src/core/crypto/hkdf_sha256.hpp

/*
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/**
 * @file
 *   This file includes definitions for performing HMAC-based Extract-and-Expand Key Derivation Function (HKDF) using
 *   SHA-256.
 */

#ifndef HKDF_SHA256_HPP_
#define HKDF_SHA256_HPP_

#include "openthread-core-config.h"

#include "common/code_utils.hpp"
#include "crypto/context_size.hpp"
#include "crypto/hmac_sha256.hpp"
#include "openthread/platform/crypto.h"

namespace ot {
namespace Crypto {

/**
 * @addtogroup core-security
 *
 * @{
 *
 */

/**
 * This class implements HMAC-based Extract-and-Expand Key Derivation Function (HKDF) [RFC5869] using SHA-256.
 *
 */
class HkdfSha256
{
public:
    /**
     * Constructor to initialize the context.
     *
     */
    HkdfSha256(void);

    /**
     * Destructor to free the context.
     *
     */
    ~HkdfSha256(void);

    /**
     * This method performs the HKDF Extract step.
     *
     * In the Extract step getting an input key extracts from it a pseudo-random key.
     *
     * @param[in] aSalt             A pointer to buffer containing salt.
     * @param[in] aSaltLength       The salt length (in bytes).
     * @param[in] aInputKey         The input key.
     *
     */
    void Extract(const uint8_t *aSalt, uint16_t aSaltLength, const Key &aInputKey);

    /**
     * This method performs the HKDF Expand step.
     *
     * The method should be used after a previous `Extract` call, otherwise its behavior is undefined. In the Expand
     * stage an output key of a given length is derived from the pseudo-random key of Extract stage.
     *
     * @param[in]  aInfo             A pointer to buffer containing info sequence.
     * @param[in]  aInfoLength       The info length (in bytes).
     * @param[out] aOutputKey        Buffer to place the output key (must contain at least @p aOutputKeyLength bytes).
     * @param[in]  aOutputKeyLength  The output key length.
     *
     */
    void Expand(const uint8_t *aInfo, uint16_t aInfoLength, uint8_t *aOutputKey, uint16_t aOutputKeyLength);

private:
    otCryptoContext mContext;
    OT_DEFINE_ALIGNED_VAR(mContextStorage, kHkdfContextSize, uint64_t);
};

/**
 * @}
 *
 */

} // namespace Crypto
} // namespace ot

#endif // HKDF_SHA256_HPP_