/*  Copyright (C) 2019 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>

    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 3 of the License, or
    (at your option) any later version.

    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.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include <string.h>

#include "contrib/ctype.h"
#include "contrib/strtonum.h"
#include "libdnssec/binary.h"
#include "libdnssec/error.h"
#include "libdnssec/pem.h"
#include "libdnssec/shared/shared.h"
#include "utils/keymgr/bind_privkey.h"

/* -- private key params conversion ---------------------------------------- */

/*!
 * Private key attribute conversion.
 */
typedef struct param_t {
	char *name;
	size_t offset;
	int (*parse_cb)(char *string, void *data);
	void (*free_cb)(void *data);
} param_t;

static int parse_algorithm(char *string, void *_algorithm);
static int parse_binary(char *string, void *_binary);
static int parse_time(char *string, void *_time);

static void binary_free(void *_binary)
{
	dnssec_binary_t *binary = _binary;
	dnssec_binary_free(binary);
}

/*!
 * Know attributes in private key file.
 */
const param_t PRIVKEY_CONVERSION_TABLE[] = {
	#define o(field) offsetof(bind_privkey_t, field)
	{ "Algorithm",       o(algorithm),        parse_algorithm, NULL },
	{ "Modulus",         o(modulus),          parse_binary,    binary_free },
	{ "PublicExponent",  o(public_exponent),  parse_binary,    binary_free },
	{ "PrivateExponent", o(private_exponent), parse_binary,    binary_free },
	{ "Prime1",          o(prime_one),        parse_binary,    binary_free },
	{ "Prime2",          o(prime_two),        parse_binary,    binary_free },
	{ "Exponent1",       o(exponent_one),     parse_binary,    binary_free },
	{ "Exponent2",       o(exponent_two),     parse_binary,    binary_free },
	{ "Coefficient",     o(coefficient),      parse_binary,    binary_free },
	{ "PrivateKey",      o(private_key),      parse_binary,    binary_free },
	{ "Created",         o(time_created),     parse_time,      NULL },
	{ "Publish",         o(time_publish),     parse_time,      NULL },
	{ "Activate",        o(time_activate),    parse_time,      NULL },
	{ "Revoke",          o(time_revoke),      parse_time,      NULL },
	{ "Inactive",        o(time_inactive),    parse_time,      NULL },
	{ "Delete",          o(time_delete),      parse_time,      NULL },
	{ NULL }
	#undef o
};

/* -- attribute parsing ---------------------------------------------------- */

/*!
 * Parse key algorithm field.
 *
 * Example: 7 (NSEC3RSASHA1)
 *
 * Only the numeric value is decoded, the rest of the value is ignored.
 */
static int parse_algorithm(char *string, void *_algorithm)
{
	char *end = string;
	while (*end != '\0' && !is_space(*end)) {
		end += 1;
	}
	*end = '\0';

	uint8_t *algorithm = _algorithm;
	int r = str_to_u8(string, algorithm);

	return (r == KNOT_EOK ? DNSSEC_EOK : DNSSEC_INVALID_KEY_ALGORITHM);
}

/*!
 * Parse binary data encoded in Base64.
 *
 * Example: AQAB
 */
static int parse_binary(char *string, void *_binary)
{
	dnssec_binary_t base64 = {
		.data = (uint8_t *)string,
		.size = strlen(string)
	};

	dnssec_binary_t *binary = _binary;
	return dnssec_binary_from_base64(&base64, binary);
}

#define LEGACY_DATE_FORMAT "%Y%m%d%H%M%S"

/*!
 * Parse timestamp in a format in \ref LEGACY_DATE_FORMAT.
 *
 * Example: 20140415151855
 */
static int parse_time(char *string, void *_time)
{
	struct tm tm = { 0 };

	char *end = strptime(string, LEGACY_DATE_FORMAT, &tm);
	if (end == NULL || *end != '\0') {
		return DNSSEC_MALFORMED_DATA;
	}

	time_t *time = _time;
	*time = timegm(&tm);

	return DNSSEC_EOK;
}

/* -- key parsing ---------------------------------------------------------- */

/*!
 * Strip string value of left and right whitespaces.
 *
 * \param[in,out] value   Start of the string.
 * \param[in,out] length  Length of the string.
 *
 */
static void strip(char **value, size_t *length)
{
	// strip from left
	while (*length > 0 && is_space(**value)) {
		*value += 1;
		*length -= 1;
	}
	// strip from right
	while (*length > 0 && is_space((*value)[*length - 1])) {
		*length -= 1;
	}
}

