trunk/src/res.c

/*
 *  ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
 *
 *  Copyright (c) 1997-2014 ircd-hybrid development team
 *
 *  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 *  USA
 */

/*! \file res.c
 * \brief ircd resolver functions
 * \version $Id$
 */

/*
 * A rewrite of Darren Reed's original res.c As there is nothing
 * left of Darren's original code, this is now licensed by the hybrid group.
 * (Well, some of the function names are the same, and bits of the structs..)
 * You can use it where it is useful, free even. Buy us a beer and stuff.
 *
 * The authors takes no responsibility for any damage or loss
 * of property which results from the use of this software.
 *
 * July 1999 - Rewrote a bunch of stuff here. Change hostent builder code,
 *     added callbacks and reference counting of returned hostents.
 *     --Bleep (Thomas Helvey <tomh@inxpress.net>)
 *
 * This was all needlessly complicated for irc. Simplified. No more hostent
 * All we really care about is the IP -> hostname mappings. That's all.
 *
 * Apr 28, 2003 --cryogen and Dianora
 */

#include "stdinc.h"
#include "list.h"
#include "client.h"
#include "event.h"
#include "irc_string.h"
#include "ircd.h"
#include "numeric.h"
#include "rng_mt.h"
#include "fdlist.h"
#include "s_bsd.h"
#include "log.h"
#include "misc.h"
#include "send.h"
#include "memory.h"
#include "mempool.h"
#include "res.h"
#include "reslib.h"

#if (CHAR_BIT != 8)
#error this code needs to be able to address individual octets
#endif

static PF res_readreply;

#define MAXPACKET      1024  /**< rfc says 512 but we expand names so ... */
#define AR_TTL         600   /**< TTL in seconds for dns cache entries */

/*
 * RFC 1104/1105 wasn't very helpful about what these fields
 * should be named, so for now, we'll just name them this way.
 * We probably should look at what named calls them or something.
 */
#define TYPE_SIZE         (size_t)2
#define CLASS_SIZE        (size_t)2
#define TTL_SIZE          (size_t)4
#define RDLENGTH_SIZE     (size_t)2
#define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)

typedef enum
{
  REQ_IDLE,  /**< We're doing not much at all */
  REQ_PTR,   /**< Looking up a PTR */
  REQ_A,     /**< Looking up an A, possibly because AAAA failed */
  REQ_AAAA,  /**< Looking up an AAAA */
  REQ_CNAME  /**< We got a CNAME in response, we better get a real answer next */
} request_state;

struct reslist
{
  dlink_node node;                           /**< Doubly linked list node. */
  int id;                                    /**< Request ID (from request header). */
  int sent;                                  /**< Number of requests sent */
  request_state state;                       /**< State the resolver machine is in */
  char type;                                 /**< Current request type. */
  char retries;                              /**< Retry counter */
  unsigned int sends;                        /**< Number of sends (>1 means resent). */
  time_t sentat;                             /**< Timestamp we last sent this request. */
  time_t timeout;                            /**< When this request times out. */
  struct irc_ssaddr addr;                    /**< Address for this request. */
  char name[RFC1035_MAX_DOMAIN_LENGTH + 1];  /**< Hostname for this request. */
  size_t namelength;                         /**< Actual hostname length. */
  dns_callback_fnc callback;                 /**< Callback function on completion. */
  void *callback_ctx;                        /**< Context pointer for callback. */
};

static fde_t ResolverFileDescriptor;
static dlink_list request_list;
static mp_pool_t *dns_pool;


/*
 * rem_request - remove a request from the list.
 * This must also free any memory that has been allocated for
 * temporary storage of DNS results.
 */
static void
rem_request(struct reslist *request)
{
  dlinkDelete(&request->node, &request_list);
  mp_pool_release(request);
}

/*
 * make_request - Create a DNS request record for the server.
 */
static struct reslist *
make_request(dns_callback_fnc callback, void *ctx)
{
  struct reslist *request = mp_pool_get(dns_pool);

  request->sentat       = CurrentTime;
  request->retries      = 2;
  request->timeout      = 4;  /* Start at 4 and exponential inc. */
  request->state        = REQ_IDLE;
  request->callback     = callback;
  request->callback_ctx = ctx;

  dlinkAdd(request, &request->node, &request_list);
  return request;
}

/*
 * int
 * res_ourserver(inp)
 *      looks up "inp" in irc_nsaddr_list[]
 * returns:
 *      0  : not found
 *      >0 : found
 * author:
 *      paul vixie, 29may94
 *      revised for ircd, cryogen(stu) may03
 */
static int
res_ourserver(const struct irc_ssaddr *inp)
{
  const struct sockaddr_in6 *v6;
  const struct sockaddr_in6 *v6in = (const struct sockaddr_in6 *)inp;
  const struct sockaddr_in *v4;
  const struct sockaddr_in *v4in = (const struct sockaddr_in *)inp;

  for (unsigned int i = 0; i < irc_nscount; ++i)
  {
    const struct irc_ssaddr *srv = &irc_nsaddr_list[i];
    v6 = (const struct sockaddr_in6 *)srv;
    v4 = (const struct sockaddr_in *)srv;

