Poor-Mans-IDS/data.cpp

//////////////////////////////////////////////////////////////////////
// IP traffic analyzer - data objects
// Written by Jonathan A. Foster <ChipMaster@YeOlPiShack.net>
// Started April 23rd, 2021
// Copyright JF Possibilities, Inc. All rights reserved.
//////////////////////////////////////////////////////////////////////
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <stdexcept>
#include <iostream>
#include "data.h"



//////////////////////////////////////////////////////////////////////
// Utils
//////////////////////////////////////////////////////////////////////

std::string ipv6opt(const std::string &addr) {
  in6_addr buf;
  char s[256];

  if(inet_pton(AF_INET6, addr.c_str(), &buf)<1) throw
    std::runtime_error("ipv6opt: inet_pton() says '"+addr+"' is not a valid IPv6 address");
  if(!inet_ntop(AF_INET6, &buf, s, 255)) throw // should never happen
    std::runtime_error("ipv6opt: inet_ntop() refused to convert the address back");
  return std::string(s);
}



int addr_wild_comp(const std::string &str1, const std::string &str2) {
  int spre1=0, spre2=0;

  if(str1=="*" || str2=="*") return 0;
  if(str1!="" && (str1.end()[-1]=='.' || str1.end()[-1]==':')) spre1=str1.size();
  if(str2!="" && (str2.end()[-1]=='.' || str2.end()[-1]==':')) spre2=str2.size();
  if(spre2>spre1) spre1=spre2;
  if(spre1)          return strncmp(str1.c_str(), str2.c_str(), spre1);
  else if(str1<str2) return -1;
  else if(str1>str2) return  1;
                     return  0;
}



//////////////////////////////////////////////////////////////////////
// Conn
//////////////////////////////////////////////////////////////////////

void Conn::clear() {
  us = them = name = protocol = "";
  in=false;
  us_port = them_port = 0;
}



void Conn::compact() {
  if(us.find(':')!=us.npos)   us=ipv6opt(us);
  if(them.find(':')!=us.npos) them=ipv6opt(them);
}



void Conn::swap() {
  std::string s;
  int x;

  s = us;
  us = them;
  them =s;

  x = us_port;
  us_port = them_port;
  them_port = x;

  in=!in;
}



Conn &Conn::operator=(const Splits &sp) {
  int x;

  clear();
  for(x=0; x<sp.count; x++) {
    if(!strncmp(sp.fields[x], "SRC=", 4)) {
      us = sp.fields[x]+4;
      continue;
    }
    if(!strncmp(sp.fields[x], "DST=", 4)) {
      them = sp.fields[x]+4;
      continue;
    }
    if(!strncmp(sp.fields[x], "SPT=", 4)) {
      us_port = atoi(sp.fields[x]+4);
      continue;
    }
    if(!strncmp(sp.fields[x], "DPT=", 4)) {
      them_port = atoi(sp.fields[x]+4);
      continue;
    }
    if(!strncmp(sp.fields[x], "TYPE=", 5) && protocol=="ICMP") {
      us_port = them_port = atoi(sp.fields[x]+5);
      continue;
    }
    if(!strncmp(sp.fields[x], "PROTO=", 6))
      protocol = sp.fields[x]+6;
  }
}



// TODO: does < > have any actual meaning in this context?
int Conn::cmp(const Conn &gtr) const {
  int r;

  if(r = addr_wild_comp(us, gtr.us)) return r;
  // TODO: auto-wildcard port based on in?
  if(us_port && gtr.us_port) { // 0 = no comparison wildcard
    if(us_port<gtr.us_port) return -1;
    if(us_port>gtr.us_port) return  1;
  }
  if(r = addr_wild_comp(them, gtr.them)) return r;
  if(them_port && gtr.them_port) { // 0 = no comparison wildcard
    if(them_port<gtr.them_port) return -1;
    if(them_port>gtr.them_port) return  1;
  }
  // TODO:  do we want to consider the name?
  if(name!="*" && gtr.name!="*") {
    if(name<gtr.name) return -1;
    if(name>gtr.name) return  1;
  }
  if(protocol<gtr.protocol) return -1;
  if(protocol>gtr.protocol) return  1;
  if(in<gtr.in) return -1;
  if(in>gtr.in) return  1;
  return 0;
}



