/* Copyright (c) 2013-2025 Jeffrey Pfau
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Based on https://github.com/clibs/sha1
 *
 * Test Vectors (from FIPS PUB 180-1)
 * "abc"
 *  A9993E36 4706816A BA3E2571 7850C26C 9CD0D89D
 * "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
 *  84983E44 1C3BD26E BAAE4AA1 F95129E5 E54670F1
 * A million repetitions of "a"
 *  34AA973C D4C4DAA4 F61EEB2B DBAD2731 6534016F
 */
#include <mgba-util/sha1.h>

#include <mgba-util/vfs.h>

/* #define SHA1HANDSOFF * Copies data before messing with it. */

#define SHA1HANDSOFF

#define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))

/* blk0() and blk() perform the initial expand. */
/* I got the idea of expanding during the round function from SSLeay */
#ifndef __BIG_ENDIAN__
#define blk0(i) (block->l[i] = (rol(block->l[i],24)&0xFF00FF00) \
	|(rol(block->l[i],8)&0x00FF00FF))
#else
#define blk0(i) block->l[i]
#endif
#define blk(i) (block->l[i&15] = rol(block->l[(i+13)&15]^block->l[(i+8)&15] \
	^block->l[(i+2)&15]^block->l[i&15],1))

/* (R0+R1), R2, R3, R4 are the different operations used in SHA1 */
#define R0(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk0(i)+0x5A827999+rol(v,5);w=rol(w,30);
#define R1(v,w,x,y,z,i) z+=((w&(x^y))^y)+blk(i)+0x5A827999+rol(v,5);w=rol(w,30);
#define R2(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0x6ED9EBA1+rol(v,5);w=rol(w,30);
#define R3(v,w,x,y,z,i) z+=(((w|x)&y)|(w&x))+blk(i)+0x8F1BBCDC+rol(v,5);w=rol(w,30);
#define R4(v,w,x,y,z,i) z+=(w^x^y)+blk(i)+0xCA62C1D6+rol(v,5);w=rol(w,30);

/* Hash a single 512-bit block. This is the core of the algorithm. */
static void sha1Transform(uint32_t state[5], const uint8_t buffer[64]) {
	uint32_t a, b, c, d, e;

	typedef union {
		unsigned char c[64];
		uint32_t l[16];
	} CHAR64LONG16;

#ifdef SHA1HANDSOFF
	CHAR64LONG16 block[1];      /* use array to appear as a pointer */

	memcpy(block, buffer, 64);
#else
	/* The following had better never be used because it causes the
	 * pointer-to-const buffer to be cast into a pointer to non-const.
	 * And the result is written through.  I threw a "const" in, hoping
	 * this will cause a diagnostic.
	 */
	CHAR64LONG16 *block = (const CHAR64LONG16 *) buffer;
#endif
	/* Copy context->state[] to working vars */
	a = state[0];
	b = state[1];
	c = state[2];
	d = state[3];
	e = state[4];
	/* 4 rounds of 20 operations each. Loop unrolled. */
	R0(a, b, c, d, e, 0);
	R0(e, a, b, c, d, 1);
	R0(d, e, a, b, c, 2);
	R0(c, d, e, a, b, 3);
	R0(b, c, d, e, a, 4);
	R0(a, b, c, d, e, 5);
	R0(e, a, b, c, d, 6);
	R0(d, e, a, b, c, 7);
	R0(c, d, e, a, b, 8);
	R0(b, c, d, e, a, 9);
	R0(a, b, c, d, e, 10);
	R0(e, a, b, c, d, 11);
	R0(d, e, a, b, c, 12);
	R0(c, d, e, a, b, 13);
	R0(b, c, d, e, a, 14);
	R0(a, b, c, d, e, 15);
	R1(e, a, b, c, d, 16);
	R1(d, e, a, b, c, 17);
	R1(c, d, e, a, b, 18);
	R1(b, c, d, e, a, 19);
	R2(a, b, c, d, e, 20);
	R2(e, a, b, c, d, 21);
	R2(d, e, a, b, c, 22);
	R2(c, d, e, a, b, 23);
	R2(b, c, d, e, a, 24);
	R2(a, b, c, d, e, 25);
	R2(e, a, b, c, d, 26);
	R2(d, e, a, b, c, 27);
	R2(c, d, e, a, b, 28);
	R2(b, c, d, e, a, 29);
	R2(a, b, c, d, e, 30);
	R2(e, a, b, c, d, 31);
	R2(d, e, a, b, c, 32);
	R2(c, d, e, a, b, 33);
	R2(b, c, d, e, a, 34);
	R2(a, b, c, d, e, 35);
	R2(e, a, b, c, d, 36);
	R2(d, e, a, b, c, 37);
	R2(c, d, e, a, b, 38);
	R2(b, c, d, e, a, 39);
	R3(a, b, c, d, e, 40);
	R3(e, a, b, c, d, 41);
	R3(d, e, a, b, c, 42);
	R3(c, d, e, a, b, 43);
	R3(b, c, d, e, a, 44);
	R3(a, b, c, d, e, 45);
	R3(e, a, b, c, d, 46);
	R3(d, e, a, b, c, 47);
	R3(c, d, e, a, b, 48);
	R3(b, c, d, e, a, 49);
	R3(a, b, c, d, e, 50);
	R3(e, a, b, c, d, 51);
	R3(d, e, a, b, c, 52);
	R3(c, d, e, a, b, 53);
	R3(b, c, d, e, a, 54);
	R3(a, b, c, d, e, 55);
	R3(e, a, b, c, d, 56);
	R3(d, e, a, b, c, 57);
	R3(c, d, e, a, b, 58);
	R3(b, c, d, e, a, 59);
	R4(a, b, c, d, e, 60);
	R4(e, a, b, c, d, 61);
	R4(d, e, a, b, c, 62);
	R4(c, d, e, a, b, 63);
	R4(b, c, d, e, a, 64);
	R4(a, b, c, d, e, 65);
	R4(e, a, b, c, d, 66);
	R4(d, e, a, b, c, 67);
	R4(c, d, e, a, b, 68);
	R4(b, c, d, e, a, 69);
	R4(a, b, c, d, e, 70);
	R4(e, a, b, c, d, 71);
	R4(d, e, a, b, c, 72);
	R4(c, d, e, a, b, 73);
	R4(b, c, d, e, a, 74);
	R4(a, b, c, d, e, 75);
	R4(e, a, b, c, d, 76);
	R4(d, e, a, b, c, 77);
	R4(c, d, e, a, b, 78);
	R4(b, c, d, e, a, 79);
	/* Add the working vars back into context.state[] */
	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;
	state[4] += e;
	/* Wipe variables */
	a = b = c = d = e = 0;
#ifdef SHA1HANDSOFF
	memset(block, '\0', sizeof(block));
#endif
}

