/* md5.c - MD5 Message-Digest Algorithm
 * Copyright (C) 1995, 1996, 1998, 1999,
 *               2000, 2001 Free Software Foundation, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * According to the definition of MD5 in RFC 1321 from April 1992.
 * NOTE: This is *not* the same file as the one from glibc.
 */
/* Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.  */
/* Heavily modified for GnuPG by <wk@gnupg.org> */

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

#include "types.h"

#ifdef WORDS_BIGENDIAN
#define BIG_ENDIAN_HOST
#endif

//#define DIM(v) (sizeof(v)/sizeof((v)[0]))
#define wipememory2(_ptr, _set, _len)                                          \
    do {                                                                       \
        volatile char *_vptr = (volatile char *)(_ptr);                        \
        size_t _vlen = (_len);                                                 \
        while (_vlen) {                                                        \
            *_vptr = (_set);                                                   \
            _vptr++;                                                           \
            _vlen--;                                                           \
        }                                                                      \
    } while (0)
#define wipememory(_ptr, _len) wipememory2(_ptr, 0, _len)
#define rol(x, n) (((x) << (n)) | ((x) >> (32 - (n))))

typedef struct {
    u32 A, B, C, D; /* chaining variables */
    u32 nblocks;
    byte buf[64];
    int count;
} MD5_CONTEXT;

void md5_init(MD5_CONTEXT *ctx) {
    ctx->A = 0x67452301;
    ctx->B = 0xefcdab89;
    ctx->C = 0x98badcfe;
    ctx->D = 0x10325476;

    ctx->nblocks = 0;
    ctx->count = 0;
}

/* These are the four functions used in the four steps of the MD5 algorithm
   and defined in the RFC 1321.  The first function is a little bit optimized
   (as found in Colin Plumbs public domain implementation).  */
/* #define FF(b, c, d) ((b & c) | (~b & d)) */
#define FF(b, c, d) (d ^ (b & (c ^ d)))
#define FG(b, c, d) FF(d, b, c)
#define FH(b, c, d) (b ^ c ^ d)
#define FI(b, c, d) (c ^ (b | ~d))

static void burn_stack(int bytes) {
    char buf[128];

    wipememory(buf, sizeof buf);
    bytes -= sizeof buf;
    if (bytes > 0) {
        burn_stack(bytes);
    }
}

/****************
 * transform n*64 bytes
 */
static void
/*transform( MD5_CONTEXT *ctx, const void *buffer, size_t len )*/
transform(MD5_CONTEXT *ctx, byte *data) {
    u32 correct_words[16];
    u32 A = ctx->A;
    u32 B = ctx->B;
    u32 C = ctx->C;
    u32 D = ctx->D;
    u32 *cwp = correct_words;

#ifdef BIG_ENDIAN_HOST
    {
        int i;
        byte *p2, *p1;
        for (i = 0, p1 = data, p2 = (byte *)correct_words; i < 16;
             i++, p2 += 4) {
            p2[3] = *p1++;
            p2[2] = *p1++;
            p2[1] = *p1++;
            p2[0] = *p1++;
        }
    }
#else
    memcpy(correct_words, data, 64);
#endif

#define OP(a, b, c, d, s, T)                                                   \
    do {                                                                       \
        a += FF(b, c, d) + (*cwp++) + T;                                       \
        a = rol(a, s);                                                         \
        a += b;                                                                \
    } while (0)

    /* Before we start, one word about the strange constants.
         They are defined in RFC 1321 as

         T[i] = (int) (4294967296.0 * fabs (sin (i))), i=1..64
     */

    /* Round 1.  */
    OP(A, B, C, D, 7, 0xd76aa478);
    OP(D, A, B, C, 12, 0xe8c7b756);
    OP(C, D, A, B, 17, 0x242070db);
    OP(B, C, D, A, 22, 0xc1bdceee);
    OP(A, B, C, D, 7, 0xf57c0faf);
    OP(D, A, B, C, 12, 0x4787c62a);
    OP(C, D, A, B, 17, 0xa8304613);
    OP(B, C, D, A, 22, 0xfd469501);
    OP(A, B, C, D, 7, 0x698098d8);
    OP(D, A, B, C, 12, 0x8b44f7af);
    OP(C, D, A, B, 17, 0xffff5bb1);
    OP(B, C, D, A, 22, 0x895cd7be);
    OP(A, B, C, D, 7, 0x6b901122);
    OP(D, A, B, C, 12, 0xfd987193);
    OP(C, D, A, B, 17, 0xa679438e);
    OP(B, C, D, A, 22, 0x49b40821);

