hmac.cpp

#include <memory>

#include "hmac.hpp"
#include "util.hpp"

std::shared_ptr<fluks::Hmac_function>
fluks::Hmac_function::create(hash_type type) {
	switch (type) {
	case hash_type::MD5:
		return std::shared_ptr<Hmac_function>(new Hmac_md5);
	case hash_type::RMD160:
		return std::shared_ptr<Hmac_function>(new Hmac_rmd160);
	case hash_type::SHA1:
		return std::shared_ptr<Hmac_function>(new Hmac_sha1);
	case hash_type::SHA224:
		return std::shared_ptr<Hmac_function>(new Hmac_sha224);
	case hash_type::SHA256:
		return std::shared_ptr<Hmac_function>(new Hmac_sha256);
	case hash_type::SHA384:
		return std::shared_ptr<Hmac_function>(new Hmac_sha384);
	case hash_type::SHA512:
		return std::shared_ptr<Hmac_function>(new Hmac_sha512);
	default:
		return std::shared_ptr<Hmac_function>(new Hmac_impl(
		    Hash_function::create(type)));
	}
}

void
fluks::Hmac_impl::init(const uint8_t *key, size_t sz) {
	size_t sz_block = traits()->block_size;
	if (sz > sz_block) {
		// key too long, so
		// K := H(K)
		_hashfn->init();
		_hashfn->add(key, sz);
		_hashfn->end(_key.get());
		sz = traits()->digest_size;
	} else {
		std::copy(key, key + sz, _key.get());
	}

	if (sz < sz_block)
		// (1) fill remainder with zeros
		std::fill(_key.get() + sz, _key.get() + sz_block, 0);

	// (2) XOR result of (1) with ipad
	std::unique_ptr<uint8_t[]> key_ipad{new uint8_t[sz_block]};
	xor_buf_byte(_key.get(), sz_block, IPAD, key_ipad.get());

	// done below as well as successive calls to add():
	// (3) append text to result of (2)
	// (4) apply H to result of (3)

	_hashfn->init();
	_hashfn->add(key_ipad.get(), sz_block);
}

void
fluks::Hmac_impl::end(uint8_t *out) {
	size_t sz_block = traits()->block_size;
	std::unique_ptr<uint8_t[]> key_opad{new uint8_t[sz_block]};
	std::unique_ptr<uint8_t[]> mid_digest{new uint8_t[traits()->digest_size]};

	// (5) XOR result of (1) with opad
	xor_buf_byte(_key.get(), sz_block, OPAD, key_opad.get());

	// (6) append result of (4) to result of (5)
	// (7) apply H to result of (6) and output result

	// get H1 = H( K^ipad . data )
	_hashfn->end(mid_digest.get());
	_hashfn->init();
	_hashfn->add(key_opad.get(), sz_block);
	_hashfn->add(mid_digest.get(), traits()->digest_size);
	// get H( K^opad . H1 )
	_hashfn->end(out);
}