/*-
 * Copyright 2005 Colin Percival
 * Copyright (c) the build2 authors (see the COPYRIGHT file).
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <stdint.h>
#include <stddef.h> /* size_t */

#ifdef SHA256_TEST_DRIVER

struct context
{
  uint32_t state[8];
  uint64_t count;
  uint8_t buf[64];
};

typedef struct context SHA256_CTX;

static void SHA256_Init (SHA256_CTX*);
static void SHA256_Update (SHA256_CTX*, const void*, size_t);
static void SHA256_Final (uint8_t[32], SHA256_CTX*);

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

int
main ()
{
  SHA256_CTX c;
  uint8_t r[32];

  /* ""    e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 */
  SHA256_Init (&c);
  SHA256_Final (r, &c);
  assert (r[0] == 0xe3 && r[31] == 0x55);

  /* "123" a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3 */
  SHA256_Init (&c);
  SHA256_Update (&c, "123", 3);
  SHA256_Final (r, &c);
  assert (r[0] == 0xa6 && r[31] == 0xe3);

  return 0;
}

#endif /* SHA256_TEST_DRIVER */

#include <libbutl/byte-order.h>

#if defined(__FreeBSD__) || defined(__NetBSD__)
#  include <sys/endian.h> /* be32dec(), be32enc(), be64enc */
#else
static uint32_t
be32dec(const void *pp)
{
	unsigned char const *p = (unsigned char const *)pp;

	return ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]);
}

static void
be32enc(void *pp, uint32_t u)
{
	unsigned char *p = (unsigned char *)pp;

	p[0] = (u >> 24) & 0xff;
	p[1] = (u >> 16) & 0xff;
	p[2] = (u >> 8) & 0xff;
	p[3] = u & 0xff;
}

static void
be64enc(void *pp, uint64_t u)
{
	unsigned char *p = (unsigned char *)pp;

        p[0] = (u >> 56) & 0xff;
	p[1] = (u >> 48) & 0xff;
	p[2] = (u >> 40) & 0xff;
        p[3] = (u >> 32) & 0xff;
        p[4] = (u >> 24) & 0xff;
	p[5] = (u >> 16) & 0xff;
	p[6] = (u >> 8) & 0xff;
	p[7] = u & 0xff;
}
#endif /* __FreeBSD__ || __NetBSD__ */

/* The rest is the unmodified (except for a few explicit casts to make
   compilable in C++) latest implementation from FreeBSD sys/crypto/sha2/. */

#include <string.h>

#if BYTE_ORDER == BIG_ENDIAN

/* Copy a vector of big-endian uint32_t into a vector of bytes */
#define be32enc_vect(dst, src, len)	\
	memcpy((void *)dst, (const void *)src, (size_t)len)

/* Copy a vector of bytes into a vector of big-endian uint32_t */
#define be32dec_vect(dst, src, len)	\
	memcpy((void *)dst, (const void *)src, (size_t)len)

#else /* BYTE_ORDER != BIG_ENDIAN */

/*
 * Encode a length len/4 vector of (uint32_t) into a length len vector of
 * (unsigned char) in big-endian form.  Assumes len is a multiple of 4.
 */
static void
be32enc_vect(unsigned char *dst, const uint32_t *src, size_t len)
{
	size_t i;

	for (i = 0; i < len / 4; i++)
		be32enc(dst + i * 4, src[i]);
}

/*
 * Decode a big-endian length len vector of (unsigned char) into a length
 * len/4 vector of (uint32_t).  Assumes len is a multiple of 4.
 */
static void
be32dec_vect(uint32_t *dst, const unsigned char *src, size_t len)
{
	size_t i;

	for (i = 0; i < len / 4; i++)
		dst[i] = be32dec(src + i * 4);
}

#endif /* BYTE_ORDER != BIG_ENDIAN */

/* Elementary functions used by SHA256 */
#define Ch(x, y, z)	((x & (y ^ z)) ^ z)
#define Maj(x, y, z)	((x & (y | z)) | (y & z))
#define SHR(x, n)	(x >> n)
#define ROTR(x, n)	((x >> n) | (x << (32 - n)))
#define S0(x)		(ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22))
#define S1(x)		(ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25))
#define s0(x)		(ROTR(x, 7) ^ ROTR(x, 18) ^ SHR(x, 3))
#define s1(x)		(ROTR(x, 17) ^ ROTR(x, 19) ^ SHR(x, 10))

