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/*
* PSSR
* (C) 1999-2007,2017 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/pssr.h>
#include <botan/mgf1.h>
#include <botan/internal/bit_ops.h>
namespace Botan {
namespace {
/*
* PSSR Encode Operation
*/
secure_vector<uint8_t> pss_encode(HashFunction& hash,
const secure_vector<uint8_t>& msg,
const secure_vector<uint8_t>& salt,
size_t output_bits)
{
const size_t HASH_SIZE = hash.output_length();
const size_t SALT_SIZE = salt.size();
if(msg.size() != HASH_SIZE)
throw Encoding_Error("Cannot encode PSS string, input length invalid for hash");
if(output_bits < 8*HASH_SIZE + 8*SALT_SIZE + 9)
throw Encoding_Error("Cannot encode PSS string, output length too small");
const size_t output_length = (output_bits + 7) / 8;
for(size_t i = 0; i != 8; ++i)
hash.update(0);
hash.update(msg);
hash.update(salt);
secure_vector<uint8_t> H = hash.final();
secure_vector<uint8_t> EM(output_length);
EM[output_length - HASH_SIZE - SALT_SIZE - 2] = 0x01;
buffer_insert(EM, output_length - 1 - HASH_SIZE - SALT_SIZE, salt);
mgf1_mask(hash, H.data(), HASH_SIZE, EM.data(), output_length - HASH_SIZE - 1);
EM[0] &= 0xFF >> (8 * ((output_bits + 7) / 8) - output_bits);
buffer_insert(EM, output_length - 1 - HASH_SIZE, H);
EM[output_length-1] = 0xBC;
return EM;
}
bool pss_verify(HashFunction& hash,
const secure_vector<uint8_t>& const_coded,
const secure_vector<uint8_t>& raw,
size_t key_bits)
{
const size_t HASH_SIZE = hash.output_length();
const size_t KEY_BYTES = (key_bits + 7) / 8;
if(key_bits < 8*HASH_SIZE + 9)
return false;
if(raw.size() != HASH_SIZE)
return false;
if(const_coded.size() > KEY_BYTES || const_coded.size() <= 1)
return false;
if(const_coded[const_coded.size()-1] != 0xBC)
return false;
secure_vector<uint8_t> coded = const_coded;
if(coded.size() < KEY_BYTES)
{
secure_vector<uint8_t> temp(KEY_BYTES);
buffer_insert(temp, KEY_BYTES - coded.size(), coded);
coded = temp;
}
const size_t TOP_BITS = 8 * ((key_bits + 7) / 8) - key_bits;
if(TOP_BITS > 8 - high_bit(coded[0]))
return false;
uint8_t* DB = coded.data();
const size_t DB_size = coded.size() - HASH_SIZE - 1;
const uint8_t* H = &coded[DB_size];
const size_t H_size = HASH_SIZE;
mgf1_mask(hash, H, H_size, DB, DB_size);
DB[0] &= 0xFF >> TOP_BITS;
size_t salt_offset = 0;
for(size_t j = 0; j != DB_size; ++j)
{
if(DB[j] == 0x01)
{ salt_offset = j + 1; break; }
if(DB[j])
return false;
}
if(salt_offset == 0)
return false;
const size_t salt_size = DB_size - salt_offset;
for(size_t j = 0; j != 8; ++j)
hash.update(0);
hash.update(raw);
hash.update(&DB[salt_offset], salt_size);
secure_vector<uint8_t> H2 = hash.final();
return same_mem(H, H2.data(), HASH_SIZE);
}
}
PSSR::PSSR(HashFunction* h) :
m_hash(h), m_SALT_SIZE(m_hash->output_length())
{
}
PSSR::PSSR(HashFunction* h, size_t salt_size) :
m_hash(h), m_SALT_SIZE(salt_size)
{
}
/*
* PSSR Update Operation
*/
void PSSR::update(const uint8_t input[], size_t length)
{
m_hash->update(input, length);
}
/*
* Return the raw (unencoded) data
*/
secure_vector<uint8_t> PSSR::raw_data()
{
return m_hash->final();
}
secure_vector<uint8_t> PSSR::encoding_of(const secure_vector<uint8_t>& msg,
size_t output_bits,
RandomNumberGenerator& rng)
{
secure_vector<uint8_t> salt = rng.random_vec(m_SALT_SIZE);
return pss_encode(*m_hash, msg, salt, output_bits);
}
/*
* PSSR Decode/Verify Operation
*/
bool PSSR::verify(const secure_vector<uint8_t>& coded,
const secure_vector<uint8_t>& raw,
size_t key_bits)
{
return pss_verify(*m_hash, coded, raw, key_bits);
}
PSSR_Raw::PSSR_Raw(HashFunction* h) :
m_hash(h), m_SALT_SIZE(m_hash->output_length())
{
}
PSSR_Raw::PSSR_Raw(HashFunction* h, size_t salt_size) :
m_hash(h), m_SALT_SIZE(salt_size)
{
}
/*
* PSSR_Raw Update Operation
*/
void PSSR_Raw::update(const uint8_t input[], size_t length)
{
m_msg.insert(m_msg.end(), input, input + length);
}
/*
* Return the raw (unencoded) data
*/
secure_vector<uint8_t> PSSR_Raw::raw_data()
{
secure_vector<uint8_t> ret;
std::swap(ret, m_msg);
if(ret.size() != m_hash->output_length())
throw Encoding_Error("PSSR_Raw Bad input length, did not match hash");
return ret;
}
secure_vector<uint8_t> PSSR_Raw::encoding_of(const secure_vector<uint8_t>& msg,
size_t output_bits,
RandomNumberGenerator& rng)
{
secure_vector<uint8_t> salt = rng.random_vec(m_SALT_SIZE);
return pss_encode(*m_hash, msg, salt, output_bits);
}
/*
* PSSR_Raw Decode/Verify Operation
*/
bool PSSR_Raw::verify(const secure_vector<uint8_t>& coded,
const secure_vector<uint8_t>& raw,
size_t key_bits)
{
return pss_verify(*m_hash, coded, raw, key_bits);
}
}
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