exclude multicast, private and reserved address space

README.md

@@ -3,12 +3,20 @@
 2.	OpenSSL library.
 
 ## Background
-Currently, Kusaba X and a lot of Kusaba X ports use a very insecure algorithm for calculating "Poster IDs". That is, a semi-unique ID used as a means of identification. Unfortunately, the developers must have overlooked the major flaw in the algorithm when developing the function. The poster IDs are calculated by simply truncating an (unsalted) MD5 hash of the dotted decimal representation of the user's IP address to 6 characters. As there are 2<sup>32</sup> IPv4 addresses and only 2<sup>24</sup> possible IDs, it makes it possible (and incredibly easy) to narrow an ID down to ~256 IP addresses. The rest could possibly be eliminated using GeoIP or any other means.
+Currently, Kusaba X and a lot of Kusaba X ports use a very insecure algorithm for calculating "Poster IDs". That is, a semi-unique ID used as a means of identification. Unfortunately, the developers must have overlooked the major flaw in the algorithm when developing the function. The poster IDs are calculated by simply truncating an (unsalted) MD5 hash of the dotted decimal representation of the user's IP address to 6 characters. As there are 2<sup>32</sup> (before excluding multicast, private and reserved space) IPv4 addresses and only 2<sup>24</sup> possible IDs, it makes it possible (and incredibly easy) to narrow an ID down to ~256 IP addresses. The rest could possibly be eliminated using GeoIP or any other means.
 
 Although it may seem unpractical because of the time and processing power required to test a hash against every single IP address, it could be done in just minutes with a large rainbow table.
 
 In short, this simple program will turn a standard Kusaba X "Poster ID" into ~256 possible IPv4 addresses.
 
+## Excluded Ranges
+ - Class D and E addresses
+ - 10.0.0.0/8
+ - 127.0.0.0/8
+ - 172.16.0.0/12
+ - 192.168.0.0/16
+After excluding multicast, private and reserved space, there is 3 706 584 831 IP addresses (~14% deduction).
+
 ## Usage
 To compile, use `make`.
 

ids.c

@@ -51,8 +51,8 @@ main(int argc, char *argv[])
 {	
 
 	if(argc != 3 || strcmp(argv[1], "--help") == 0) {
-		fprintf(stderr, "Usage: ids <database> <poster id>\n");
-		fprintf(stderr, "   or: ids <database> --generate\n");
+		fprintf(stderr, "Usage: ids <database> <poster id>\n"
+						"   or: ids <database> --generate\n");
 		exit(0);
 	}
 
@@ -62,15 +62,38 @@ main(int argc, char *argv[])
 		// generate rainbow table
 		FILE *fp = fopen(database, "w");
 		if(fp == NULL) {
-			fprintf(stderr, "Error opening %s for writing!\n", database);
+			fprintf(stderr, "Could not open %s for writing!\n", database);
 			return 1;
 		}
 
 		char *hash = malloc(7);
 
 		unsigned long x;
 		char *ip;
-		for(x = 16843009; x < 4294967295 ; x++) {
+
+		// 3741253376
+
+		// - 16777216
+		// - 16777216
+		// - 1048576
+		// - 65536
+
+		for(x = 16843009; x <= 3758096384 ; x++) {
+			if(x == 167772160) {
+				// skip 10.0.0.0/8
+				x = 184549376;
+			} else if(x == 2130706432) {
+				// skip 127.0.0.0/8
+				x = 2147483648;
+			} else if(x == 2886729728) {
+				// skip 172.16.0.0/12
+				x = 2887778304;
+			} else if(x == 3232235520) {
+				// skip 192.168.0.0/16
+				x = 3232301056;
+			}
+
+
 			ip = ultoip(x);
 
 			// create hash
@@ -91,14 +114,14 @@ main(int argc, char *argv[])
 		}
 
 		fclose(fp);	
-	} else if(strlen(argv[1]) == 6) {
+	} else if(strlen(argv[2]) == 6) {
 		char *hash = malloc(7);
 		hash[6] = 0;
 
 		// open rainbow table for reading
 		FILE *fp = fopen(database, "r");
 		if(fp == NULL) {
-			fprintf(stderr, "Error opening %s for reading!\n", database);
+			fprintf(stderr, "Could not open %s for reading!\n", database);
 			return 1;
 		}
 
@@ -107,6 +130,20 @@ main(int argc, char *argv[])
 		// iterate through ipv4 address space
 		unsigned long i = 16843009;
 		while(!feof(fp)) {
+			if(i == 167772160) {
+				// skip 10.0.0.0/8
+				i = 184549376;
+			} else if(i == 2130706432) {
+				// skip 127.0.0.0/8
+				i = 2147483648;
+			} else if(i == 2886729728) {
+				// skip 172.16.0.0/12
+				i = 2887778304;
+			} else if(i == 3232235520) {
+				// skip 192.168.0.0/16
+				i = 3232301056;
+			}
+
 			fread(hash, 1, 6, fp);
 			// test hash
 			if(strncmp(hash, search_hash, 6) == 0) {
@@ -118,7 +155,7 @@ main(int argc, char *argv[])
 
 		fclose(fp);
 	} else {
-		fprintf(stderr, "Error: Poster ID must be 6 characters (hexadecimal)!");
+		fprintf(stderr, "Error: Poster ID must be 6 characters (hexadecimal)!\n");
 		return 1;
 	}
 }