/*
 *	BIRD -- SHA-1 Hash Function (FIPS 180-1, RFC 3174)
 *
 *	(c) 2015 CZ.NIC z.s.p.o.
 *
 *	Based on the code from libucw-6.4
 *	(c) 2008--2009 Martin Mares <mj@ucw.cz>
 *
 *	Based on the code from libgcrypt-1.2.3, which is
 *	(c) 1998, 2001, 2002, 2003 Free Software Foundation, Inc.
 *
 *	Can be freely distributed and used under the terms of the GNU GPL.
 */

#include "lib/null.h"
#include "lib/sha1.h"
#include "lib/unaligned.h"

#include <string.h>

void
sha1_init(sha1_context *hd)
{
  hd->h0 = 0x67452301;
  hd->h1 = 0xefcdab89;
  hd->h2 = 0x98badcfe;
  hd->h3 = 0x10325476;
  hd->h4 = 0xc3d2e1f0;
  hd->nblocks = 0;
  hd->count = 0;
}

/*
 * Transform the message X which consists of 16 32-bit-words
 */
static void
transform(sha1_context *hd, const byte *data)
{
  u32 a,b,c,d,e,tm;
  u32 x[16];

  /* Get values from the chaining vars. */
  a = hd->h0;
  b = hd->h1;
  c = hd->h2;
  d = hd->h3;
  e = hd->h4;

#ifdef CPU_BIG_ENDIAN
  memcpy(x, data, 64);
#else
  int i;
  for (i = 0; i < 16; i++)
    x[i] = get_u32(data+4*i);
#endif


#define K1  0x5A827999L
#define K2  0x6ED9EBA1L
#define K3  0x8F1BBCDCL
#define K4  0xCA62C1D6L
#define F1(x,y,z)   ( z ^ ( x & ( y ^ z ) ) )
#define F2(x,y,z)   ( x ^ y ^ z )
#define F3(x,y,z)   ( ( x & y ) | ( z & ( x | y ) ) )
#define F4(x,y,z)   ( x ^ y ^ z )


#define M(i) ( tm =   x[i&0x0f] ^ x[(i-14)&0x0f] \
		    ^ x[(i-8)&0x0f] ^ x[(i-3)&0x0f] \
	       , (x[i&0x0f] = ROL(tm, 1)) )

#define	ROL(x, bits) (((x) << (bits)) | ((uint)(x) >> (sizeof(uint)*8 - (bits))))		/** Bitwise rotation of an unsigned int to the left **/

