471 lines
13 KiB
C++
471 lines
13 KiB
C++
#include <arpa/inet.h>
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#include <libmnl/libmnl.h>
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#include <type_traits>
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#include <tins/tins.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter/nfnetlink.h>
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#include <linux/types.h>
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#include <linux/netfilter/nfnetlink_queue.h>
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#include <libnetfilter_queue/libnetfilter_queue.h>
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#include <linux/netfilter/nfnetlink_conntrack.h>
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#include <stdexcept>
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#include <iostream>
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#include <cstring>
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#include <cstdlib>
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#include <cerrno>
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#include <sstream>
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#include <thread>
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#include <mutex>
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#include <jpcre2.hpp>
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using namespace std;
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using namespace Tins;
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typedef jpcre2::select<char> jp;
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mutex stdout_mutex;
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bool unhexlify(string const &hex, string &newString) {
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try{
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int len = hex.length();
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for(int i=0; i< len; i+=2)
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{
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std::string byte = hex.substr(i,2);
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char chr = (char) (int)strtol(byte.c_str(), NULL, 16);
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newString.push_back(chr);
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}
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return true;
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}
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catch (...){
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return false;
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}
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}
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typedef pair<string,jp::Regex> regex_rule_pair;
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typedef vector<regex_rule_pair> regex_rule_vector;
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struct regex_rules{
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regex_rule_vector output_whitelist, input_whitelist, output_blacklist, input_blacklist;
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regex_rule_vector* getByCode(char code){
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switch(code){
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case 'C': // Client to server Blacklist
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return &output_blacklist; break;
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case 'c': // Client to server Whitelist
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return &output_whitelist; break;
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case 'S': // Server to client Blacklist
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return &input_blacklist; break;
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case 's': // Server to client Whitelist
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return &input_whitelist; break;
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}
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throw invalid_argument( "Expected 'C' 'c' 'S' or 's'" );
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}
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int add(const char* arg){
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//Integrity checks
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size_t arg_len = strlen(arg);
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if (arg_len < 2 || arg_len%2 != 0){
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cerr << "[warning] [regex_rules.add] invalid arg passed (" << arg << "), skipping..." << endl;
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return -1;
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}
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if (arg[0] != '0' && arg[0] != '1'){
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cerr << "[warning] [regex_rules.add] invalid is_case_sensitive (" << arg[0] << ") in '" << arg << "', must be '1' or '0', skipping..." << endl;
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return -1;
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}
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if (arg[1] != 'C' && arg[1] != 'c' && arg[1] != 'S' && arg[1] != 's'){
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cerr << "[warning] [regex_rules.add] invalid filter_type (" << arg[1] << ") in '" << arg << "', must be 'C', 'c', 'S' or 's', skipping..." << endl;
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return -1;
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}
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string hex(arg+2), expr;
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if (!unhexlify(hex, expr)){
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cerr << "[warning] [regex_rules.add] invalid hex regex value (" << hex << "), skipping..." << endl;
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return -1;
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}
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//Push regex
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jp::Regex regex(expr,arg[0] == '1'?"gS":"giS");
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if (regex){
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cerr << "[info] [regex_rules.add] adding new regex filter: '" << expr << "'" << endl;
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getByCode(arg[1])->push_back(make_pair(string(arg), regex));
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} else {
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cerr << "[warning] [regex_rules.add] compiling of '" << expr << "' regex failed, skipping..." << endl;
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return -1;
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}
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return 0;
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}
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bool check(unsigned char* data, const size_t& bytes_transferred, const bool in_input){
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string str_data((char *) data, bytes_transferred);
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for (regex_rule_pair ele:(in_input?input_blacklist:output_blacklist)){
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try{
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if(ele.second.match(str_data)){
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unique_lock<mutex> lck(stdout_mutex);
