/* vi:set ts=8 sts=4 sw=4 noet:
 *
 * MNV - MNV is not Vim	by Bram Moolenaar
 *
 * Do ":help uganda"  in MNV to read copying and usage conditions.
 * Do ":help credits" in MNV to see a list of people who contributed.
 * See README.txt for an overview of the MNV source code.
 *
 * FIPS-180-2 compliant SHA-256 implementation
 * GPL by Christophe Devine, applies to older version.
 * Modified for md5deep, in public domain.
 * Modified For MNV, Mohsin Ahmed,
 * (original link www.cs.albany.edu/~mosh no longer available)
 * Mohsin Ahmed states this work is distributed under the MNV License or GPL,
 * at your choice.
 *
 * MNV specific notes:
 * Functions exported by this file:
 *  1. sha256_key() hashes the password to 64 bytes char string.
 *  2. sha2_seed() generates a random header.
 *  sha256_self_test() is implicitly called once.
 */

#include "mnv.h"

#if defined(FEAT_CRYPT) || defined(FEAT_PERSISTENT_UNDO)

# define GET_UINT32(n, b, i)		    \
{					    \
    (n) = ( (UINT32_T)(b)[(i)	 ] << 24)   \
	| ( (UINT32_T)(b)[(i) + 1] << 16)   \
	| ( (UINT32_T)(b)[(i) + 2] <<  8)   \
	| ( (UINT32_T)(b)[(i) + 3]	);  \
}

# define PUT_UINT32(n,b,i)		  \
{					  \
    (b)[(i)    ] = (char_u)((n) >> 24);   \
    (b)[(i) + 1] = (char_u)((n) >> 16);   \
    (b)[(i) + 2] = (char_u)((n) >>  8);   \
    (b)[(i) + 3] = (char_u)((n)      );   \
}

    void
sha256_start(context_sha256_T *ctx)
{
    ctx->total[0] = 0;
    ctx->total[1] = 0;

    ctx->state[0] = 0x6A09E667;
    ctx->state[1] = 0xBB67AE85;
    ctx->state[2] = 0x3C6EF372;
    ctx->state[3] = 0xA54FF53A;
    ctx->state[4] = 0x510E527F;
    ctx->state[5] = 0x9B05688C;
    ctx->state[6] = 0x1F83D9AB;
    ctx->state[7] = 0x5BE0CD19;
}

    static void
sha256_process(context_sha256_T *ctx, char_u data[64])
{
    UINT32_T temp1, temp2, W[64];
    UINT32_T A, B, C, D, E, F, G, H;

    GET_UINT32(W[0],  data,  0);
    GET_UINT32(W[1],  data,  4);
    GET_UINT32(W[2],  data,  8);
    GET_UINT32(W[3],  data, 12);
    GET_UINT32(W[4],  data, 16);
    GET_UINT32(W[5],  data, 20);
    GET_UINT32(W[6],  data, 24);
    GET_UINT32(W[7],  data, 28);
    GET_UINT32(W[8],  data, 32);
    GET_UINT32(W[9],  data, 36);
    GET_UINT32(W[10], data, 40);
    GET_UINT32(W[11], data, 44);
    GET_UINT32(W[12], data, 48);
    GET_UINT32(W[13], data, 52);
    GET_UINT32(W[14], data, 56);
    GET_UINT32(W[15], data, 60);

# define  SHR(x, n) (((x) & 0xFFFFFFFF) >> (n))
# define ROTR(x, n) (SHR(x, n) | ((x) << (32 - (n))))

# define S0(x) (ROTR(x, 7) ^ ROTR(x, 18) ^  SHR(x, 3))
# define S1(x) (ROTR(x, 17) ^ ROTR(x, 19) ^  SHR(x, 10))

# define S2(x) (ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22))
# define S3(x) (ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25))

# define F0(x, y, z) (((x) & (y)) | ((z) & ((x) | (y))))
# define F1(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))

# define R(t)				\
(					\
    W[t] = S1(W[(t) -  2]) + W[(t) -  7] +	\
	   S0(W[(t) - 15]) + W[(t) - 16]	\
)

# define P(a,b,c,d,e,f,g,h,x,K)		     \
{					     \
    temp1 = (h) + S3(e) + F1(e, f, g) + (K) + (x); \
    temp2 = S2(a) + F0(a, b, c);	     \
    (d) += temp1; (h) = temp1 + temp2;	     \
}

