passhash9.cpp

Go to the documentation of this file.

/*
* Passhash9 Password Hashing
* (C) 2010 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/passhash9.h>
#include <botan/rng.h>
#include <botan/internal/loadstor.h>
#include <botan/pbkdf2.h>
#include <botan/base64.h>
 
namespace Botan {
 
namespace {
 
const std::string MAGIC_PREFIX = "$9$";
 
const size_t WORKFACTOR_BYTES = 2;
const size_t ALGID_BYTES = 1;
const size_t SALT_BYTES = 12; // 96 bits of salt
const size_t PASSHASH9_PBKDF_OUTPUT_LEN = 24; // 192 bits output
 
const size_t WORK_FACTOR_SCALE = 10000;
 
std::unique_ptr<MessageAuthenticationCode> get_pbkdf_prf(uint8_t alg_id)
   {
   if(alg_id == 0)
      return MessageAuthenticationCode::create("HMAC(SHA-1)");
   else if(alg_id == 1)
      return MessageAuthenticationCode::create("HMAC(SHA-256)");
   else if(alg_id == 2)
      return MessageAuthenticationCode::create("CMAC(Blowfish)");
   else if(alg_id == 3)
      return MessageAuthenticationCode::create("HMAC(SHA-384)");
   else if(alg_id == 4)
      return MessageAuthenticationCode::create("HMAC(SHA-512)");
   return nullptr;
   }
 
}
 
std::string generate_passhash9(std::string_view pass,
                               RandomNumberGenerator& rng,
                               uint16_t work_factor,
                               uint8_t alg_id)
   {
   BOTAN_ARG_CHECK(work_factor > 0 && work_factor < 512, "Invalid Passhash9 work factor");
 
   auto prf = get_pbkdf_prf(alg_id);
 
   if(!prf)
      throw Invalid_Argument("Passhash9: Algorithm id " +
                             std::to_string(alg_id) +
                             " is not defined");
 
   PKCS5_PBKDF2 kdf(std::move(prf));
 
   secure_vector<uint8_t> salt(SALT_BYTES);
   rng.randomize(salt.data(), salt.size());
 
   const size_t kdf_iterations = WORK_FACTOR_SCALE * work_factor;
 
   secure_vector<uint8_t> blob;
   blob.push_back(alg_id);
   blob.push_back(get_byte<0>(work_factor));
   blob.push_back(get_byte<1>(work_factor));
   blob += salt;
   blob += kdf.derive_key(PASSHASH9_PBKDF_OUTPUT_LEN,
                          pass,
                          salt.data(), salt.size(),
                          kdf_iterations).bits_of();
 
   return MAGIC_PREFIX + base64_encode(blob);
   }
 
bool check_passhash9(std::string_view pass, std::string_view hash)
   {
   const size_t BINARY_LENGTH =
     ALGID_BYTES +
     WORKFACTOR_BYTES +
     PASSHASH9_PBKDF_OUTPUT_LEN +
     SALT_BYTES;
 
   const size_t 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;
 
   secure_vector<uint8_t> bin = base64_decode(hash.data() + MAGIC_PREFIX.size());
 
   if(bin.size() != BINARY_LENGTH)
      return false;
 
   uint8_t alg_id = bin[0];
 
   const size_t work_factor = load_be<uint16_t>(&bin[ALGID_BYTES], 0);
 
   // Bug in the format, bad states shouldn't be representable, but are...
   if(work_factor == 0)
      return false;
 
   if(work_factor > 512)
      throw Invalid_Argument("Requested passhash9 work factor " +
                             std::to_string(work_factor) + " is too large");
 
   const size_t kdf_iterations = WORK_FACTOR_SCALE * work_factor;
 
   auto pbkdf_prf = get_pbkdf_prf(alg_id);
 
   if(!pbkdf_prf)
      return false; // unknown algorithm, reject
 
   PKCS5_PBKDF2 kdf(std::move(pbkdf_prf));
 
   secure_vector<uint8_t> cmp = kdf.derive_key(
      PASSHASH9_PBKDF_OUTPUT_LEN,
      pass,
      &bin[ALGID_BYTES + WORKFACTOR_BYTES], SALT_BYTES,
      kdf_iterations).bits_of();
 
   return constant_time_compare(cmp.data(),
                   &bin[ALGID_BYTES + WORKFACTOR_BYTES + SALT_BYTES],
                   PASSHASH9_PBKDF_OUTPUT_LEN);
   }
 
bool is_passhash9_alg_supported(uint8_t alg_id)
   {
   if (get_pbkdf_prf(alg_id))
      {
      return true;
      }
   return false;
   }
 
}