HmacContext.h

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/****
 * Sming Framework Project - Open Source framework for high efficiency native ESP8266 development.
 * Created 2015 by Skurydin Alexey
 * http://github.com/SmingHub/Sming
 * All files of the Sming Core are provided under the LGPL v3 license.
 *
 * HmacContext.h
 *
 ****/

#pragma once

#include "HashContext.h"
#include <cstring>
#include <cassert>

namespace Crypto
{
template <class HashContext> class HmacContext
{
public:
    using Engine = typename HashContext::Engine;
    using Hash = typename HashContext::Hash;
    static constexpr size_t blocksize = Engine::blocksize;

    HmacContext() = default;

    HmacContext(const Secret& key)
    {
        init(key);
    }

    HmacContext& init(const Secret& key)
    {
        ByteArray<blocksize> inputPad{};
        if(key.size() <= blocksize) {
            memcpy(inputPad.data(), key.data(), key.size());
        } else {
            ctx.reset();
            ctx.update(key);
            auto hash = ctx.getHash();
            memcpy(inputPad.data(), hash.data(), hash.size());
        }

        outputPad = inputPad;

        for(auto& c : inputPad) {
            c ^= 0x36;
        }
        for(auto& c : outputPad) {
            c ^= 0x5c;
        }

        ctx.reset();
        ctx.update(inputPad);

        return *this;
    }

    template <typename... Ts> HmacContext& update(Ts&&... args)
    {
        ctx.update(std::forward<Ts>(args)...);
        return *this;
    }

    Hash getHash()
    {
        auto tmp = ctx.getHash();

        ctx.reset();
        ctx.update(outputPad);
        ctx.update(tmp);
        return ctx.getHash();
    }

    template <typename... Ts> Hash calculate(Ts&&... args)
    {
        ctx.update(std::forward<Ts>(args)...);
        return getHash();
    }

private:
    ByteArray<blocksize> outputPad;
    HashContext ctx;
};

/*
 * HMAC definitions
 */

using HmacMd5 = HmacContext<Md5>;
using HmacSha1 = HmacContext<Sha1>;
using HmacSha224 = HmacContext<Sha224>;
using HmacSha256 = HmacContext<Sha256>;
using HmacSha384 = HmacContext<Sha384>;
using HmacSha512 = HmacContext<Sha512>;

} // namespace Crypto