------------------
   Other requests(E)...

   (u) Unencrypted,
   (R) RSA,
   (H) SHA1,
   (E) Encrypted with symmetric cipher.

   Part of the challenge is directly used to set the symmetric cipher
   key and the initial vector.  Since a man-in-the-middle cannot
   decrypt the RSA challenges, this means that he cannot get or forge
   the key for the symmetric cipher.
*/

int send_id(connection_t *cl)
{
cp
  cl->allow_request = CHALLENGE;
cp
  return send_request(cl, "%d %s %d %lx %hd", ID, myself->name, myself->protocol_version, myself->options, myself->port);
}

int id_h(connection_t *cl)
{
  connection_t *old;
  unsigned short int port;
  char name[MAX_STRING_SIZE];
  avl_node_t *node;
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING" %d %lx %hd", name, &cl->protocol_version, &cl->options, &port) != 4)
    {
       syslog(LOG_ERR, _("Got bad ID from %s"), cl->hostname);
       return -1;
    }

  /* Check if version matches */

  if(cl->protocol_version != myself->protocol_version)
    {
      syslog(LOG_ERR, _("Peer %s (%s) uses incompatible version %d"),
             cl->name, cl->hostname, cl->protocol_version);
      return -1;
    }

  /* Check if identity is a valid name */

  if(check_id(name))
    {
      syslog(LOG_ERR, _("Peer %s uses invalid identity name"), cl->hostname);
      return -1;
    }
  
  /* Copy string to cl */
  
  cl->name = xstrdup(name);

  /* Load information about peer */

  if(read_host_config(cl))
    {
      syslog(LOG_ERR, _("Peer %s had unknown identity (%s)"), cl->hostname, cl->name);
      return -1;
    }

  /* First check if the host we connected to is already in our
     connection list. If so, we are probably making a loop, which
     is not desirable.
   */

  if(cl->status.outgoing)
    {
      if((old = lookup_id(cl->name)))
        {
          if(debug_lvl >= DEBUG_CONNECTIONS)
            syslog(LOG_NOTICE, _("Uplink %s (%s) is already in our connection list"), cl->name, cl->hostname);
          cl->status.outgoing = 0;
          old->status.outgoing = 1;
          terminate_connection(cl);
          return 0;
        }
    }
    
  /* Now we can add the name to the id tree */
  
  id_add(cl);

  /* And uhr... cl->port just changed so we have to unlink it from the connection tree and re-insert... */
  
  node = avl_unlink(connection_tree, cl);
  cl->port = port;
  avl_insert_node(connection_tree, node);

  /* Read in the public key, so that we can send a challenge */

  if(read_rsa_public_key(cl))
    return -1;

cp
  return send_challenge(cl);
}

int send_challenge(connection_t *cl)
{
  char *buffer;
  int len, x;
cp
  len = RSA_size(cl->rsa_key);

  /* Allocate buffers for the challenge */

  buffer = xmalloc(len*2+1);

  if(cl->hischallenge)
    free(cl->hischallenge);
    
  cl->hischallenge = xmalloc(len);
cp
  /* Copy random data to the buffer */

  RAND_bytes(cl->hischallenge, len);

  cl->hischallenge[0] &= 0x7F;	/* Somehow if the first byte is more than 0xD0 or something like that, decryption fails... */
cp
  if(debug_lvl >= DEBUG_SCARY_THINGS)
    {
      bin2hex(cl->hischallenge, buffer, len);
      buffer[len*2] = '\0';
      syslog(LOG_DEBUG, _("Generated random challenge (unencrypted): %s"), buffer);
    }

