#include <string>
#include <vector>

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>

#include <gnutls/gnutls.h>

#include "users.h"
#include "channels.h"
#include "modules.h"
#include "helperfuncs.h"
#include "socket.h"
#include "hashcomp.h"

/* $ModDesc: Provides SSL support for clients */
/* $CompileFlags: `libgnutls-config --cflags` */
/* $LinkerFlags: -L/usr/local/lib -Wl,--rpath -Wl,/usr/local/lib -L/usr/lib -Wl,--rpath -Wl,/usr/lib -lgnutls */

enum issl_status { ISSL_NONE, ISSL_HANDSHAKING_READ, ISSL_HANDSHAKING_WRITE, ISSL_HANDSHAKEN, ISSL_CLOSING, ISSL_CLOSED };

class issl_session
{
public:
	gnutls_session_t sess;
	issl_status status;
	std::string outbuf;
	int inbufoffset;
	char* inbuf;
	int fd;
};

class ModuleSSL : public Module
{
	Server* Srv;
	ServerConfig* SrvConf;
	ConfigReader* Conf;
	
	std::vector<int> listenports;
	
	int inbufsize;
	issl_session sessions[MAX_DESCRIPTORS];
	
	gnutls_certificate_credentials x509_cred;
	gnutls_dh_params dh_params;
	
	std::string keyfile;
	std::string certfile;
	std::string cafile;
	std::string crlfile;
	int dh_bits;
	
 public:
	
	ModuleSSL(Server* Me)
		: Module::Module(Me)
	{
		Srv = Me;
		SrvConf = Srv->GetConfig();
		Conf = new ConfigReader;
		
		// Not rehashable...because I cba to reduce all the sizes of existing buffers.
		inbufsize = SrvConf->NetBufferSize;
		
		gnutls_global_init(); // This must be called once in the program

		if(gnutls_certificate_allocate_credentials(&x509_cred) != 0)
			log(DEFAULT, "m_ssl_gnutls.so: Failed to allocate certificate credentials");

		// Guessing return meaning
		if(gnutls_dh_params_init(&dh_params) < 0)
			log(DEFAULT, "m_ssl_gnutls.so: Failed to initialise DH parameters");

		OnRehash("");

		// Void return, guess we assume success
		gnutls_certificate_set_dh_params(x509_cred, dh_params);
	}
	
	virtual void OnRehash(std::string param)
	{
		delete Conf;
		Conf = new ConfigReader;
		
		for(unsigned int i = 0; i < listenports.size(); i++)
		{
			SrvConf->DelIOHook(listenports[i]);
		}
		
		listenports.clear();
		
		for(int i = 0; i < Conf->Enumerate("bind"); i++)
		{
			// For each <bind> tag
			if(((Conf->ReadValue("bind", "type", i) == "") || (Conf->ReadValue("bind", "type", i) == "clients")) && (Conf->ReadValue("bind", "ssl", i) == "gnutls"))
			{
				// Get the port we're meant to be listening on with SSL
				unsigned int port = Conf->ReadInteger("bind", "port", i, true);
				SrvConf->AddIOHook(port, this);
				
				// We keep a record of which ports we're listening on with SSL
				listenports.push_back(port);
				
				log(DEFAULT, "m_ssl_gnutls.so: Enabling SSL for port %d", port);
			}
		}
		
		cafile	= Conf->ReadValue("gnutls", "cafile", 0);
		crlfile	= Conf->ReadValue("gnutls", "crlfile", 0);
		certfile	= Conf->ReadValue("gnutls", "certfile", 0);
		keyfile	= Conf->ReadValue("gnutls", "keyfile", 0);
		dh_bits	= Conf->ReadInteger("gnutls", "dhbits", 0, false);
		
		if(cafile == "")
			cafile = "conf/ca.pem";
			
		if(crlfile == "")
			crlfile = "conf/crl.pem";
			
		if(certfile == "")
			certfile = "conf/cert.pem";
			
		if(keyfile == "")
			keyfile = "conf/key.pem";
			
		if((dh_bits != 768) && (dh_bits != 1024) && (dh_bits != 2048) && (dh_bits != 3072) && (dh_bits != 4096))
			dh_bits = 1024;
		
		if(gnutls_certificate_set_x509_trust_file(x509_cred, cafile.c_str(), GNUTLS_X509_FMT_PEM) < 0)
			log(DEFAULT, "m_ssl_gnutls.so: Failed to set X.509 trust file: %s", cafile.c_str());
			
		if(gnutls_certificate_set_x509_crl_file (x509_cred, crlfile.c_str(), GNUTLS_X509_FMT_PEM) < 0)
			log(DEFAULT, "m_ssl_gnutls.so: Failed to set X.509 CRL file: %s", crlfile.c_str());
		
