/*      $OpenBSD: md5.c,v 1.13 2025/04/14 18:32:24 claudio Exp $        */

/*
 * This code implements the MD5 message-digest algorithm.
 * The algorithm is due to Ron Rivest.  This code was
 * written by Colin Plumb in 1993, no copyright is claimed.
 * This code is in the public domain; do with it what you wish.
 *
 * Equivalent code is available from RSA Data Security, Inc.
 * This code has been tested against that, and is equivalent,
 * except that you don't need to include two pages of legalese
 * with every copy.
 *
 * To compute the message digest of a chunk of bytes, declare an
 * MD5Context structure, pass it to MD5Init, call MD5Update as
 * needed on buffers full of bytes, and then call MD5Final, which
 * will fill a supplied 16-byte array with the digest.
 */

#include <sys/types.h>
#include <string.h>
#include <md5.h>

#define PUT_64BIT_LE(cp, value) do {                                    \
        (cp)[7] = (value) >> 56;                                        \
        (cp)[6] = (value) >> 48;                                        \
        (cp)[5] = (value) >> 40;                                        \
        (cp)[4] = (value) >> 32;                                        \
        (cp)[3] = (value) >> 24;                                        \
        (cp)[2] = (value) >> 16;                                        \
        (cp)[1] = (value) >> 8;                                         \
        (cp)[0] = (value); } while (0)

#define PUT_32BIT_LE(cp, value) do {                                    \
        (cp)[3] = (value) >> 24;                                        \
        (cp)[2] = (value) >> 16;                                        \
        (cp)[1] = (value) >> 8;                                         \
        (cp)[0] = (value); } while (0)

static const u_int8_t PADDING[MD5_BLOCK_LENGTH] = {
        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
};

/*
 * Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
 * initialization constants.
 */
void
MD5Init(MD5_CTX *ctx)
{
        ctx->count = 0;
        ctx->state[0] = 0x67452301;
        ctx->state[1] = 0xefcdab89;
        ctx->state[2] = 0x98badcfe;
        ctx->state[3] = 0x10325476;
}
DEF_WEAK(MD5Init);

/*
 * Update context to reflect the concatenation of another buffer full
 * of bytes.
 */
void
MD5Update(MD5_CTX *ctx, const unsigned char *input, size_t len)
{
        size_t have, need;

        /* Calling with no data is valid (we do nothing) */
        if (len == 0)
                return;

        /* Check how many bytes we already have and how many more we need. */
        have = (size_t)((ctx->count >> 3) & (MD5_BLOCK_LENGTH - 1));
        need = MD5_BLOCK_LENGTH - have;

        /* Update bitcount */
        ctx->count += (u_int64_t)len << 3;

        if (len >= need) {
                if (have != 0) {
                        memcpy(ctx->buffer + have, input, need);
                        MD5Transform(ctx->state, ctx->buffer);
                        input += need;
                        len -= need;
                        have = 0;
                }

                /* Process data in MD5_BLOCK_LENGTH-byte chunks. */
                while (len >= MD5_BLOCK_LENGTH) {
                        MD5Transform(ctx->state, input);
                        input += MD5_BLOCK_LENGTH;
                        len -= MD5_BLOCK_LENGTH;
                }
        }

        /* Handle any remaining bytes of data. */
        if (len != 0)
                memcpy(ctx->buffer + have, input, len);
}
DEF_WEAK(MD5Update);

/*
 * Pad pad to 64-byte boundary with the bit pattern
 * 1 0* (64-bit count of bits processed, MSB-first)
 */
void
MD5Pad(MD5_CTX *ctx)
{
        u_int8_t count[8];
        size_t padlen;

        /* Convert count to 8 bytes in little endian order. */
        PUT_64BIT_LE(count, ctx->count);

        /* Pad out to 56 mod 64. */
        padlen = MD5_BLOCK_LENGTH -
            ((ctx->count >> 3) & (MD5_BLOCK_LENGTH - 1));
        if (padlen < 1 + 8)
                padlen += MD5_BLOCK_LENGTH;
        MD5Update(ctx, PADDING, padlen - 8);            /* padlen - 8 <= 64 */
        MD5Update(ctx, count, 8);
}
DEF_WEAK(MD5Pad);

/*
 * Final wrapup--call MD5Pad, fill in digest and zero out ctx.
 */
void
MD5Final(unsigned char digest[MD5_DIGEST_LENGTH], MD5_CTX *ctx)
{
        int i;

        MD5Pad(ctx);
        for (i = 0; i < 4; i++)
                PUT_32BIT_LE(digest + i * 4, ctx->state[i]);
        explicit_bzero(ctx, sizeof(*ctx));
}
DEF_WEAK(MD5Final);


/* The four core functions - F1 is optimized somewhat */

/* #define F1(x, y, z) (x & y | ~x & z) */
#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))

/* This is the central step in the MD5 algorithm. */
#define MD5STEP(f, w, x, y, z, data, s) \
        ( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )

/*
 * The core of the MD5 algorithm, this alters an existing MD5 hash to
 * reflect the addition of 16 longwords of new data.  MD5Update blocks
 * the data and converts bytes into longwords for this routine.
 */
void
MD5Transform(u_int32_t state[4], const u_int8_t block[MD5_BLOCK_LENGTH])
{
        u_int32_t a, b, c, d, in[MD5_BLOCK_LENGTH / 4];

