/* Implementacija SHA-1 algoritma za izracunavanje sazetka 
 * 
 * (c) Dalibor Dukic duke@x.pbf.hr 
 * Sat Oct 23 13:36:41 CEST 2004
 * 
 * algoritam slijedi specifikaciju FIPS 180-1 standard 
 * potpisan od strane NIST-a 
 * 
 */
 
/* ./sha <ime_datoteke> */

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include "Header/sha1.h"

/* sha-1 context */
//u_int32_t M[16];
const u_int32_t K[]={   /*  Konstante definirane u SHA-1 */
	0x5A827999,	0x5A827999, 0x5A827999,	0x5A827999,	
	0x5A827999,	0x5A827999, 0x5A827999,	0x5A827999, 
	0x5A827999,	0x5A827999, 0x5A827999, 0x5A827999,
	0x5A827999, 0x5A827999, 0x5A827999, 0x5A827999,
	0x5A827999, 0x5A827999, 0x5A827999, 0x5A827999,
	0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1,
	0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1,
	0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1,
	0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1,
	0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1, 0x6ED9EBA1,
	0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC,
	0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC,
	0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC,
	0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC,
	0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC, 0x8F1BBCDC,
  	0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6,
  	0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6,
  	0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6,
  	0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6,
  	0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6, 0xCA62C1D6,
};
const u_int32_t H[]={
  	0x67452301,
  	0xEFCDAB89,
  	0x98BADCFE,
  	0x10325476,
  	0xC3D2E1F0
};


/* inicijalizacija konteksta */
void sha1_init(SHA_CTX* sha1_ctx){
	
																 
	sha1_ctx->digest[0]=H[0];
	sha1_ctx->digest[1]=H[1];
	sha1_ctx->digest[2]=H[2];
 	sha1_ctx->digest[3]=H[3];
	sha1_ctx->digest[4]=H[4];
	
	sha1_ctx->count[0]=0;
	sha1_ctx->count[1]=0;

	sha1_ctx->index=0;
	
	sha1_ctx->processed=0;
}


void process_block(SHA_CTX* sha1_ctx, u_int8_t* buffer, unsigned int len ){
	
	int i;

	
	memset(&sha1_ctx->M, 0, 64);
#ifdef DEBUG
	fprintf(stdout, "buffer -> %s\n",buffer);
	fprintf(stdout, "len-> %d\n",len);
#endif
	/* kad dobijemo manji buffer od 64 (64*8)*/
	

	u_int32_t byte;
		
	for(i=0; i<len; i++){
			if(i==638){
				fprintf(stdout, "evi\n");
			}
		byte=buffer[i];

	
		
		byte=byte<<(8*(3-i%4));	
		sha1_ctx->M[sha1_ctx->index]|=byte;
		
		if(sha1_ctx->processed==1) sha1_ctx->processed=0;
			
		if((i+1)%4==0)
			sha1_ctx->index+=1;		
		
	
		/* povecaj counter */	
		sha1_ctx->count[0]+=8;
		if(sha1_ctx->count[0]==0){
			sha1_ctx->count[1]++;
		//	if(sha1_ctx->count[1]==0) 
		//		merror("Poruka je predugacka",__LINE__);
			}
		
		
		if(((i+1)*8)%512==0){
			sha1_process_block(sha1_ctx);
			sha1_ctx->index=0;
			sha1_ctx->processed=1;
			memset(&sha1_ctx->M, 0, 64);
			
		}
		
	

