/*
 * sha256.c - Implementation of the Secure Hash Algorithm-256 (SHA-256).
 *
 * Implemented from the description on the NIST Web site:
 *		http://csrc.nist.gov/cryptval/shs.html
 *
 *
 * Copyright (C) 2012  Rafal Kupiec (customized for sessmgr)
 * Copyright (C) 2009  Eric Bishop (adapted as standalone utility)
 * Copyright (C) 2002  Southern Storm Software, Pty Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>

#include "sha256.h"

static void ProcessBlock(SHA256Context *sha, const unsigned char *block) {
	u_int32_t W[64];
	u_int32_t a, b, c, d, e, f, g, h;
	u_int32_t temp, temp2;
	int t;

	for(t = 0; t < 16; ++t) {
		W[t] = (((u_int32_t) (block[t * 4 + 0])) << 24) | (((u_int32_t) (block[t * 4 + 1])) << 16) | (((u_int32_t) (block[t * 4 + 2])) <<  8) | ((u_int32_t) (block[t * 4 + 3]));
	}
	for(t = 16; t < 64; ++t) {
		W[t] = TRUNCLONG(RHO1(W[t - 2]) + W[t - 7] + RHO0(W[t - 15]) + W[t - 16]);
	}
	a = sha->A;
	b = sha->B;
	c = sha->C;
	d = sha->D;
	e = sha->E;
	f = sha->F;
	g = sha->G;
	h = sha->H;
	for(t = 0; t < 64; ++t) {
		temp = TRUNCLONG(h + SUM1(e) + CH(e, f, g) + K[t] + W[t]);
		temp2 = TRUNCLONG(SUM0(a) + MAJ(a, b, c));
		h = g;
		g = f;
		f = e;
		e = TRUNCLONG(d + temp);
		d = c;
		c = b;
		b = a;
		a = TRUNCLONG(temp + temp2);
	}
	sha->A = TRUNCLONG(sha->A + a);
	sha->B = TRUNCLONG(sha->B + b);
	sha->C = TRUNCLONG(sha->C + c);
	sha->D = TRUNCLONG(sha->D + d);
	sha->E = TRUNCLONG(sha->E + e);
	sha->F = TRUNCLONG(sha->F + f);
	sha->G = TRUNCLONG(sha->G + g);
	sha->H = TRUNCLONG(sha->H + h);
	DoMemZero(W, sizeof(u_int32_t) * 64);
	a = b = c = d = e = f = g = h = temp = temp2 = 0;
}

void SHA256Data(SHA256Context *sha, const void *buffer, unsigned long len) {
	unsigned long templen;

	sha->totalLen += (u_int64_t)len;
	while(len > 0) {
		if(!(sha->inputLen) && len >= 64) {
			ProcessBlock(sha, (const unsigned char *) buffer);
			buffer = (const void *) (((const unsigned char *) buffer) + 64);
			len -= 64;
		} else {
			templen = len;
			if(templen > (64 - sha->inputLen)) {
				templen = 64 - sha->inputLen;
			}
			memcpy(sha->input + sha->inputLen, buffer, templen);
			if((sha->inputLen += templen) >= 64) {
				ProcessBlock(sha, sha->input);
				sha->inputLen = 0;
			}
			buffer = (const void *) (((const unsigned char *) buffer) + templen);
			len -= templen;
		}
	}
}

void SHA256Finalize(SHA256Context *sha, unsigned char hash[SHA256_HASH_SIZE]) {
	u_int64_t totalBits;

	if(hash) {
		if(sha->inputLen >= 56) {
			sha->input[(sha->inputLen)++] = (unsigned char) 0x80;
			while(sha->inputLen < 64) {
				sha->input[(sha->inputLen)++] = (unsigned char) 0x00;
			}
			ProcessBlock(sha, sha->input);
			sha->inputLen = 0;
		} else {
			sha->input[(sha->inputLen)++] = (unsigned char) 0x80;
		}
		while(sha->inputLen < 56) {
			sha->input[(sha->inputLen)++] = (unsigned char) 0x00;
		}
		totalBits = (sha->totalLen << 3);
		WriteLong(sha->input + 56, (u_int32_t) (totalBits >> 32));
		WriteLong(sha->input + 60, (u_int32_t) totalBits);
		ProcessBlock(sha, sha->input);
		WriteLong(hash, sha->A);
		WriteLong(hash + 4, sha->B);
		WriteLong(hash + 8, sha->C);
		WriteLong(hash + 12, sha->D);
		WriteLong(hash + 16, sha->E);
		WriteLong(hash + 20, sha->F);
		WriteLong(hash + 24, sha->G);
		WriteLong(hash + 28, sha->H);
	}
	DoMemZero(sha, sizeof(SHA256Context));
}

void SHA256Init(SHA256Context *sha) {
	sha->inputLen = 0;
	sha->A = 0x6a09e667;
	sha->B = 0xbb67ae85;
	sha->C = 0x3c6ef372;
	sha->D = 0xa54ff53a;
	sha->E = 0x510e527f;
	sha->F = 0x9b05688c;
	sha->G = 0x1f83d9ab;
	sha->H = 0x5be0cd19;
	sha->totalLen = 0;
}

static void WriteLong(unsigned char *buf, u_int32_t value) {
	buf[0] = (unsigned char)(value >> 24);
	buf[1] = (unsigned char)(value >> 16);
	buf[2] = (unsigned char)(value >> 8);
	buf[3] = (unsigned char)value;
}

unsigned char* get_sha256_hash(const char* unhashed) {
	SHA256Context sha;
	unsigned char* hash = (unsigned char*) malloc(32);

	SHA256Init(&sha);
	SHA256Data(&sha, unhashed, strlen(unhashed));
	SHA256Finalize(&sha, hash);
	return hash;
}

char* get_sha256_hash_hex_str(const char* unhashed) {
	unsigned char* hashed = get_sha256_hash(unhashed);
	char* hashed_hex = (char*) malloc(65);
	char next_hex[3];
	int index =0;

	hashed_hex[0] = '\0';
	for(index=0; index < 32; index++) {
		sprintf(next_hex, "%02X", hashed[index]);
		strcat(hashed_hex, next_hex);
	}
	free(hashed);
	return hashed_hex;
}