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/*
* KDF defined in NIST SP 800-56a revision 2 (Single-step key-derivation function)
* or in NIST SP 800-56C revision 2 (Section 4 - One-Step KDM)
*
* (C) 2017 Ribose Inc. Written by Krzysztof Kwiatkowski.
* (C) 2024 Fabian Albert - Rohde & Schwarz Cybersecurity
* (C) 2024 René Meusel - Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/sp800_56c_one_step.h>
#include <botan/exceptn.h>
#include <botan/mem_ops.h>
#include <botan/internal/bit_ops.h>
#include <botan/internal/fmt.h>
#include <botan/internal/kmac.h>
#include <functional>
namespace Botan {
namespace {
template <typename T>
concept hash_or_mac_type = std::is_same_v<T, HashFunction> || std::is_same_v<T, MessageAuthenticationCode>;
/**
* @brief One-Step Key Derivation as defined in SP800-56Cr2 Section 4
*/
template <hash_or_mac_type HashOrMacType>
void kdm_internal(std::span<uint8_t> output_buffer,
std::span<const uint8_t> z,
std::span<const uint8_t> fixed_info,
HashOrMacType& hash_or_mac,
const std::function<void(HashOrMacType&)>& init_h_callback) {
size_t l = output_buffer.size() * 8;
// 1. If L > 0, then set reps = ceil(L / H_outputBits); otherwise,
// output an error indicator and exit this process without
// performing the remaining actions (i.e., omit steps 2 through 8).
BOTAN_ARG_CHECK(l > 0, "Zero KDM output length");
size_t reps = ceil_division(l, hash_or_mac.output_length() * 8);
// 2. If reps > (2^32 − 1), then output an error indicator and exit this
// process without performing the remaining actions
// (i.e., omit steps 3 through 8).
BOTAN_ARG_CHECK(reps <= 0xFFFFFFFF, "Too large KDM output length");
// 3. Initialize a big-endian 4-byte unsigned integer counter as
// 0x00000000, corresponding to a 32-bit binary representation of
// the number zero.
uint32_t counter = 0;
// 4. If counter || Z || FixedInfo is more than max_H_inputBits bits
// long, then output an error indicator and exit this process
// without performing any of the remaining actions (i.e., omit
// steps 5 through 8). => SHA3 and KMAC are unlimited
// 5. Initialize Result(0) as an empty bit string
// (i.e., the null string).
secure_vector<uint8_t> result;
// 6. For i = 1 to reps, do the following:
for(size_t i = 1; i <= reps; i++) {
// 6.1. Increment counter by 1.
counter++;
// Reset the hash/MAC object. For MAC, also set the key (salt) and IV.
hash_or_mac.clear();
init_h_callback(hash_or_mac);
// 6.2 Compute K(i) = H(counter || Z || FixedInfo).
hash_or_mac.update_be(counter);
hash_or_mac.update(z);
hash_or_mac.update(fixed_info);
auto k_i = hash_or_mac.final();
// 6.3. Set Result(i) = Result(i−1) || K(i).
result.insert(result.end(), k_i.begin(), k_i.end());
}
// 7. Set DerivedKeyingMaterial equal to the leftmost L bits of Result(reps).
copy_mem(output_buffer, std::span(result).subspan(0, output_buffer.size()));
}
} // namespace
void SP800_56C_One_Step_Hash::perform_kdf(std::span<uint8_t> key,
std::span<const uint8_t> secret,
std::span<const uint8_t> salt,
std::span<const uint8_t> label) const {
BOTAN_ARG_CHECK(salt.empty(), "SP800_56A_Hash does not support a non-empty salt");
kdm_internal<HashFunction>(key, secret, label, *m_hash, [](HashFunction&) { /* NOP */ });
}
std::string SP800_56C_One_Step_Hash::name() const {
return fmt("SP800-56A({})", m_hash->name());
}
std::unique_ptr<KDF> SP800_56C_One_Step_Hash::new_object() const {
return std::make_unique<SP800_56C_One_Step_Hash>(m_hash->new_object());
}
SP800_56C_One_Step_HMAC::SP800_56C_One_Step_HMAC(std::unique_ptr<MessageAuthenticationCode> mac) :
m_mac(std::move(mac)) {
// TODO: we need a MessageAuthenticationCode::is_hmac
if(!m_mac->name().starts_with("HMAC(")) {
throw Algorithm_Not_Found("Only HMAC can be used with SP800_56A_HMAC");
}
}
void SP800_56C_One_Step_HMAC::perform_kdf(std::span<uint8_t> key,
std::span<const uint8_t> secret,
std::span<const uint8_t> salt,
std::span<const uint8_t> label) const {
kdm_internal<MessageAuthenticationCode>(key, secret, label, *m_mac, [&](MessageAuthenticationCode& kdf_mac) {
// 4.1 Option 2 and 3 - An implementation dependent byte string, salt,
// whose (non-null) value may be optionally provided in
// OtherInput, serves as the HMAC# key ..
// SP 800-56Cr2 specifies if the salt is empty then a block of zeros
// equal to the hash's underlying block size are used. However for HMAC
// this is equivalent to setting a zero-length key, so the same call
// works for either case.
kdf_mac.set_key(salt);
});
}
std::string SP800_56C_One_Step_HMAC::name() const {
return fmt("SP800-56A({})", m_mac->name());
}
std::unique_ptr<KDF> SP800_56C_One_Step_HMAC::new_object() const {
return std::make_unique<SP800_56C_One_Step_HMAC>(m_mac->new_object());
}
// Option 3 - KMAC
void SP800_56A_One_Step_KMAC_Abstract::perform_kdf(std::span<uint8_t> key,
std::span<const uint8_t> secret,
std::span<const uint8_t> salt,
std::span<const uint8_t> label) const {
auto mac = create_kmac_instance(key.size());
kdm_internal<MessageAuthenticationCode>(key, secret, label, *mac, [&](MessageAuthenticationCode& kdf_mac) {
// 4.1 Option 2 and 3 - An implementation dependent byte string, salt,
// whose (non-null) value may be optionally provided in
// OtherInput, serves as the KMAC# key ...
if(salt.empty()) {
// 4.1 Implementation-Dependent Parameters 3
// If H(x) = KMAC128[or 256](salt, x, H_outputBits, "KDF"),
// then – in the absence of an agreed-upon alternative –
// the default_salt shall be an all - zero string of
// 164 bytes [or 132 bytes]
kdf_mac.set_key(std::vector<uint8_t>(default_salt_length(), 0));
} else {
kdf_mac.set_key(salt);
}
// 4.1 Option 3 - The "customization string" S shall be the byte string
// 01001011 || 01000100 || 01000110, which represents the sequence
// of characters 'K', 'D', and 'F' in 8-bit ASCII.
kdf_mac.start(std::array<uint8_t, 3>{'K', 'D', 'F'});
});
}
std::unique_ptr<MessageAuthenticationCode> SP800_56C_One_Step_KMAC128::create_kmac_instance(
size_t output_byte_len) const {
return std::make_unique<KMAC128>(output_byte_len * 8);
}
std::unique_ptr<MessageAuthenticationCode> SP800_56C_One_Step_KMAC256::create_kmac_instance(
size_t output_byte_len) const {
return std::make_unique<KMAC256>(output_byte_len * 8);
}
} // namespace Botan