aead: Create AEAD using traditional transforms with an explicit IV generator

Real AEADs directly provide a suitable IV generator, but traditional crypters
do not. For some (stream) ciphers, we should use sequential IVs, for which
we pass an appropriate generator to the AEAD wrapper.

src/libstrongswan/crypto/aead.c

@@ -172,7 +172,7 @@ METHOD(aead_t, destroy, void,
 /**
  * See header
  */
-aead_t *aead_create(crypter_t *crypter, signer_t *signer)
+aead_t *aead_create(crypter_t *crypter, signer_t *signer, iv_gen_t *iv_gen)
 {
 	private_aead_t *this;
 
@@ -190,7 +190,7 @@ aead_t *aead_create(crypter_t *crypter, signer_t *signer)
 		},
 		.crypter = crypter,
 		.signer = signer,
-		.iv_gen = iv_gen_rand_create(),
+		.iv_gen = iv_gen,
 	);
 
 	return &this->public;

src/libstrongswan/crypto/aead.h

@@ -135,8 +135,9 @@ struct aead_t {
  *
  * @param crypter		encryption transform for this aead
  * @param signer		integrity transform for this aead
+ * @param iv_gen		suitable IV generator for encryption algorithm
  * @return				aead transform
  */
-aead_t *aead_create(crypter_t *crypter, signer_t *signer);
+aead_t *aead_create(crypter_t *crypter, signer_t *signer, iv_gen_t *iv_gen);
 
 #endif /** AEAD_H_ @}*/