pkcs8.cpp

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/*
* PKCS #8
* (C) 1999-2010,2014,2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/pkcs8.h>
#include <botan/rng.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/asn1_obj.h>
#include <botan/oids.h>
#include <botan/pem.h>
#include <botan/internal/scan_name.h>
#include <botan/pk_algs.h>
 
#if defined(BOTAN_HAS_PKCS5_PBES2)
   #include <botan/internal/pbes2.h>
#endif
 
namespace Botan::PKCS8 {
 
namespace {
 
/*
* Get info from an EncryptedPrivateKeyInfo
*/
secure_vector<uint8_t> PKCS8_extract(DataSource& source,
                                  AlgorithmIdentifier& pbe_alg_id)
   {
   secure_vector<uint8_t> key_data;
 
   BER_Decoder(source)
      .start_sequence()
         .decode(pbe_alg_id)
         .decode(key_data, ASN1_Type::OctetString)
      .verify_end();
 
   return key_data;
   }
 
/*
* PEM decode and/or decrypt a private key
*/
secure_vector<uint8_t> PKCS8_decode(
   DataSource& source,
   const std::function<std::string ()>& get_passphrase,
   AlgorithmIdentifier& pk_alg_id,
   bool is_encrypted)
   {
   AlgorithmIdentifier pbe_alg_id;
   secure_vector<uint8_t> key_data, key;
 
   try {
      if(ASN1::maybe_BER(source) && !PEM_Code::matches(source))
         {
         if(is_encrypted)
            {
            key_data = PKCS8_extract(source, pbe_alg_id);
            }
         else
            {
            // todo read more efficiently
            while(!source.end_of_data())
               {
               uint8_t b;
               size_t read = source.read_byte(b);
               if(read)
                  {
                  key_data.push_back(b);
                  }
               }
            }
         }
      else
         {
         std::string label;
         key_data = PEM_Code::decode(source, label);
 
         // todo remove autodetect for pem as well?
         if(label == "PRIVATE KEY")
            is_encrypted = false;
         else if(label == "ENCRYPTED PRIVATE KEY")
            {
            DataSource_Memory key_source(key_data);
            key_data = PKCS8_extract(key_source, pbe_alg_id);
            }
         else
            throw PKCS8_Exception("Unknown PEM label " + label);
         }
 
      if(key_data.empty())
         throw PKCS8_Exception("No key data found");
      }
   catch(Decoding_Error& e)
      {
      throw Decoding_Error("PKCS #8 private key decoding", e);
      }
 
   try
      {
      if(is_encrypted)
         {
         if(OIDS::oid2str_or_throw(pbe_alg_id.get_oid()) != "PBE-PKCS5v20")
            throw PKCS8_Exception("Unknown PBE type " + pbe_alg_id.get_oid().to_string());
#if defined(BOTAN_HAS_PKCS5_PBES2)
         key = pbes2_decrypt(key_data, get_passphrase(), pbe_alg_id.get_parameters());
#else
         BOTAN_UNUSED(get_passphrase);
         throw Decoding_Error("Private key is encrypted but PBES2 was disabled in build");
#endif
         }
      else
         key = key_data;
 
      BER_Decoder(key)
         .start_sequence()
            .decode_and_check<size_t>(0, "Unknown PKCS #8 version number")
            .decode(pk_alg_id)
            .decode(key, ASN1_Type::OctetString)
            .discard_remaining()
         .end_cons();
      }
   catch(std::exception& e)
      {
      throw Decoding_Error("PKCS #8 private key decoding", e);
      }
   return key;
   }
 
}
 
/*
* PEM encode a PKCS #8 private key, unencrypted
*/
std::string PEM_encode(const Private_Key& key)
   {
   return PEM_Code::encode(key.private_key_info(), "PRIVATE KEY");
   }
 
