md5.c

md5.c

// md5.c

#include <stdlib.h>

static char* bin2hex(const unsigned char* b, size_t len, char* s)
{
  int i;
  for (i = 0; i < len; i++)
  {
    s[i*2] = (b[i] >> 4) < 10 ? (b[i] >> 4) + 48: (b[i] >> 4) + 87;
    s[i*2+1] = (b[i] & 0x0F) < 10 ? (b[i] & 0x0F) + 48 : (b[i] & 0x0F) + 87;
  }
  s[len*2] = 0;
  return s;
}

unsigned char* md5(const unsigned char *data, size_t len, unsigned char *digest) {
  unsigned char *msg = NULL;
  size_t new_len, bits_len, offset;
  unsigned int a,b,c,d,i,f,g,temp;
  unsigned int *w, *h0, *h1, *h2, *h3;
  static const unsigned char r[] = {
    7,12,17,22,7,12,17,22,7,12,17,22,7,12,17,22,
    5,9,14,20,5,9,14,20,5,9,14,20,5,9,14,20,
    4,11,16,23,4,11,16,23,4,11,16,23,4,11,16,23,
    6,10,15,21,6,10,15,21,6,10,15,21,6,10,15,21
  };
  static const unsigned int k[] = {
    0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
    0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
    0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
    0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
    0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
    0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
    0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
    0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
    0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
    0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
    0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
    0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
    0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
    0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
    0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
    0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
  };
  h0 = (unsigned int *)(digest);
  h1 = (unsigned int *)(digest+4);
  h2 = (unsigned int *)(digest+8);
  h3 = (unsigned int *)(digest+12);
 
  *h0 = 0x67452301;
  *h1 = 0xefcdab89;
  *h2 = 0x98badcfe;
  *h3 = 0x10325476;
  new_len = ((((len + 8) / 64) + 1) * 64) - 8;
  msg = calloc(new_len + 64, 1);
  memcpy(msg, data, len);
  msg[len] = 128;
  bits_len = 8*len;
  memcpy(msg + new_len, &bits_len, 4);
  for(offset=0; offset<new_len; offset += (512/8)) {
    w = (unsigned int *)(msg + offset);
    a = *h0;
    b = *h1;
    c = *h2;
    d = *h3;
    for(i = 0; i<64; i++) {       
      if (i < 16) {
        f = (b & c) | ((~b) & d);
        g = i;
      } else if (i < 32) {
        f = (d & b) | ((~d) & c);
        g = (5*i + 1) % 16;
      } else if (i < 48) {
        f = b ^ c ^ d;
        g = (3*i + 5) % 16;          
      } else {
        f = c ^ (b | (~d));
        g = (7*i) % 16;
      }
      temp = d;
      d = c;
      c = b;
      b = b + ((((a + f + k[i] + w[g])) << (r[i])) | (((a + f + k[i] + w[g])) >> (32 - (r[i]))));
      a = temp;
    }
    *h0 += a;
    *h1 += b;
    *h2 += c;
    *h3 += d;
  }
  free(msg);
  return digest;
}

char* md5_string(const unsigned char *data, size_t len, char *s) {
  unsigned char digest[16];
  return bin2hex(md5(data, len, digest),16,s);
}