/*

* (C) 1999-2010,2015,2018 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/pubkey.h>

#include <botan/der_enc.h>

#include <botan/ber_dec.h>

#include <botan/bigint.h>

#include <botan/internal/pk_ops.h>

#include <botan/internal/ct_utils.h>

#include <botan/rng.h>

namespace Botan {

secure_vector<uint8_t> PK_Decryptor::decrypt(const uint8_t in[], size_t length) const

   {

   uint8_t valid_mask = 0;

   secure_vector<uint8_t> decoded = do_decrypt(valid_mask, in, length);

   if(valid_mask == 0)

      throw Decoding_Error("Invalid public key ciphertext, cannot decrypt");

   return decoded;

   }

secure_vector<uint8_t>

PK_Decryptor::decrypt_or_random(const uint8_t in[],

                                size_t length,

                                size_t expected_pt_len,

                                RandomNumberGenerator& rng,

                                const uint8_t required_content_bytes[],

                                const uint8_t required_content_offsets[],

                                size_t required_contents_length) const

   {

   const secure_vector<uint8_t> fake_pms = rng.random_vec(expected_pt_len);

   uint8_t decrypt_valid = 0;

   secure_vector<uint8_t> decoded = do_decrypt(decrypt_valid, in, length);

   auto valid_mask = CT::Mask<uint8_t>::is_equal(decrypt_valid, 0xFF);

   valid_mask &= CT::Mask<uint8_t>(CT::Mask<size_t>::is_zero(decoded.size() ^ expected_pt_len));

   decoded.resize(expected_pt_len);

   for(size_t i = 0; i != required_contents_length; ++i)

      {

      /*

      These values are chosen by the application and for TLS are constants,

      so this early failure via assert is fine since we know 0,1 < 48

      If there is a protocol that has content checks on the key where

      the expected offsets are controllable by the attacker this could

      still leak.

      Alternately could always reduce the offset modulo the length?

      */

      const uint8_t exp = required_content_bytes[i];

      const uint8_t off = required_content_offsets[i];

      BOTAN_ASSERT(off < expected_pt_len, "Offset in range of plaintext");

      auto eq = CT::Mask<uint8_t>::is_equal(decoded[off], exp);

      valid_mask &= eq;

      }

   // If valid_mask is false, assign fake pre master instead

   valid_mask.select_n(decoded.data(), decoded.data(), fake_pms.data(), expected_pt_len);

   return decoded;

   }

secure_vector<uint8_t>

PK_Decryptor::decrypt_or_random(const uint8_t in[],

                                size_t length,

                                size_t expected_pt_len,

                                RandomNumberGenerator& rng) const

   {

   return decrypt_or_random(in, length, expected_pt_len, rng,

                            nullptr, nullptr, 0);

   }

PK_Encryptor_EME::PK_Encryptor_EME(const Public_Key& key,

                                   RandomNumberGenerator& rng,

                                   const std::string& padding,

                                   const std::string& provider)

   {

   m_op = key.create_encryption_op(rng, padding, provider);

   if(!m_op)

      throw Invalid_Argument("Key type " + key.algo_name() + " does not support encryption");

   }

PK_Encryptor_EME::~PK_Encryptor_EME() = default;

size_t PK_Encryptor_EME::ciphertext_length(size_t ptext_len) const

   {

   return m_op->ciphertext_length(ptext_len);

   }

std::vector<uint8_t>

PK_Encryptor_EME::enc(const uint8_t in[], size_t length, RandomNumberGenerator& rng) const

   {

   return unlock(m_op->encrypt(in, length, rng));

   }

size_t PK_Encryptor_EME::maximum_input_size() const

   {

   return m_op->max_input_bits() / 8;

   }

PK_Decryptor_EME::PK_Decryptor_EME(const Private_Key& key,

                                   RandomNumberGenerator& rng,

                                   const std::string& padding,

                                   const std::string& provider)

   {

   m_op = key.create_decryption_op(rng, padding, provider);

   if(!m_op)

      throw Invalid_Argument("Key type " + key.algo_name() + " does not support decryption");

