// SPDX-License-Identifier: 0BSD

/*
 * SHA-256
 *
 * This is based on the XZ Utils version which is based public domain code
 * from Crypto++ Library 5.5.1 released in 2007: https://www.cryptopp.com/
 *
 * Authors: Wei Dai
 *          Lasse Collin <lasse.collin@tukaani.org>
 */

#include "xz_private.h"

static inline uint32_t
rotr_32(uint32_t num, unsigned amount)
{
	return (num >> amount) | (num << (32 - amount));
}

#define blk0(i) (W[i] = get_be32(&data[4 * i]))
#define blk2(i) (W[i & 15] += s1(W[(i - 2) & 15]) + W[(i - 7) & 15] \
		+ s0(W[(i - 15) & 15]))

#define Ch(x, y, z) (z ^ (x & (y ^ z)))
#define Maj(x, y, z) ((x & (y ^ z)) + (y & z))

#define a(i) T[(0 - i) & 7]
#define b(i) T[(1 - i) & 7]
#define c(i) T[(2 - i) & 7]
#define d(i) T[(3 - i) & 7]
#define e(i) T[(4 - i) & 7]
#define f(i) T[(5 - i) & 7]
#define g(i) T[(6 - i) & 7]
#define h(i) T[(7 - i) & 7]

#define R(i, j, blk) \
	h(i) += S1(e(i)) + Ch(e(i), f(i), g(i)) + SHA256_K[i + j] + blk; \
	d(i) += h(i); \
	h(i) += S0(a(i)) + Maj(a(i), b(i), c(i))
#define R0(i) R(i, 0, blk0(i))
#define R2(i) R(i, j, blk2(i))

#define S0(x) rotr_32(x ^ rotr_32(x ^ rotr_32(x, 9), 11), 2)
#define S1(x) rotr_32(x ^ rotr_32(x ^ rotr_32(x, 14), 5), 6)
#define s0(x) (rotr_32(x ^ rotr_32(x, 11), 7) ^ (x >> 3))
#define s1(x) (rotr_32(x ^ rotr_32(x, 2), 17) ^ (x >> 10))

static const uint32_t SHA256_K[64] = {
	0x428A2F98, 0x71374491, 0xB5C0FBCF, 0xE9B5DBA5,
	0x3956C25B, 0x59F111F1, 0x923F82A4, 0xAB1C5ED5,
	0xD807AA98, 0x12835B01, 0x243185BE, 0x550C7DC3,
	0x72BE5D74, 0x80DEB1FE, 0x9BDC06A7, 0xC19BF174,
	0xE49B69C1, 0xEFBE4786, 0x0FC19DC6, 0x240CA1CC,
	0x2DE92C6F, 0x4A7484AA, 0x5CB0A9DC, 0x76F988DA,
	0x983E5152, 0xA831C66D, 0xB00327C8, 0xBF597FC7,
	0xC6E00BF3, 0xD5A79147, 0x06CA6351, 0x14292967,
	0x27B70A85, 0x2E1B2138, 0x4D2C6DFC, 0x53380D13,
	0x650A7354, 0x766A0ABB, 0x81C2C92E, 0x92722C85,
	0xA2BFE8A1, 0xA81A664B, 0xC24B8B70, 0xC76C51A3,
	0xD192E819, 0xD6990624, 0xF40E3585, 0x106AA070,
	0x19A4C116, 0x1E376C08, 0x2748774C, 0x34B0BCB5,
	0x391C0CB3, 0x4ED8AA4A, 0x5B9CCA4F, 0x682E6FF3,
	0x748F82EE, 0x78A5636F, 0x84C87814, 0x8CC70208,
	0x90BEFFFA, 0xA4506CEB, 0xBEF9A3F7, 0xC67178F2
};

static void
transform(uint32_t state[8], const uint8_t data[64])
{
	uint32_t W[16];
	uint32_t T[8];
	unsigned int j;

	/* Copy state[] to working vars. */
	memcpy(T, state, sizeof(T));

	/* The first 16 operations unrolled */
	R0( 0); R0( 1); R0( 2); R0( 3);
	R0( 4); R0( 5); R0( 6); R0( 7);
	R0( 8); R0( 9); R0(10); R0(11);
	R0(12); R0(13); R0(14); R0(15);

	/* The remaining 48 operations partially unrolled */
	for (j = 16; j < 64; j += 16) {
		R2( 0); R2( 1); R2( 2); R2( 3);
		R2( 4); R2( 5); R2( 6); R2( 7);
		R2( 8); R2( 9); R2(10); R2(11);
		R2(12); R2(13); R2(14); R2(15);
	}

	/* Add the working vars back into state[]. */
	state[0] += a(0);
	state[1] += b(0);
	state[2] += c(0);
	state[3] += d(0);
	state[4] += e(0);
	state[5] += f(0);
	state[6] += g(0);
	state[7] += h(0);
}

XZ_EXTERN void xz_sha256_reset(struct xz_sha256 *s)
{
	static const uint32_t initial_state[8] = {
		0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A,
		0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19
	};

	memcpy(s->state, initial_state, sizeof(initial_state));
	s->size = 0;
}

XZ_EXTERN void xz_sha256_update(const uint8_t *buf, size_t size,
				struct xz_sha256 *s)
{
	size_t copy_start;
	size_t copy_size;

	/*
	 * Copy the input data into a properly aligned temporary buffer.
	 * This way we can be called with arbitrarily sized buffers
	 * (no need to be a multiple of 64 bytes).
	 *
	 * Full 64-byte chunks could be processed directly from buf with
	 * unaligned access. It seemed to make very little difference in
	 * speed on x86-64 though. Thus it was omitted.
	 */
	while (size > 0) {
		copy_start = s->size & 0x3F;
		copy_size = 64 - copy_start;
		if (copy_size > size)
			copy_size = size;

		memcpy(s->data + copy_start, buf, copy_size);

		buf += copy_size;
		size -= copy_size;
		s->size += copy_size;

		if ((s->size & 0x3F) == 0)
			transform(s->state, s->data);
	}
}

XZ_EXTERN bool xz_sha256_validate(const uint8_t *buf, struct xz_sha256 *s)
{
	/*
	 * Add padding as described in RFC 3174 (it describes SHA-1 but
	 * the same padding style is used for SHA-256 too).
	 */
	size_t i = s->size & 0x3F;
	s->data[i++] = 0x80;

	while (i != 64 - 8) {
		if (i == 64) {
			transform(s->state, s->data);
			i = 0;
		}

		s->data[i++] = 0x00;
	}

	/* Convert the message size from bytes to bits. */
	s->size *= 8;

	/*
	 * Store the message size in big endian byte order and
	 * calculate the final hash value.
	 */
	for (i = 0; i < 8; ++i)
		s->data[64 - 8 + i] = (uint8_t)(s->size >> ((7 - i) * 8));

	transform(s->state, s->data);

	/* Compare if the hash value matches the first 32 bytes in buf. */
	for (i = 0; i < 8; ++i)
		if (get_unaligned_be32(buf + 4 * i) != s->state[i])
			return false;

	return true;
}