		// Guessing on the return value of this, manual doesn't say :|
		if(gnutls_certificate_set_x509_key_file (x509_cred, certfile.c_str(), keyfile.c_str(), GNUTLS_X509_FMT_PEM) < 0)
			log(DEFAULT, "m_ssl_gnutls.so: Failed to set X.509 certificate and key files: %s and %s", certfile.c_str(), keyfile.c_str());	
			
 		// Generate Diffie Hellman parameters - for use with DHE
		// kx algorithms. These should be discarded and regenerated
		// once a day, once a week or once a month. Depending on the
		// security requirements.
		
		if(gnutls_dh_params_generate2(dh_params, dh_bits) < 0)
			log(DEFAULT, "m_ssl_gnutls.so: Failed to generate DH parameters (%d bits)", dh_bits);
	}
	
	virtual ~ModuleSSL()
	{
		delete Conf;
		gnutls_dh_params_deinit(dh_params);
		gnutls_certificate_free_credentials(x509_cred);
		gnutls_global_deinit();
	}
	
	virtual Version GetVersion()
	{
		return Version(1, 0, 0, 0, VF_STATIC | VF_VENDOR);
	}

	void Implements(char* List)
	{
		List[I_OnRawSocketAccept] = List[I_OnRawSocketClose] = List[I_OnRawSocketRead] = List[I_OnRawSocketWrite] = 1;
		List[I_OnSyncUserMetaData] = List[I_OnDecodeMetaData] = List[I_OnUserQuit] = List[I_OnRehash] = List[I_OnWhois] = 1;
	}

	virtual void OnRawSocketAccept(int fd, std::string ip, int localport)
	{
		issl_session* session = &sessions[fd];
	
		session->fd = fd;
		session->inbuf = new char[inbufsize];
		session->inbufoffset = 0;
	
		gnutls_init(&session->sess, GNUTLS_SERVER);

		gnutls_set_default_priority(session->sess); // Avoid calling all the priority functions, defaults are adequate.
		gnutls_credentials_set(session->sess, GNUTLS_CRD_CERTIFICATE, x509_cred);
		gnutls_certificate_server_set_request(session->sess, GNUTLS_CERT_REQUEST); // Request client certificate if any.
		gnutls_dh_set_prime_bits(session->sess, dh_bits);
		gnutls_transport_set_ptr(session->sess, (gnutls_transport_ptr_t) fd); // Give gnutls the fd for the socket.
		
		Handshake(session);
	}

	virtual void OnRawSocketClose(int fd)
	{
		CloseSession(&sessions[fd]);
	}
	
	virtual int OnRawSocketRead(int fd, char* buffer, unsigned int count, int &readresult)
	{
		issl_session* session = &sessions[fd];
		
		if(!session->sess)
		{
			log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead: No session to read from");
			readresult = 0;
			CloseSession(session);
			return 1;
		}
		
		log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead(%d, buffer, %u, %d)", fd, count, readresult);
		
		if(session->status == ISSL_HANDSHAKING_READ)
		{
			// The handshake isn't finished, try to finish it.
			
			if(Handshake(session))
			{
				// Handshake successfully resumed.
				log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead: successfully resumed handshake");
			}
			else
			{
				// Couldn't resume handshake.	
				log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead: failed to resume handshake");
				return -1;
			}
		}
		else if(session->status == ISSL_HANDSHAKING_WRITE)
		{
			log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead: handshake wants to write data but we are currently reading");
			return -1;
		}
		
		// If we resumed the handshake then session->status will be ISSL_HANDSHAKEN.
		
