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[thirdparty/pdns.git] / pdns / dnsparser.cc

/*
    PowerDNS Versatile Database Driven Nameserver
    Copyright (C) 2005 - 2011  PowerDNS.COM BV

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License version 2 as 
    published by the Free Software Foundation

    Additionally, the license of this program contains a special
    exception which allows to distribute the program in binary form when
    it is linked against OpenSSL.

    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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "dnsparser.hh"
#include "dnswriter.hh"
#include <boost/lexical_cast.hpp>
#include <boost/algorithm/string.hpp>
#include <boost/format.hpp>

#include "namespaces.hh"

class UnknownRecordContent : public DNSRecordContent
{
public:
  UnknownRecordContent(const DNSRecord& dr, PacketReader& pr) 
    : DNSRecordContent(dr.d_type), d_dr(dr)
  {
    pr.copyRecord(d_record, dr.d_clen);
  }

  UnknownRecordContent(const string& zone) : DNSRecordContent(0)
  {
    // parse the input
    vector<string> parts;
    stringtok(parts, zone);
    if(parts.size()!=3 && !(parts.size()==2 && equals(parts[1],"0")) )
      throw MOADNSException("Unknown record was stored incorrectly, need 3 fields, got "+lexical_cast<string>(parts.size())+": "+zone );
    const string& relevant=(parts.size() > 2) ? parts[2] : "";
    unsigned int total=atoi(parts[1].c_str());
    if(relevant.size()!=2*total)
      throw MOADNSException((boost::format("invalid unknown record length for label %s: size not equal to length field (%d != %d)") % d_dr.d_label.c_str() % relevant.size() % (2*total)).str());
    string out;
    out.reserve(total+1);
    for(unsigned int n=0; n < total; ++n) {
      int c;
      sscanf(relevant.c_str()+2*n, "%02x", &c);
      out.append(1, (char)c);
    }

    d_record.insert(d_record.end(), out.begin(), out.end());
  }
  
  string getZoneRepresentation() const
  {
    ostringstream str;
    str<<"\\# "<<(unsigned int)d_record.size()<<" ";
    char hex[4];
    for(size_t n=0; n<d_record.size(); ++n) {
      snprintf(hex,sizeof(hex)-1, "%02x", d_record.at(n));
      str << hex;
    }
    return str.str();
  }
  
  void toPacket(DNSPacketWriter& pw)
  {
    pw.xfrBlob(string(d_record.begin(),d_record.end()));
  }
private:
  DNSRecord d_dr;
  vector<uint8_t> d_record;
};

static const string EncodeDNSLabel(const string& input)
{  
  if(input.length() == 1 && input[0]=='.') // otherwise we encode .. (long story)
    return string (1, 0);
    
  labelparts_t parts;
  bool unescapedSomething = labeltokUnescape(parts, input);
  string ret;

  if(!unescapedSomething) {
    for(labelparts_t::const_iterator i=parts.begin(); i!=parts.end(); ++i) {
      ret.append(1, i->second - i->first);
      ret.append(input.c_str() + i->first, i->second - i->first);
    }

  } else {
    for(labelparts_t::const_iterator i=parts.begin(); i!=parts.end(); ++i) {
      string part(input.c_str() + i->first, i->second - i->first);
      boost::replace_all(part, "\\\\", "\\");
      boost::replace_all(part, "\\.", ".");
    
      ret.append(1, part.length());
      ret.append(part);
    }  
  }    
  ret.append(1, 0);
  return ret;
}


shared_ptr<DNSRecordContent> DNSRecordContent::unserialize(const string& qname, uint16_t qtype, const string& serialized)
{
  dnsheader dnsheader;
  memset(&dnsheader, 0, sizeof(dnsheader));
  dnsheader.qdcount=htons(1);
  dnsheader.ancount=htons(1);

  vector<uint8_t> packet; // build pseudo packet

  /* will look like: dnsheader, 5 bytes, encoded qname, dns record header, serialized data */

  string encoded=EncodeDNSLabel(qname);

  packet.resize(sizeof(dnsheader) + 5 + encoded.size() + sizeof(struct dnsrecordheader) + serialized.size());

  uint16_t pos=0;

  memcpy(&packet[0], &dnsheader, sizeof(dnsheader)); pos+=sizeof(dnsheader);

