tdlookup.c

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#include <unistd.h>
#include "uint_t.h"
#include "open.h"
#include "tai.h"
#include "cdbread.h"
#include "byte.h"
#include "case.h"
#include "dns.h"
#include "seek.h"
#include "response.h"
#include "ip.h"
#include "clientloc.h"
 
static int want(const char *owner,const char type[2])
{
  unsigned int pos;
  static char *d;
  char x[10];
  uint16 datalen;
 
  pos = dns_packet_skipname(response,response_len,12); if (!pos) return 0;
  pos += 4;
 
  while (pos < response_len) {
    pos = dns_packet_getname(response,response_len,pos,&d); if (!pos) return 0;
    pos = dns_packet_copy(response,response_len,pos,x,10); if (!pos) return 0;
    if (dns_domain_equal(d,owner))
      if (byte_equal(type,2,x)) return 0;
    uint16_unpack_big(x + 8,&datalen);
    pos += datalen;
  }
  return 1;
}
 
static char *d1;
 
static char clientloc[2];
static struct tai now;
static struct cdb c;
 
static char data[32767];
static uint32 dlen;
static unsigned int dpos;
static char type[2];
static uint32 ttl;
 
static int find(char *d,int flagwild)
{
  int r;
  char ch;
  struct tai cutoff;
  char ttd[8];
  char ttlstr[4];
  char recordloc[2];
  double newttl;
 
  for (;;) {
    r = cdb_findnext(&c,d,dns_domain_length(d));
    if (r <= 0) return r;
    dlen = cdb_datalen(&c);
    if (dlen > sizeof(data)) return DNS_ERR;
    if (cdb_read(&c,data,dlen,cdb_datapos(&c)) == -1) return DNS_INT;
    dpos = dns_packet_copy(data,dlen,0,type,2); if (!dpos) return DNS_ERR;
    dpos = dns_packet_copy(data,dlen,dpos,&ch,1); if (!dpos) return DNS_ERR;
    if ((ch == '=' + 1) || (ch == '*' + 1)) {  // XXX: locator '='/'>' (in/out); wildcard '+'
      --ch;
      dpos = dns_packet_copy(data,dlen,dpos,recordloc,2); if (!dpos) return DNS_ERR;
      if (byte_diff(recordloc,2,clientloc)) continue;
    }
    if (flagwild != (ch == '*')) continue;
    dpos = dns_packet_copy(data,dlen,dpos,ttlstr,4); if (!dpos) return DNS_ERR;
    uint32_unpack_big(ttlstr,&ttl);
    dpos = dns_packet_copy(data,dlen,dpos,ttd,8); if (!dpos) return DNS_ERR;
    if (byte_diff(ttd,8,"\0\0\0\0\0\0\0\0")) {
      tai_unpack(ttd,&cutoff);
      if (ttl == 0) {
        if (tai_less(&cutoff,&now)) continue;
        tai_sub(&cutoff,&cutoff,&now);
        newttl = tai_approx(&cutoff);
        if (newttl <= 2.0) newttl = 2.0;
        if (newttl >= 3600.0) newttl = 3600.0;
        ttl = newttl;
      }
      else
        if (!tai_less(&cutoff,&now)) continue;
    }
    return 1;
  }
}
 
static int dobytes(unsigned int len)
{
  char buf[20];
  if (len > 20) return 0;
  dpos = dns_packet_copy(data,dlen,dpos,buf,len);
  if (!dpos) return 0;
  return response_addbytes(buf,len);
}
 
static int doname(void)
{
  dpos = dns_packet_getname(data,dlen,dpos,&d1);
  if (!dpos) return 0;
  return response_addname(d1);
}
 