  /* Encrypt the random data */

  if(RSA_public_encrypt(len, cl->hischallenge, buffer, cl->rsa_key, RSA_NO_PADDING) != len)	/* NO_PADDING because the message size equals the RSA key size and it is totally random */
    {
      syslog(LOG_ERR, _("Error during encryption of challenge for %s (%s)"), cl->name, cl->hostname);
      free(buffer);
      return -1;
    }
cp
  /* Convert the encrypted random data to a hexadecimal formatted string */

  bin2hex(buffer, buffer, len);
  buffer[len*2] = '\0';
cp
  /* Send the challenge */

  cl->allow_request = CHAL_REPLY;
  x = send_request(cl, "%d %s", CHALLENGE, buffer);
  free(buffer);
cp
  return x;
}

int challenge_h(connection_t *cl)
{
  char buffer[MAX_STRING_SIZE];
  int len;
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING, buffer) != 1)
    {
       syslog(LOG_ERR, _("Got bad CHALLENGE from %s (%s)"), cl->name, cl->hostname);
       return -1;
    }

  len = RSA_size(myself->rsa_key);

  /* Check if the length of the challenge is all right */

  if(strlen(buffer) != len*2)
    {
      syslog(LOG_ERR, _("Intruder: wrong challenge length from %s (%s)"), cl->name, cl->hostname);
      return -1;
    }

  /* Allocate buffers for the challenge */

  if(!cl->mychallenge)
    cl->mychallenge = xmalloc(len);

  /* Convert the challenge from hexadecimal back to binary */

  hex2bin(buffer,buffer,len);

  /* Decrypt the challenge */
  
  if(RSA_private_decrypt(len, buffer, cl->mychallenge, myself->rsa_key, RSA_NO_PADDING) != len)	/* See challenge() */
    {
      syslog(LOG_ERR, _("Error during encryption of challenge for %s (%s)"), cl->name, cl->hostname);
      return -1;
    }

  if(debug_lvl >= DEBUG_SCARY_THINGS)
    {
      bin2hex(cl->mychallenge, buffer, len);
      buffer[len*2] = '\0';
      syslog(LOG_DEBUG, _("Received random challenge (unencrypted): %s"), buffer);
    }

  /* Rest is done by send_chal_reply() */
cp
  return send_chal_reply(cl);
}

int send_chal_reply(connection_t *cl)
{
  char hash[SHA_DIGEST_LENGTH*2+1];
cp
  if(!cl->mychallenge)
    {
      syslog(LOG_ERR, _("Trying to send CHAL_REPLY to %s (%s) without a valid CHALLENGE"), cl->name, cl->hostname);
      return -1;
    }
     
  /* Calculate the hash from the challenge we received */

  SHA1(cl->mychallenge, RSA_size(myself->rsa_key), hash);

  /* Convert the hash to a hexadecimal formatted string */

  bin2hex(hash,hash,SHA_DIGEST_LENGTH);
  hash[SHA_DIGEST_LENGTH*2] = '\0';

  /* Send the reply */

  if(cl->status.outgoing)
    cl->allow_request = ID;
  else
    cl->allow_request = METAKEY;

cp
  return send_request(cl, "%d %s", CHAL_REPLY, hash);
}

int chal_reply_h(connection_t *cl)
{
  char hishash[MAX_STRING_SIZE];
  char myhash[SHA_DIGEST_LENGTH];
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING, hishash) != 1)
    {
       syslog(LOG_ERR, _("Got bad CHAL_REPLY from %s (%s)"), cl->name, cl->hostname);
       return -1;
    }

  /* Check if the length of the hash is all right */

  if(strlen(hishash) != SHA_DIGEST_LENGTH*2)
    {
      syslog(LOG_ERR, _("Intruder: wrong challenge reply length from %s (%s)"), cl->name, cl->hostname);
      return -1;
    }

  /* Convert the hash to binary format */

  hex2bin(hishash, hishash, SHA_DIGEST_LENGTH);

  /* Calculate the hash from the challenge we sent */

  SHA1(cl->hischallenge, RSA_size(cl->rsa_key), myhash);

  /* Verify the incoming hash with the calculated hash */

  if(memcmp(hishash, myhash, SHA_DIGEST_LENGTH))
    {
      syslog(LOG_ERR, _("Intruder: wrong challenge reply from %s (%s)"), cl->name, cl->hostname);
      if(debug_lvl >= DEBUG_SCARY_THINGS)
        {
          bin2hex(myhash, hishash, SHA_DIGEST_LENGTH);
          hishash[SHA_DIGEST_LENGTH*2] = '\0';
          syslog(LOG_DEBUG, _("Expected challenge reply: %s"), hishash);
        }
      return -1;
    }


