/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * GXSNMP -- An snmp mangament application
 *
 * SHA: NIST's Secure Hash Algorithm
 *
 * Based on SHA code originally posted to sci.crypt by Peter Gutmann
 * in message <30ajo5$oe8@ccu2.auckland.ac.nz>.
 * Modified to test for endianness on creation of SHA objects by AMK.
 * Also, the original specification of SHA was found to have a weakness
 * by NSA/NIST.  This code implements the fixed version of SHA.
 *
 * Here's the first paragraph of Peter Gutmann's posting:
 *    
 * The following is my SHA (FIPS 180) code updated to allow use of the "fixed"
 * SHA, thanks to Jim Gillogly and an anonymous contributor for the information
 * on what's changed in the new version.  The fix is a simple change which
 * involves adding a single rotate in the initial expansion function.  It is
 * unknown whether this is an optimal solution to the problem which was
 * discovered in the SHA or whether it's simply a bandaid which fixes the
 * problem with a minimum of effort (for example the reengineering of a great
 * many Capstone chips).
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <glib.h>
#include <gobject/gobject.h>
#include "gxsnmp_hash.h"
#include "gxsnmp_digest.h"
#include "gxsnmp_sha.h"

/* The SHA f()-functions.  The f1 and f3 functions can be optimized to
   save one boolean operation each - thanks to Rich Schroeppel,
   rcs@cs.arizona.edu for discovering this */

/*#define f1(x,y,z) ( ( x & y ) | ( ~x & z ) )          // Rounds  0-19 */
#define f1(x,y,z)   ( z ^ ( x & ( y ^ z ) ) )           /* Rounds  0-19 */
#define f2(x,y,z)   ( x ^ y ^ z )                       /* Rounds 20-39 */
/*#define f3(x,y,z) ( ( x & y ) | ( x & z ) | ( y & z ) )   // Rounds 40-59 */
#define f3(x,y,z)   ( ( x & y ) | ( z & ( x | y ) ) )   /* Rounds 40-59 */
#define f4(x,y,z)   ( x ^ y ^ z )                       /* Rounds 60-79 */

/* The SHA Mysterious Constants */

#define K1  0x5A827999L                                 /* Rounds  0-19 */
#define K2  0x6ED9EBA1L                                 /* Rounds 20-39 */
#define K3  0x8F1BBCDCL                                 /* Rounds 40-59 */
#define K4  0xCA62C1D6L                                 /* Rounds 60-79 */

/* SHA initial values */

#define h0init  0x67452301L
#define h1init  0xEFCDAB89L
#define h2init  0x98BADCFEL
#define h3init  0x10325476L
#define h4init  0xC3D2E1F0L

/* Note that it may be necessary to add parentheses to these macros if they
   are to be called with expressions as arguments */
/* 32-bit rotate left - kludged with shifts */

#define ROTL(n,X)  ( ( ( X ) << n ) | ( ( X ) >> ( 32 - n ) ) )

/* The initial expanding function.  The hash function is defined over an
   80-word expanded input array W, where the first 16 are copies of the input
   data, and the remaining 64 are defined by

        W[ i ] = W[ i - 16 ] ^ W[ i - 14 ] ^ W[ i - 8 ] ^ W[ i - 3 ]

   This implementation generates these values on the fly in a circular
   buffer - thanks to Colin Plumb, colin@nyx10.cs.du.edu for this
   optimization.

