#include <string.h>
#include <fstream>
#include <sstream>
#include <boost/regex.hpp>
#include <boost/filesystem.hpp>
#include <cryptopp/hmac.h>
#include <cryptopp/osrng.h>
#include <cryptopp/asn.h>
#include <cryptopp/base64.h>
#include <cryptopp/crc.h>
#include <cryptopp/zinflate.h>
#include "I2PEndian.h"
#include "Reseed.h"
#include "Log.h"
#include "Identity.h"
#include "CryptoConst.h"
#include "NetDb.h"
#include "util.h"


namespace i2p
{
namespace data
{

	static std::vector<std::string> httpReseedHostList = {
				// "http://193.150.121.66/netDb/",  // unstable
				// "http://us.reseed.i2p2.no/",     // misconfigured, not serving reseed data
				// "http://jp.reseed.i2p2.no/",     // Really outdated RIs
				"http://netdb.i2p2.no/",            // only SU3 (v2) support
				"http://i2p.mooo.com/netDb/",
				"http://uk.reseed.i2p2.no/",
				"http://i2p-netdb.innovatio.no/"
			};

	//TODO: Remember to add custom port support. Not all serves on 443
	static std::vector<std::string> httpsReseedHostList = {
				// "https://193.150.121.66/netDb/",  // unstable
				// "https://i2p-netdb.innovatio.no/",// Vuln to POODLE
				"https://netdb.i2p2.no/",            // Only SU3 (v2) support
				"https://reseed.i2p-projekt.de/",    // Only HTTPS
				"https://cowpuncher.drollette.com/netdb/",  // Only HTTPS and SU3 (v2) support -- will move to a new location
				"https://i2p.mooo.com/netDb/",
				"https://link.mx24.eu/",             // Only HTTPS and SU3 (v2) support
				"https://i2pseed.zarrenspry.info/",  // Only HTTPS and SU3 (v2) support
				"https://ieb9oopo.mooo.com/"         // Only HTTPS and SU3 (v2) support
			};
	
	//TODO: Implement v2 reseeding. Lightweight zip library is needed.
	//TODO: Implement SU3, utils.
	Reseeder::Reseeder()
	{
	}

	Reseeder::~Reseeder()
	{
	}

	bool Reseeder::reseedNow()
	{
		try
		{
			// Seems like the best place to try to intercept with SSL
			/*ssl_server = true;
			try {
				// SSL
			}
			catch (std::exception& e)
			{
				LogPrint("Exception in SSL: ", e.what());
			}*/
			std::string reseedHost = httpReseedHostList[(rand() % httpReseedHostList.size())];
			LogPrint("Reseeding from ", reseedHost);
			std::string content = i2p::util::http::httpRequest(reseedHost);
			if (content == "")
			{
				LogPrint("Reseed failed");
				return false;
			}
			boost::regex e("<\\s*A\\s+[^>]*href\\s*=\\s*\"([^\"]*)\"", boost::regex::normal | boost::regbase::icase);
			boost::sregex_token_iterator i(content.begin(), content.end(), e, 1);
			boost::sregex_token_iterator j;
			//TODO: Ugly code, try to clean up.
			//TODO: Try to reduce N number of variables
			std::string name;
			std::string routerInfo;
			std::string tmpUrl;
			std::string filename;
			std::string ignoreFileSuffix = ".su3";
			boost::filesystem::path root = i2p::util::filesystem::GetDataDir();
			while (i != j)
			{
				name = *i++;
				if (name.find(ignoreFileSuffix)!=std::string::npos)
					continue;
				LogPrint("Downloading ", name);
				tmpUrl = reseedHost;
				tmpUrl.append(name);
				routerInfo = i2p::util::http::httpRequest(tmpUrl);
				if (routerInfo.size()==0)
					continue;
				filename = root.string();
#ifndef _WIN32
				filename += "/netDb/r";
#else
				filename += "\\netDb\\r";
#endif
				filename += name.at(11); // first char in id
#ifndef _WIN32
				filename.append("/");
#else
				filename.append("\\");
#endif
				filename.append(name.c_str());
				std::ofstream outfile (filename, std::ios::binary);
				outfile << routerInfo;
				outfile.close();
			}
			return true;
		}
		catch (std::exception& ex)
		{
			//TODO: error reporting
			return false;
		}
		return false;
	}	

