brick-sha2

// -*- mode: C++; indent-tabs-mode: nil; c-basic-offset: 4 -*-

/*
 * (c) 2017 Jan Mrázek
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Based on:
 *
 * FILE:	sha2.c
 * AUTHOR:	Aaron D. Gifford <me@aarongifford.com>
 *
 * Copyright (c) 2000-2001, Aaron D. Gifford
 * 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.
 * 3. Neither the name of the copyright holder nor the names of contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTOR(S) ``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 CONTRIBUTOR(S) 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.
 *
 * OPENBSD ORIGINAL: lib/libc/hash/sha2.c
 */

#pragma once

#include <brick-assert>
#include <brick-string>
#include <string>
#include <iomanip>
#include <sstream>
#include <cstring>
#include <sys/types.h>

namespace brq {
namespace detail {

// #ifdef DIVINE_RELAX_WARNINGS
// DIVINE_RELAX_WARNINGS
// #endif

/*** SHA-256/384/512 Various Length Definitions ***********************/
static const constexpr int SHA256_BLOCK_LENGTH	 = 64;
static const constexpr int SHA256_DIGEST_LENGTH	 = 32;
static const constexpr int SHA256_DIGEST_STRING_LENGTH = (SHA256_DIGEST_LENGTH * 2 + 1);
static const constexpr int SHA384_BLOCK_LENGTH	 = 128;
static const constexpr int SHA384_DIGEST_LENGTH	 = 48;
static const constexpr int SHA384_DIGEST_STRING_LENGTH = (SHA384_DIGEST_LENGTH * 2 + 1);
static const constexpr int SHA512_BLOCK_LENGTH	 = 128;
static const constexpr int SHA512_DIGEST_LENGTH	 = 64;
static const constexpr int SHA512_DIGEST_STRING_LENGTH = (SHA512_DIGEST_LENGTH * 2 + 1);


/*** SHA-256/384/512 Context Structures *******************************/
typedef struct _SHA256_CTX {
	uint32_t	state[8];
	uint64_t	bitcount;
	uint8_t	buffer[SHA256_BLOCK_LENGTH];
} SHA256_CTX;
typedef struct _SHA512_CTX {
	uint64_t	state[8];
	uint64_t	bitcount[2];
	uint8_t	buffer[SHA512_BLOCK_LENGTH];
} SHA512_CTX;

typedef SHA512_CTX SHA384_CTX;


/*
 * UNROLLED TRANSFORM LOOP NOTE:
 * You can define SHA2_UNROLL_TRANSFORM to use the unrolled transform
 * loop version for the hash transform rounds (defined using macros
 * later in this file).  Either define on the command line, for example:
 *
 *   cc -DSHA2_UNROLL_TRANSFORM -o sha2 sha2.c sha2prog.c
 *
 * or define below:
 *
 *   #define SHA2_UNROLL_TRANSFORM
 *
 */

/*** SHA-256/384/512 Machine Architecture Definitions *****************/
/*
 * BYTE_ORDER NOTE:
 *
 * Please make sure that your system defines BYTE_ORDER.  If your
 * architecture is little-endian, make sure it also defines
 * LITTLE_ENDIAN and that the two (BYTE_ORDER and LITTLE_ENDIAN) are
 * equivalent.
 *
 * If your system does not define the above, then you can do so by
 * hand like this:
 *
 *   #define LITTLE_ENDIAN 1234
 *   #define BIG_ENDIAN    4321
 *
 * And for little-endian machines, add:
 *
 *   #define BYTE_ORDER LITTLE_ENDIAN
 *
 * Or for big-endian machines:
 *
 *   #define BYTE_ORDER BIG_ENDIAN
 *
 * The FreeBSD machine this was written on defines BYTE_ORDER
 * appropriately by including <sys/types.h> (which in turn includes
 * <machine/endian.h> where the appropriate definitions are actually
 * made).
 */
#if !defined(BYTE_ORDER) || (BYTE_ORDER != LITTLE_ENDIAN && BYTE_ORDER != BIG_ENDIAN)
#error Define BYTE_ORDER to be equal to either LITTLE_ENDIAN or BIG_ENDIAN
#endif


/*** SHA-256/384/512 Various Length Definitions ***********************/
static const constexpr int SHA256_SHORT_BLOCK_LENGTH = (SHA256_BLOCK_LENGTH - 8);
static const constexpr int SHA384_SHORT_BLOCK_LENGTH = (SHA384_BLOCK_LENGTH - 16);
static const constexpr int SHA512_SHORT_BLOCK_LENGTH = (SHA512_BLOCK_LENGTH - 16);

