// Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
// rights reserved.

// License to copy and use this software is granted provided that it
// is identified as the "RSA Data Security, Inc. MD5 Message-Digest
// Algorithm" in all material mentioning or referencing this software
// or this function.
//
// License is also granted to make and use derivative works provided
// that such works are identified as "derived from the RSA Data
// Security, Inc. MD5 Message-Digest Algorithm" in all material
// mentioning or referencing the derived work.
//
// RSA Data Security, Inc. makes no representations concerning either
// the merchantability of this software or the suitability of this
// software for any particular purpose. It is provided "as is"
// without express or implied warranty of any kind.
//
// These notices must be retained in any copies of any part of this
// documentation and/or software.

// The original md5 implementation avoids external libraries.
// This version has dependency on stdio.h for file input and
// string.h for memcpy.

#pragma once

#include <stdio.h>
#include <string.h>

namespace osquery {
namespace md5 {

// Constants for MD5Transform routine.
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

static unsigned char PADDING[64] = {0x80,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0,
                                    0};

// F, G, H and I are basic MD5 functions.
#define FFF(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

// ROTATE_LEFT rotates x left n bits.
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32 - (n))))

// FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
// Rotation is separate from addition to prevent recomputation.
#define FF(a, b, c, d, x, s, ac)                   \
  {                                                \
    (a) += FFF((b), (c), (d)) + (x) + (UINT4)(ac); \
    (a) = ROTATE_LEFT((a), (s));                   \
    (a) += (b);                                    \
  }
#define GG(a, b, c, d, x, s, ac)                 \
  {                                              \
    (a) += G((b), (c), (d)) + (x) + (UINT4)(ac); \
    (a) = ROTATE_LEFT((a), (s));                 \
    (a) += (b);                                  \
  }
#define HH(a, b, c, d, x, s, ac)                 \
  {                                              \
    (a) += H((b), (c), (d)) + (x) + (UINT4)(ac); \
    (a) = ROTATE_LEFT((a), (s));                 \
    (a) += (b);                                  \
  }
#define II(a, b, c, d, x, s, ac)                 \
  {                                              \
    (a) += I((b), (c), (d)) + (x) + (UINT4)(ac); \
    (a) = ROTATE_LEFT((a), (s));                 \
    (a) += (b);                                  \
  }

typedef unsigned char BYTE;

// POINTER defines a generic pointer type
typedef unsigned char *POINTER;

// UINT2 defines a two byte word
typedef unsigned short int UINT2;

// UINT4 defines a four byte word
typedef unsigned long int UINT4;

// convenient object that wraps
// the C-functions for use in C++ only
class MD5 {
 private:
  struct __context_t {
    UINT4 state[4]; /* state (ABCD) */
    UINT4 count[2]; /* number of bits, modulo 2^64 (lsb first) */
    unsigned char buffer[64]; /* input buffer */
  } context;

  // The core of the MD5 algorithm is here.
  // MD5 basic transformation. Transforms state based on block.
  static void MD5Transform(UINT4 state[4], unsigned char block[64]) {
    UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];

    Decode(x, block, 64);

    /* Round 1 */
    FF(a, b, c, d, x[0], S11, 0xd76aa478); /* 1 */
    FF(d, a, b, c, x[1], S12, 0xe8c7b756); /* 2 */
    FF(c, d, a, b, x[2], S13, 0x242070db); /* 3 */
    FF(b, c, d, a, x[3], S14, 0xc1bdceee); /* 4 */
    FF(a, b, c, d, x[4], S11, 0xf57c0faf); /* 5 */
    FF(d, a, b, c, x[5], S12, 0x4787c62a); /* 6 */
    FF(c, d, a, b, x[6], S13, 0xa8304613); /* 7 */
    FF(b, c, d, a, x[7], S14, 0xfd469501); /* 8 */
    FF(a, b, c, d, x[8], S11, 0x698098d8); /* 9 */
    FF(d, a, b, c, x[9], S12, 0x8b44f7af); /* 10 */
    FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
    FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
    FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
    FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
    FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
    FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