    A = ctx->state[0];
    B = ctx->state[1];
    C = ctx->state[2];
    D = ctx->state[3];
    E = ctx->state[4];
    F = ctx->state[5];
    G = ctx->state[6];
    H = ctx->state[7];

    P( A, B, C, D, E, F, G, H, W[ 0], 0x428A2F98);
    P( H, A, B, C, D, E, F, G, W[ 1], 0x71374491);
    P( G, H, A, B, C, D, E, F, W[ 2], 0xB5C0FBCF);
    P( F, G, H, A, B, C, D, E, W[ 3], 0xE9B5DBA5);
    P( E, F, G, H, A, B, C, D, W[ 4], 0x3956C25B);
    P( D, E, F, G, H, A, B, C, W[ 5], 0x59F111F1);
    P( C, D, E, F, G, H, A, B, W[ 6], 0x923F82A4);
    P( B, C, D, E, F, G, H, A, W[ 7], 0xAB1C5ED5);
    P( A, B, C, D, E, F, G, H, W[ 8], 0xD807AA98);
    P( H, A, B, C, D, E, F, G, W[ 9], 0x12835B01);
    P( G, H, A, B, C, D, E, F, W[10], 0x243185BE);
    P( F, G, H, A, B, C, D, E, W[11], 0x550C7DC3);
    P( E, F, G, H, A, B, C, D, W[12], 0x72BE5D74);
    P( D, E, F, G, H, A, B, C, W[13], 0x80DEB1FE);
    P( C, D, E, F, G, H, A, B, W[14], 0x9BDC06A7);
    P( B, C, D, E, F, G, H, A, W[15], 0xC19BF174);
    P( A, B, C, D, E, F, G, H, R(16), 0xE49B69C1);
    P( H, A, B, C, D, E, F, G, R(17), 0xEFBE4786);
    P( G, H, A, B, C, D, E, F, R(18), 0x0FC19DC6);
    P( F, G, H, A, B, C, D, E, R(19), 0x240CA1CC);
    P( E, F, G, H, A, B, C, D, R(20), 0x2DE92C6F);
    P( D, E, F, G, H, A, B, C, R(21), 0x4A7484AA);
    P( C, D, E, F, G, H, A, B, R(22), 0x5CB0A9DC);
    P( B, C, D, E, F, G, H, A, R(23), 0x76F988DA);
    P( A, B, C, D, E, F, G, H, R(24), 0x983E5152);
    P( H, A, B, C, D, E, F, G, R(25), 0xA831C66D);
    P( G, H, A, B, C, D, E, F, R(26), 0xB00327C8);
    P( F, G, H, A, B, C, D, E, R(27), 0xBF597FC7);
    P( E, F, G, H, A, B, C, D, R(28), 0xC6E00BF3);
    P( D, E, F, G, H, A, B, C, R(29), 0xD5A79147);
    P( C, D, E, F, G, H, A, B, R(30), 0x06CA6351);
    P( B, C, D, E, F, G, H, A, R(31), 0x14292967);
    P( A, B, C, D, E, F, G, H, R(32), 0x27B70A85);
    P( H, A, B, C, D, E, F, G, R(33), 0x2E1B2138);
    P( G, H, A, B, C, D, E, F, R(34), 0x4D2C6DFC);
    P( F, G, H, A, B, C, D, E, R(35), 0x53380D13);
    P( E, F, G, H, A, B, C, D, R(36), 0x650A7354);
    P( D, E, F, G, H, A, B, C, R(37), 0x766A0ABB);
    P( C, D, E, F, G, H, A, B, R(38), 0x81C2C92E);
    P( B, C, D, E, F, G, H, A, R(39), 0x92722C85);
    P( A, B, C, D, E, F, G, H, R(40), 0xA2BFE8A1);
    P( H, A, B, C, D, E, F, G, R(41), 0xA81A664B);
    P( G, H, A, B, C, D, E, F, R(42), 0xC24B8B70);
    P( F, G, H, A, B, C, D, E, R(43), 0xC76C51A3);
    P( E, F, G, H, A, B, C, D, R(44), 0xD192E819);
    P( D, E, F, G, H, A, B, C, R(45), 0xD6990624);
    P( C, D, E, F, G, H, A, B, R(46), 0xF40E3585);
    P( B, C, D, E, F, G, H, A, R(47), 0x106AA070);
    P( A, B, C, D, E, F, G, H, R(48), 0x19A4C116);
    P( H, A, B, C, D, E, F, G, R(49), 0x1E376C08);
    P( G, H, A, B, C, D, E, F, R(50), 0x2748774C);
    P( F, G, H, A, B, C, D, E, R(51), 0x34B0BCB5);
    P( E, F, G, H, A, B, C, D, R(52), 0x391C0CB3);
    P( D, E, F, G, H, A, B, C, R(53), 0x4ED8AA4A);
    P( C, D, E, F, G, H, A, B, R(54), 0x5B9CCA4F);
    P( B, C, D, E, F, G, H, A, R(55), 0x682E6FF3);
    P( A, B, C, D, E, F, G, H, R(56), 0x748F82EE);
    P( H, A, B, C, D, E, F, G, R(57), 0x78A5636F);
    P( G, H, A, B, C, D, E, F, R(58), 0x84C87814);
    P( F, G, H, A, B, C, D, E, R(59), 0x8CC70208);
    P( E, F, G, H, A, B, C, D, R(60), 0x90BEFFFA);
    P( D, E, F, G, H, A, B, C, R(61), 0xA4506CEB);
    P( C, D, E, F, G, H, A, B, R(62), 0xBEF9A3F7);
    P( B, C, D, E, F, G, H, A, R(63), 0xC67178F2);