		if(session->status == ISSL_HANDSHAKEN)
		{
			// Is this right? Not sure if the unencrypted data is garaunteed to be the same length.
			// Read into the inbuffer, offset from the beginning by the amount of data we have that insp hasn't taken yet.
			log(DEBUG, "m_ssl_gnutls.so: gnutls_record_recv(sess, inbuf+%d, %d-%d)", session->inbufoffset, inbufsize, session->inbufoffset);
			
			int ret = gnutls_record_recv(session->sess, session->inbuf + session->inbufoffset, inbufsize - session->inbufoffset);

			if(ret == 0)
			{
				// Client closed connection.
				log(DEBUG, "m_ssl_gnutls.so: Client closed the connection");
				readresult = 0;
				CloseSession(session);
				return 1;
			}
			else if(ret < 0)
			{
				if(ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED)
				{
					log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead: Not all SSL data read: %s", gnutls_strerror(ret));
					return -1;
				}
				else
				{
					log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead: Error reading SSL data: %s", gnutls_strerror(ret));
					readresult = 0;
					CloseSession(session);
				}
			}
			else
			{
				// Read successfully 'ret' bytes into inbuf + inbufoffset
				// There are 'ret' + 'inbufoffset' bytes of data in 'inbuf'
				// 'buffer' is 'count' long
				
				unsigned int length = ret + session->inbufoffset;
		
				log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead: Read %d bytes, now have %d waiting to be passed up", ret, length);
						
				if(count <= length)
				{
					memcpy(buffer, session->inbuf, count);
					// Move the stuff left in inbuf to the beginning of it
					memcpy(session->inbuf, session->inbuf + count, (length - count));
					// Now we need to set session->inbufoffset to the amount of data still waiting to be handed to insp.
					session->inbufoffset = length - count;
					// Insp uses readresult as the count of how much data there is in buffer, so:
					readresult = count;
				}
				else
				{
					// There's not as much in the inbuf as there is space in the buffer, so just copy the whole thing.
					memcpy(buffer, session->inbuf, length);
					// Zero the offset, as there's nothing there..
					session->inbufoffset = 0;
					// As above
					readresult = length;
				}
			
				log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead: Passing %d bytes up to insp:");
				Srv->Log(DEBUG, std::string(buffer, readresult));
			}
		}
		else if(session->status == ISSL_CLOSING)
		{
			log(DEBUG, "m_ssl_gnutls.so: OnRawSocketRead: session closing...");
			readresult = 0;
		}
		
		return 1;
	}
	
	virtual int OnRawSocketWrite(int fd, char* buffer, int count)
	{		
		issl_session* session = &sessions[fd];
		const char* sendbuffer = buffer;

		if(!session->sess)
		{
			log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: No session to write to");
			CloseSession(session);
			return 1;
		}
		
		if(session->status == ISSL_HANDSHAKING_WRITE)
		{
			// The handshake isn't finished, try to finish it.
			
			if(Handshake(session))
			{
				// Handshake successfully resumed.
				log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: successfully resumed handshake");
			}
			else
			{
				// Couldn't resume handshake.	
				log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: failed to resume handshake"); 
			}
		}
		else if(session->status == ISSL_HANDSHAKING_READ)
		{
			log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: handshake wants to read data but we are currently writing");
		}

		log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: Adding %d bytes to the outgoing buffer", count);		
		session->outbuf.append(sendbuffer, count);
		sendbuffer = session->outbuf.c_str();
		count = session->outbuf.size();

		if(session->status == ISSL_HANDSHAKEN)
		{
			log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: Trying to write %d bytes:", count);
			Srv->Log(DEBUG, session->outbuf);
			
			int ret = gnutls_record_send(session->sess, sendbuffer, count);
		
			if(ret == 0)
			{
				log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: Client closed the connection");
				CloseSession(session);
			}
			else if(ret < 0)
			{
				if(ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED)
				{
					log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: Not all SSL data written: %s", gnutls_strerror(ret));
				}
				else
				{
					log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: Error writing SSL data: %s", gnutls_strerror(ret));
					CloseSession(session);					
				}
			}
			else
			{
				log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: Successfully wrote %d bytes", ret);
				session->outbuf = session->outbuf.substr(ret);
			}
		}
		else if(session->status == ISSL_CLOSING)
		{
			log(DEBUG, "m_ssl_gnutls.so: OnRawSocketWrite: session closing...");
		}
		
		return 1;
	}

	virtual void OnUserQuit(userrec* user, std::string reason)
	{
		CloseSession(&sessions[user->fd]);
	}
	