/*** ENDIAN SPECIFIC COPY MACROS **************************************/
inline void BE_8_TO_32( uint32_t& dst, const uint8_t *cp ) {
	dst = static_cast< uint32_t >( cp[ 3 ] ) | (static_cast< uint32_t >( cp[ 2 ] ) << 8) |
	    (static_cast< uint32_t >( cp[ 1 ] ) << 16) | (static_cast< uint32_t >( cp[ 0 ] ) << 24);
}

inline void BE_8_TO_64( uint64_t& dst, const uint8_t *cp ) {					\
	dst = static_cast< uint64_t >( cp[ 7 ] ) | (static_cast< uint64_t >( cp[ 6 ] ) << 8) |
	    (static_cast< uint64_t >( cp[ 5 ] ) << 16) | (static_cast< uint64_t >( cp[ 4 ] ) << 24) |
	    (static_cast< uint64_t >( cp[ 3 ] ) << 32) | (static_cast< uint64_t >( cp[ 2 ] ) << 40) |
	    (static_cast< uint64_t >( cp[ 1 ] ) << 48) | (static_cast< uint64_t >( cp[ 0 ] ) << 56);
}

inline void BE_64_TO_8( uint8_t *cp, uint64_t src ) {					\
	(cp)[0] = (src) >> 56;
    (cp)[1] = (src) >> 48;
	(cp)[2] = (src) >> 40;
	(cp)[3] = (src) >> 32;
	(cp)[4] = (src) >> 24;
	(cp)[5] = (src) >> 16;
	(cp)[6] = (src) >> 8;
	(cp)[7] = (src);
}

inline void BE_32_TO_8( uint8_t *cp, uint32_t src ) {
	(cp)[0] = (src) >> 24;
	(cp)[1] = (src) >> 16;
	(cp)[2] = (src) >> 8;
	(cp)[3] = (src);
}

/*
 * Macro for incrementally adding the unsigned 64-bit integer n to the
 * unsigned 128-bit integer (represented using a two-element array of
 * 64-bit words):
 */
inline void ADDINC128( uint64_t *w, uint64_t n) {						\
	(w)[0] += n;
	if ((w)[0] < (n)) {
		(w)[1]++;
	}
}

/*** THE SIX LOGICAL FUNCTIONS ****************************************/
/*
 * Bit shifting and rotation (used by the six SHA-XYZ logical functions:
 *
 *   NOTE:  The naming of R and S appears backwards here (R is a SHIFT and
 *   S is a ROTATION) because the SHA-256/384/512 description document
 *   (see http://csrc.nist.gov/cryptval/shs/sha256-384-512.pdf) uses this
 *   same "backwards" definition.
 */
/* Shift-right (used in SHA-256, SHA-384, and SHA-512): */
template < typename T >
inline T R( int b, T x ) { return x >> b; }
/* 32-bit Rotate-right (used in SHA-256): */
inline uint32_t S32( int b, uint32_t x )	{
    return ((x) >> (b)) | ((x) << (32 - (b)));
}
/* 64-bit Rotate-right (used in SHA-384 and SHA-512): */
inline uint64_t S64( int b, uint64_t x )	{
	return ((x) >> (b)) | ((x) << (64 - (b)));
}

/* Two of six logical functions used in SHA-256, SHA-384, and SHA-512: */
template < typename T >
inline T Ch( T x, T y, T z) {
	return ((x) & (y)) ^ ((~(x)) & (z));
}
template < typename T >
inline T Maj( T x, T y, T z ) {
	return ((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z));
}

/* Four of six logical functions used in SHA-256: */
inline uint32_t Sigma0_256( uint32_t x ) { return S32(2,  (x)) ^ S32(13, (x)) ^ S32(22, (x)); }
inline uint32_t Sigma1_256( uint32_t x ) { return S32(6,  (x)) ^ S32(11, (x)) ^ S32(25, (x)); }
inline uint32_t sigma0_256( uint32_t x ) { return S32(7,  (x)) ^ S32(18, (x)) ^ R(3 ,   (x)); }
inline uint32_t sigma1_256( uint32_t x ) { return S32(17, (x)) ^ S32(19, (x)) ^ R(10,   (x)); }

/* Four of six logical functions used in SHA-384 and SHA-512: */
inline uint64_t Sigma0_512( uint64_t x ) { return S64(28, (x)) ^ S64(34, (x)) ^ S64(39, (x)); }
inline uint64_t Sigma1_512( uint64_t x ) { return S64(14, (x)) ^ S64(18, (x)) ^ S64(41, (x)); }
inline uint64_t sigma0_512( uint64_t x ) { return S64( 1, (x)) ^ S64( 8, (x)) ^ R( 7,   (x)); }
inline uint64_t sigma1_512( uint64_t x ) { return S64(19, (x)) ^ S64(61, (x)) ^ R( 6,   (x)); }


