Add nonce generator interface

Nonce generators (nonce_gen_t) can be used to get or allocate nonces.

Users can request nonce generators from the crypto factory while nonce
plugins register/remove themselves to/from the crypto factory.

src/libstrongswan/crypto/crypto_factory.h

@@ -30,6 +30,7 @@ typedef struct crypto_factory_t crypto_factory_t;
 #include <crypto/hashers/hasher.h>
 #include <crypto/prfs/prf.h>
 #include <crypto/rngs/rng.h>
+#include <crypto/nonce_gen.h>
 #include <crypto/diffie_hellman.h>
 #include <crypto/transform.h>
 
@@ -65,6 +66,11 @@ typedef prf_t* (*prf_constructor_t)(pseudo_random_function_t algo);
  */
 typedef rng_t* (*rng_constructor_t)(rng_quality_t quality);
 
+/**
+ * Constructor function for nonce generators
+ */
+typedef nonce_gen_t* (*nonce_gen_constructor_t)();
+
 /**
  * Constructor function for diffie hellman
  *
@@ -131,6 +137,13 @@ struct crypto_factory_t {
 	 */
 	rng_t* (*create_rng)(crypto_factory_t *this, rng_quality_t quality);
 
+	/**
+	 * Create a nonce generator instance.
+	 *
+	 * @return				nonce_gen_t instance, NULL if not supported
+	 */
+	nonce_gen_t* (*create_nonce_gen)(crypto_factory_t *this);
+
 	/**
 	 * Create a diffie hellman instance.
 	 *
@@ -252,6 +265,23 @@ struct crypto_factory_t {
 	 */
 	void (*remove_rng)(crypto_factory_t *this, rng_constructor_t create);
 
+	/**
+	 * Register a nonce generator.
+	 *
+	 * @param plugin_name	plugin that registered this algorithm
+	 * @param create		constructor function for that nonce generator
+	 */
+	void (*add_nonce_gen)(crypto_factory_t *this, const char *plugin_name,
+						  nonce_gen_constructor_t create);
+
+	/**
+	 * Unregister a nonce generator.
+	 *
+	 * @param create		constructor function to unregister
+	 */
+	void (*remove_nonce_gen)(crypto_factory_t *this,
+							 nonce_gen_constructor_t create);
+
 	/**
 	 * Register a diffie hellman constructor.
 	 *