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/* Copyright 2015 OpenMarket Ltd
*
* 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 OLM_CIPHER_H_
#define OLM_CIPHER_H_
#include <stdint.h>
#include <stdlib.h>
#ifdef __cplusplus
extern "C" {
#endif
struct _olm_cipher;
struct _olm_cipher_ops {
/**
* Returns the length of the message authentication code that will be
* appended to the output.
*/
size_t (*mac_length)(const struct _olm_cipher *cipher);
/**
* Returns the length of cipher-text for a given length of plain-text.
*/
size_t (*encrypt_ciphertext_length)(
const struct _olm_cipher *cipher,
size_t plaintext_length
);
/*
* Encrypts the plain-text into the output buffer and authenticates the
* contents of the output buffer covering both cipher-text and any other
* associated data in the output buffer.
*
* |---------------------------------------output_length-->|
* output |--ciphertext_length-->| |---mac_length-->|
* ciphertext
*
* The plain-text pointers and cipher-text pointers may be the same.
*
* Returns size_t(-1) if the length of the cipher-text or the output
* buffer is too small. Otherwise returns the length of the output buffer.
*/
size_t (*encrypt)(
const struct _olm_cipher *cipher,
uint8_t const * key, size_t key_length,
uint8_t const * plaintext, size_t plaintext_length,
uint8_t * ciphertext, size_t ciphertext_length,
uint8_t * output, size_t output_length
);
/**
* Returns the maximum length of plain-text that a given length of
* cipher-text can contain.
*/
size_t (*decrypt_max_plaintext_length)(
const struct _olm_cipher *cipher,
size_t ciphertext_length
);
/**
* Authenticates the input and decrypts the cipher-text into the plain-text
* buffer.
*
* |----------------------------------------input_length-->|
* input |--ciphertext_length-->| |---mac_length-->|
* ciphertext
*
* The plain-text pointers and cipher-text pointers may be the same.
*
* Returns size_t(-1) if the length of the plain-text buffer is too
* small or if the authentication check fails. Otherwise returns the length
* of the plain text.
*/
size_t (*decrypt)(
const struct _olm_cipher *cipher,
uint8_t const * key, size_t key_length,
uint8_t const * input, size_t input_length,
uint8_t const * ciphertext, size_t ciphertext_length,
uint8_t * plaintext, size_t max_plaintext_length
);
};
struct _olm_cipher {
const struct _olm_cipher_ops *ops;
/* cipher-specific fields follow */
};
struct _olm_cipher_aes_sha_256 {
struct _olm_cipher base_cipher;
/** context string for the HKDF used for deriving the AES256 key, HMAC key,
* and AES IV, from the key material passed to encrypt/decrypt.
*/
uint8_t const * kdf_info;
/** length of context string kdf_info */
size_t kdf_info_length;
};
extern const struct _olm_cipher_ops _olm_cipher_aes_sha_256_ops;
/**
* get an initializer for an instance of struct _olm_cipher_aes_sha_256.
*
* To use it, declare:
*
* struct _olm_cipher_aes_sha_256 MY_CIPHER =
* OLM_CIPHER_INIT_AES_SHA_256("MY_KDF");
* struct _olm_cipher *cipher = OLM_CIPHER_BASE(&MY_CIPHER);
*/
#define OLM_CIPHER_INIT_AES_SHA_256(KDF_INFO) { \
/*.base_cipher = */{ &_olm_cipher_aes_sha_256_ops },\
/*.kdf_info = */(uint8_t *)(KDF_INFO), \
/*.kdf_info_length = */sizeof(KDF_INFO) - 1 \
}
#define OLM_CIPHER_BASE(CIPHER) \
(&((CIPHER)->base_cipher))
#ifdef __cplusplus
} /* extern "C" */
#endif
#endif /* OLM_CIPHER_H_ */
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