  char tmp[6]="\x0" "\x0\x1" "\x0\x1"; // root question for ns_t_a
  memcpy(&packet[pos], &tmp, 5); pos+=5;

  memcpy(&packet[pos], encoded.c_str(), encoded.size()); pos+=(uint16_t)encoded.size();

  struct dnsrecordheader drh;
  drh.d_type=htons(qtype);
  drh.d_class=htons(1);
  drh.d_ttl=0;
  drh.d_clen=htons(serialized.size());

  memcpy(&packet[pos], &drh, sizeof(drh)); pos+=sizeof(drh);
  memcpy(&packet[pos], serialized.c_str(), serialized.size()); pos+=(uint16_t)serialized.size();

  MOADNSParser mdp((char*)&*packet.begin(), (unsigned int)packet.size());
  shared_ptr<DNSRecordContent> ret= mdp.d_answers.begin()->first.d_content;
  ret->header.d_type=ret->d_qtype;
  ret->label=mdp.d_answers.begin()->first.d_label;
  ret->header.d_ttl=mdp.d_answers.begin()->first.d_ttl;
  return ret;
}

DNSRecordContent* DNSRecordContent::mastermake(const DNSRecord &dr, 
                                               PacketReader& pr)
{
  uint16_t searchclass = (dr.d_type == QType::OPT) ? 1 : dr.d_class; // class is invalid for OPT

  typemap_t::const_iterator i=getTypemap().find(make_pair(searchclass, dr.d_type));
  if(i==getTypemap().end() || !i->second) {
    return new UnknownRecordContent(dr, pr);
  }

  return i->second(dr, pr);
}

DNSRecordContent* DNSRecordContent::mastermake(uint16_t qtype, uint16_t qclass,
                                               const string& content)
{
  zmakermap_t::const_iterator i=getZmakermap().find(make_pair(qclass, qtype));
  if(i==getZmakermap().end()) {
    return new UnknownRecordContent(content);
  }

  return i->second(content);
}

DNSRecordContent* DNSRecordContent::mastermake(const DNSRecord &dr, PacketReader& pr, uint16_t oc) {
  // For opcode UPDATE and where the DNSRecord is an answer record, we don't care about content, because this is
  // not used within the prerequisite section of RFC2136, so - we can simply use unknownrecordcontent.
  // For section 3.2.3, we do need content so we need to get it properly. But only for the correct Qclasses.
  if (oc == Opcode::Update && dr.d_place == DNSRecord::Answer && dr.d_class != 1)
    return new UnknownRecordContent(dr, pr);

  uint16_t searchclass = (dr.d_type == QType::OPT) ? 1 : dr.d_class; // class is invalid for OPT

  typemap_t::const_iterator i=getTypemap().find(make_pair(searchclass, dr.d_type));
  if(i==getTypemap().end() || !i->second) {
    return new UnknownRecordContent(dr, pr);
  }

  return i->second(dr, pr);
}


DNSRecordContent::typemap_t& DNSRecordContent::getTypemap()
{
  static DNSRecordContent::typemap_t typemap;
  return typemap;
}

DNSRecordContent::n2typemap_t& DNSRecordContent::getN2Typemap()
{
  static DNSRecordContent::n2typemap_t n2typemap;
  return n2typemap;
}

DNSRecordContent::t2namemap_t& DNSRecordContent::getT2Namemap()
{
  static DNSRecordContent::t2namemap_t t2namemap;
  return t2namemap;
}


DNSRecordContent::zmakermap_t& DNSRecordContent::getZmakermap()
{
  static DNSRecordContent::zmakermap_t zmakermap;
  return zmakermap;
}

void MOADNSParser::init(const char *packet, unsigned int len)
{
  if(len < sizeof(dnsheader))
    throw MOADNSException("Packet shorter than minimal header");
  
  memcpy(&d_header, packet, sizeof(dnsheader));

  if(d_header.opcode != Opcode::Query && d_header.opcode != Opcode::Notify && d_header.opcode != Opcode::Update)
    throw MOADNSException("Can't parse non-query packet with opcode="+ lexical_cast<string>(d_header.opcode));

  d_header.qdcount=ntohs(d_header.qdcount);
  d_header.ancount=ntohs(d_header.ancount);
  d_header.nscount=ntohs(d_header.nscount);
  d_header.arcount=ntohs(d_header.arcount);
  
  uint16_t contentlen=len-sizeof(dnsheader);

  d_content.resize(contentlen);
  copy(packet+sizeof(dnsheader), packet+len, d_content.begin());
  
  unsigned int n=0;

