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randombit / botan / 18978562474

31 Oct 2025 04:18PM UTC coverage: 90.672% (+0.003%) from 90.669%
18978562474

Pull #5124

github

web-flow
Merge 30546bc9a into 72715a0cf
Pull Request #5124: Cooperative Cancellation in PasswordHash

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94.52
/src/lib/pbkdf/bcrypt_pbkdf/bcrypt_pbkdf.cpp
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/*
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* (C) 2018,2019 Jack Lloyd
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*
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* Botan is released under the Simplified BSD License (see license.txt)
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*/
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#include <botan/bcrypt_pbkdf.h>
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#include <botan/hash.h>
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#include <botan/internal/blowfish.h>
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#include <botan/internal/fmt.h>
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#include <botan/internal/loadstor.h>
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#include <botan/internal/mem_utils.h>
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#include <botan/internal/time_utils.h>
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namespace Botan {
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Bcrypt_PBKDF::Bcrypt_PBKDF(size_t iterations) : m_iterations(iterations) {
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   BOTAN_ARG_CHECK(m_iterations > 0, "Invalid Bcrypt-PBKDF iterations");
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}
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std::string Bcrypt_PBKDF::to_string() const {
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   return fmt("Bcrypt-PBKDF({})", m_iterations);
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}
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std::string Bcrypt_PBKDF_Family::name() const {
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   return "Bcrypt-PBKDF";
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}
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std::unique_ptr<PasswordHash> Bcrypt_PBKDF_Family::tune(size_t output_length,
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                                                        std::chrono::milliseconds msec,
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                                                        size_t /*max_memory*/,
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                                                        std::chrono::milliseconds tune_time) const {
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   const size_t blocks = (output_length + 32 - 1) / 32;
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   if(blocks == 0) {
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      return default_params();
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   }
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   const size_t starting_iter = 2;
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   auto pwhash = this->from_iterations(starting_iter);
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   auto tune_fn = [&]() {
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      uint8_t output[32] = {0};
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      pwhash->derive_key(output, sizeof(output), "test", 4, nullptr, 0);
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   };
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   const uint64_t measured_time = measure_cost(tune_time, tune_fn) / blocks;
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   const uint64_t target_nsec = msec.count() * static_cast<uint64_t>(1000000);
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   const uint64_t desired_increase = target_nsec / measured_time;
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   if(desired_increase == 0) {
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      return this->from_iterations(starting_iter);
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   }
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   return this->from_iterations(static_cast<size_t>(desired_increase * starting_iter));
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}
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std::unique_ptr<PasswordHash> Bcrypt_PBKDF_Family::default_params() const {
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   return this->from_iterations(32);  // About 100 ms on fast machine
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}
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std::unique_ptr<PasswordHash> Bcrypt_PBKDF_Family::from_iterations(size_t iterations) const {
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   return std::make_unique<Bcrypt_PBKDF>(iterations);
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}
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std::unique_ptr<PasswordHash> Bcrypt_PBKDF_Family::from_params(size_t iterations, size_t /*t*/, size_t /*p*/) const {
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   return this->from_iterations(iterations);
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}
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namespace {
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void bcrypt_round(Blowfish& blowfish,
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                  const secure_vector<uint8_t>& pass_hash,
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                  const secure_vector<uint8_t>& salt_hash,
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                  secure_vector<uint8_t>& out,
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                  secure_vector<uint8_t>& tmp) {
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   const size_t BCRYPT_PBKDF_OUTPUT = 32;
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   // "OxychromaticBlowfishSwatDynamite"
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   alignas(64) static const uint8_t BCRYPT_PBKDF_MAGIC[BCRYPT_PBKDF_OUTPUT] = {
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      0x4F, 0x78, 0x79, 0x63, 0x68, 0x72, 0x6F, 0x6D, 0x61, 0x74, 0x69, 0x63, 0x42, 0x6C, 0x6F, 0x77,
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      0x66, 0x69, 0x73, 0x68, 0x53, 0x77, 0x61, 0x74, 0x44, 0x79, 0x6E, 0x61, 0x6D, 0x69, 0x74, 0x65};
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   const size_t BCRYPT_PBKDF_WORKFACTOR = 6;
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   const size_t BCRYPT_PBKDF_ROUNDS = 64;
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   blowfish.salted_set_key(
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      pass_hash.data(), pass_hash.size(), salt_hash.data(), salt_hash.size(), BCRYPT_PBKDF_WORKFACTOR, true);
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   copy_mem(tmp.data(), BCRYPT_PBKDF_MAGIC, BCRYPT_PBKDF_OUTPUT);
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   for(size_t i = 0; i != BCRYPT_PBKDF_ROUNDS; ++i) {
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      blowfish.encrypt(tmp);
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   }
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   /*
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   Bcrypt PBKDF loads the Blowfish output as big endian for no reason
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   in particular. We can't just swap everything once at the end
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   because the (big-endian) values are fed into SHA-512 to generate
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   the salt for the next round
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   */
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   for(size_t i = 0; i != 32 / 4; ++i) {
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      const uint32_t w = load_le<uint32_t>(tmp.data(), i);
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      store_be(w, &tmp[sizeof(uint32_t) * i]);
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   }
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   xor_buf(out.data(), tmp.data(), BCRYPT_PBKDF_OUTPUT);
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}
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}  // namespace
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void Bcrypt_PBKDF::derive_key(uint8_t output[],
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                              size_t output_len,
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                              const char* password,
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                              size_t password_len,
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                              const uint8_t salt[],
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                              size_t salt_len,
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                              const std::optional<std::stop_token>& stop_token) const {
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   // No output desired, so we are all done already...
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   if(output_len == 0) {
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      return;
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   }
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   BOTAN_ARG_CHECK(output_len <= 10 * 1024 * 1024, "Too much output for Bcrypt PBKDF");
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   const size_t BCRYPT_BLOCK_SIZE = 32;
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   const size_t blocks = (output_len + BCRYPT_BLOCK_SIZE - 1) / BCRYPT_BLOCK_SIZE;
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   auto sha512 = HashFunction::create_or_throw("SHA-512");
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   const auto pass_hash = sha512->process(as_span_of_bytes(password, password_len));
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   secure_vector<uint8_t> salt_hash(sha512->output_length());
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   Blowfish blowfish;
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   secure_vector<uint8_t> out(BCRYPT_BLOCK_SIZE);
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   secure_vector<uint8_t> tmp(BCRYPT_BLOCK_SIZE);
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   for(size_t block = 0; block != blocks; ++block) {
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      clear_mem(out.data(), out.size());
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      sha512->update(salt, salt_len);
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      sha512->update_be(static_cast<uint32_t>(block + 1));
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      sha512->final(salt_hash.data());
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      bcrypt_round(blowfish, pass_hash, salt_hash, out, tmp);
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      for(size_t r = 1; r < m_iterations; ++r) {
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         if((r & 63) == 0 && stop_token.has_value() && stop_token->stop_requested()) {
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            throw Botan::Operation_Canceled("scrypt");
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         }
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         // Next salt is H(prev_output)
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         sha512->update(tmp);
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         sha512->final(salt_hash.data());
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         bcrypt_round(blowfish, pass_hash, salt_hash, out, tmp);
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      }
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      for(size_t i = 0; i != BCRYPT_BLOCK_SIZE; ++i) {
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         const size_t dest = i * blocks + block;
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         if(dest < output_len) {
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            output[dest] = out[i];
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         }
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      }
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   }
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}
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}  // namespace Botan
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