/*
* X.509 Certificate Authority
* (C) 1999-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#include <botan/x509_ca.h>
#include <botan/pubkey.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/bigint.h>
#include <botan/parsing.h>
#include <botan/lookup.h>
#include <botan/oids.h>
#include <memory>
#include <set>

namespace Botan {

/*
* Load the certificate and private key
*/
X509_CA::X509_CA(const X509_Certificate& c,
                 const Private_Key& key,
                 const std::string& hash_fn) : cert(c)
   {
   if(!cert.is_CA_cert())
      throw Invalid_Argument("X509_CA: This certificate is not for a CA");

   signer = choose_sig_format(key, hash_fn, ca_sig_algo);
   }

/*
* X509_CA Destructor
*/
X509_CA::~X509_CA()
   {
   delete signer;
   }

/*
* Sign a PKCS #10 certificate request
*/
X509_Certificate X509_CA::sign_request(const PKCS10_Request& req,
                                       RandomNumberGenerator& rng,
                                       const X509_Time& not_before,
                                       const X509_Time& not_after)
   {
   Key_Constraints constraints;
   if(req.is_CA())
      constraints = Key_Constraints(KEY_CERT_SIGN | CRL_SIGN);
   else
      {
      std::unique_ptr<Public_Key> key(req.subject_public_key());
      constraints = X509::find_constraints(*key, req.constraints());
      }

   Extensions extensions;

   extensions.add(
      new Cert_Extension::Basic_Constraints(req.is_CA(), req.path_limit()),
      true);

   extensions.add(new Cert_Extension::Key_Usage(constraints), true);

   extensions.add(new Cert_Extension::Authority_Key_ID(cert.subject_key_id()));
   extensions.add(new Cert_Extension::Subject_Key_ID(req.raw_public_key()));

   extensions.add(
      new Cert_Extension::Subject_Alternative_Name(req.subject_alt_name()));

   extensions.add(
      new Cert_Extension::Extended_Key_Usage(req.ex_constraints()));

   return make_cert(signer, rng, ca_sig_algo,
                    req.raw_public_key(),
                    not_before, not_after,
                    cert.subject_dn(), req.subject_dn(),
                    extensions);
   }

/*
* Create a new certificate
*/
X509_Certificate X509_CA::make_cert(PK_Signer* signer,
                                    RandomNumberGenerator& rng,
                                    const AlgorithmIdentifier& sig_algo,
                                    const MemoryRegion<byte>& pub_key,
                                    const X509_Time& not_before,
                                    const X509_Time& not_after,
                                    const X509_DN& issuer_dn,
                                    const X509_DN& subject_dn,
                                    const Extensions& extensions)
   {
   const u32bit X509_CERT_VERSION = 3;
   const size_t SERIAL_BITS = 128;

   BigInt serial_no(rng, SERIAL_BITS);

   DataSource_Memory source(X509_Object::make_signed(signer, rng, sig_algo,
         DER_Encoder().start_cons(SEQUENCE)
            .start_explicit(0)
               .encode(X509_CERT_VERSION-1)
            .end_explicit()

            .encode(serial_no)

            .encode(sig_algo)
            .encode(issuer_dn)

            .start_cons(SEQUENCE)
               .encode(not_before)
               .encode(not_after)
            .end_cons()

            .encode(subject_dn)
            .raw_bytes(pub_key)

            .start_explicit(3)
               .start_cons(SEQUENCE)
                  .encode(extensions)
                .end_cons()
            .end_explicit()
         .end_cons()
      .get_contents()
   ));

   return X509_Certificate(source);
   }

/*
* Create a new, empty CRL
*/
X509_CRL X509_CA::new_crl(RandomNumberGenerator& rng,
                          u32bit next_update) const
   {
   std::vector<CRL_Entry> empty;
   return make_crl(empty, 1, next_update, rng);
   }

/*
* Update a CRL with new entries
*/
X509_CRL X509_CA::update_crl(const X509_CRL& crl,
                             const std::vector<CRL_Entry>& new_revoked,
                             RandomNumberGenerator& rng,
                             u32bit next_update) const
   {
   std::vector<CRL_Entry> revoked = crl.get_revoked();

   std::copy(new_revoked.begin(), new_revoked.end(),
             std::back_inserter(revoked));

   return make_crl(revoked, crl.crl_number() + 1, next_update, rng);
   }

/*
* Create a CRL
*/
X509_CRL X509_CA::make_crl(const std::vector<CRL_Entry>& revoked,
                           u32bit crl_number, u32bit next_update,
                           RandomNumberGenerator& rng) const
   {
   const u32bit X509_CRL_VERSION = 2;

   if(next_update == 0)
      next_update = timespec_to_u32bit("7d");

   // Totally stupid: ties encoding logic to the return of std::time!!
   auto current_time = std::chrono::system_clock::now();
   auto expire_time = current_time + std::chrono::seconds(next_update);

   Extensions extensions;
   extensions.add(
      new Cert_Extension::Authority_Key_ID(cert.subject_key_id()));
   extensions.add(new Cert_Extension::CRL_Number(crl_number));

   DataSource_Memory source(X509_Object::make_signed(signer, rng, ca_sig_algo,
         DER_Encoder().start_cons(SEQUENCE)
            .encode(X509_CRL_VERSION-1)
            .encode(ca_sig_algo)
            .encode(cert.issuer_dn())
            .encode(X509_Time(current_time))
            .encode(X509_Time(expire_time))
            .encode_if(revoked.size() > 0,
                 DER_Encoder()
                    .start_cons(SEQUENCE)
                       .encode_list(revoked)
                    .end_cons()
               )
            .start_explicit(0)
               .start_cons(SEQUENCE)
                  .encode(extensions)
               .end_cons()
            .end_explicit()
         .end_cons()
      .get_contents()
   ));

   return X509_CRL(source);
   }

/*
* Return the CA's certificate
*/
X509_Certificate X509_CA::ca_certificate() const
   {
   return cert;
   }

/*
* Choose a signing format for the key
*/
PK_Signer* choose_sig_format(const Private_Key& key,
                             const std::string& hash_fn,
                             AlgorithmIdentifier& sig_algo)
   {
   std::string padding;

   const std::string algo_name = key.algo_name();

   const HashFunction* proto_hash = retrieve_hash(hash_fn);
   if(!proto_hash)
      throw Algorithm_Not_Found(hash_fn);

   if(key.max_input_bits() < proto_hash->output_length()*8)
      throw Invalid_Argument("Key is too small for chosen hash function");

   if(algo_name == "RSA")
      padding = "EMSA3";
   else if(algo_name == "DSA")
      padding = "EMSA1";
   else if(algo_name == "ECDSA")
      padding = "EMSA1_BSI";
   else
      throw Invalid_Argument("Unknown X.509 signing key type: " + algo_name);

   Signature_Format format =
      (key.message_parts() > 1) ? DER_SEQUENCE : IEEE_1363;

   padding = padding + '(' + proto_hash->name() + ')';

   sig_algo.oid = OIDS::lookup(algo_name + "/" + padding);
   sig_algo.parameters = key.algorithm_identifier().parameters;

   return new PK_Signer(key, padding, format);
   }

}