#if defined(BOTAN_HAS_PKCS5_PBES2)
 
namespace {
 
std::pair<std::string, std::string>
choose_pbe_params(const std::string& pbe_algo, const std::string& key_algo)
   {
   if(pbe_algo.empty())
      {
      /*
      * For algorithms where we are using a non-RFC format anyway, default to
      * SIV or GCM. For others (RSA, ECDSA, ...) default to something widely
      * compatible.
      */
      const bool nonstandard_pk = (key_algo == "McEliece" || key_algo == "XMSS");
 
      if(nonstandard_pk)
         {
#if defined(BOTAN_HAS_AEAD_SIV) && defined(BOTAN_HAS_SHA2_64)
         return std::make_pair("AES-256/SIV", "SHA-512");
#elif defined(BOTAN_HAS_AEAD_GCM) && defined(BOTAN_HAS_SHA2_64)
         return std::make_pair("AES-256/GCM", "SHA-512");
#endif
         }
 
      // Default is something compatible with everyone else
      return std::make_pair("AES-256/CBC", "SHA-256");
      }
 
   SCAN_Name request(pbe_algo);
 
   if(request.arg_count() != 2 ||
      (request.algo_name() != "PBE-PKCS5v20" && request.algo_name() != "PBES2"))
      {
      throw Invalid_Argument("Unsupported PBE " + pbe_algo);
      }
 
   return std::make_pair(request.arg(0), request.arg(1));
   }
 
}
 
#endif
 
/*
* BER encode a PKCS #8 private key, encrypted
*/
std::vector<uint8_t> BER_encode(const Private_Key& key,
                             RandomNumberGenerator& rng,
                             const std::string& pass,
                             std::chrono::milliseconds msec,
                             const std::string& pbe_algo)
   {
#if defined(BOTAN_HAS_PKCS5_PBES2)
   const auto pbe_params = choose_pbe_params(pbe_algo, key.algo_name());
 
   const std::pair<AlgorithmIdentifier, std::vector<uint8_t>> pbe_info =
      pbes2_encrypt_msec(PKCS8::BER_encode(key), pass, msec, nullptr,
                         pbe_params.first, pbe_params.second, rng);
 
   std::vector<uint8_t> output;
   DER_Encoder der(output);
   der.start_sequence()
         .encode(pbe_info.first)
         .encode(pbe_info.second, ASN1_Type::OctetString)
      .end_cons();
 
   return output;
#else
   BOTAN_UNUSED(key, rng, pass, msec, pbe_algo);
   throw Encoding_Error("PKCS8::BER_encode cannot encrypt because PBES2 was disabled in build");
#endif
   }
 
/*
* PEM encode a PKCS #8 private key, encrypted
*/
std::string PEM_encode(const Private_Key& key,
                       RandomNumberGenerator& rng,
                       const std::string& pass,
                       std::chrono::milliseconds msec,
                       const std::string& pbe_algo)
   {
   if(pass.empty())
      return PEM_encode(key);
 
   return PEM_Code::encode(PKCS8::BER_encode(key, rng, pass, msec, pbe_algo),
                           "ENCRYPTED PRIVATE KEY");
   }
 
/*
* BER encode a PKCS #8 private key, encrypted
*/
std::vector<uint8_t> BER_encode_encrypted_pbkdf_iter(const Private_Key& key,
                                                     RandomNumberGenerator& rng,
                                                     const std::string& pass,
                                                     size_t pbkdf_iterations,
                                                     const std::string& cipher,
                                                     const std::string& pbkdf_hash)
   {
#if defined(BOTAN_HAS_PKCS5_PBES2)
   const std::pair<AlgorithmIdentifier, std::vector<uint8_t>> pbe_info =
      pbes2_encrypt_iter(key.private_key_info(),
                         pass, pbkdf_iterations,
                         cipher.empty() ? "AES-256/CBC" : cipher,
                         pbkdf_hash.empty() ? "SHA-256" : pbkdf_hash,
                         rng);
 
   std::vector<uint8_t> output;
   DER_Encoder der(output);
   der.start_sequence()
         .encode(pbe_info.first)
         .encode(pbe_info.second, ASN1_Type::OctetString)
      .end_cons();
 
   return output;
 
#else
   BOTAN_UNUSED(key, rng, pass, pbkdf_iterations, cipher, pbkdf_hash);
   throw Encoding_Error("PKCS8::BER_encode_encrypted_pbkdf_iter cannot encrypt because PBES2 disabled in build");
#endif
   }
 