/*** SHA-XYZ INITIAL HASH VALUES AND CONSTANTS ************************/
/* Hash constant words K for SHA-256: */
const static uint32_t K256[64] = {
	0x428a2f98UL, 0x71374491UL, 0xb5c0fbcfUL, 0xe9b5dba5UL,
	0x3956c25bUL, 0x59f111f1UL, 0x923f82a4UL, 0xab1c5ed5UL,
	0xd807aa98UL, 0x12835b01UL, 0x243185beUL, 0x550c7dc3UL,
	0x72be5d74UL, 0x80deb1feUL, 0x9bdc06a7UL, 0xc19bf174UL,
	0xe49b69c1UL, 0xefbe4786UL, 0x0fc19dc6UL, 0x240ca1ccUL,
	0x2de92c6fUL, 0x4a7484aaUL, 0x5cb0a9dcUL, 0x76f988daUL,
	0x983e5152UL, 0xa831c66dUL, 0xb00327c8UL, 0xbf597fc7UL,
	0xc6e00bf3UL, 0xd5a79147UL, 0x06ca6351UL, 0x14292967UL,
	0x27b70a85UL, 0x2e1b2138UL, 0x4d2c6dfcUL, 0x53380d13UL,
	0x650a7354UL, 0x766a0abbUL, 0x81c2c92eUL, 0x92722c85UL,
	0xa2bfe8a1UL, 0xa81a664bUL, 0xc24b8b70UL, 0xc76c51a3UL,
	0xd192e819UL, 0xd6990624UL, 0xf40e3585UL, 0x106aa070UL,
	0x19a4c116UL, 0x1e376c08UL, 0x2748774cUL, 0x34b0bcb5UL,
	0x391c0cb3UL, 0x4ed8aa4aUL, 0x5b9cca4fUL, 0x682e6ff3UL,
	0x748f82eeUL, 0x78a5636fUL, 0x84c87814UL, 0x8cc70208UL,
	0x90befffaUL, 0xa4506cebUL, 0xbef9a3f7UL, 0xc67178f2UL
};

/* Initial hash value H for SHA-256: */
const static uint32_t sha256_initial_hash_value[8] = {
	0x6a09e667UL,
	0xbb67ae85UL,
	0x3c6ef372UL,
	0xa54ff53aUL,
	0x510e527fUL,
	0x9b05688cUL,
	0x1f83d9abUL,
	0x5be0cd19UL
};

/* Hash constant words K for SHA-384 and SHA-512: */
const static uint64_t K512[80] = {
	0x428a2f98d728ae22ULL, 0x7137449123ef65cdULL,
	0xb5c0fbcfec4d3b2fULL, 0xe9b5dba58189dbbcULL,
	0x3956c25bf348b538ULL, 0x59f111f1b605d019ULL,
	0x923f82a4af194f9bULL, 0xab1c5ed5da6d8118ULL,
	0xd807aa98a3030242ULL, 0x12835b0145706fbeULL,
	0x243185be4ee4b28cULL, 0x550c7dc3d5ffb4e2ULL,
	0x72be5d74f27b896fULL, 0x80deb1fe3b1696b1ULL,
	0x9bdc06a725c71235ULL, 0xc19bf174cf692694ULL,
	0xe49b69c19ef14ad2ULL, 0xefbe4786384f25e3ULL,
	0x0fc19dc68b8cd5b5ULL, 0x240ca1cc77ac9c65ULL,
	0x2de92c6f592b0275ULL, 0x4a7484aa6ea6e483ULL,
	0x5cb0a9dcbd41fbd4ULL, 0x76f988da831153b5ULL,
	0x983e5152ee66dfabULL, 0xa831c66d2db43210ULL,
	0xb00327c898fb213fULL, 0xbf597fc7beef0ee4ULL,
	0xc6e00bf33da88fc2ULL, 0xd5a79147930aa725ULL,
	0x06ca6351e003826fULL, 0x142929670a0e6e70ULL,
	0x27b70a8546d22ffcULL, 0x2e1b21385c26c926ULL,
	0x4d2c6dfc5ac42aedULL, 0x53380d139d95b3dfULL,
	0x650a73548baf63deULL, 0x766a0abb3c77b2a8ULL,
	0x81c2c92e47edaee6ULL, 0x92722c851482353bULL,
	0xa2bfe8a14cf10364ULL, 0xa81a664bbc423001ULL,
	0xc24b8b70d0f89791ULL, 0xc76c51a30654be30ULL,
	0xd192e819d6ef5218ULL, 0xd69906245565a910ULL,
	0xf40e35855771202aULL, 0x106aa07032bbd1b8ULL,
	0x19a4c116b8d2d0c8ULL, 0x1e376c085141ab53ULL,
	0x2748774cdf8eeb99ULL, 0x34b0bcb5e19b48a8ULL,
	0x391c0cb3c5c95a63ULL, 0x4ed8aa4ae3418acbULL,
	0x5b9cca4f7763e373ULL, 0x682e6ff3d6b2b8a3ULL,
	0x748f82ee5defb2fcULL, 0x78a5636f43172f60ULL,
	0x84c87814a1f0ab72ULL, 0x8cc702081a6439ecULL,
	0x90befffa23631e28ULL, 0xa4506cebde82bde9ULL,
	0xbef9a3f7b2c67915ULL, 0xc67178f2e372532bULL,
	0xca273eceea26619cULL, 0xd186b8c721c0c207ULL,
	0xeada7dd6cde0eb1eULL, 0xf57d4f7fee6ed178ULL,
	0x06f067aa72176fbaULL, 0x0a637dc5a2c898a6ULL,
	0x113f9804bef90daeULL, 0x1b710b35131c471bULL,
	0x28db77f523047d84ULL, 0x32caab7b40c72493ULL,
	0x3c9ebe0a15c9bebcULL, 0x431d67c49c100d4cULL,
	0x4cc5d4becb3e42b6ULL, 0x597f299cfc657e2aULL,
	0x5fcb6fab3ad6faecULL, 0x6c44198c4a475817ULL
};