    /* Round 2 */
    GG(a, b, c, d, x[1], S21, 0xf61e2562); /* 17 */
    GG(d, a, b, c, x[6], S22, 0xc040b340); /* 18 */
    GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
    GG(b, c, d, a, x[0], S24, 0xe9b6c7aa); /* 20 */
    GG(a, b, c, d, x[5], S21, 0xd62f105d); /* 21 */
    GG(d, a, b, c, x[10], S22, 0x2441453); /* 22 */
    GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
    GG(b, c, d, a, x[4], S24, 0xe7d3fbc8); /* 24 */
    GG(a, b, c, d, x[9], S21, 0x21e1cde6); /* 25 */
    GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
    GG(c, d, a, b, x[3], S23, 0xf4d50d87); /* 27 */
    GG(b, c, d, a, x[8], S24, 0x455a14ed); /* 28 */
    GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
    GG(d, a, b, c, x[2], S22, 0xfcefa3f8); /* 30 */
    GG(c, d, a, b, x[7], S23, 0x676f02d9); /* 31 */
    GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

    /* Round 3 */
    HH(a, b, c, d, x[5], S31, 0xfffa3942); /* 33 */
    HH(d, a, b, c, x[8], S32, 0x8771f681); /* 34 */
    HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
    HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
    HH(a, b, c, d, x[1], S31, 0xa4beea44); /* 37 */
    HH(d, a, b, c, x[4], S32, 0x4bdecfa9); /* 38 */
    HH(c, d, a, b, x[7], S33, 0xf6bb4b60); /* 39 */
    HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
    HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
    HH(d, a, b, c, x[0], S32, 0xeaa127fa); /* 42 */
    HH(c, d, a, b, x[3], S33, 0xd4ef3085); /* 43 */
    HH(b, c, d, a, x[6], S34, 0x4881d05); /* 44 */
    HH(a, b, c, d, x[9], S31, 0xd9d4d039); /* 45 */
    HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
    HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
    HH(b, c, d, a, x[2], S34, 0xc4ac5665); /* 48 */

    /* Round 4 */
    II(a, b, c, d, x[0], S41, 0xf4292244); /* 49 */
    II(d, a, b, c, x[7], S42, 0x432aff97); /* 50 */
    II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
    II(b, c, d, a, x[5], S44, 0xfc93a039); /* 52 */
    II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
    II(d, a, b, c, x[3], S42, 0x8f0ccc92); /* 54 */
    II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
    II(b, c, d, a, x[1], S44, 0x85845dd1); /* 56 */
    II(a, b, c, d, x[8], S41, 0x6fa87e4f); /* 57 */
    II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
    II(c, d, a, b, x[6], S43, 0xa3014314); /* 59 */
    II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
    II(a, b, c, d, x[4], S41, 0xf7537e82); /* 61 */
    II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
    II(c, d, a, b, x[2], S43, 0x2ad7d2bb); /* 63 */
    II(b, c, d, a, x[9], S44, 0xeb86d391); /* 64 */

    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;

    // Zeroize sensitive information.
    memset((POINTER)x, 0, sizeof(x));
  }

  // Encodes input (UINT4) into output (unsigned char). Assumes len is
  // a multiple of 4.
  static void Encode(unsigned char *output, UINT4 *input, unsigned int len) {
    unsigned int i, j;

    for (i = 0, j = 0; j < len; i++, j += 4) {
      output[j] = (unsigned char)(input[i] & 0xff);
      output[j + 1] = (unsigned char)((input[i] >> 8) & 0xff);
      output[j + 2] = (unsigned char)((input[i] >> 16) & 0xff);
      output[j + 3] = (unsigned char)((input[i] >> 24) & 0xff);
    }
  }