  PacketReader pr(d_content);
  bool validPacket=false;
  try {
    d_qtype = d_qclass = 0; // sometimes replies come in with no question, don't present garbage then

    for(n=0;n < d_header.qdcount; ++n) {
      d_qname=pr.getLabel();
      d_qtype=pr.get16BitInt();
      d_qclass=pr.get16BitInt();
    }

    struct dnsrecordheader ah;
    vector<unsigned char> record;
    validPacket=true;
    for(n=0;n < (unsigned int)(d_header.ancount + d_header.nscount + d_header.arcount); ++n) {
      DNSRecord dr;
      
      if(n < d_header.ancount)
        dr.d_place=DNSRecord::Answer;
      else if(n < d_header.ancount + d_header.nscount)
        dr.d_place=DNSRecord::Nameserver;
      else 
        dr.d_place=DNSRecord::Additional;
      
      unsigned int recordStartPos=pr.d_pos;

      string label=pr.getLabel();
      
      pr.getDnsrecordheader(ah);
      dr.d_ttl=ah.d_ttl;
      dr.d_type=ah.d_type;
      dr.d_class=ah.d_class;
      
      dr.d_label=label;
      dr.d_clen=ah.d_clen;

      dr.d_content=std::shared_ptr<DNSRecordContent>(DNSRecordContent::mastermake(dr, pr, d_header.opcode));
      d_answers.push_back(make_pair(dr, pr.d_pos));

      if(dr.d_type == QType::TSIG && dr.d_class == 0xff) 
        d_tsigPos = recordStartPos + sizeof(struct dnsheader);
    }

#if 0    
    if(pr.d_pos!=contentlen) {
      throw MOADNSException("Packet ("+d_qname+"|#"+lexical_cast<string>(d_qtype)+") has trailing garbage ("+ lexical_cast<string>(pr.d_pos) + " < " + 
                            lexical_cast<string>(contentlen) + ")");
    }
#endif 
  }
  catch(std::out_of_range &re) {
    if(validPacket && d_header.tc) { // don't sweat it over truncated packets, but do adjust an, ns and arcount
      if(n < d_header.ancount) {
        d_header.ancount=n; d_header.nscount = d_header.arcount = 0;
      }
      else if(n < d_header.ancount + d_header.nscount) {
        d_header.nscount = n - d_header.ancount; d_header.arcount=0;
      }
      else {
        d_header.arcount = n - d_header.ancount - d_header.nscount;
      }
    }
    else {
      throw MOADNSException("Error parsing packet of "+lexical_cast<string>(len)+" bytes (rd="+
                            lexical_cast<string>(d_header.rd)+
                            "), out of bounds: "+string(re.what()));
    }
  }
}


void PacketReader::getDnsrecordheader(struct dnsrecordheader &ah)
{
  unsigned int n;
  unsigned char *p=reinterpret_cast<unsigned char*>(&ah);
  
  for(n=0; n < sizeof(dnsrecordheader); ++n) 
    p[n]=d_content.at(d_pos++);
  
  ah.d_type=ntohs(ah.d_type);
  ah.d_class=ntohs(ah.d_class);
  ah.d_clen=ntohs(ah.d_clen);
  ah.d_ttl=ntohl(ah.d_ttl);

  d_startrecordpos=d_pos; // needed for getBlob later on
  d_recordlen=ah.d_clen;
}


void PacketReader::copyRecord(vector<unsigned char>& dest, uint16_t len)
{
  dest.resize(len);
  if(!len)
    return;

  for(uint16_t n=0;n<len;++n) {
    dest.at(n)=d_content.at(d_pos++);
  }
}

void PacketReader::copyRecord(unsigned char* dest, uint16_t len)
{
  if(d_pos + len > d_content.size())
    throw std::out_of_range("Attempt to copy outside of packet");