/*!
 * Parse one line of the private key file.
 */
static int parse_line(bind_privkey_t *params, char *line, size_t length)
{
	assert(params);
	assert(line);

	strip(&line, &length);
	if (length == 0) {
		return KNOT_EOK; // blank line
	}

	char *separator = memchr(line, ':', length);
	if (!separator) {
		return DNSSEC_MALFORMED_DATA;
	}

	char *key = line;
	size_t key_length = separator - key;
	strip(&key, &key_length);

	char *value = separator + 1;
	size_t value_length = (line + length) - value;
	strip(&value, &value_length);

	if (key_length == 0 || value_length == 0) {
		return DNSSEC_MALFORMED_DATA;
	}

	key[key_length] = '\0';
	value[value_length] = '\0';

	for (const param_t *p = PRIVKEY_CONVERSION_TABLE; p->name != NULL; p++) {
		size_t name_length = strlen(p->name);
		if (name_length != key_length) {
			continue;
		}

		if (strcasecmp(p->name, key) != 0) {
			continue;
		}

		return p->parse_cb(value, (void *)params + p->offset);
	}

	// ignore unknown attributes

	return DNSSEC_EOK;
}

int bind_privkey_parse(const char *filename, bind_privkey_t *params_ptr)
{
	_cleanup_fclose_ FILE *file = fopen(filename, "r");
	if (!file) {
		return DNSSEC_NOT_FOUND;
	}

	bind_privkey_t params = *params_ptr;

	_cleanup_free_ char *line = NULL;
	size_t size = 0;
	ssize_t read = 0;
	while ((read = getline(&line, &size, file)) != -1) {
		int r = parse_line(&params, line, read);
		if (r != DNSSEC_EOK) {
			bind_privkey_free(&params);
			return r;
		}
	}

	*params_ptr = params;

	return DNSSEC_EOK;
}

/* -- freeing -------------------------------------------------------------- */

/*!
 * Free private key parameters.
 */
void bind_privkey_free(bind_privkey_t *params)
{
	if (!params) {
		return;
	}

	for (const param_t *p = PRIVKEY_CONVERSION_TABLE; p->name != NULL; p++) {
		if (p->free_cb) {
			p->free_cb((void *)params + p->offset);
		}
	}

	clear_struct(params);
}

/* -- export to PEM -------------------------------------------------------- */

static int rsa_params_to_pem(const bind_privkey_t *params, dnssec_binary_t *pem)
{
	_cleanup_x509_privkey_ gnutls_x509_privkey_t key = NULL;
	int result = gnutls_x509_privkey_init(&key);
	if (result != GNUTLS_E_SUCCESS) {
		return DNSSEC_ENOMEM;
	}

	gnutls_datum_t m = binary_to_datum(&params->modulus);
	gnutls_datum_t e = binary_to_datum(&params->public_exponent);
	gnutls_datum_t d = binary_to_datum(&params->private_exponent);
	gnutls_datum_t p = binary_to_datum(&params->prime_one);
	gnutls_datum_t q = binary_to_datum(&params->prime_two);
	gnutls_datum_t u = binary_to_datum(&params->coefficient);

	result = gnutls_x509_privkey_import_rsa_raw(key, &m, &e, &d, &p, &q, &u);
	if (result != GNUTLS_E_SUCCESS) {
		return DNSSEC_KEY_IMPORT_ERROR;
	}

	return dnssec_pem_from_x509(key, pem);
}

/*!
 * \see lib/key/convert.h
 */
static gnutls_ecc_curve_t choose_ecdsa_curve(size_t pubkey_size)
{
	switch (pubkey_size) {
#ifdef HAVE_ED25519
	case 32: return GNUTLS_ECC_CURVE_ED25519;
#endif
#ifdef HAVE_ED448
	case 57: return GNUTLS_ECC_CURVE_ED448;
#endif
	case 64: return GNUTLS_ECC_CURVE_SECP256R1;
	case 96: return GNUTLS_ECC_CURVE_SECP384R1;
	default: return GNUTLS_ECC_CURVE_INVALID;
	}
}

static void ecdsa_extract_public_params(dnssec_key_t *key, gnutls_ecc_curve_t *curve,
					gnutls_datum_t *x, gnutls_datum_t *y)
{
	dnssec_binary_t pubkey = { 0 };
	dnssec_key_get_pubkey(key, &pubkey);

