#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>


/*
*    Network/Netmask to zone file converter
*
*    Copyright (C) 2018 Rob van der Putten, Leiden, Holland, 
*    rob at sput dot nl.
* 
*    This program is free software; you can redistribute it and/or modify
*    it under the terms of the GNU General Public License version 3 as
*    published by the Free Software Foundation.
* 
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU General Public License for more details.
*/


/*  Powers of two  */
int pows[] = { 1, 2, 4, 8, 16, 32, 64, 128 };
/*  Netmasks; 0000, 1000, 1100, 1110, etc  */
int mask4[] = { 0, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe };
int mask6[] = { 0, 0x08, 0x0c, 0x0e };


void proc4(int ip[], int mask, char *txt)
{
    int divn, i, j, max, remn;

    i = 0;
    j = 0;
    max = 0;

    /*  Per byte  */
    divn = mask / 8;
    remn = mask % 8;

    if (remn == 0) {
	if(divn > 3)
	    printf("%d", ip[3]);
	else
	    printf("*");
	j = divn;
	while (j > 0) {
	    printf(".%d", ip[j - 1]);
	    j--;
	}
	printf("\tIN\tA\t127.0.0.2\n");
	if(txt != NULL)
	    printf("\t\tIN\tTXT\t\"https://www.spamhaus.org/sbl/query/%s\"\n", \
	      txt);
    } else {
	i = mask4[remn] & ip[divn];    /*  In case they got it wrong  */
	max = pows[8 - remn] + i;
	while (i < max) {
	    printf("*.%d", i);
	    j = divn;
	    while (j > 0) {
		printf(".%d", ip[j - 1]);
		j--;
	    }
	    printf("\tIN\tA\t127.0.0.2\n");
	    if(txt != NULL)
		printf("\t\tIN\tTXT\t\"https://www.spamhaus.org/sbl/query/%s\"\n", \
		  txt);
	    i++;
	}
    }
}

void proc6(unsigned char nibs[], int mask, char *txt)
{
    int divn, i, j, max, remn;

    i = 0;
    j = 0;
    max = 0;

    /*  Per nibble  */
    divn = mask / 4;
    remn = mask % 4;

    if (remn == 0) {
	if(divn > 31)
	    printf("%x", nibs[31]);
	else
	     printf("*");
	j = divn;
	while (j > 0) {
	    printf(".%x", nibs[j - 1]);
	    j--;
	}
	printf("\tIN\tA\t127.0.0.2\n");
	if(txt != NULL)
	    printf("\t\t\tIN\tTXT\t\"https://www.spamhaus.org/sbl/query/%s\"\n", \
	      txt);
    } else {
	i = mask6[remn] & nibs[divn];    /*  In case they got it wrong  */
	max = pows[4 - remn] + i;
	while (i < max) {
	    printf("*.%x", i);
	    j = divn;
	    while (j > 0) {
		printf(".%x", nibs[j - 1]);
		j--;
	    }
	    printf("\tIN\tA\t127.0.0.2\n");
	    if(txt != NULL)
		printf("\t\t\tIN\tTXT\t\"https://www.spamhaus.org/sbl/query/%s\"\n", \
		  txt);
	    i++;
	}
    }
}

void hlp(void)
{
    fprintf(stderr, "Usage: procdrop [-t]\n");
    fprintf(stderr, "The '-t' option adds TXT records.\n\n");

    fprintf(stderr, "Copyright (c) 2018 R.J. van der Putten, Leiden, Holland, ");
    fprintf(stderr, "rob at sput dot nl\n");
    fprintf(stderr, "GNU GPL applies\n\n");
}


int main(int argc, char **argv)
{
    int i, ip[4], j, len, mask, tf;
    unsigned char ip6adr[16], nibs[32];
    char ip6str[64], line[4096], txt[256];

    /*
    *    Translates network/netmask into dns zone file.
    */

    i = 0;
    j = 0;
    len = 0;
    memset(ip, 0, sizeof(ip));
    mask = 0;
    tf = 0;
    memset(ip6adr, 0, sizeof(ip6adr));
    memset(ip6str, 0, sizeof(ip6str));
    memset(line, 0, 4096);
    memset(nibs, 0, 32);
    memset(txt, 0, 256);

    if (argc > 2) {
	hlp();
	exit(1);
    }
    if (argc > 1) {
	if (strcmp(argv[1], "-t") == 0) {
	    tf = 1;
	} else {
	    hlp();
	    exit(1);
	}
    }

    while (fgets(line, 4096, stdin)) {
	if (line[0] == ';' || (line[0] < '0' && line[0] > 0)) {
	    printf("%s", line);
	    continue;
	}
	if (sscanf(line, "%d.%d.%d.%d/%d ; %255s", \
	  &ip[0], &ip[1], &ip[2], &ip[3], &mask, txt) == 6) {
	    if (ip[0] < 0 || ip[0] > 255 || \
	      ip[1] < 0 || ip[1] > 255 || \
	      ip[2] < 0 || ip[2] > 255 || 
	      ip[3] < 0 || ip[3] > 255) {
		printf("%s", line);
		continue;
	    }
	    if (mask < 0 || mask > 32) {
		printf("%s", line);
		continue;
	    }
	    printf("; %d.%d.%d.%d/%d\t%s\n", \
	      ip[0], ip[1], ip[2], ip[3], mask, txt);
	    if (tf == 0)
		proc4(ip, mask, NULL);
	    else
		proc4(ip, mask, txt);
	} else if (sscanf(line, "%63s ; %255s", ip6str, txt) == 2) {
	    i = 0;
	    len = strlen(ip6str);
	    mask = -1;
	    while (i < len) {
		if (ip6str[i] == '/') {
		    ip6str[i] = 0 ;
		    mask = atoi(ip6str + i + 1);
		    break;
		}
		i++;
	    }
	    if (mask < 0 || mask > 128) {
		printf("%s", line);
		continue;
	    }
	    if (inet_pton(AF_INET6, ip6str, ip6adr) == 1) {
		printf("; %s/%d\t%s\n", ip6str, mask, txt);
		i = 0;
		j = 0;
		/*  Translate bytes to nibbles  */
		while (i < 16) {
		    nibs[j] = (ip6adr[i] >> 4);
		    j++;
		    nibs[j] = 0xf & ip6adr[i];
		    i++;
		    j++;
		}
		if (tf == 0)
		    proc6(nibs, mask, NULL);
		else
		    proc6(nibs, mask, txt);
	    } else {
		printf("%s", line);
	    }
	} else {
	    printf("%s", line);
	}
    }

    return(0);
}