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cout << "BLOCKED " << ele.first << endl;
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return false;
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}
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} catch(...){
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cerr << "[info] [regex_rules.check] Error while matching blacklist regex: " << ele.first << endl;
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}
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}
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for (regex_rule_pair ele:(in_input?input_whitelist:output_whitelist)){
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try{
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if(!ele.second.match(str_data)){
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unique_lock<mutex> lck(stdout_mutex);
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cout << "BLOCKED " << ele.first << endl;
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return false;
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}
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} catch(...){
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cerr << "[info] [regex_rules.check] Error while matching whitelist regex: " << ele.first << endl;
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}
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}
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return true;
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}
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};
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shared_ptr<regex_rules> regex_config;
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typedef bool NetFilterQueueCallback(const uint8_t*,uint32_t);
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PDU * find_transport_layer(PDU* pkt){
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while(pkt != NULL){
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if (pkt->pdu_type() == PDU::TCP || pkt->pdu_type() == PDU::UDP) {
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return pkt;
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}
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pkt = pkt->inner_pdu();
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}
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return pkt;
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}
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template <NetFilterQueueCallback callback_func>
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class NetfilterQueue {
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public:
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size_t BUF_SIZE = 0xffff + (MNL_SOCKET_BUFFER_SIZE/2);
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char *buf = NULL;
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unsigned int portid;
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u_int16_t queue_num;
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struct mnl_socket* nl = NULL;
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NetfilterQueue(u_int16_t queue_num): queue_num(queue_num) {
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struct nlmsghdr *nlh;
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nl = mnl_socket_open(NETLINK_NETFILTER);
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if (nl == NULL) { throw runtime_error( "mnl_socket_open" );}
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if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
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mnl_socket_close(nl);
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throw runtime_error( "mnl_socket_bind" );
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}
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portid = mnl_socket_get_portid(nl);
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buf = (char*) malloc(BUF_SIZE);
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if (!buf) {
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mnl_socket_close(nl);
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throw runtime_error( "allocate receive buffer" );
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}
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if (send_config_cmd(NFQNL_CFG_CMD_BIND) < 0) {
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_clear();
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throw runtime_error( "mnl_socket_send" );
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}
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//TESTING QUEUE: TODO find a legal system to test if the queue was binded successfully
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if (send_config_cmd(NFQNL_CFG_CMD_NONE) < 0) {
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_clear();
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throw runtime_error( "mnl_socket_send" );
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}
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if (recv_packet() == -1) {
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_clear();
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throw std::runtime_error( "mnl_socket_recvfrom" );
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}
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/*
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I checked that if this byte (that is the only one that changes) is set to 1,
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this message is the NFQNL_CFG_CMD_BIND error, instead
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if it is set to 0, this message is the error generated by NFQNL_CFG_CMD_NONE
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So NFQNL_CFG_CMD_BIND doesn't sended any error and it's all ok.
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*/
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if (buf[44] == 1){
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_clear();
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throw std::invalid_argument( "queueid is already busy" );
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}
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//END TESTING QUEUE
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nlh = nfq_nlmsg_put(buf, NFQNL_MSG_CONFIG, queue_num);
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nfq_nlmsg_cfg_put_params(nlh, NFQNL_COPY_PACKET, 0xffff);
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mnl_attr_put_u32(nlh, NFQA_CFG_FLAGS, htonl(NFQA_CFG_F_GSO));
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mnl_attr_put_u32(nlh, NFQA_CFG_MASK, htonl(NFQA_CFG_F_GSO));
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if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
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_clear();
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throw runtime_error( "mnl_socket_send" );
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}
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}
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void run(){
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/*
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* ENOBUFS is signalled to userspace when packets were lost
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* on kernel side. In most cases, userspace isn't interested
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* in this information, so turn it off.