    /*
     * Could probably just memcmp(srv, inp, srv.ss_len) here
     * but we'll air on the side of caution - stu
     */
    switch (srv->ss.ss_family)
    {
      case AF_INET6:
        if (srv->ss.ss_family == inp->ss.ss_family)
          if (v6->sin6_port == v6in->sin6_port)
            if (!memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
                        sizeof(struct in6_addr)))
              return 1;
        break;
      case AF_INET:
        if (srv->ss.ss_family == inp->ss.ss_family)
          if (v4->sin_port == v4in->sin_port)
            if (v4->sin_addr.s_addr == v4in->sin_addr.s_addr)
              return 1;
        break;
      default:
        break;
    }
  }

  return 0;
}

/*
 * start_resolver - do everything we need to read the resolv.conf file
 * and initialize the resolver file descriptor if needed
 */
static void
start_resolver(void)
{
  irc_res_init();

  if (!ResolverFileDescriptor.flags.open)
  {
    if (comm_open(&ResolverFileDescriptor, irc_nsaddr_list[0].ss.ss_family,
                  SOCK_DGRAM, 0, "UDP resolver socket") == -1)
      return;

    /* At the moment, the resolver FD data is global .. */
    comm_setselect(&ResolverFileDescriptor, COMM_SELECT_READ, res_readreply, NULL, 0);
  }
}

/*
 * restart_resolver - reread resolv.conf, reopen socket
 */
void
restart_resolver(void)
{
  fd_close(&ResolverFileDescriptor);
  start_resolver();
}

/*
 * delete_resolver_queries - cleanup outstanding queries
 * for which there no longer exist clients or conf lines.
 */
void
delete_resolver_queries(const void *vptr)
{
  dlink_node *ptr = NULL, *ptr_next = NULL;

  DLINK_FOREACH_SAFE(ptr, ptr_next, request_list.head)
  {
    struct reslist *request = ptr->data;

    if (request->callback_ctx == vptr)
      rem_request(request);
  }
}

/*
 * send_res_msg - sends msg to all nameservers found in the "_res" structure.
 * This should reflect /etc/resolv.conf. We will get responses
 * which arent needed but is easier than checking to see if nameserver
 * isn't present. Returns number of messages successfully sent to
 * nameservers or -1 if no successful sends.
 */
static int
send_res_msg(const char *msg, int len, unsigned int rcount)
{
  int sent = 0;
  unsigned int max_queries = IRCD_MIN(irc_nscount, rcount);

  /* RES_PRIMARY option is not implemented
   * if (res.options & RES_PRIMARY || 0 == max_queries)
   */
  if (max_queries == 0)
    max_queries = 1;

  for (unsigned int i = 0; i < max_queries; ++i)
  {
    if (sendto(ResolverFileDescriptor.fd, msg, len, 0,
        (struct sockaddr*)&(irc_nsaddr_list[i]),
        irc_nsaddr_list[i].ss_len) == len)
      ++sent;
  }

  return sent;
}

/*
 * find_id - find a dns request id (id is determined by dn_mkquery)
 */
static struct reslist *
find_id(int id)
{
  dlink_node *ptr = NULL;

  DLINK_FOREACH(ptr, request_list.head)
  {
    struct reslist *request = ptr->data;

    if (request->id == id)
      return request;
  }

  return NULL;
}

/*
 * query_name - generate a query based on class, type and name.
 */
static void
query_name(const char *name, int query_class, int type,
           struct reslist *request)
{
  char buf[MAXPACKET];
  int request_len = 0;

  memset(buf, 0, sizeof(buf));

  if ((request_len = irc_res_mkquery(name, query_class, type,
      (unsigned char *)buf, sizeof(buf))) > 0)
  {
    HEADER *header = (HEADER *)buf;

    /*
     * Generate an unique id.
     * NOTE: we don't have to worry about converting this to and from
     * network byte order, the nameserver does not interpret this value
     * and returns it unchanged.
     */
    do
      header->id = (header->id + genrand_int32()) & 0xFFFF;
    while (find_id(header->id));

    request->id = header->id;
    ++request->sends;

    request->sent += send_res_msg(buf, request_len, request->sends);
  }
}

/*
 * do_query_name - nameserver lookup name
 */
static void
do_query_name(dns_callback_fnc callback, void *ctx, const char *name,
              struct reslist *request, int type)
{
  char host_name[RFC1035_MAX_DOMAIN_LENGTH + 1];

  strlcpy(host_name, name, sizeof(host_name));

  if (request == NULL)
  {
    request             = make_request(callback, ctx);
    request->type       = type;
    request->namelength = strlcpy(request->name, host_name, sizeof(request->name));
  }

  request->type = type;
  query_name(host_name, C_IN, type, request);
}

/*
 * do_query_number - Use this to do reverse IP# lookups.
 */
static void
do_query_number(dns_callback_fnc callback, void *ctx,
                const struct irc_ssaddr *addr,
                struct reslist *request)
{
  char ipbuf[128] = "";

  if (addr->ss.ss_family == AF_INET)
  {
    const struct sockaddr_in *v4 = (const struct sockaddr_in *)addr;
    const unsigned char *cp = (const unsigned char *)&v4->sin_addr.s_addr;

    snprintf(ipbuf, sizeof(ipbuf), "%u.%u.%u.%u.in-addr.arpa.",
             (unsigned int)(cp[3]), (unsigned int)(cp[2]),
             (unsigned int)(cp[1]), (unsigned int)(cp[0]));
  }
  else if (addr->ss.ss_family == AF_INET6)
  {
    const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr;
    const unsigned char *cp = (const unsigned char *)&v6->sin6_addr.s6_addr;

    snprintf(ipbuf, sizeof(ipbuf),
             "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
             "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa.",
             (unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
             (unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
             (unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
             (unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
             (unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
             (unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
             (unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
             (unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
             (unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
             (unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
             (unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
             (unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
             (unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
             (unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
             (unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
             (unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
  }

  if (request == NULL)
  {
    request       = make_request(callback, ctx);
    request->type = T_PTR;
    memcpy(&request->addr, addr, sizeof(struct irc_ssaddr));
  }

  query_name(ipbuf, C_IN, T_PTR, request);
}

/*
 * gethost_byname_type - get host address from name
 *
 */
void
gethost_byname_type(dns_callback_fnc callback, void *ctx, const char *name, int type)
{
  assert(name);
  do_query_name(callback, ctx, name, NULL, type);
}

