view libtomcrypt/src/pk/dsa/dsa_verify_key.c @ 1629:258b57b208ae

Fix for issue successfull login of disabled user (#78) This commit introduces fix for scenario: 1. Root login disabled on dropbear 2. PAM authentication model enabled While login as root user, after prompt for password user is being notified about login failrue, but after second attempt of prompt for password within same session, login becames succesfull. Signed-off-by: Pawel Rapkiewicz <[email protected]>
author vincentto13 <33652988+vincentto13@users.noreply.github.com>
date Wed, 20 Mar 2019 15:03:40 +0100
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.
 */
#include "tomcrypt.h"

/**
   @file dsa_verify_key.c
   DSA implementation, verify a key, Tom St Denis
*/

#ifdef LTC_MDSA

/**
   Validate a DSA key

     Yeah, this function should've been called dsa_validate_key()
     in the first place and for compat-reasons we keep it
     as it was (for now).

   @param key   The key to validate
   @param stat  [out]  Result of test, 1==valid, 0==invalid
   @return CRYPT_OK if successful
*/
int dsa_verify_key(dsa_key *key, int *stat)
{
   int err;

   err = dsa_int_validate_primes(key, stat);
   if (err != CRYPT_OK || *stat == 0) return err;

   err = dsa_int_validate_pqg(key, stat);
   if (err != CRYPT_OK || *stat == 0) return err;

   return dsa_int_validate_xy(key, stat);
}

/**
   Non-complex part (no primality testing) of the validation
   of DSA params (p, q, g)

   @param key   The key to validate
   @param stat  [out]  Result of test, 1==valid, 0==invalid
   @return CRYPT_OK if successful
*/
int dsa_int_validate_pqg(dsa_key *key, int *stat)
{
   void *tmp1, *tmp2;
   int  err;

   LTC_ARGCHK(key  != NULL);
   LTC_ARGCHK(stat != NULL);
   *stat = 0;

   /* check q-order */
   if ( key->qord >= LTC_MDSA_MAX_GROUP || key->qord <= 15 ||
        (unsigned long)key->qord >= mp_unsigned_bin_size(key->p) ||
        (mp_unsigned_bin_size(key->p) - key->qord) >= LTC_MDSA_DELTA ) {
      return CRYPT_OK;
   }

   /* FIPS 186-4 chapter 4.1: 1 < g < p */
   if (mp_cmp_d(key->g, 1) != LTC_MP_GT || mp_cmp(key->g, key->p) != LTC_MP_LT) {
      return CRYPT_OK;
   }

   if ((err = mp_init_multi(&tmp1, &tmp2, NULL)) != CRYPT_OK)        { return err; }

   /* FIPS 186-4 chapter 4.1: q is a divisor of (p - 1) */
   if ((err = mp_sub_d(key->p, 1, tmp1)) != CRYPT_OK)                { goto error; }
   if ((err = mp_div(tmp1, key->q, tmp1, tmp2)) != CRYPT_OK)         { goto error; }
   if (mp_iszero(tmp2) != LTC_MP_YES) {
      err = CRYPT_OK;
      goto error;
   }

   /* FIPS 186-4 chapter 4.1: g is a generator of a subgroup of order q in
    * the multiplicative group of GF(p) - so we make sure that g^q mod p = 1
    */
   if ((err = mp_exptmod(key->g, key->q, key->p, tmp1)) != CRYPT_OK) { goto error; }
   if (mp_cmp_d(tmp1, 1) != LTC_MP_EQ) {
      err = CRYPT_OK;
      goto error;
   }

   err   = CRYPT_OK;
   *stat = 1;
error:
   mp_clear_multi(tmp2, tmp1, NULL);
   return err;
}

/**
   Primality testing of DSA params p and q

   @param key   The key to validate
   @param stat  [out]  Result of test, 1==valid, 0==invalid
   @return CRYPT_OK if successful
*/
int dsa_int_validate_primes(dsa_key *key, int *stat)
{
   int err, res;

   *stat = 0;
   LTC_ARGCHK(key  != NULL);
   LTC_ARGCHK(stat != NULL);

   /* key->q prime? */
   if ((err = mp_prime_is_prime(key->q, LTC_MILLER_RABIN_REPS, &res)) != CRYPT_OK) {
      return err;
   }
   if (res == LTC_MP_NO) {
      return CRYPT_OK;
   }

   /* key->p prime? */
   if ((err = mp_prime_is_prime(key->p, LTC_MILLER_RABIN_REPS, &res)) != CRYPT_OK) {
      return err;
   }
   if (res == LTC_MP_NO) {
      return CRYPT_OK;
   }

   *stat = 1;
   return CRYPT_OK;
}

/**
   Validation of a DSA key (x and y values)

   @param key   The key to validate
   @param stat  [out]  Result of test, 1==valid, 0==invalid
   @return CRYPT_OK if successful
*/
int dsa_int_validate_xy(dsa_key *key, int *stat)
{
   void *tmp;
   int  err;

   *stat = 0;
   LTC_ARGCHK(key  != NULL);
   LTC_ARGCHK(stat != NULL);

   /* 1 < y < p-1 */
   if ((err = mp_init(&tmp)) != CRYPT_OK) {
      return err;
   }
   if ((err = mp_sub_d(key->p, 1, tmp)) != CRYPT_OK) {
      goto error;
   }
   if (mp_cmp_d(key->y, 1) != LTC_MP_GT || mp_cmp(key->y, tmp) != LTC_MP_LT) {
      err = CRYPT_OK;
      goto error;
   }

   if (key->type == PK_PRIVATE) {
      /* FIPS 186-4 chapter 4.1: 0 < x < q */
      if (mp_cmp_d(key->x, 0) != LTC_MP_GT || mp_cmp(key->x, key->q) != LTC_MP_LT) {
         err = CRYPT_OK;
         goto error;
      }
      /* FIPS 186-4 chapter 4.1: y = g^x mod p */
      if ((err = mp_exptmod(key->g, key->x, key->p, tmp)) != CRYPT_OK) {
         goto error;
      }
      if (mp_cmp(tmp, key->y) != LTC_MP_EQ) {
         err = CRYPT_OK;
         goto error;
      }
   }
   else {
      /* with just a public key we cannot test y = g^x mod p therefore we
       * only test that y^q mod p = 1, which makes sure y is in g^x mod p
       */
      if ((err = mp_exptmod(key->y, key->q, key->p, tmp)) != CRYPT_OK) {
         goto error;
      }
      if (mp_cmp_d(tmp, 1) != LTC_MP_EQ) {
         err = CRYPT_OK;
         goto error;
      }
   }

   err   = CRYPT_OK;
   *stat = 1;
error:
   mp_clear(tmp);
   return err;
}

#endif

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