  /* Identity has now been positively verified.
     If we are accepting this new connection, then send our identity,
     if we are making this connecting, acknowledge.
   */
cp
  if(cl->status.outgoing)
      return send_metakey(cl);
  else
      return send_id(cl);
}

int send_metakey(connection_t *cl)
{
  char *buffer;
  int len, x;
cp
  len = RSA_size(cl->rsa_key);

  /* Allocate buffers for the meta key */

  buffer = xmalloc(len*2+1);

  if(!cl->cipher_outkey)
    cl->cipher_outkey = xmalloc(len);
    
  if(!cl->cipher_outctx)
    cl->cipher_outctx = xmalloc(sizeof(*cl->cipher_outctx));
cp
  /* Copy random data to the buffer */

  RAND_bytes(cl->cipher_outkey, len);

  cl->cipher_outkey[0] &= 0x7F;	/* FIXME: Somehow if the first byte is more than 0xD0 or something like that, decryption fails... */

  if(debug_lvl >= DEBUG_SCARY_THINGS)
    {
      bin2hex(cl->cipher_outkey, buffer, len);
      buffer[len*2] = '\0';
      syslog(LOG_DEBUG, _("Generated random meta key (unencrypted): %s"), buffer);
    }

  /* Encrypt the random data */
  
  if(RSA_public_encrypt(len, cl->cipher_outkey, buffer, cl->rsa_key, RSA_NO_PADDING) != len)	/* NO_PADDING because the message size equals the RSA key size and it is totally random */
    {
      syslog(LOG_ERR, _("Error during encryption of meta key for %s (%s)"), cl->name, cl->hostname);
      free(buffer);
      return -1;
    }
cp
  /* Convert the encrypted random data to a hexadecimal formatted string */

  bin2hex(buffer, buffer, len);
  buffer[len*2] = '\0';

  /* Send the meta key */

  if(cl->status.outgoing)
    cl->allow_request = METAKEY;
  else
    cl->allow_request = ACK;
    
  x = send_request(cl, "%d %s", METAKEY, buffer);
  free(buffer);

  EVP_EncryptInit(cl->cipher_outctx, EVP_bf_cfb(), cl->cipher_outkey, cl->cipher_outkey + EVP_bf_cfb()->key_len);
cp
  return x;
}

int metakey_h(connection_t *cl)
{
  char buffer[MAX_STRING_SIZE];
  int len;
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING, buffer) != 1)
    {
       syslog(LOG_ERR, _("Got bad METAKEY from %s (%s)"), cl->name, cl->hostname);
       return -1;
    }

  len = RSA_size(myself->rsa_key);

  /* Check if the length of the meta key is all right */

  if(strlen(buffer) != len*2)
    {
      syslog(LOG_ERR, _("Intruder: wrong meta key length from %s (%s)"), cl->name, cl->hostname);
      return -1;
    }

  /* Allocate buffers for the meta key */

  if(!cl->cipher_inkey)
    cl->cipher_inkey = xmalloc(len);

  if(!cl->cipher_inctx)
    cl->cipher_inctx = xmalloc(sizeof(*cl->cipher_inctx));

  /* Convert the challenge from hexadecimal back to binary */

  hex2bin(buffer,buffer,len);

  /* Decrypt the meta key */
  
  if(RSA_private_decrypt(len, buffer, cl->cipher_inkey, myself->rsa_key, RSA_NO_PADDING) != len)	/* See challenge() */
    {
      syslog(LOG_ERR, _("Error during encryption of meta key for %s (%s)"), cl->name, cl->hostname);
      return -1;
    }

  if(debug_lvl >= DEBUG_SCARY_THINGS)
    {
      bin2hex(cl->cipher_inkey, buffer, len);
      buffer[len*2] = '\0';
      syslog(LOG_DEBUG, _("Received random meta key (unencrypted): %s"), buffer);
    }