/*
 * gethost_byname - wrapper for _type - send T_AAAA first if IPV6 supported
 */
void
gethost_byname(dns_callback_fnc callback, void *ctx, const char *name)
{
  gethost_byname_type(callback, ctx, name, T_AAAA);
}

/*
 * gethost_byaddr - get host name from address
 */
void
gethost_byaddr(dns_callback_fnc callback, void *ctx, const struct irc_ssaddr *addr)
{
  do_query_number(callback, ctx, addr, NULL);
}

static void
resend_query(struct reslist *request)
{
  switch (request->type)
  {
    case T_PTR:
      do_query_number(NULL, NULL, &request->addr, request);
      break;
    case T_A:
    case T_AAAA:
      do_query_name(NULL, NULL, request->name, request, request->type);
      break;
    default:
      break;
  }
}

/*
 * proc_answer - process name server reply
 */
static int
proc_answer(struct reslist *request, HEADER *header, char *buf, char *eob)
{
  char hostbuf[RFC1035_MAX_DOMAIN_LENGTH + 100]; /* working buffer */
  unsigned char *current;      /* current position in buf */
  int type;                    /* answer type */
  int n;                       /* temp count */
  int rd_length;
  struct sockaddr_in *v4;      /* conversion */
  struct sockaddr_in6 *v6;

  current = (unsigned char *)buf + sizeof(HEADER);

  for (; header->qdcount > 0; --header->qdcount)
  {
    if ((n = irc_dn_skipname(current, (unsigned char *)eob)) < 0)
      break;

    current += (size_t)n + QFIXEDSZ;
  }

  /*
   * Process each answer sent to us blech.
   */
  while (header->ancount > 0 && (char *)current < eob)
  {
    header->ancount--;

    n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current,
        hostbuf, sizeof(hostbuf));

    if (n < 0  /* Broken message */ || n == 0  /* No more answers left */)
      return 0;

    hostbuf[RFC1035_MAX_DOMAIN_LENGTH] = '\0';

    /*
     * With Address arithmetic you have to be very anal
     * this code was not working on alpha due to that
     * (spotted by rodder/jailbird/dianora)
     */
    current += (size_t)n;

    if (!(((char *)current + ANSWER_FIXED_SIZE) < eob))
      break;

    type = irc_ns_get16(current);
    current += TYPE_SIZE;
    current += CLASS_SIZE;
    current += TTL_SIZE;
    rd_length = irc_ns_get16(current);
    current += RDLENGTH_SIZE;

    /*
     * Wait to set request->type until we verify this structure
     */
    switch (type)
    {
      case T_A:
        if (request->type != T_A)
          return 0;

        /*
         * Check for invalid rd_length or too many addresses
         */
        if (rd_length != sizeof(struct in_addr))
          return 0;

        v4 = (struct sockaddr_in *)&request->addr;
        request->addr.ss_len = sizeof(struct sockaddr_in);
        v4->sin_family = AF_INET;
        memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
        return 1;
        break;
      case T_AAAA:
        if (request->type != T_AAAA)
          return 0;

        if (rd_length != sizeof(struct in6_addr))
          return 0;

        request->addr.ss_len = sizeof(struct sockaddr_in6);
        v6 = (struct sockaddr_in6 *)&request->addr;
        v6->sin6_family = AF_INET6;
        memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
        return 1;
        break;
      case T_PTR:
        if (request->type != T_PTR)
          return 0;

        n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob,
                          current, hostbuf, sizeof(hostbuf));
        if (n < 0  /* Broken message */ || n == 0  /* No more answers left */)
          return 0;

        request->namelength = strlcpy(request->name, hostbuf, sizeof(request->name));
        return 1;
        break;
      case T_CNAME:
        current += rd_length;
        break;

      default:
        /* XXX I'd rather just throw away the entire bogus thing
         * but its possible its just a broken nameserver with still
         * valid answers. But lets do some rudimentary logging for now...
         */
        ilog(LOG_TYPE_IRCD, "irc_res.c bogus type %d", type);
        break;
    }
  }

  return 1;
}

/*
 * res_readreply - read a dns reply from the nameserver and process it.
 */
static void
res_readreply(fde_t *fd, void *data)
{
  char buf[sizeof(HEADER) + MAXPACKET];
  HEADER *header;
  struct reslist *request = NULL;
  ssize_t rc = 0;
  socklen_t len = sizeof(struct irc_ssaddr);
  struct irc_ssaddr lsin;

  while ((rc = recvfrom(fd->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len)) != -1)
  {
    if (rc <= (ssize_t)sizeof(HEADER))
      continue;

    /*
     * Check against possibly fake replies
     */
    if (!res_ourserver(&lsin))
      continue;

