/*-
 * Copyright 2016 Vsevolod Stakhov
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#ifndef DKIM_H_
#define DKIM_H_

#include "config.h"
#include "contrib/libev/ev.h"
#include "dns.h"
#include "ref.h"
#include <stdbool.h>
#include <stdint.h>


/* Main types and definitions */

#define RSPAMD_DKIM_SIGNHEADER "DKIM-Signature"
#define RSPAMD_DKIM_ARC_SIGNHEADER "ARC-Message-Signature"
#define RSPAMD_DKIM_ARC_AUTHHEADER "ARC-Authentication-Results"
#define RSPAMD_DKIM_ARC_SEALHEADER "ARC-Seal"
/* DKIM signature header */


/* Errors (from OpenDKIM) */

#define DKIM_SIGERROR_UNKNOWN (-1)       /* unknown error */
#define DKIM_SIGERROR_VERSION 1          /* unsupported version */
#define DKIM_SIGERROR_EXPIRED 3          /* signature expired */
#define DKIM_SIGERROR_FUTURE 4           /* signature in the future */
#define DKIM_SIGERROR_NOREC 6            /* No record */
#define DKIM_SIGERROR_INVALID_HC 7       /* c= invalid (header) */
#define DKIM_SIGERROR_INVALID_BC 8       /* c= invalid (body) */
#define DKIM_SIGERROR_INVALID_A 10       /* a= invalid */
#define DKIM_SIGERROR_INVALID_L 12       /* l= invalid */
#define DKIM_SIGERROR_EMPTY_D 16         /* d= empty */
#define DKIM_SIGERROR_EMPTY_S 18         /* s= empty */
#define DKIM_SIGERROR_EMPTY_B 20         /* b= empty */
#define DKIM_SIGERROR_NOKEY 22           /* no key found in DNS */
#define DKIM_SIGERROR_KEYFAIL 24         /* DNS query failed */
#define DKIM_SIGERROR_EMPTY_BH 26        /* bh= empty */
#define DKIM_SIGERROR_BADSIG 28          /* signature mismatch */
#define DKIM_SIGERROR_EMPTY_H 31         /* h= empty */
#define DKIM_SIGERROR_INVALID_H 32       /* h= missing req'd entries */
#define DKIM_SIGERROR_KEYHASHMISMATCH 37 /* sig-key hash mismatch */
#define DKIM_SIGERROR_EMPTY_V 45         /* v= tag empty */
#define DKIM_SIGERROR_KEYTYPE 46         /* unknown key type */
#define DKIM_SIGERROR_REVOKED 47         /* key revoked (no p= tag) */

#ifdef __cplusplus
extern "C" {
#endif

/* Check results */
enum rspamd_dkim_check_rcode {
	DKIM_CONTINUE = 0,
	DKIM_REJECT,
	DKIM_TRYAGAIN,
	DKIM_NOTFOUND,
	DKIM_RECORD_ERROR,
	DKIM_PERM_ERROR,
};

#define DKIM_CANON_SIMPLE 0  /* as specified in DKIM spec */
#define DKIM_CANON_RELAXED 1 /* as specified in DKIM spec */

struct rspamd_dkim_context_s;
typedef struct rspamd_dkim_context_s rspamd_dkim_context_t;

struct rspamd_dkim_sign_context_s;
typedef struct rspamd_dkim_sign_context_s rspamd_dkim_sign_context_t;

struct rspamd_dkim_key_s;
typedef struct rspamd_dkim_key_s rspamd_dkim_key_t;
typedef struct rspamd_dkim_key_s rspamd_dkim_sign_key_t;

struct rspamd_task;

enum rspamd_dkim_key_format {
	RSPAMD_DKIM_KEY_FILE = 0,
	RSPAMD_DKIM_KEY_PEM,
	RSPAMD_DKIM_KEY_BASE64,
	RSPAMD_DKIM_KEY_RAW,
	RSPAMD_DKIM_KEY_UNKNOWN
};

enum rspamd_dkim_type {
	RSPAMD_DKIM_NORMAL,
	RSPAMD_DKIM_ARC_SIG,
	RSPAMD_DKIM_ARC_SEAL
};

/* Signature methods */
enum rspamd_sign_type {
	DKIM_SIGN_UNKNOWN = -2,
	DKIM_SIGN_RSASHA1 = 0,
	DKIM_SIGN_RSASHA256,
	DKIM_SIGN_RSASHA512,
	DKIM_SIGN_ECDSASHA256,
	DKIM_SIGN_ECDSASHA512,
	DKIM_SIGN_EDDSASHA256,
};

enum rspamd_dkim_key_type {
	RSPAMD_DKIM_KEY_INVALID = -1,
	RSPAMD_DKIM_KEY_RSA = 0,
	RSPAMD_DKIM_KEY_ECDSA,
	RSPAMD_DKIM_KEY_EDDSA
};

struct rspamd_dkim_check_result {
	enum rspamd_dkim_check_rcode rcode;
	rspamd_dkim_context_t *ctx;
	/* Processed parts */
	const char *selector;
	const char *domain;
	const char *short_b;
	const char *fail_reason;
};


/* Err MUST be freed if it is not NULL, key is allocated by slice allocator */
typedef void (*dkim_key_handler_f)(rspamd_dkim_key_t *key, size_t keylen,
								   rspamd_dkim_context_t *ctx, gpointer ud, GError *err);

