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view libtomcrypt/src/pk/ecc/ltc_ecc_projective_add_point.c @ 1715:3974f087d9c0

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Disallow leading lines before the ident for server (#102) Per RFC4253 4.2 clients must be able to process other lines of data before the version string, server behavior is not defined neither with MUST/SHOULD nor with MAY. If server process up to 50 lines too - it may cause too long hanging session with invalid/evil client that consume host resources and potentially may lead to DDoS on poor embedded boxes. Let's require first line from client to be version string and fail early if it's not - matches both RFC and real OpenSSH behavior.
author Vladislav Grishenko <themiron@users.noreply.github.com>
date Mon, 15 Jun 2020 18:22:18 +0500
parents 6dba84798cd5
children
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 */

/* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
 *
 * All curves taken from NIST recommendation paper of July 1999
 * Available at http://csrc.nist.gov/cryptval/dss.htm
 */
#include "tomcrypt.h"

/**
  @file ltc_ecc_projective_add_point.c
  ECC Crypto, Tom St Denis
*/

#if defined(LTC_MECC) && (!defined(LTC_MECC_ACCEL) || defined(LTM_DESC))

/**
   Add two ECC points
   @param P        The point to add
   @param Q        The point to add
   @param R        [out] The destination of the double
   @param modulus  The modulus of the field the ECC curve is in
   @param mp       The "b" value from montgomery_setup()
   @return CRYPT_OK on success
*/
int ltc_ecc_projective_add_point(ecc_point *P, ecc_point *Q, ecc_point *R, void *modulus, void *mp)
{
   void  *t1, *t2, *x, *y, *z;
   int    err;

   LTC_ARGCHK(P       != NULL);
   LTC_ARGCHK(Q       != NULL);
   LTC_ARGCHK(R       != NULL);
   LTC_ARGCHK(modulus != NULL);
   LTC_ARGCHK(mp      != NULL);

   if ((err = mp_init_multi(&t1, &t2, &x, &y, &z, NULL)) != CRYPT_OK) {
      return err;
   }

   /* should we dbl instead? */
   if ((err = mp_sub(modulus, Q->y, t1)) != CRYPT_OK)                          { goto done; }

   if ( (mp_cmp(P->x, Q->x) == LTC_MP_EQ) &&
        (Q->z != NULL && mp_cmp(P->z, Q->z) == LTC_MP_EQ) &&
        (mp_cmp(P->y, Q->y) == LTC_MP_EQ || mp_cmp(P->y, t1) == LTC_MP_EQ)) {
        mp_clear_multi(t1, t2, x, y, z, NULL);
        return ltc_ecc_projective_dbl_point(P, R, modulus, mp);
   }

   if ((err = mp_copy(P->x, x)) != CRYPT_OK)                                   { goto done; }
   if ((err = mp_copy(P->y, y)) != CRYPT_OK)                                   { goto done; }
   if ((err = mp_copy(P->z, z)) != CRYPT_OK)                                   { goto done; }

   /* if Z is one then these are no-operations */
   if (Q->z != NULL) {
      /* T1 = Z' * Z' */
      if ((err = mp_sqr(Q->z, t1)) != CRYPT_OK)                                { goto done; }
      if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK)           { goto done; }
      /* X = X * T1 */
      if ((err = mp_mul(t1, x, x)) != CRYPT_OK)                                { goto done; }
      if ((err = mp_montgomery_reduce(x, modulus, mp)) != CRYPT_OK)            { goto done; }
      /* T1 = Z' * T1 */
      if ((err = mp_mul(Q->z, t1, t1)) != CRYPT_OK)                            { goto done; }
      if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK)           { goto done; }
      /* Y = Y * T1 */
      if ((err = mp_mul(t1, y, y)) != CRYPT_OK)                                { goto done; }
      if ((err = mp_montgomery_reduce(y, modulus, mp)) != CRYPT_OK)            { goto done; }
   }

   /* T1 = Z*Z */
   if ((err = mp_sqr(z, t1)) != CRYPT_OK)                                      { goto done; }
   if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK)              { goto done; }
   /* T2 = X' * T1 */
   if ((err = mp_mul(Q->x, t1, t2)) != CRYPT_OK)                               { goto done; }
   if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK)              { goto done; }
   /* T1 = Z * T1 */
   if ((err = mp_mul(z, t1, t1)) != CRYPT_OK)                                  { goto done; }
   if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK)              { goto done; }
   /* T1 = Y' * T1 */
   if ((err = mp_mul(Q->y, t1, t1)) != CRYPT_OK)                               { goto done; }
   if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK)              { goto done; }