   }

PK_Decryptor_EME::~PK_Decryptor_EME() = default;

size_t PK_Decryptor_EME::plaintext_length(size_t ctext_len) const

   {

   return m_op->plaintext_length(ctext_len);

   }

secure_vector<uint8_t> PK_Decryptor_EME::do_decrypt(uint8_t& valid_mask,

                                                 const uint8_t in[], size_t in_len) const

   {

   return m_op->decrypt(valid_mask, in, in_len);

   }

PK_KEM_Encryptor::PK_KEM_Encryptor(const Public_Key& key,

                                   RandomNumberGenerator& rng,

                                   const std::string& param,

                                   const std::string& provider)

   {

   m_op = key.create_kem_encryption_op(rng, param, provider);

   if(!m_op)

      throw Invalid_Argument("Key type " + key.algo_name() + " does not support KEM encryption");

   }

PK_KEM_Encryptor::~PK_KEM_Encryptor() = default;

void PK_KEM_Encryptor::encrypt(secure_vector<uint8_t>& out_encapsulated_key,

                               secure_vector<uint8_t>& out_shared_key,

                               size_t desired_shared_key_len,

                               RandomNumberGenerator& rng,

                               const uint8_t salt[],

                               size_t salt_len)

   {

   m_op->kem_encrypt(out_encapsulated_key,

                     out_shared_key,

                     desired_shared_key_len,

                     rng,

                     salt,

                     salt_len);

   }

PK_KEM_Decryptor::PK_KEM_Decryptor(const Private_Key& key,

                                   RandomNumberGenerator& rng,

                                   const std::string& param,

                                   const std::string& provider)

   {

   m_op = key.create_kem_decryption_op(rng, param, provider);

   if(!m_op)

      throw Invalid_Argument("Key type " + key.algo_name() + " does not support KEM decryption");

   }

PK_KEM_Decryptor::~PK_KEM_Decryptor() = default;

secure_vector<uint8_t> PK_KEM_Decryptor::decrypt(const uint8_t encap_key[],

                                              size_t encap_key_len,

                                              size_t desired_shared_key_len,

                                              const uint8_t salt[],

                                              size_t salt_len)

   {

   return m_op->kem_decrypt(encap_key, encap_key_len,

                            desired_shared_key_len,

                            salt, salt_len);

   }

PK_Key_Agreement::PK_Key_Agreement(PK_Key_Agreement&&) noexcept = default;

PK_Key_Agreement::PK_Key_Agreement(const Private_Key& key,

                                   RandomNumberGenerator& rng,

                                   const std::string& kdf,

                                   const std::string& provider)

   {

   m_op = key.create_key_agreement_op(rng, kdf, provider);

   if(!m_op)

      throw Invalid_Argument("Key type " + key.algo_name() + " does not support key agreement");

   }

PK_Key_Agreement::~PK_Key_Agreement() = default;

size_t PK_Key_Agreement::agreed_value_size() const

   {

   return m_op->agreed_value_size();

   }

SymmetricKey PK_Key_Agreement::derive_key(size_t key_len,

                                          const uint8_t in[], size_t in_len,

                                          const uint8_t salt[],

                                          size_t salt_len) const

   {

   return m_op->agree(key_len, in, in_len, salt, salt_len);

   }

static void check_der_format_supported(Signature_Format format, size_t parts)

   {

      if(format != Signature_Format::Standard && parts == 1)

         throw Invalid_Argument("PK: This algorithm does not support DER encoding");

   }

PK_Signer::PK_Signer(const Private_Key& key,

                     RandomNumberGenerator& rng,

                     const std::string& emsa,

                     Signature_Format format,

                     const std::string& provider)

   {

   m_op = key.create_signature_op(rng, emsa, provider);

   if(!m_op)

      throw Invalid_Argument("Key type " + key.algo_name() + " does not support signature generation");

   m_sig_format = format;

   m_parts = key.message_parts();

   m_part_size = key.message_part_size();

   check_der_format_supported(format, m_parts);

   }

PK_Signer::~PK_Signer() = default;

void PK_Signer::update(const uint8_t in[], size_t length)

   {

   m_op->update(in, length);

