/**
 * @file authenticator.c
 *
 * @brief Implementation of authenticator_t.
 *
 */

/*
 * Copyright (C) 2005 Jan Hutter, Martin Willi
 * Hochschule fuer Technik Rapperswil
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 */

#include <string.h>

#include "authenticator.h"

#include <daemon.h>

/**
 * Key pad for the AUTH method SHARED_KEY_MESSAGE_INTEGRITY_CODE.
 */
#define IKEV2_KEY_PAD "Key Pad for IKEv2"


typedef struct private_authenticator_t private_authenticator_t;

/**
 * Private data of an authenticator_t object.
 */
struct private_authenticator_t {

	/**
	 * Public authenticator_t interface.
	 */
	authenticator_t public;

	/**
	 * Assigned IKE_SA. Needed to get objects of type prf_t and logger_t.
	 */
	ike_sa_t *ike_sa;
	
	/**
	 * PRF taken from the IKE_SA.
	 */
	prf_t *prf;

	/**
	 * A logger for.
	 * 
	 * Using logger of IKE_SA.
	 */
	logger_t *logger;
	
	/**
	 * @brief Creates the octets which are signed (RSA) or MACed (shared secret) as described in section 
	 * 2.15 of RFC.
	 * 
	 * @param this				calling object
	 * @param last_message		the last message to include in created octets 
	 * 							(either binary form of IKE_SA_INIT request or IKE_SA_INIT response)
	 * @param other_nonce		Nonce data received from other peer
	 * @param my_id				id_payload_t object representing an ID payload
	 * @param initiator			Type of peer. TRUE, if it is original initiator, FALSE otherwise
	 * @return					octets as described in section 2.15. Memory gets allocated and has to get 
	 * 							destroyed by caller.
	 */
	chunk_t (*allocate_octets) (private_authenticator_t *this,
								chunk_t last_message,
								chunk_t other_nonce,
								id_payload_t *my_id,
								bool initiator);
	
	/**
	 * @brief Creates the AUTH data using auth method SHARED_KEY_MESSAGE_INTEGRITY_CODE.
	 * 
	 * @param this				calling object
	 * @param last_message		the last message
	 * 							(either binary form of IKE_SA_INIT request or IKE_SA_INIT response)
	 * @param nonce				Nonce data to include in auth data compution
	 * @param id_payload		id_payload_t object representing an ID payload
	 * @param initiator			Type of peer. TRUE, if it is original initiator, FALSE otherwise
	 * @param shared_secret		shared secret as chunk_t. If shared secret is a string,
	 * 							the NULL termination is not included.
	 * @return					AUTH data as dscribed in section 2.15 for 
	 * 							AUTH method SHARED_KEY_MESSAGE_INTEGRITY_CODE.
	 * 							Memory gets allocated and has to get destroyed by caller.
	 */
	chunk_t (*build_preshared_secret_signature) (private_authenticator_t *this,
												 chunk_t last_message,
												 chunk_t nonce,
												 id_payload_t *id_payload,
												 bool initiator,
												 chunk_t preshared_secret);
};

/**
 * Implementation of private_authenticator_t.allocate_octets.
 */
static chunk_t allocate_octets(private_authenticator_t *this,
								chunk_t last_message, 
								chunk_t other_nonce,
								id_payload_t *my_id,
								bool initiator)
{
	prf_t *prf;
	chunk_t id_chunk = my_id->get_data(my_id);
	u_int8_t id_with_header[4 + id_chunk.len];
	/*
	 * IKEv2 for linux (http://sf.net/projects/ikev2/) 
	 * is not compatible with IKEv2 Draft and so not compatible with this
	 * implementation, cause AUTH data are computed without
	 * ID type and the three reserved bytes.
	 */
	chunk_t id_with_header_chunk = {ptr:id_with_header, len: sizeof(id_with_header)};
	u_int8_t *current_pos;
	chunk_t octets;
	
	id_with_header[0] = my_id->get_id_type(my_id);
	id_with_header[1] = 0x00;
	id_with_header[2] = 0x00;
	id_with_header[3] = 0x00;
	memcpy(id_with_header + 4,id_chunk.ptr,id_chunk.len);
	
	if (initiator)
	{
		prf = this->ike_sa->get_prf_auth_i(this->ike_sa);
	}
	else
	{
		prf = this->ike_sa->get_prf_auth_r(this->ike_sa);
	}
	
	/* 4 bytes are id type and reserved fields of id payload */
	octets.len = last_message.len + other_nonce.len + prf->get_block_size(prf);
	octets.ptr = malloc(octets.len);
	current_pos = octets.ptr;
	memcpy(current_pos,last_message.ptr,last_message.len);
	current_pos += last_message.len;
	memcpy(current_pos,other_nonce.ptr,other_nonce.len);
	current_pos += other_nonce.len;
	prf->get_bytes(prf, id_with_header_chunk, current_pos);
	
	this->logger->log_chunk(this->logger,RAW | LEVEL2, "octets (message + nonce + prf(Sk_px,Idx)",octets);
	return octets;
}

