#ifndef DCRYPT_H
#define DCRYPT_H 1

struct dcrypt_context_symmetric;
struct dcrypt_context_hmac;
struct dcrypt_public_key;
struct dcrypt_private_key;

struct dcrypt_keypair {
	struct dcrypt_public_key *pub;
	struct dcrypt_private_key *priv;
};

enum dcrypt_sym_mode {
	DCRYPT_MODE_ENCRYPT,
	DCRYPT_MODE_DECRYPT
};

enum dcrypt_key_type {
	DCRYPT_KEY_RSA = 0x1,
	DCRYPT_KEY_EC  = 0x2
};

/**
 * dovecot key format:
 * version version-specific data
 * v1: version tab nid tab raw ec private key (in hex)
 * v2: version colon algorithm oid colon private-or-public-key-only (in hex)
 */
enum dcrypt_key_format {
	DCRYPT_FORMAT_PEM,
	DCRYPT_FORMAT_DOVECOT,
};

enum dcrypt_key_encryption_type {
	DCRYPT_KEY_ENCRYPTION_TYPE_NONE,
	DCRYPT_KEY_ENCRYPTION_TYPE_KEY,
	DCRYPT_KEY_ENCRYPTION_TYPE_PASSWORD
};

enum dcrypt_key_version {
	DCRYPT_KEY_VERSION_1,
	DCRYPT_KEY_VERSION_2,
	DCRYPT_KEY_VERSION_NA /* not applicable, PEM key */
};

enum dcrypt_key_kind {
	DCRYPT_KEY_KIND_PUBLIC,
	DCRYPT_KEY_KIND_PRIVATE
};

struct dcrypt_settings {
	/* OpenSSL engine to use */
	const char *crypto_device;
	/* Look for backends in this directory */
	const char *module_dir;
};

/**
 * load and initialize dcrypt backend, use either openssl or gnutls
 */
bool dcrypt_initialize(const char *backend, const struct dcrypt_settings *set, const char **error_r);

/**
 * deinitialize dcrypt
 */
void dcrypt_deinitialize(void);

/**
 * create symmetric context
 */
bool dcrypt_ctx_sym_create(const char *algorithm, enum dcrypt_sym_mode mode, struct dcrypt_context_symmetric **ctx_r, const char **error_r);

/**
 * destroy symmetric context and free memory
 */
void dcrypt_ctx_sym_destroy(struct dcrypt_context_symmetric **ctx);

/**
 * key and IV manipulation functions
 */
void dcrypt_ctx_sym_set_key(struct dcrypt_context_symmetric *ctx, const unsigned char *key, size_t key_len);
void dcrypt_ctx_sym_set_iv(struct dcrypt_context_symmetric *ctx, const unsigned char *iv, size_t iv_len);
void dcrypt_ctx_sym_set_key_iv_random(struct dcrypt_context_symmetric *ctx);
bool dcrypt_ctx_sym_get_key(struct dcrypt_context_symmetric *ctx, buffer_t *key);
bool dcrypt_ctx_sym_get_iv(struct dcrypt_context_symmetric *ctx, buffer_t *iv);

/**
 * turn padding on/off (default: on)
 */
void dcrypt_ctx_sym_set_padding(struct dcrypt_context_symmetric *ctx, bool padding);


/**
 * authentication data manipulation (use with GCM only)
 */
void dcrypt_ctx_sym_set_aad(struct dcrypt_context_symmetric *ctx, const unsigned char *aad, size_t aad_len);
bool dcrypt_ctx_sym_get_aad(struct dcrypt_context_symmetric *ctx, buffer_t *aad);
/**
 * result tag from aead (use with GCM only)
 */
void dcrypt_ctx_sym_set_tag(struct dcrypt_context_symmetric *ctx, const unsigned char *tag, size_t tag_len);
bool dcrypt_ctx_sym_get_tag(struct dcrypt_context_symmetric *ctx, buffer_t *tag);

/* get various lengths */
unsigned int dcrypt_ctx_sym_get_key_length(struct dcrypt_context_symmetric *ctx);
unsigned int dcrypt_ctx_sym_get_iv_length(struct dcrypt_context_symmetric *ctx);
unsigned int dcrypt_ctx_sym_get_block_size(struct dcrypt_context_symmetric *ctx);

/**
 * initialize crypto
 */
bool dcrypt_ctx_sym_init(struct dcrypt_context_symmetric *ctx, const char **error_r);
/**
 * update with data
 */
bool dcrypt_ctx_sym_update(struct dcrypt_context_symmetric *ctx, const unsigned char *data, size_t data_len, buffer_t *result, const char **error_r);
/**
 * perform final step (may or may not emit data)
 */
bool dcrypt_ctx_sym_final(struct dcrypt_context_symmetric *ctx, buffer_t *result, const char **error_r);

/**
 * create HMAC context, algorithm is digest algorithm
 */
bool dcrypt_ctx_hmac_create(const char *algorithm, struct dcrypt_context_hmac **ctx_r, const char **error_r);
/**
 * destroy HMAC context and free memory
 */
void dcrypt_ctx_hmac_destroy(struct dcrypt_context_hmac **ctx);