  EVP_DecryptInit(cl->cipher_inctx, EVP_bf_cfb(), cl->cipher_inkey, cl->cipher_inkey + EVP_bf_cfb()->key_len);
  
cp
  if(cl->status.outgoing)
    return send_ack(cl);
  else
    return send_metakey(cl);
}

int send_ack(connection_t *cl)
{
  int x;
cp
  if(cl->status.outgoing)
    cl->allow_request = ACK;

  x = send_request(cl, "%d", ACK);
  cl->status.encryptout = 1;
cp
  return x;
}

int ack_h(connection_t *cl)
{
  connection_t *old, *p;
  subnet_t *subnet;
  avl_node_t *node, *node2;
cp
  /* Okay, before we active the connection, we check if there is another entry
     in the connection list with the same name. If so, it presumably is an
     old connection that has timed out but we don't know it yet.
   */

  while((old = lookup_id(cl->name)))
    {
      if(debug_lvl >= DEBUG_CONNECTIONS)
        syslog(LOG_NOTICE, _("Removing old entry for %s at %s in favour of new connection from %s"),
        cl->name, old->hostname, cl->hostname);

      terminate_connection(old);
    }

  /* Activate this connection */

  cl->allow_request = ALL;
  cl->status.active = 1;
  cl->status.decryptin = 1;
  cl->nexthop = cl;
  cl->cipher_pkttype = EVP_bf_cfb();
  cl->cipher_pktkeylength = cl->cipher_pkttype->key_len + cl->cipher_pkttype->iv_len;

  if(debug_lvl >= DEBUG_CONNECTIONS)
    syslog(LOG_NOTICE, _("Connection with %s (%s) activated"), cl->name, cl->hostname);

cp
  if(!cl->status.outgoing)
    send_ack(cl);

  /* Send him our subnets */
  
  for(node = myself->subnet_tree->head; node; node = node->next)
    {
      subnet = (subnet_t *)node->data;
      send_add_subnet(cl, subnet);
    }
  /* And send him all the hosts and their subnets we know... */
  
  for(node = connection_tree->head; node; node = node->next)
    {
      p = (connection_t *)node->data;
      
      if(p != cl && p->status.active)
        {
          /* Notify others of this connection */

          if(p->status.meta)
            send_add_host(p, cl);

          /* Notify new connection of everything we know */

          send_add_host(cl, p);

          for(node2 = p->subnet_tree->head; node2; node2 = node2->next)
            {
              subnet = (subnet_t *)node2->data;
              send_add_subnet(cl, subnet);
            }
        }
    }  
cp
  return 0;
}

/* Address and subnet information exchange */

int send_add_subnet(connection_t *cl, subnet_t *subnet)
{
  int x;
  char *netstr;
cp
  x = send_request(cl, "%d %s %s", ADD_SUBNET,
                      subnet->owner->name, netstr = net2str(subnet));
  free(netstr);
cp
  return x;
}

int add_subnet_h(connection_t *cl)
{
  char subnetstr[MAX_STRING_SIZE];
  char name[MAX_STRING_SIZE];
  connection_t *owner, *p;
  subnet_t *subnet;
  avl_node_t *node;
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING" "MAX_STRING, name, subnetstr) != 2)
    {
      syslog(LOG_ERR, _("Got bad ADD_SUBNET from %s (%s)"), cl->name, cl->hostname);
      return -1;
    }

  /* Check if owner name is a valid */

  if(check_id(name))
    {
      syslog(LOG_ERR, _("Got bad ADD_SUBNET from %s (%s): invalid identity name"), cl->name, cl->hostname);
      return -1;
    }

  /* Check if subnet string is valid */

  if(!(subnet = str2net(subnetstr)))
    {
      syslog(LOG_ERR, _("Got bad ADD_SUBNET from %s (%s): invalid subnet string"), cl->name, cl->hostname);
      return -1;
    }

  /* Check if somebody tries to add a subnet of ourself */

  if(!strcmp(name, myself->name))
    {
      syslog(LOG_ERR, _("Warning: got ADD_SUBNET from %s (%s) for ourself, restarting"),
             cl->name, cl->hostname);
      sighup = 1;
      return 0;
    }

