Botan  2.4.0
Crypto and TLS for C++11
hotp.cpp
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1 /*
2 * HOTP
3 * (C) 2017 Jack Lloyd
4 *
5 * Botan is released under the Simplified BSD License (see license.txt)
6 */
7 
8 #include <botan/hotp.h>
9 
10 namespace Botan {
11 
12 HOTP::HOTP(const SymmetricKey& key, const std::string& hash_algo, size_t digits)
13  {
14  if(digits == 6)
15  m_digit_mod = 1000000;
16  else if(digits == 7)
17  m_digit_mod = 10000000;
18  else if(digits == 8)
19  m_digit_mod = 100000000;
20  else
21  throw Invalid_Argument("Invalid HOTP digits");
22 
23  /*
24  RFC 4228 only supports SHA-1 but TOTP allows SHA-256 and SHA-512
25  and some HOTP libs support one or both as extensions
26  */
27  if(hash_algo == "SHA-1")
28  m_mac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-1)");
29  else if(hash_algo == "SHA-256")
30  m_mac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
31  else if(hash_algo == "SHA-512")
32  m_mac = MessageAuthenticationCode::create_or_throw("HMAC(SHA-512)");
33  else
34  throw Invalid_Argument("Unsupported HOTP hash function");
35 
36  m_mac->set_key(key);
37  }
38 
39 uint32_t HOTP::generate_hotp(uint64_t counter)
40  {
41  uint8_t counter8[8] = { 0 };
42  store_be(counter, counter8);
43  m_mac->update(counter8, sizeof(counter8));
44  const secure_vector<uint8_t> mac = m_mac->final();
45 
46  const size_t offset = mac[mac.size()-1] & 0x0F;
47  const uint32_t code = load_be<uint32_t>(mac.data() + offset, 0) & 0x7FFFFFFF;
48  return code % m_digit_mod;
49  }
50 
51 std::pair<bool,uint64_t> HOTP::verify_hotp(uint32_t otp, uint64_t starting_counter, size_t resync_range)
52  {
53  for(size_t i = 0; i <= resync_range; ++i)
54  {
55  if(generate_hotp(starting_counter + i) == otp)
56  return std::make_pair(true, starting_counter + i + 1);
57  }
58  return std::make_pair(false, starting_counter);
59  }
60 
61 }
62 
void store_be(uint16_t in, uint8_t out[2])
Definition: loadstor.h:434
uint32_t load_be< uint32_t >(const uint8_t in[], size_t off)
Definition: loadstor.h:177
Definition: alg_id.cpp:13
AlgorithmIdentifier hash_algo
Definition: x509_obj.cpp:22
HOTP(const SymmetricKey &key, const std::string &hash_algo="SHA-1", size_t digits=6)
Definition: hotp.cpp:12
std::pair< bool, uint64_t > verify_hotp(uint32_t otp, uint64_t starting_counter, size_t resync_range=0)
Definition: hotp.cpp:51
static std::unique_ptr< MessageAuthenticationCode > create_or_throw(const std::string &algo_spec, const std::string &provider="")
Definition: mac.cpp:140
std::vector< T, secure_allocator< T > > secure_vector
Definition: secmem.h:88
uint32_t generate_hotp(uint64_t counter)
Definition: hotp.cpp:39