#include <stdio.h>
#include "cryptlib.h"
-#include "bn.h"
-#include "dh.h"
+#include <openssl/bn.h>
+#include <openssl/dh.h>
-/* Check that p is a strong prime and
- * if g is 2, 3 or 5, check that is is a suitable generator
+/*-
+ * Check that p is a safe prime and
+ * if g is 2, 3 or 5, check that it is a suitable generator
* where
* for 2, p mod 24 == 11
* for 3, p mod 12 == 5
* should hold.
*/
-int DH_check(dh,ret)
-DH *dh;
-int *ret;
+int DH_check(const DH *dh, int *ret)
{
int ok=0;
BN_CTX *ctx=NULL;
BN_ULONG l;
- BIGNUM *q=NULL;
+ BIGNUM *t1=NULL, *t2 = NULL;
*ret=0;
ctx=BN_CTX_new();
if (ctx == NULL) goto err;
- q=BN_new();
- if (q == NULL) goto err;
+ BN_CTX_start(ctx);
+ t1=BN_CTX_get(ctx);
+ if (t1 == NULL) goto err;
+ t2=BN_CTX_get(ctx);
+ if (t2 == NULL) goto err;
- if (BN_is_word(dh->g,DH_GENERATOR_2))
+ if (dh->q)
+ {
+ if (BN_cmp(dh->g, BN_value_one()) <= 0)
+ *ret|=DH_NOT_SUITABLE_GENERATOR;
+ else if (BN_cmp(dh->g, dh->p) >= 0)
+ *ret|=DH_NOT_SUITABLE_GENERATOR;
+ else
+ {
+ /* Check g^q == 1 mod p */
+ if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx))
+ goto err;
+ if (!BN_is_one(t1))
+ *ret|=DH_NOT_SUITABLE_GENERATOR;
+ }
+ if (!BN_is_prime_ex(dh->q,BN_prime_checks,ctx,NULL))
+ *ret|=DH_CHECK_Q_NOT_PRIME;
+ /* Check p == 1 mod q i.e. q divides p - 1 */
+ if (!BN_div(t1, t2, dh->p, dh->q, ctx))
+ goto err;
+ if (!BN_is_one(t2))
+ *ret|=DH_CHECK_INVALID_Q_VALUE;
+ if (dh->j && BN_cmp(dh->j, t1))
+ *ret|=DH_CHECK_INVALID_J_VALUE;
+
+ }
+ else if (BN_is_word(dh->g,DH_GENERATOR_2))
{
l=BN_mod_word(dh->p,24);
if (l != 11) *ret|=DH_NOT_SUITABLE_GENERATOR;
}
-/* else if (BN_is_word(dh->g,DH_GENERATOR_3))
+#if 0
+ else if (BN_is_word(dh->g,DH_GENERATOR_3))
{
l=BN_mod_word(dh->p,12);
if (l != 5) *ret|=DH_NOT_SUITABLE_GENERATOR;
- }*/
+ }
+#endif
else if (BN_is_word(dh->g,DH_GENERATOR_5))
{
l=BN_mod_word(dh->p,10);
else
*ret|=DH_UNABLE_TO_CHECK_GENERATOR;
- if (!BN_is_prime(dh->p,BN_prime_checks,NULL,ctx,NULL))
+ if (!BN_is_prime_ex(dh->p,BN_prime_checks,ctx,NULL))
*ret|=DH_CHECK_P_NOT_PRIME;
- else
+ else if (!dh->q)
{
- if (!BN_rshift1(q,dh->p)) goto err;
- if (!BN_is_prime(q,BN_prime_checks,NULL,ctx,NULL))
- *ret|=DH_CHECK_P_NOT_STRONG_PRIME;
+ if (!BN_rshift1(t1,dh->p)) goto err;
+ if (!BN_is_prime_ex(t1,BN_prime_checks,ctx,NULL))
+ *ret|=DH_CHECK_P_NOT_SAFE_PRIME;
}
ok=1;
err:
- if (ctx != NULL) BN_CTX_free(ctx);
+ if (ctx != NULL)
+ {
+ BN_CTX_end(ctx);
+ BN_CTX_free(ctx);
+ }
+ return(ok);
+ }
+
+int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
+ {
+ int ok=0;
+ BIGNUM *q=NULL;
+
+ *ret=0;
+ q=BN_new();
+ if (q == NULL) goto err;
+ BN_set_word(q,1);
+ if (BN_cmp(pub_key,q)<=0)
+ *ret|=DH_CHECK_PUBKEY_TOO_SMALL;
+ BN_copy(q,dh->p);
+ BN_sub_word(q,1);
+ if (BN_cmp(pub_key,q)>=0)
+ *ret|=DH_CHECK_PUBKEY_TOO_LARGE;
+
+ ok = 1;
+err:
if (q != NULL) BN_free(q);
return(ok);
}