   The updated SHA changes the expanding function by adding a rotate of 1
   bit.  Thanks to Jim Gillogly, jim@rand.org, and an anonymous contributor
   for this information */

#define expand(W,i) ( W[ i & 15 ] = ROTL( 1, ( W[ i & 15 ] ^ W[ (i - 14) & 15 ] ^ \
                                                 W[ (i - 8) & 15 ] ^ W[ (i - 3) & 15 ] ) ) )


/* The prototype SHA sub-round.  The fundamental sub-round is:

        a' = e + ROTL( 5, a ) + f( b, c, d ) + k + data;
        b' = a;
        c' = ROTL( 30, b );
        d' = c;
        e' = d;

   but this is implemented by unrolling the loop 5 times and renaming the
   variables ( e, a, b, c, d ) = ( a', b', c', d', e' ) each iteration.
   This code is then replicated 20 times for each of the 4 functions, using
   the next 20 values from the W[] array each time */

#define subRound(a, b, c, d, e, f, k, data) \
    ( e += ROTL( 5, a ) + f( b, c, d ) + k + data, b = ROTL( 30, b ) )

static void SHAInit(guint32 digest[5]);
static void SHATransform(guint32 digest[5], guint32 data[16]);

static void gxsnmp_sha_init        (GxsnmpSha       *sha);
static void gxsnmp_sha_class_init  (GxsnmpShaClass  *klass);
static void gxsnmp_sha_finalize    (GObject         *object);

static void gxsnmp_sha_transform   (GxsnmpDigest    *digest);
static void gxsnmp_sha_reset       (GxsnmpHash      *hash);

static gpointer parent_class = NULL;

GType
gxsnmp_sha_get_type (void)
{
  static GType object_type = 0;

  if (!object_type)
    {
      static const GTypeInfo object_info =
        {
          sizeof (GxsnmpShaClass),
          (GBaseInitFunc) NULL,
          (GBaseFinalizeFunc) NULL,
          (GClassInitFunc) gxsnmp_sha_class_init,
          NULL,           /* class_finalize */
          NULL,           /* class_data */
          sizeof (GxsnmpSha),
          0,              /* n_preallocs */
          (GInstanceInitFunc) gxsnmp_sha_init,
        };

        object_type = g_type_register_static (gxsnmp_digest_get_type(),
                                              "GxsnmpSha",
                                              &object_info, 0);
    }
  return object_type;
}

static void
gxsnmp_sha_init (GxsnmpSha *object)
{
  GxsnmpHash   *hash   = GXSNMP_HASH(object);
  GxsnmpDigest *digest = GXSNMP_DIGEST(object);

  hash->result    = (guint32 *) g_malloc(20);
  hash->hashlen   = 20;
  hash->hashname  = "SHA-1";
  digest->endianess = TRUE;

  if (hash->result)
    SHAInit(hash->result);
}

static void
gxsnmp_sha_class_init (GxsnmpShaClass *klass)
{
  GObjectClass      *object_class  = G_OBJECT_CLASS (klass);
  GxsnmpDigestClass *digest_class  = GXSNMP_DIGEST_CLASS (klass);
  GxsnmpHashClass   *hash_class    = GXSNMP_HASH_CLASS (klass);
  parent_class = g_type_class_peek_parent (klass);

  digest_class->transform = gxsnmp_sha_transform;
  hash_class->reset       = gxsnmp_sha_reset;
  object_class->finalize  = gxsnmp_sha_finalize;
}

static void
gxsnmp_sha_finalize (GObject *object)
{
  G_OBJECT_CLASS (parent_class)->finalize (object);
}

static void
gxsnmp_sha_transform (GxsnmpDigest *digest)
{
  GxsnmpHash *hash = GXSNMP_HASH (digest);

  if (hash->result)
    SHATransform(hash->result, digest->data);
}

static void
gxsnmp_sha_reset (GxsnmpHash *hash)
{
  GXSNMP_HASH_CLASS (parent_class)->reset (hash);

  if (hash->result)
    SHAInit(hash->result);
}

/* Initialize the SHA values */

static void
SHAInit(guint32 digest[5])
{
  /* Set the h-vars to their initial values */
  digest[ 0 ] = h0init;
  digest[ 1 ] = h1init;
  digest[ 2 ] = h2init;
  digest[ 3 ] = h3init;
  digest[ 4 ] = h4init;
}