/* Initial hash value H for SHA-384 */
const static uint64_t sha384_initial_hash_value[8] = {
	0xcbbb9d5dc1059ed8ULL,
	0x629a292a367cd507ULL,
	0x9159015a3070dd17ULL,
	0x152fecd8f70e5939ULL,
	0x67332667ffc00b31ULL,
	0x8eb44a8768581511ULL,
	0xdb0c2e0d64f98fa7ULL,
	0x47b5481dbefa4fa4ULL
};

/* Initial hash value H for SHA-512 */
const static uint64_t sha512_initial_hash_value[8] = {
	0x6a09e667f3bcc908ULL,
	0xbb67ae8584caa73bULL,
	0x3c6ef372fe94f82bULL,
	0xa54ff53a5f1d36f1ULL,
	0x510e527fade682d1ULL,
	0x9b05688c2b3e6c1fULL,
	0x1f83d9abfb41bd6bULL,
	0x5be0cd19137e2179ULL
};


/*** SHA-256: *********************************************************/
static void
SHA256_Init(SHA256_CTX *context)
{
	if (context == NULL)
		return;
	memcpy(context->state, sha256_initial_hash_value,
	    sizeof(sha256_initial_hash_value));
	memset(context->buffer, 0, sizeof(context->buffer));
	context->bitcount = 0;
}

#ifdef SHA2_UNROLL_TRANSFORM

/* Unrolled SHA-256 round macros: */

#define ROUND256_0_TO_15(a,b,c,d,e,f,g,h) do {				    \
	BE_8_TO_32(W256[j], data);					    \
	data += 4;							    \
	T1 = (h) + Sigma1_256((e)) + Ch((e), (f), (g)) + K256[j] + W256[j]; \
	(d) += T1;							    \
	(h) = T1 + Sigma0_256((a)) + Maj((a), (b), (c));		    \
	j++;								    \
} while(0)

#define ROUND256(a,b,c,d,e,f,g,h) do {					    \
	s0 = W256[(j+1)&0x0f];						    \
	s0 = sigma0_256(s0);						    \
	s1 = W256[(j+14)&0x0f];						    \
	s1 = sigma1_256(s1);						    \
	T1 = (h) + Sigma1_256((e)) + Ch((e), (f), (g)) + K256[j] +	    \
	     (W256[j&0x0f] += s1 + W256[(j+9)&0x0f] + s0);		    \
	(d) += T1;							    \
	(h) = T1 + Sigma0_256((a)) + Maj((a), (b), (c));		    \
	j++;								    \
} while(0)

void
SHA256_Transform(uint32_t state[8], const uint8_t data[SHA256_BLOCK_LENGTH])
{
	uint32_t	a, b, c, d, e, f, g, h, s0, s1;
	uint32_t	T1, W256[16];
	int		j;

	/* Initialize registers with the prev. intermediate value */
	a = state[0];
	b = state[1];
	c = state[2];
	d = state[3];
	e = state[4];
	f = state[5];
	g = state[6];
	h = state[7];

	j = 0;
	do {
		/* Rounds 0 to 15 (unrolled): */
		ROUND256_0_TO_15(a,b,c,d,e,f,g,h);
		ROUND256_0_TO_15(h,a,b,c,d,e,f,g);
		ROUND256_0_TO_15(g,h,a,b,c,d,e,f);
		ROUND256_0_TO_15(f,g,h,a,b,c,d,e);
		ROUND256_0_TO_15(e,f,g,h,a,b,c,d);
		ROUND256_0_TO_15(d,e,f,g,h,a,b,c);
		ROUND256_0_TO_15(c,d,e,f,g,h,a,b);
		ROUND256_0_TO_15(b,c,d,e,f,g,h,a);
	} while (j < 16);

	/* Now for the remaining rounds up to 63: */
	do {
		ROUND256(a,b,c,d,e,f,g,h);
		ROUND256(h,a,b,c,d,e,f,g);
		ROUND256(g,h,a,b,c,d,e,f);
		ROUND256(f,g,h,a,b,c,d,e);
		ROUND256(e,f,g,h,a,b,c,d);
		ROUND256(d,e,f,g,h,a,b,c);
		ROUND256(c,d,e,f,g,h,a,b);
		ROUND256(b,c,d,e,f,g,h,a);
	} while (j < 64);

	/* Compute the current intermediate hash value */
	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;
	state[4] += e;
	state[5] += f;
	state[6] += g;
	state[7] += h;

	/* Clean up */
	a = b = c = d = e = f = g = h = T1 = 0;
}

#else /* SHA2_UNROLL_TRANSFORM */

static void
SHA256_Transform(uint32_t state[8], const uint8_t data[SHA256_BLOCK_LENGTH])
{
	uint32_t	a, b, c, d, e, f, g, h, s0, s1;
	uint32_t	T1, T2, W256[16];
	int		j;

	/* Initialize registers with the prev. intermediate value */
	a = state[0];
	b = state[1];
	c = state[2];
	d = state[3];
	e = state[4];
	f = state[5];
	g = state[6];
	h = state[7];

	j = 0;
	do {
		BE_8_TO_32(W256[j], data);
		data += 4;
		/* Apply the SHA-256 compression function to update a..h */
		T1 = h + Sigma1_256(e) + Ch(e, f, g) + K256[j] + W256[j];
		T2 = Sigma0_256(a) + Maj(a, b, c);
		h = g;
		g = f;
		f = e;
		e = d + T1;
		d = c;
		c = b;
		b = a;
		a = T1 + T2;

		j++;
	} while (j < 16);

	do {
		/* Part of the message block expansion: */
		s0 = W256[(j+1)&0x0f];
		s0 = sigma0_256(s0);
		s1 = W256[(j+14)&0x0f];
		s1 = sigma1_256(s1);

		/* Apply the SHA-256 compression function to update a..h */
		T1 = h + Sigma1_256(e) + Ch(e, f, g) + K256[j] +
		     (W256[j&0x0f] += s1 + W256[(j+9)&0x0f] + s0);
		T2 = Sigma0_256(a) + Maj(a, b, c);
		h = g;
		g = f;
		f = e;
		e = d + T1;
		d = c;
		c = b;
		b = a;
		a = T1 + T2;

		j++;
	} while (j < 64);

	/* Compute the current intermediate hash value */
	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;
	state[4] += e;
	state[5] += f;
	state[6] += g;
	state[7] += h;

	/* Clean up */
	a = b = c = d = e = f = g = h = T1 = T2 = 0;
}

#endif /* SHA2_UNROLL_TRANSFORM */

static void
SHA256_Update(SHA256_CTX *context, const uint8_t *data, size_t len)
{
	size_t	freespace, usedspace;

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

	usedspace = (context->bitcount >> 3) % SHA256_BLOCK_LENGTH;
	if (usedspace > 0) {
		/* Calculate how much free space is available in the buffer */
		freespace = SHA256_BLOCK_LENGTH - usedspace;

		if (len >= freespace) {
			/* Fill the buffer completely and process it */
			memcpy(&context->buffer[usedspace], data, freespace);
			context->bitcount += freespace << 3;
			len -= freespace;
			data += freespace;
			SHA256_Transform(context->state, context->buffer);
		} else {
			/* The buffer is not yet full */
			memcpy(&context->buffer[usedspace], data, len);
			context->bitcount += len << 3;
			/* Clean up: */
			usedspace = freespace = 0;
			return;
		}
	}
	while (len >= SHA256_BLOCK_LENGTH) {
		/* Process as many complete blocks as we can */
		SHA256_Transform(context->state, data);
		context->bitcount += SHA256_BLOCK_LENGTH << 3;
		len -= SHA256_BLOCK_LENGTH;
		data += SHA256_BLOCK_LENGTH;
	}
	if (len > 0) {
		/* There's left-overs, so save 'em */
		memcpy(context->buffer, data, len);
		context->bitcount += len << 3;
	}
	/* Clean up: */
	usedspace = freespace = 0;
}

static void
SHA256_Pad(SHA256_CTX *context)
{
	unsigned int	usedspace;

	usedspace = (context->bitcount >> 3) % SHA256_BLOCK_LENGTH;
	if (usedspace > 0) {
		/* Begin padding with a 1 bit: */
		context->buffer[usedspace++] = 0x80;

		if (usedspace <= SHA256_SHORT_BLOCK_LENGTH) {
			/* Set-up for the last transform: */
			memset(&context->buffer[usedspace], 0,
			    SHA256_SHORT_BLOCK_LENGTH - usedspace);
		} else {
			if (usedspace < SHA256_BLOCK_LENGTH) {
				memset(&context->buffer[usedspace], 0,
				    SHA256_BLOCK_LENGTH - usedspace);
			}
			/* Do second-to-last transform: */
			SHA256_Transform(context->state, context->buffer);

			/* Prepare for last transform: */
			memset(context->buffer, 0, SHA256_SHORT_BLOCK_LENGTH);
		}
	} else {
		/* Set-up for the last transform: */
		memset(context->buffer, 0, SHA256_SHORT_BLOCK_LENGTH);

		/* Begin padding with a 1 bit: */
		*context->buffer = 0x80;
	}
	/* Store the length of input data (in bits) in big endian format: */
	BE_64_TO_8(&context->buffer[SHA256_SHORT_BLOCK_LENGTH],
	    context->bitcount);

	/* Final transform: */
	SHA256_Transform(context->state, context->buffer);

	/* Clean up: */
	usedspace = 0;
}

static void
SHA256_Final(uint8_t digest[SHA256_DIGEST_LENGTH], SHA256_CTX *context)
{
	SHA256_Pad(context);

	/* If no digest buffer is passed, we don't bother doing this: */
	if (digest != NULL) {
#if BYTE_ORDER == LITTLE_ENDIAN
		int	i;

