/*
 * Copyright (C) 2009 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 "pgp_cert.h"
#include "pgp_utils.h"

#include <time.h>

#include <utils/debug.h>

typedef struct private_pgp_cert_t private_pgp_cert_t;

/**
 * Private data of an pgp_cert_t object.
 */
struct private_pgp_cert_t {

	/**
	 * Implements pgp_cert_t interface.
	 */
	pgp_cert_t public;

	/**
	 * Public key of the certificate
	 */
	public_key_t *key;

	/**
	 * version of the public key
	 */
	uint32_t version;

	/**
	 * creation time
	 */
	uint32_t created;

	/**
	 * days the certificate is valid
	 */
	uint32_t valid;

	/**
	 * userid of the certificate
	 */
	identification_t *user_id;

	/**
	 * v3 or v4 fingerprint of the PGP public key
	 */
	chunk_t fingerprint;

	/**
	 * full PGP encoding
	 */
	chunk_t encoding;

	/**
	 * reference counter
	 */
	refcount_t ref;
};


METHOD(certificate_t, get_type, certificate_type_t,
	private_pgp_cert_t *this)
{
	return CERT_GPG;
}

METHOD(certificate_t, get_subject,identification_t*,
	private_pgp_cert_t *this)
{
	return this->user_id;
}

METHOD(certificate_t, get_issuer, identification_t*,
	private_pgp_cert_t *this)
{
	return this->user_id;
}

METHOD(certificate_t, has_subject, id_match_t,
	private_pgp_cert_t *this, identification_t *subject)
{
	id_match_t match_user_id;

	match_user_id = this->user_id->matches(this->user_id, subject);
	if (match_user_id == ID_MATCH_NONE &&
		subject->get_type(subject) == ID_KEY_ID &&
        chunk_equals(this->fingerprint, subject->get_encoding(subject)))
	{
		return ID_MATCH_PERFECT;
	}
	return match_user_id;
}

METHOD(certificate_t, has_issuer, id_match_t,
	private_pgp_cert_t *this, identification_t *issuer)
{
	return ID_MATCH_NONE;
}

METHOD(certificate_t, issued_by,bool,
	private_pgp_cert_t *this, certificate_t *issuer, signature_scheme_t *scheme)
{
	/* TODO: check signature blobs for a valid signature */
	return FALSE;
}

METHOD(certificate_t, get_public_key, public_key_t*,
	private_pgp_cert_t *this)
{
	this->key->get_ref(this->key);
	return this->key;
}

METHOD(certificate_t, get_ref, certificate_t*,
	private_pgp_cert_t *this)
{
	ref_get(&this->ref);
	return &this->public.interface.interface;
}

METHOD(certificate_t, get_validity, bool,
	private_pgp_cert_t *this, time_t *when, time_t *not_before,
	time_t *not_after)
{
	time_t t, until;

	if (when)
	{
		t = *when;
	}
	else
	{
		t = time(NULL);
	}
	if (not_before)
	{
		*not_before = this->created;
	}
	if (this->valid)
	{
		until = this->valid + this->created * 24 * 60 * 60;
	}
	else
	{
		/* Jan 19 03:14:07 UTC 2038 */
		until = TIME_32_BIT_SIGNED_MAX;
	}
	if (not_after)
	{
		*not_after = until;
	}
	return (t >= this->valid && t <= until);
}

METHOD(certificate_t, get_encoding, bool,
	private_pgp_cert_t *this, cred_encoding_type_t type, chunk_t *encoding)
{
	if (type == CERT_PGP_PKT)
	{
		*encoding = chunk_clone(this->encoding);
		return TRUE;
	}
	return lib->encoding->encode(lib->encoding, type, NULL, encoding,
						CRED_PART_PGP_CERT, this->encoding, CRED_PART_END);
}

METHOD(certificate_t, equals, bool,
	private_pgp_cert_t *this, certificate_t *other)
{
	chunk_t encoding;
	bool equal;

	if (this == (private_pgp_cert_t*)other)
	{
		return TRUE;
	}
	if (other->get_type(other) != CERT_X509)
	{
		return FALSE;
	}
	if (other->equals == (void*)equals)
	{	/* skip allocation if we have the same implementation */
		return chunk_equals(this->encoding, ((private_pgp_cert_t*)other)->encoding);
	}
	if (!other->get_encoding(other, CERT_PGP_PKT, &encoding))
	{
		return FALSE;
	}
	equal = chunk_equals(this->encoding, encoding);
	free(encoding.ptr);
	return equal;
}

METHOD(certificate_t, destroy, void,
	private_pgp_cert_t *this)
{
	if (ref_put(&this->ref))
	{
		DESTROY_IF(this->key);
		DESTROY_IF(this->user_id);
		free(this->fingerprint.ptr);
		free(this->encoding.ptr);
		free(this);
	}
}

METHOD(pgp_certificate_t, get_fingerprint, chunk_t,
	private_pgp_cert_t *this)
{
	return this->fingerprint;
}

/**
 * See header
 */
private_pgp_cert_t *create_empty()
{
	private_pgp_cert_t *this;

