Dump salt and digest of bcrypt hash

dump_bcrypt_hash.c

// Original src: https://github.com/pyca/bcrypt/blob/master/src/_csrc/bcrypt.c

#include <stdio.h>
#include <string.h>
#include <sys/types.h>

// Maps to character set "./ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
static const u_int8_t index_64[128] = {
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
	255, 255, 255, 255, 255, 255, 0, 1, 54, 55,
	56, 57, 58, 59, 60, 61, 62, 63, 255, 255,
	255, 255, 255, 255, 255, 2, 3, 4, 5, 6,
	7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
	17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,
	255, 255, 255, 255, 255, 255, 28, 29, 30,
	31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
	41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
	51, 52, 53, 255, 255, 255, 255, 255
};
#define CHAR64(c)  ( (c) > 127 ? 255 : index_64[(c)])

/*
 * read buflen (after decoding) bytes of data from b64data
 */
static int
decode_bcrypt64(u_int8_t *buffer, size_t len, const char *b64data)
{
	u_int8_t *bp = buffer;
	const u_int8_t *p = b64data;
	u_int8_t c1, c2, c3, c4;

	while (bp < buffer + len) {
		c1 = CHAR64(*p);
		/* Invalid data */
		if (c1 == 255)
			return -1;

		c2 = CHAR64(*(p + 1));
		if (c2 == 255)
			return -1;

		*bp++ = (c1 << 2) | ((c2 & 0x30) >> 4);
		if (bp >= buffer + len)
			break;

		c3 = CHAR64(*(p + 2));
		if (c3 == 255)
			return -1;

		*bp++ = ((c2 & 0x0f) << 4) | ((c3 & 0x3c) >> 2);
		if (bp >= buffer + len)
			break;

		c4 = CHAR64(*(p + 3));
		if (c4 == 255)
			return -1;
		*bp++ = ((c3 & 0x03) << 6) | c4;

		p += 4;
	}
	return 0;
}

/*
 * print len bytes in dex
 */
void
printh(char *h, int len) {
  for (int i=0; i<len; i++) {
    printf("%02x", (unsigned char)h[i]);
  }
}

int main(int argc, char *argv[]) {
  char buf[1024];
  for (int i=1; i<argc; i++) {
    printf("===== %s =====\n", argv[i]);
    if (strlen(argv[i]) != 53) {
      printf("ERROR: Not a valid bcrypt hash\n");
    } else {
      memset(buf, '\0', 1024);
      // First get the salt (128-bit)
      decode_bcrypt64(buf, 22, argv[i]);
      // Then the digest (192-bit)
      decode_bcrypt64(buf+16, 31, argv[i]+22);
      // Dump the results
      printf("Salt  : ");
      printh(buf, 16);
      printf("\nDigest: ");
      printh(buf+16, 24);
      printf("\n");
    }
  }
}