  memcpy(dest, &d_content.at(d_pos), len);
  d_pos+=len;
}

void PacketReader::xfr48BitInt(uint64_t& ret)
{
  ret=0;
  ret+=d_content.at(d_pos++);
  ret<<=8;
  ret+=d_content.at(d_pos++);
  ret<<=8;
  ret+=d_content.at(d_pos++);
  ret<<=8;
  ret+=d_content.at(d_pos++);
  ret<<=8;
  ret+=d_content.at(d_pos++);
  ret<<=8;
  ret+=d_content.at(d_pos++);
}

uint32_t PacketReader::get32BitInt()
{
  uint32_t ret=0;
  ret+=d_content.at(d_pos++);
  ret<<=8;
  ret+=d_content.at(d_pos++);
  ret<<=8;
  ret+=d_content.at(d_pos++);
  ret<<=8;
  ret+=d_content.at(d_pos++);
  
  return ret;
}


uint16_t PacketReader::get16BitInt()
{
  return get16BitInt(d_content, d_pos);
}

uint16_t PacketReader::get16BitInt(const vector<unsigned char>&content, uint16_t& pos)
{
  uint16_t ret=0;
  ret+=content.at(pos++);
  ret<<=8;
  ret+=content.at(pos++);
  
  return ret;
}

uint8_t PacketReader::get8BitInt()
{
  return d_content.at(d_pos++);
}

string PacketReader::getLabel()
{
  unsigned int consumed;
  vector<uint8_t> content(d_content);
  content.insert(content.begin(), sizeof(dnsheader), 0);

  string ret = DNSName((const char*) content.data(), content.size(), d_pos + sizeof(dnsheader), true /* uncompress */, 0 /* qtype */, 0 /* qclass */, &consumed).toString();

  d_pos+=consumed;
  return ret;
}

static string txtEscape(const string &name)
{
  string ret;
  char ebuf[5];

  for(string::const_iterator i=name.begin();i!=name.end();++i) {
    if((unsigned char) *i > 127 || (unsigned char) *i < 32) {
      snprintf(ebuf, sizeof(ebuf), "\\%03u", (unsigned char)*i);
      ret += ebuf;
    }
    else if(*i=='"' || *i=='\\'){
      ret += '\\';
      ret += *i;
    }
    else
      ret += *i;
  }
  return ret;
}

// exceptions thrown here do not result in logging in the main pdns auth server - just so you know!
string PacketReader::getText(bool multi)
{
  string ret;
  ret.reserve(40);
  while(d_pos < d_startrecordpos + d_recordlen ) {
    if(!ret.empty()) {
      ret.append(1,' ');
    }
    unsigned char labellen=d_content.at(d_pos++);
    
    ret.append(1,'"');
    if(labellen) { // no need to do anything for an empty string
      string val(&d_content.at(d_pos), &d_content.at(d_pos+labellen-1)+1);
      ret.append(txtEscape(val)); // the end is one beyond the packet
    }
    ret.append(1,'"');
    d_pos+=labellen;
    if(!multi)
      break;
  }

  return ret;
}


void PacketReader::xfrBlob(string& blob)
try
{
  if(d_recordlen && !(d_pos == (d_startrecordpos + d_recordlen)))
    blob.assign(&d_content.at(d_pos), &d_content.at(d_startrecordpos + d_recordlen - 1 ) + 1);
  else
    blob.clear();

  d_pos = d_startrecordpos + d_recordlen;
}
catch(...)
{
  throw std::out_of_range("xfrBlob out of range");
}

void PacketReader::xfrBlobNoSpaces(string& blob, int length) {
  xfrBlob(blob, length);
}

void PacketReader::xfrBlob(string& blob, int length)
{
  if(length) {
    blob.assign(&d_content.at(d_pos), &d_content.at(d_pos + length - 1 ) + 1 );
    
    d_pos += length;
  }
  else 
    blob.clear();
}


void PacketReader::xfrHexBlob(string& blob, bool keepReading)
{
  xfrBlob(blob);
}

string simpleCompress(const string& elabel, const string& root)
{
  string label=elabel;
  // FIXME: this relies on the semi-canonical escaped output from getLabel
  if(strchr(label.c_str(), '\\')) {
    boost::replace_all(label, "\\.", ".");
    boost::replace_all(label, "\\032", " ");
    boost::replace_all(label, "\\\\", "\\");   
  }
  typedef vector<pair<unsigned int, unsigned int> > parts_t;
  parts_t parts;
  vstringtok(parts, label, ".");
  string ret;
  ret.reserve(label.size()+4);
  for(parts_t::const_iterator i=parts.begin(); i!=parts.end(); ++i) {
    if(!root.empty() && !strncasecmp(root.c_str(), label.c_str() + i->first, 1 + label.length() - i->first)) { // also match trailing 0, hence '1 +'
      const unsigned char rootptr[2]={0xc0,0x11};
      ret.append((const char *) rootptr, 2);
      return ret;
    }
    ret.append(1, (char)(i->second - i->first));
    ret.append(label.c_str() + i->first, i->second - i->first);
  }
  ret.append(1, (char)0);
  return ret;
}