		/* Convert TO host byte order */
		for (i = 0; i < 8; i++)
			BE_32_TO_8(digest + i * 4, context->state[i]);
#else
		memcpy(digest, context->state, SHA256_DIGEST_LENGTH);
#endif
		memset(context, 0, sizeof(*context));
	}
}


/*** SHA-512: *********************************************************/
static void
SHA512_Init(SHA512_CTX *context)
{
	if (context == NULL)
		return;
	memcpy(context->state, sha512_initial_hash_value,
	    sizeof(sha512_initial_hash_value));
	memset(context->buffer, 0, sizeof(context->buffer));
	context->bitcount[0] = context->bitcount[1] =  0;
}

#ifdef SHA2_UNROLL_TRANSFORM

/* Unrolled SHA-512 round macros: */

#define ROUND512_0_TO_15(a,b,c,d,e,f,g,h) do {				    \
	BE_8_TO_64(W512[j], data);					    \
	data += 8;							    \
	T1 = (h) + Sigma1_512((e)) + Ch((e), (f), (g)) + K512[j] + W512[j]; \
	(d) += T1;							    \
	(h) = T1 + Sigma0_512((a)) + Maj((a), (b), (c));		    \
	j++;								    \
} while(0)


#define ROUND512(a,b,c,d,e,f,g,h) do {					    \
	s0 = W512[(j+1)&0x0f];						    \
	s0 = sigma0_512(s0);						    \
	s1 = W512[(j+14)&0x0f];						    \
	s1 = sigma1_512(s1);						    \
	T1 = (h) + Sigma1_512((e)) + Ch((e), (f), (g)) + K512[j] +	    \
             (W512[j&0x0f] += s1 + W512[(j+9)&0x0f] + s0);		    \
	(d) += T1;							    \
	(h) = T1 + Sigma0_512((a)) + Maj((a), (b), (c));		    \
	j++;								    \
} while(0)

void
SHA512_Transform(uint64_t state[8], const uint8_t data[SHA512_BLOCK_LENGTH])
{
	uint64_t	a, b, c, d, e, f, g, h, s0, s1;
	uint64_t	T1, W512[16];
	int		j;

	/* Initialize registers with the prev. intermediate value */
	a = state[0];
	b = state[1];
	c = state[2];
	d = state[3];
	e = state[4];
	f = state[5];
	g = state[6];
	h = state[7];

	j = 0;
	do {
		/* Rounds 0 to 15 (unrolled): */
		ROUND512_0_TO_15(a,b,c,d,e,f,g,h);
		ROUND512_0_TO_15(h,a,b,c,d,e,f,g);
		ROUND512_0_TO_15(g,h,a,b,c,d,e,f);
		ROUND512_0_TO_15(f,g,h,a,b,c,d,e);
		ROUND512_0_TO_15(e,f,g,h,a,b,c,d);
		ROUND512_0_TO_15(d,e,f,g,h,a,b,c);
		ROUND512_0_TO_15(c,d,e,f,g,h,a,b);
		ROUND512_0_TO_15(b,c,d,e,f,g,h,a);
	} while (j < 16);

	/* Now for the remaining rounds up to 79: */
	do {
		ROUND512(a,b,c,d,e,f,g,h);
		ROUND512(h,a,b,c,d,e,f,g);
		ROUND512(g,h,a,b,c,d,e,f);
		ROUND512(f,g,h,a,b,c,d,e);
		ROUND512(e,f,g,h,a,b,c,d);
		ROUND512(d,e,f,g,h,a,b,c);
		ROUND512(c,d,e,f,g,h,a,b);
		ROUND512(b,c,d,e,f,g,h,a);
	} while (j < 80);

	/* Compute the current intermediate hash value */
	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;
	state[4] += e;
	state[5] += f;
	state[6] += g;
	state[7] += h;

	/* Clean up */
	a = b = c = d = e = f = g = h = T1 = 0;
}

#else /* SHA2_UNROLL_TRANSFORM */

static void
SHA512_Transform(uint64_t state[8], const uint8_t data[SHA512_BLOCK_LENGTH])
{
	uint64_t	a, b, c, d, e, f, g, h, s0, s1;
	uint64_t	T1, T2, W512[16];
	int		j;

	/* Initialize registers with the prev. intermediate value */
	a = state[0];
	b = state[1];
	c = state[2];
	d = state[3];
	e = state[4];
	f = state[5];
	g = state[6];
	h = state[7];

	j = 0;
	do {
		BE_8_TO_64(W512[j], data);
		data += 8;
		/* Apply the SHA-512 compression function to update a..h */
		T1 = h + Sigma1_512(e) + Ch(e, f, g) + K512[j] + W512[j];
		T2 = Sigma0_512(a) + Maj(a, b, c);
		h = g;
		g = f;
		f = e;
		e = d + T1;
		d = c;
		c = b;
		b = a;
		a = T1 + T2;

		j++;
	} while (j < 16);

	do {
		/* Part of the message block expansion: */
		s0 = W512[(j+1)&0x0f];
		s0 = sigma0_512(s0);
		s1 = W512[(j+14)&0x0f];
		s1 =  sigma1_512(s1);