	int Reseeder::ReseedNowSU3 ()
	{
		CryptoPP::AutoSeededRandomPool rnd;
		auto ind = rnd.GenerateWord32 (0, httpReseedHostList.size() - 1);
		std::string reseedHost = httpReseedHostList[ind];
		return ReseedFromSU3 (reseedHost);
	}

	int Reseeder::ReseedFromSU3 (const std::string& host)
	{
		std::string url = host + "i2pseeds.su3";
		LogPrint (eLogInfo, "Dowloading SU3 from ", host);
		std::string su3 = i2p::util::http::httpRequest (url);
		if (su3.length () > 0)
		{
			std::stringstream s(su3);
			return ProcessSU3Stream (s);
		}
		else
		{
			LogPrint (eLogWarning, "SU3 download failed");
			return 0;
		}
	}
	
	int Reseeder::ProcessSU3File (const char * filename)
	{
		std::ifstream s(filename, std::ifstream::binary);
		if (s.is_open ())	
			return ProcessSU3Stream (s);
		else
		{
			LogPrint (eLogError, "Can't open file ", filename);
			return 0;
		}
	}

	const char SU3_MAGIC_NUMBER[]="I2Psu3";	
	const uint32_t ZIP_HEADER_SIGNATURE = 0x04034B50;
	const uint32_t ZIP_CENTRAL_DIRECTORY_HEADER_SIGNATURE = 0x02014B50;	
	const uint16_t ZIP_BIT_FLAG_DATA_DESCRIPTOR = 0x0008;	
	int Reseeder::ProcessSU3Stream (std::istream& s)
	{
		char magicNumber[7];
		s.read (magicNumber, 7); // magic number and zero byte 6
		if (strcmp (magicNumber, SU3_MAGIC_NUMBER))
		{
			LogPrint (eLogError, "Unexpected SU3 magic number");	
			return 0;
		}			
		s.seekg (1, std::ios::cur); // su3 file format version
		SigningKeyType signatureType;
		s.read ((char *)&signatureType, 2);  // signature type
		signatureType = be16toh (signatureType);
		uint16_t signatureLength;
		s.read ((char *)&signatureLength, 2);  // signature length
		signatureLength = be16toh (signatureLength);
		s.seekg (1, std::ios::cur); // unused
		uint8_t versionLength;
		s.read ((char *)&versionLength, 1);  // version length	
		s.seekg (1, std::ios::cur); // unused
		uint8_t signerIDLength;
		s.read ((char *)&signerIDLength, 1);  // signer ID length	
		uint64_t contentLength;
		s.read ((char *)&contentLength, 8);  // content length	
		contentLength = be64toh (contentLength);
		s.seekg (1, std::ios::cur); // unused
		uint8_t fileType;
		s.read ((char *)&fileType, 1);  // file type	
		if (fileType != 0x00) //  zip file
		{
			LogPrint (eLogError, "Can't handle file type ", (int)fileType);	
			return 0;
		}
		s.seekg (1, std::ios::cur); // unused
		uint8_t contentType;
		s.read ((char *)&contentType, 1);  // content type	
		if (contentType != 0x03) // reseed data
		{
			LogPrint (eLogError, "Unexpected content type ", (int)contentType);	
			return 0;
		}
		s.seekg (12, std::ios::cur); // unused

		s.seekg (versionLength, std::ios::cur); // skip version
		char signerID[256];
		s.read (signerID, signerIDLength); // signerID
		signerID[signerIDLength] = 0;
		