  /* Check if the owner of the new subnet is in the connection list */

  if(!(owner = lookup_id(name)))
    {
      syslog(LOG_ERR, _("Got ADD_SUBNET for %s from %s (%s) which is not in our connection list"),
             name, cl->name, cl->hostname);
      return -1;
    }

  /* If everything is correct, add the subnet to the list of the owner */

  subnet_add(owner, subnet);

  /* Tell the rest */
  
  for(node = connection_tree->head; node; node = node->next)
    {
      p = (connection_t *)node->data;
      if(p->status.meta && p->status.active && p!= cl)
        send_add_subnet(p, subnet);
    }
cp
  return 0;
}

int send_del_subnet(connection_t *cl, subnet_t *subnet)
{
  int x;
  char *netstr;
cp
  netstr = net2str(subnet);
  x = send_request(cl, "%d %s %s", DEL_SUBNET, subnet->owner->name, netstr);
  free(netstr);
cp
  return x;
}

int del_subnet_h(connection_t *cl)
{
  char subnetstr[MAX_STRING_SIZE];
  char name[MAX_STRING_SIZE];
  connection_t *owner, *p;
  subnet_t *subnet;
  avl_node_t *node;
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING" "MAX_STRING, name, subnetstr) != 3)
    {
      syslog(LOG_ERR, _("Got bad DEL_SUBNET from %s (%s)"), cl->name, cl->hostname);
      return -1;
    }

  /* Check if owner name is a valid */

  if(check_id(name))
    {
      syslog(LOG_ERR, _("Got bad DEL_SUBNET from %s (%s): invalid identity name"), cl->name, cl->hostname);
      return -1;
    }

  /* Check if subnet string is valid */

  if(!(subnet = str2net(subnetstr)))
    {
      syslog(LOG_ERR, _("Got bad DEL_SUBNET from %s (%s): invalid subnet string"), cl->name, cl->hostname);
      return -1;
    }

  free(subnetstr);
  
  /* Check if somebody tries to add a subnet of ourself */

  if(!strcmp(name, myself->name))
    {
      syslog(LOG_ERR, _("Warning: got DEL_SUBNET from %s (%s) for ourself, restarting"),
             cl->name, cl->hostname);
      sighup = 1;
      return 0;
    }

  /* Check if the owner of the new subnet is in the connection list */

  if(!(owner = lookup_id(name)))
    {
      syslog(LOG_ERR, _("Got DEL_SUBNET for %s from %s (%s) which is not in our connection list"),
             name, cl->name, cl->hostname);
      return -1;
    }

  /* If everything is correct, delete the subnet from the list of the owner */

  subnet_del(subnet);

  /* Tell the rest */
  
  for(node = connection_tree->head; node; node = node->next)
    {
      p = (connection_t *)node->data;
      if(p->status.meta && p->status.active && p!= cl)
        send_del_subnet(p, subnet);
    }
cp
  return 0;
}

/* New and closed connections notification */

int send_add_host(connection_t *cl, connection_t *other)
{
cp
  return send_request(cl, "%d %s %lx:%d %lx", ADD_HOST,
                      other->name, other->address, other->port, other->options);
}

int add_host_h(connection_t *cl)
{
  connection_t *old, *new, *p;
  char name[MAX_STRING_SIZE];
  avl_node_t *node;
cp
  new = new_connection();

  if(sscanf(cl->buffer, "%*d "MAX_STRING" %lx:%d %lx", name, &new->address, &new->port, &new->options) != 4)
    {
       syslog(LOG_ERR, _("Got bad ADD_HOST from %s (%s)"), cl->name, cl->hostname);
       return -1;
    }

  /* Check if identity is a valid name */

  if(check_id(name))
    {
      syslog(LOG_ERR, _("Got bad ADD_HOST from %s (%s): invalid identity name"), cl->name, cl->hostname);
      free_connection(new);
      return -1;
    }

