sip_utils.c

siproxd is a proxy/masquerading for the SIP protocal.

/* -*- Mode: C; c-basic-offset: 3 -*-
    Copyright (C) 2002  Thomas Ries <[e-mail]>

    This file is part of Siproxd.
    
    Siproxd 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.
    
    Siproxd 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 Siproxd; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
*/
#include "config.h"

#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <time.h>
#include <signal.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <net/if.h>
#include <sys/ioctl.h>

#include <sys/types.h>
#include <pwd.h>

#include <osipparser2/osip_parser.h>
#include <osipparser2/osip_port.h>
#include <osipparser2/osip_md5.h>

#include "siproxd.h"
#include "digcalc.h"
#include "rewrite_rules.h"
#include "log.h"

static char const ident[]="$Id: " __FILE__ ": " PACKAGE "-" VERSION "-"
			  BUILDSTR " $";

/* configuration storage */
extern struct siproxd_config configuration;

extern int h_errno;
extern int sip_socket;				/* sending SIP datagrams */

extern struct urlmap_s urlmap[];		/* URL mapping table     */


/*
 * create a reply template from an given SIP request
 *
 * RETURNS a pointer to osip_message_t
 */
osip_message_t *msg_make_template_reply (osip_message_t * request, int code) {
   osip_message_t *response;
   int pos;

   osip_message_init (&response);
   response->message=NULL;
   osip_message_set_version (response, osip_strdup ("SIP/2.0"));
   osip_message_set_status_code (response, code);
   osip_message_set_reason_phrase (response, 
                                   osip_strdup(osip_message_get_reason (code)));

   if (request->to==NULL) {
      ERROR("msg_make_template_reply: empty To in request header");
   }

   if (request->from==NULL) {
      ERROR("msg_make_template_reply: empty From in request header");
   }

   osip_to_clone (request->to, &response->to);
   osip_from_clone (request->from, &response->from);


   /* via headers */
   pos = 0;
   while (!osip_list_eol (request->vias, pos)) {
      char *tmp;
      osip_via_t *via;
      via = (osip_via_t *) osip_list_get (request->vias, pos);
      osip_via_to_str (via, &tmp);

      osip_message_set_via (response, tmp);
      osip_free (tmp);
      pos++;
   }

   osip_call_id_clone(request->call_id,&response->call_id);
   osip_cseq_clone(request->cseq,&response->cseq);

   return response;
}


/*
 * check for a via loop.
 * It checks for the presense of a via entry that holds one of
 * my IP addresses and is *not* the topmost via.
 *
 * RETURNS
 *	STS_TRUE if loop detected
 *	STS_FALSE if no loop
 */
int check_vialoop (osip_message_t *my_msg) {
/*
!!! actually this is a problematic one.
1) for requests, I must search the whole VIA list
   (topmost via is the previos station in the path)

2) for responses I must skip the topmost via, as this is mine
   (and will be removed later on)

3) What happens if we have 'clashes'  with private addresses??
   From that point of view, siproxd *should* not try to
   check against it's local IF addresses if they are private.
   this then of course again can lead to a endless loop...
   -> Use a fixed unique part of branch parameter to identify that it
   is MY via
   
   can we use something like a Tag in via headers?? (a veriy likely
   to-be-unique ID)

*/
   int sts;
   int pos;
   int found_own_via;

   found_own_via=0;
   pos = 1;	/* for detecting a loop, don't check the first entry 
   		   as this is my own VIA! */
   while (!osip_list_eol (my_msg->vias, pos)) {
      osip_via_t *via;
      via = (osip_via_t *) osip_list_get (my_msg->vias, pos);
      sts = is_via_local (via);
      if (sts == STS_TRUE) found_own_via+=1;
      pos++;
   }

   /*
    * what happens if a message is coming back to me legally?
    *  UA1 -->--\       /-->--\
    *            siproxd       Registrar
    *  UA2 --<--/       \--<--/
    *
    * This may also lead to a VIA loop - so I probably must take the branch
    * parameter into count (or a unique part of it) OR just allow at least 2
    * vias of my own.
    */
   return (found_own_via>2)? STS_TRUE : STS_FALSE;
}