#undef OP
#define OP(f, a, b, c, d, k, s, T)                                             \
    do {                                                                       \
        a += f(b, c, d) + correct_words[k] + T;                                \
        a = rol(a, s);                                                         \
        a += b;                                                                \
    } while (0)

    /* Round 2.  */
    OP(FG, A, B, C, D, 1, 5, 0xf61e2562);
    OP(FG, D, A, B, C, 6, 9, 0xc040b340);
    OP(FG, C, D, A, B, 11, 14, 0x265e5a51);
    OP(FG, B, C, D, A, 0, 20, 0xe9b6c7aa);
    OP(FG, A, B, C, D, 5, 5, 0xd62f105d);
    OP(FG, D, A, B, C, 10, 9, 0x02441453);
    OP(FG, C, D, A, B, 15, 14, 0xd8a1e681);
    OP(FG, B, C, D, A, 4, 20, 0xe7d3fbc8);
    OP(FG, A, B, C, D, 9, 5, 0x21e1cde6);
    OP(FG, D, A, B, C, 14, 9, 0xc33707d6);
    OP(FG, C, D, A, B, 3, 14, 0xf4d50d87);
    OP(FG, B, C, D, A, 8, 20, 0x455a14ed);
    OP(FG, A, B, C, D, 13, 5, 0xa9e3e905);
    OP(FG, D, A, B, C, 2, 9, 0xfcefa3f8);
    OP(FG, C, D, A, B, 7, 14, 0x676f02d9);
    OP(FG, B, C, D, A, 12, 20, 0x8d2a4c8a);

    /* Round 3.  */
    OP(FH, A, B, C, D, 5, 4, 0xfffa3942);
    OP(FH, D, A, B, C, 8, 11, 0x8771f681);
    OP(FH, C, D, A, B, 11, 16, 0x6d9d6122);
    OP(FH, B, C, D, A, 14, 23, 0xfde5380c);
    OP(FH, A, B, C, D, 1, 4, 0xa4beea44);
    OP(FH, D, A, B, C, 4, 11, 0x4bdecfa9);
    OP(FH, C, D, A, B, 7, 16, 0xf6bb4b60);
    OP(FH, B, C, D, A, 10, 23, 0xbebfbc70);
    OP(FH, A, B, C, D, 13, 4, 0x289b7ec6);
    OP(FH, D, A, B, C, 0, 11, 0xeaa127fa);
    OP(FH, C, D, A, B, 3, 16, 0xd4ef3085);
    OP(FH, B, C, D, A, 6, 23, 0x04881d05);
    OP(FH, A, B, C, D, 9, 4, 0xd9d4d039);
    OP(FH, D, A, B, C, 12, 11, 0xe6db99e5);
    OP(FH, C, D, A, B, 15, 16, 0x1fa27cf8);
    OP(FH, B, C, D, A, 2, 23, 0xc4ac5665);

    /* Round 4.  */
    OP(FI, A, B, C, D, 0, 6, 0xf4292244);
    OP(FI, D, A, B, C, 7, 10, 0x432aff97);
    OP(FI, C, D, A, B, 14, 15, 0xab9423a7);
    OP(FI, B, C, D, A, 5, 21, 0xfc93a039);
    OP(FI, A, B, C, D, 12, 6, 0x655b59c3);
    OP(FI, D, A, B, C, 3, 10, 0x8f0ccc92);
    OP(FI, C, D, A, B, 10, 15, 0xffeff47d);
    OP(FI, B, C, D, A, 1, 21, 0x85845dd1);
    OP(FI, A, B, C, D, 8, 6, 0x6fa87e4f);
    OP(FI, D, A, B, C, 15, 10, 0xfe2ce6e0);
    OP(FI, C, D, A, B, 6, 15, 0xa3014314);
    OP(FI, B, C, D, A, 13, 21, 0x4e0811a1);
    OP(FI, A, B, C, D, 4, 6, 0xf7537e82);
    OP(FI, D, A, B, C, 11, 10, 0xbd3af235);
    OP(FI, C, D, A, B, 2, 15, 0x2ad7d2bb);
    OP(FI, B, C, D, A, 9, 21, 0xeb86d391);

