axfrdns.c

Go to the documentation of this file.

#include <unistd.h>
#include "droproot.h"
#include "exit.h"
#include "env.h"
#include "uint_t.h"
#include "ip.h"
#include "tai.h"
#include "buffer.h"
#include "timeout.h"
#include "open.h"
#include "seek.h"
#include "cdbread.h"
#include "stralloc.h"
#include "logmsg.h"
#include "str.h"
#include "byte.h"
#include "case.h"
#include "dns.h"
#include "scan.h"
#include "qlog.h"
#include "response.h"
#include "clientloc.h"
 
extern int respond(char *,char *,char *);
 
#define WHO "axfrdns"
 
unsigned int flagedns0 = 0;
unsigned int msgsize = MSGSIZE;
 
void nomem()
{
  logmsg(WHO,111,FATAL,"out of memory");
}
void die_truncated()
{
  logmsg(WHO,111,FATAL,"truncated request");
}
void die_netwrite()
{
  logmsg(WHO,111,FATAL,"unable to write to network");
}
void die_netread()
{
  logmsg(WHO,111,FATAL,"unable to read from network");
}
void die_outside()
{
  logmsg(WHO,111,FATAL,"unable to locate information in data.cdb");
}
void die_cdbread()
{
  logmsg(WHO,111,FATAL,"unable to read data.cdb");
}
void die_cdbformat()
{
  logmsg(WHO,111,FATAL,B("unable to read data.cdb: ","format error"));
}
 
ssize_t safewrite(int fd,char *buf,size_t len)
{
  int r;
 
  r = timeoutwrite(60,fd,buf,len);
  if (r <= 0) die_netwrite();
  return r;
}
 
char netwritespace[1024];
buffer netwrite = BUFFER_INIT(safewrite,1,netwritespace,sizeof(netwritespace));
 
void print(char *buf,unsigned int len)
{
  char tcpheader[2];
  uint16_pack_big(tcpheader,len);
  buffer_put(&netwrite,tcpheader,2);
  buffer_put(&netwrite,buf,len);
  buffer_flush(&netwrite);
}
 
char *axfr;
static char *axfrok;
 
void axfrcheck(char *q)
{
  int i;
  int j;
 
  if (!axfr) return;
 
  i = j = 0;
  for (;;) {
    if (!axfr[i] || (axfr[i] == '/')) {
      if (i > j) {
        if (dns_domain_fromdot(&axfrok,axfr + j,i - j) <= 0) nomem();
        if (dns_domain_equal(q,axfrok)) return;
      }
      j = i + 1;
    }
    if (!axfr[i]) break;
    ++i;
  }
 
  logmsg(WHO,111,FATAL,"disallowed zone transfer request");
}
 
static char *zone;
unsigned int zonelen;
char typeclass[4];
 
int fdcdb;
buffer bcdb;
char bcdbspace[1024];
 
void get_cdb(char *buf,unsigned int len)
{
  int r;
 
  while (len > 0) {
    r = buffer_get(&bcdb,buf,len);
    if (r < 0) die_cdbread();
    if (!r) die_cdbformat();
    buf += r;
    len -= r;
  }
}
 
char ip[16];
unsigned long port;
char clientloc[2];
 
struct tai now;
char data[32767];
uint32 dlen;
uint32 dpos;
 
void dns_copy(char *buf,unsigned int len)
{
  dpos = dns_packet_copy(data,dlen,dpos,buf,len);
  if (!dpos) die_cdbread();
}
 
void doname(stralloc *sa)
{
  static char *d;
  dpos = dns_packet_getname(data,dlen,dpos,&d);
  if (!dpos) die_cdbread();
  if (!stralloc_catb(sa,d,dns_domain_length(d))) nomem();
}
 
int build(stralloc *sa,char *q,int flagsoa,char id[2])
{
  unsigned int rdatapos;
  char misc[20];
  char type[2];
  char recordloc[2];
  char ttl[4];
  char ttd[8];
  struct tai cutoff;
 
  dpos = 0;
  dns_copy(type,2);
  if (flagsoa) if (byte_diff(type,2,DNS_T_SOA)) return 0;
  if (!flagsoa) if (byte_equal(type,2,DNS_T_SOA)) return 0;
 