	// :kenny.chatspike.net 320 Om Epy|AFK :is a Secure Connection
	virtual void OnWhois(userrec* source, userrec* dest)
	{
		if(dest->GetExt("ssl"))
		{
			WriteServ(source->fd, "320 %s %s :is a Secure Connection", source->nick, dest->nick);
		}
	}
	
	virtual void OnSyncUserMetaData(userrec* user, Module* proto, void* opaque, std::string extname)
	{
		// check if the linking module wants to know about OUR metadata
		if(extname == "ssl")
		{
			// check if this user has an swhois field to send
			if(user->GetExt(extname))
			{
				// call this function in the linking module, let it format the data how it
				// sees fit, and send it on its way. We dont need or want to know how.
				proto->ProtoSendMetaData(opaque, TYPE_USER, user, extname, "ON");
			}
		}
	}
	
	virtual void OnDecodeMetaData(int target_type, void* target, std::string extname, std::string extdata)
	{
		// check if its our metadata key, and its associated with a user
		if ((target_type == TYPE_USER) && (extname == "ssl"))
		{
			userrec* dest = (userrec*)target;
			// if they dont already have an ssl flag, accept the remote server's
			if (!dest->GetExt(extname))
			{
				dest->Extend(extname, "ON");
			}
		}
	}
	
	bool Handshake(issl_session* session)
	{		
		int ret = gnutls_handshake(session->sess);
      
      if(ret < 0)
		{
			if(ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED)
			{
				// Handshake needs resuming later, read() or write() would have blocked.
				
				if(gnutls_record_get_direction(session->sess) == 0)
				{
					// gnutls_handshake() wants to read() again.
					session->status = ISSL_HANDSHAKING_READ;
					log(DEBUG, "m_ssl_gnutls.so: Handshake needs resuming (reading) later, error string: %s", gnutls_strerror(ret));
				}
				else
				{
					// gnutls_handshake() wants to write() again.
					session->status = ISSL_HANDSHAKING_WRITE;
					log(DEBUG, "m_ssl_gnutls.so: Handshake needs resuming (writing) later, error string: %s", gnutls_strerror(ret));
					MakePollWrite(session);	
				}
			}
			else
			{
				// Handshake failed.
				CloseSession(session);
			   log(DEBUG, "m_ssl_gnutls.so: Handshake failed, error string: %s", gnutls_strerror(ret));
			   session->status = ISSL_CLOSING;
			}
			
			return false;
		}
		else
		{
			// Handshake complete.
			log(DEBUG, "m_ssl_gnutls.so: Handshake completed");
			
			// This will do for setting the ssl flag...it could be done earlier if it's needed. But this seems neater.
			Srv->FindDescriptor(session->fd)->Extend("ssl", "ON");
			
			session->status = ISSL_HANDSHAKEN;
			
			MakePollWrite(session);
			
			return true;
		}
	}
	
	void MakePollWrite(issl_session* session)
	{
		OnRawSocketWrite(session->fd, NULL, 0);
	}
	
	void CloseSession(issl_session* session)
	{
		if(session->sess)
		{
			gnutls_bye(session->sess, GNUTLS_SHUT_WR);
			gnutls_deinit(session->sess);
		}
		
		if(session->inbuf)
		{
			delete[] session->inbuf;
		}
		
		session->outbuf.clear();
		session->inbuf = NULL;
		session->sess = NULL;
		session->status = ISSL_NONE;
	}
};

class ModuleSSLFactory : public ModuleFactory
{
 public:
	ModuleSSLFactory()
	{
	}
	
	~ModuleSSLFactory()
	{
	}
	
	virtual Module * CreateModule(Server* Me)
	{
		return new ModuleSSL(Me);
	}
};


extern "C" void * init_module( void )
{
	return new ModuleSSLFactory;
}