/*
* X.509 Certificate Extensions
* (C) 1999-2010,2012 Jack Lloyd
* (C) 2016 René Korthaus, Rohde & Schwarz Cybersecurity
* (C) 2017 Fabian Weissberg, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/x509_ext.h>
#include <botan/x509cert.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/hash.h>
#include <botan/internal/loadstor.h>
#include <botan/internal/bit_ops.h>
#include <algorithm>
#include <set>
#include <sstream>

namespace Botan {

namespace {

std::unique_ptr<Certificate_Extension>
extension_from_oid(const OID& oid)
   {
   if(oid == Cert_Extension::Subject_Key_ID::static_oid())
      return std::make_unique<Cert_Extension::Subject_Key_ID>();

   if(oid == Cert_Extension::Key_Usage::static_oid())
      return std::make_unique<Cert_Extension::Key_Usage>();

   if(oid == Cert_Extension::Subject_Alternative_Name::static_oid())
      return std::make_unique<Cert_Extension::Subject_Alternative_Name>();

   if(oid == Cert_Extension::Issuer_Alternative_Name::static_oid())
      return std::make_unique<Cert_Extension::Issuer_Alternative_Name>();

   if(oid == Cert_Extension::Basic_Constraints::static_oid())
      return std::make_unique<Cert_Extension::Basic_Constraints>();

   if(oid == Cert_Extension::CRL_Number::static_oid())
      return std::make_unique<Cert_Extension::CRL_Number>();

   if(oid == Cert_Extension::CRL_ReasonCode::static_oid())
      return std::make_unique<Cert_Extension::CRL_ReasonCode>();

   if(oid == Cert_Extension::Authority_Key_ID::static_oid())
      return std::make_unique<Cert_Extension::Authority_Key_ID>();

   if(oid == Cert_Extension::Name_Constraints::static_oid())
      return std::make_unique<Cert_Extension::Name_Constraints>();

   if(oid == Cert_Extension::CRL_Distribution_Points::static_oid())
      return std::make_unique<Cert_Extension::CRL_Distribution_Points>();

   if(oid == Cert_Extension::CRL_Issuing_Distribution_Point::static_oid())
      return std::make_unique<Cert_Extension::CRL_Issuing_Distribution_Point>();

   if(oid == Cert_Extension::Certificate_Policies::static_oid())
      return std::make_unique<Cert_Extension::Certificate_Policies>();

   if(oid == Cert_Extension::Extended_Key_Usage::static_oid())
      return std::make_unique<Cert_Extension::Extended_Key_Usage>();

   if(oid == Cert_Extension::Authority_Information_Access::static_oid())
      return std::make_unique<Cert_Extension::Authority_Information_Access>();

   return nullptr; // unknown
   }

}

/*
* Create a Certificate_Extension object of some kind to handle
*/
std::unique_ptr<Certificate_Extension>
Extensions::create_extn_obj(const OID& oid,
                            bool critical,
                            const std::vector<uint8_t>& body)
   {
   const std::string oid_str = oid.to_string();

   std::unique_ptr<Certificate_Extension> extn = extension_from_oid(oid);

   if(!extn)
      {
      // some other unknown extension type
      extn = std::make_unique<Cert_Extension::Unknown_Extension>(oid, critical);
      }

   try
      {
      extn->decode_inner(body);
      }
   catch(Decoding_Error&)
      {
      extn.reset(new Cert_Extension::Unknown_Extension(oid, critical));
      extn->decode_inner(body);
      }
   return extn;
   }

/*
* Validate the extension (the default implementation is a NOP)
*/
void Certificate_Extension::validate(const X509_Certificate&, const X509_Certificate&,
      const std::vector<X509_Certificate>&,
      std::vector<std::set<Certificate_Status_Code>>&,
      size_t)
   {
   }