		/* Apply the SHA-512 compression function to update a..h */
		T1 = h + Sigma1_512(e) + Ch(e, f, g) + K512[j] +
		     (W512[j&0x0f] += s1 + W512[(j+9)&0x0f] + s0);
		T2 = Sigma0_512(a) + Maj(a, b, c);
		h = g;
		g = f;
		f = e;
		e = d + T1;
		d = c;
		c = b;
		b = a;
		a = T1 + T2;

		j++;
	} while (j < 80);

	/* Compute the current intermediate hash value */
	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;
	state[4] += e;
	state[5] += f;
	state[6] += g;
	state[7] += h;

	/* Clean up */
	a = b = c = d = e = f = g = h = T1 = T2 = 0;
}

#endif /* SHA2_UNROLL_TRANSFORM */

static void
SHA512_Update(SHA512_CTX *context, const uint8_t *data, size_t len)
{
	size_t	freespace, usedspace;

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

	usedspace = (context->bitcount[0] >> 3) % SHA512_BLOCK_LENGTH;
	if (usedspace > 0) {
		/* Calculate how much free space is available in the buffer */
		freespace = SHA512_BLOCK_LENGTH - usedspace;

		if (len >= freespace) {
			/* Fill the buffer completely and process it */
			memcpy(&context->buffer[usedspace], data, freespace);
			ADDINC128(context->bitcount, freespace << 3);
			len -= freespace;
			data += freespace;
			SHA512_Transform(context->state, context->buffer);
		} else {
			/* The buffer is not yet full */
			memcpy(&context->buffer[usedspace], data, len);
			ADDINC128(context->bitcount, len << 3);
			/* Clean up: */
			usedspace = freespace = 0;
			return;
		}
	}
	while (len >= SHA512_BLOCK_LENGTH) {
		/* Process as many complete blocks as we can */
		SHA512_Transform(context->state, data);
		ADDINC128(context->bitcount, SHA512_BLOCK_LENGTH << 3);
		len -= SHA512_BLOCK_LENGTH;
		data += SHA512_BLOCK_LENGTH;
	}
	if (len > 0) {
		/* There's left-overs, so save 'em */
		memcpy(context->buffer, data, len);
		ADDINC128(context->bitcount, len << 3);
	}
	/* Clean up: */
	usedspace = freespace = 0;
}

static void
SHA512_Pad(SHA512_CTX *context)
{
	unsigned int	usedspace;

	usedspace = (context->bitcount[0] >> 3) % SHA512_BLOCK_LENGTH;
	if (usedspace > 0) {
		/* Begin padding with a 1 bit: */
		context->buffer[usedspace++] = 0x80;

		if (usedspace <= SHA512_SHORT_BLOCK_LENGTH) {
			/* Set-up for the last transform: */
			memset(&context->buffer[usedspace], 0, SHA512_SHORT_BLOCK_LENGTH - usedspace);
		} else {
			if (usedspace < SHA512_BLOCK_LENGTH) {
				memset(&context->buffer[usedspace], 0, SHA512_BLOCK_LENGTH - usedspace);
			}
			/* Do second-to-last transform: */
			SHA512_Transform(context->state, context->buffer);

			/* And set-up for the last transform: */
			memset(context->buffer, 0, SHA512_BLOCK_LENGTH - 2);
		}
	} else {
		/* Prepare for final transform: */
		memset(context->buffer, 0, SHA512_SHORT_BLOCK_LENGTH);

		/* Begin padding with a 1 bit: */
		*context->buffer = 0x80;
	}
	/* Store the length of input data (in bits) in big endian format: */
	BE_64_TO_8(&context->buffer[SHA512_SHORT_BLOCK_LENGTH],
	    context->bitcount[1]);
	BE_64_TO_8(&context->buffer[SHA512_SHORT_BLOCK_LENGTH + 8],
	    context->bitcount[0]);

	/* Final transform: */
	SHA512_Transform(context->state, context->buffer);

	/* Clean up: */
	usedspace = 0;
}

static void
SHA512_Final(uint8_t digest[SHA512_DIGEST_LENGTH], SHA512_CTX *context)
{
	SHA512_Pad(context);

	/* If no digest buffer is passed, we don't bother doing this: */
	if (digest != NULL) {
#if BYTE_ORDER == LITTLE_ENDIAN
		int	i;

		/* Convert TO host byte order */
		for (i = 0; i < 8; i++)
			BE_64_TO_8(digest + i * 8, context->state[i]);
#else
		memcpy(digest, context->state, SHA512_DIGEST_LENGTH);
#endif
		memset(context, 0, sizeof(*context));
	}
}


#if 0
/*** SHA-384: *********************************************************/
void
SHA384_Init(SHA384_CTX *context)
{
	if (context == NULL)
		return;
	memcpy(context->state, sha384_initial_hash_value,
	    sizeof(sha384_initial_hash_value));
	memset(context->buffer, 0, sizeof(context->buffer));
	context->bitcount[0] = context->bitcount[1] = 0;
}