/*
 * check if a given osip_via_t is local. I.e. its address is owned
 * by my inbound or outbound interface
 *
 * RETURNS
 *	STS_TRUE if the given VIA is one of my interfaces
 *	STS_FALSE otherwise
 */
int is_via_local (osip_via_t *via) {
   int sts, found;
   struct in_addr addr_via, addr_myself;
   char *my_interfaces[]=
        { configuration.inbound_if,  configuration.outbound_if,  (char*)-1 };
   int port;
   int i;
   char *ptr;

   if (via==NULL) {
      ERROR("called is_via_local with NULL via");
      return STS_FALSE;
   }

   DEBUGC(DBCLASS_BABBLE,"via name %s",via->host);
   if (utils_inet_aton(via->host,&addr_via) == 0) {
      /* need name resolution */
      sts=get_ip_by_host(via->host, &addr_via);
      if (sts == STS_FAILURE) {
         DEBUGC(DBCLASS_DNS, "is_via_local: cannot resolve VIA [%s]",
                via->host);
         return STS_FAILURE;
      }
   }   

   found=0;
   for (i=0; ; i++) {
      /*
       * try to search by interface name first
       */
      ptr=my_interfaces[i];
      if (ptr==(char*)-1) break; /* end of list mark */

      if (ptr) {
         DEBUGC(DBCLASS_BABBLE,"resolving IP of interface %s",ptr);
         sts = get_ip_by_ifname(ptr, &addr_myself);
      }

      /* check the extracted VIA against my own host addresses */
      if (via->port) port=atoi(via->port);
      else port=SIP_PORT;

      if ( (memcmp(&addr_myself, &addr_via, sizeof(addr_myself))==0) &&
           (port == configuration.sip_listen_port) ) {
         DEBUG("got address match [%s]", utils_inet_ntoa(addr_via));
         found=1;
	 break;
      }
   }

   return (found)? STS_TRUE : STS_FALSE;
}


/*
 * compares two URLs
 * (by now, only scheme, hostname and username are compared)
 *
 * RETURNS
 *	STS_SUCCESS if equal
 *	STS_FAILURE if non equal or error
 */
int compare_url(osip_uri_t *url1, osip_uri_t *url2) {
   int sts1, sts2;
   struct in_addr addr1, addr2;

   /* sanity checks */
   if ((url1 == NULL) || (url2 == NULL)) {
      ERROR("compare_url: NULL ptr: url1=0x%p, url2=0x%p",url1, url2);
      return STS_FAILURE;
   }

   /* sanity checks: host part is a MUST */
   if ((url1->host == NULL) || (url2->host == NULL)) {
      ERROR("compare_url: NULL ptr: url1->host=0x%p, url2->host=0x%p",
            url1->host, url2->host);
      return STS_FAILURE;
   }

   DEBUGC(DBCLASS_PROXY, "comparing urls: %s:%s@%s -> %s:%s@%s",
         (url1->scheme)   ? url1->scheme :   "(null)",
         (url1->username) ? url1->username : "(null)",
         (url1->host)     ? url1->host :     "(null)",
         (url2->scheme)   ? url2->scheme :   "(null)",
         (url2->username) ? url2->username : "(null)",
         (url2->host)     ? url2->host :     "(null)");

   /* compare SCHEME (if present) case INsensitive */
   if (url1->scheme && url2->scheme) {
      if (strcasecmp(url1->scheme, url2->scheme) != 0) {
         DEBUGC(DBCLASS_PROXY, "compare_url: scheme mismatch");
         return STS_FAILURE;
      }
   } else {
      WARN("compare_url: NULL scheme - ignoring");
   }

   /* compare username (if present) case sensitive */
   if (url1->username && url2->username) {
      if (strcmp(url1->username, url2->username) != 0) {
         DEBUGC(DBCLASS_PROXY, "compare_url: username mismatch");
         return STS_FAILURE;
      }
   } else {
      WARN("compare_url: NULL username - ignoring");
   }


   /*
    * now, try to resolve the host. If resolveable, compare
    * IP addresses - if not resolveable, compare the host names
    * itselfes
    */

