/*
 * File: md5.c
 * Purpose: MD5 message-digest algorithm
 *
 * Copyright (c) 2018 MAngband and PWMAngband Developers
 *
 * This work is free software; you can redistribute it and/or modify it
 * under the terms of either:
 *
 * a) the GNU General Public License as published by the Free Software
 *    Foundation, version 2, or
 *
 * b) the "Angband licence":
 *    This software may be copied and distributed for educational, research,
 *    and not for profit purposes provided that this copyright and statement
 *    are included in all such copies.  Other copyrights may also apply.
 */


#include "angband.h"


/* 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 F(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) += F ((b), (c), (d)) + (x) + (u32b)(ac); \
    (a) = ROTATE_LEFT ((a), (s)); \
    (a) += (b); \
}

#define GG(a, b, c, d, x, s, ac) \
{ \
    (a) += G ((b), (c), (d)) + (x) + (u32b)(ac); \
    (a) = ROTATE_LEFT ((a), (s)); \
    (a) += (b); \
}

#define HH(a, b, c, d, x, s, ac) \
{ \
    (a) += H ((b), (c), (d)) + (x) + (u32b)(ac); \
    (a) = ROTATE_LEFT ((a), (s)); \
    (a) += (b); \
}

#define II(a, b, c, d, x, s, ac) \
{ \
    (a) += I ((b), (c), (d)) + (x) + (u32b)(ac); \
    (a) = ROTATE_LEFT ((a), (s)); \
    (a) += (b); \
}


/* MD5 context. */
typedef struct
{
    u32b state[4];              /* State (ABCD) */
    u32b count[2];              /* Number of bits, modulo 2^64 (lsb first) */
    unsigned char buffer[512];  /* Input buffer */
} MD5_CTX;


/* Forward declarations */
static void MD5Transform(u32b state[4], unsigned char block[64]);
static void Encode(unsigned char *output, u32b *input, unsigned int len);
static void Decode(u32b *output, unsigned char *input, unsigned int len);
static void MD5_memcpy(byte_ptr output, byte_ptr input, unsigned int len);
static void MD5_memset(byte_ptr output, int value, unsigned int len);


/* MD5 initialization. Begins an MD5 operation, writing a new context. */
static void MD5Init(MD5_CTX *context)
{
    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.
 */
static void MD5Update(MD5_CTX *context, 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] += ((u32b)inputLen << 3)) < ((u32b)inputLen << 3))
        context->count[1]++;
    context->count[1] += ((u32b)inputLen >> 29);

    partLen = 64 - index;

    /* Transform as many times as possible. */
    if (inputLen >= partLen)
    {
        MD5_memcpy((byte_ptr)&context->buffer[index], (byte_ptr)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 */
    MD5_memcpy((byte_ptr)&context->buffer[index], (byte_ptr)&input[i], inputLen - i);
}


/*
 * MD5 finalization. Ends an MD5 message-digest operation, writing the
 * the message digest and zeroizing the context.
 */
static void MD5Final(unsigned char digest[NORMAL_WID], MD5_CTX *context)
{
    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);
    MD5Update(context, PADDING, padLen);

    /* Append length (before padding) */
    MD5Update(context, bits, 8);

    /* Store state in digest */
    Encode(digest, context->state, 16);

    /* Zeroize sensitive information. */
    MD5_memset((byte_ptr)context, 0, sizeof(*context));
}


/* MD5 basic transformation. Transforms state based on block. */
static void MD5Transform(u32b state[4], unsigned char block[64])
{
    u32b 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. */
    MD5_memset((byte_ptr)x, 0, sizeof(x));
}


/*
 * Encodes input (u32b) into output (unsigned char). Assumes len is
 * a multiple of 4.
 */
static void Encode(unsigned char *output, u32b *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 (u32b). Assumes len is
 * a multiple of 4.
 */
static void Decode(u32b *output, unsigned char *input, unsigned int len)
{
    unsigned int i, j;

    for (i = 0, j = 0; j < len; i++, j += 4)
        output[i] = ((u32b)input[j]) | (((u32b)input[j + 1]) << 8) |
            (((u32b)input[j + 2]) << 16) | (((u32b)input[j + 3]) << 24);
}


/* Note: Replace "for loop" with standard memcpy if possible. */
static void MD5_memcpy(byte_ptr output, byte_ptr input, unsigned int len)
{
    unsigned int i;

    for (i = 0; i < len; i++)
        output[i] = input[i];
}


/* Note: Replace "for loop" with standard memset if possible. */
static void MD5_memset(byte_ptr output, int value, unsigned int len)
{
    unsigned int i;

    for (i = 0; i < len; i++)
        ((char *)output)[i] = (char)value;
}


/* Finally we put the hashing algorithm to work */
void MD5Password(char *string)
{
    MD5_CTX context;
    unsigned int len = (unsigned int)strlen(string);
    char temp[MAX_PASS_LEN];
    int i;
    char *dst;
    char hexval[16] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

    MD5Init(&context);
    MD5Update(&context, (unsigned char*)string, len);
    MD5Final((unsigned char*)string, &context);

    /* Convert to hex */
    my_strcpy(temp, "$1$", sizeof(temp));
    dst = temp + 3;
    for (i = 0; i < 16; i++)
    {
        *dst++ = hexval[(string[i] >> 4) & 0xf];
        *dst++ = hexval[string[i] & 0x0f];
    }
    *dst = 0;
    my_strcpy(string, temp, strlen(temp) + 1);
}  
