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---

enum.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2006, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 *
 * Funding provided by nic.at
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief ENUM Support for Asterisk
 *
 * \author Mark Spencer <markster@digium.com>
 *
 * \arg Funding provided by nic.at
 *
 * \par Enum standards
 *
 * - NAPTR records: http://ietf.nri.reston.va.us/rfc/rfc2915.txt
 * - DNS SRV records: http://www.ietf.org/rfc/rfc2782.txt
 * - ENUM http://www.ietf.org/rfc/rfc3761.txt
 * - ENUM for H.323: http://www.ietf.org/rfc/rfc3762.txt
 * - ENUM SIP: http://www.ietf.org/rfc/rfc3764.txt
 * - IANA ENUM Services: http://www.iana.org/assignments/enum-services
 *
 * \par Possible improvement
 * \todo Implement a caching mechanism for multile enum lookups
 * - See http://bugs.digium.com/view.php?id=6739
 */

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 51499 $")

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#if __APPLE_CC__ >= 1495
#include <arpa/nameser_compat.h>
#endif
#include <resolv.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <regex.h>
#include <unistd.h>
#include <errno.h>

#include "asterisk/logger.h"
#include "asterisk/options.h"
#include "asterisk/enum.h"
#include "asterisk/dns.h"
#include "asterisk/channel.h"
#include "asterisk/config.h"
#include "asterisk/utils.h"

#ifdef __APPLE__
#undef T_NAPTR
#define T_NAPTR 35
#endif

#ifdef __APPLE__
#undef T_TXT
#define T_TXT 16
#endif

#define TOPLEV "e164.arpa."   /*!< The IETF Enum standard root, managed by the ITU */

/* Linked list from config file */
static struct enum_search {
   char toplev[512];
   struct enum_search *next;
} *toplevs;

static int enumver;

AST_MUTEX_DEFINE_STATIC(enumlock);

struct naptr {
   unsigned short order;
   unsigned short pref;
} __attribute__ ((__packed__));

/*! \brief Parse NAPTR record information elements */
static unsigned int parse_ie(char *data, unsigned int maxdatalen, unsigned char *src, unsigned int srclen)
{
   unsigned int len, olen;

   len = olen = (unsigned int) src[0];
   src++;
   srclen--;

   if (len > srclen) {
      ast_log(LOG_WARNING, "ENUM parsing failed: Wanted %d characters, got %d\n", len, srclen);
      return -1;
   }

   if (len > maxdatalen)
      len = maxdatalen;
   memcpy(data, src, len);

   return olen + 1;
}

/*! \brief Parse DNS NAPTR record used in ENUM ---*/
static int parse_naptr(char *dst, int dstsize, char *tech, int techsize, unsigned char *answer, int len, char *naptrinput)
{
   char tech_return[80];
   unsigned char *oanswer = answer;
   char flags[512] = "";
   char services[512] = "";
   char *p;
   char regexp[512] = "";
   char repl[512] = "";
   char temp[512] = "";
   char delim;
   char *delim2;
   char *pattern, *subst, *d;
   int res;
   int regexp_len, size, backref;
   int d_len = sizeof(temp) - 1;
   regex_t preg;
   regmatch_t pmatch[9];

   tech_return[0] = '\0';

   dst[0] = '\0';

   if (len < sizeof(struct naptr)) {
      ast_log(LOG_WARNING, "NAPTR record length too short\n");
      return -1;
   }
   answer += sizeof(struct naptr);
   len -= sizeof(struct naptr);
   if ((res = parse_ie(flags, sizeof(flags) - 1, answer, len)) < 0) {
      ast_log(LOG_WARNING, "Failed to get flags from NAPTR record\n");
      return -1;
   } else {
      answer += res;
      len -= res;
   }
   if ((res = parse_ie(services, sizeof(services) - 1, answer, len)) < 0) {
      ast_log(LOG_WARNING, "Failed to get services from NAPTR record\n");
      return -1;
   } else {
      answer += res;
      len -= res;
   }
   if ((res = parse_ie(regexp, sizeof(regexp) - 1, answer, len)) < 0) {
      ast_log(LOG_WARNING, "Failed to get regexp from NAPTR record\n");
      return -1;
   } else {
      answer += res;
      len -= res;
   }