/*
* PEM encode a PKCS #8 private key, encrypted
*/
std::string PEM_encode_encrypted_pbkdf_iter(const Private_Key& key,
                                            RandomNumberGenerator& rng,
                                            const std::string& pass,
                                            size_t pbkdf_iterations,
                                            const std::string& cipher,
                                            const std::string& pbkdf_hash)
   {
   return PEM_Code::encode(
      PKCS8::BER_encode_encrypted_pbkdf_iter(key, rng, pass, pbkdf_iterations, cipher, pbkdf_hash),
      "ENCRYPTED PRIVATE KEY");
   }
 
/*
* BER encode a PKCS #8 private key, encrypted
*/
std::vector<uint8_t> BER_encode_encrypted_pbkdf_msec(const Private_Key& key,
                                                     RandomNumberGenerator& rng,
                                                     const std::string& pass,
                                                     std::chrono::milliseconds pbkdf_msec,
                                                     size_t* pbkdf_iterations,
                                                     const std::string& cipher,
                                                     const std::string& pbkdf_hash)
   {
#if defined(BOTAN_HAS_PKCS5_PBES2)
   const std::pair<AlgorithmIdentifier, std::vector<uint8_t>> pbe_info =
      pbes2_encrypt_msec(key.private_key_info(), pass,
                         pbkdf_msec, pbkdf_iterations,
                         cipher.empty() ? "AES-256/CBC" : cipher,
                         pbkdf_hash.empty() ? "SHA-256" : pbkdf_hash,
                         rng);
 
   std::vector<uint8_t> output;
   DER_Encoder(output)
      .start_sequence()
         .encode(pbe_info.first)
         .encode(pbe_info.second, ASN1_Type::OctetString)
      .end_cons();
 
   return output;
#else
   BOTAN_UNUSED(key, rng, pass, pbkdf_msec, pbkdf_iterations, cipher, pbkdf_hash);
   throw Encoding_Error("BER_encode_encrypted_pbkdf_msec cannot encrypt because PBES2 disabled in build");
#endif
   }
 
/*
* PEM encode a PKCS #8 private key, encrypted
*/
std::string PEM_encode_encrypted_pbkdf_msec(const Private_Key& key,
                                            RandomNumberGenerator& rng,
                                            const std::string& pass,
                                            std::chrono::milliseconds pbkdf_msec,
                                            size_t* pbkdf_iterations,
                                            const std::string& cipher,
                                            const std::string& pbkdf_hash)
   {
   return PEM_Code::encode(
      PKCS8::BER_encode_encrypted_pbkdf_msec(key, rng, pass, pbkdf_msec, pbkdf_iterations, cipher, pbkdf_hash),
      "ENCRYPTED PRIVATE KEY");
   }
 
namespace {
 
/*
* Extract a private key (encrypted/unencrypted) and return it
*/
std::unique_ptr<Private_Key>
load_key(DataSource& source,
         const std::function<std::string ()>& get_pass,
         bool is_encrypted)
   {
   AlgorithmIdentifier alg_id;
   secure_vector<uint8_t> pkcs8_key = PKCS8_decode(source, get_pass, alg_id, is_encrypted);
 
   const std::string alg_name = OIDS::oid2str_or_empty(alg_id.get_oid());
   if(alg_name.empty())
      throw PKCS8_Exception("Unknown algorithm OID: " +
                            alg_id.get_oid().to_string());
 
   return load_private_key(alg_id, pkcs8_key);
   }
 
}
 
/*
* Extract an encrypted private key and return it
*/
std::unique_ptr<Private_Key> load_key(DataSource& source,
                                      const std::function<std::string ()>& get_pass)
   {
   return load_key(source, get_pass, true);
   }
 
/*
* Extract an encrypted private key and return it
*/
std::unique_ptr<Private_Key> load_key(DataSource& source,
                                      const std::string& pass)
   {
   // We need to use bind rather than a lambda capturing `pass` here in order to avoid a Clang 8 bug.
   // See https://github.com/randombit/botan/issues/2255.
   return load_key(source, std::bind([](const std::string& p) { return p; }, pass), true);
   }
 
/*
* Extract an unencrypted private key and return it
*/
std::unique_ptr<Private_Key> load_key(DataSource& source)
   {
   auto fail_fn = []() -> std::string {
      throw PKCS8_Exception("Internal error: Attempt to read password for unencrypted key");
   };
 
   return load_key(source, fail_fn, false);
   }
 
}