X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;f=libtomcrypt%2Fsrc%2Fpk%2Fdsa%2Fdsa_verify_key.c;fp=libtomcrypt%2Fsrc%2Fpk%2Fdsa%2Fdsa_verify_key.c;h=258e6cbe488e68a59315a5cba4a9db3bc3d9b713;hb=66bc25938679f1d6a1d1200f329093d82a5e99b4;hp=0000000000000000000000000000000000000000;hpb=a52ee0733f420ca20224049260d6fc5cf7d8f621;p=zpackage

diff --git a/libtomcrypt/src/pk/dsa/dsa_verify_key.c b/libtomcrypt/src/pk/dsa/dsa_verify_key.c
new file mode 100644
index 0000000..258e6cb
--- /dev/null
+++ b/libtomcrypt/src/pk/dsa/dsa_verify_key.c
@@ -0,0 +1,199 @@
+/* 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
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */