crack_demo.c

// Demo didáctica de cracking de SHA-256 sin sal contra wordlist en memoria.
//
// Uso:
//   ./crack_demo <hash_hex> [<wordlist_path>]
//
// Ejemplo:
//   echo -n "letmein" | sha256sum
//   ./crack_demo 1c8bfe8f801d79745c4631d09fff36c82aa37fc4cce4fc946683d7b336b63032
//
// NO usar en producción. Solo ilustrativo: passwords reales tienen salt
// y un KDF caro (bcrypt/argon2id) por encima.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/sha.h>

void hex(const unsigned char *buf, char *out) {
    for (int i = 0; i < SHA256_DIGEST_LENGTH; i++)
        sprintf(out + 2 * i, "%02x", buf[i]);
    out[64] = '\0';
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Uso: %s <hash_hex> [wordlist]\n", argv[0]);
        return 1;
    }
    const char *target = argv[1];
    const char *wlpath = argc > 2 ? argv[2] : "/usr/share/wordlists/rockyou.txt";

    FILE *fp = fopen(wlpath, "r");
    if (!fp) { perror("fopen"); return 1; }

    char line[256];
    long tried = 0;
    while (fgets(line, sizeof line, fp)) {
        size_t n = strcspn(line, "\r\n");
        line[n] = '\0';
        if (n == 0) continue;

        unsigned char digest[SHA256_DIGEST_LENGTH];
        SHA256((unsigned char *) line, n, digest);

        char hexdigest[65];
        hex(digest, hexdigest);
        if (strcmp(hexdigest, target) == 0) {
            printf("[+] Encontrado tras %ld intentos: \"%s\"\n", tried + 1, line);
            fclose(fp);
            return 0;
        }
        tried++;
        if (tried % 100000 == 0) {
            fprintf(stderr, "\r[*] %ld passwords probados...", tried);
            fflush(stderr);
        }
    }
    printf("\n[-] No encontrado tras %ld intentos.\n", tried);
    fclose(fp);
    return 1;
}