Miscellany

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


#define SEMTEX "semtex.labs.overthewire.org"
#define X86PORT "24000"
#define SEMTEXFILE "result.2"

#define DEBUG

int create_socket(int sockfd, struct addrinfo *servinfo) { 

	if ((sockfd = socket(servinfo->ai_family, servinfo->ai_socktype,
			     servinfo->ai_protocol)) == -1) {
		perror("socket");
		return -1;
	 }

	 return sockfd;
}


int create_addrinfo(struct addrinfo *hints, struct addrinfo **servinfo)
{
	int status = -1;

	memset(hints, 0, sizeof(hints));
	hints->ai_family = AF_INET;
	hints->ai_socktype = SOCK_STREAM;
	hints->ai_flags = AI_PASSIVE;

	if ((status = getaddrinfo(SEMTEX,X86PORT,
				  hints, servinfo)) != 0) {
		fprintf(stderr,"getaddrinfo: %s\n", gai_strerror(status));
		return -1;
	}

	return status;
}

void write_bytes(unsigned char *bytes, FILE *fp, int len)
{
	int i = 0,j = 0;
	size_t bytes_write = 0;
	int blen = (len/2)+1;
	unsigned char *buffer = NULL;


	if (len > 0) {

		buffer = (unsigned char *)calloc(blen,sizeof(unsigned char));

		if (!buffer) {
			perror("calloc");
			exit(-1);
		}

	
		if (len > 1) {
			j = 0;
			i = 0;
#ifdef DEBUG
			puts("len > 1");
#endif
			for (i = 0; i < len/2 ; i++) {
				buffer[i] = bytes[i*2];
			}
		}
		else {
#ifdef DEBUG
			puts("len < 1");
#endif
			buffer[0] = bytes[0];
		}
#ifdef DEBUG
		printf("[DEBUG:%s:] Writing %d (blen) bytes (%u len) %d %% 2  = %d\n%s\n",__FUNCTION__,
							sizeof(unsigned char) * blen,
							len,
							len,len / 2,
							buffer);
#endif
		if ((bytes_write = fwrite(buffer, sizeof(unsigned char) * blen
					  ,1,fp)) == 0) {
			perror("fwrite");
			exit(0);
		}
		free(buffer);
	}
}


void recv_loop(int sockfd)
{
	int bytes_read = 0;
	unsigned char *bytes_recv = (unsigned char *)calloc(255,sizeof(unsigned char));
	FILE *fp = fopen(SEMTEXFILE,"w");

	if (!fp) {
		perror("fopen");
		exit(0);
	}

	while((bytes_read = recv(sockfd, bytes_recv, sizeof(unsigned char)*255, 0)) != 0) {
#ifdef DEBUG
		printf("[DEBUG:%s] read %d bytes \n",__FUNCTION__, 
						    bytes_read);
#endif
		write_bytes(bytes_recv, fp, bytes_read);
	}

	free(bytes_recv);
	fclose(fp);
}

int main()
{
	int sockfd = -1;
	struct addrinfo hints;
	struct addrinfo *servinfo;

	if (create_addrinfo(&hints, &servinfo) == -1)
		return -1;

#ifdef DEBUG
	puts("[+] getaddrinfo successfully called");
#endif

	sockfd = create_socket(sockfd, servinfo);

#ifdef DEBUG
	puts("[+] Got a socket");
#endif

	if ((connect(sockfd, servinfo->ai_addr, servinfo->ai_addrlen)) == -1) {
		perror("connect");	
		return -1;
	}
#ifdef DEBUG
	puts("[+] Successfully connected");
#endif

	recv_loop(sockfd);

	close(sockfd);
	free(servinfo);

	return 0;
}