/* $OpenBSD: xmss_hash.c,v 1.3 2022/04/20 16:00:25 millert Exp $ */

/*

hash.c version 20160722

Andreas Hülsing

Joost Rijneveld

Public domain.

*/

#include "includes.h"

#ifdef WITH_XMSS

#include "xmss_hash_address.h"

#include "xmss_commons.h"

#include "xmss_hash.h"

#include <stddef.h>

#ifdef HAVE_STDINT_H

# include <stdint.h>

#endif

#include <stdio.h>

#include <string.h>

int core_hash_SHA2(unsigned char *, const unsigned int, const unsigned char *,

    unsigned int, const unsigned char *, unsigned long long, unsigned int);

unsigned char* addr_to_byte(unsigned char *bytes, const uint32_t addr[8]){

#if IS_LITTLE_ENDIAN==1 

  int i = 0;

  for(i=0;i<8;i++)

    to_byte(bytes+i*4, addr[i],4);

  return bytes;  

#else

  memcpy(bytes, addr, 32);

  return bytes; 

#endif   

}

int core_hash_SHA2(unsigned char *out, const unsigned int type, const unsigned char *key, unsigned int keylen, const unsigned char *in, unsigned long long inlen, unsigned int n){  

  unsigned long long i = 0;

  unsigned char buf[inlen + n + keylen];

  // Input is (toByte(X, 32) || KEY || M) 

  // set toByte

  to_byte(buf, type, n);

  for (i=0; i < keylen; i++) {

    buf[i+n] = key[i];

  }

  for (i=0; i < inlen; i++) {

    buf[keylen + n + i] = in[i];

  }

  if (n == 32) {

    SHA256(buf, inlen + keylen + n, out);

    return 0;

  }

  else {

    if (n == 64) {

      SHA512(buf, inlen + keylen + n, out);

      return 0;

    }

  }

  return 1;

}

/**

 * Implements PRF

 */

int prf(unsigned char *out, const unsigned char *in, const unsigned char *key, unsigned int keylen)

{ 

  return core_hash_SHA2(out, 3, key, keylen, in, 32, keylen);

}

/*

 * Implemts H_msg

 */

int h_msg(unsigned char *out, const unsigned char *in, unsigned long long inlen, const unsigned char *key, const unsigned int keylen, const unsigned int n)

{

  if (keylen != 3*n){

    // H_msg takes 3n-bit keys, but n does not match the keylength of keylen

    return -1;

  }  

  return core_hash_SHA2(out, 2, key, keylen, in, inlen, n);

}

/**

 * We assume the left half is in in[0]...in[n-1]

 */

int hash_h(unsigned char *out, const unsigned char *in, const unsigned char *pub_seed, uint32_t addr[8], const unsigned int n)

{

  unsigned char buf[2*n];

  unsigned char key[n];

  unsigned char bitmask[2*n];

  unsigned char byte_addr[32];

  unsigned int i;

  setKeyAndMask(addr, 0);

  addr_to_byte(byte_addr, addr);

  prf(key, byte_addr, pub_seed, n);

  // Use MSB order

  setKeyAndMask(addr, 1);

  addr_to_byte(byte_addr, addr);

  prf(bitmask, byte_addr, pub_seed, n);

  setKeyAndMask(addr, 2);

  addr_to_byte(byte_addr, addr);

  prf(bitmask+n, byte_addr, pub_seed, n);

  for (i = 0; i < 2*n; i++) {

    buf[i] = in[i] ^ bitmask[i];

  }

  return core_hash_SHA2(out, 1, key, n, buf, 2*n, n);

}

int hash_f(unsigned char *out, const unsigned char *in, const unsigned char *pub_seed, uint32_t addr[8], const unsigned int n)

{

  unsigned char buf[n];

  unsigned char key[n];

  unsigned char bitmask[n];

  unsigned char byte_addr[32];

  unsigned int i;

  setKeyAndMask(addr, 0);  

  addr_to_byte(byte_addr, addr);  

  prf(key, byte_addr, pub_seed, n);

  setKeyAndMask(addr, 1);

  addr_to_byte(byte_addr, addr);

  prf(bitmask, byte_addr, pub_seed, n);

  for (i = 0; i < n; i++) {

    buf[i] = in[i] ^ bitmask[i];

  }

  return core_hash_SHA2(out, 0, key, n, buf, n, n);

}

#endif /* WITH_XMSS */