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f059e57322
- Rearrange class variables to minimize storage padding. - Add protected getters for EspnowMeshBackend and MeshBackendBase components. - Partially update README.md
84 lines
4.2 KiB
C++
84 lines
4.2 KiB
C++
/*
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* Copyright (C) 2019 Anders Löfgren
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*
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* License (MIT license):
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef __MESHCRYPTOINTERFACE_H__
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#define __MESHCRYPTOINTERFACE_H__
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#include <Arduino.h>
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#include <Crypto.h>
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namespace MeshCryptoInterface
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{
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/**
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* There is a constant-time HMAC version available. More constant-time info here: https://www.bearssl.org/constanttime.html
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* For small messages, it takes substantially longer time to complete than a normal HMAC (5 ms vs 2 ms in a quick benchmark,
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* determined by the difference between min and max allowed message length), and it also sets a maximum length that messages can be (1024 bytes by default).
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* Making the fixed max length variable would defeat the whole purpose of using constant-time, and not making it variable would create the wrong HMAC if message size exceeds the maximum.
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*
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* Also, HMAC is already partially constant-time. Quoting the link above:
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* "Hash functions implemented by BearSSL (MD5, SHA-1, SHA-224, SHA-256, SHA-384 and SHA-512) consist in bitwise logical operations and additions on 32-bit or 64-bit words,
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* naturally yielding constant-time operations. HMAC is naturally as constant-time as the underlying hash function. The size of the MACed data, and the size of the key,
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* may leak, though; only the contents are protected."
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*
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* Thus the non constant-time version is used within the mesh framework instead.
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*/
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/**
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* Create a SHA256 HMAC from the message, using the provided hashKey. The result will be hmacLength bytes long and returned as a String in HEX format.
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*
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* @param message The string from which to create the HMAC.
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* @param hashKey The hash key to use when creating the HMAC.
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* @param hashKeyLength The length of the hash key in bytes.
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* @param hmacLength The desired length of the generated HMAC, in bytes. Valid values are 1 to 32. Defaults to experimental::crypto::SHA256::NATURAL_LENGTH.
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*
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* @return A String with the generated HMAC in HEX format.
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*/
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String createMeshHmac(const String &message, const void *hashKey, const size_t hashKeyLength, const size_t hmacLength = experimental::crypto::SHA256::NATURAL_LENGTH);
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/**
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* Verify a SHA256 HMAC which was created from the message using the provided hashKey.
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*
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* @param message The string from which the HMAC was created.
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* @param messageHmac A string with the generated HMAC in HEX format. Valid messageHmac.length() is 2 to 64.
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* @param hashKey The hash key to use when creating the HMAC.
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* @param hashKeyLength The length of the hash key in bytes.
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*
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* @return True if the HMAC is correct. False otherwise.
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*/
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bool verifyMeshHmac(const String &message, const String &messageHmac, const uint8_t *hashKey, const uint8_t hashKeyLength);
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/**
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* Initialize key with a SHA-256 hash of keySeed.
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*
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* @param key A uint8_t array containing the key to be initialized.
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* @param keyLength The length of the key array in bytes. Maximum value is experimental::crypto::SHA256::NATURAL_LENGTH.
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* @param keySeed The key seed.
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*
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* @return A pointer to the initialized key array.
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*/
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uint8_t *initializeKey(uint8_t *key, const uint8_t keyLength, const String &keySeed);
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}
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#endif
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