Add create_nonce_gen function to keymat interface

This function returns a nonce generator object.

src/libcharon/sa/ikev1/keymat_v1.c

@@ -985,6 +985,12 @@ METHOD(keymat_t, create_dh, diffie_hellman_t*,
 	return lib->crypto->create_dh(lib->crypto, group);
 }
 
+METHOD(keymat_t, create_nonce_gen, nonce_gen_t*,
+	private_keymat_v1_t *this)
+{
+	return lib->crypto->create_nonce_gen(lib->crypto);
+}
+
 METHOD(keymat_t, get_aead, aead_t*,
 	private_keymat_v1_t *this, bool in)
 {
@@ -1019,6 +1025,7 @@ keymat_v1_t *keymat_v1_create(bool initiator)
 			.keymat = {
 				.get_version = _get_version,
 				.create_dh = _create_dh,
+				.create_nonce_gen = _create_nonce_gen,
 				.get_aead = _get_aead,
 				.destroy = _destroy,
 			},

src/libcharon/sa/ikev2/keymat_v2.c

@@ -83,6 +83,12 @@ METHOD(keymat_t, create_dh, diffie_hellman_t*,
 	return lib->crypto->create_dh(lib->crypto, group);
 }
 
+METHOD(keymat_t, create_nonce_gen, nonce_gen_t*,
+	private_keymat_v2_t *this)
+{
+	return lib->crypto->create_nonce_gen(lib->crypto);
+}
+
 /**
  * Derive IKE keys for a combined AEAD algorithm
  */
@@ -571,6 +577,7 @@ keymat_v2_t *keymat_v2_create(bool initiator)
 			.keymat = {
 				.get_version = _get_version,
 				.create_dh = _create_dh,
+				.create_nonce_gen = _create_nonce_gen,
 				.get_aead = _get_aead,
 				.destroy = _destroy,
 			},

src/libcharon/sa/keymat.h

@@ -61,6 +61,16 @@ struct keymat_t {
 	diffie_hellman_t* (*create_dh)(keymat_t *this,
 								   diffie_hellman_group_t group);
 
+	/**
+	 * Create a nonce generator object.
+	 *
+	 * The nonce generator can be used to create nonces needed during IKE/CHILD
+	 * SA establishment or rekeying.
+	 *
+	 * @return				nonce generator object
+	 */
+	nonce_gen_t* (*create_nonce_gen)(keymat_t *this);
+
 	/*
 	 * Get a AEAD transform to en-/decrypt and sign/verify IKE messages.
 	 *