/*
        Byte  \204 (meaning: response, opcode 0, authoritative, not truncated, recursion not desired), or, optionally, 
                             QR        OPCODE    AA             TC             RD      
              \205 if the client used byte \001. named-xfer rejects responses that do not have at least bits \204.
        Byte  \000 (meaning: recursion not available, no Z bits, RCODE 0), or, optionally, \200.
                             RA                          Z+AD+CD RCODE 
        Bytes \000\000 (meaning no questions), or \000\001 (meaning one question).
                        QDCOUNT=0                  QDCOUNT=1
2 bytes, nly  \000\001, indicating the number of answer records below.
                        ANCOUNT
        Bytes \000\000 (meaning no authority records).
                        NSCOUNT
        Bytes \000\000 (meaning no additional records).
                        ARCOUNT  
        NOTE: \000 = \00 = \0
*/
 
  if (!stralloc_copyb(sa,id,2)) nomem();                               // ID
  if (!stralloc_catb(sa,"\204\000\0\0\0\1\0\0\0\0",10)) nomem();       // following header
 
  dns_copy(misc,1);
  if ((misc[0] == '=' + 1) || (misc[0] == '*' + 1)) {                  // '*'+1 = 43; '='+1 = 62; bug fix?
    --misc[0];
    dns_copy(recordloc,2);
    if (byte_diff(recordloc,2,clientloc)) return 0;
  }
  if (misc[0] == '*') {
    if (flagsoa) return 0;
    if (!stralloc_catb(sa,"\1*",2)) nomem();
  }
  if (!stralloc_catb(sa,q,dns_domain_length(q))) nomem();
  if (!stralloc_catb(sa,type,2)) nomem();
 
  dns_copy(ttl,4);
  dns_copy(ttd,8);
  if (byte_diff(ttd,8,"\0\0\0\0\0\0\0\0")) {
    tai_unpack(ttd,&cutoff);
    if (byte_equal(ttl,4,"\0\0\0\0")) {
      if (tai_less(&cutoff,&now)) return 0;
      uint32_pack_big(ttl,2);
    }
    else
      if (!tai_less(&cutoff,&now)) return 0;
  }
 
  if (!stralloc_catb(sa,DNS_C_IN,2)) nomem();
  if (!stralloc_catb(sa,ttl,4)) nomem();
  if (!stralloc_catb(sa,"\0\0",2)) nomem();
  rdatapos = sa->len;
 
  if (byte_equal(type,2,DNS_T_SOA)) {
    doname(sa);
    doname(sa);
    dns_copy(misc,20);
    if (!stralloc_catb(sa,misc,20)) nomem();
  }
  else if (byte_equal(type,2,DNS_T_NS) || byte_equal(type,2,DNS_T_PTR) || byte_equal(type,2,DNS_T_CNAME)) {
    doname(sa);
  }
  else if (byte_equal(type,2,DNS_T_MX)) {
    dns_copy(misc,2);
    if (!stralloc_catb(sa,misc,2)) nomem();
    doname(sa);
  }
  else
    if (!stralloc_catb(sa,data + dpos,dlen - dpos)) nomem();
 
  if (sa->len > 65535) die_cdbformat();
  uint16_pack_big(sa->s + rdatapos - 2,sa->len - rdatapos);
  return 1;
}
 
static struct cdb c;
static char *q;
static stralloc soa;
static stralloc message;
 
void doaxfr(char id[2])
{
  char key[MSGSIZE];
  uint32 klen;
  char num[4];
  uint32 eod;
  uint32 pos;
  int r;
 
  axfrcheck(zone);
 
  find_clientloc(clientloc,ip);
 
  tai_now(&now);
  cdb_init(&c,fdcdb);
 
  cdb_findstart(&c);
  for (;;) {
    r = cdb_findnext(&c,zone,zonelen);
    if (r == -1) die_cdbread();
    if (!r) die_outside();
    dlen = cdb_datalen(&c);
    if (dlen > sizeof(data)) die_cdbformat();
    if (cdb_read(&c,data,dlen,cdb_datapos(&c)) == -1) die_cdbformat();
    if (build(&soa,zone,1,id)) break;
  }
 