   /* get the IP addresses from the (possible) hostnames */
   sts1=get_ip_by_host(url1->host, &addr1);
   if (sts1 == STS_FAILURE) {
      DEBUGC(DBCLASS_PROXY, "compare_url: cannot resolve host [%s]",
             url1->host);
   }

   sts2=get_ip_by_host(url2->host, &addr2);
   if (sts2 == STS_FAILURE) {
      DEBUGC(DBCLASS_PROXY, "compare_url: cannot resolve host [%s]",
             url2->host);
   }

   if ((sts1 == STS_SUCCESS) && (sts2 == STS_SUCCESS)) {
      /* compare IP addresses */
      if (memcmp(&addr1, &addr2, sizeof(addr1))!=0) {
         DEBUGC(DBCLASS_PROXY, "compare_url: IP mismatch");
         return STS_FAILURE;
      }
   } else {
      /* compare hostname strings case INsensitive */
      if (strcasecmp(url1->host, url2->host) != 0) {
         DEBUGC(DBCLASS_PROXY, "compare_url: host name mismatch");
         return STS_FAILURE;
      }
   }

   /* the two URLs did pass all tests successfully - MATCH */
   return STS_SUCCESS;
}


/*
 * compares two Call IDs
 * (by now, only hostname and username are compared)
 *
 * RETURNS
 *	STS_SUCCESS if equal
 *	STS_FAILURE if non equal or error
 */
int compare_callid(osip_call_id_t *cid1, osip_call_id_t *cid2) {

   if ((cid1==0) || (cid2==0)) {
      ERROR("compare_callid: NULL ptr: cid1=0x%p, cid2=0x%p",cid1, cid2);
      return STS_FAILURE;
   }

   /*
    * Check number part: if present must be equal, 
    * if not present, must be not present in both cids
    */
   if (cid1->number && cid2->number) {
      /* have both numbers */
      if (strcmp(cid1->number, cid2->number) != 0) goto mismatch;
   } else {
      /* at least one number missing, make sure that both are empty */
      if ( (cid1->number && (cid1->number[0]!='\0')) ||
           (cid2->number && (cid2->number[0]!='\0'))) {
         goto mismatch;
      }
   }

   /*
    * Check host part: if present must be equal, 
    * if not present, must be not present in both cids
    */
   if (cid1->host && cid2->host) {
      /* have both hosts */
      if (strcmp(cid1->host, cid2->host) != 0) goto mismatch;
   } else {
      /* at least one host missing, make sure that both are empty */
      if ( (cid1->host && (cid1->host[0]!='\0')) ||
           (cid2->host && (cid2->host[0]!='\0'))) {
         goto mismatch;
      }
   }

   DEBUGC(DBCLASS_BABBLE, "comparing callid - matched: "
          "%s@%s <-> %s@%s",
          cid1->number, cid1->host, cid2->number, cid2->host);
   return STS_SUCCESS;

mismatch:
   DEBUGC(DBCLASS_BABBLE, "comparing callid - mismatch: "
          "%s@%s <-> %s@%s",
          cid1->number, cid1->host, cid2->number, cid2->host);
   return STS_FAILURE;
}


/*
 * check if a given request is addressed to local. I.e. it is addressed
 * to the porxy itself (IP of my inbound or outbound interface, same port)
 *
 * RETURNS
 *	STS_TRUE if the request is addressed local
 *	STS_FALSE otherwise
 */
int is_sipuri_local (osip_message_t *sip) {
   int sts, found;
   struct in_addr addr_uri, addr_myself;
   char *my_interfaces[]=
        { configuration.inbound_if,  configuration.outbound_if,  (char*)-1 };
   int port;
   int i;
   char *ptr;

   if (sip==NULL) {
      ERROR("called is_sipuri_local with NULL sip");
      return STS_FALSE;
   }

   if (!sip || !sip->req_uri) {
      ERROR("is_sipuri_local: no request URI present");
      return STS_FALSE;
   }

   DEBUGC(DBCLASS_DNS,"check for local SIP URI %s:%s",
          sip->req_uri->host? sip->req_uri->host : "*NULL*",
          sip->req_uri->port? sip->req_uri->port : "*NULL*");

   if (utils_inet_aton(sip->req_uri->host, &addr_uri) == 0) {
      /* need name resolution */
      get_ip_by_host(sip->req_uri->host, &addr_uri);
   }   

   found=0;
   for (i=0; ; i++) {
      /*
       * try to search by interface name first
       */
      ptr=my_interfaces[i];
      if (ptr==(char*)-1) break; /* end of list mark */

      if (ptr) {
         DEBUGC(DBCLASS_BABBLE,"resolving IP of interface %s",ptr);
         sts = get_ip_by_ifname(ptr, &addr_myself);
      }

      /* check the extracted HOST against my own host addresses */
      if (sip->req_uri->port) {
         port=atoi(sip->req_uri->port);
      } else {
         port=SIP_PORT;
      }