/*
* Add a new cert
*/
void Extensions::add(std::unique_ptr<Certificate_Extension> extn, bool critical)
   {
   // sanity check: we don't want to have the same extension more than once
   if(m_extension_info.count(extn->oid_of()) > 0)
      {
      const std::string name = extn->oid_name();
      throw Invalid_Argument("Extension " + name + " already present in Extensions::add");
      }

   const OID oid = extn->oid_of();
   Extensions_Info info(critical, std::move(extn));
   m_extension_oids.push_back(oid);
   m_extension_info.emplace(oid, info);
   }

bool Extensions::add_new(std::unique_ptr<Certificate_Extension> extn, bool critical)
   {
   if(m_extension_info.count(extn->oid_of()) > 0)
      {
      return false; // already exists
      }

   const OID oid = extn->oid_of();
   Extensions_Info info(critical, std::move(extn));
   m_extension_oids.push_back(oid);
   m_extension_info.emplace(oid, info);
   return true;
   }

bool Extensions::remove(const OID& oid)
   {
   const bool erased = m_extension_info.erase(oid) > 0;

   if(erased)
      {
      m_extension_oids.erase(std::find(m_extension_oids.begin(), m_extension_oids.end(), oid));
      }

   return erased;
   }

void Extensions::replace(std::unique_ptr<Certificate_Extension> extn, bool critical)
   {
   // Remove it if it existed
   remove(extn->oid_of());

   const OID oid = extn->oid_of();
   Extensions_Info info(critical, std::move(extn));
   m_extension_oids.push_back(oid);
   m_extension_info.emplace(oid, info);
   }

bool Extensions::extension_set(const OID& oid) const
   {
   return (m_extension_info.find(oid) != m_extension_info.end());
   }

bool Extensions::critical_extension_set(const OID& oid) const
   {
   auto i = m_extension_info.find(oid);
   if(i != m_extension_info.end())
      return i->second.is_critical();
   return false;
   }

std::vector<uint8_t> Extensions::get_extension_bits(const OID& oid) const
   {
   auto i = m_extension_info.find(oid);
   if(i == m_extension_info.end())
      throw Invalid_Argument("Extensions::get_extension_bits no such extension set");

   return i->second.bits();
   }

const Certificate_Extension* Extensions::get_extension_object(const OID& oid) const
   {
   auto extn = m_extension_info.find(oid);
   if(extn == m_extension_info.end())
      return nullptr;

   return &extn->second.obj();
   }

std::unique_ptr<Certificate_Extension> Extensions::get(const OID& oid) const
   {
   if(const Certificate_Extension* ext = this->get_extension_object(oid))
      {
      return ext->copy();
      }
   return nullptr;
   }

std::vector<std::pair<std::unique_ptr<Certificate_Extension>, bool>> Extensions::extensions() const
   {
   std::vector<std::pair<std::unique_ptr<Certificate_Extension>, bool>> exts;
   for(auto&& ext : m_extension_info)
      {
      exts.push_back(
         std::make_pair(
            ext.second.obj().copy(),
            ext.second.is_critical())
         );
      }
   return exts;
   }

std::map<OID, std::pair<std::vector<uint8_t>, bool>> Extensions::extensions_raw() const
   {
   std::map<OID, std::pair<std::vector<uint8_t>, bool>> out;
   for(auto&& ext : m_extension_info)
      {
      out.emplace(ext.first,
                  std::make_pair(ext.second.bits(),
                                 ext.second.is_critical()));
      }
   return out;
   }

/*
* Encode an Extensions list
*/
void Extensions::encode_into(DER_Encoder& to_object) const
   {
   for(auto ext_info : m_extension_info)
      {
      const OID& oid = ext_info.first;
      const bool should_encode = ext_info.second.obj().should_encode();

      if(should_encode)
         {
         const bool is_critical = ext_info.second.is_critical();
         const std::vector<uint8_t>& ext_value = ext_info.second.bits();

         to_object.start_sequence()
               .encode(oid)
               .encode_optional(is_critical, false)
               .encode(ext_value, ASN1_Type::OctetString)
            .end_cons();
         }
      }
   }

/*
* Decode a list of Extensions
*/
void Extensions::decode_from(BER_Decoder& from_source)
   {
   m_extension_oids.clear();
   m_extension_info.clear();

