File: bcrypt.cpp

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/*
* Bcrypt Password Hashing
* (C) 2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#include <botan/bcrypt.h>
#include <botan/loadstor.h>
#include <botan/libstate.h>
#include <botan/blowfish.h>
#include <botan/base64.h>

namespace Botan {

namespace {

std::string bcrypt_base64_encode(const byte input[], size_t length)
   {
   // Bcrypt uses a non-standard base64 alphabet
   const byte OPENBSD_BASE64_SUB[256] = {
      0x00, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x38, 0x80, 0x80, 0x80, 0x39,
      0x79, 0x7A, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x2E, 0x2F, 0x41, 0x42, 0x43, 0x44, 0x45,
      0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50, 0x51,
      0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x59, 0x5A, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,
      0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75,
      0x76, 0x77, 0x78, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80
   };

   std::string b64 = base64_encode(input, length);

   while(b64.size() && b64[b64.size()-1] == '=')
      b64 = b64.substr(0, b64.size() - 1);

   for(size_t i = 0; i != b64.size(); ++i)
      b64[i] = OPENBSD_BASE64_SUB[static_cast<byte>(b64[i])];

   return b64;
   }

MemoryVector<byte> bcrypt_base64_decode(std::string input)
   {
   const byte OPENBSD_BASE64_SUB[256] = {
      0x00, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x41, 0x42,
      0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x2B, 0x2F, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,
      0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F, 0x50, 0x51, 0x52, 0x53, 0x54, 0x55,
      0x56, 0x57, 0x58, 0x59, 0x5A, 0x61, 0x62, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D,
      0x6E, 0x6F, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,
      0x7A, 0x30, 0x31, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
      0x80, 0x80, 0x80, 0x80
   };

   for(size_t i = 0; i != input.size(); ++i)
      input[i] = OPENBSD_BASE64_SUB[static_cast<byte>(input[i])];

   return base64_decode(input);
   }

std::string make_bcrypt(const std::string& pass,
                        const MemoryRegion<byte>& salt,
                        u16bit work_factor)
   {
   const byte magic[24] = {
      0x4F, 0x72, 0x70, 0x68, 0x65, 0x61, 0x6E, 0x42,
      0x65, 0x68, 0x6F, 0x6C, 0x64, 0x65, 0x72, 0x53,
      0x63, 0x72, 0x79, 0x44, 0x6F, 0x75, 0x62, 0x74
   };

   MemoryVector<byte> ctext(magic, 24);

   Blowfish blowfish;

   // Include the trailing NULL byte
   blowfish.eks_key_schedule(reinterpret_cast<const byte*>(pass.c_str()),
                             pass.length() + 1,
                             salt,
                             work_factor);

   for(size_t i = 0; i != 64; ++i)
      blowfish.encrypt_n(&ctext[0], &ctext[0], 3);

   std::string salt_b64 = bcrypt_base64_encode(&salt[0], salt.size());

   return "$2a$" + to_string(work_factor, 2) + "$" + salt_b64.substr(0, 22) +
             bcrypt_base64_encode(&ctext[0], ctext.size() - 1);
   }

}

std::string generate_bcrypt(const std::string& pass,
                            RandomNumberGenerator& rng,
                            u16bit work_factor)
   {
   return make_bcrypt(pass, rng.random_vec(16), work_factor);
   }

bool check_bcrypt(const std::string& pass, const std::string& hash)
   {
   if(hash.size() != 60 ||
      hash[0] != '$' || hash[1] != '2' || hash[2] != 'a' ||
      hash[3] != '$' || hash[6] != '$')
      {
      return false;
      }

   const u16bit workfactor = to_u32bit(hash.substr(4, 2));

   MemoryVector<byte> salt = bcrypt_base64_decode(hash.substr(7, 22));

   const std::string compare = make_bcrypt(pass, salt, workfactor);

   return (hash == compare);
   }

}