    /*
     * Convert DNS reply reader from Network byte order to CPU byte order.
     */
    header = (HEADER *)buf;
    header->ancount = ntohs(header->ancount);
    header->qdcount = ntohs(header->qdcount);
    header->nscount = ntohs(header->nscount);
    header->arcount = ntohs(header->arcount);

    /*
     * Response for an id which we have already received an answer for
     * just ignore this response.
     */
    if ((request = find_id(header->id)) == NULL)
      continue;

    if (header->rcode != NO_ERRORS || header->ancount == 0)
    {
      /*
       * If a bad error was returned, stop here and don't
       * send any more (no retries granted).
       */
      (*request->callback)(request->callback_ctx, NULL, NULL, 0);
      rem_request(request);
      continue;
    }

    /*
     * If this fails there was an error decoding the received packet.
     * We only give it one shot. If it fails, just leave the client
     * unresolved.
     */
    if (!proc_answer(request, header, buf, buf + rc))
    {
      (*request->callback)(request->callback_ctx, NULL, NULL, 0);
      rem_request(request);
      continue;
    }

    if (request->type == T_PTR)
    {
      if (request->namelength == 0)
      {
        /*
         * Got a PTR response with no name, something bogus is happening
         * don't bother trying again, the client address doesn't resolve
         */
        (*request->callback)(request->callback_ctx, NULL, NULL, 0);
        rem_request(request);
        continue;
      }

      /*
       * Lookup the 'authoritative' name that we were given for the ip#.
       */
      if (request->addr.ss.ss_family == AF_INET6)
        gethost_byname_type(request->callback, request->callback_ctx, request->name, T_AAAA);
      else
        gethost_byname_type(request->callback, request->callback_ctx, request->name, T_A);
      rem_request(request);
    }
    else
    {
      /*
       * Got a name and address response, client resolved
       */
      (*request->callback)(request->callback_ctx, &request->addr, request->name, request->namelength);
      rem_request(request);
    }

    continue;
  }

  comm_setselect(fd, COMM_SELECT_READ, res_readreply, NULL, 0);
}

void
report_dns_servers(struct Client *source_p)
{
  char ipaddr[HOSTIPLEN + 1] = "";

  for (unsigned int i = 0; i < irc_nscount; ++i)
  {
    getnameinfo((struct sockaddr *)&(irc_nsaddr_list[i]),
                irc_nsaddr_list[i].ss_len, ipaddr,
                sizeof(ipaddr), NULL, 0, NI_NUMERICHOST);
    sendto_one_numeric(source_p, &me, RPL_STATSALINE, ipaddr);
  }
}

/*
 * timeout_query_list - Remove queries from the list which have been
 * there too long without being resolved.
 */
static time_t
timeout_query_list(void)
{
  dlink_node *ptr = NULL, *ptr_next = NULL;
  struct reslist *request = NULL;
  time_t next_time = 0;
  time_t timeout   = 0;

  DLINK_FOREACH_SAFE(ptr, ptr_next, request_list.head)
  {
    request = ptr->data;
    timeout = request->sentat + request->timeout;

    if (CurrentTime >= timeout)
    {
      if (--request->retries <= 0)
      {
        (*request->callback)(request->callback_ctx, NULL, NULL, 0);
        rem_request(request);
        continue;
      }
      else
      {
        request->sentat = CurrentTime;
        request->timeout += request->timeout;
        resend_query(request);
      }
    }

    if (next_time == 0 || timeout < next_time)
      next_time = timeout;
  }

  return (next_time > CurrentTime) ? next_time : (CurrentTime + AR_TTL);
}

/*
 * timeout_resolver - check request list
 */
static void
timeout_resolver(void *unused)
{
  timeout_query_list();
}

/*
 * init_resolver - initialize resolver and resolver library
 */
void
init_resolver(void)
{
  static struct event event_timeout_resolver =
  {
    .name = "timeout_resolver",
    .handler = timeout_resolver,
    .when = 1
  };

  dns_pool = mp_pool_new(sizeof(struct reslist), MP_CHUNK_SIZE_DNS);