  #define R(a,b,c,d,e,f,k,m)  do { e += ROL( a, 5 )     \
				      + f( b, c, d )  \
				      + k	      \
				      + m;	      \
				 b = ROL( b, 30 );    \
			       } while(0)
  R( a, b, c, d, e, F1, K1, x[ 0] );
  R( e, a, b, c, d, F1, K1, x[ 1] );
  R( d, e, a, b, c, F1, K1, x[ 2] );
  R( c, d, e, a, b, F1, K1, x[ 3] );
  R( b, c, d, e, a, F1, K1, x[ 4] );
  R( a, b, c, d, e, F1, K1, x[ 5] );
  R( e, a, b, c, d, F1, K1, x[ 6] );
  R( d, e, a, b, c, F1, K1, x[ 7] );
  R( c, d, e, a, b, F1, K1, x[ 8] );
  R( b, c, d, e, a, F1, K1, x[ 9] );
  R( a, b, c, d, e, F1, K1, x[10] );
  R( e, a, b, c, d, F1, K1, x[11] );
  R( d, e, a, b, c, F1, K1, x[12] );
  R( c, d, e, a, b, F1, K1, x[13] );
  R( b, c, d, e, a, F1, K1, x[14] );
  R( a, b, c, d, e, F1, K1, x[15] );
  R( e, a, b, c, d, F1, K1, M(16) );
  R( d, e, a, b, c, F1, K1, M(17) );
  R( c, d, e, a, b, F1, K1, M(18) );
  R( b, c, d, e, a, F1, K1, M(19) );
  R( a, b, c, d, e, F2, K2, M(20) );
  R( e, a, b, c, d, F2, K2, M(21) );
  R( d, e, a, b, c, F2, K2, M(22) );
  R( c, d, e, a, b, F2, K2, M(23) );
  R( b, c, d, e, a, F2, K2, M(24) );
  R( a, b, c, d, e, F2, K2, M(25) );
  R( e, a, b, c, d, F2, K2, M(26) );
  R( d, e, a, b, c, F2, K2, M(27) );
  R( c, d, e, a, b, F2, K2, M(28) );
  R( b, c, d, e, a, F2, K2, M(29) );
  R( a, b, c, d, e, F2, K2, M(30) );
  R( e, a, b, c, d, F2, K2, M(31) );
  R( d, e, a, b, c, F2, K2, M(32) );
  R( c, d, e, a, b, F2, K2, M(33) );
  R( b, c, d, e, a, F2, K2, M(34) );
  R( a, b, c, d, e, F2, K2, M(35) );
  R( e, a, b, c, d, F2, K2, M(36) );
  R( d, e, a, b, c, F2, K2, M(37) );
  R( c, d, e, a, b, F2, K2, M(38) );
  R( b, c, d, e, a, F2, K2, M(39) );
  R( a, b, c, d, e, F3, K3, M(40) );
  R( e, a, b, c, d, F3, K3, M(41) );
  R( d, e, a, b, c, F3, K3, M(42) );
  R( c, d, e, a, b, F3, K3, M(43) );
  R( b, c, d, e, a, F3, K3, M(44) );
  R( a, b, c, d, e, F3, K3, M(45) );
  R( e, a, b, c, d, F3, K3, M(46) );
  R( d, e, a, b, c, F3, K3, M(47) );
  R( c, d, e, a, b, F3, K3, M(48) );
  R( b, c, d, e, a, F3, K3, M(49) );
  R( a, b, c, d, e, F3, K3, M(50) );
  R( e, a, b, c, d, F3, K3, M(51) );
  R( d, e, a, b, c, F3, K3, M(52) );
  R( c, d, e, a, b, F3, K3, M(53) );
  R( b, c, d, e, a, F3, K3, M(54) );
  R( a, b, c, d, e, F3, K3, M(55) );
  R( e, a, b, c, d, F3, K3, M(56) );
  R( d, e, a, b, c, F3, K3, M(57) );
  R( c, d, e, a, b, F3, K3, M(58) );
  R( b, c, d, e, a, F3, K3, M(59) );
  R( a, b, c, d, e, F4, K4, M(60) );
  R( e, a, b, c, d, F4, K4, M(61) );
  R( d, e, a, b, c, F4, K4, M(62) );
  R( c, d, e, a, b, F4, K4, M(63) );
  R( b, c, d, e, a, F4, K4, M(64) );
  R( a, b, c, d, e, F4, K4, M(65) );
  R( e, a, b, c, d, F4, K4, M(66) );
  R( d, e, a, b, c, F4, K4, M(67) );
  R( c, d, e, a, b, F4, K4, M(68) );
  R( b, c, d, e, a, F4, K4, M(69) );
  R( a, b, c, d, e, F4, K4, M(70) );
  R( e, a, b, c, d, F4, K4, M(71) );
  R( d, e, a, b, c, F4, K4, M(72) );
  R( c, d, e, a, b, F4, K4, M(73) );
  R( b, c, d, e, a, F4, K4, M(74) );
  R( a, b, c, d, e, F4, K4, M(75) );
  R( e, a, b, c, d, F4, K4, M(76) );
  R( d, e, a, b, c, F4, K4, M(77) );
  R( c, d, e, a, b, F4, K4, M(78) );
  R( b, c, d, e, a, F4, K4, M(79) );