  // Decodes input (unsigned char) into output (UINT4). Assumes len is
  // a multiple of 4.
  static void Decode(UINT4 *output, unsigned char *input, unsigned int len) {
    unsigned int i, j;

    for (i = 0, j = 0; j < len; i++, j += 4) {
      output[i] = ((UINT4)input[j]) | (((UINT4)input[j + 1]) << 8) |
                  (((UINT4)input[j + 2]) << 16) | (((UINT4)input[j + 3]) << 24);
    }
  }

 public:
  // MAIN FUNCTIONS
  MD5() { Init(); }

  // MD5 initialization. Begins an MD5 operation, writing a new context.
  void Init() {
    context.count[0] = context.count[1] = 0;

    // Load magic initialization constants.
    context.state[0] = 0x67452301;
    context.state[1] = 0xefcdab89;
    context.state[2] = 0x98badcfe;
    context.state[3] = 0x10325476;
  }

  // MD5 block update operation. Continues an MD5 message-digest
  // operation, processing another message block, and updating the
  // context.
  void Update(unsigned char *input, unsigned int inputLen) {
    unsigned int i, index, partLen;

    // Compute number of bytes mod 64
    index = (unsigned int)((context.count[0] >> 3) & 0x3F);

    // Update number of bits
    if ((context.count[0] += ((UINT4)inputLen << 3)) < ((UINT4)inputLen << 3)) {
      context.count[1]++;
    }
    context.count[1] += ((UINT4)inputLen >> 29);

    partLen = 64 - index;

    // Transform as many times as possible.
    if (inputLen >= partLen) {
      memcpy((POINTER)&context.buffer[index], (POINTER)input, partLen);
      MD5Transform(context.state, context.buffer);

      for (i = partLen; i + 63 < inputLen; i += 64) {
        MD5Transform(context.state, &input[i]);
      }
      index = 0;
    } else {
      i = 0;
    }

    /* Buffer remaining input */
    memcpy((POINTER)&context.buffer[index], (POINTER)&input[i], inputLen - i);
  }

  // MD5 finalization. Ends an MD5 message-digest operation, writing the
  // the message digest and zeroizing the context.
  // Writes to digestRaw
  void Final() {
    unsigned char bits[8];
    unsigned int index, padLen;

    // Save number of bits
    Encode(bits, context.count, 8);

    // Pad out to 56 mod 64.
    index = (unsigned int)((context.count[0] >> 3) & 0x3f);
    padLen = (index < 56) ? (56 - index) : (120 - index);
    Update(PADDING, padLen);

    // Append length (before padding)
    Update(bits, 8);

    // Store state in digest
    Encode(digestRaw, context.state, 16);

    // Zeroize sensitive information.
    memset((POINTER)&context, 0, sizeof(context));

    writeToString();
  }

  /// Buffer must be 32+1 (nul) = 33 chars long at least
  void writeToString() {
    int pos;

    for (pos = 0; pos < 16; pos++)
      sprintf(digestChars + (pos * 2), "%02x", digestRaw[pos]);
  }

 public:
  // an MD5 digest is a 16-byte number (32 hex digits)
  BYTE digestRaw[16];

  // This version of the digest is actually
  // a "printf'd" version of the digest.
  char digestChars[33];

  /// Load a file from disk and digest it
  // Digests a file and returns the result.
  char *digestFile(const char *filename) {
    Init();

    FILE *file;

    int len;
    unsigned char buffer[1024];

    if ((file = fopen(filename, "rb")) == nullptr) {
      fprintf(stderr, "%s can't be opened\n", filename);
    } else {
      while ((len = fread(buffer, 1, 1024, file))) {
        Update(buffer, len);
      }
      Final();

      fclose(file);
    }

    return digestChars;
  }

  /// Digests a byte-array already in memory
  char *digestMemory(BYTE *memchunk, int len) {
    Init();
    Update(memchunk, len);
    Final();

    return digestChars;
  }

  // Digests a string and prints the result.
  char *digestString(const char *string) {
    Init();
    Update((unsigned char *)string, strlen(string));
    Final();

    return digestChars;
  }
};
}
}