		//try to verify signature
		auto it = m_SigningKeys.find (signerID);
		if (it != m_SigningKeys.end ())
		{
			// TODO: implement all signature types
			if (signatureType == SIGNING_KEY_TYPE_RSA_SHA512_4096)
			{
				size_t pos = s.tellg ();
				size_t tbsLen = pos + contentLength;
				uint8_t * tbs = new uint8_t[tbsLen];
				s.seekg (0, std::ios::beg);
				s.read ((char *)tbs, tbsLen);
				uint8_t * signature = new uint8_t[signatureLength];
				s.read ((char *)signature, signatureLength);
				// RSA-raw
				i2p::crypto::RSASHA5124096RawVerifier verifier(it->second);
				verifier.Update (tbs, tbsLen);
				if (!verifier.Verify (signature))
					LogPrint (eLogWarning, "SU3 signature verification failed");
				delete[] signature;
				delete[] tbs;
				s.seekg (pos, std::ios::beg);
			}
			else
				LogPrint (eLogWarning, "Signature type ", signatureType, " is not supported");
		}
		else
			LogPrint (eLogWarning, "Certificate for ", signerID, " not loaded");
		
		// handle content
		int numFiles = 0;
		size_t contentPos = s.tellg ();
		while (!s.eof ())
		{	
			uint32_t signature;
			s.read ((char *)&signature, 4);
			signature = le32toh (signature);
			if (signature == ZIP_HEADER_SIGNATURE)
			{
				// next local file
				s.seekg (2, std::ios::cur); // version
				uint16_t bitFlag;
				s.read ((char *)&bitFlag, 2);	
				bitFlag = le16toh (bitFlag);
				uint16_t compressionMethod;
				s.read ((char *)&compressionMethod, 2);	
				compressionMethod = le16toh (compressionMethod);
				s.seekg (4, std::ios::cur); // skip fields we don't care about
				uint32_t compressedSize, uncompressedSize; 
				uint8_t crc32[4];
				s.read ((char *)crc32, 4);	
				s.read ((char *)&compressedSize, 4);	
				compressedSize = le32toh (compressedSize);	
				s.read ((char *)&uncompressedSize, 4);
				uncompressedSize = le32toh (uncompressedSize);	
				uint16_t fileNameLength, extraFieldLength; 
				s.read ((char *)&fileNameLength, 2);	
				fileNameLength = le16toh (fileNameLength);
				s.read ((char *)&extraFieldLength, 2);
				extraFieldLength = le16toh (extraFieldLength);
				char localFileName[255];
				s.read (localFileName, fileNameLength);
				localFileName[fileNameLength] = 0;
				s.seekg (extraFieldLength, std::ios::cur);
				// take care about data desriptor if presented
				if (bitFlag & ZIP_BIT_FLAG_DATA_DESCRIPTOR)
				{
					size_t pos = s.tellg ();
					if (!FindZipDataDescriptor (s))
					{
						LogPrint (eLogError, "SU3 archive data descriptor not found");
						return numFiles;
					}								
	
					s.read ((char *)crc32, 4);	
					s.read ((char *)&compressedSize, 4);	
					compressedSize = le32toh (compressedSize) + 4; // ??? we must consider signature as part of compressed data
					s.read ((char *)&uncompressedSize, 4);
					uncompressedSize = le32toh (uncompressedSize);	

					// now we know compressed and uncompressed size
					s.seekg (pos, std::ios::beg); // back to compressed data
				}

				LogPrint (eLogDebug, "Proccessing file ", localFileName, " ", compressedSize, " bytes");
				if (!compressedSize)
				{
					LogPrint (eLogWarning, "Unexpected size 0. Skipped");
					continue;
				}	
				
				uint8_t * compressed = new uint8_t[compressedSize];
				s.read ((char *)compressed, compressedSize);
				if (compressionMethod) // we assume Deflate
				{
					CryptoPP::Inflator decompressor;
					decompressor.Put (compressed, compressedSize);	
					decompressor.MessageEnd();
					if (decompressor.MaxRetrievable () <= uncompressedSize)
					{
						uint8_t * uncompressed = new uint8_t[uncompressedSize];	
						decompressor.Get (uncompressed, uncompressedSize);	
						if (CryptoPP::CRC32().VerifyDigest (crc32, uncompressed, uncompressedSize))
						{
							i2p::data::netdb.AddRouterInfo (uncompressed, uncompressedSize);
							numFiles++;
						}
						else
							LogPrint (eLogError, "CRC32 verification failed");
						delete[] uncompressed;
					}
					else
						LogPrint (eLogError, "Actual uncompressed size ", decompressor.MaxRetrievable (), " exceed ", uncompressedSize, " from header");
				}	
				else // no compression
				{
					i2p::data::netdb.AddRouterInfo (compressed, compressedSize);
					numFiles++;
				}	
				delete[] compressed;
				if (bitFlag & ZIP_BIT_FLAG_DATA_DESCRIPTOR)
					s.seekg (12, std::ios::cur); // skip data descriptor section if presented (12 = 16 - 4)
			}
			else
			{
				if (signature != ZIP_CENTRAL_DIRECTORY_HEADER_SIGNATURE)
					LogPrint (eLogWarning, "Missing zip central directory header");
				break; // no more files
			}
			size_t end = s.tellg ();
			if (end - contentPos >= contentLength)
				break; // we are beyond contentLength
		}
		return numFiles;
	}

