bcrypt.cpp

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/*
* Bcrypt Password Hashing
* (C) 2010,2018,2020 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/bcrypt.h>
#include <botan/rng.h>
#include <botan/internal/blowfish.h>
#include <botan/base64.h>
#include <botan/internal/parsing.h>
#include <botan/internal/ct_utils.h>
 
namespace Botan {
 
namespace {
 
// Bcrypt uses a non-standard base64 alphabet
uint8_t base64_to_bcrypt_encoding(uint8_t c)
   {
   const auto is_ab = CT::Mask<uint8_t>::is_within_range(c, 'a', 'b');
   const auto is_cz = CT::Mask<uint8_t>::is_within_range(c, 'c', 'z');
   const auto is_CZ = CT::Mask<uint8_t>::is_within_range(c, 'C', 'Z');
 
   const auto is_01 = CT::Mask<uint8_t>::is_within_range(c, '0', '1');
   const auto is_29 = CT::Mask<uint8_t>::is_within_range(c, '2', '9');
 
   const auto is_A = CT::Mask<uint8_t>::is_equal(c, 'A');
   const auto is_B = CT::Mask<uint8_t>::is_equal(c, 'B');
   const auto is_plus = CT::Mask<uint8_t>::is_equal(c, '+');
   const auto is_slash = CT::Mask<uint8_t>::is_equal(c, '/');
 
   uint8_t ret = 0x80;
   ret = is_ab.select(c - 'a' + 'Y', ret);
   ret = is_cz.select(c - 2, ret);
   ret = is_CZ.select(c - 2, ret);
   ret = is_01.select(c - '0' + 'y', ret);
   ret = is_29.select(c - '2' + '0', ret);
   ret = is_A.select('.', ret);
   ret = is_B.select('/', ret);
   ret = is_plus.select('8', ret);
   ret = is_slash.select('9', ret);
 
   return ret;
   }
 
uint8_t bcrypt_encoding_to_base64(uint8_t c)
   {
   const auto is_ax = CT::Mask<uint8_t>::is_within_range(c, 'a', 'x');
   const auto is_yz = CT::Mask<uint8_t>::is_within_range(c, 'y', 'z');
 
   const auto is_AX = CT::Mask<uint8_t>::is_within_range(c, 'A', 'X');
   const auto is_YZ = CT::Mask<uint8_t>::is_within_range(c, 'Y', 'Z');
   const auto is_07 = CT::Mask<uint8_t>::is_within_range(c, '0', '7');
 
   const auto is_8 = CT::Mask<uint8_t>::is_equal(c, '8');
   const auto is_9 = CT::Mask<uint8_t>::is_equal(c, '9');
   const auto is_dot = CT::Mask<uint8_t>::is_equal(c, '.');
   const auto is_slash = CT::Mask<uint8_t>::is_equal(c, '/');
 
   uint8_t ret = 0x80;
   ret = is_ax.select(c - 'a' + 'c', ret);
   ret = is_yz.select(c - 'y' + '0', ret);
   ret = is_AX.select(c - 'A' + 'C', ret);
   ret = is_YZ.select(c - 'Y' + 'a', ret);
   ret = is_07.select(c - '0' + '2', ret);
   ret = is_8.select('+', ret);
   ret = is_9.select('/', ret);
   ret = is_dot.select('A', ret);
   ret = is_slash.select('B', ret);
 
   return ret;
   }
 
std::string bcrypt_base64_encode(const uint8_t input[], size_t length)
   {
   std::string b64 = base64_encode(input, length);
 
   while(!b64.empty() && b64[b64.size()-1] == '=')
      b64 = b64.substr(0, b64.size() - 1);
 
   for(size_t i = 0; i != b64.size(); ++i)
      b64[i] = static_cast<char>(base64_to_bcrypt_encoding(static_cast<uint8_t>(b64[i])));;
 
   return b64;
   }
 
std::vector<uint8_t> bcrypt_base64_decode(std::string input)
   {
   for(size_t i = 0; i != input.size(); ++i)
      input[i] = bcrypt_encoding_to_base64(static_cast<uint8_t>(input[i]));
 
   return unlock(base64_decode(input));
   }
 
std::string make_bcrypt(const std::string& pass,
                        const std::vector<uint8_t>& salt,
                        uint16_t work_factor,
                        char version)
   {
   /*
   * On a 4 GHz Skylake, workfactor == 18 takes about 15 seconds to
   * hash a password. This seems like a reasonable upper bound for the
   * time being.
   * Bcrypt allows up to work factor 31 (2^31 iterations)
   */
   BOTAN_ARG_CHECK(work_factor >= 4 && work_factor <= 18,
                   "Invalid bcrypt work factor");
 
   alignas(64) static const uint8_t BCRYPT_MAGIC[8*3] = {
      0x4F, 0x72, 0x70, 0x68, 0x65, 0x61, 0x6E, 0x42,
      0x65, 0x68, 0x6F, 0x6C, 0x64, 0x65, 0x72, 0x53,
      0x63, 0x72, 0x79, 0x44, 0x6F, 0x75, 0x62, 0x74
   };
 
   Blowfish blowfish;
 
   // Include the trailing NULL byte, so we need c_str() not data()
   blowfish.salted_set_key(cast_char_ptr_to_uint8(pass.c_str()),
                           pass.length() + 1,
                           salt.data(),
                           salt.size(),
                           work_factor);
 
   std::vector<uint8_t> ctext(BCRYPT_MAGIC, BCRYPT_MAGIC + 8*3);
 
   for(size_t i = 0; i != 64; ++i)
      blowfish.encrypt_n(ctext.data(), ctext.data(), 3);
 
   std::string salt_b64 = bcrypt_base64_encode(salt.data(), salt.size());
 
   std::string work_factor_str = std::to_string(work_factor);
   if(work_factor_str.length() == 1)
      work_factor_str = "0" + work_factor_str;
 
   return "$2" + std::string(1, version) + "$" + work_factor_str +
          "$" + salt_b64.substr(0, 22) +
          bcrypt_base64_encode(ctext.data(), ctext.size() - 1);
   }
 
}
 
std::string generate_bcrypt(const std::string& pass,
                            RandomNumberGenerator& rng,
                            uint16_t work_factor,
                            char version)
   {
   /*
   2a, 2b and 2y are identical for our purposes because our implementation of 2a
   never had the truncation or signed char bugs in the first place.
   */
 
   if(version != 'a' && version != 'b' && version != 'y')
      throw Invalid_Argument("Unknown bcrypt version '" + std::string(1, version) + "'");
 
   std::vector<uint8_t> salt;
   rng.random_vec(salt, 16);
   return make_bcrypt(pass, salt, work_factor, version);
   }
 
bool check_bcrypt(const std::string& pass, const std::string& hash)
   {
   if(hash.size() != 60 ||
      hash[0] != '$' || hash[1] != '2' || hash[3] != '$' || hash[6] != '$')
      {
      return false;
      }
 
   const char bcrypt_version = hash[2];
 
   if(bcrypt_version != 'a' && bcrypt_version != 'b' && bcrypt_version != 'y')
      {
      return false;
      }
 
   const uint16_t workfactor = to_uint16(hash.substr(4, 2));
 
   const std::vector<uint8_t> salt = bcrypt_base64_decode(hash.substr(7, 22));
   if(salt.size() != 16)
      return false;
 
   const std::string compare = make_bcrypt(pass, salt, workfactor, bcrypt_version);
 
   return same_mem(hash.data(), compare.data(), compare.size());
   }
 
}