HKDF.h

/*
 * Copyright (C) 2022 Southern Storm Software, Pty Ltd.
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 *
 * The above copyright notice and this permission notice shall be included
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 */
 
#ifndef CRYPTO_HKDF_h
#define CRYPTO_HKDF_h
 
#include "Hash.h"
#include "Crypto.h"
 
class HKDFCommon
{
public:
    virtual ~HKDFCommon();
 
    void setKey(const void *key, size_t keyLen, const void *salt = 0, size_t saltLen = 0);
 
    void extract(void *out, size_t outLen, const void *info = 0, size_t infoLen = 0);
 
    void clear();
 
protected:
    HKDFCommon();
    void setHashAlgorithm(Hash *hashAlg, uint8_t *buffer)
    {
        hash = hashAlg;
        buf = buffer;
    }
 
private:
    Hash *hash;
    uint8_t *buf;
    uint8_t counter;
    uint8_t posn;
};
 
template <typename T>
class HKDF : public HKDFCommon
{
public:
    HKDF() { setHashAlgorithm(&hashAlg, buffer); }
    ~HKDF() { ::clean(buffer, sizeof(buffer)); }
 
private:
    T hashAlg;
    uint8_t buffer[T::HASH_SIZE * 2];
};
 
template <typename T> void hkdf
    (void *out, size_t outLen, const void *key, size_t keyLen,
     const void *salt, size_t saltLen, const void *info, size_t infoLen)
{
    HKDF<T> context;
    context.setKey(key, keyLen, salt, saltLen);
    context.extract(out, outLen, info, infoLen);
}
 
#endif