	const uint8_t ZIP_DATA_DESCRIPTOR_SIGNATURE[] = { 0x50, 0x4B, 0x07, 0x08 };	
	bool Reseeder::FindZipDataDescriptor (std::istream& s)
	{
		size_t nextInd = 0;	
		while (!s.eof ())
		{
			uint8_t nextByte;
			s.read ((char *)&nextByte, 1);
			if (nextByte == ZIP_DATA_DESCRIPTOR_SIGNATURE[nextInd])	
			{
				nextInd++;
				if (nextInd >= sizeof (ZIP_DATA_DESCRIPTOR_SIGNATURE))
					return true;
			}
			else
				nextInd = 0;
		}
		return false;
	}

	const char CERTIFICATE_HEADER[] = "-----BEGIN CERTIFICATE-----";
	const char CERTIFICATE_FOOTER[] = "-----END CERTIFICATE-----";
	void Reseeder::LoadCertificate (const std::string& filename)
	{
		std::ifstream s(filename, std::ifstream::binary);
		if (s.is_open ())	
		{
			s.seekg (0, std::ios::end);
			size_t len = s.tellg ();
			s.seekg (0, std::ios::beg);
			char buf[2048];
			s.read (buf, len);
			std::string cert (buf, len);
			// assume file in pem format
			auto pos1 = cert.find (CERTIFICATE_HEADER);	
			auto pos2 = cert.find (CERTIFICATE_FOOTER);	
			if (pos1 == std::string::npos || pos2 == std::string::npos)
			{
				LogPrint (eLogError, "Malformed certificate file");
				return;
			}	
			pos1 += strlen (CERTIFICATE_HEADER);
			pos2 -= pos1;
			std::string base64 = cert.substr (pos1, pos2);

			CryptoPP::ByteQueue queue;
			CryptoPP::Base64Decoder decoder; // regular base64 rather than I2P 
			decoder.Attach (new CryptoPP::Redirector (queue));
			decoder.Put ((const uint8_t *)base64.data(), base64.length());
			decoder.MessageEnd ();
			
			LoadCertificate (queue);
		}
		else
			LogPrint (eLogError, "Can't open certificate file ", filename);
	}

	std::string Reseeder::LoadCertificate (CryptoPP::ByteQueue& queue)
	{
		// extract X.509
		CryptoPP::BERSequenceDecoder x509Cert (queue);
		CryptoPP::BERSequenceDecoder tbsCert (x509Cert);
		// version
		uint32_t ver;
		CryptoPP::BERGeneralDecoder context (tbsCert, CryptoPP::CONTEXT_SPECIFIC | CryptoPP::CONSTRUCTED);
		CryptoPP::BERDecodeUnsigned<uint32_t>(context, ver, CryptoPP::INTEGER);
		// serial
		CryptoPP::Integer serial;
   		serial.BERDecode(tbsCert);	
		// signature
		CryptoPP::BERSequenceDecoder signature (tbsCert);
   		signature.SkipAll();
		