/* shaInit - Initialize new context */
void sha1Init(struct SHA1Context* context) {
	/* SHA1 initialization constants */
	context->state[0] = 0x67452301;
	context->state[1] = 0xEFCDAB89;
	context->state[2] = 0x98BADCFE;
	context->state[3] = 0x10325476;
	context->state[4] = 0xC3D2E1F0;
	context->count[0] = context->count[1] = 0;
}

/* Run your data through this. */
void sha1Update(struct SHA1Context* context, const void* data, size_t len) {
	size_t i;
	size_t j;

	j = context->count[0];
	if ((context->count[0] += len << 3) < j) {
		++context->count[1];
	}
	context->count[1] += (len >> 29);
	j = (j >> 3) & 63;
	if ((j + len) > 63) {
		memcpy(&context->buffer[j], data, (i = 64 - j));
		sha1Transform(context->state, context->buffer);
		for (; i + 63 < len; i += 64) {
			sha1Transform(context->state, &((uint8_t*) data)[i]);
		}
		j = 0;
	} else {
		i = 0;
	}
	memcpy(&context->buffer[j], &((uint8_t*) data)[i], len - i);
}

/* Add padding and return the message digest. */
void sha1Finalize(uint8_t digest[20], struct SHA1Context* context) {
	unsigned i;
	uint8_t finalcount[8];
	uint8_t c;

	for (i = 0; i < 8; ++i) {
		finalcount[i] = (uint8_t) ((context->count[(i >= 4 ? 0 : 1)] >> ((3 - (i & 3)) * 8)) & 255);      /* Endian independent */
	}
	c = 0200;
	sha1Update(context, &c, 1);
	while ((context->count[0] & 504) != 448) {
		c = 0000;
		sha1Update(context, &c, 1);
	}
	sha1Update(context, finalcount, 8); /* Should cause a SHA1Transform() */
	for (i = 0; i < 20; ++i) {
		digest[i] = (uint8_t) ((context->state[i >> 2] >> ((3 - (i & 3)) * 8)) & 255);
	}
	/* Wipe variables */
	memset(context, '\0', sizeof(*context));
	memset(&finalcount, '\0', sizeof(finalcount));
}

void sha1Buffer(const void* input, size_t len, uint8_t* result) {
	struct SHA1Context ctx;
	size_t i;

	sha1Init(&ctx);
	for (i = 0; i + 63 < len; i += 64) {
		sha1Update(&ctx, &((const uint8_t*) input)[i], 64);
	}
	for (; i < len; ++i) {
		sha1Update(&ctx, &((const uint8_t*) input)[i], 1);
	}
	sha1Finalize(result, &ctx);
}

bool sha1File(struct VFile* vf, uint8_t* result) {
	struct SHA1Context ctx;
	uint8_t buffer[2048];
	sha1Init(&ctx);

	ssize_t read;
	ssize_t position = vf->seek(vf, 0, SEEK_CUR);
	if (vf->seek(vf, 0, SEEK_SET) < 0) {
		return false;
	}
	while ((read = vf->read(vf, buffer, sizeof(buffer))) > 0) {
		sha1Update(&ctx, buffer, read);
	}
	vf->seek(vf, position, SEEK_SET);
	if (read < 0) {
		return false;
	}
	sha1Finalize(result, &ctx);
	return true;
}
