mirror of https://git.matrix.org/git/olm.git
143 lines
4.3 KiB
C
143 lines
4.3 KiB
C
/* Copyright 2015 OpenMarket Ltd
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef OLM_CIPHER_H_
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#define OLM_CIPHER_H_
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#include <stdint.h>
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#include <stdlib.h>
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// Note: exports in this file are only for unit tests. Nobody else should be
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// using this externally
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#include "olm/olm_export.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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struct _olm_cipher;
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struct _olm_cipher_ops {
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/**
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* Returns the length of the message authentication code that will be
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* appended to the output.
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*/
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size_t (*mac_length)(const struct _olm_cipher *cipher);
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/**
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* Returns the length of cipher-text for a given length of plain-text.
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*/
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size_t (*encrypt_ciphertext_length)(
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const struct _olm_cipher *cipher,
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size_t plaintext_length
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);
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/*
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* Encrypts the plain-text into the output buffer and authenticates the
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* contents of the output buffer covering both cipher-text and any other
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* associated data in the output buffer.
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*
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* |---------------------------------------output_length-->|
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* output |--ciphertext_length-->| |---mac_length-->|
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* ciphertext
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*
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* The plain-text pointers and cipher-text pointers may be the same.
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*
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* Returns size_t(-1) if the length of the cipher-text or the output
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* buffer is too small. Otherwise returns the length of the output buffer.
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*/
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size_t (*encrypt)(
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const struct _olm_cipher *cipher,
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uint8_t const * key, size_t key_length,
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uint8_t const * plaintext, size_t plaintext_length,
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uint8_t * ciphertext, size_t ciphertext_length,
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uint8_t * output, size_t output_length
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);
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/**
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* Returns the maximum length of plain-text that a given length of
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* cipher-text can contain.
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*/
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size_t (*decrypt_max_plaintext_length)(
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const struct _olm_cipher *cipher,
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size_t ciphertext_length
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);
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/**
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* Authenticates the input and decrypts the cipher-text into the plain-text
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* buffer.
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*
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* |----------------------------------------input_length-->|
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* input |--ciphertext_length-->| |---mac_length-->|
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* ciphertext
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*
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* The plain-text pointers and cipher-text pointers may be the same.
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*
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* Returns size_t(-1) if the length of the plain-text buffer is too
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* small or if the authentication check fails. Otherwise returns the length
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* of the plain text.
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*/
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size_t (*decrypt)(
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const struct _olm_cipher *cipher,
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uint8_t const * key, size_t key_length,
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uint8_t const * input, size_t input_length,
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uint8_t const * ciphertext, size_t ciphertext_length,
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uint8_t * plaintext, size_t max_plaintext_length
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);
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};
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struct _olm_cipher {
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const struct _olm_cipher_ops *ops;
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/* cipher-specific fields follow */
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};
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struct _olm_cipher_aes_sha_256 {
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struct _olm_cipher base_cipher;
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/** context string for the HKDF used for deriving the AES256 key, HMAC key,
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* and AES IV, from the key material passed to encrypt/decrypt.
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*/
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uint8_t const * kdf_info;
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/** length of context string kdf_info */
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size_t kdf_info_length;
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};
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OLM_EXPORT extern const struct _olm_cipher_ops _olm_cipher_aes_sha_256_ops;
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/**
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* get an initializer for an instance of struct _olm_cipher_aes_sha_256.
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*
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* To use it, declare:
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*
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* struct _olm_cipher_aes_sha_256 MY_CIPHER =
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* OLM_CIPHER_INIT_AES_SHA_256("MY_KDF");
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* struct _olm_cipher *cipher = OLM_CIPHER_BASE(&MY_CIPHER);
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*/
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#define OLM_CIPHER_INIT_AES_SHA_256(KDF_INFO) { \
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/*.base_cipher = */{ &_olm_cipher_aes_sha_256_ops },\
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/*.kdf_info = */(uint8_t *)(KDF_INFO), \
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/*.kdf_info_length = */sizeof(KDF_INFO) - 1 \
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}
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#define OLM_CIPHER_BASE(CIPHER) \
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(&((CIPHER)->base_cipher))
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#ifdef __cplusplus
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} /* extern "C" */
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#endif
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#endif /* OLM_CIPHER_H_ */
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