/**
 * Implementation of private_authenticator_t.build_preshared_secret_signature.
 */
static chunk_t build_preshared_secret_signature(private_authenticator_t *this,
															chunk_t last_message,
															chunk_t nonce,
															id_payload_t *id_payload,
															bool initiator,
															chunk_t preshared_secret)
{
	chunk_t key_pad = {ptr: IKEV2_KEY_PAD, len:strlen(IKEV2_KEY_PAD)};
	u_int8_t key_buffer[this->prf->get_block_size(this->prf)];
	chunk_t key = {ptr: key_buffer, len: sizeof(key_buffer)};
	chunk_t auth_data;

	chunk_t octets = this->allocate_octets(this,last_message,nonce,id_payload,initiator);
	
	/* AUTH = prf(prf(Shared Secret,"Key Pad for IKEv2"), <msg octets>) */
	this->prf->set_key(this->prf, preshared_secret);
	this->prf->get_bytes(this->prf, key_pad, key_buffer);
	this->prf->set_key(this->prf, key);
	this->prf->allocate_bytes(this->prf, octets, &auth_data);
	chunk_free(&octets);
	this->logger->log_chunk(this->logger,RAW | LEVEL2, "authenticated data",auth_data);

	return auth_data;
}

/**
 * Implementation of authenticator_t.verify_auth_data.
 */
static status_t verify_auth_data (private_authenticator_t *this,
									auth_payload_t *auth_payload,
									chunk_t last_received_packet,
									chunk_t my_nonce,
									id_payload_t *other_id_payload,
									bool initiator)
{
	switch(auth_payload->get_auth_method(auth_payload))
	{
		case SHARED_KEY_MESSAGE_INTEGRITY_CODE:
		{
			identification_t *other_id = other_id_payload->get_identification(other_id_payload);
			chunk_t auth_data = auth_payload->get_data(auth_payload);
			chunk_t preshared_secret;
			status_t status;
						
			status = charon->credentials->get_shared_secret(charon->credentials,
															other_id,
															&preshared_secret);
			if (status != SUCCESS)
			{
				this->logger->log(this->logger, ERROR, "no shared secret found for '%s'",
								  other_id->get_string(other_id));
				other_id->destroy(other_id);
				return status;	
			}
			
			chunk_t my_auth_data = this->build_preshared_secret_signature(this,
																		  last_received_packet,
																		  my_nonce,
																		  other_id_payload,
																		  initiator,
																		  preshared_secret);
			chunk_free(&preshared_secret);
			
			if (auth_data.len != my_auth_data.len)
			{
				chunk_free(&my_auth_data);
				status = FAILED;
			}
			else if (memcmp(auth_data.ptr,my_auth_data.ptr, my_auth_data.len) == 0)
			{
				this->logger->log(this->logger, CONTROL, "authentication of '%s' with preshared secret successful",
										other_id->get_string(other_id));
				status = SUCCESS;
			}
			else
			{
				this->logger->log(this->logger, ERROR, "authentication of '%s' with preshared secret failed",
										other_id->get_string(other_id));
				status = FAILED;
			}
			other_id->destroy(other_id);
			chunk_free(&my_auth_data);
			return status;
		}
		case RSA_DIGITAL_SIGNATURE:
		{
			status_t status;
			chunk_t octets;
			chunk_t auth_data = auth_payload->get_data(auth_payload);
			identification_t *other_id = other_id_payload->get_identification(other_id_payload);

			rsa_public_key_t *public_key =
				charon->credentials->get_trusted_public_key(charon->credentials, other_id);

			if (public_key == NULL)
			{
				this->logger->log(this->logger, ERROR, "no public key found for '%s'",
								  other_id->get_string(other_id));
				other_id->destroy(other_id);
				return NOT_FOUND;	
			}
			
			octets = this->allocate_octets(this,last_received_packet, my_nonce,other_id_payload, initiator);
			
			status = public_key->verify_emsa_pkcs1_signature(public_key, octets, auth_data);
			if (status == SUCCESS)
			{
				this->logger->log(this->logger, CONTROL, "authentication of '%s' with RSA successful",
										other_id->get_string(other_id));
			}
			else
			{
				this->logger->log(this->logger, ERROR, "authentication of '%s' with RSA failed",
										other_id->get_string(other_id));
			}
			
			other_id->destroy(other_id);
			chunk_free(&octets);
			return status;
		}
		default:
		{
			return NOT_SUPPORTED;
		}
	}
}

/**
 * Implementation of authenticator_t.compute_auth_data.
 */
static status_t compute_auth_data (private_authenticator_t *this,
									auth_payload_t **auth_payload,
									chunk_t last_sent_packet,
									chunk_t other_nonce,
									id_payload_t *my_id_payload,
									bool initiator)
{
	connection_t *connection = this->ike_sa->get_connection(this->ike_sa);
	
	switch(connection->get_auth_method(connection))
	{
		case SHARED_KEY_MESSAGE_INTEGRITY_CODE:
		{
			identification_t *my_id = my_id_payload->get_identification(my_id_payload);
			chunk_t preshared_secret;
			status_t status;
			chunk_t auth_data;

			status = charon->credentials->get_shared_secret(charon->credentials,
															my_id,
															&preshared_secret);

			if (status != SUCCESS)
			{
				this->logger->log(this->logger, ERROR, "no shared secret found for %s",
								  my_id->get_string(my_id));
				my_id->destroy(my_id);
				return status;	
			}
			my_id->destroy(my_id);
			
			auth_data = this->build_preshared_secret_signature(this, last_sent_packet, other_nonce,
															   my_id_payload, initiator, preshared_secret);
			chunk_free(&preshared_secret);
			*auth_payload = auth_payload_create();
			(*auth_payload)->set_auth_method(*auth_payload, SHARED_KEY_MESSAGE_INTEGRITY_CODE);
			(*auth_payload)->set_data(*auth_payload, auth_data);

			chunk_free(&auth_data);
			return SUCCESS;
		}
		case RSA_DIGITAL_SIGNATURE:
		{
			char buf[BUF_LEN];
			chunk_t octets, auth_data;
			status_t status = NOT_FOUND;
			rsa_public_key_t  *my_pubkey;
			rsa_private_key_t *my_key;

			identification_t  *my_id = my_id_payload->get_identification(my_id_payload);
			
			this->logger->log(this->logger, CONTROL|LEVEL1, "looking for public key belonging to '%s'",
							  my_id->get_string(my_id));

			my_pubkey = charon->credentials->get_rsa_public_key(charon->credentials, my_id);
			if (my_pubkey == NULL)
			{
				this->logger->log(this->logger, ERROR, "no public key found for '%s'",
								  my_id->get_string(my_id));
				goto end_rsa;
			}
			this->logger->log(this->logger, CONTROL|LEVEL2, "matching public key found");
			
			chunk_to_hex(buf, BUF_LEN, my_pubkey->get_keyid(my_pubkey));
			this->logger->log(this->logger, CONTROL|LEVEL1, "looking for private key with keyid %s", buf);

			my_key = charon->credentials->get_rsa_private_key(charon->credentials, my_pubkey);
			if (my_key == NULL)
			{
				char buf[BUF_LEN];

				chunk_to_hex(buf, BUF_LEN, my_pubkey->get_keyid(my_pubkey));
				this->logger->log(this->logger, ERROR, "no private key found with for %s with keyid %s",
								  my_id->get_string(my_id), buf);
				goto end_rsa;
			}
			this->logger->log(this->logger, CONTROL|LEVEL2, "matching private key found");

			octets = this->allocate_octets(this,last_sent_packet,other_nonce,my_id_payload,initiator);
			status = my_key->build_emsa_pkcs1_signature(my_key, HASH_SHA1, octets, &auth_data);
			chunk_free(&octets);

			if (status != SUCCESS)
			{
				my_key->destroy(my_key);
				goto end_rsa;
			}
			
			*auth_payload = auth_payload_create();
			(*auth_payload)->set_auth_method(*auth_payload, RSA_DIGITAL_SIGNATURE);
			(*auth_payload)->set_data(*auth_payload, auth_data);

			my_key->destroy(my_key);
			chunk_free(&auth_data);

		end_rsa:
			my_id->destroy(my_id);
			return status;
		}
		default:
		{
			return NOT_SUPPORTED;
		}
	}
}

/**
 * Implementation of authenticator_t.destroy.
 */
static void destroy (private_authenticator_t *this)
{
	free(this);
}

/*
 * Described in header.
 */
authenticator_t *authenticator_create(ike_sa_t *ike_sa)
{
	private_authenticator_t *this = malloc_thing(private_authenticator_t);

	/* Public functions */
	this->public.destroy = (void(*)(authenticator_t*))destroy;
	this->public.verify_auth_data = (status_t (*) (authenticator_t *,auth_payload_t *, chunk_t ,chunk_t ,id_payload_t *,bool)) verify_auth_data;
	this->public.compute_auth_data = (status_t (*) (authenticator_t *,auth_payload_t **, chunk_t ,chunk_t ,id_payload_t *,bool)) compute_auth_data;
	
	/* private functions */
	this->allocate_octets = allocate_octets;
	this->build_preshared_secret_signature = build_preshared_secret_signature;
	
	/* private data */
	this->ike_sa = ike_sa;
	this->prf = this->ike_sa->get_prf(this->ike_sa);
	this->logger = logger_manager->get_logger(logger_manager, IKE_SA);
	
	return &(this->public);
}