botan: Simplify DH/ECDH key derivation

src/libstrongswan/plugins/botan/botan_diffie_hellman.c

@@ -97,37 +97,14 @@ bool load_private_key(private_botan_diffie_hellman_t *this, chunk_t value)
 METHOD(diffie_hellman_t, set_other_public_value, bool,
 	private_botan_diffie_hellman_t *this, chunk_t value)
 {
-	botan_pk_op_ka_t op;
-
 	if (!diffie_hellman_verify_value(this->group, value))
 	{
 		return FALSE;
 	}
 
-	if (botan_pk_op_key_agreement_create(&op, this->dh_key, "Raw", 0))
-	{
-		return FALSE;
-	}
-
 	chunk_clear(&this->shared_secret);
 
-	if (botan_pk_op_key_agreement_size(op, &this->shared_secret.len))
+	return botan_dh_key_derivation(this->dh_key, value, &this->shared_secret);
-	{
-		botan_pk_op_key_agreement_destroy(op);
-		return FALSE;
-	}
-
-	this->shared_secret = chunk_alloc(this->shared_secret.len);
-	if (botan_pk_op_key_agreement(op, this->shared_secret.ptr,
-								  &this->shared_secret.len, value.ptr,
-								  value.len, NULL, 0))
-	{
-		chunk_clear(&this->shared_secret);
-		botan_pk_op_key_agreement_destroy(op);
-		return FALSE;
-	}
-	botan_pk_op_key_agreement_destroy(op);
-	return TRUE;
 }
 
 METHOD(diffie_hellman_t, get_my_public_value, bool,

src/libstrongswan/plugins/botan/botan_ec_diffie_hellman.c

@@ -69,40 +69,17 @@ struct private_botan_ec_diffie_hellman_t {
 METHOD(diffie_hellman_t, set_other_public_value, bool,
 	private_botan_ec_diffie_hellman_t *this, chunk_t value)
 {
-	botan_pk_op_ka_t ka;
-
 	if (!diffie_hellman_verify_value(this->group, value))
 	{
 		return FALSE;
 	}
 
-	if (botan_pk_op_key_agreement_create(&ka, this->key, "Raw", 0))
-	{
-		return FALSE;
-	}
-
 	chunk_clear(&this->shared_secret);
 
-	if (botan_pk_op_key_agreement_size(ka, &this->shared_secret.len))
-	{
-		botan_pk_op_key_agreement_destroy(ka);
-		return FALSE;
-	}
-
 	/* prepend 0x04 to indicate uncompressed point format */
 	value = chunk_cata("cc", chunk_from_chars(0x04), value);
 
-	this->shared_secret = chunk_alloc(this->shared_secret.len);
+	return botan_dh_key_derivation(this->key, value, &this->shared_secret);
-	if (botan_pk_op_key_agreement(ka, this->shared_secret.ptr,
-								  &this->shared_secret.len, value.ptr,
-								  value.len, NULL, 0))
-	{
-		chunk_clear(&this->shared_secret);
-		botan_pk_op_key_agreement_destroy(ka);
-		return FALSE;
-	}
-	botan_pk_op_key_agreement_destroy(ka);
-	return TRUE;
 }
 
 METHOD(diffie_hellman_t, get_my_public_value, bool,

src/libstrongswan/plugins/botan/botan_util.c

@@ -259,3 +259,33 @@ bool botan_get_signature(botan_privkey_t key, const char *scheme,
 	botan_pk_op_sign_destroy(sign_op);
 	return TRUE;
 }
+
+/*
+ * Described in header
+ */
+bool botan_dh_key_derivation(botan_privkey_t key, chunk_t pub, chunk_t *secret)
+{
+	botan_pk_op_ka_t ka;
+
+	if (botan_pk_op_key_agreement_create(&ka, key, "Raw", 0))
+	{
+		return FALSE;
+	}
+
+	if (botan_pk_op_key_agreement_size(ka, &secret->len))
+	{
+		botan_pk_op_key_agreement_destroy(ka);
+		return FALSE;
+	}
+
+	*secret = chunk_alloc(secret->len);
+	if (botan_pk_op_key_agreement(ka, secret->ptr, &secret->len, pub.ptr,
+								  pub.len, NULL, 0))
+	{
+		chunk_clear(secret);
+		botan_pk_op_key_agreement_destroy(ka);
+		return FALSE;
+	}
+	botan_pk_op_key_agreement_destroy(ka);
+	return TRUE;
+}

src/libstrongswan/plugins/botan/botan_util.h

@@ -100,4 +100,17 @@ bool botan_get_fingerprint(botan_pubkey_t pubkey, void *cache,
 bool botan_get_signature(botan_privkey_t key, const char *scheme,
 						 chunk_t data, chunk_t *signature);
 
+/**
+ * Do the Diffie-Hellman key derivation using the given private key and public
+ * value.
+ *
+ * Note that the public value is not verified in this function.
+ *
+ * @param key		DH private key
+ * @param pub		other's public value
+ * @param secret	the derived secret (allocated on success)
+ * @return			TRUE if derivation was successful
+ */
+bool botan_dh_key_derivation(botan_privkey_t key, chunk_t pub, chunk_t *secret);
+
 #endif /** BOTAN_UTIL_H_ @}*/