Simple bruteforcer for BostonKeyParty CTF level 'Randy'.

gistfile1.c

#include <stdlib.h>
#include <stdio.h>
#include <limits.h>

unsigned int outputs[7][4] = {
	{0x7358837a, 0x6e1b2658, 0x3c00c5ff,  0x8c0d4aa},
	{0x34d8c3b5, 0x5b56dca1,  0x78236d7, 0x1973085e},
	{0x1f49456c, 0x27c0fa1d, 0x145214aa, 0x6200299c},
	{0x1fea6614, 0x41cdb864, 0x53c0ed56, 0x63642916},
	{0x4e81abc7, 0x792ce075, 0x7d2bc59c, 0x42a11ada},
	{0x683d3f5d,  0xcaae38d, 0x7ec81c18, 0x444671e6},
	{0x28c9a8fe,  0x3324b23, 0x3075f253, 0x60d2e9d2}};

unsigned int seeds[7] = {544485486,1914712179,811888180,874524781,1915974758,825319712,555819297};

void printasascii(unsigned int value){
	printf("%c", (value) & 0xff);
	printf("%c", (value >> 8) & 0xff);
	printf("%c", (value >> 16) & 0xff);
	printf("%c", (value >> 24) & 0xff);
}

typedef union {
	unsigned int integer;
	unsigned char bytes[4];
} output_t;

int main(int argc, char* argv[]){
	output_t value;
	value.bytes[0] = 0x20;
	value.bytes[1] = 0x20;
	value.bytes[2] = 0x20;
	value.bytes[3] = 0x20;
	unsigned int outcome;
	unsigned int tries = 0;
	size_t output_row = 0;
	size_t seeds_found = 0;
	while(1){
		for(output_row = 0; output_row < 7; output_row++){
			srandom(value.integer);
			outcome = random();
			if(outcome == outputs[output_row][0]){
				outcome = random();
				if(outcome == outputs[output_row][1]){
					outcome = random();
					if(outcome == outputs[output_row][2]){
						outcome = random();
						if(outcome == outputs[output_row][3]){
							seeds[output_row] = value.integer;
							seeds_found++;
							printf("Found %i/7 seeds\n", seeds_found);
							printf("Seed %i = \"", output_row);
							printasascii(value.integer);
							printf("\" (%i)\n", value.integer);
							if(seeds_found == 7) break;
						}
					}
				}
			}
		}

		/* iterate printable ascii */
		if(value.bytes[3] < 0x7f){
			value.bytes[3]++;
		} else {
			value.bytes[3] = 0x20;
			if(value.bytes[2] < 0x7f){
				value.bytes[2]++;
			} else {
				value.bytes[2] = 0x20;
				if(value.bytes[1] < 0x7f){
					value.bytes[1]++;
				} else {
					value.bytes[1] = 0x20;
					if(value.bytes[0] < 0x7f){
						value.bytes[0]++;
					} else {
						printf("Exhausted keyspace.\n");
						break;
					}
				}
			}
		}
		tries++;
		if(tries % 1000000 == 0){
			printf("Tried %i seeds\nCurrent seed trying: ", tries);
			printasascii(value.integer);
			printf("\n");
		}
	}
	for(output_row = 0; output_row < 7; output_row++){
		printasascii(seeds[output_row]);
	}

	printf("\n");
	for(output_row = 0; output_row < 7; output_row++){
		printf("%i\n",seeds[output_row]);
	}

	return 0;
}