void simpleExpandTo(const string& label, unsigned int frompos, string& ret)
{
  unsigned int labellen=0;
  while((labellen=(unsigned char)label.at(frompos++))) {
    ret.append(label.c_str()+frompos, labellen);
    ret.append(1,'.');
    frompos+=labellen;
  }
}

/** Simple DNSPacketMangler. Ritual is: get a pointer into the packet and moveOffset() to beyond your needs
 *  If you survive that, feel free to read from the pointer */
class DNSPacketMangler
{
public:
  explicit DNSPacketMangler(std::string& packet)
    : d_packet(packet), d_notyouroffset(12), d_offset(d_notyouroffset)
  {}
  
  void skipLabel()
  {
    uint8_t len; 
    while((len=get8BitInt())) { 
      if(len >= 0xc0) { // extended label
        get8BitInt();
        return;
      }
      skipBytes(len);
    }
  }
  void skipBytes(uint16_t bytes)
  {
      moveOffset(bytes);
  }
  uint16_t get16BitInt()
  {
    const char* p = d_packet.c_str() + d_offset;
    moveOffset(2);
    uint16_t ret;
    memcpy(&ret, (void*)p, 2);
    return ntohs(ret);
  }
  
  uint8_t get8BitInt()
  {
    const char* p = d_packet.c_str() + d_offset;
    moveOffset(1);
    return *p;
  }
  
  void skipRData()
  {
    int toskip = get16BitInt();
    moveOffset(toskip);
  }
  void decreaseAndSkip32BitInt(uint32_t decrease)
  {
    const char *p = (const char*)d_packet.c_str() + d_offset;
    moveOffset(4);
    
    uint32_t tmp;
    memcpy(&tmp, (void*) p, sizeof(tmp));
    tmp = ntohl(tmp);
    tmp-=decrease;
    tmp = htonl(tmp);
    d_packet.replace(d_offset-4, sizeof(tmp), (const char*)&tmp, sizeof(tmp));
  }
private:
  void moveOffset(uint16_t by)
  {
    d_notyouroffset += by;
    if(d_notyouroffset > d_packet.length())
      throw std::out_of_range("dns packet out of range: "+lexical_cast<string>(d_notyouroffset) +" > " 
      + lexical_cast<string>(d_packet.length()) );
  }
  std::string& d_packet;
  
  uint32_t d_notyouroffset;  // only 'moveOffset' can touch this
  const uint32_t&  d_offset; // look.. but don't touch
  
};

// method of operation: silently fail if it doesn't work - we're only trying to be nice, don't fall over on it
void ageDNSPacket(std::string& packet, uint32_t seconds)
{
  if(packet.length() < sizeof(dnsheader))
    return;
  try 
  {
    dnsheader dh;
    memcpy((void*)&dh, (const dnsheader*)packet.c_str(), sizeof(dh));
    int numrecords = ntohs(dh.ancount) + ntohs(dh.nscount) + ntohs(dh.arcount);
    DNSPacketMangler dpm(packet);
    
    int n;
    for(n=0; n < ntohs(dh.qdcount) ; ++n) {
      dpm.skipLabel();
      dpm.skipBytes(4); // qtype, qclass
    }
   // cerr<<"Skipped "<<n<<" questions, now parsing "<<numrecords<<" records"<<endl;
    for(n=0; n < numrecords; ++n) {
      dpm.skipLabel();
      
      uint16_t dnstype = dpm.get16BitInt();
      /* uint16_t dnsclass = */ dpm.get16BitInt();
      
      if(dnstype == QType::OPT) // not aging that one with a stick
        break;
      
      dpm.decreaseAndSkip32BitInt(seconds);
      dpm.skipRData();
    }
  }
  catch(...)
  {
    return;
  }
}