  /* Check if somebody tries to add ourself */

  if(!strcmp(name, myself->name))
    {
      syslog(LOG_ERR, _("Warning: got ADD_HOST from %s (%s) for ourself, restarting"), cl->name, cl->hostname);
      sighup = 1;
      free_connection(new);
      return 0;
    }
    
  /* Fill in more of the new connection structure */

  new->hostname = hostlookup(htonl(new->address));

  /* Check if the new host already exists in the connnection list */

  if((old = lookup_id(name)))
    {
      if((new->address == old->address) && (new->port == old->port))
        {
          if(debug_lvl >= DEBUG_CONNECTIONS)
            syslog(LOG_NOTICE, _("Got duplicate ADD_HOST for %s (%s) from %s (%s)"),
                   old->name, old->hostname, name, new->hostname);
          free_connection(new);
          return 0;
        }
      else
        {
          if(debug_lvl >= DEBUG_CONNECTIONS)
            syslog(LOG_NOTICE, _("Removing old entry for %s (%s) in favour of new connection"),
                   old->name, old->hostname);

          terminate_connection(old);
        }
    }

  /* Hook it up into the connection */

  new->name = xstrdup(name);
  connection_add(new);
  id_add(new);

  /* Tell the rest about the new host */

  for(node = connection_tree->head; node; node = node->next)
    {
      p = (connection_t *)node->data;
      if(p->status.meta && p->status.active && p!=cl)
        send_add_host(p, new);
    }

  /* Fill in rest of connection structure */

  new->nexthop = cl;
  new->status.active = 1;
  new->cipher_pkttype = EVP_bf_cfb();
  new->cipher_pktkeylength = cl->cipher_pkttype->key_len + cl->cipher_pkttype->iv_len;
cp
  return 0;
}

int send_del_host(connection_t *cl, connection_t *other)
{
cp
  return send_request(cl, "%d %s %lx:%d %lx", DEL_HOST,
                      other->name, other->address, other->port, other->options);
}

int del_host_h(connection_t *cl)
{
  char name[MAX_STRING_SIZE];
  ip_t address;
  port_t port;
  long int options;
  connection_t *old, *p;
  avl_node_t *node;
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING" %lx:%d %lx", name, &address, &port, &options) != 4)
    {
      syslog(LOG_ERR, _("Got bad DEL_HOST from %s (%s)"),
             cl->name, cl->hostname);
      return -1;
    }

  /* Check if identity is a valid name */

  if(check_id(name))
    {
      syslog(LOG_ERR, _("Got bad DEL_HOST from %s (%s): invalid identity name"), cl->name, cl->hostname);
      return -1;
    }

  /* Check if somebody tries to delete ourself */

  if(!strcmp(name, myself->name))
    {
      syslog(LOG_ERR, _("Warning: got DEL_HOST from %s (%s) for ourself, restarting"),
             cl->name, cl->hostname);
      sighup = 1;
      return 0;
    }

  /* Check if the new host already exists in the connnection list */

  if(!(old = lookup_id(name)))
    {
      syslog(LOG_ERR, _("Got DEL_HOST from %s (%s) for %s which is not in our connection list"),
             name, cl->name, cl->hostname);
      return -1;
    }
  
  /* Check if the rest matches */
  
  if(address!=old->address || port!=old->port || options!=old->options || cl!=old->nexthop)
    {
      syslog(LOG_WARNING, _("Got DEL_HOST from %s (%s) for %s which doesn't match"), cl->name, cl->hostname, old->name);
      return 0;
    }

  /* Ok, since EVERYTHING seems to check out all right, delete it */

  old->status.active = 0;
  terminate_connection(old);

  /* Tell the rest about the new host */

  for(node = connection_tree->head; node; node = node->next)
    {
      p = (connection_t *)node->data;
      if(p->status.meta && p->status.active && p!=cl)
        send_del_host(p, old);
    }
cp
  return 0;
}