  start_resolver();
  event_add(&event_timeout_resolver, NULL);
}
Revision:	4452
Committed:	Mon Aug 11 15:51:47 2014 UTC (11 years ago) by michael
Content type:	text/x-csrc
File size:	21384 byte(s)
Log Message:	- res.c:proc_answer(): applied "Ignore CNAME records in dns queries" fix from p4. ** Ignore CNAME records in dns queries. Allows PTRS to point to CNAMEs which can point to an A/AAAA which resolves to the correct IP.
#	Content
1	/*
2	* ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
3	*
4	* Copyright (c) 1997-2014 ircd-hybrid development team
5	*
6	* This program is free software; you can redistribute it and/or modify
7	* it under the terms of the GNU General Public License as published by
8	* the Free Software Foundation; either version 2 of the License, or
9	* (at your option) any later version.
10	*
11	* This program is distributed in the hope that it will be useful,
12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14	* GNU General Public License for more details.
15	*
16	* You should have received a copy of the GNU General Public License
17	* along with this program; if not, write to the Free Software
18	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
19	* USA
20	*/
21
22	/*! \file res.c
23	* \brief ircd resolver functions
24	* \version $Id$
25	*/
26
27	/*
28	* A rewrite of Darren Reed's original res.c As there is nothing
29	* left of Darren's original code, this is now licensed by the hybrid group.
30	* (Well, some of the function names are the same, and bits of the structs..)
31	* You can use it where it is useful, free even. Buy us a beer and stuff.
32	*
33	* The authors takes no responsibility for any damage or loss
34	* of property which results from the use of this software.
35	*
36	* July 1999 - Rewrote a bunch of stuff here. Change hostent builder code,
37	* added callbacks and reference counting of returned hostents.
38	* --Bleep (Thomas Helvey <tomh@inxpress.net>)
39	*
40	* This was all needlessly complicated for irc. Simplified. No more hostent
41	* All we really care about is the IP -> hostname mappings. That's all.
42	*
43	* Apr 28, 2003 --cryogen and Dianora
44	*/
45
46	#include "stdinc.h"
47	#include "list.h"
48	#include "client.h"
49	#include "event.h"
50	#include "irc_string.h"
51	#include "ircd.h"
52	#include "numeric.h"
53	#include "rng_mt.h"
54	#include "fdlist.h"
55	#include "s_bsd.h"
56	#include "log.h"
57	#include "misc.h"
58	#include "send.h"
59	#include "memory.h"
60	#include "mempool.h"
61	#include "res.h"
62	#include "reslib.h"
63
64	#if (CHAR_BIT != 8)
65	#error this code needs to be able to address individual octets
66	#endif
67
68	static PF res_readreply;
69
70	#define MAXPACKET 1024 /*< rfc says 512 but we expand names so ... /
71	#define AR_TTL 600 /*< TTL in seconds for dns cache entries /
72
73	/*
74	* RFC 1104/1105 wasn't very helpful about what these fields
75	* should be named, so for now, we'll just name them this way.
76	* We probably should look at what named calls them or something.
77	*/
78	#define TYPE_SIZE (size_t)2
79	#define CLASS_SIZE (size_t)2
80	#define TTL_SIZE (size_t)4
81	#define RDLENGTH_SIZE (size_t)2
82	#define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)
83
84	typedef enum
85	{
86	REQ_IDLE, /*< We're doing not much at all /
87	REQ_PTR, /*< Looking up a PTR /
88	REQ_A, /*< Looking up an A, possibly because AAAA failed /
89	REQ_AAAA, /*< Looking up an AAAA /
90	REQ_CNAME /*< We got a CNAME in response, we better get a real answer next /
91	} request_state;
92
93	struct reslist
94	{
95	dlink_node node; /*< Doubly linked list node. /
96	int id; /*< Request ID (from request header). /
97	int sent; /*< Number of requests sent /
98	request_state state; /*< State the resolver machine is in /
99	char type; /*< Current request type. /
100	char retries; /*< Retry counter /
101	unsigned int sends; /*< Number of sends (>1 means resent). /
102	time_t sentat; /*< Timestamp we last sent this request. /
103	time_t timeout; /*< When this request times out. /
104	struct irc_ssaddr addr; /*< Address for this request. /
105	char name[RFC1035_MAX_DOMAIN_LENGTH + 1]; /*< Hostname for this request. /
106	size_t namelength; /*< Actual hostname length. /
107	dns_callback_fnc callback; /*< Callback function on completion. /
108	void callback_ctx; /< Context pointer for callback. /
109	};
110
111	static fde_t ResolverFileDescriptor;
112	static dlink_list request_list;
113	static mp_pool_t *dns_pool;
114
115
116	/*
117	* rem_request - remove a request from the list.
118	* This must also free any memory that has been allocated for
119	* temporary storage of DNS results.
120	*/
121	static void
122	rem_request(struct reslist *request)
123	{
124	dlinkDelete(&request->node, &request_list);
125	mp_pool_release(request);
126	}
127
128	/*
129	* make_request - Create a DNS request record for the server.
130	*/
131	static struct reslist *
132	make_request(dns_callback_fnc callback, void *ctx)
133	{
134	struct reslist *request = mp_pool_get(dns_pool);
135
136	request->sentat = CurrentTime;
137	request->retries = 2;
138	request->timeout = 4; /* Start at 4 and exponential inc. */
139	request->state = REQ_IDLE;
140	request->callback = callback;
141	request->callback_ctx = ctx;
142
143	dlinkAdd(request, &request->node, &request_list);
144	return request;
145	}
146
147	/*
148	* int
149	* res_ourserver(inp)
150	* looks up "inp" in irc_nsaddr_list[]