		// issuer
		std::string name;
		CryptoPP::BERSequenceDecoder issuer (tbsCert);
		{
			CryptoPP::BERSetDecoder c (issuer);	c.SkipAll();
			CryptoPP::BERSetDecoder st (issuer); st.SkipAll();
			CryptoPP::BERSetDecoder l (issuer); l.SkipAll();
			CryptoPP::BERSetDecoder o (issuer); o.SkipAll();
			CryptoPP::BERSetDecoder ou (issuer); ou.SkipAll();
			CryptoPP::BERSetDecoder cn (issuer);
			{		
				CryptoPP::BERSequenceDecoder attributes (cn);
				{			
					CryptoPP::BERGeneralDecoder ident(attributes, CryptoPP::OBJECT_IDENTIFIER);
					ident.SkipAll ();
					CryptoPP::BERDecodeTextString (attributes, name, CryptoPP::UTF8_STRING);
				}	
			}	
		}	
   		issuer.SkipAll();
		// validity
		CryptoPP::BERSequenceDecoder validity (tbsCert);
   		validity.SkipAll();
		// subject
		CryptoPP::BERSequenceDecoder subject (tbsCert);
   		subject.SkipAll();
		// public key
		CryptoPP::BERSequenceDecoder publicKey (tbsCert);
		{			
			CryptoPP::BERSequenceDecoder ident (publicKey);
			ident.SkipAll ();
			CryptoPP::BERGeneralDecoder key (publicKey, CryptoPP::BIT_STRING);
			key.Skip (1); // FIXME: probably bug in crypto++
			CryptoPP::BERSequenceDecoder keyPair (key);
			CryptoPP::Integer n;
   			n.BERDecode (keyPair);
			if (name.length () > 0) 
			{	
				PublicKey value;
				n.Encode (value, 512);
				m_SigningKeys[name] = value;
			}		
			else
				LogPrint (eLogWarning, "Unknown issuer. Skipped");
		}	
   		publicKey.SkipAll();
		
		tbsCert.SkipAll();
		x509Cert.SkipAll();
		return name;
	}	
	
	void Reseeder::LoadCertificates ()
	{
		boost::filesystem::path reseedDir = i2p::util::filesystem::GetCertificatesDir() / "reseed";
		
		if (!boost::filesystem::exists (reseedDir))
		{
			LogPrint (eLogWarning, "Reseed certificates not loaded. ", reseedDir, " doesn't exist");
			return;
		}

		int numCertificates = 0;
		boost::filesystem::directory_iterator end; // empty
		for (boost::filesystem::directory_iterator it (reseedDir); it != end; ++it)
		{
			if (boost::filesystem::is_regular_file (it->status()) && it->path ().extension () == ".crt")
			{	
				LoadCertificate (it->path ().string ());
				numCertificates++;
			}	
		}	
		LogPrint (eLogInfo, numCertificates, " certificates loaded");
	}	

	std::string Reseeder::HttpsRequest (const std::string& address)
	{
		static uint8_t clientHello[] = 
		{
			0x16, // handshake
			0x03, 0x02, // version (TSL 1.2)
			0x00, 0x2F, // length of handshake
			// handshake
			0x01, // handshake type (client hello)
			0x00, 0x00, 0x2B, // length of handshake payload 
			// client hello
			0x03, 0x02, // highest version supported (TSL 1.2)
			0x01, 0x01, 0x01, 0x01, // date, can be anything
			0x74, 0x55, 0x18, 0x36, 0x42, 0x05, 0xC1, 0xDD, 0x4A, 0x21, 0x80, 0x80, 0xEC, 0x37,
			0x11, 0x93, 0x16, 0xF4, 0x66, 0x00, 0x12, 0x67, 0xAB, 0xBA, 0xFF, 0x29, 0x13, 0x9E, // 28 random bytes
			0x00, // session id length
			0x00, 0x04, // chiper suites length
			0x00, 0x00, // NULL_WITH_NULL_NULL
			0x00, 0x35, // RSA_WITH_AES_256_CBC_SHA
			0x01, // compression methods length
			0x00  // no compression
		};	

		static uint8_t clientKeyExchange[] =
		{
			0x16, // handshake
			0x03, 0x02, // version (TSL 1.2)
			0x02, 0x04, // length of handshake
			// handshake
			0x10, // handshake type (client key exchange)
			0x00, 0x02, 0x00, // length of handshake payload 
			// client key exchange RSA
			// 512 RSA encrypted 48 bytes ( 2 bytes version + 46 random bytes)
		};	
		
