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#ifndef SESSION_CIPHER_H
#define SESSION_CIPHER_H
#include <stdint.h>
#include <stddef.h>
#include "signal_protocol_types.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* The main entry point for Signal Protocol encrypt/decrypt operations.
*
* Once a session has been established with session_builder,
* this class can be used for all encrypt/decrypt operations within
* that session.
*/
/**
* Construct a session cipher for encrypt/decrypt operations on a session.
* In order to use session_cipher, a session must have already been created
* and stored using session_builder.
*
* The store and global contexts must remain valid for the lifetime of the
* session cipher.
*
* When finished, free the returned instance by calling session_cipher_free().
*
* @param cipher set to a freshly allocated session cipher instance
* @param store the signal_protocol_store_context to store all state information in
* @param remote_address the remote address that messages will be encrypted to or decrypted from.
* @param global_context the global library context
* @return 0 on success, or negative on failure
*/
int session_cipher_create(session_cipher **cipher,
signal_protocol_store_context *store, const signal_protocol_address *remote_address,
signal_context *global_context);
/**
* Set the optional user data pointer for the session cipher.
*
* This is to give callback functions a way of accessing app specific
* context information for this cipher.
*/
void session_cipher_set_user_data(session_cipher *cipher, void *user_data);
/**
* Get the optional user data pointer for the session cipher.
*
* This is to give callback functions a way of accessing app specific
* context information for this cipher.
*/
void *session_cipher_get_user_data(session_cipher *cipher);
/**
* Set the callback function that is called during the decrypt process.
*
* The callback function is called from within
* session_cipher_decrypt_pre_key_signal_message() and
* session_cipher_decrypt_signal_message() after decryption is complete
* but before the updated session state has been committed to the session
* store. If the callback function returns a negative value, then the
* decrypt function will immediately fail with an error.
*
* This a callback allows some implementations to store the committed plaintext
* to their local message store first, in case they are concerned with a crash
* or write error happening between the time the session state is updated but
* before they're able to successfully store the plaintext to disk.
*
* @param callback the callback function to set
*/
void session_cipher_set_decryption_callback(session_cipher *cipher,
int (*callback)(session_cipher *cipher, signal_buffer *plaintext, void *decrypt_context));
/**
* Encrypt a message.
*
* @param padded_message The plaintext message bytes, optionally padded to a constant multiple.
* @param padded_message_len The length of the data pointed to by padded_message
* @param encrypted_message Set to a ciphertext message encrypted to the recipient+device tuple.
*
* @return SG_SUCCESS on success, negative on error
*/
int session_cipher_encrypt(session_cipher *cipher,
const uint8_t *padded_message, size_t padded_message_len,
ciphertext_message **encrypted_message);
/**
* Decrypt a message.
*
* @param ciphertext The pre_key_signal_message to decrypt.
* @param decrypt_context Optional context pointer associated with the
* ciphertext, which is passed to the decryption callback function
* @param plaintext Set to a newly allocated buffer containing the plaintext.
*
* @retval SG_SUCCESS Success
* @retval SG_ERR_INVALID_MESSAGE if the input is not valid ciphertext.
* @retval SG_ERR_DUPLICATE_MESSAGE if the input is a message that has already been received.
* @retval SG_ERR_LEGACY_MESSAGE if the input is a message formatted by a protocol version that
* is no longer supported.
* @retval SG_ERR_INVALID_KEY_ID when there is no local pre_key_record
* that corresponds to the pre key ID in the message.
* @retval SG_ERR_INVALID_KEY when the message is formatted incorrectly.
* @retval SG_ERR_UNTRUSTED_IDENTITY when the identity key of the sender is untrusted.
*/
int session_cipher_decrypt_pre_key_signal_message(session_cipher *cipher,
pre_key_signal_message *ciphertext, void *decrypt_context,
signal_buffer **plaintext);
/**
* Decrypt a message.
*
* @param ciphertext The signal_message to decrypt.
* @param decrypt_context Optional context pointer associated with the
* ciphertext, which is passed to the decryption callback function
* @param plaintext Set to a newly allocated buffer containing the plaintext.
*
* @retval SG_SUCCESS Success
* @retval SG_ERR_INVALID_MESSAGE if the input is not valid ciphertext.
* @retval SG_ERR_DUPLICATE_MESSAGE if the input is a message that has already been received.
* @retval SG_ERR_LEGACY_MESSAGE if the input is a message formatted by a protocol version that
* is no longer supported.
* @retval SG_ERR_NO_SESSION if there is no established session for this contact.
*/
int session_cipher_decrypt_signal_message(session_cipher *cipher,
signal_message *ciphertext, void *decrypt_context,
signal_buffer **plaintext);
/**
* Gets the remote registration ID for this session cipher.
*
* @param remote_id Set to the value of the remote registration ID
*
* @return SG_SUCCESS on success, negative on error
*/
int session_cipher_get_remote_registration_id(session_cipher *cipher, uint32_t *remote_id);
/**
* Gets the version of the session associated with this session cipher.
*
* @param version Set to the value of the session version
*
* @retval SG_SUCCESS Success
* @retval SG_ERR_NO_SESSION if no session could be found
*/
int session_cipher_get_session_version(session_cipher *cipher, uint32_t *version);
void session_cipher_free(session_cipher *cipher);
#ifdef __cplusplus
}
#endif
#endif /* SESSION_CIPHER_H */
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