   /* Y = Y - T1 */
   if ((err = mp_sub(y, t1, y)) != CRYPT_OK)                                   { goto done; }
   if (mp_cmp_d(y, 0) == LTC_MP_LT) {
      if ((err = mp_add(y, modulus, y)) != CRYPT_OK)                           { goto done; }
   }
   /* T1 = 2T1 */
   if ((err = mp_add(t1, t1, t1)) != CRYPT_OK)                                 { goto done; }
   if (mp_cmp(t1, modulus) != LTC_MP_LT) {
      if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK)                         { goto done; }
   }
   /* T1 = Y + T1 */
   if ((err = mp_add(t1, y, t1)) != CRYPT_OK)                                  { goto done; }
   if (mp_cmp(t1, modulus) != LTC_MP_LT) {
      if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK)                         { goto done; }
   }
   /* X = X - T2 */
   if ((err = mp_sub(x, t2, x)) != CRYPT_OK)                                   { goto done; }
   if (mp_cmp_d(x, 0) == LTC_MP_LT) {
      if ((err = mp_add(x, modulus, x)) != CRYPT_OK)                           { goto done; }
   }
   /* T2 = 2T2 */
   if ((err = mp_add(t2, t2, t2)) != CRYPT_OK)                                 { goto done; }
   if (mp_cmp(t2, modulus) != LTC_MP_LT) {
      if ((err = mp_sub(t2, modulus, t2)) != CRYPT_OK)                         { goto done; }
   }
   /* T2 = X + T2 */
   if ((err = mp_add(t2, x, t2)) != CRYPT_OK)                                  { goto done; }
   if (mp_cmp(t2, modulus) != LTC_MP_LT) {
      if ((err = mp_sub(t2, modulus, t2)) != CRYPT_OK)                         { goto done; }
   }

   /* if Z' != 1 */
   if (Q->z != NULL) {
      /* Z = Z * Z' */
      if ((err = mp_mul(z, Q->z, z)) != CRYPT_OK)                              { goto done; }
      if ((err = mp_montgomery_reduce(z, modulus, mp)) != CRYPT_OK)            { goto done; }
   }

   /* Z = Z * X */
   if ((err = mp_mul(z, x, z)) != CRYPT_OK)                                    { goto done; }
   if ((err = mp_montgomery_reduce(z, modulus, mp)) != CRYPT_OK)               { goto done; }

   /* T1 = T1 * X  */
   if ((err = mp_mul(t1, x, t1)) != CRYPT_OK)                                  { goto done; }
   if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK)              { goto done; }
   /* X = X * X */
   if ((err = mp_sqr(x, x)) != CRYPT_OK)                                       { goto done; }
   if ((err = mp_montgomery_reduce(x, modulus, mp)) != CRYPT_OK)               { goto done; }
   /* T2 = T2 * x */
   if ((err = mp_mul(t2, x, t2)) != CRYPT_OK)                                  { goto done; }
   if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK)              { goto done; }
   /* T1 = T1 * X  */
   if ((err = mp_mul(t1, x, t1)) != CRYPT_OK)                                  { goto done; }
   if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK)              { goto done; }

   /* X = Y*Y */
   if ((err = mp_sqr(y, x)) != CRYPT_OK)                                       { goto done; }
   if ((err = mp_montgomery_reduce(x, modulus, mp)) != CRYPT_OK)               { goto done; }
   /* X = X - T2 */
   if ((err = mp_sub(x, t2, x)) != CRYPT_OK)                                   { goto done; }
   if (mp_cmp_d(x, 0) == LTC_MP_LT) {
      if ((err = mp_add(x, modulus, x)) != CRYPT_OK)                           { goto done; }
   }

   /* T2 = T2 - X */
   if ((err = mp_sub(t2, x, t2)) != CRYPT_OK)                                  { goto done; }
   if (mp_cmp_d(t2, 0) == LTC_MP_LT) {
      if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK)                         { goto done; }
   }
   /* T2 = T2 - X */
   if ((err = mp_sub(t2, x, t2)) != CRYPT_OK)                                  { goto done; }
   if (mp_cmp_d(t2, 0) == LTC_MP_LT) {
      if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK)                         { goto done; }
   }
   /* T2 = T2 * Y */
   if ((err = mp_mul(t2, y, t2)) != CRYPT_OK)                                  { goto done; }
   if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK)              { goto done; }
   /* Y = T2 - T1 */
   if ((err = mp_sub(t2, t1, y)) != CRYPT_OK)                                  { goto done; }
   if (mp_cmp_d(y, 0) == LTC_MP_LT) {
      if ((err = mp_add(y, modulus, y)) != CRYPT_OK)                           { goto done; }
   }
   /* Y = Y/2 */
   if (mp_isodd(y)) {
      if ((err = mp_add(y, modulus, y)) != CRYPT_OK)                           { goto done; }
   }
   if ((err = mp_div_2(y, y)) != CRYPT_OK)                                     { goto done; }

   if ((err = mp_copy(x, R->x)) != CRYPT_OK)                                   { goto done; }
   if ((err = mp_copy(y, R->y)) != CRYPT_OK)                                   { goto done; }
   if ((err = mp_copy(z, R->z)) != CRYPT_OK)                                   { goto done; }

   err = CRYPT_OK;
done:
   mp_clear_multi(t1, t2, x, y, z, NULL);
   return err;
}

#endif

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