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/*
* GCM GHASH
* (C) 2013,2015,2017 Jack Lloyd
* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/ghash.h>
#include <botan/internal/ct_utils.h>
#include <botan/internal/loadstor.h>
#include <botan/internal/cpuid.h>
#include <botan/exceptn.h>
namespace Botan {
std::string GHASH::provider() const
{
#if defined(BOTAN_HAS_GHASH_CLMUL_CPU)
if(CPUID::has_carryless_multiply())
return "clmul";
#endif
#if defined(BOTAN_HAS_GHASH_CLMUL_VPERM)
if(CPUID::has_vperm())
return "vperm";
#endif
return "base";
}
void GHASH::ghash_multiply(secure_vector<uint8_t>& x,
const uint8_t input[],
size_t blocks)
{
#if defined(BOTAN_HAS_GHASH_CLMUL_CPU)
if(CPUID::has_carryless_multiply())
{
return ghash_multiply_cpu(x.data(), m_H_pow.data(), input, blocks);
}
#endif
#if defined(BOTAN_HAS_GHASH_CLMUL_VPERM)
if(CPUID::has_vperm())
{
return ghash_multiply_vperm(x.data(), m_HM.data(), input, blocks);
}
#endif
CT::poison(x.data(), x.size());
const uint64_t ALL_BITS = 0xFFFFFFFFFFFFFFFF;
uint64_t X[2] = {
load_be<uint64_t>(x.data(), 0),
load_be<uint64_t>(x.data(), 1)
};
for(size_t b = 0; b != blocks; ++b)
{
X[0] ^= load_be<uint64_t>(input, 2*b);
X[1] ^= load_be<uint64_t>(input, 2*b+1);
uint64_t Z[2] = { 0, 0 };
for(size_t i = 0; i != 64; ++i)
{
const uint64_t X0MASK = (ALL_BITS + (X[0] >> 63)) ^ ALL_BITS;
const uint64_t X1MASK = (ALL_BITS + (X[1] >> 63)) ^ ALL_BITS;
X[0] <<= 1;
X[1] <<= 1;
Z[0] ^= m_HM[4*i ] & X0MASK;
Z[1] ^= m_HM[4*i+1] & X0MASK;
Z[0] ^= m_HM[4*i+2] & X1MASK;
Z[1] ^= m_HM[4*i+3] & X1MASK;
}
X[0] = Z[0];
X[1] = Z[1];
}
store_be<uint64_t>(x.data(), X[0], X[1]);
CT::unpoison(x.data(), x.size());
}
void GHASH::ghash_update(secure_vector<uint8_t>& ghash,
const uint8_t input[], size_t length)
{
verify_key_set(!m_HM.empty());
/*
This assumes if less than block size input then we're just on the
final block and should pad with zeros
*/
const size_t full_blocks = length / GCM_BS;
const size_t final_bytes = length - (full_blocks * GCM_BS);
if(full_blocks > 0)
{
ghash_multiply(ghash, input, full_blocks);
}
if(final_bytes)
{
uint8_t last_block[GCM_BS] = { 0 };
copy_mem(last_block, input + full_blocks * GCM_BS, final_bytes);
ghash_multiply(ghash, last_block, 1);
secure_scrub_memory(last_block, final_bytes);
}
}
void GHASH::key_schedule(const uint8_t key[], size_t length)
{
m_H.assign(key, key+length);
m_H_ad.resize(GCM_BS);
m_ad_len = 0;
m_text_len = 0;
uint64_t H0 = load_be<uint64_t>(m_H.data(), 0);
uint64_t H1 = load_be<uint64_t>(m_H.data(), 1);
const uint64_t R = 0xE100000000000000;
m_HM.resize(256);
// precompute the multiples of H
for(size_t i = 0; i != 2; ++i)
{
for(size_t j = 0; j != 64; ++j)
{
/*
we interleave H^1, H^65, H^2, H^66, H3, H67, H4, H68
to make indexing nicer in the multiplication code
*/
m_HM[4*j+2*i] = H0;
m_HM[4*j+2*i+1] = H1;
// GCM's bit ops are reversed so we carry out of the bottom
const uint64_t carry = R * (H1 & 1);
H1 = (H1 >> 1) | (H0 << 63);
H0 = (H0 >> 1) ^ carry;
}
}
#if defined(BOTAN_HAS_GHASH_CLMUL_CPU)
if(CPUID::has_carryless_multiply())
{
m_H_pow.resize(8);
ghash_precompute_cpu(m_H.data(), m_H_pow.data());
}
#endif
}
void GHASH::start(const uint8_t nonce[], size_t len)
{
BOTAN_ARG_CHECK(len == 16, "GHASH requires a 128-bit nonce");
m_nonce.assign(nonce, nonce + len);
m_ghash = m_H_ad;
}
void GHASH::set_associated_data(const uint8_t input[], size_t length)
{
if(m_ghash.empty() == false)
throw Invalid_State("Too late to set AD in GHASH");
zeroise(m_H_ad);
ghash_update(m_H_ad, input, length);
m_ad_len = length;
}
void GHASH::update_associated_data(const uint8_t ad[], size_t length)
{
verify_key_set(m_ghash.size() == GCM_BS);
m_ad_len += length;
ghash_update(m_ghash, ad, length);
}
void GHASH::update(const uint8_t input[], size_t length)
{
verify_key_set(m_ghash.size() == GCM_BS);
m_text_len += length;
ghash_update(m_ghash, input, length);
}
void GHASH::add_final_block(secure_vector<uint8_t>& hash,
size_t ad_len, size_t text_len)
{
/*
* stack buffer is fine here since the text len is public
* and the length of the AD is probably not sensitive either.
*/
uint8_t final_block[GCM_BS];
store_be<uint64_t>(final_block, 8*ad_len, 8*text_len);
ghash_update(hash, final_block, GCM_BS);
}
void GHASH::final(uint8_t mac[], size_t mac_len)
{
BOTAN_ARG_CHECK(mac_len > 0 && mac_len <= 16, "GHASH output length");
add_final_block(m_ghash, m_ad_len, m_text_len);
for(size_t i = 0; i != mac_len; ++i)
mac[i] = m_ghash[i] ^ m_nonce[i];
m_ghash.clear();
m_text_len = 0;
}
void GHASH::nonce_hash(secure_vector<uint8_t>& y0, const uint8_t nonce[], size_t nonce_len)
{
BOTAN_ASSERT(m_ghash.size() == 0, "nonce_hash called during wrong time");
ghash_update(y0, nonce, nonce_len);
add_final_block(y0, 0, nonce_len);
}
void GHASH::clear()
{
zap(m_H);
zap(m_HM);
reset();
}
void GHASH::reset()
{
zeroise(m_H_ad);
m_ghash.clear();
m_nonce.clear();
m_text_len = m_ad_len = 0;
}
}
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