  /* Update chaining vars. */
  hd->h0 += a;
  hd->h1 += b;
  hd->h2 += c;
  hd->h3 += d;
  hd->h4 += e;
}


/*
 * Update the message digest with the contents
 * of INBUF with length INLEN.
 */
void
sha1_update(sha1_context *hd, const byte *inbuf, uint inlen)
{
  if( hd->count == 64 )  /* flush the buffer */
  {
    transform( hd, hd->buf );
    hd->count = 0;
    hd->nblocks++;
  }
  if( !inbuf )
    return;

  if( hd->count )
  {
    for( ; inlen && hd->count < 64; inlen-- )
      hd->buf[hd->count++] = *inbuf++;
    sha1_update( hd, NULL, 0 );
    if( !inlen )
      return;
  }

  while( inlen >= 64 ) 
  {
    transform( hd, inbuf );
    hd->count = 0;
    hd->nblocks++;
    inlen -= 64;
    inbuf += 64;
  }
  for( ; inlen && hd->count < 64; inlen-- )
    hd->buf[hd->count++] = *inbuf++;
}


/*
 * The routine final terminates the computation and
 * returns the digest.
 * The handle is prepared for a new cycle, but adding bytes to the
 * handle will the destroy the returned buffer.
 * Returns: 20 bytes representing the digest.
 */

byte *
sha1_final(sha1_context *hd)
{
  u32 t, msb, lsb;
  u32 *p;

  sha1_update(hd, NULL, 0); /* flush */;

  t = hd->nblocks;
  /* multiply by 64 to make a byte count */
  lsb = t << 6;
  msb = t >> 26;
  /* add the count */
  t = lsb;
  if( (lsb += hd->count) < t )
    msb++;
  /* multiply by 8 to make a bit count */
  t = lsb;
  lsb <<= 3;
  msb <<= 3;
  msb |= t >> 29;

  if( hd->count < 56 )  /* enough room */
  {
    hd->buf[hd->count++] = 0x80; /* pad */
    while( hd->count < 56 )
      hd->buf[hd->count++] = 0;  /* pad */
  }
  else  /* need one extra block */
  {
    hd->buf[hd->count++] = 0x80; /* pad character */
    while( hd->count < 64 )
      hd->buf[hd->count++] = 0;
    sha1_update(hd, NULL, 0);  /* flush */;
    memset(hd->buf, 0, 56 ); /* fill next block with zeroes */
  }
  /* append the 64 bit count */
  hd->buf[56] = msb >> 24;
  hd->buf[57] = msb >> 16;
  hd->buf[58] = msb >>  8;
  hd->buf[59] = msb	   ;
  hd->buf[60] = lsb >> 24;
  hd->buf[61] = lsb >> 16;
  hd->buf[62] = lsb >>  8;
  hd->buf[63] = lsb	   ;
  transform(hd, hd->buf);

  p = (u32*) hd->buf;
#define X(a) do { put_u32(p, hd->h##a); p++; } while(0)
  X(0);
  X(1);
  X(2);
  X(3);
  X(4);
#undef X

  return hd->buf;
}

/*
 * Shortcut function which puts the hash value of the supplied buffer
 * into outbuf which must have a size of 20 bytes.
 */
void
sha1_hash_buffer(byte *outbuf, const byte *buffer, uint length)
{
  sha1_context hd;

  sha1_init(&hd);
  sha1_update(&hd, buffer, length);
  memcpy(outbuf, sha1_final(&hd), SHA1_SIZE);
}

#ifdef TEST

#include <stdio.h>
#include <unistd.h>
#include <ucw/string.h>

int main(void)
{
  sha1_context hd;
  byte buf[3];
  int cnt;

  sha1_init(&hd);
  while ((cnt = read(0, buf, sizeof(buf))) > 0)
    sha1_update(&hd, buf, cnt);

  char text[SHA1_HEX_SIZE];
  mem_to_hex(text, sha1_final(&hd), SHA1_SIZE, 0);
  puts(text);

  return 0;
}

#endif