/* Perform the SHA transformation.  Note that this code, like MD5, seems to
   break some optimizing compilers due to the complexity of the expressions
   and the size of the basic block.  It may be necessary to split it into
   sections, e.g. based on the four subrounds

   Note that this corrupts the shaInfo->data area */

static void 
SHATransform(guint32 *digest, guint32 *data )
{
  guint32 A, B, C, D, E;     /* Local vars */
  guint32 eData[ 16 ];       /* Expanded data */

  /* Set up first buffer and local data buffer */
  A = digest[ 0 ];
  B = digest[ 1 ];
  C = digest[ 2 ];
  D = digest[ 3 ];
  E = digest[ 4 ];
  g_memmove( eData, data, 64 );

  /* Heavy mangling, in 4 sub-rounds of 20 interations each. */
  subRound( A, B, C, D, E, f1, K1, eData[  0 ] );
  subRound( E, A, B, C, D, f1, K1, eData[  1 ] );
  subRound( D, E, A, B, C, f1, K1, eData[  2 ] );
  subRound( C, D, E, A, B, f1, K1, eData[  3 ] );
  subRound( B, C, D, E, A, f1, K1, eData[  4 ] );
  subRound( A, B, C, D, E, f1, K1, eData[  5 ] );
  subRound( E, A, B, C, D, f1, K1, eData[  6 ] );
  subRound( D, E, A, B, C, f1, K1, eData[  7 ] );
  subRound( C, D, E, A, B, f1, K1, eData[  8 ] );
  subRound( B, C, D, E, A, f1, K1, eData[  9 ] );
  subRound( A, B, C, D, E, f1, K1, eData[ 10 ] );
  subRound( E, A, B, C, D, f1, K1, eData[ 11 ] );
  subRound( D, E, A, B, C, f1, K1, eData[ 12 ] );
  subRound( C, D, E, A, B, f1, K1, eData[ 13 ] );
  subRound( B, C, D, E, A, f1, K1, eData[ 14 ] );
  subRound( A, B, C, D, E, f1, K1, eData[ 15 ] );
  subRound( E, A, B, C, D, f1, K1, expand( eData, 16 ) );
  subRound( D, E, A, B, C, f1, K1, expand( eData, 17 ) );
  subRound( C, D, E, A, B, f1, K1, expand( eData, 18 ) );
  subRound( B, C, D, E, A, f1, K1, expand( eData, 19 ) );

  subRound( A, B, C, D, E, f2, K2, expand( eData, 20 ) );
  subRound( E, A, B, C, D, f2, K2, expand( eData, 21 ) );
  subRound( D, E, A, B, C, f2, K2, expand( eData, 22 ) );
  subRound( C, D, E, A, B, f2, K2, expand( eData, 23 ) );
  subRound( B, C, D, E, A, f2, K2, expand( eData, 24 ) );
  subRound( A, B, C, D, E, f2, K2, expand( eData, 25 ) );
  subRound( E, A, B, C, D, f2, K2, expand( eData, 26 ) );
  subRound( D, E, A, B, C, f2, K2, expand( eData, 27 ) );
  subRound( C, D, E, A, B, f2, K2, expand( eData, 28 ) );
  subRound( B, C, D, E, A, f2, K2, expand( eData, 29 ) );
  subRound( A, B, C, D, E, f2, K2, expand( eData, 30 ) );
  subRound( E, A, B, C, D, f2, K2, expand( eData, 31 ) );
  subRound( D, E, A, B, C, f2, K2, expand( eData, 32 ) );
  subRound( C, D, E, A, B, f2, K2, expand( eData, 33 ) );
  subRound( B, C, D, E, A, f2, K2, expand( eData, 34 ) );
  subRound( A, B, C, D, E, f2, K2, expand( eData, 35 ) );
  subRound( E, A, B, C, D, f2, K2, expand( eData, 36 ) );
  subRound( D, E, A, B, C, f2, K2, expand( eData, 37 ) );
  subRound( C, D, E, A, B, f2, K2, expand( eData, 38 ) );
  subRound( B, C, D, E, A, f2, K2, expand( eData, 39 ) );