/**
 * hmac key manipulation
 */
void dcrypt_ctx_hmac_set_key(struct dcrypt_context_hmac *ctx, const unsigned char *key, size_t key_len);
bool dcrypt_ctx_hmac_get_key(struct dcrypt_context_hmac *ctx, buffer_t *key);
void dcrypt_ctx_hmac_set_key_random(struct dcrypt_context_hmac *ctx);

/**
 * get digest length for HMAC
 */
unsigned int dcrypt_ctx_hmac_get_digest_length(struct dcrypt_context_hmac *ctx);

/**
 * initialize hmac
 */
bool dcrypt_ctx_hmac_init(struct dcrypt_context_hmac *ctx, const char **error_r);
/**
 * update hmac context with data
 */
bool dcrypt_ctx_hmac_update(struct dcrypt_context_hmac *ctx, const unsigned char *data, size_t data_len, const char **error_r);
/**
 * perform final rounds and retrieve result
 */
bool dcrypt_ctx_hmac_final(struct dcrypt_context_hmac *ctx, buffer_t *result, const char **error_r);


/**
 * Elliptic Curve based Diffie-Heffman shared secret derivation */
bool dcrypt_ecdh_derive_secret_local(struct dcrypt_private_key *local_key, buffer_t *R, buffer_t *S, const char **error_r);
bool dcrypt_ecdh_derive_secret_peer(struct dcrypt_public_key *peer_key, buffer_t *R, buffer_t *S, const char **error_r);

/**
 * generate cryptographic data from password and salt. Use 1000-10000 for rounds.
 */
bool dcrypt_pbkdf2(const unsigned char *password, size_t password_len, const unsigned char *salt, size_t salt_len,
	const char *hash, unsigned int rounds, buffer_t *result, unsigned int result_len, const char **error_r);

bool dcrypt_keypair_generate(struct dcrypt_keypair *pair_r, enum dcrypt_key_type kind, unsigned int bits, const char *curve, const char **error_r);

/**
 * load loads key structure from external format. 
 * store stores key structure into external format.
 *
 * you can provide either PASSWORD or ENC_KEY, not both.
 */
bool dcrypt_key_load_private(struct dcrypt_private_key **key_r, const char *data,
	const char *password, struct dcrypt_private_key *dec_key, const char **error_r);

bool dcrypt_key_load_public(struct dcrypt_public_key **key_r, const char *data,
	const char **error_r);

/**
 * When encrypting with public key, the cipher parameter here must begin with
 * ecdh-, for example ecdh-aes-256-ctr. An example of a valid cipher for
 * encrypting with password would be aes-256-ctr.
 */
bool dcrypt_key_store_private(struct dcrypt_private_key *key, enum dcrypt_key_format format, const char *cipher, 
	buffer_t *destination, const char *password, struct dcrypt_public_key *enc_key, const char **error_r);

bool dcrypt_key_store_public(struct dcrypt_public_key *key, enum dcrypt_key_format format, buffer_t *destination, const char **error_r);

void dcrypt_key_convert_private_to_public(struct dcrypt_private_key *priv_key, struct dcrypt_public_key **pub_key_r);

void dcrypt_keypair_unref(struct dcrypt_keypair *keypair);
void dcrypt_key_ref_public(struct dcrypt_public_key *key);
void dcrypt_key_ref_private(struct dcrypt_private_key *key);
void dcrypt_key_unref_public(struct dcrypt_public_key **key);
void dcrypt_key_unref_private(struct dcrypt_private_key **key);

enum dcrypt_key_type dcrypt_key_type_private(struct dcrypt_private_key *key);
enum dcrypt_key_type dcrypt_key_type_public(struct dcrypt_public_key *key);
bool dcrypt_key_id_public(struct dcrypt_public_key *key, const char *algorithm, buffer_t *result, const char **error_r); /* return digest of key */
bool dcrypt_key_id_public_old(struct dcrypt_public_key *key, buffer_t *result, const char **error_r); /* return SHA1 sum of key */
bool dcrypt_key_id_private(struct dcrypt_private_key *key, const char *algorithm, buffer_t *result, const char **error_r); /* return digest of key */
bool dcrypt_key_id_private_old(struct dcrypt_private_key *key, buffer_t *result, const char **error_r); /* return SHA1 sum of key */

bool dcrypt_key_string_get_info(const char *key_data, enum dcrypt_key_format *format_r, enum dcrypt_key_version *version_r,
	enum dcrypt_key_kind *kind_r, enum dcrypt_key_encryption_type *encryption_type_r, const char **encryption_key_hash_r,
	const char **key_hash_r, const char **error_r);

/* RSA stuff */
bool dcrypt_rsa_encrypt(struct dcrypt_public_key *key, const unsigned char *data, size_t data_len, buffer_t *result, const char **error_r);
bool dcrypt_rsa_decrypt(struct dcrypt_private_key *key, const unsigned char *data, size_t data_len, buffer_t *result, const char **error_r);

/* OID stuff */
const char *dcrypt_oid2name(const unsigned char *oid, size_t oid_len, const char **error_r);
bool dcrypt_name2oid(const char *name, buffer_t *oid, const char **error_r);

#endif