/*
 *    
 *      Author: George Mossessian
 *      https://rosettacode.org/wiki/MD4
 *
 *      The MD4 hash algorithm, as described in https://tools.ietf.org/html/rfc1320
 */
 
 
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#include "md4.h"

typedef struct string{
        char *c;
        int len;
        char sign;
}string;
 
static uint32_t *MD4Digest(uint32_t *w, int len);
static void setMD4Registers(uint32_t AA, uint32_t BB, uint32_t CC, uint32_t DD);
static uint32_t changeEndianness(uint32_t x);
static void resetMD4Registers(void);
static string stringCat(string first, string second);
static string uint32ToString(uint32_t l);
static uint32_t stringToUint32(string s);
 
static const char *BASE16 = "0123456789abcdef=";
 
#define F(X,Y,Z) (((X)&(Y))|((~(X))&(Z)))
#define G(X,Y,Z) (((X)&(Y))|((X)&(Z))|((Y)&(Z)))
#define H(X,Y,Z) ((X)^(Y)^(Z))
 
#define LEFTROTATE(A,N) ((A)<<(N))|((A)>>(32-(N)))
 
#define MD4ROUND1(a,b,c,d,x,s) a += F(b,c,d) + x; a = LEFTROTATE(a, s);
#define MD4ROUND2(a,b,c,d,x,s) a += G(b,c,d) + x + (uint32_t)0x5A827999; a = LEFTROTATE(a, s);
#define MD4ROUND3(a,b,c,d,x,s) a += H(b,c,d) + x + (uint32_t)0x6ED9EBA1; a = LEFTROTATE(a, s);
 
static uint32_t A = 0x67452301;
static uint32_t B = 0xefcdab89;
static uint32_t C = 0x98badcfe;
static uint32_t D = 0x10325476;
 
string newString(char * c, int t) {
	string r;
	int i;
	if(c!=NULL){
		r.len = (t<=0)?strlen(c):t;
		r.c=(char *)malloc(sizeof(char)*(r.len+1));
		for(i=0; i<r.len; i++) r.c[i]=c[i];
		r.c[r.len]='\0';
		return r;
	}
	r.len=t;
	r.c=(char *)malloc(sizeof(char)*(r.len+1));
	memset(r.c,(char)0,sizeof(char)*(t+1));
	r.sign = 1;
	return r;
}
 
string stringCat(string first, string second){
	string str=newString(NULL, first.len+second.len);
	int i;
 
	for(i=0; i<first.len; i++){
		str.c[i]=first.c[i];
	}
	for(i=first.len; i<str.len; i++){
		str.c[i]=second.c[i-first.len];
	}
	return str;
}
 
string base16Encode(string in){
	string out=newString(NULL, in.len*2);
	int i,j;
 
	j=0;
	for(i=0; i<in.len; i++){
		out.c[j++]=BASE16[((in.c[i] & 0xF0)>>4)];
		out.c[j++]=BASE16[(in.c[i] & 0x0F)];
	}
	out.c[j]='\0';
	return out;
}
 
 
string uint32ToString(uint32_t l){
	string s = newString(NULL,4);
	int i;
	for(i=0; i<4; i++){
		s.c[i] = (l >> (8*(3-i))) & 0xFF;
	}
	return s;
}
 
uint32_t stringToUint32(string s){
	uint32_t l;
	int i;
	l=0;
	for(i=0; i<4; i++){
		l = l|(((uint32_t)((unsigned char)s.c[i]))<<(8*(3-i)));
	}
	return l;
}
 
char *MD4(char *str, int len){
	string m=newString(str, len);
	string digest;
	uint32_t *w;
	uint32_t *hash;
	uint64_t mlen=m.len;
	unsigned char oneBit = 0x80;
	int i, wlen;
 
	string s = newString((char *)&oneBit,1);
	string ss = stringCat(m, s);
	free(m.c);
	m=ss;
	free(s.c);
 
	//append 0 ≤ k < 512 bits '0', such that the resulting message length in bits
	//	is congruent to −64 ≡ 448 (mod 512)4
	i=((56-m.len)%64);
	if(i<0) i+=64;
	s = newString(NULL, i);
	ss = stringCat(m,s);
	free(m.c);
	m=ss;
	free(s.c);

	w = malloc(sizeof(uint32_t)*(m.len/4+2));
 
	//append length, in bits (hence <<3), least significant word first
	for(i=0; i<m.len/4; i++){
		s = newString(&(m.c[4*i]), 4);
		w[i]=stringToUint32(s);
		free(s.c);
	}
	w[i++] = (mlen<<3) & 0xFFFFFFFF;
	w[i++] = (mlen>>29) & 0xFFFFFFFF;
 
	wlen=i;

	free(m.c);
 