    ctx->state[0] += A;
    ctx->state[1] += B;
    ctx->state[2] += C;
    ctx->state[3] += D;
    ctx->state[4] += E;
    ctx->state[5] += F;
    ctx->state[6] += G;
    ctx->state[7] += H;
}

    void
sha256_update(context_sha256_T *ctx, char_u *input, UINT32_T length)
{
    UINT32_T left, fill;

    if (length == 0)
	return;

    left = ctx->total[0] & 0x3F;
    fill = 64 - left;

    ctx->total[0] += length;
    ctx->total[0] &= 0xFFFFFFFF;

    if (ctx->total[0] < length)
	ctx->total[1]++;

    if (left && length >= fill)
    {
	memcpy((void *)(ctx->buffer + left), (void *)input, fill);
	sha256_process(ctx, ctx->buffer);
	length -= fill;
	input  += fill;
	left = 0;
    }

    while (length >= 64)
    {
	sha256_process(ctx, input);
	length -= 64;
	input  += 64;
    }

    if (length)
	memcpy((void *)(ctx->buffer + left), (void *)input, length);
}

static char_u sha256_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
};

    void
sha256_finish(context_sha256_T *ctx, char_u digest[32])
{
    UINT32_T last, padn;
    UINT32_T high, low;
    char_u   msglen[8];

    high = (ctx->total[0] >> 29) | (ctx->total[1] <<  3);
    low  = (ctx->total[0] <<  3);

    PUT_UINT32(high, msglen, 0);
    PUT_UINT32(low,  msglen, 4);

    last = ctx->total[0] & 0x3F;
    padn = (last < 56) ? (56 - last) : (120 - last);

    sha256_update(ctx, sha256_padding, padn);
    sha256_update(ctx, msglen, 8);

    PUT_UINT32(ctx->state[0], digest,  0);
    PUT_UINT32(ctx->state[1], digest,  4);
    PUT_UINT32(ctx->state[2], digest,  8);
    PUT_UINT32(ctx->state[3], digest, 12);
    PUT_UINT32(ctx->state[4], digest, 16);
    PUT_UINT32(ctx->state[5], digest, 20);
    PUT_UINT32(ctx->state[6], digest, 24);
    PUT_UINT32(ctx->state[7], digest, 28);
}
#endif // FEAT_CRYPT || FEAT_PERSISTENT_UNDO

#if defined(FEAT_CRYPT)
/*
 * Returns hex digest of "buf[buf_len]" in a static array.
 * if "salt" is not NULL also do "salt[salt_len]".
 */
    char_u *
sha256_bytes(
    char_u *buf,
    int    buf_len,
    char_u *salt,
    int    salt_len)
{
    char_u	     sha256sum[32];
    static char_u    hexit[65];
    int		     j;
    context_sha256_T ctx;

    sha256_self_test();

    sha256_start(&ctx);
    sha256_update(&ctx, buf, buf_len);
    if (salt != NULL)
	sha256_update(&ctx, salt, salt_len);
    sha256_finish(&ctx, sha256sum);
    for (j = 0; j < 32; j++)
	sprintf((char *)hexit + j * 2, "%02x", sha256sum[j]);
    hexit[sizeof(hexit) - 1] = '\0';
    return hexit;
}