	INIT(this,
		.public = {
			.interface = {
				.interface = {
					.get_type = _get_type,
					.get_subject = _get_subject,
					.get_issuer = _get_issuer,
					.has_subject = _has_subject,
					.has_issuer = _has_issuer,
					.issued_by = _issued_by,
					.get_public_key = _get_public_key,
					.get_validity = _get_validity,
					.get_encoding = _get_encoding,
					.equals = _equals,
					.get_ref = _get_ref,
					.destroy = _destroy,
				},
				.get_fingerprint = _get_fingerprint,
			},
		},
		.ref = 1,
	);

	return this;
}

/**
 * Parse the public key packet of a PGP certificate
 */
static bool parse_public_key(private_pgp_cert_t *this, chunk_t packet)
{
	chunk_t pubkey_packet = packet;

	if (!pgp_read_scalar(&packet, 1, &this->version))
	{
		return FALSE;
	}
	switch (this->version)
	{
		case 3:
			if (!pgp_read_scalar(&packet, 4, &this->created) ||
				!pgp_read_scalar(&packet, 2, &this->valid))
			{
				return FALSE;
			}
			break;
		case 4:
			if (!pgp_read_scalar(&packet, 4, &this->created))
			{
				return FALSE;
			}
			break;
		default:
			DBG1(DBG_ASN, "PGP packet version V%d not supported",
				 this->version);
			return FALSE;
	}
	if (this->valid)
	{
		DBG2(DBG_ASN, "L2 - created %T, valid %d days", &this->created, FALSE,
			 this->valid);
	}
	else
	{
		DBG2(DBG_ASN, "L2 - created %T, never expires", &this->created, FALSE);
	}
	DESTROY_IF(this->key);
	this->key = lib->creds->create(lib->creds, CRED_PUBLIC_KEY, KEY_ANY,
									BUILD_BLOB_PGP, packet, BUILD_END);
	if (this->key == NULL)
	{
		return FALSE;
	}

	/* compute V4 or V3 fingerprint according to section 12.2 of RFC 4880 */
	if (this->version == 4)
	{
		chunk_t pubkey_packet_header = chunk_from_chars(
					0x99, pubkey_packet.len / 256, pubkey_packet.len % 256
				);
		hasher_t *hasher;

		hasher = lib->crypto->create_hasher(lib->crypto, HASH_SHA1);
		if (hasher == NULL)
		{
			DBG1(DBG_ASN, "no SHA-1 hasher available");
			return FALSE;
		}
		if (!hasher->allocate_hash(hasher, pubkey_packet_header, NULL) ||
			!hasher->allocate_hash(hasher, pubkey_packet, &this->fingerprint))
		{
			hasher->destroy(hasher);
			return FALSE;
		}
		hasher->destroy(hasher);
		DBG2(DBG_ASN, "L2 - v4 fingerprint %#B", &this->fingerprint);
	}
	else
	{
		/* V3 fingerprint is computed by public_key_t class */
		if (!this->key->get_fingerprint(this->key, KEYID_PGPV3,
										&this->fingerprint))
		{
			return FALSE;
		}
		this->fingerprint = chunk_clone(this->fingerprint);
		DBG2(DBG_ASN, "L2 - v3 fingerprint %#B", &this->fingerprint);
	}
	return TRUE;
}

/**
 * Parse the signature packet of a PGP certificate
 */
static bool parse_signature(private_pgp_cert_t *this, chunk_t packet)
{
	uint32_t version, len, type, created;

	if (!pgp_read_scalar(&packet, 1, &version))
	{
		return FALSE;
	}

	/* we parse only v3 or v4 signature packets */
	if (version != 3 && version != 4)
	{
		DBG2(DBG_ASN, "L2 - v%d signature ignored", version);
		return TRUE;
	}
	if (version == 4)
	{
		if (!pgp_read_scalar(&packet, 1, &type))
		{
			return FALSE;
		}
		DBG2(DBG_ASN, "L2 - v%d signature of type 0x%02x", version, type);
	}
	else
	{
		if (!pgp_read_scalar(&packet, 1, &len) || len != 5)
		{
			return FALSE;
		}
		if (!pgp_read_scalar(&packet, 1, &type) ||
			!pgp_read_scalar(&packet, 4, &created))
		{
			return FALSE;
		}
		DBG2(DBG_ASN, "L2 - v3 signature of type 0x%02x, created %T", type,
			 &created, FALSE);
	}
	/* TODO: parse and save signature to a list */
	return TRUE;
}

/**
 * Parse the userid packet of a PGP certificate
 */
static bool parse_user_id(private_pgp_cert_t *this, chunk_t packet)
{
	DESTROY_IF(this->user_id);
	this->user_id = identification_create_from_encoding(ID_KEY_ID, packet);
	DBG2(DBG_ASN, "L2 - '%Y'", this->user_id);
	return TRUE;
}

/**
 * See header.
 */
pgp_cert_t *pgp_cert_load(certificate_type_t type, va_list args)
{
	chunk_t packet, blob = chunk_empty;
	pgp_packet_tag_t tag;
	private_pgp_cert_t *this;

	while (TRUE)
	{
		switch (va_arg(args, builder_part_t))
		{
			case BUILD_BLOB_PGP:
				blob = va_arg(args, chunk_t);
				continue;
			case BUILD_END:
				break;
			default:
				return NULL;
		}
		break;
	}

	this = create_empty();
	this->encoding = chunk_clone(blob);
	while (blob.len)
	{
		if (!pgp_read_packet(&blob, &packet, &tag))
		{
			destroy(this);
			return NULL;
		}
		switch (tag)
		{
			case PGP_PKT_PUBLIC_KEY:
				if (!parse_public_key(this, packet))
				{
					destroy(this);
					return NULL;
				}
				break;
			case PGP_PKT_SIGNATURE:
				if (!parse_signature(this, packet))
				{
					destroy(this);
					return NULL;
				}
				break;
			case PGP_PKT_USER_ID:
				if (!parse_user_id(this, packet))
				{
					destroy(this);
					return NULL;
				}
				break;
			default:
				DBG1(DBG_LIB, "ignoring %N packet in PGP certificate",
					 pgp_packet_tag_names, tag);
				break;
		}
	}
	if (this->key)
	{
		return &this->public;
	}
	destroy(this);
	return NULL;
}