151	* returns:
152	* 0 : not found
153	* >0 : found
154	* author:
155	* paul vixie, 29may94
156	* revised for ircd, cryogen(stu) may03
157	*/
158	static int
159	res_ourserver(const struct irc_ssaddr *inp)
160	{
161	const struct sockaddr_in6 *v6;
162	const struct sockaddr_in6 v6in = (const struct sockaddr_in6 )inp;
163	const struct sockaddr_in *v4;
164	const struct sockaddr_in v4in = (const struct sockaddr_in )inp;
165
166	for (unsigned int i = 0; i < irc_nscount; ++i)
167	{
168	const struct irc_ssaddr *srv = &irc_nsaddr_list[i];
169	v6 = (const struct sockaddr_in6 *)srv;
170	v4 = (const struct sockaddr_in *)srv;
171
172	/*
173	* Could probably just memcmp(srv, inp, srv.ss_len) here
174	* but we'll air on the side of caution - stu
175	*/
176	switch (srv->ss.ss_family)
177	{
178	case AF_INET6:
179	if (srv->ss.ss_family == inp->ss.ss_family)
180	if (v6->sin6_port == v6in->sin6_port)
181	if (!memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr,
182	sizeof(struct in6_addr)))
183	return 1;
184	break;
185	case AF_INET:
186	if (srv->ss.ss_family == inp->ss.ss_family)
187	if (v4->sin_port == v4in->sin_port)
188	if (v4->sin_addr.s_addr == v4in->sin_addr.s_addr)
189	return 1;
190	break;
191	default:
192	break;
193	}
194	}
195
196	return 0;
197	}
198
199	/*
200	* start_resolver - do everything we need to read the resolv.conf file
201	* and initialize the resolver file descriptor if needed
202	*/
203	static void
204	start_resolver(void)
205	{
206	irc_res_init();
207
208	if (!ResolverFileDescriptor.flags.open)
209	{
210	if (comm_open(&ResolverFileDescriptor, irc_nsaddr_list[0].ss.ss_family,
211	SOCK_DGRAM, 0, "UDP resolver socket") == -1)
212	return;
213
214	/* At the moment, the resolver FD data is global .. */
215	comm_setselect(&ResolverFileDescriptor, COMM_SELECT_READ, res_readreply, NULL, 0);
216	}
217	}
218
219	/*
220	* restart_resolver - reread resolv.conf, reopen socket
221	*/
222	void
223	restart_resolver(void)
224	{
225	fd_close(&ResolverFileDescriptor);
226	start_resolver();
227	}
228
229	/*
230	* delete_resolver_queries - cleanup outstanding queries
231	* for which there no longer exist clients or conf lines.
232	*/
233	void
234	delete_resolver_queries(const void *vptr)
235	{
236	dlink_node ptr = NULL, ptr_next = NULL;
237
238	DLINK_FOREACH_SAFE(ptr, ptr_next, request_list.head)
239	{
240	struct reslist *request = ptr->data;
241
242	if (request->callback_ctx == vptr)
243	rem_request(request);
244	}
245	}
246
247	/*
248	* send_res_msg - sends msg to all nameservers found in the "_res" structure.
249	* This should reflect /etc/resolv.conf. We will get responses
250	* which arent needed but is easier than checking to see if nameserver
251	* isn't present. Returns number of messages successfully sent to
252	* nameservers or -1 if no successful sends.
253	*/
254	static int
255	send_res_msg(const char *msg, int len, unsigned int rcount)
256	{
257	int sent = 0;
258	unsigned int max_queries = IRCD_MIN(irc_nscount, rcount);
259
260	/* RES_PRIMARY option is not implemented
261	* if (res.options & RES_PRIMARY \|\| 0 == max_queries)
262	*/
263	if (max_queries == 0)
264	max_queries = 1;
265
266	for (unsigned int i = 0; i < max_queries; ++i)
267	{
268	if (sendto(ResolverFileDescriptor.fd, msg, len, 0,
269	(struct sockaddr*)&(irc_nsaddr_list[i]),
270	irc_nsaddr_list[i].ss_len) == len)
271	++sent;
272	}
273
274	return sent;
275	}
276
277	/*
278	* find_id - find a dns request id (id is determined by dn_mkquery)
279	*/
280	static struct reslist *
281	find_id(int id)
282	{
283	dlink_node *ptr = NULL;
284
285	DLINK_FOREACH(ptr, request_list.head)
286	{
287	struct reslist *request = ptr->data;
288
289	if (request->id == id)
290	return request;
291	}
292
293	return NULL;
294	}
295
296	/*
297	* query_name - generate a query based on class, type and name.
298	*/
299	static void
300	query_name(const char *name, int query_class, int type,
301	struct reslist *request)
302	{
303	char buf[MAXPACKET];
304	int request_len = 0;
305
306	memset(buf, 0, sizeof(buf));
307
308	if ((request_len = irc_res_mkquery(name, query_class, type,
309	(unsigned char *)buf, sizeof(buf))) > 0)
310	{
311	HEADER header = (HEADER )buf;
312
313	/*
314	* Generate an unique id.
315	* NOTE: we don't have to worry about converting this to and from
316	* network byte order, the nameserver does not interpret this value
317	* and returns it unchanged.
318	*/
319	do
320	header->id = (header->id + genrand_int32()) & 0xFFFF;
321	while (find_id(header->id));
322
323	request->id = header->id;
324	++request->sends;
325
326	request->sent += send_res_msg(buf, request_len, request->sends);
327	}
328	}
329
330	/*
331	* do_query_name - nameserver lookup name
332	*/
333	static void
334	do_query_name(dns_callback_fnc callback, void ctx, const char name,
335	struct reslist *request, int type)
336	{
337	char host_name[RFC1035_MAX_DOMAIN_LENGTH + 1];
338
339	strlcpy(host_name, name, sizeof(host_name));
340
341	if (request == NULL)
342	{
343	request = make_request(callback, ctx);
344	request->type = type;
345	request->namelength = strlcpy(request->name, host_name, sizeof(request->name));
346	}
347
348	request->type = type;
349	query_name(host_name, C_IN, type, request);
350	}
351
352	/*
353	* do_query_number - Use this to do reverse IP# lookups.
354	*/
355	static void
356	do_query_number(dns_callback_fnc callback, void *ctx,
357	const struct irc_ssaddr *addr,
