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/*
* Passhash9 Password Hashing
* (C) 2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/passhash9.h>
#include <botan/loadstor.h>
#include <botan/libstate.h>
#include <botan/pbkdf2.h>
#include <botan/base64.h>
#include <botan/pipe.h>
namespace Botan {
namespace {
const std::string MAGIC_PREFIX = "$9$";
const u32bit WORKFACTOR_BYTES = 2;
const u32bit ALGID_BYTES = 1;
const u32bit SALT_BYTES = 12; // 96 bits of salt
const u32bit PBKDF_OUTPUT_LEN = 24; // 192 bits output
const u32bit WORK_FACTOR_SCALE = 10000;
MessageAuthenticationCode* get_pbkdf_prf(byte alg_id)
{
Algorithm_Factory& af = global_state().algorithm_factory();
try
{
if(alg_id == 0)
return af.make_mac("HMAC(SHA-1)");
}
catch(Algorithm_Not_Found) {}
return 0;
}
std::pair<byte, MessageAuthenticationCode*> choose_pbkdf_prf()
{
for(byte alg_id = 0; alg_id != 255; ++alg_id)
{
MessageAuthenticationCode* prf = get_pbkdf_prf(alg_id);
if(prf)
return std::make_pair(alg_id, prf);
}
throw Internal_Error("Passhash9: No PRF available");
}
}
std::string generate_passhash9(const std::string& pass,
RandomNumberGenerator& rng,
u16bit work_factor)
{
std::pair<byte, MessageAuthenticationCode*> prf = choose_pbkdf_prf();
byte alg_id = prf.first;
PKCS5_PBKDF2 kdf(prf.second); // takes ownership of pointer
SecureVector<byte> salt(SALT_BYTES);
rng.randomize(&salt[0], salt.size());
u32bit kdf_iterations = WORK_FACTOR_SCALE * work_factor;
SecureVector<byte> pbkdf2_output =
kdf.derive_key(PBKDF_OUTPUT_LEN, pass,
&salt[0], salt.size(),
kdf_iterations).bits_of();
Pipe pipe(new Base64_Encoder);
pipe.start_msg();
pipe.write(alg_id);
pipe.write(get_byte(0, work_factor));
pipe.write(get_byte(1, work_factor));
pipe.write(salt);
pipe.write(pbkdf2_output);
pipe.end_msg();
return MAGIC_PREFIX + pipe.read_all_as_string();
}
bool check_passhash9(const std::string& pass, const std::string& hash)
{
const u32bit BINARY_LENGTH =
(ALGID_BYTES + WORKFACTOR_BYTES + PBKDF_OUTPUT_LEN + SALT_BYTES);
const u32bit BASE64_LENGTH =
MAGIC_PREFIX.size() + (BINARY_LENGTH * 8) / 6;
if(hash.size() != BASE64_LENGTH)
return false;
for(size_t i = 0; i != MAGIC_PREFIX.size(); ++i)
if(hash[i] != MAGIC_PREFIX[i])
return false;
Pipe pipe(new Base64_Decoder);
pipe.start_msg();
pipe.write(hash.c_str() + MAGIC_PREFIX.size());
pipe.end_msg();
SecureVector<byte> bin = pipe.read_all();
if(bin.size() != BINARY_LENGTH)
return false;
byte alg_id = bin[0];
u32bit kdf_iterations =
WORK_FACTOR_SCALE * load_be<u16bit>(bin + ALGID_BYTES, 0);
if(kdf_iterations == 0)
return false;
MessageAuthenticationCode* pbkdf_prf = get_pbkdf_prf(alg_id);
if(pbkdf_prf == 0)
return false; // unknown algorithm, reject
PKCS5_PBKDF2 kdf(pbkdf_prf); // takes ownership of pointer
SecureVector<byte> cmp = kdf.derive_key(
PBKDF_OUTPUT_LEN, pass,
&bin[ALGID_BYTES + WORKFACTOR_BYTES], SALT_BYTES,
kdf_iterations).bits_of();
return same_mem(cmp.begin(),
bin.begin() + ALGID_BYTES + WORKFACTOR_BYTES + SALT_BYTES,
PBKDF_OUTPUT_LEN);
}
}
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