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*/
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int ret = 1;
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mnl_socket_setsockopt(nl, NETLINK_NO_ENOBUFS, &ret, sizeof(int));
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for (;;) {
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ret = recv_packet();
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if (ret == -1) {
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throw std::runtime_error( "mnl_socket_recvfrom" );
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}
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ret = mnl_cb_run(buf, ret, 0, portid, queue_cb, nl);
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if (ret < 0){
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throw std::runtime_error( "mnl_cb_run" );
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}
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}
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}
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~NetfilterQueue() {
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send_config_cmd(NFQNL_CFG_CMD_UNBIND);
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_clear();
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}
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private:
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ssize_t send_config_cmd(nfqnl_msg_config_cmds cmd){
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struct nlmsghdr *nlh = nfq_nlmsg_put(buf, NFQNL_MSG_CONFIG, queue_num);
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nfq_nlmsg_cfg_put_cmd(nlh, AF_INET, cmd);
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return mnl_socket_sendto(nl, nlh, nlh->nlmsg_len);
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}
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ssize_t recv_packet(){
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return mnl_socket_recvfrom(nl, buf, BUF_SIZE);
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}
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void _clear(){
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if (buf != NULL) {
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free(buf);
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buf = NULL;
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}
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mnl_socket_close(nl);
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}
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static int queue_cb(const struct nlmsghdr *nlh, void *data)
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{
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struct mnl_socket* nl = (struct mnl_socket*)data;
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//Extract attributes from the nlmsghdr
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struct nlattr *attr[NFQA_MAX+1] = {};
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if (nfq_nlmsg_parse(nlh, attr) < 0) {
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perror("problems parsing");
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return MNL_CB_ERROR;
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}
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if (attr[NFQA_PACKET_HDR] == NULL) {
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fputs("metaheader not set\n", stderr);
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return MNL_CB_ERROR;
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}
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//Get Payload
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uint16_t plen = mnl_attr_get_payload_len(attr[NFQA_PAYLOAD]);
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void *payload = mnl_attr_get_payload(attr[NFQA_PAYLOAD]);
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//Return result to the kernel
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struct nfqnl_msg_packet_hdr *ph = (nfqnl_msg_packet_hdr*) mnl_attr_get_payload(attr[NFQA_PACKET_HDR]);
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struct nfgenmsg *nfg = (nfgenmsg *)mnl_nlmsg_get_payload(nlh);
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char buf[MNL_SOCKET_BUFFER_SIZE];
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struct nlmsghdr *nlh_verdict;
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struct nlattr *nest;
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nlh_verdict = nfq_nlmsg_put(buf, NFQNL_MSG_VERDICT, ntohs(nfg->res_id));
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/*
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This define allow to avoid to allocate new heap memory for each packet.
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The code under this comment is replicated for ipv6 and ip
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Better solutions are welcome. :)
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*/
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#define PKT_HANDLE \
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PDU *transport_layer = find_transport_layer(&packet); \
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if(transport_layer->inner_pdu() == nullptr || transport_layer == nullptr){ \
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nfq_nlmsg_verdict_put(nlh_verdict, ntohl(ph->packet_id), NF_ACCEPT ); \
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}else{ \
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int size = transport_layer->inner_pdu()->size(); \
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if(callback_func((const uint8_t*)payload+plen - size, size)){ \
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nfq_nlmsg_verdict_put(nlh_verdict, ntohl(ph->packet_id), NF_ACCEPT ); \
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} else{ \
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if (transport_layer->pdu_type() == PDU::TCP){ \
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((TCP *)transport_layer)->release_inner_pdu(); \
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((TCP *)transport_layer)->set_flag(TCP::FIN,1); \
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((TCP *)transport_layer)->set_flag(TCP::ACK,1); \
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((TCP *)transport_layer)->set_flag(TCP::SYN,0); \
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nfq_nlmsg_verdict_put_pkt(nlh_verdict, packet.serialize().data(), packet.size()); \
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nfq_nlmsg_verdict_put(nlh_verdict, ntohl(ph->packet_id), NF_ACCEPT ); \
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}else{ \
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nfq_nlmsg_verdict_put(nlh_verdict, ntohl(ph->packet_id), NF_DROP ); \
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} \
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} \
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}
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// Check IP protocol version
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if ( (((uint8_t*)payload)[0] & 0xf0) == 0x40 ){
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IP packet = IP((uint8_t*)payload,plen);
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PKT_HANDLE
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}else{
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IPv6 packet = IPv6((uint8_t*)payload,plen);
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PKT_HANDLE
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}
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/* example to set the connmark. First, start NFQA_CT section: */
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nest = mnl_attr_nest_start(nlh_verdict, NFQA_CT);
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/* then, add the connmark attribute: */
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mnl_attr_put_u32(nlh_verdict, CTA_MARK, htonl(42));
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/* more conntrack attributes, e.g. CTA_LABELS could be set here */
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/* end conntrack section */
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mnl_attr_nest_end(nlh_verdict, nest);
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if (mnl_socket_sendto(nl, nlh_verdict, nlh_verdict->nlmsg_len) < 0) {
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throw std::runtime_error( "mnl_socket_send" );
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}
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return MNL_CB_OK;
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}