	*curve = choose_ecdsa_curve(pubkey.size);

	size_t param_size = pubkey.size / 2;
	x->data = pubkey.data;
	x->size = param_size;
	y->data = pubkey.data + param_size;
	y->size = param_size;
}

static int ecdsa_params_to_pem(dnssec_key_t *dnskey, const bind_privkey_t *params,
			       dnssec_binary_t *pem)
{
	_cleanup_x509_privkey_ gnutls_x509_privkey_t key = NULL;
	int result = gnutls_x509_privkey_init(&key);
	if (result != GNUTLS_E_SUCCESS) {
		return DNSSEC_ENOMEM;
	}

	gnutls_ecc_curve_t curve = 0;
	gnutls_datum_t x = { 0 };
	gnutls_datum_t y = { 0 };
	ecdsa_extract_public_params(dnskey, &curve, &x, &y);

	gnutls_datum_t k = binary_to_datum(&params->private_key);

	result = gnutls_x509_privkey_import_ecc_raw(key, curve, &x, &y, &k);
	if (result != DNSSEC_EOK) {
		return DNSSEC_KEY_IMPORT_ERROR;
	}

	gnutls_x509_privkey_fix(key);

	return dnssec_pem_from_x509(key, pem);
}

#if defined(HAVE_ED25519) || defined(HAVE_ED448)
static void eddsa_extract_public_params(dnssec_key_t *key, gnutls_ecc_curve_t *curve,
					gnutls_datum_t *x)
{
	dnssec_binary_t pubkey = { 0 };
	dnssec_key_get_pubkey(key, &pubkey);

	*curve = choose_ecdsa_curve(pubkey.size);

	x->data = pubkey.data;
	x->size = pubkey.size;
}

static int eddsa_params_to_pem(dnssec_key_t *dnskey, const bind_privkey_t *params,
			       dnssec_binary_t *pem)
{
	_cleanup_x509_privkey_ gnutls_x509_privkey_t key = NULL;
	int result = gnutls_x509_privkey_init(&key);
	if (result != GNUTLS_E_SUCCESS) {
		return DNSSEC_ENOMEM;
	}

	gnutls_ecc_curve_t curve = 0;
	gnutls_datum_t x = { 0 };
	eddsa_extract_public_params(dnskey, &curve, &x);

	gnutls_datum_t k = binary_to_datum(&params->private_key);

	result = gnutls_x509_privkey_import_ecc_raw(key, curve, &x, NULL, &k);
	if (result != DNSSEC_EOK) {
		return DNSSEC_KEY_IMPORT_ERROR;
	}

	gnutls_x509_privkey_fix(key);

	return dnssec_pem_from_x509(key, pem);
}
#endif

int bind_privkey_to_pem(dnssec_key_t *key, bind_privkey_t *params, dnssec_binary_t *pem)
{
	dnssec_key_algorithm_t algorithm = dnssec_key_get_algorithm(key);
	switch (algorithm) {
	case DNSSEC_KEY_ALGORITHM_RSA_SHA1:
	case DNSSEC_KEY_ALGORITHM_RSA_SHA1_NSEC3:
	case DNSSEC_KEY_ALGORITHM_RSA_SHA256:
	case DNSSEC_KEY_ALGORITHM_RSA_SHA512:
		return rsa_params_to_pem(params, pem);
	case DNSSEC_KEY_ALGORITHM_ECDSA_P256_SHA256:
	case DNSSEC_KEY_ALGORITHM_ECDSA_P384_SHA384:
		return ecdsa_params_to_pem(key, params, pem);
#ifdef HAVE_ED25519
	case DNSSEC_KEY_ALGORITHM_ED25519:
#endif
#ifdef HAVE_ED448
	case DNSSEC_KEY_ALGORITHM_ED448:
#endif
#if defined(HAVE_ED25519) || defined(HAVE_ED448)
		return eddsa_params_to_pem(key, params, pem);
#endif
	default:
		return DNSSEC_INVALID_KEY_ALGORITHM;
	}
}

void bind_privkey_to_timing(bind_privkey_t *params, knot_kasp_key_timing_t *timing)
{
	// timing->created remains "now"
	timing->publish = (knot_time_t)params->time_publish;
	timing->ready   = 0;
	timing->active  = (knot_time_t)params->time_activate;
	timing->retire  = (knot_time_t)params->time_inactive;
	timing->revoke  = (knot_time_t)params->time_revoke;
	timing->remove  = (knot_time_t)params->time_delete;
}