  subRound( A, B, C, D, E, f3, K3, expand( eData, 40 ) );
  subRound( E, A, B, C, D, f3, K3, expand( eData, 41 ) );
  subRound( D, E, A, B, C, f3, K3, expand( eData, 42 ) );
  subRound( C, D, E, A, B, f3, K3, expand( eData, 43 ) );
  subRound( B, C, D, E, A, f3, K3, expand( eData, 44 ) );
  subRound( A, B, C, D, E, f3, K3, expand( eData, 45 ) );
  subRound( E, A, B, C, D, f3, K3, expand( eData, 46 ) );
  subRound( D, E, A, B, C, f3, K3, expand( eData, 47 ) );
  subRound( C, D, E, A, B, f3, K3, expand( eData, 48 ) );
  subRound( B, C, D, E, A, f3, K3, expand( eData, 49 ) );
  subRound( A, B, C, D, E, f3, K3, expand( eData, 50 ) );
  subRound( E, A, B, C, D, f3, K3, expand( eData, 51 ) );
  subRound( D, E, A, B, C, f3, K3, expand( eData, 52 ) );
  subRound( C, D, E, A, B, f3, K3, expand( eData, 53 ) );
  subRound( B, C, D, E, A, f3, K3, expand( eData, 54 ) );
  subRound( A, B, C, D, E, f3, K3, expand( eData, 55 ) );
  subRound( E, A, B, C, D, f3, K3, expand( eData, 56 ) );
  subRound( D, E, A, B, C, f3, K3, expand( eData, 57 ) );
  subRound( C, D, E, A, B, f3, K3, expand( eData, 58 ) );
  subRound( B, C, D, E, A, f3, K3, expand( eData, 59 ) );

  subRound( A, B, C, D, E, f4, K4, expand( eData, 60 ) );
  subRound( E, A, B, C, D, f4, K4, expand( eData, 61 ) );
  subRound( D, E, A, B, C, f4, K4, expand( eData, 62 ) );
  subRound( C, D, E, A, B, f4, K4, expand( eData, 63 ) );
  subRound( B, C, D, E, A, f4, K4, expand( eData, 64 ) );
  subRound( A, B, C, D, E, f4, K4, expand( eData, 65 ) );
  subRound( E, A, B, C, D, f4, K4, expand( eData, 66 ) );
  subRound( D, E, A, B, C, f4, K4, expand( eData, 67 ) );
  subRound( C, D, E, A, B, f4, K4, expand( eData, 68 ) );
  subRound( B, C, D, E, A, f4, K4, expand( eData, 69 ) );
  subRound( A, B, C, D, E, f4, K4, expand( eData, 70 ) );
  subRound( E, A, B, C, D, f4, K4, expand( eData, 71 ) );
  subRound( D, E, A, B, C, f4, K4, expand( eData, 72 ) );
  subRound( C, D, E, A, B, f4, K4, expand( eData, 73 ) );
  subRound( B, C, D, E, A, f4, K4, expand( eData, 74 ) );
  subRound( A, B, C, D, E, f4, K4, expand( eData, 75 ) );
  subRound( E, A, B, C, D, f4, K4, expand( eData, 76 ) );
  subRound( D, E, A, B, C, f4, K4, expand( eData, 77 ) );
  subRound( C, D, E, A, B, f4, K4, expand( eData, 78 ) );
  subRound( B, C, D, E, A, f4, K4, expand( eData, 79 ) );

  /* Build message digest */
  digest[ 0 ] += A;
  digest[ 1 ] += B;
  digest[ 2 ] += C;
  digest[ 3 ] += D;
  digest[ 4 ] += E;
}

GxsnmpSha*   gxsnmp_sha_new()
{
  GxsnmpSha* sha;

  sha = g_object_new (gxsnmp_sha_get_type (), NULL);

  return sha;
}