   if ((res = dn_expand(oanswer, answer + len, answer, repl, sizeof(repl) - 1)) < 0) {
      ast_log(LOG_WARNING, "Failed to expand hostname\n");
      return -1;
   }

   if (option_debug > 2)   /* Advanced NAPTR debugging */
      ast_log(LOG_DEBUG, "NAPTR input='%s', flags='%s', services='%s', regexp='%s', repl='%s'\n",
         naptrinput, flags, services, regexp, repl);

   if (tolower(flags[0]) != 'u') {
      ast_log(LOG_WARNING, "NAPTR Flag must be 'U' or 'u'.\n");
      return -1;
   }

   p = strstr(services, "e2u+");
   if (p == NULL)
      p = strstr(services, "E2U+");
   if (p){
      p = p + 4;
      if (strchr(p, ':')){
         p = strchr(p, ':') + 1;
      }
      ast_copy_string(tech_return, p, sizeof(tech_return));
   } else {

      p = strstr(services, "+e2u");
      if (p == NULL)
         p = strstr(services, "+E2U");
      if (p) {
         *p = 0;
         p = strchr(services, ':');
         if (p)
            *p = 0;
         ast_copy_string(tech_return, services, sizeof(tech_return));
      }
   }

   /* DEDBUGGING STUB
   ast_copy_string(regexp, "!^\\+43(.*)$!\\1@bla.fasel!", sizeof(regexp) - 1);
   */

   regexp_len = strlen(regexp);
   if (regexp_len < 7) {
      ast_log(LOG_WARNING, "Regex too short to be meaningful.\n");
      return -1;
   }


   delim = regexp[0];
   delim2 = strchr(regexp + 1, delim);
   if ((delim2 == NULL) || (regexp[regexp_len-1] != delim)) {
      ast_log(LOG_WARNING, "Regex delimiter error (on \"%s\").\n",regexp);
      return -1;
   }

   pattern = regexp + 1;
   *delim2 = 0;
   subst   = delim2 + 1;
   regexp[regexp_len-1] = 0;

/*
 * now do the regex wizardry.
 */

   if (regcomp(&preg, pattern, REG_EXTENDED | REG_NEWLINE)) {
      ast_log(LOG_WARNING, "NAPTR Regex compilation error (regex = \"%s\").\n",regexp);
      return -1;
   }

   if (preg.re_nsub > 9) {
      ast_log(LOG_WARNING, "NAPTR Regex compilation error: too many subs.\n");
      regfree(&preg);
      return -1;
   }

   if (regexec(&preg, naptrinput, 9, pmatch, 0)) {
      ast_log(LOG_WARNING, "NAPTR Regex match failed.\n");
      regfree(&preg);
      return -1;
   }
   regfree(&preg);

   d = temp;
   d_len--;
   while (*subst && (d_len > 0)) {
      if ((subst[0] == '\\') && isdigit(subst[1]) && (pmatch[subst[1]-'0'].rm_so != -1)) {
         backref = subst[1]-'0';
         size = pmatch[backref].rm_eo - pmatch[backref].rm_so;
         if (size > d_len) {
            ast_log(LOG_WARNING, "Not enough space during NAPTR regex substitution.\n");
            return -1;
            }
         memcpy(d, naptrinput + pmatch[backref].rm_so, size);
         d += size;
         d_len -= size;
         subst += 2;
      } else if (isprint(*subst)) {
         *d++ = *subst++;
         d_len--;
      } else {
         ast_log(LOG_WARNING, "Error during regex substitution.\n");
         return -1;
      }
   }
   *d = 0;
   ast_copy_string(dst, temp, dstsize);
   dst[dstsize - 1] = '\0';

   if (*tech != '\0'){ /* check if it is requested NAPTR */
      if (!strncasecmp(tech, "ALL", techsize)){
         return 1; /* return or count any RR */
      }
      if (!strncasecmp(tech_return, tech, sizeof(tech_return)<techsize?sizeof(tech_return):techsize)){
         ast_copy_string(tech, tech_return, techsize);
         return 1; /* we got out RR */
      } else { /* go to the next RR in the DNS answer */
         return 0;
      }
   }

