refining changeset 4483 by introducing charon.dh_exponent_ansi_x9_42 key
[strongswan.git] / src / libstrongswan / plugins / openssl / openssl_diffie_hellman.c
index 217b1aa..f309236 100644 (file)
@@ -38,23 +38,28 @@ struct modulus_entry_t {
        BIGNUM *(*get_prime)(BIGNUM *bn);
        
        /* 
+        * Optimum length of exponent in bits.
+        */     
+       long opt_exponent_len;
+
+       /* 
         * Generator value.
         */     
        u_int16_t generator;
 };
 
 /**
- * All supported modulus values.
+ * All supported modulus values - optimum exponent size according to RFC 3526.
  */
 static modulus_entry_t modulus_entries[] = {
-       {MODP_768_BIT,  get_rfc2409_prime_768,  2},
-       {MODP_1024_BIT, get_rfc2409_prime_1024, 2},
-       {MODP_1536_BIT, get_rfc3526_prime_1536, 2},
-       {MODP_2048_BIT, get_rfc3526_prime_2048, 2},
-       {MODP_3072_BIT, get_rfc3526_prime_3072, 2},
-       {MODP_4096_BIT, get_rfc3526_prime_4096, 2},
-       {MODP_6144_BIT, get_rfc3526_prime_6144, 2},
-       {MODP_8192_BIT, get_rfc3526_prime_8192, 2},
+       {MODP_768_BIT,  get_rfc2409_prime_768,  256, 2},
+       {MODP_1024_BIT, get_rfc2409_prime_1024, 256, 2},
+       {MODP_1536_BIT, get_rfc3526_prime_1536, 256, 2},
+       {MODP_2048_BIT, get_rfc3526_prime_2048, 384, 2},
+       {MODP_3072_BIT, get_rfc3526_prime_3072, 384, 2},
+       {MODP_4096_BIT, get_rfc3526_prime_4096, 512, 2},
+       {MODP_6144_BIT, get_rfc3526_prime_6144, 512, 2},
+       {MODP_8192_BIT, get_rfc3526_prime_8192, 512, 2},
 };
 
 typedef struct private_openssl_diffie_hellman_t private_openssl_diffie_hellman_t;
@@ -83,6 +88,11 @@ struct private_openssl_diffie_hellman_t {
         */
        BIGNUM *pub_key;
        
+       /* 
+        * Optimum length of exponent in bits.
+        */     
+       long opt_exponent_len;
+
        /**
         * Shared secret
         */
@@ -180,6 +190,7 @@ static status_t set_modulus(private_openssl_diffie_hellman_t *this)
                        this->dh->p = modulus_entries[i].get_prime(NULL);
                        this->dh->g = BN_new();
                        BN_set_word(this->dh->g, modulus_entries[i].generator);
+                       this->opt_exponent_len = modulus_entries[i].opt_exponent_len;
                        return SUCCESS;
                }
        }
@@ -202,6 +213,7 @@ static void destroy(private_openssl_diffie_hellman_t *this)
  */
 openssl_diffie_hellman_t *openssl_diffie_hellman_create(diffie_hellman_group_t group)
 {
+       bool ansi_x9_42;
        private_openssl_diffie_hellman_t *this = malloc_thing(private_openssl_diffie_hellman_t);
        
        this->public.dh.get_shared_secret = (status_t (*)(diffie_hellman_t *, chunk_t *)) get_shared_secret;
@@ -217,8 +229,7 @@ openssl_diffie_hellman_t *openssl_diffie_hellman_create(diffie_hellman_group_t g
                free(this);
                return NULL;
        }
-       this->dh->length = DH_EXPONENT_ENTROPY_SIZE;
-       
+
        this->group = group;
        this->computed = FALSE;
        
@@ -232,12 +243,17 @@ openssl_diffie_hellman_t *openssl_diffie_hellman_create(diffie_hellman_group_t g
                return NULL;
        }
        
+       ansi_x9_42 = lib->settings->get_bool(lib->settings,
+                                        "charon.dh_exponent_ansi_x9_42", TRUE);
+       this->dh->length = (ansi_x9_42) ? 0 : this->opt_exponent_len;
+
        /* generate my public and private values */
        if (!DH_generate_key(this->dh))
        {
                destroy(this);
                return NULL;
        }
+       DBG2("size of DH secret exponent: %d bits", BN_num_bits(this->dh->priv_key));
        
        return &this->public;
 }