static int doit(char *q,char qtype[2])
{
  unsigned int bpos;
  unsigned int anpos;
  unsigned int aupos;
  unsigned int arpos;
  char *control;
  char *wild;
  int flaggavesoa;
  int flagfound;
  int r;
  int flagns;
  int flagauthoritative;
  char x[20];
  char dn[FQDN_LEN + 1];
  uint16 u16;
  char addr4[MAX_ANSWERS][4];
  char addr6[MAX_ANSWERS][16];
  int addr4num, addr6num;
  uint32 addr4ttl; 
  uint32 addr6ttl;
  int i;
 
  anpos = response_len;
 
  control = q;
  for (;;) {
    flagns = 0;
    flagauthoritative = 0;
    cdb_findstart(&c);
    while ((r = find(control,0))) {
      if (r == -1) return 0;
      if (byte_equal(type,2,DNS_T_SOA)) flagauthoritative = 1;
      if (byte_equal(type,2,DNS_T_NS)) flagns = 1;
    }
    if (flagns) break;
    if (!*control) return 0; /* q is not within our bailiwick */
    control += *control;
    control += 1;
  }
 
  if (!flagauthoritative) {
    response[2] &= ~4;
    goto AUTHORITY; /* q is in a child zone */
  }
 
 
  flaggavesoa = 0;
  flagfound = 0;
  wild = q;
 
  for (;;) {
    addr4num = addr6num = 0;
    addr4ttl = addr6ttl = 0;
    cdb_findstart(&c);
    while ((r = find(wild,wild != q))) {
      if (r == -1) return 0;
      flagfound = 1;
      if (flaggavesoa && byte_equal(type,2,DNS_T_SOA)) continue;
      if (byte_diff(type,2,qtype) && byte_diff(qtype,2,DNS_T_ANY) && 
          byte_diff(type,2,DNS_T_CNAME)) continue;
 
      if (byte_equal(type,2,DNS_T_A) && (dlen - dpos == 4)) {
        addr4ttl = ttl;
        i = dns_random(addr4num + 1);
        if (i < MAX_ANSWERS) {
          if ((i < addr4num) && (addr4num < MAX_ANSWERS))
            byte_copy(addr4[addr4num],4,addr4[i]);
          byte_copy(addr4[i],4,data + dpos);
        }
        if (addr4num < 1000000) ++addr4num;
        continue;
      }
      if (byte_equal(type,2,DNS_T_AAAA) && (dlen - dpos == 16)) {
        addr6ttl = ttl;
        i = dns_random(addr6num + 1);
        if (i < MAX_ANSWERS) {
          if ((i < addr6num) && (addr6num < MAX_ANSWERS))
            byte_copy(addr6[addr6num],16,addr6[i]);
          byte_copy(addr6[i],16,data + dpos);
        }
        if (addr6num < 1000000) ++addr6num;
        continue;
      }
      if (!response_rstart(q,type,ttl)) return 0;
      if (byte_equal(type,2,DNS_T_NS) || 
          byte_equal(type,2,DNS_T_CNAME) || 
          byte_equal(type,2,DNS_T_PTR)) {
        if (!doname()) return 0;
      }
      else if (byte_equal(type,2,DNS_T_MX)) {
        if (!dobytes(2)) return 0;
        if (!doname()) return 0;
      }
      else if (byte_equal(type,2,DNS_T_SOA)) {
        if (!doname()) return 0;
        if (!doname()) return 0;
        if (!dobytes(20)) return 0;
        flaggavesoa = 1;
      }
      else
        if (!response_addbytes(data + dpos,dlen - dpos)) return 0;
      response_rfinish(RESPONSE_ANSWER);
    }
    for (i = 0; i < addr4num; ++i)
      if (i < MAX_ANSWERS) {
        if (!response_rstart(q,DNS_T_A,addr4ttl)) return 0;
        if (!response_addbytes(addr4[i],4)) return 0;
        response_rfinish(RESPONSE_ANSWER);
      }
    for (i = 0; i < addr6num; ++i)
      if (i < MAX_ANSWERS) {
        if (!response_rstart(q,DNS_T_AAAA,addr6ttl)) return 0;
        if (!response_addbytes(addr6[i],16)) return 0;
        response_rfinish(RESPONSE_ANSWER);
      }
 
    if (flagfound) break;
    if (wild == control) break;
    if (!*wild) break; /* impossible */
    wild += *wild;
    wild += 1;
  }
 
  if (!flagfound) response_nxdomain();
 
 
  AUTHORITY:
  aupos = response_len;
 
  if (flagauthoritative && (aupos == anpos)) {
    cdb_findstart(&c);
    while ((r = find(control,0))) {
      if (r == -1) return 0;
      if (byte_equal(type,2,DNS_T_SOA)) {
        if (!response_rstart(control,DNS_T_SOA,ttl)) return 0;
        if (!doname()) return 0;
        if (!doname()) return 0;
        if (!dobytes(20)) return 0;
        response_rfinish(RESPONSE_AUTHORITY);
        break;
      }
    }
  } else if (want(control,DNS_T_NS)) {
      cdb_findstart(&c);
      while ((r = find(control,0))) {
        if (r == -1) return 0;
        if (byte_equal(type,2,DNS_T_NS)) {
          if (!response_rstart(control,DNS_T_NS,ttl)) return 0;
          if (!doname()) return 0;
          response_rfinish(RESPONSE_AUTHORITY);
        }
      }
    }
 
  arpos = response_len;
 
  // Fill Additional Section
 
  bpos = anpos;
  while (bpos < arpos) {
    bpos = dns_packet_skipname(response,arpos,bpos); if (!bpos) return 0;
    bpos = dns_packet_copy(response,arpos,bpos,x,10); if (!bpos) return 0;
 
    if (byte_equal(x,2,DNS_T_NS) || byte_equal(x,2,DNS_T_MX)) {
      if (byte_equal(x,2,DNS_T_NS)) {
        if (!dns_packet_getname(response,arpos,bpos,&d1)) return 0;
      }
      else if (!dns_packet_getname(response,arpos,bpos + 2,&d1)) return 0;
 
      int dl = dns_domain_length(d1); // core a DJB bug
      case_lowerb(d1,dl);
 
      case_lowerb(d1,dns_domain_length(d1));
 
      byte_zero(dn,FQDN_LEN);
      if (want(d1,DNS_T_A) || want(d1,DNS_T_AAAA)) {
        cdb_findstart(&c);
        while ((r = find(d1,0))) {
          if (r == -1) return 0;
          if (byte_equal(type,2,DNS_T_A)) {
            if (byte_equal(d1,dl,dn)) continue;
            if (!response_rstart(d1,DNS_T_A,ttl)) return 0;
            byte_copy(dn,dl,d1);
            if (!dobytes(4)) return 0;
            response_rfinish(RESPONSE_ADDITIONAL);
          }
          else if (byte_equal(type,2,DNS_T_AAAA)) {
            if (byte_equal(d1,dl,dn)) continue;
            if (!response_rstart(d1,DNS_T_AAAA,ttl)) return 0;
            byte_copy(dn,dl,d1);
            if (!dobytes(16)) return 0;
            response_rfinish(RESPONSE_ADDITIONAL);
          }
        }
      }
    }
    uint16_unpack_big(x + 8,&u16);
    bpos += u16;
  }
 
  if (flagauthoritative && (response_len > max_response_len)) {
    byte_zero(response + RESPONSE_ADDITIONAL,2);
    response_len = arpos;
    if (response_len > MSGSIZE) {  // from macro, not udp_msgsize()
      byte_zero(response + RESPONSE_AUTHORITY,2);
      response_len = aupos;
    }
  }
 
  return 1;
}
 
int respond(char *q,char qtype[2],char ip[16])
{
  int fd;
  int r;
 
  find_clientloc(clientloc,ip);
 
  tai_now(&now);
  fd = open_read("data.cdb");
  if (fd == -1) return 0;
  cdb_init(&c,fd);
 
  r = doit(q,qtype);
 
  cdb_free(&c);
  close(fd);
  return r;
}