/* Status and error notification routines */

int send_status(connection_t *cl, int statusno, char *statusstring)
{
cp
  if(!statusstring)
    statusstring = status_text[statusno];
cp
  return send_request(cl, "%d %d %s", STATUS, statusno, statusstring);
}

int status_h(connection_t *cl)
{
  int statusno;
  char statusstring[MAX_STRING_SIZE];
cp
  if(sscanf(cl->buffer, "%*d %d "MAX_STRING, &statusno, statusstring) != 2)
    {
       syslog(LOG_ERR, _("Got bad STATUS from %s (%s)"),
              cl->name, cl->hostname);
       return -1;
    }

  if(debug_lvl >= DEBUG_STATUS)
    {
      syslog(LOG_NOTICE, _("Status message from %s (%s): %s: %s"),
             cl->name, cl->hostname, status_text[statusno], statusstring);
    }

cp
  return 0;
}

int send_error(connection_t *cl, int errno, char *errstring)
{
cp
  if(!errstring)
    errstring = strerror(errno);
  return send_request(cl, "%d %d %s", ERROR, errno, errstring);
}

int error_h(connection_t *cl)
{
  int errno;
  char errorstring[MAX_STRING_SIZE];
cp
  if(sscanf(cl->buffer, "%*d %d "MAX_STRING, &errno, errorstring) != 2)
    {
       syslog(LOG_ERR, _("Got bad ERROR from %s (%s)"),
              cl->name, cl->hostname);
       return -1;
    }

  if(debug_lvl >= DEBUG_ERROR)
    {
      syslog(LOG_NOTICE, _("Error message from %s (%s): %s: %s"),
             cl->name, cl->hostname, strerror(errno), errorstring);
    }

  terminate_connection(cl);
cp
  return 0;
}

int send_termreq(connection_t *cl)
{
cp
  return send_request(cl, "%d", TERMREQ);
}

int termreq_h(connection_t *cl)
{
cp
  terminate_connection(cl);
cp
  return 0;
}

/* Keepalive routines - FIXME: needs a closer look */

int send_ping(connection_t *cl)
{
cp
  cl->status.pinged = 1;
  cl->last_ping_time = time(NULL);
cp
  return send_request(cl, "%d", PING);
}

int ping_h(connection_t *cl)
{
cp
  return send_pong(cl);
}

int send_pong(connection_t *cl)
{
cp
  return send_request(cl, "%d", PONG);
}

int pong_h(connection_t *cl)
{
cp
  cl->status.pinged = 0;
cp
  return 0;
}

/* Key exchange */

int send_key_changed(connection_t *from, connection_t *cl)
{
  connection_t *p;
  avl_node_t *node;
cp
  for(node = connection_tree->head; node; node = node->next)
    {
      p = (connection_t *)node->data;
      if(p != cl && p->status.meta && p->status.active)
        send_request(p, "%d %s", KEY_CHANGED, from->name);
    }
cp
  return 0;
}

int key_changed_h(connection_t *cl)
{
  char from_id[MAX_STRING_SIZE];
  connection_t *from;
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING, from_id) != 1)
    {
      syslog(LOG_ERR, _("Got bad KEY_CHANGED from %s (%s)"),
             cl->name, cl->hostname);
      return -1;
    }

  if(!(from = lookup_id(from_id)))
    {
      syslog(LOG_ERR, _("Got KEY_CHANGED from %s (%s) origin %s which does not exist in our connection list"),
             cl->name, cl->hostname, from_id);
      return -1;
    }

  from->status.validkey = 0;
  from->status.waitingforkey = 0;

  send_key_changed(from, cl);
cp
  return 0;
}

int send_req_key(connection_t *from, connection_t *to)
{
cp
  return send_request(to->nexthop, "%d %s %s", REQ_KEY,
                      from->name, to->name);
}

int req_key_h(connection_t *cl)
{
  char from_id[MAX_STRING_SIZE];
  char to_id[MAX_STRING_SIZE];
  connection_t *from, *to;
  char pktkey[129];
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING" "MAX_STRING, from_id, to_id) != 2)
    {
       syslog(LOG_ERR, _("Got bad REQ_KEY from %s (%s)"),
              cl->name, cl->hostname);
       return -1;
    }

  if(!(from = lookup_id(from_id)))
    {
      syslog(LOG_ERR, _("Got REQ_KEY from %s (%s) origin %s which does not exist in our connection list"),
             cl->name, cl->hostname, from_id);
      return -1;
    }