/*
 * Returns sha256(buf) as 64 hex chars in static array.
 */
    char_u *
sha256_key(
    char_u *buf,
    char_u *salt,
    int    salt_len)
{
    // No passwd means don't encrypt
    if (buf == NULL || *buf == NUL)
	return (char_u *)"";

    return sha256_bytes(buf, (int)STRLEN(buf), salt, salt_len);
}

/*
 * These are the standard FIPS-180-2 test vectors
 */

static char *sha_self_test_msg[] = {
    "abc",
    "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
    NULL
};

static char *sha_self_test_vector[] = {
    "ba7816bf8f01cfea414140de5dae2223" \
    "b00361a396177a9cb410ff61f20015ad",
    "248d6a61d20638b8e5c026930c3e6039" \
    "a33ce45964ff2167f6ecedd419db06c1",
    "cdc76e5c9914fb9281a1c7e284d73e67" \
    "f1809a48a497200e046d39ccc7112cd0"
};

/*
 * Perform a test on the SHA256 algorithm.
 * Return FAIL or OK.
 */
    int
sha256_self_test(void)
{
    int		     i, j;
    char	     output[65];
    context_sha256_T ctx;
    char_u	     buf[1000];
    char_u	     sha256sum[32];
    static int	     failures = 0;
    char_u	     *hexit;
    static int	     sha256_self_tested = 0;

    if (sha256_self_tested > 0)
	return failures > 0 ? FAIL : OK;
    sha256_self_tested = 1;

    for (i = 0; i < 3; i++)
    {
	if (i < 2)
	{
	    hexit = sha256_bytes((char_u *)sha_self_test_msg[i],
		    (int)STRLEN(sha_self_test_msg[i]),
		    NULL, 0);
	    STRCPY(output, hexit);
	}
	else
	{
	    sha256_start(&ctx);
	    mnv_memset(buf, 'a', 1000);
	    for (j = 0; j < 1000; j++)
		sha256_update(&ctx, (char_u *)buf, 1000);
	    sha256_finish(&ctx, sha256sum);
	    for (j = 0; j < 32; j++)
		sprintf(output + j * 2, "%02x", sha256sum[j]);
	}
	if (memcmp(output, sha_self_test_vector[i], 64))
	{
	    failures++;
	    output[sizeof(output) - 1] = '\0';
	    // printf("sha256_self_test %d failed %s\n", i, output);
	}
    }
    return failures > 0 ? FAIL : OK;
}

    static unsigned int
get_some_time(void)
{
# ifdef HAVE_GETTIMEOFDAY
    struct timeval tv;

    // Using usec makes it less predictable.
    gettimeofday(&tv, NULL);
    return (unsigned int)(tv.tv_sec + tv.tv_usec);
# else
    return (unsigned int)time(NULL);
# endif
}

/*
 * Fill "header[header_len]" with random_data.
 * Also "salt[salt_len]" when "salt" is not NULL.
 */
    void
sha2_seed(
    char_u *header,
    int    header_len,
    char_u *salt,
    int    salt_len)
{
    int		     i;
    static char_u    random_data[1000];
    char_u	     sha256sum[32];
    context_sha256_T ctx;

    srand(get_some_time());

    for (i = 0; i < (int)sizeof(random_data) - 1; i++)
	random_data[i] = (char_u)((get_some_time() ^ rand()) & 0xff);
    sha256_start(&ctx);
    sha256_update(&ctx, (char_u *)random_data, sizeof(random_data));
    sha256_finish(&ctx, sha256sum);

    // put first block into header.
    for (i = 0; i < header_len; i++)
	header[i] = sha256sum[i % sizeof(sha256sum)];

    // put remaining block into salt.
    if (salt != NULL)
	for (i = 0; i < salt_len; i++)
	    salt[i] = sha256sum[(i + header_len) % sizeof(sha256sum)];
}

#endif // FEAT_CRYPT