   /* tech was not specified, return first parsed RR */
   ast_copy_string(tech, tech_return, techsize);

   return 1;
}

/* do not return requested value, just count RRs and return thei number in dst */
#define ENUMLOOKUP_OPTIONS_COUNT       1

struct enum_naptr_rr {
   struct naptr naptr; /* order and preference of RR */
   char *result; /* result of naptr parsing,e.g.: tel:+5553 */
   char *tech; /* Technology (from URL scheme) */
   int sort_pos; /* sort position */
};

struct enum_context {
   char *dst;  /* Destination part of URL from ENUM */
   int dstlen; /* Length */
   char *tech; /* Technology (from URL scheme) */
   int techlen;   /* Length */
   char *txt;  /* TXT record in TXT lookup */
   int txtlen; /* Length */
   char *naptrinput; /* The number to lookup */
   int position; /* used as counter for RRs or specifies position of required RR */
   int options; /* options , see ENUMLOOKUP_OPTIONS_* defined above */
   struct enum_naptr_rr *naptr_rrs; /* array of parsed NAPTR RRs */
   int naptr_rrs_count; /* Size of array naptr_rrs */
};

/*! \brief Callback for TXT record lookup */
static int txt_callback(void *context, unsigned char *answer, int len, unsigned char *fullanswer)
{
   struct enum_context *c = (struct enum_context *)context;

   if (answer == NULL) {
      c->txt = NULL;
      c->txtlen = 0;
      return 0;
   }

   /* skip over first byte, as for some reason it's a vertical tab character */
   answer += 1;
   len -= 1;

   /* answer is not null-terminated, but should be */
   /* this is safe to do, as answer has extra bytes on the end we can
    * safely overwrite with a null */
   answer[len] = '\0';
   /* now increment len so that len includes the null, so that we can
    * compare apples to apples */
   len +=1;

   /* finally, copy the answer into c->txt */
   ast_copy_string(c->txt, (const char *) answer, len < c->txtlen ? len : (c->txtlen));

   /* just to be safe, let's make sure c->txt is null terminated */
   c->txt[(c->txtlen)-1] = '\0';

   return 1;
}

/*! \brief Callback from ENUM lookup function */
static int enum_callback(void *context, unsigned char *answer, int len, unsigned char *fullanswer)
{
   struct enum_context *c = context;
   void *p = NULL;
   int res;

   res = parse_naptr(c->dst, c->dstlen, c->tech, c->techlen, answer, len, c->naptrinput);

   if (res < 0) {
      ast_log(LOG_WARNING, "Failed to parse naptr :(\n");
      return -1;
   } else if (res > 0 && !ast_strlen_zero(c->dst)){ /* ok, we got needed NAPTR */
      if (c->options & ENUMLOOKUP_OPTIONS_COUNT){ /* counting RRs */
         c->position++;
         snprintf(c->dst, c->dstlen, "%d", c->position);
      } else  {
         if ((p = ast_realloc(c->naptr_rrs, sizeof(*c->naptr_rrs) * (c->naptr_rrs_count + 1)))) {
            c->naptr_rrs = p;
            memcpy(&c->naptr_rrs[c->naptr_rrs_count].naptr, answer, sizeof(c->naptr_rrs->naptr));
            c->naptr_rrs[c->naptr_rrs_count].result = strdup(c->dst);
            c->naptr_rrs[c->naptr_rrs_count].tech = strdup(c->tech);
            c->naptr_rrs[c->naptr_rrs_count].sort_pos = c->naptr_rrs_count;
            c->naptr_rrs_count++;
         }
         c->dst[0] = 0;
      }
      return 0;
   }

   if (c->options & ENUMLOOKUP_OPTIONS_COUNT)   { /* counting RRs */
      snprintf(c->dst, c->dstlen, "%d", c->position);
   }

   return 0;
}

/*! \brief ENUM lookup */
int ast_get_enum(struct ast_channel *chan, const char *number, char *dst, int dstlen, char *tech, int techlen, char* suffix, char* options, unsigned int record)
{
   struct enum_context context;
   char tmp[259 + 512];
   char naptrinput[512];
   int pos = strlen(number) - 1;
   int newpos = 0;
   int ret = -1;
   struct enum_search *s = NULL;
   int version = -1;
   /* for ISN rewrite */
   char *p1 = NULL;
   char *p2 = NULL;
   int k = 0;
   int i = 0;
   int z = 0;

   ast_copy_string(naptrinput, number[0] == 'n' ? number+1 : number, sizeof(naptrinput));

   context.naptrinput = naptrinput; /* The number */
   context.dst = dst;         /* Return string */
   context.dstlen = dstlen;
   context.tech = tech;
   context.techlen = techlen;
   context.options = 0;
   context.position = record;
   context.naptr_rrs = NULL;
   context.naptr_rrs_count = 0;

   if (options != NULL) {
      if (*options == 'c') {
         context.options = ENUMLOOKUP_OPTIONS_COUNT;
         context.position = 0;
      }
   }

   ast_log(LOG_DEBUG, "ast_get_enum(): n='%s', tech='%s', suffix='%s', options='%d', record='%d'\n",
         number, tech, suffix, context.options, context.position);

   if (pos > 128)
      pos = 128;