	}
	

	if(len <= BUFFER_LENGTH){

		if(sha1_ctx->processed==1) {
			sha1_ctx->M[sha1_ctx->index]|=0x80000000;
			sha1_ctx->M[14]=sha1_ctx->count[1];
			sha1_ctx->M[15]=sha1_ctx->count[0];
			sha1_process_block(sha1_ctx);
			
			return;
		}
		if((len*8)%512 >447){
			if(len%4==1) 	  sha1_ctx->M[sha1_ctx->index-1]|=0x00800000;
			else if(len%4==2) sha1_ctx->M[sha1_ctx->index-1]|=0x00008000;
			else if(len%4==3) sha1_ctx->M[sha1_ctx->index-1]|=0x00000080;
			else if(len%4==0) sha1_ctx->M[sha1_ctx->index]|=0x80000000;
			sha1_process_block(sha1_ctx);
			sha1_ctx->index=0;
			
			memset(&sha1_ctx->M, 0, 64);
			
			sha1_ctx->M[14]=sha1_ctx->count[1];
			sha1_ctx->M[15]=sha1_ctx->count[0];
			
			sha1_process_block(sha1_ctx);
			sha1_ctx->index=0;
			
			return;			
		}
		if(len%4==1) 	  sha1_ctx->M[sha1_ctx->index]|=0x00800000;
		else if(len%4==2) sha1_ctx->M[sha1_ctx->index]|=0x00008000;
		else if(len%4==3) sha1_ctx->M[sha1_ctx->index]|=0x00000080;
		else if(len%4==0) sha1_ctx->M[sha1_ctx->index+1]|=0x80000000;

		sha1_ctx->M[14]=sha1_ctx->count[1];
		sha1_ctx->M[15]=sha1_ctx->count[0];
	
		sha1_process_block(sha1_ctx);
		sha1_ctx->index=0;
	}
	
#ifdef DEBUG
	fprintf(stdout, "i=%d, coun %d-", i,sha1_ctx->count[1]);
	fprintf(stdout, "%d\n", sha1_ctx->count[0]);
#endif
} 




/*
f(t;B,C,D) = (B AND C) OR ((NOT B) AND D) ( 0 <= t <= 19)  (u C-u: f=(B&C)|((~B)&D) )
f(t;B,C,D) = B XOR C XOR D (20 <= t <= 39)
f(t;B,C,D) = (B AND C) OR (B AND D) OR (C AND D) (40 <= t <= 59)
f(t;B,C,D) = B XOR C XOR D (60 <= t <= 79).
*/
u_int32_t f(int t, u_int32_t B, u_int32_t C, u_int32_t D){
	
	u_int32_t buffer;
	
	if(0 <= t && t <= 19) 
		buffer=((B & C) | ((~B) & D));
	if(20 <= t && t <=39) 
		buffer=(B ^ C ^ D);
	if(40 <= t && t <= 59) 
		buffer=((B & C)|(B & D)|(C & D));
	if(60 <= t && t <= 79) 
		buffer=(B ^ C ^ D);
	
	return buffer;  
}

void sha1_process_block(SHA_CTX* sha1_ctx){
				
	u_int32_t W[80];
	u_int32_t temp;
	u_int32_t A,B,C,D,E;
	int t,j;
	
	
	for(j=0; j<=15; j++){
		W[j]=sha1_ctx->M[j];
		//W[j]=M[j];
	}
	// W(t)= ROTL_1( W(t-3) XOR W(t-8) XOR W(t-14) XOR W(t-16) )  //ROTL_1 - rotacija 1 mjesto u lijevo
	for(t=16; t<=79; t++){
		W[t]=ROTL(1, W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
	}
	
	A=sha1_ctx->digest[0];
	B=sha1_ctx->digest[1];
	C=sha1_ctx->digest[2];
	D=sha1_ctx->digest[3];
	E=sha1_ctx->digest[4];
	
//	  TEMP=ROTL_5(A) + f(t;B,C,D) + E + W(t) + K(t) 
	for(t=0; t<=79; t++){
		temp=ROTL(5, A) + f(t, B, C, D) + E + W[t] + K[t];
	
		E=D;
    	D=C;
    	C=ROTL(30, B);
    	B=A;
    	A=temp;
#ifdef DEBUG
    	fprintf(stdout,"t=%02d %08x %08x %08x %08x %08x\n", t, A, B, C, D, E );	
#endif
	}
	
	sha1_ctx->digest[0]+=A;
	sha1_ctx->digest[1]+=B;
	sha1_ctx->digest[2]+=C;
	sha1_ctx->digest[3]+=D;
	sha1_ctx->digest[4]+=E;
	
}