  /* Check if this key request is for us */

  if(!strcmp(to_id, myself->name))
    {
      bin2hex(myself->cipher_pktkey, pktkey, myself->cipher_pktkeylength);
      pktkey[myself->cipher_pktkeylength*2] = '\0';
      send_ans_key(myself, from, pktkey);
    }
  else
    {
      if(!(to = lookup_id(to_id)))
        {
          syslog(LOG_ERR, _("Got REQ_KEY from %s (%s) destination %s which does not exist in our connection list"),
                 cl->name, cl->hostname, to_id);
          return -1;
        }
        
      if(to->status.validkey)	/* Proxy keys */
        {
          bin2hex(to->cipher_pktkey, pktkey, to->cipher_pktkeylength);
          pktkey[to->cipher_pktkeylength*2] = '\0';
          send_ans_key(to, from, pktkey);
        }
      else
        send_req_key(from, to);
    }

cp
  return 0;
}

int send_ans_key(connection_t *from, connection_t *to, char *pktkey)
{
cp
  return send_request(to->nexthop, "%d %s %s %s", ANS_KEY,
                      from->name, to->name, pktkey);
}

int ans_key_h(connection_t *cl)
{
  char from_id[MAX_STRING_SIZE];
  char to_id[MAX_STRING_SIZE];
  char pktkey[MAX_STRING_SIZE];
  int keylength;
  connection_t *from, *to;
cp
  if(sscanf(cl->buffer, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING, from_id, to_id, pktkey) != 3)
    {
       syslog(LOG_ERR, _("Got bad ANS_KEY from %s (%s)"),
              cl->name, cl->hostname);
       return -1;
    }

  if(!(from = lookup_id(from_id)))
    {
      syslog(LOG_ERR, _("Got ANS_KEY from %s (%s) origin %s which does not exist in our connection list"),
             cl->name, cl->hostname, from_id);
      return -1;
    }

  /* Check correctness of packet key */

  keylength = strlen(pktkey);

  if(keylength != from->cipher_pktkeylength*2)
    {
      syslog(LOG_ERR, _("Got bad ANS_KEY from %s (%s) origin %s: invalid key length"),
             cl->name, cl->hostname, from->name);
      return -1;
    }

  /* Forward it if necessary */

  if(strcmp(to_id, myself->name))
    {
      if(!(to = lookup_id(to_id)))
        {
          syslog(LOG_ERR, _("Got ANS_KEY from %s (%s) destination %s which does not exist in our connection list"),
                 cl->name, cl->hostname, to_id);
          return -1;
        }
      send_ans_key(from, to, pktkey);
    }

  /* Update our copy of the origin's packet key */

  if(from->cipher_pktkey)
    free(from->cipher_pktkey);

  from->cipher_pktkey = xstrdup(pktkey);
  keylength /= 2;
  hex2bin(from->cipher_pktkey, from->cipher_pktkey, keylength);
  from->cipher_pktkey[keylength] = '\0';

  from->status.validkey = 1;
  from->status.waitingforkey = 0;
cp
  return 0;
}

/* Jumptable for the request handlers */

int (*request_handlers[])(connection_t*) = {
  id_h, challenge_h, chal_reply_h, metakey_h, ack_h,
  status_h, error_h, termreq_h,
  ping_h, pong_h,
  add_host_h, del_host_h,
  add_subnet_h, del_subnet_h,
  key_changed_h, req_key_h, ans_key_h,
};

/* Request names */

char (*request_name[]) = {
  "ID", "CHALLENGE", "CHAL_REPLY", "METAKEY", "ACK",
  "STATUS", "ERROR", "TERMREQ",
  "PING", "PONG",
  "ADD_HOST", "DEL_HOST",
  "ADD_SUBNET", "DEL_SUBNET",
  "KEY_CHANGED", "REQ_KEY", "ANS_KEY",
};

/* Status strings */

char (*status_text[]) = {
  "Warning",
};

/* Error strings */

char (*error_text[]) = {
  "Error",
};