/* - - -----< redirector >---- - -
 *  
 *  [ne]interaktivni redirektor
 *  pouziti:
 *  iredir <local port> [<host> <destination port>]
 *
 *  Pokud nezadas host a dport, spusti
 *  se jako interaktivni redir, tzn. 
 *  po pripojeni klienta se po zadani hesla 
 *  zepta kam se ma pripojit...
 * 
 *                     -( trace@dump.cz )-
 */

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>

#include <signal.h>
#include <sys/wait.h>

#define max(a, b)	((a)>(b)?(a):(b))

/* odkomentujte, pokud chcete, aby redirektor po pripojeni klienta
 * vyzadoval heslo */
// #define REQUIRE_PASSWORD

#define DEBUG

void dperror(char *str) {
#ifdef DEBUG
	perror(str);
#endif
}

void killchild(int x) {
	int status;
	wait(&status);
}

int copyloop(int client, int dport, struct hostent *h);
void daemonize();

int main(int argc, char *argv[]) {
	int local_sock, client_sock, localport, destport;
	struct sockaddr_in local, client;
	struct hostent *h;
	int sockaddr_len, len;
	char buff[1024];
	int interactive;
#ifdef REQUIRE_PASSWORD
	char passwd[16] = {0};

	/* po jednom znaku! (kvuli `strings iredir`) */
	passwd[0] = 'i';
	passwd[1] = ' ';
	passwd[2] = 'f';
	passwd[3] = 'e';
	passwd[4] = 'e';
	passwd[5] = 'l';
	passwd[6] = ' ';
	passwd[7] = 'h';
	passwd[8] = 'a';
	passwd[9] = 'p';
	passwd[10] = 'p';
	passwd[11] = 'y';
#endif	
	if (argc == 4) {
		interactive = 0;
		localport = atoi(argv[1]);
		destport = atoi(argv[3]);	
 		if ((h = gethostbyname(argv[2])) == NULL) {
			perror("gethostbyname");
			exit(1);
		}
	} else if (argc == 2) {
		interactive = 1;
		localport = atoi(argv[1]);
	} else {
		printf("usage: %s localport [<host> <destination_port>]\n", argv[0]);
		exit(1);
	}

	memset(&local, 0, sizeof(struct sockaddr_in));
	local.sin_port = htons(localport);
	local.sin_addr.s_addr = inet_addr("0.0.0.0");
	local.sin_family = AF_INET;
	
	if ((local_sock = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
		perror("local socket");
		exit(-1);
	}
	
	if (bind(local_sock, (struct sockaddr *)&local, sizeof(struct sockaddr_in)) == -1) {
		perror("local bind");
		close(local_sock);
		exit(-1);
	}

	if (listen(local_sock, 5) == -1) {
		perror("local listen");
		close(local_sock);
		exit(-1);
	}
#ifndef DEBUG
	daemonize();
#endif

	signal(SIGCHLD, &killchild);
	
	while(1) {
		sockaddr_len = sizeof(struct sockaddr_in);
	
		if ((client_sock = accept(local_sock, (struct sockaddr *)&client, &sockaddr_len)) == -1) {
			dperror("local accept");
			exit(-1);
		}
		
		switch (fork()) {
			case -1:
				dperror("fork");
				exit(-1);
				break;
				
			case 0:
#ifdef REQUIRE_PASSWORD
				read(client_sock, buff, sizeof(buff));
				if (!strstr(buff, passwd)) {
					close(client_sock);
					continue;
				}
#endif
				if (interactive) {
					char *ptr;
					
					write(client_sock, "Host: ", 6);
					memset(buff, 0, sizeof(buff));
					len = read(client_sock, buff, 256);

					/* odstranime pripady newline */
					ptr = buff;
					while (*ptr && *ptr > 13) ptr++;
					*ptr = '\0';
					
					if ((h = gethostbyname(buff)) == NULL) {
						dperror("gethostbyname");
						exit(-1);
					}

					write(client_sock, "Port: ", 6);
					read(client_sock, buff, 6);
					destport = atoi(buff);
				}
				
				write(client_sock, "connecting...", 13);
				copyloop(client_sock, destport, h);
				exit(0);
		}
		close(client_sock);
	}
	close(local_sock);
	exit(0);
} 

int copyloop(int client, int dport, struct hostent *h) {
	int server, ndfs, len;
	struct sockaddr_in serv;
	fd_set readfds;
	char buffer[4096];
	
	
	memset(&serv, 0, sizeof(struct sockaddr_in));
	memcpy(&serv.sin_addr, h->h_addr_list[0], sizeof(in_addr_t));
	serv.sin_family = AF_INET;
	serv.sin_port = htons(dport);

	if ((server = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		dperror("server socket");
		exit(-1);
	}

	/* pripojeni k cilovemu serveru */
	if (connect(server, (struct sockaddr *)&serv, sizeof(serv)) == -1) {
		write(client, "failed!\n", 8);
		dperror("server connect");
		exit(-1);
	}
	write(client, "OK\n", 3);

	/* do readfds dame deskriptory, mezi kteryma chceme selectovat 
	   V tomhle pripade server a client */ 
	FD_ZERO(&readfds);
	FD_SET(server, &readfds);
	FD_SET(client, &readfds);
	
	/* nastavime pocet testovanych deskriptoru (0 - ndfs-1) */
	ndfs = max(server, client)+1;
	
	/* je-li jeden z deskriptoru pripraven ke cteni, otevre se,
	 * prectou se data a poslou na druhy */	
	while(select(ndfs, &readfds, NULL, NULL, NULL) != -1) {
		if (FD_ISSET(server, &readfds)) {
			len = read(server, buffer, sizeof(buffer));
			if (len>0) 
				write(client, buffer, len);
			else
				break;
		}
		if (FD_ISSET(client, &readfds)) {
			len = read(client, buffer, sizeof(buffer));
			if (len>0) 
				write(server, buffer, len);
			else
				break;
		}

		FD_ZERO(&readfds);
		FD_SET(server, &readfds);
		FD_SET(client, &readfds);	
	}
	close(server);
	close(client);
	return 0;
}	
	
/* hodi redir na pozadi */
void daemonize() {
	int fd;
	
	if (fork()) 
		exit(0);
	else {
		setsid();
		chdir("/");
		fd = open("/dev/null", O_RDWR);
		dup2(fd, 0);
		dup2(fd, 1);
		dup2(fd, 2);
		close(fd);
	}
}