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/* Portal */
#include <ESP8266WiFi.h>
#include <ESP8266WebServer.h>
#include <WiFiUdp.h>
/* DNSServer.h */
#define DNS_QR_QUERY 0
#define DNS_QR_RESPONSE 1
#define DNS_OPCODE_QUERY 0
enum class DNSReplyCode
{
NoError = 0,
FormError = 1,
ServerFailure = 2,
NonExistentDomain = 3,
NotImplemented = 4,
Refused = 5,
YXDomain = 6,
YXRRSet = 7,
NXRRSet = 8
};
struct DNSHeader
{
uint16_t ID; // identification number
unsigned char RD : 1; // recursion desired
unsigned char TC : 1; // truncated message
unsigned char AA : 1; // authoritive answer
unsigned char OPCode : 4; // message_type
unsigned char QR : 1; // query/response flag
unsigned char RCode : 4; // response code
unsigned char Z : 3; // its z! reserved
unsigned char RA : 1; // recursion available
uint16_t QDCount; // number of question entries
uint16_t ANCount; // number of answer entries
uint16_t NSCount; // number of authority entries
uint16_t ARCount; // number of resource entries
};
class DNSServer
{
public:
DNSServer();
void processNextRequest();
// Returns true if successful, false if there are no sockets available
bool start(const IPAddress &resolvedIP);
// stops the DNS server
void stop();
private:
WiFiUDP _udp;
uint16_t _port;
String _domainName;
unsigned char _resolvedIP[4];
int _currentPacketSize;
unsigned char* _buffer;
DNSHeader* _dnsHeader;
uint32_t _ttl;
DNSReplyCode _errorReplyCode;
bool requestIncludesOnlyOneQuestion();
String getDomainName();
void replyWithIP();
};
/* end DNSServer.h */
/* main code */
DNSServer dns;
ESP8266WebServer server(80);
#define LOGLENGTH 50
String domainlog[LOGLENGTH];
int logptr = 0;
void logDomain(String requestUrl) {
if (++logptr == LOGLENGTH) {
logptr = 0;
}
domainlog[logptr] = requestUrl;
}
void serve() {
String answer = "";
for (int i=0; i<logptr; i++) {
answer.concat(domainlog[i]);
answer += "\n";
}
server.send(200, "text/plain", answer);
}
void setup() {
WiFi.softAP("Portal");
IPAddress ip = WiFi.softAPIP();
dns.start(ip);
server.onNotFound(serve);
server.begin();
}
void loop() {
dns.processNextRequest();
server.handleClient();
}
/* end main code */
/* modified DNSServer.cpp */
#include <lwip/def.h>
#include <Arduino.h>
DNSServer::DNSServer()
{
_ttl = htonl(600);
_errorReplyCode = DNSReplyCode::NonExistentDomain;
}
bool DNSServer::start(const IPAddress &resolvedIP)
{
_port = 53;
_buffer = NULL;
_resolvedIP[0] = resolvedIP[0];
_resolvedIP[1] = resolvedIP[1];
_resolvedIP[2] = resolvedIP[2];
_resolvedIP[3] = resolvedIP[3];
return _udp.begin(_port) == 1;
}
void DNSServer::stop()
{
_udp.stop();
free(_buffer);
_buffer = NULL;
}
void DNSServer::processNextRequest()
{
_currentPacketSize = _udp.parsePacket();
if (_currentPacketSize)
{
if (_buffer != NULL) free(_buffer);
_buffer = (unsigned char*)malloc(_currentPacketSize * sizeof(char));
if (_buffer == NULL) return;
_udp.read(_buffer, _currentPacketSize);
_dnsHeader = (DNSHeader*) _buffer;
if (_dnsHeader->QR == DNS_QR_QUERY &&
_dnsHeader->OPCode == DNS_OPCODE_QUERY &&
requestIncludesOnlyOneQuestion())
{
logDomain(getDomainName());
replyWithIP(); // reply with the same ip regardless of request
}
}
}
String DNSServer::getDomainName()
{
String parsedDomainName = "";
if (_buffer == NULL) return parsedDomainName;
unsigned char *start = _buffer + 12;
if (*start == 0)
{
return parsedDomainName;
}
int pos = 0;
while(true)
{
unsigned char labelLength = *(start + pos);
for(int i = 0; i < labelLength; i++)
{
pos++;
parsedDomainName += (char)*(start + pos);
}
pos++;
if (*(start + pos) == 0)
{
return parsedDomainName;
}
else
{
parsedDomainName += ".";
}
}
}
bool DNSServer::requestIncludesOnlyOneQuestion()
{
return ntohs(_dnsHeader->QDCount) == 1 &&
_dnsHeader->ANCount == 0 &&
_dnsHeader->NSCount == 0 &&
_dnsHeader->ARCount == 0;
}
void DNSServer::replyWithIP()
{
if (_buffer == NULL) return;
_dnsHeader->QR = DNS_QR_RESPONSE;
_dnsHeader->ANCount = _dnsHeader->QDCount;
_dnsHeader->QDCount = _dnsHeader->QDCount;
//_dnsHeader->RA = 1;
_udp.beginPacket(_udp.remoteIP(), _udp.remotePort());
_udp.write(_buffer, _currentPacketSize);
_udp.write((uint8_t)192); // answer name is a pointer
_udp.write((uint8_t)12); // pointer to offset at 0x00c
_udp.write((uint8_t)0); // 0x0001 answer is type A query (host address)
_udp.write((uint8_t)1);
_udp.write((uint8_t)0); //0x0001 answer is class IN (internet address)
_udp.write((uint8_t)1);
_udp.write((unsigned char*)&_ttl, 4);
// Length of RData is 4 bytes (because, in this case, RData is IPv4)
_udp.write((uint8_t)0);
_udp.write((uint8_t)4);
_udp.write(_resolvedIP, sizeof(_resolvedIP));
_udp.endPacket();
}
/* end DNSServer.cpp */
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