 
	//change endianness, but not for the appended message length, for some reason?
	for(i=0; i<wlen-2; i++){
		w[i]=changeEndianness(w[i]);
	}
 
	hash = MD4Digest(w,wlen);
	free(w);
 
	digest=newString(NULL,0);
	for(i=0; i<4; i++){
		hash[i]=changeEndianness(hash[i]);
		s = uint32ToString(hash[i]);
		string ss = stringCat(digest,s);
		free(s.c);
		free(digest.c);
		digest=ss;
	}

	free(hash);
 
	char* g = base16Encode(digest).c;
	free(digest.c);
	return g;
}
 
uint32_t *MD4Digest(uint32_t *w, int len){
	//assumes message.len is a multiple of 64 bytes.
	int i,j;
	uint32_t X[16];
	uint32_t *digest = malloc(sizeof(uint32_t)*4);
	uint32_t AA, BB, CC, DD;
 
	for(i=0; i<len/16; i++){
		for(j=0; j<16; j++){
			X[j]=w[i*16+j];
		}
 
		AA=A;
		BB=B;
		CC=C;
		DD=D;
 
		MD4ROUND1(A,B,C,D,X[0],3);
		MD4ROUND1(D,A,B,C,X[1],7);
		MD4ROUND1(C,D,A,B,X[2],11);
		MD4ROUND1(B,C,D,A,X[3],19);
		MD4ROUND1(A,B,C,D,X[4],3);
		MD4ROUND1(D,A,B,C,X[5],7);
		MD4ROUND1(C,D,A,B,X[6],11);
		MD4ROUND1(B,C,D,A,X[7],19);
		MD4ROUND1(A,B,C,D,X[8],3);
		MD4ROUND1(D,A,B,C,X[9],7);
		MD4ROUND1(C,D,A,B,X[10],11);
		MD4ROUND1(B,C,D,A,X[11],19);
		MD4ROUND1(A,B,C,D,X[12],3);
		MD4ROUND1(D,A,B,C,X[13],7);
		MD4ROUND1(C,D,A,B,X[14],11);
		MD4ROUND1(B,C,D,A,X[15],19);
 
		MD4ROUND2(A,B,C,D,X[0],3);
		MD4ROUND2(D,A,B,C,X[4],5);
		MD4ROUND2(C,D,A,B,X[8],9);
		MD4ROUND2(B,C,D,A,X[12],13);
		MD4ROUND2(A,B,C,D,X[1],3);
		MD4ROUND2(D,A,B,C,X[5],5);
		MD4ROUND2(C,D,A,B,X[9],9);
		MD4ROUND2(B,C,D,A,X[13],13);
		MD4ROUND2(A,B,C,D,X[2],3);
		MD4ROUND2(D,A,B,C,X[6],5);
		MD4ROUND2(C,D,A,B,X[10],9);
		MD4ROUND2(B,C,D,A,X[14],13);
		MD4ROUND2(A,B,C,D,X[3],3);
		MD4ROUND2(D,A,B,C,X[7],5);
		MD4ROUND2(C,D,A,B,X[11],9);
		MD4ROUND2(B,C,D,A,X[15],13);
 
		MD4ROUND3(A,B,C,D,X[0],3);
		MD4ROUND3(D,A,B,C,X[8],9);
		MD4ROUND3(C,D,A,B,X[4],11);
		MD4ROUND3(B,C,D,A,X[12],15);
		MD4ROUND3(A,B,C,D,X[2],3);
		MD4ROUND3(D,A,B,C,X[10],9);
		MD4ROUND3(C,D,A,B,X[6],11);
		MD4ROUND3(B,C,D,A,X[14],15);
		MD4ROUND3(A,B,C,D,X[1],3);
		MD4ROUND3(D,A,B,C,X[9],9);
		MD4ROUND3(C,D,A,B,X[5],11);
		MD4ROUND3(B,C,D,A,X[13],15);
		MD4ROUND3(A,B,C,D,X[3],3);
		MD4ROUND3(D,A,B,C,X[11],9);
		MD4ROUND3(C,D,A,B,X[7],11);
		MD4ROUND3(B,C,D,A,X[15],15);
 
		A+=AA;
		B+=BB;
		C+=CC;
		D+=DD;
	}
 
	digest[0]=A;
	digest[1]=B;
	digest[2]=C;
	digest[3]=D;
	resetMD4Registers();
	return digest;
}
 
uint32_t changeEndianness(uint32_t x){
	return ((x & 0xFF) << 24) | ((x & 0xFF00) << 8) | ((x & 0xFF0000) >> 8) | ((x & 0xFF000000) >> 24);
}
 
void setMD4Registers(uint32_t AA, uint32_t BB, uint32_t CC, uint32_t DD){
	A=AA;
	B=BB;
	C=CC;
	D=DD;
}
 
void resetMD4Registers(void){
	setMD4Registers(0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476);
}