/*
 * run -- an nmap wrapper
 *
 * checks nmap options and, if all is well, spawns nmap
 */
#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define TARGET		"169.237.7.61"
#define	NMAP		"/usr/local/bin/nmap"
#define	NMAP0		"nmap"
#define PATH		"PATH=/usr/bin:/bin:/usr/sbin:/sbin";
#define IFS		"IFS= \t\n";

/* valid options -- allow probing, verbose, fragmentation, and ping analysis */
char *okopts[] = {
	"-sT", "-sF", "-sX", "-sN", "-sP", "-sU", "-sA", "-sW", "-sR",
	"-P0", "-PT", "-PS", "-PI", "-O", "-f", "-v", "-vv", "-F", "-sS",
	NULL,
};
/* valid options -- these require numeric arg to the options */
char *numargopts[] = {
	"-g", "-M", "--max_rtt_timeout", "--min_rtt_timeout",
	"--initial_rtt_timeout",
	NULL,
};
/* valid options -- these require lists to the options */
char *listargopts[] = {
	"-p",
	NULL,
};


/*
 * returns 1 if s points to a number with optional surrounding spaces
 * 0 otherwise
 */
int isnum(char *s)
{
	int count = 0;		/* need at least 1 digit */

	/* skip leading spaces */
	while(isspace(*s)) s++;

	/* count digits as you skip over them */
	while(isdigit(*s)){
		s++;
		count++;
	}

	/* skip trailing spaces */
	while(isspace(*s)) s++;

	/* you need at least 1 digit and s pointing to NUL byte */
	return(count && !*s);
}

/*
 * returns 1 if s points to a list of comma-separated numbers and ranges
 * (a range is num-num); 0 otherwise
 */
int islist(char *s)
{
	int count = 0;		/* need at least 1 digit */

	/* skip leading spaces */
	while(isspace(*s)) s++;

	/* skip numbers, list */
	while(*s){
		/* just look for chars here */
		if (!isdigit(*s) && *s != '-' && *s != ',')
			return(0);
		count++;
		s++;
	}

	/* skip trailing spaces */
	while(isspace(*s)) s++;

	/* you need at least 1 list and s pointing to NUL byte */
	return(count && !*s);
}

/*
 * report errors and drop dead!
 */
void error(char *s, char *p)
{
	fprintf(stderr, s, p);
	fprintf(stderr, "\n");
	exit(1);
}

/*
 * the BIG enchilada
 * this checks the options and if valid spawns the nmap program
 */
int main(int argc, char *argv[])
{
	char *ncarg[1000];	/* args to nmap */
	char *env[1000];	/* environment -- okay, MAY be overkill! */
	int i;			/* counter in various loops */
	int okay;		/* 1 when option determined valid, else 0 */
	char **p;		/* loops through lists of strings */

	/* the name of the program to spawn */
	ncarg[0] = NMAP0;

	/*
	 * loop through list of options
	 * if it's valid, add it to the options array ncarg
	 * if not, kiss the user goodbye
	 */
	for(i = 1; i < argc && i < 998; i++){
		okay = 0;
		/*
		 * first option check: see if it doesn't require
		 * an argument -- check okopts list
		 */
		for(p = okopts; *p != NULL; p++)
			if (strcmp(argv[i], *p) == 0){
				/* bingo! we're cool */
				okay = 1;
				ncarg[i] = argv[i];
				break;
			}
		if (okay)
			continue;
		/*
		 * not a valid option so far --
	         * see if it takes a number
		 */
		for(p = numargopts; *p != NULL; p++)
			if (strncmp(argv[i], *p, strlen(*p)) == 0){
				ncarg[i] = argv[i];
				if (strlen(argv[i]) == strlen(*p)){
					i++;
					ncarg[i] = argv[i];
				}
				else
					argv[i] += strlen(*p);
				if (argv[i] == NULL || !isnum(argv[i])){
					error("need number after %s", *p);
					exit(1);
				}
				okay = 1;
				break;
			}
		if (okay)
			continue;
		/*
		 * not a valid option so far --
	         * see if it takes a list
		 */
		for(p = listargopts; *p != NULL; p++)
			if (strncmp(argv[i], *p, strlen(*p)) == 0){
				ncarg[i] = argv[i];
				if (strlen(argv[i]) == strlen(*p)){
					i++;
					ncarg[i] = argv[i];
				}
				else
					argv[i] += strlen(*p);
				if (argv[i] == NULL || !islist(argv[i])){
					error("need list after %s", *p);
					exit(1);
				}
				okay = 1;
				break;
			}
		/*
		 * if it's not valid, give error and quit
		 */
		if (!okay){
			error("%s: unknown or disallowed option\n", argv[i]);
			exit(1);
		}
	}
	/*
	 * all's okay -- set up the rest of the argument list
	 * and the environment
	 */
	ncarg[i] = TARGET;
	ncarg[i+1] = NULL;
	env[0] = PATH;
	env[1] = IFS;
	env[2] = NULL;
	/*
	 * spawn it
	 */
	if (execve(NMAP, ncarg, env) < 0){
		perror("execv: nmap");
		exit(1);
	}
	/*
	 * should NEVER get here!
	 */
	exit(0);
}