#if BYTE_ORDER == LITTLE_ENDIAN
        memcpy(in, block, sizeof(in));
#else
        for (a = 0; a < MD5_BLOCK_LENGTH / 4; a++) {
                in[a] = (u_int32_t)(
                    (u_int32_t)(block[a * 4 + 0]) |
                    (u_int32_t)(block[a * 4 + 1]) <<  8 |
                    (u_int32_t)(block[a * 4 + 2]) << 16 |
                    (u_int32_t)(block[a * 4 + 3]) << 24);
        }
#endif

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

        MD5STEP(F1, a, b, c, d, in[ 0] + 0xd76aa478,  7);
        MD5STEP(F1, d, a, b, c, in[ 1] + 0xe8c7b756, 12);
        MD5STEP(F1, c, d, a, b, in[ 2] + 0x242070db, 17);
        MD5STEP(F1, b, c, d, a, in[ 3] + 0xc1bdceee, 22);
        MD5STEP(F1, a, b, c, d, in[ 4] + 0xf57c0faf,  7);
        MD5STEP(F1, d, a, b, c, in[ 5] + 0x4787c62a, 12);
        MD5STEP(F1, c, d, a, b, in[ 6] + 0xa8304613, 17);
        MD5STEP(F1, b, c, d, a, in[ 7] + 0xfd469501, 22);
        MD5STEP(F1, a, b, c, d, in[ 8] + 0x698098d8,  7);
        MD5STEP(F1, d, a, b, c, in[ 9] + 0x8b44f7af, 12);
        MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
        MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
        MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122,  7);
        MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
        MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
        MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);

        MD5STEP(F2, a, b, c, d, in[ 1] + 0xf61e2562,  5);
        MD5STEP(F2, d, a, b, c, in[ 6] + 0xc040b340,  9);
        MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
        MD5STEP(F2, b, c, d, a, in[ 0] + 0xe9b6c7aa, 20);
        MD5STEP(F2, a, b, c, d, in[ 5] + 0xd62f105d,  5);
        MD5STEP(F2, d, a, b, c, in[10] + 0x02441453,  9);
        MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
        MD5STEP(F2, b, c, d, a, in[ 4] + 0xe7d3fbc8, 20);
        MD5STEP(F2, a, b, c, d, in[ 9] + 0x21e1cde6,  5);
        MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6,  9);
        MD5STEP(F2, c, d, a, b, in[ 3] + 0xf4d50d87, 14);
        MD5STEP(F2, b, c, d, a, in[ 8] + 0x455a14ed, 20);
        MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905,  5);
        MD5STEP(F2, d, a, b, c, in[ 2] + 0xfcefa3f8,  9);
        MD5STEP(F2, c, d, a, b, in[ 7] + 0x676f02d9, 14);
        MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);

        MD5STEP(F3, a, b, c, d, in[ 5] + 0xfffa3942,  4);
        MD5STEP(F3, d, a, b, c, in[ 8] + 0x8771f681, 11);
        MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
        MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
        MD5STEP(F3, a, b, c, d, in[ 1] + 0xa4beea44,  4);
        MD5STEP(F3, d, a, b, c, in[ 4] + 0x4bdecfa9, 11);
        MD5STEP(F3, c, d, a, b, in[ 7] + 0xf6bb4b60, 16);
        MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
        MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6,  4);
        MD5STEP(F3, d, a, b, c, in[ 0] + 0xeaa127fa, 11);
        MD5STEP(F3, c, d, a, b, in[ 3] + 0xd4ef3085, 16);
        MD5STEP(F3, b, c, d, a, in[ 6] + 0x04881d05, 23);
        MD5STEP(F3, a, b, c, d, in[ 9] + 0xd9d4d039,  4);
        MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
        MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
        MD5STEP(F3, b, c, d, a, in[2 ] + 0xc4ac5665, 23);

        MD5STEP(F4, a, b, c, d, in[ 0] + 0xf4292244,  6);
        MD5STEP(F4, d, a, b, c, in[7 ] + 0x432aff97, 10);
        MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
        MD5STEP(F4, b, c, d, a, in[5 ] + 0xfc93a039, 21);
        MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3,  6);
        MD5STEP(F4, d, a, b, c, in[3 ] + 0x8f0ccc92, 10);
        MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
        MD5STEP(F4, b, c, d, a, in[1 ] + 0x85845dd1, 21);
        MD5STEP(F4, a, b, c, d, in[8 ] + 0x6fa87e4f,  6);
        MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
        MD5STEP(F4, c, d, a, b, in[6 ] + 0xa3014314, 15);
        MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
        MD5STEP(F4, a, b, c, d, in[4 ] + 0xf7537e82,  6);
        MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
        MD5STEP(F4, c, d, a, b, in[2 ] + 0x2ad7d2bb, 15);
        MD5STEP(F4, b, c, d, a, in[9 ] + 0xeb86d391, 21);

        state[0] += a;
        state[1] += b;
        state[2] += c;
        state[3] += d;
}
DEF_WEAK(MD5Transform);