__weak_alias(SHA384_Transform, SHA512_Transform);
__weak_alias(SHA384_Update, SHA512_Update);
__weak_alias(SHA384_Pad, SHA512_Pad);

void
SHA384_Final(uint8_t digest[SHA384_DIGEST_LENGTH], SHA384_CTX *context)
{
	SHA384_Pad(context);

	/* If no digest buffer is passed, we don't bother doing this: */
	if (digest != NULL) {
#if BYTE_ORDER == LITTLE_ENDIAN
		int	i;

		/* Convert TO host byte order */
		for (i = 0; i < 6; i++)
			BE_64_TO_8(digest + i * 8, context->state[i]);
#else
		memcpy(digest, context->state, SHA384_DIGEST_LENGTH);
#endif
	}

	/* Zero out state data */
	memset(context, 0, sizeof(*context));
}
#endif

// #ifdef DIVINE_RELAX_WARNINGS
// DIVINE_UNRELAX_WARNINGS
// #endif

} // namespace detail

inline auto sha2_256( std::string_view s )
{
    using namespace detail;
    _SHA256_CTX ctx;
    SHA256_Init( &ctx );
    SHA256_Update( &ctx, reinterpret_cast< const uint8_t* >( s.data() ), s.size() );
    std::array< uint8_t, 32 > r;
    SHA256_Final( r.begin(), &ctx );
    return r;
}

inline auto sha2_512( const std::string& s )
{
    using namespace detail;
    _SHA512_CTX ctx;
    SHA512_Init( &ctx );
    SHA512_Update( &ctx, reinterpret_cast< const uint8_t* >( s.data() ), s.size() );
    std::array< uint8_t, 64 > r;
    SHA512_Final( r.begin(), &ctx );
    return r;
}

template< typename T >
auto to_hex( const T &hash ) -> std::enable_if_t< sizeof( *hash.begin() ) == 1, std::string >
{
    brq::string_builder s;
    s.hex();
    for ( char x : hash )
        s << brq::pad( 2, '0' ) << static_cast< unsigned int >( x & 0xff ) << brq::mark;
    if ( s.truncated() )
        throw std::bad_alloc();
    return s.buffer();
}

}

namespace t_brq
{
    struct sha2
    {
        // http://www.di-mgt.com.au/sha_testvectors.html

        TEST(abc)
        {
            std::string input = "abc";
            std::string output_256
            { 
                "\xba\x78\x16\xbf\x8f\x01\xcf\xea\x41\x41\x40\xde\x5d\xae\x22\x23"
                "\xb0\x03\x61\xa3\x96\x17\x7a\x9c\xb4\x10\xff\x61\xf2\x00\x15\xad",
                brq::detail::SHA256_DIGEST_LENGTH
            };
            std::string output_512
            {
                "\xdd\xaf\x35\xa1\x93\x61\x7a\xba\xcc\x41\x73\x49\xae\x20\x41\x31"
                "\x12\xe6\xfa\x4e\x89\xa9\x7e\xa2\x0a\x9e\xee\xe6\x4b\x55\xd3\x9a"
                "\x21\x92\x99\x2a\x27\x4f\xc1\xa8\x36\xba\x3c\x23\xa3\xfe\xeb\xbd"
                "\x45\x4d\x44\x23\x64\x3c\xe8\x0e\x2a\x9a\xc9\x4f\xa5\x4c\xa4\x9f",
                brq::detail::SHA512_DIGEST_LENGTH
            };
            ASSERT_EQ( brq::to_hex( brq::sha2_256( input ) ), brq::to_hex( output_256 ) );
            ASSERT_EQ( brq::to_hex( brq::sha2_512( input ) ), brq::to_hex( output_512 ) );
        }

        TEST(empty)
        {
            std::string input;
            std::string output_256
            {
                "\xe3\xb0\xc4\x42\x98\xfc\x1c\x14\x9a\xfb\xf4\xc8\x99\x6f\xb9\x24"
                "\x27\xae\x41\xe4\x64\x9b\x93\x4c\xa4\x95\x99\x1b\x78\x52\xb8\x55",
                brq::detail::SHA256_DIGEST_LENGTH
            };

            std::string output_512
            {
                "\xcf\x83\xe1\x35\x7e\xef\xb8\xbd\xf1\x54\x28\x50\xd6\x6d\x80\x07"
                "\xd6\x20\xe4\x05\x0b\x57\x15\xdc\x83\xf4\xa9\x21\xd3\x6c\xe9\xce"
                "\x47\xd0\xd1\x3c\x5d\x85\xf2\xb0\xff\x83\x18\xd2\x87\x7e\xec\x2f"
                "\x63\xb9\x31\xbd\x47\x41\x7a\x81\xa5\x38\x32\x7a\xf9\x27\xda\x3e",
                brq::detail::SHA512_DIGEST_LENGTH
            };
            ASSERT_EQ( brq::to_hex( brq::sha2_256( input ) ), brq::to_hex( output_256 ) );
            ASSERT_EQ( brq::to_hex( brq::sha2_512( input ) ), brq::to_hex( output_512 ) );
        }
    };
}

// vim: syntax=cpp tabstop=4 shiftwidth=4 expandtab ft=cpp