1 /*
2  *  Copyright (c) 2020, The OpenThread Authors.
3  *  All rights reserved.
4  *
5  *  Redistribution and use in source and binary forms, with or without
6  *  modification, are permitted provided that the following conditions are met:
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8  *     notice, this list of conditions and the following disclaimer.
9  *  2. Redistributions in binary form must reproduce the above copyright
10  *     notice, this list of conditions and the following disclaimer in the
11  *     documentation and/or other materials provided with the distribution.
12  *  3. Neither the name of the copyright holder nor the
13  *     names of its contributors may be used to endorse or promote products
14  *     derived from this software without specific prior written permission.
15  *
16  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
17  *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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27  */
28 
29 /**
30  * @file
31  *   This file includes definitions for performing HMAC-based Extract-and-Expand Key Derivation Function (HKDF) using
32  *   SHA-256.
33  */
34 
35 #ifndef HKDF_SHA256_HPP_
36 #define HKDF_SHA256_HPP_
37 
38 #include "openthread-core-config.h"
39 
40 #include "common/code_utils.hpp"
41 #include "crypto/context_size.hpp"
42 #include "crypto/hmac_sha256.hpp"
43 #include "openthread/platform/crypto.h"
44 
45 namespace ot {
46 namespace Crypto {
47 
48 /**
49  * @addtogroup core-security
50  *
51  * @{
52  *
53  */
54 
55 /**
56  * Implements HMAC-based Extract-and-Expand Key Derivation Function (HKDF) [RFC5869] using SHA-256.
57  *
58  */
59 class HkdfSha256
60 {
61 public:
62     /**
63      * Constructor to initialize the context.
64      *
65      */
66     HkdfSha256(void);
67 
68     /**
69      * Destructor to free the context.
70      *
71      */
72     ~HkdfSha256(void);
73 
74     /**
75      * Performs the HKDF Extract step.
76      *
77      * In the Extract step getting an input key extracts from it a pseudo-random key.
78      *
79      * @param[in] aSalt             A pointer to buffer containing salt.
80      * @param[in] aSaltLength       The salt length (in bytes).
81      * @param[in] aInputKey         The input key.
82      *
83      */
84     void Extract(const uint8_t *aSalt, uint16_t aSaltLength, const Key &aInputKey);
85 
86     /**
87      * Performs the HKDF Expand step.
88      *
89      * The method should be used after a previous `Extract` call, otherwise its behavior is undefined. In the Expand
90      * stage an output key of a given length is derived from the pseudo-random key of Extract stage.
91      *
92      * @param[in]  aInfo             A pointer to buffer containing info sequence.
93      * @param[in]  aInfoLength       The info length (in bytes).
94      * @param[out] aOutputKey        Buffer to place the output key (must contain at least @p aOutputKeyLength bytes).
95      * @param[in]  aOutputKeyLength  The output key length.
96      *
97      */
98     void Expand(const uint8_t *aInfo, uint16_t aInfoLength, uint8_t *aOutputKey, uint16_t aOutputKeyLength);
99 
100 private:
101     otCryptoContext mContext;
102     OT_DEFINE_ALIGNED_VAR(mContextStorage, kHkdfContextSize, uint64_t);
103 };
104 
105 /**
106  * @}
107  *
108  */
109 
110 } // namespace Crypto
111 } // namespace ot
112 
113 #endif // HKDF_SHA256_HPP_
114