   /* ISN rewrite */
   p1 = strchr(number, '*');

   if (number[0] == 'n') { /* do not perform ISN rewrite ('n' is testing flag) */
      p1 = NULL;
      k = 1; /* strip 'n' from number */
   }

   if (p1 != NULL) {
      p2 = p1+1;
      while (p1 > number){
         p1--;
         tmp[newpos++] = *p1;
         tmp[newpos++] = '.';
      }
      if (*p2) {
         while (*p2 && newpos < 128){
            tmp[newpos++] = *p2;
            p2++;
         }
         tmp[newpos++] = '.';
      }

   } else {
      while (pos >= k) {
         if (isdigit(number[pos])) {
            tmp[newpos++] = number[pos];
            tmp[newpos++] = '.';
         }
         pos--;
      }
   }

   if (chan && ast_autoservice_start(chan) < 0)
      return -1;

   if(suffix) {
      ast_copy_string(tmp + newpos, suffix, sizeof(tmp) - newpos);
      ret = ast_search_dns(&context, tmp, C_IN, T_NAPTR, enum_callback);
      ast_log(LOG_DEBUG, "ast_get_enum: ast_search_dns(%s) returned %d\n", tmp, ret);
   } else {
      ret = -1;      /* this is actually dead code since the demise of app_enum.c */
      for (;;) {
         ast_mutex_lock(&enumlock);
         if (version != enumver) {
            /* Ooh, a reload... */
            s = toplevs;
            version = enumver;
         } else {
            s = s->next;
         }
         ast_mutex_unlock(&enumlock);

         if (!s)
            break;
   
         ast_copy_string(tmp + newpos, s->toplev, sizeof(tmp) - newpos);
         ret = ast_search_dns(&context, tmp, C_IN, T_NAPTR, enum_callback);
         ast_log(LOG_DEBUG, "ast_get_enum: ast_search_dns(%s) returned %d\n", tmp, ret);
         if (ret > 0)
            break;
      }
   }

   if (ret < 0) {
      if (option_debug)
         ast_log(LOG_DEBUG, "No such number found: %s (%s)\n", tmp, strerror(errno));
      strcpy(dst, "0");
      ret = 0;
   }

   if (context.naptr_rrs_count >= context.position && ! (context.options & ENUMLOOKUP_OPTIONS_COUNT)) {
      /* sort array by NAPTR order/preference */
      for (k = 0; k < context.naptr_rrs_count; k++) {
         for (i = 0; i < context.naptr_rrs_count; i++) {
            /* use order first and then preference to compare */
            if ((ntohs(context.naptr_rrs[k].naptr.order) < ntohs(context.naptr_rrs[i].naptr.order)
                  && context.naptr_rrs[k].sort_pos > context.naptr_rrs[i].sort_pos)
               || (ntohs(context.naptr_rrs[k].naptr.order) > ntohs(context.naptr_rrs[i].naptr.order)
                  && context.naptr_rrs[k].sort_pos < context.naptr_rrs[i].sort_pos)){
               z = context.naptr_rrs[k].sort_pos;
               context.naptr_rrs[k].sort_pos = context.naptr_rrs[i].sort_pos;
               context.naptr_rrs[i].sort_pos = z;
               continue;
            }
            if (ntohs(context.naptr_rrs[k].naptr.order) == ntohs(context.naptr_rrs[i].naptr.order)) {
               if ((ntohs(context.naptr_rrs[k].naptr.pref) < ntohs(context.naptr_rrs[i].naptr.pref)
                     && context.naptr_rrs[k].sort_pos > context.naptr_rrs[i].sort_pos)
                  || (ntohs(context.naptr_rrs[k].naptr.pref) > ntohs(context.naptr_rrs[i].naptr.pref)
                     && context.naptr_rrs[k].sort_pos < context.naptr_rrs[i].sort_pos)){
                  z = context.naptr_rrs[k].sort_pos;
                  context.naptr_rrs[k].sort_pos = context.naptr_rrs[i].sort_pos;
                  context.naptr_rrs[i].sort_pos = z;
               }
            }
         }
      }
      for (k = 0; k < context.naptr_rrs_count; k++) {
         if (context.naptr_rrs[k].sort_pos == context.position-1) {
            ast_copy_string(context.dst, context.naptr_rrs[k].result, dstlen);
            ast_copy_string(context.tech, context.naptr_rrs[k].tech, techlen);
            break;
         }
      }
   } else if (!(context.options & ENUMLOOKUP_OPTIONS_COUNT)) {
      context.dst[0] = 0;
   }
   if (chan)
      ret |= ast_autoservice_stop(chan);