/**
 * Create new dkim context from signature
 * @param sig message's signature
 * @param pool pool to allocate memory from
 * @param time_jitter jitter in seconds to allow time diff while checking
 * @param err pointer to error object
 * @return new context or NULL
 */
rspamd_dkim_context_t *rspamd_create_dkim_context(const char *sig,
												  rspamd_mempool_t *pool,
												  struct rspamd_dns_resolver *resolver,
												  unsigned int time_jitter,
												  enum rspamd_dkim_type type,
												  GError **err);

/**
 * Create new dkim context for making a signature
 * @param task
 * @param priv_key
 * @param err
 * @return
 */
rspamd_dkim_sign_context_t *rspamd_create_dkim_sign_context(struct rspamd_task *task,
															rspamd_dkim_sign_key_t *priv_key,
															int headers_canon,
															int body_canon,
															const char *dkim_headers,
															enum rspamd_dkim_type type,
															GError **err);

/**
 * Load dkim key
 * @param path
 * @param err
 * @return
 */
rspamd_dkim_sign_key_t *rspamd_dkim_sign_key_load(const char *what, size_t len,
												  enum rspamd_dkim_key_format type,
												  GError **err);

/**
 * Invalidate modified sign key
 * @param key
 * @return
*/
bool rspamd_dkim_sign_key_maybe_invalidate(rspamd_dkim_sign_key_t *key,
										   time_t mtime);

/**
 * Make DNS request for specified context and obtain and parse key
 * @param ctx dkim context from signature
 * @param resolver dns resolver object
 * @param s async session to make request
 * @return
 */
bool rspamd_get_dkim_key(rspamd_dkim_context_t *ctx,
						 struct rspamd_task *task,
						 dkim_key_handler_f handler,
						 gpointer ud);

/**
 * Check task for dkim context using dkim key
 * @param ctx dkim verify context
 * @param key dkim key (from cache or from dns request)
 * @param task task to check
 * @return
 */
struct rspamd_dkim_check_result *rspamd_dkim_check(rspamd_dkim_context_t *ctx,
												   rspamd_dkim_key_t *key,
												   struct rspamd_task *task);

struct rspamd_dkim_check_result *
rspamd_dkim_create_result(rspamd_dkim_context_t *ctx,
						  enum rspamd_dkim_check_rcode rcode,
						  struct rspamd_task *task);

GString *rspamd_dkim_sign(struct rspamd_task *task,
						  const char *selector,
						  const char *domain,
						  time_t expire,
						  size_t len,
						  unsigned int idx,
						  const char *arc_cv,
						  rspamd_dkim_sign_context_t *ctx);

rspamd_dkim_key_t *rspamd_dkim_key_ref(rspamd_dkim_key_t *k);

void rspamd_dkim_key_unref(rspamd_dkim_key_t *k);

rspamd_dkim_sign_key_t *rspamd_dkim_sign_key_ref(rspamd_dkim_sign_key_t *k);

void rspamd_dkim_sign_key_unref(rspamd_dkim_sign_key_t *k);

/**
 * Get the type of a signing key
 * @param key signing key
 * @return key type (RSA, EDDSA, etc)
 */
enum rspamd_dkim_key_type rspamd_dkim_sign_key_get_type(rspamd_dkim_sign_key_t *key);

/**
 * Sign a digest with a DKIM signing key
 * @param key signing key
 * @param digest SHA256 digest (32 bytes)
 * @param dlen digest length (must be 32)
 * @param sig_out output signature buffer (base64 encoded), must be freed by caller
 * @param err error pointer
 * @return TRUE if successful
 */
gboolean rspamd_dkim_sign_digest(rspamd_dkim_sign_key_t *key,
								 const unsigned char *digest, gsize dlen,
								 char **sig_out, GError **err);

const char *rspamd_dkim_get_domain(rspamd_dkim_context_t *ctx);

const char *rspamd_dkim_get_selector(rspamd_dkim_context_t *ctx);

const char *rspamd_dkim_get_dns_key(rspamd_dkim_context_t *ctx);

unsigned int rspamd_dkim_key_get_ttl(rspamd_dkim_key_t *k);

/**
 * Create DKIM public key from a raw data
 * @param keydata
 * @param keylen
 * @param type
 * @param err
 * @return
 */
rspamd_dkim_key_t *rspamd_dkim_make_key(const char *keydata, unsigned int keylen,
										enum rspamd_dkim_key_type type,
										GError **err);

#define RSPAMD_DKIM_KEY_ID_LEN 16
/**
 * Returns key id for dkim key (raw md5 of RSPAMD_DKIM_KEY_ID_LEN)
 * NOT ZERO TERMINATED, use RSPAMD_DKIM_KEY_ID_LEN for length
 * @param key
 * @return
 */
const unsigned char *rspamd_dkim_key_id(rspamd_dkim_key_t *key);

/**
 * Parse DKIM public key from a TXT record
 * @param txt
 * @param keylen
 * @param err
 * @return
 */
rspamd_dkim_key_t *rspamd_dkim_parse_key(const char *txt, size_t *keylen,
										 GError **err);

/**
 * Canonicalise header using relaxed algorithm
 * @param hname
 * @param hvalue
 * @param out
 * @param outlen
 * @return
 */
off_t rspamd_dkim_canonize_header_relaxed_str(const char *hname,
											  const char *hvalue,
											  char *out,
											  size_t outlen);

/**
 * Checks public and private keys for match
 * @param pk
 * @param sk
 * @param err
 * @return
 */
bool rspamd_dkim_match_keys(rspamd_dkim_key_t *pk,
							rspamd_dkim_sign_key_t *sk,
							GError **err);

/**
 * Free DKIM key
 * @param key
 */
void rspamd_dkim_key_free(rspamd_dkim_key_t *key);

#ifdef __cplusplus
}
#endif

#endif /* DKIM_H_ */