std::ostream &operator<<(std::ostream &out, const Conn &c) {
  out << c.us
      << ( c.in ? " <- " : " -> " )
      << c.them
      << " " << c.protocol
      << "[" << ( c.in ? c.us_port : c.them_port ) << "] "
      << c.name;
  return out;
}



const Splits &operator>>(const Splits &tsv, Conn &conn) {
  if(tsv.count<7) throw std::runtime_error("Conn=TSV: too few columns");
  conn.clear();
  conn.us        = tsv[0];
  conn.us_port   = atoi(tsv.fields[1]);
  conn.them      = tsv[2];
  conn.them_port = atoi(tsv.fields[3]);
  conn.name      = tsv[4];
  conn.protocol  = tsv[5];
  conn.in        = tsv[6]=="1";
  return tsv;
}



//////////////////////////////////////////////////////////////////////
// ConnList
//////////////////////////////////////////////////////////////////////

int ConnList::find(Conn &needle) {
  int r;

  for(r=0; r<size(); r++) if((*this)[r]==needle) return r;
  return -1;
}



//////////////////////////////////////////////////////////////////////
// LogAnalyzer
//////////////////////////////////////////////////////////////////////

LogAnalyzer::LogAnalyzer():
  us(0)
{ // I'd rather this initialization be static...
  dns_ignore.push_back("v=spf1");
  dns_ignore.push_back("https:");
  dns_del.push_back("NODATA-");
  dns_del.push_back("NXDOMAIN-");
}



bool LogAnalyzer::line(const std::string &in) {
  int ict=0;
  NameVal::iterator nvp;
  std::string name, address, s;

  /// setup ///

  if(!us)
    throw std::runtime_error("LogAnalyzer::line: us list is not assigned");
  ln=in;

  ///  DNS query result ///

  // TODO: need to get more specific on tying us + them + time to DNS
  if(ln.count>8 && strncmp(ln.fields[4], "dnsmasq[", 8)==0) {
    if(ln[5]=="reply" || ln[5]=="cached") {
      name = ln[6];
      address = ln[8];

      /* NOTE: CNAME resolution seems to follow this order in logs:

           1. A result line (reply/cached) with an address of <CNAME>
           2. One or more consecutive result lines for the canonical name

         Looking over the logs it doesn't appear that dnsmasq will log
         anything between the original and CNAME resolutions. The exception
         is if a CNAME record is cached and it has to resolve what it
         points to. In this case there would be a "cached" and then a
         "forwarded" record eventually followed by "reply ... <CNAME>".
         In that case we want to operate on the reply.

         I just saw that CNAME log entries can be chained. It looks like
         they are an "is <CNAME>" entry followed by another. We want to
         keep the original name (alias).
      */
      // we're handling a CNAME entry
      if(address=="<CNAME>") {
        // If we don't have a cname yet then this is a CNAME to a CNAME.
        if(alias=="" || cname!="") {
          alias = name;
          cname = "";
        }
        return 0;
      }
      // If in cname _mode_:
      if(alias!="") {
        if(cname=="") {
          cname = name; // This is our target name
          name = alias; // substitute the alias
        } else if(cname==name) {
          name = alias; // substitute the alias
        } else {
          cname = "";   // These are different records reset
          name = "";
        }
      }

      // Hmm... is this reply an address?
      if(pre_match(dns_ignore, address)) return 0; // nope
      if(pre_match(dns_del,    address)) return 0; // does not exist reply
      if((nvp=rdns.find(address))!=rdns.end()) {
        if(nvp->second==name) return 0;
        //dlog("WARN: DNS address overlap "+address+": "+nvp->second+" : "+name);
      }
      rdns[address] = name;
      //dlog("Added "+address+" = "+name);
      return 0;
    } else if(alias!="") {
      // we've fallen out of CNAME resolution.
      alias = "";
      cname = "";
    }
  }

  /// process connections ///

  if((ln.count>5  // old Linux style
  && ln[4]=="kernel:"
  && ln[5]=="ACCEPT"
  ) || (ln.count>6  // new Linux style
  && ln[4]=="vmunix:"
  && ln[6]=="ACCEPT")
  ) {
    conn = ln;
    conn.compact();
    if(!pre_match(*us, conn.us)) conn.swap();
    if((nvp=rdns.find(conn.them))!=rdns.end()) conn.name = nvp->second;
    return 1;
  }
  return 0;
}