NSF hosted CTF ca. 2007

nsf-ctf.c

//Centralized password authentication server.
//Written by clever kid.

#include <netlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#define PASSFILE "password.txt"
#define SERV_HOST "0.0.0.0"
#define SERV_PORT "24312"

#define PASSLEN 256

#define REPLYLEN 256

//#define FORKED

char passwd[PASSLEN];

int handleMe(fd *accept, char *ipbuff){
	int replylen;
	char readpasswd[PASSLEN];
	char reply[REPLYLEN];

	printf("Connection from : %s\n",ipbuff);

	*readpasswd=0;
	*reply=0;
	replylen=0;

	if(Readline(*accept,readpasswd,PASSLEN)<0) 
		return NET_ERROR;

	if(strncmp(readpasswd,passwd,PASSLEN)) {
		//TODO
		//replylen=snprintf(reply,REPLYLEN,readpasswd,"Read: %s Original: %s",passwd);
		replylen=snprintf(reply,REPLYLEN,readpasswd,"%s",passwd);
	} else {
		replylen=snprintf(reply,REPLYLEN,"%s","Success");
	}

	if(Writeline(*accept,reply)<replylen) 
		return NET_ERROR;

	return NET_OK;
}

int readPasswd(){
	int i=0;
	FILE *fp=fopen(PASSFILE,"rt");
	*passwd=0;
	if(!fp) return -1;
	fgets(passwd,PASSLEN,fp);	
	for(;passwd[i]&&i<PASSLEN;++i) {	
		if(passwd[i]=='\r'||passwd[i]=='\n'||passwd[i]==-1) {
			passwd[i]=0; 
		}
	}
	fclose(fp); fp=NULL;
	return 0;
}

int main(){
	fd in,accept;
	int status;
	char ipbuff[256];
	
	#ifdef FORKED
	pid_t pid;
	char *tmpipbuff;
	#endif
	
	srand(time(NULL));
	
	if(Initialize()<0) {
		printf("Data Error\n");
		return -1;
	}

	if(readPasswd()<0) {
		printf("Data Error\n");
		return -1;
	}
	
	if(Bind(&in,SERV_HOST,SERV_PORT)<0) {
		printf("Bind Error\n");
		return -1;
	}
	printf("Bound on : %s:%s\n",SERV_HOST,SERV_PORT);

	while(1) {

		if(Accept(&in,&accept,ipbuff,NULL)<0){
			printf("Accept Error\n");
			continue;
		} 

		#ifdef FORKED
		tmpipbuff=malloc(sizeof(char)*256);
		if(!tmpipbuff) {
			printf("Unable to alloc Client Details Buffer\n");
			Close(&accept);
			continue;
		}
		strncpy(tmpipbuff,ipbuff,256*sizeof(char));		
		pid=fork();
		if(pid<0) {
			printf("Fork Error\n");
			Close(&accept);
			continue;
		}
		if(!pid){
			Close(&in);
			printf("Child: %d\n",getpid());
			status=handleMe(&accept,tmpipbuff);
			free(tmpipbuff);
			Close(&accept);
			return status;
		} else {
			Close(&accept);
		}
		#else
		status=handleMe(&accept,ipbuff);
		Close(&accept);
		#endif
	}
	Close(&in);
	return 0;
}