/* sha1.c - SHA1 hash function
 *	Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
 *
 * Please see below for more legal information!
 *
 * This file is part of GnuPG.
 *
 * GnuPG 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.
 *
 * GnuPG 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 * USA.
 */


/*  Test vectors:
 *
 *  "abc"
 *  A999 3E36 4706 816A BA3E  2571 7850 C26C 9CD0 D89D
 *
 *  "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq"
 *  8498 3E44 1C3B D26E BAAE  4AA1 F951 29E5 E546 70F1
 */


#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "util.h"
#include "memory.h"
#include "algorithms.h"
#include "bithelp.h"


typedef struct {
    u32  h0,h1,h2,h3,h4;
    u32  nblocks;
    byte buf[64];
    int  count;
} SHA1_CONTEXT;

static void
burn_stack (int bytes)
{
    char buf[128];
    
    wipememory(buf,sizeof buf);
    bytes -= sizeof buf;
    if (bytes > 0)
        burn_stack (bytes);
}


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, 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;

#if BIG_ENDIAN_HOST
    memcpy( x, data, 64 );
#else
    { int i;
      byte *p2;
      for(i=0, p2=(byte*)x; i < 16; i++, p2 += 4 ) {
	p2[3] = *data++;
	p2[2] = *data++;
	p2[1] = *data++;
	p2[0] = *data++;
      }
    }
#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 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 chainig 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.
 */
static void
sha1_write( SHA1_CONTEXT *hd, byte *inbuf, size_t inlen)
{
    if( hd->count == 64 ) { /* flush the buffer */
	transform( hd, hd->buf );
        burn_stack (88+4*sizeof(void*));
	hd->count = 0;
	hd->nblocks++;
    }
    if( !inbuf )
	return;
    if( hd->count ) {
	for( ; inlen && hd->count < 64; inlen-- )
	    hd->buf[hd->count++] = *inbuf++;
	sha1_write( hd, NULL, 0 );
	if( !inlen )
	    return;
    }

    while( inlen >= 64 ) {
	transform( hd, inbuf );
	hd->count = 0;
	hd->nblocks++;
	inlen -= 64;
	inbuf += 64;
    }
    burn_stack (88+4*sizeof(void*));
    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.
 */

static void
sha1_final(SHA1_CONTEXT *hd)
{
    u32 t, msb, lsb;
    byte *p;

    sha1_write(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_write(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 );
    burn_stack (88+4*sizeof(void*));

    p = hd->buf;
#if BIG_ENDIAN_HOST
#define X(a) do { *(u32*)p = hd->h##a ; p += 4; } while(0)
#else /* little endian */
#define X(a) do { *p++ = hd->h##a >> 24; *p++ = hd->h##a >> 16;	 \
		      *p++ = hd->h##a >> 8; *p++ = hd->h##a; } while(0)
#endif
    X(0);
    X(1);
    X(2);
    X(3);
    X(4);
#undef X
}

static byte *
sha1_read( SHA1_CONTEXT *hd )
{
    return hd->buf;
}

/****************
 * Return some information about the algorithm.  We need algo here to
 * distinguish different flavors of the algorithm.
 * Returns: A pointer to string describing the algorithm or NULL if
 *	    the ALGO is invalid.
 */
const char *
sha1_get_info( int algo, size_t *contextsize,
	       byte **r_asnoid, int *r_asnlen, int *r_mdlen,
	       void (**r_init)( void *c ),
	       void (**r_write)( void *c, byte *buf, size_t nbytes ),
	       void (**r_final)( void *c ),
	       byte *(**r_read)( void *c )
	     )
{
    static byte asn[15] = /* Object ID is 1.3.14.3.2.26 */
		    { 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03,
		      0x02, 0x1a, 0x05, 0x00, 0x04, 0x14 };
    if( algo != 2 )
	return NULL;

    *contextsize = sizeof(SHA1_CONTEXT);
    *r_asnoid = asn;
    *r_asnlen = DIM(asn);
    *r_mdlen = 20;
    *(void  (**)(SHA1_CONTEXT *))r_init 		= sha1_init;
    *(void  (**)(SHA1_CONTEXT *, byte*, size_t))r_write = sha1_write;
    *(void  (**)(SHA1_CONTEXT *))r_final		= sha1_final;
    *(byte *(**)(SHA1_CONTEXT *))r_read 		= sha1_read;

    return "SHA1";
}