   }

namespace {

std::vector<uint8_t> der_encode_signature(const std::vector<uint8_t>& sig,

                                          size_t parts,

                                          size_t part_size)

   {

   if(sig.size() % parts != 0 || sig.size() != parts * part_size)

      throw Encoding_Error("Unexpected size for DER signature");

   std::vector<BigInt> sig_parts(parts);

   for(size_t i = 0; i != sig_parts.size(); ++i)

      sig_parts[i].binary_decode(&sig[part_size*i], part_size);

   std::vector<uint8_t> output;

   DER_Encoder(output)

      .start_sequence()

      .encode_list(sig_parts)

      .end_cons();

   return output;

   }

}

size_t PK_Signer::signature_length() const

   {

   if(m_sig_format == Signature_Format::Standard)

      {

      return m_op->signature_length();

      }

   else if(m_sig_format == Signature_Format::DerSequence)

      {

      // This is a large over-estimate but its easier than computing

      // the exact value

      return m_op->signature_length() + (8 + 4*m_parts);

      }

   else

      throw Internal_Error("PK_Signer: Invalid signature format enum");

   }

std::vector<uint8_t> PK_Signer::signature(RandomNumberGenerator& rng)

   {

   std::vector<uint8_t> sig = unlock(m_op->sign(rng));

   if(m_sig_format == Signature_Format::Standard)

      {

      return sig;

      }

   else if(m_sig_format == Signature_Format::DerSequence)

      {

      return der_encode_signature(sig, m_parts, m_part_size);

      }

   else

      throw Internal_Error("PK_Signer: Invalid signature format enum");

   }

PK_Verifier::PK_Verifier(const Public_Key& key,

                         const std::string& emsa,

                         Signature_Format format,

                         const std::string& provider)

   {

   m_op = key.create_verification_op(emsa, provider);

   if(!m_op)

      throw Invalid_Argument("Key type " + key.algo_name() + " does not support signature verification");

   m_sig_format = format;

   m_parts = key.message_parts();

   m_part_size = key.message_part_size();

   check_der_format_supported(format, m_parts);

   }

PK_Verifier::~PK_Verifier() = default;

void PK_Verifier::set_input_format(Signature_Format format)

   {

   check_der_format_supported(format, m_parts);

   m_sig_format = format;

   }

bool PK_Verifier::verify_message(const uint8_t msg[], size_t msg_length,

                                 const uint8_t sig[], size_t sig_length)

   {

   update(msg, msg_length);

   return check_signature(sig, sig_length);

   }

void PK_Verifier::update(const uint8_t in[], size_t length)

   {

   m_op->update(in, length);

   }

bool PK_Verifier::check_signature(const uint8_t sig[], size_t length)

   {

   try {

      if(m_sig_format == Signature_Format::Standard)

         {

         return m_op->is_valid_signature(sig, length);

         }

      else if(m_sig_format == Signature_Format::DerSequence)

         {

         std::vector<uint8_t> real_sig;

         BER_Decoder decoder(sig, length);

         BER_Decoder ber_sig = decoder.start_sequence();

         BOTAN_ASSERT_NOMSG(m_parts != 0 && m_part_size != 0);

         size_t count = 0;

         while(ber_sig.more_items())

            {

            BigInt sig_part;

            ber_sig.decode(sig_part);

            real_sig += BigInt::encode_1363(sig_part, m_part_size);

            ++count;

            }

         if(count != m_parts)

            throw Decoding_Error("PK_Verifier: signature size invalid");

         const std::vector<uint8_t> reencoded =

            der_encode_signature(real_sig, m_parts, m_part_size);

         if(reencoded.size() != length ||

            same_mem(reencoded.data(), sig, reencoded.size()) == false)

            {

            throw Decoding_Error("PK_Verifier: signature is not the canonical DER encoding");

            }

         return m_op->is_valid_signature(real_sig.data(), real_sig.size());

         }

      else

         throw Internal_Error("PK_Verifier: Invalid signature format enum");

      }

   catch(Invalid_Argument&) { return false; }

   catch(Decoding_Error&) { return false; }

   catch(Encoding_Error&) { return false; }

   }

}