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};
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bool is_sudo(){
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return getuid() == 0;
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}
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void config_updater (){
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string line, data;
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while (true){
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getline(cin, line);
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if (cin.bad()){
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cerr << "[fatal] [upfdater] cin.bad() != 0" << endl;
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exit(EXIT_FAILURE);
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}
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cerr << "[info] [updater] Updating configuration with line " << line << endl;
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istringstream config_stream(line);
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regex_rules *regex_new_config = new regex_rules();
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while(!config_stream.eof()){
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config_stream >> data;
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regex_new_config->add(data.c_str());
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}
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regex_config.reset(regex_new_config);
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cerr << "[info] [updater] Config update done" << endl;
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}
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}
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template <NetFilterQueueCallback func>
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class NFQueueSequence{
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private:
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vector<NetfilterQueue<func> *> nfq;
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uint16_t _init;
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uint16_t _end;
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vector<thread> threads;
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public:
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static const int QUEUE_BASE_NUM = 1000;
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NFQueueSequence(uint16_t seq_len){
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if (seq_len <= 0) throw invalid_argument("seq_len <= 0");
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nfq = vector<NetfilterQueue<func>*>(seq_len);
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_init = QUEUE_BASE_NUM;
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while(nfq[0] == NULL){
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if (_init+seq_len-1 >= 65536){
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throw runtime_error("NFQueueSequence: too many queues!");
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}
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for (int i=0;i<seq_len;i++){
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try{
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nfq[i] = new NetfilterQueue<func>(_init+i);
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}catch(const invalid_argument e){
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for(int j = 0; j < i; j++) {
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delete nfq[j];
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nfq[j] = nullptr;
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}
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_init += seq_len - i;
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break;
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}
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}
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}
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_end = _init + seq_len - 1;
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}
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void start(){
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if (threads.size() != 0) throw runtime_error("NFQueueSequence: already started!");
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for (int i=0;i<nfq.size();i++){
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threads.push_back(thread(&NetfilterQueue<func>::run, nfq[i]));
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}
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}
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void join(){
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for (int i=0;i<nfq.size();i++){
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threads[i].join();
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}
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threads.clear();
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}
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uint16_t init(){
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return _init;
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}
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uint16_t end(){
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return _end;
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}
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~NFQueueSequence(){
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for (int i=0;i<nfq.size();i++){
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delete nfq[i];
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}
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}
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};
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template <bool is_input>
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bool filter_callback(const uint8_t *data, uint32_t len){
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shared_ptr<regex_rules> current_config = regex_config;
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return current_config->check((unsigned char *)data, len, is_input);
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}
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int main(int argc, char *argv[])
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{
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if(!is_sudo()){
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cerr << "[fatal] [main] You must be root to run this program" << endl;
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exit(EXIT_FAILURE);
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}
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int n_of_queue = 1;
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if (argc >= 2) n_of_queue = atoi(argv[1]);
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regex_config.reset(new regex_rules());
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NFQueueSequence<filter_callback<true>> input_queues(n_of_queue);
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input_queues.start();
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NFQueueSequence<filter_callback<false>> output_queues(n_of_queue);
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output_queues.start();
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cout << "QUEUES INPUT " << input_queues.init() << " " << input_queues.end() << " OUTPUT " << output_queues.init() << " " << output_queues.end() << endl;
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config_updater();
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}
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/*
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libpcre2-dev
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libnetfilter-queue-dev
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libtins-dev
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libmnl-dev
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c++ nfqueue.cpp -o nfqueue -pthread -lpcre2-8 -ltins -lnetfilter_queue -lmnl
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WORKDIR /tmp/
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RUN git clone --branch release https://github.com/jpcre2/jpcre2
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WORKDIR /tmp/jpcre2
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RUN ./configure; make; make install
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WORKDIR /
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//NFQNL_CFG_CMD_UNBIND ???
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*/ |