    /* Put checksum in context given as argument.  */
    ctx->A += A;
    ctx->B += B;
    ctx->C += C;
    ctx->D += D;
}

/* The routine updates the message-digest context to
 * account for the presence of each of the characters inBuf[0..inLen-1]
 * in the message whose digest is being computed.
 */
void md5_write(MD5_CONTEXT *hd, byte *inbuf, size_t inlen) {
    if (hd->count == 64) { /* flush the buffer */
        transform(hd, hd->buf);
        burn_stack(80 + 6 * sizeof(void *));
        hd->count = 0;
        hd->nblocks++;
    }
    if (!inbuf) {
        return;
    }
    if (hd->count) {
        for (; inlen && hd->count < 64; inlen--) {
            hd->buf[hd->count++] = *inbuf++;
        }
        md5_write(hd, NULL, 0);
        if (!inlen) {
            return;
        }
    }

    while (inlen >= 64) {
        transform(hd, inbuf);
        hd->count = 0;
        hd->nblocks++;
        inlen -= 64;
        inbuf += 64;
    }
    burn_stack(80 + 6 * sizeof(void *));
    for (; inlen && hd->count < 64; inlen--) {
        hd->buf[hd->count++] = *inbuf++;
    }
}
/* The routine final terminates the message-digest computation and
 * ends with the desired message digest in mdContext->digest[0...15].
 * The handle is prepared for a new MD5 cycle.
 * Returns 16 bytes representing the digest.
 */

void md5_final(MD5_CONTEXT *hd) {
    u32 t, msb, lsb;
    byte *p;

    md5_write(hd, NULL, 0); /* flush */
    ;

    t = hd->nblocks;
    /* multiply by 64 to make a byte count */
    lsb = t << 6;
    msb = t >> 26;
    /* add the count */
    t = lsb;
    if ((lsb += hd->count) < t) {
        msb++;
    }
    /* multiply by 8 to make a bit count */
    t = lsb;
    lsb <<= 3;
    msb <<= 3;
    msb |= t >> 29;

    if (hd->count < 56) {            /* enough room */
        hd->buf[hd->count++] = 0x80; /* pad */
        while (hd->count < 56) {
            hd->buf[hd->count++] = 0; /* pad */
        }
    } else {                         /* need one extra block */
        hd->buf[hd->count++] = 0x80; /* pad character */
        while (hd->count < 64) {
            hd->buf[hd->count++] = 0;
        }
        md5_write(hd, NULL, 0); /* flush */
        ;
        memset(hd->buf, 0, 56); /* fill next block with zeroes */
    }
    /* append the 64 bit count */
    hd->buf[56] = lsb;
    hd->buf[57] = lsb >> 8;
    hd->buf[58] = lsb >> 16;
    hd->buf[59] = lsb >> 24;
    hd->buf[60] = msb;
    hd->buf[61] = msb >> 8;
    hd->buf[62] = msb >> 16;
    hd->buf[63] = msb >> 24;
    transform(hd, hd->buf);
    burn_stack(80 + 6 * sizeof(void *));

    p = hd->buf;
#ifdef BIG_ENDIAN_HOST
#define X(a)                                                                   \
    do {                                                                       \
        *p++ = hd->a;                                                          \
        *p++ = hd->a >> 8;                                                     \
        *p++ = hd->a >> 16;                                                    \
        *p++ = hd->a >> 24;                                                    \
    } while (0)
#else /* little endian */
#define X(a)                                                                   \
    do {                                                                       \
        *(u32 *)p = hd->a;                                                     \
        p += 4;                                                                \
    } while (0)
#endif
    X(A);
    X(B);
    X(C);
    X(D);
#undef X
}