  cdb_free(&c);
  print(soa.s,soa.len);
 
  seek_begin(fdcdb);
  buffer_init(&bcdb,buffer_unixread,fdcdb,bcdbspace,sizeof(bcdbspace));
 
  pos = 0;
  get_cdb(num,4); pos += 4;
  uint32_unpack(num,&eod);
  while (pos < 2048) { get_cdb(num,4); pos += 4; }
 
  while (pos < eod) {
    if (eod - pos < 8) die_cdbformat();
    get_cdb(num,4); pos += 4;
    uint32_unpack(num,&klen);
    get_cdb(num,4); pos += 4;
    uint32_unpack(num,&dlen);
    if (eod - pos < klen) die_cdbformat();
    pos += klen;
    if (eod - pos < dlen) die_cdbformat();
    pos += dlen;
 
    if (klen > sizeof(key)) die_cdbformat();
    get_cdb(key,klen);
    if (dlen > sizeof(data)) die_cdbformat();
    get_cdb(data,dlen);
 
    if ((klen > 1) && (key[0] == 0)) continue; /* location */
    if (klen < 1) die_cdbformat();
    if (dns_packet_getname(key,klen,0,&q) != klen) die_cdbformat();
    if (!dns_domain_suffix(q,zone)) continue;
    if (!build(&message,q,0,id)) continue;
    print(message.s,message.len);
  }
 
  print(soa.s,soa.len);
}
 
void netread(char *buf,unsigned int len)
{
  int r;
 
  while (len > 0) {
    r = timeoutread(60,0,buf,len);
    if (r == 0) _exit(0);
    if (r < 0) die_netread();
    buf += r; len -= r;
  }
}
 
char tcpheader[2];
char buf[MSGSIZE];
uint16 len;
 
static char seed[128];
 
int main()
{
  unsigned int pos;
  char header[12];
  char qtype[2];
  char qclass[2];
  const char *x;
 
  droproot(WHO);
  dns_random_init(seed);
 
  axfr = env_get("AXFR");
  
  x = env_get("TCP6REMOTEIP");
  if (!x) x = env_get("TCPREMOTEIP");
  if (x && ip6_scan(x,ip))
    ;
  else
    byte_zero(ip,16);
 
  x = env_get("TCP6REMOTEPORT");
  if (!x)
    x = env_get("TCPREMOTEPORT");
  if (!x) x = "0";
  scan_dnum(x,&port);
 
  for (;;) {
    netread(tcpheader,2);
    uint16_unpack_big(tcpheader,&len);
    if (len > MSGSIZE) logmsg(WHO,111,FATAL,"excessively large request");
    netread(buf,len);
 
    pos = dns_packet_copy(buf,len,0,header,12); if (!pos) die_truncated();
    if (header[2] & 254) logmsg(WHO,111,FATAL,"bogus query");
    if (header[4] || (header[5] != 1)) logmsg(WHO,111,FATAL,"bogus query");
 
    pos = dns_packet_getname(buf,len,pos,&zone); if (!pos) die_truncated();
    zonelen = dns_domain_length(zone);
    pos = dns_packet_copy(buf,len,pos,qtype,2); if (!pos) die_truncated();
    pos = dns_packet_copy(buf,len,pos,qclass,2); if (!pos) die_truncated();
 
    if (byte_diff(qclass,2,DNS_C_IN) && byte_diff(qclass,2,DNS_C_ANY))
      logmsg(WHO,111,FATAL,"bogus query: bad class");
 
    qlog(ip,port,header,zone,qtype," ");
 
    if (byte_equal(qtype,2,DNS_T_AXFR)) {
      case_lowerb(zone,zonelen);
      fdcdb = open_read("data.cdb");
      if (fdcdb == -1) die_cdbread();
      doaxfr(header);
      close(fdcdb);
    }
    else {
      if (!response_query(zone,qtype,qclass)) nomem();
      response[2] |= 4;
      case_lowerb(zone,zonelen);
      response_id(header);
      response[3] &= ~128;
      if (!(header[2] & 1)) response[2] &= ~1;
      if (!respond(zone,qtype,ip)) die_outside();
      print(response,response_len);
    }
  }
}