358	struct reslist *request)
359	{
360	char ipbuf[128] = "";
361
362	if (addr->ss.ss_family == AF_INET)
363	{
364	const struct sockaddr_in v4 = (const struct sockaddr_in )addr;
365	const unsigned char cp = (const unsigned char )&v4->sin_addr.s_addr;
366
367	snprintf(ipbuf, sizeof(ipbuf), "%u.%u.%u.%u.in-addr.arpa.",
368	(unsigned int)(cp[3]), (unsigned int)(cp[2]),
369	(unsigned int)(cp[1]), (unsigned int)(cp[0]));
370	}
371	else if (addr->ss.ss_family == AF_INET6)
372	{
373	const struct sockaddr_in6 v6 = (const struct sockaddr_in6 )addr;
374	const unsigned char cp = (const unsigned char )&v6->sin6_addr.s6_addr;
375
376	snprintf(ipbuf, sizeof(ipbuf),
377	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
378	"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa.",
379	(unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
380	(unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
381	(unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
382	(unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
383	(unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
384	(unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
385	(unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
386	(unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
387	(unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
388	(unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
389	(unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
390	(unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
391	(unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
392	(unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
393	(unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
394	(unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
395	}
396
397	if (request == NULL)
398	{
399	request = make_request(callback, ctx);
400	request->type = T_PTR;
401	memcpy(&request->addr, addr, sizeof(struct irc_ssaddr));
402	}
403
404	query_name(ipbuf, C_IN, T_PTR, request);
405	}
406
407	/*
408	* gethost_byname_type - get host address from name
409	*
410	*/
411	void
412	gethost_byname_type(dns_callback_fnc callback, void ctx, const char name, int type)
413	{
414	assert(name);
415	do_query_name(callback, ctx, name, NULL, type);
416	}
417
418	/*
419	* gethost_byname - wrapper for _type - send T_AAAA first if IPV6 supported
420	*/
421	void
422	gethost_byname(dns_callback_fnc callback, void ctx, const char name)
423	{
424	gethost_byname_type(callback, ctx, name, T_AAAA);
425	}
426
427	/*
428	* gethost_byaddr - get host name from address
429	*/
430	void
431	gethost_byaddr(dns_callback_fnc callback, void ctx, const struct irc_ssaddr addr)
432	{
433	do_query_number(callback, ctx, addr, NULL);
434	}
435
436	static void
437	resend_query(struct reslist *request)
438	{
439	switch (request->type)
440	{
441	case T_PTR:
442	do_query_number(NULL, NULL, &request->addr, request);
443	break;
444	case T_A:
445	case T_AAAA:
446	do_query_name(NULL, NULL, request->name, request, request->type);
447	break;
448	default:
449	break;
450	}
451	}
452
453	/*
454	* proc_answer - process name server reply
455	*/
456	static int
457	proc_answer(struct reslist request, HEADER header, char buf, char eob)
458	{
459	char hostbuf[RFC1035_MAX_DOMAIN_LENGTH + 100]; /* working buffer */
460	unsigned char current; / current position in buf */
461	int type; /* answer type */
462	int n; /* temp count */
463	int rd_length;
464	struct sockaddr_in v4; / conversion */
465	struct sockaddr_in6 *v6;
466
467	current = (unsigned char *)buf + sizeof(HEADER);
468
469	for (; header->qdcount > 0; --header->qdcount)
470	{
471	if ((n = irc_dn_skipname(current, (unsigned char *)eob)) < 0)
472	break;
473
474	current += (size_t)n + QFIXEDSZ;
475	}
476
477	/*
478	* Process each answer sent to us blech.
479	*/
480	while (header->ancount > 0 && (char *)current < eob)
481	{
482	header->ancount--;
483
484	n = irc_dn_expand((unsigned char )buf, (unsigned char )eob, current,
485	hostbuf, sizeof(hostbuf));
486
487	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
488	return 0;
489
490	hostbuf[RFC1035_MAX_DOMAIN_LENGTH] = '\0';
491
492	/*
493	* With Address arithmetic you have to be very anal
494	* this code was not working on alpha due to that
495	* (spotted by rodder/jailbird/dianora)
496	*/
497	current += (size_t)n;
498
499	if (!(((char *)current + ANSWER_FIXED_SIZE) < eob))
500	break;
501
502	type = irc_ns_get16(current);
503	current += TYPE_SIZE;
504	current += CLASS_SIZE;
505	current += TTL_SIZE;
506	rd_length = irc_ns_get16(current);
507	current += RDLENGTH_SIZE;
508
509	/*
510	* Wait to set request->type until we verify this structure
511	*/
512	switch (type)
513	{
514	case T_A:
515	if (request->type != T_A)
516	return 0;
517
518	/*
519	* Check for invalid rd_length or too many addresses
520	*/
521	if (rd_length != sizeof(struct in_addr))
522	return 0;
523
524	v4 = (struct sockaddr_in *)&request->addr;
525	request->addr.ss_len = sizeof(struct sockaddr_in);
526	v4->sin_family = AF_INET;
527	memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
528	return 1;
529	break;
530	case T_AAAA:
531	if (request->type != T_AAAA)
532	return 0;
533
534	if (rd_length != sizeof(struct in6_addr))
535	return 0;
536
537	request->addr.ss_len = sizeof(struct sockaddr_in6);
538	v6 = (struct sockaddr_in6 *)&request->addr;
539	v6->sin6_family = AF_INET6;
540	memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
