pubkey.cpp

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/*
* (C) 1999-2010,2015,2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/pubkey.h>
 
#include <botan/ber_dec.h>
#include <botan/bigint.h>
#include <botan/der_enc.h>
#include <botan/rng.h>
#include <botan/internal/ct_utils.h>
#include <botan/internal/fmt.h>
#include <botan/internal/parsing.h>
#include <botan/internal/pk_ops.h>
#include <botan/internal/pss_params.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,
                                   std::string_view padding,
                                   std::string_view provider) {
   m_op = key.create_encryption_op(rng, padding, provider);
   if(!m_op) {
      throw Invalid_Argument(fmt("Key type {} does not support encryption", key.algo_name()));
   }
}
 
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,
                                   std::string_view padding,
                                   std::string_view provider) {
   m_op = key.create_decryption_op(rng, padding, provider);
   if(!m_op) {
      throw Invalid_Argument(fmt("Key type {} does not support decryption", key.algo_name()));
   }
}
 
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, std::string_view param, std::string_view provider) {
   m_op = key.create_kem_encryption_op(param, provider);
   if(!m_op) {
      throw Invalid_Argument(fmt("Key type {} does not support KEM encryption"));
   }
}
 
PK_KEM_Encryptor::~PK_KEM_Encryptor() = default;
 
size_t PK_KEM_Encryptor::shared_key_length(size_t desired_shared_key_len) const {
   return m_op->shared_key_length(desired_shared_key_len);
}
 
size_t PK_KEM_Encryptor::encapsulated_key_length() const {
   return m_op->encapsulated_key_length();
}
 
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);
}
 
size_t PK_KEM_Decryptor::shared_key_length(size_t desired_shared_key_len) const {
   return m_op->shared_key_length(desired_shared_key_len);
}
 
PK_KEM_Decryptor::PK_KEM_Decryptor(const Private_Key& key,
                                   RandomNumberGenerator& rng,
                                   std::string_view param,
                                   std::string_view provider) {
   m_op = key.create_kem_decryption_op(rng, param, provider);
   if(!m_op) {
      throw Invalid_Argument(fmt("Key type {} does not support KEM decryption", key.algo_name()));
   }
}
 
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,
                                   std::string_view kdf,
                                   std::string_view provider) {
   m_op = key.create_key_agreement_op(rng, kdf, provider);
   if(!m_op) {
      throw Invalid_Argument(fmt("Key type {} does not support key agreement", key.algo_name()));
   }
}
 
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 SymmetricKey(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("This algorithm does not support DER encoding");
   }
}
 
PK_Signer::PK_Signer(const Private_Key& key,
                     RandomNumberGenerator& rng,
                     std::string_view emsa,
                     Signature_Format format,
                     std::string_view provider) {
   m_op = key.create_signature_op(rng, emsa, provider);
   if(!m_op) {
      throw Invalid_Argument(fmt("Key type {} does not support signature generation", key.algo_name()));
   }
   m_sig_format = format;
   m_parts = key.message_parts();
   m_part_size = key.message_part_size();
   check_der_format_supported(format, m_parts);
}
 
AlgorithmIdentifier PK_Signer::algorithm_identifier() const {
   return m_op->algorithm_identifier();
}
 
std::string PK_Signer::hash_function() const {
   return m_op->hash_function();
}
 
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;
}
 
}  // namespace
 
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,
                         std::string_view emsa,
                         Signature_Format format,
                         std::string_view provider) {
   m_op = key.create_verification_op(emsa, provider);
   if(!m_op) {
      throw Invalid_Argument(fmt("Key type {} does not support signature verification", key.algo_name()));
   }
   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(const Public_Key& key,
                         const AlgorithmIdentifier& signature_algorithm,
                         std::string_view provider) {
   m_op = key.create_x509_verification_op(signature_algorithm, provider);
 
   if(!m_op) {
      throw Invalid_Argument(fmt("Key type {} does not support X.509 signature verification", key.algo_name()));
   }
 
   m_sig_format = key.default_x509_signature_format();
   m_parts = key.message_parts();
   m_part_size = key.message_part_size();
   check_der_format_supported(m_sig_format, m_parts);
}
 
PK_Verifier::~PK_Verifier() = default;
 
std::string PK_Verifier::hash_function() const {
   return m_op->hash_function();
}
 
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);
}
 
namespace {
 
std::vector<uint8_t> decode_der_signature(const uint8_t sig[], size_t length, size_t sig_parts, size_t sig_part_size) {
   std::vector<uint8_t> real_sig;
   BER_Decoder decoder(sig, length);
   BER_Decoder ber_sig = decoder.start_sequence();
 
   BOTAN_ASSERT_NOMSG(sig_parts != 0 && sig_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, sig_part_size);
      ++count;
   }
 
   if(count != sig_parts) {
      throw Decoding_Error("PK_Verifier: signature size invalid");
   }
 
   const std::vector<uint8_t> reencoded = der_encode_signature(real_sig, sig_parts, sig_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 real_sig;
}
 
}  // namespace
 
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) {
         bool decoding_success = false;
         std::vector<uint8_t> real_sig;
 
         try {
            real_sig = decode_der_signature(sig, length, m_parts, m_part_size);
            decoding_success = true;
         } catch(Decoding_Error&) {}
 
         bool accept = m_op->is_valid_signature(real_sig.data(), real_sig.size());
 
         return accept && decoding_success;
      } 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;
   }
}
 
}  // namespace Botan