		i2p::util::http::url u(address);
		boost::asio::ip::tcp::iostream site;
		site.connect(u.host_, "443");
		if (site.good ())
		{
			// send ClientHello
			site.write ((char *)clientHello, sizeof (clientHello));
			// read ServerHello
			uint8_t type;
			site.read ((char *)&type, 1);
			uint16_t version;
			site.read ((char *)&version, 2);
			uint16_t length;
			site.read ((char *)&length, 2);
			length = be16toh (length);
			char * serverHello = new char[length];
			site.read (serverHello, length);
			uint8_t serverRandom[32];
			if (serverHello[0] == 0x02) // handshake type server hello
				memcpy (serverRandom, serverHello + 6, 32);
			else
				LogPrint (eLogError, "Unexpected handshake type ", (int)serverHello[0]);
			delete[] serverHello;
			// read Certificate
			site.read ((char *)&type, 1);
			site.read ((char *)&version, 2);
			site.read ((char *)&length, 2);
			length = be16toh (length);
			char * certificate = new char[length];
			site.read (certificate, length);
			CryptoPP::RSA::PublicKey publicKey;
			// 0 - handshake type
			// 1 - 3 - handshake payload length
			// 4 - 6 - length of array of certificates
			// 7 - 9 - length of certificate
			if (certificate[0] == 0x0B) // handshake type certificate
			{
				CryptoPP::ByteQueue queue;
				queue.Put ((uint8_t *)certificate + 10, length - 10);	
				queue.MessageEnd ();
				auto issuer = LoadCertificate (queue);
				auto it = m_SigningKeys.find (issuer);
				if (it != m_SigningKeys.end ())
					publicKey.Initialize (CryptoPP::Integer (it->second, 512), CryptoPP::Integer (i2p::crypto::rsae));
				else
					LogPrint (eLogError, "Can't find public key for ", issuer);
			}	
			else
				LogPrint (eLogError, "Unexpected handshake type ", (int)certificate[0]);
			delete[] certificate;
			// read ServerHelloDone
			site.read ((char *)&type, 1);
			site.read ((char *)&version, 2);
			site.read ((char *)&length, 2);
			length = be16toh (length);
			char * serverHelloDone = new char[length];
			site.read (serverHelloDone, length);
			if (serverHelloDone[0] != 0x0E) // handshake type hello done
				LogPrint (eLogError, "Unexpected handshake type ", (int)serverHelloDone[0]);
			delete[] serverHelloDone;
			// our turn now
			// generate secret key
			CryptoPP::AutoSeededRandomPool rnd;
			CryptoPP::RSAES_PKCS1v15_Encryptor encryptor(publicKey);
			// encryptor.CiphertextLength (48);
			uint8_t secret[48], encrypted[512];
			secret[0] = clientKeyExchange[1]; secret[1] = clientKeyExchange[2]; // version
			rnd.GenerateBlock (secret + 2, 46); // 46 random bytes
			encryptor.Encrypt (rnd, secret, 48, encrypted);
			// send ClientKeyExchange
			site.write ((char *)clientKeyExchange, sizeof (clientKeyExchange));
			site.write ((char *)encrypted, 512);
			uint8_t masterSecret[48], random[64];
			memcpy (random, clientHello + 11, 32);
			memcpy (random + 32, serverRandom, 32);
			PRF (secret, "master secret", random, 48, masterSecret);
		}
		else
			LogPrint (eLogError, "Can't connect to ", address);
		return "";
	}	
	
	void Reseeder::PRF (const uint8_t * secret, const char * label, const uint8_t * random, size_t len, uint8_t * buf)
	{
		// secret is assumed 48 bytes	
		// random is 64 bytes
		// output is 48 bytes (buffer size should be 64)
 		CryptoPP::HMAC<CryptoPP::SHA256> hmac (secret, 48);	
		uint8_t seed[96]; size_t seedLen;
		seedLen = strlen (label);	
		memcpy (seed, label, seedLen);
		memcpy (seed + seedLen, random, 64);
		seedLen += 64;

		size_t offset = 0;
		uint8_t a[128];
		hmac.CalculateDigest (a, seed, seedLen);
		while (offset < len)
		{
			memcpy (a + 32, seed, seedLen);
			hmac.CalculateDigest (buf + offset, a, seedLen + 32);
			offset += 32;
			hmac.CalculateDigest (a, a, 32);
		}
	}

}
}