541	return 1;
542	break;
543	case T_PTR:
544	if (request->type != T_PTR)
545	return 0;
546
547	n = irc_dn_expand((unsigned char )buf, (unsigned char )eob,
548	current, hostbuf, sizeof(hostbuf));
549	if (n < 0 /* Broken message / \|\| n == 0 / No more answers left */)
550	return 0;
551
552	request->namelength = strlcpy(request->name, hostbuf, sizeof(request->name));
553	return 1;
554	break;
555	case T_CNAME:
556	current += rd_length;
557	break;
558
559	default:
560	/* XXX I'd rather just throw away the entire bogus thing
561	* but its possible its just a broken nameserver with still
562	* valid answers. But lets do some rudimentary logging for now...
563	*/
564	ilog(LOG_TYPE_IRCD, "irc_res.c bogus type %d", type);
565	break;
566	}
567	}
568
569	return 1;
570	}
571
572	/*
573	* res_readreply - read a dns reply from the nameserver and process it.
574	*/
575	static void
576	res_readreply(fde_t fd, void data)
577	{
578	char buf[sizeof(HEADER) + MAXPACKET];
579	HEADER *header;
580	struct reslist *request = NULL;
581	ssize_t rc = 0;
582	socklen_t len = sizeof(struct irc_ssaddr);
583	struct irc_ssaddr lsin;
584
585	while ((rc = recvfrom(fd->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len)) != -1)
586	{
587	if (rc <= (ssize_t)sizeof(HEADER))
588	continue;
589
590	/*
591	* Check against possibly fake replies
592	*/
593	if (!res_ourserver(&lsin))
594	continue;
595
596	/*
597	* Convert DNS reply reader from Network byte order to CPU byte order.
598	*/
599	header = (HEADER *)buf;
600	header->ancount = ntohs(header->ancount);
601	header->qdcount = ntohs(header->qdcount);
602	header->nscount = ntohs(header->nscount);
603	header->arcount = ntohs(header->arcount);
604
605	/*
606	* Response for an id which we have already received an answer for
607	* just ignore this response.
608	*/
609	if ((request = find_id(header->id)) == NULL)
610	continue;
611
612	if (header->rcode != NO_ERRORS \|\| header->ancount == 0)
613	{
614	/*
615	* If a bad error was returned, stop here and don't
616	* send any more (no retries granted).
617	*/
618	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
619	rem_request(request);
620	continue;
621	}
622
623	/*
624	* If this fails there was an error decoding the received packet.
625	* We only give it one shot. If it fails, just leave the client
626	* unresolved.
627	*/
628	if (!proc_answer(request, header, buf, buf + rc))
629	{
630	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
631	rem_request(request);
632	continue;
633	}
634
635	if (request->type == T_PTR)
636	{
637	if (request->namelength == 0)
638	{
639	/*
640	* Got a PTR response with no name, something bogus is happening
641	* don't bother trying again, the client address doesn't resolve
642	*/
643	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
644	rem_request(request);
645	continue;
646	}
647
648	/*
649	* Lookup the 'authoritative' name that we were given for the ip#.
650	*/
651	if (request->addr.ss.ss_family == AF_INET6)
652	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_AAAA);
653	else
654	gethost_byname_type(request->callback, request->callback_ctx, request->name, T_A);
655	rem_request(request);
656	}
657	else
658	{
659	/*
660	* Got a name and address response, client resolved
661	*/
662	(*request->callback)(request->callback_ctx, &request->addr, request->name, request->namelength);
663	rem_request(request);
664	}
665
666	continue;
667	}
668
669	comm_setselect(fd, COMM_SELECT_READ, res_readreply, NULL, 0);
670	}
671
672	void
673	report_dns_servers(struct Client *source_p)
674	{
675	char ipaddr[HOSTIPLEN + 1] = "";
676
677	for (unsigned int i = 0; i < irc_nscount; ++i)
678	{
679	getnameinfo((struct sockaddr *)&(irc_nsaddr_list[i]),
680	irc_nsaddr_list[i].ss_len, ipaddr,
681	sizeof(ipaddr), NULL, 0, NI_NUMERICHOST);
682	sendto_one_numeric(source_p, &me, RPL_STATSALINE, ipaddr);
683	}
684	}
685
686	/*
687	* timeout_query_list - Remove queries from the list which have been
688	* there too long without being resolved.
689	*/
690	static time_t
691	timeout_query_list(void)
692	{
693	dlink_node ptr = NULL, ptr_next = NULL;
694	struct reslist *request = NULL;
695	time_t next_time = 0;
696	time_t timeout = 0;
697
698	DLINK_FOREACH_SAFE(ptr, ptr_next, request_list.head)
699	{
700	request = ptr->data;
701	timeout = request->sentat + request->timeout;
702
703	if (CurrentTime >= timeout)
704	{
705	if (--request->retries <= 0)
706	{
707	(*request->callback)(request->callback_ctx, NULL, NULL, 0);
708	rem_request(request);
709	continue;
710	}
711	else
712	{
713	request->sentat = CurrentTime;
714	request->timeout += request->timeout;
715	resend_query(request);
716	}
717	}
718
719	if (next_time == 0 \|\| timeout < next_time)
720	next_time = timeout;
721	}
722
723	return (next_time > CurrentTime) ? next_time : (CurrentTime + AR_TTL);
724	}
725
726	/*
727	* timeout_resolver - check request list
728	*/
729	static void
730	timeout_resolver(void *unused)
731	{
732	timeout_query_list();
733	}
734
735	/*
736	* init_resolver - initialize resolver and resolver library
737	*/
738	void
739	init_resolver(void)
740	{
741	static struct event event_timeout_resolver =
742	{
743	.name = "timeout_resolver",
744	.handler = timeout_resolver,
745	.when = 1
746	};
747
748	dns_pool = mp_pool_new(sizeof(struct reslist), MP_CHUNK_SIZE_DNS);
749
750	start_resolver();
751	event_add(&event_timeout_resolver, NULL);
752	}