mark all block comments that need format preserving so that
[openssl.git] / crypto / dh / dh_check.c
index 65602e4..0acd775 100644 (file)
 
 #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);
@@ -104,17 +133,42 @@ int *ret;
        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);
        }