/* SHA256 round function */
#define RND(a, b, c, d, e, f, g, h, k)			\
	t0 = h + S1(e) + Ch(e, f, g) + k;		\
	t1 = S0(a) + Maj(a, b, c);			\
	d += t0;					\
	h  = t0 + t1;

/* Adjusted round function for rotating state */
#define RNDr(S, W, i, k)			\
	RND(S[(64 - i) % 8], S[(65 - i) % 8],	\
	    S[(66 - i) % 8], S[(67 - i) % 8],	\
	    S[(68 - i) % 8], S[(69 - i) % 8],	\
	    S[(70 - i) % 8], S[(71 - i) % 8],	\
	    W[i] + k)

/*
 * SHA256 block compression function.  The 256-bit state is transformed via
 * the 512-bit input block to produce a new state.
 */
static void
SHA256_Transform(uint32_t * state, const unsigned char block[64])
{
	uint32_t W[64];
	uint32_t S[8];
	uint32_t t0, t1;
	int i;

	/* 1. Prepare message schedule W. */
	be32dec_vect(W, block, 64);
	for (i = 16; i < 64; i++)
		W[i] = s1(W[i - 2]) + W[i - 7] + s0(W[i - 15]) + W[i - 16];

	/* 2. Initialize working variables. */
	memcpy(S, state, 32);

	/* 3. Mix. */
	RNDr(S, W, 0, 0x428a2f98);
	RNDr(S, W, 1, 0x71374491);
	RNDr(S, W, 2, 0xb5c0fbcf);
	RNDr(S, W, 3, 0xe9b5dba5);
	RNDr(S, W, 4, 0x3956c25b);
	RNDr(S, W, 5, 0x59f111f1);
	RNDr(S, W, 6, 0x923f82a4);
	RNDr(S, W, 7, 0xab1c5ed5);
	RNDr(S, W, 8, 0xd807aa98);
	RNDr(S, W, 9, 0x12835b01);
	RNDr(S, W, 10, 0x243185be);
	RNDr(S, W, 11, 0x550c7dc3);
	RNDr(S, W, 12, 0x72be5d74);
	RNDr(S, W, 13, 0x80deb1fe);
	RNDr(S, W, 14, 0x9bdc06a7);
	RNDr(S, W, 15, 0xc19bf174);
	RNDr(S, W, 16, 0xe49b69c1);
	RNDr(S, W, 17, 0xefbe4786);
	RNDr(S, W, 18, 0x0fc19dc6);
	RNDr(S, W, 19, 0x240ca1cc);
	RNDr(S, W, 20, 0x2de92c6f);
	RNDr(S, W, 21, 0x4a7484aa);
	RNDr(S, W, 22, 0x5cb0a9dc);
	RNDr(S, W, 23, 0x76f988da);
	RNDr(S, W, 24, 0x983e5152);
	RNDr(S, W, 25, 0xa831c66d);
	RNDr(S, W, 26, 0xb00327c8);
	RNDr(S, W, 27, 0xbf597fc7);
	RNDr(S, W, 28, 0xc6e00bf3);
	RNDr(S, W, 29, 0xd5a79147);
	RNDr(S, W, 30, 0x06ca6351);
	RNDr(S, W, 31, 0x14292967);
	RNDr(S, W, 32, 0x27b70a85);
	RNDr(S, W, 33, 0x2e1b2138);
	RNDr(S, W, 34, 0x4d2c6dfc);
	RNDr(S, W, 35, 0x53380d13);
	RNDr(S, W, 36, 0x650a7354);
	RNDr(S, W, 37, 0x766a0abb);
	RNDr(S, W, 38, 0x81c2c92e);
	RNDr(S, W, 39, 0x92722c85);
	RNDr(S, W, 40, 0xa2bfe8a1);
	RNDr(S, W, 41, 0xa81a664b);
	RNDr(S, W, 42, 0xc24b8b70);
	RNDr(S, W, 43, 0xc76c51a3);
	RNDr(S, W, 44, 0xd192e819);
	RNDr(S, W, 45, 0xd6990624);
	RNDr(S, W, 46, 0xf40e3585);
	RNDr(S, W, 47, 0x106aa070);
	RNDr(S, W, 48, 0x19a4c116);
	RNDr(S, W, 49, 0x1e376c08);
	RNDr(S, W, 50, 0x2748774c);
	RNDr(S, W, 51, 0x34b0bcb5);
	RNDr(S, W, 52, 0x391c0cb3);
	RNDr(S, W, 53, 0x4ed8aa4a);
	RNDr(S, W, 54, 0x5b9cca4f);
	RNDr(S, W, 55, 0x682e6ff3);
	RNDr(S, W, 56, 0x748f82ee);
	RNDr(S, W, 57, 0x78a5636f);
	RNDr(S, W, 58, 0x84c87814);
	RNDr(S, W, 59, 0x8cc70208);
	RNDr(S, W, 60, 0x90befffa);
	RNDr(S, W, 61, 0xa4506ceb);
	RNDr(S, W, 62, 0xbef9a3f7);
	RNDr(S, W, 63, 0xc67178f2);

	/* 4. Mix local working variables into global state */
	for (i = 0; i < 8; i++)
		state[i] += S[i];
}

static unsigned char PAD[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
};

/* Add padding and terminating bit-count. */
static void
SHA256_Pad(SHA256_CTX * ctx)
{
	unsigned char len[8];
	uint32_t r, plen;

	/*
	 * Convert length to a vector of bytes -- we do this now rather
	 * than later because the length will change after we pad.
	 */
	be64enc(len, ctx->count);

	/* Add 1--64 bytes so that the resulting length is 56 mod 64 */
	r = (ctx->count >> 3) & 0x3f;
	plen = (r < 56) ? (56 - r) : (120 - r);
	SHA256_Update(ctx, PAD, (size_t)plen);

	/* Add the terminating bit-count */
	SHA256_Update(ctx, len, 8);
}

/* SHA-256 initialization.  Begins a SHA-256 operation. */
void
SHA256_Init(SHA256_CTX * ctx)
{

	/* Zero bits processed so far */
	ctx->count = 0;

	/* Magic initialization constants */
	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;
}

/* Add bytes into the hash */
void
SHA256_Update(SHA256_CTX * ctx, const void *in, size_t len)
{
	uint64_t bitlen;
	uint32_t r;
	const unsigned char *src = (const unsigned char *) (in);

	/* Number of bytes left in the buffer from previous updates */
	r = (ctx->count >> 3) & 0x3f;

	/* Convert the length into a number of bits */
	bitlen = len << 3;

	/* Update number of bits */
	ctx->count += bitlen;

	/* Handle the case where we don't need to perform any transforms */
	if (len < 64 - r) {
		memcpy(&ctx->buf[r], src, len);
		return;
	}

	/* Finish the current block */
	memcpy(&ctx->buf[r], src, 64 - r);
	SHA256_Transform(ctx->state, ctx->buf);
	src += 64 - r;
	len -= 64 - r;

	/* Perform complete blocks */
	while (len >= 64) {
		SHA256_Transform(ctx->state, src);
		src += 64;
		len -= 64;
	}

	/* Copy left over data into buffer */
	memcpy(ctx->buf, src, len);
}

/*
 * SHA-256 finalization.  Pads the input data, exports the hash value,
 * and clears the context state.
 */
void
SHA256_Final(uint8_t digest[32], SHA256_CTX * ctx)
{

	/* Add padding */
	SHA256_Pad(ctx);

	/* Write the hash */
	be32enc_vect(digest, ctx->state, 32);

	/* Clear the context state */
	memset((void *)ctx, 0, sizeof(*ctx));
}