   for (k = 0; k < context.naptr_rrs_count; k++) {
      free(context.naptr_rrs[k].result);
      free(context.naptr_rrs[k].tech);
   }

   free(context.naptr_rrs);

   return ret;
}

/*! \brief Get TXT record from DNS.
   Really has nothing to do with enum, but anyway...
 */
int ast_get_txt(struct ast_channel *chan, const char *number, char *dst, int dstlen, char *tech, int techlen, char *txt, int txtlen)
{
   struct enum_context context;
   char tmp[259 + 512];
   char naptrinput[512] = "+";
   int pos = strlen(number) - 1;
   int newpos = 0;
   int ret = -1;
   struct enum_search *s = NULL;
   int version = -1;

   strncat(naptrinput, number, sizeof(naptrinput) - 2);

   context.naptrinput = naptrinput;
   context.dst = dst;
   context.dstlen = dstlen;
   context.tech = tech;
   context.techlen = techlen;
   context.txt = txt;
   context.txtlen = txtlen;

   if (pos > 128)
      pos = 128;
   while (pos >= 0) {
      tmp[newpos++] = number[pos--];
      tmp[newpos++] = '.';
   }

   if (chan && ast_autoservice_start(chan) < 0)
      return -1;

   for (;;) {
      ast_mutex_lock(&enumlock);
      if (version != enumver) {
         /* Ooh, a reload... */
         s = toplevs;
         version = enumver;
      } else {
         s = s->next;
      }
      if (s) {
         ast_copy_string(tmp + newpos, s->toplev, sizeof(tmp) - newpos);
      }
      ast_mutex_unlock(&enumlock);
      if (!s)
         break;

      ret = ast_search_dns(&context, tmp, C_IN, T_TXT, txt_callback);
      if (ret > 0)
         break;
   }
   if (ret < 0) {
      if (option_debug > 1)
         ast_log(LOG_DEBUG, "No such number found in ENUM: %s (%s)\n", tmp, strerror(errno));
      ret = 0;
   }
   if (chan)
      ret |= ast_autoservice_stop(chan);
   return ret;
}

/*! \brief Add enum tree to linked list */
static struct enum_search *enum_newtoplev(char *s)
{
   struct enum_search *tmp;

   if ((tmp = ast_calloc(1, sizeof(*tmp)))) {      
      ast_copy_string(tmp->toplev, s, sizeof(tmp->toplev));
   }
   return tmp;
}

/*! \brief Initialize the ENUM support subsystem */
int ast_enum_init(void)
{
   struct ast_config *cfg;
   struct enum_search *s, *sl;
   struct ast_variable *v;

   /* Destroy existing list */
   ast_mutex_lock(&enumlock);
   s = toplevs;
   while (s) {
      sl = s;
      s = s->next;
      free(sl);
   }
   toplevs = NULL;
   cfg = ast_config_load("enum.conf");
   if (cfg) {
      sl = NULL;
      v = ast_variable_browse(cfg, "general");
      while (v) {
         if (!strcasecmp(v->name, "search")) {
            s = enum_newtoplev(v->value);
            if (s) {
               if (sl)
                  sl->next = s;
               else
                  toplevs = s;
               sl = s;
            }
         }
         v = v->next;
      }
      ast_config_destroy(cfg);
   } else {
      toplevs = enum_newtoplev(TOPLEV);
   }
   enumver++;
   ast_mutex_unlock(&enumlock);
   return 0;
}

int ast_enum_reload(void)
{
   return ast_enum_init();
}

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