   BER_Decoder sequence = from_source.start_sequence();

   while(sequence.more_items())
      {
      OID oid;
      bool critical;
      std::vector<uint8_t> bits;

      sequence.start_sequence()
         .decode(oid)
         .decode_optional(critical, ASN1_Type::Boolean, ASN1_Class::Universal, false)
         .decode(bits, ASN1_Type::OctetString)
      .end_cons();

      std::unique_ptr<Certificate_Extension> obj = create_extn_obj(oid, critical, bits);
      Extensions_Info info(critical, bits, std::move(obj));

      m_extension_oids.push_back(oid);
      m_extension_info.emplace(oid, info);
      }
   sequence.verify_end();
   }

namespace Cert_Extension {

/*
* Checked accessor for the path_limit member
*/
size_t Basic_Constraints::get_path_limit() const
   {
   if(!m_is_ca)
      throw Invalid_State("Basic_Constraints::get_path_limit: Not a CA");
   return m_path_limit;
   }

/*
* Encode the extension
*/
std::vector<uint8_t> Basic_Constraints::encode_inner() const
   {
   std::vector<uint8_t> output;
   DER_Encoder(output)
      .start_sequence()
      .encode_if(m_is_ca,
                 DER_Encoder()
                    .encode(m_is_ca)
                    .encode_optional(m_path_limit, NO_CERT_PATH_LIMIT)
         )
      .end_cons();
   return output;
   }

/*
* Decode the extension
*/
void Basic_Constraints::decode_inner(const std::vector<uint8_t>& in)
   {
   BER_Decoder(in)
      .start_sequence()
         .decode_optional(m_is_ca, ASN1_Type::Boolean, ASN1_Class::Universal, false)
         .decode_optional(m_path_limit, ASN1_Type::Integer, ASN1_Class::Universal, NO_CERT_PATH_LIMIT)
      .end_cons();

   if(m_is_ca == false)
      m_path_limit = 0;
   }

/*
* Encode the extension
*/
std::vector<uint8_t> Key_Usage::encode_inner() const
   {
   if(m_constraints == NO_CONSTRAINTS)
      throw Encoding_Error("Cannot encode zero usage constraints");

   const size_t unused_bits = ctz(static_cast<uint32_t>(m_constraints));

   std::vector<uint8_t> der;
   der.push_back(static_cast<uint8_t>(ASN1_Type::BitString));
   der.push_back(2 + ((unused_bits < 8) ? 1 : 0));
   der.push_back(unused_bits % 8);
   der.push_back((m_constraints >> 8) & 0xFF);
   if(m_constraints & 0xFF)
      der.push_back(m_constraints & 0xFF);

   return der;
   }

/*
* Decode the extension
*/
void Key_Usage::decode_inner(const std::vector<uint8_t>& in)
   {
   BER_Decoder ber(in);

   BER_Object obj = ber.get_next_object();

   obj.assert_is_a(ASN1_Type::BitString, ASN1_Class::Universal, "usage constraint");

   if(obj.length() != 2 && obj.length() != 3)
      throw BER_Decoding_Error("Bad size for BITSTRING in usage constraint");

   uint16_t usage = 0;

      const uint8_t* bits = obj.bits();

   if(bits[0] >= 8)
      throw BER_Decoding_Error("Invalid unused bits in usage constraint");

   const uint8_t mask = static_cast<uint8_t>(0xFF << bits[0]);

   if(obj.length() == 2)
      {
      usage = make_uint16(bits[1] & mask, 0);
      }
   else if(obj.length() == 3)
      {
      usage = make_uint16(bits[1], bits[2] & mask);
      }

   m_constraints = Key_Constraints(usage);
   }

/*
* Encode the extension
*/
std::vector<uint8_t> Subject_Key_ID::encode_inner() const
   {
   std::vector<uint8_t> output;
   DER_Encoder(output).encode(m_key_id, ASN1_Type::OctetString);
   return output;
   }

/*
* Decode the extension
*/
void Subject_Key_ID::decode_inner(const std::vector<uint8_t>& in)
   {
   BER_Decoder(in).decode(m_key_id, ASN1_Type::OctetString).verify_end();
   }

/*
* Subject_Key_ID Constructor
*/
Subject_Key_ID::Subject_Key_ID(const std::vector<uint8_t>& pub_key, const std::string& hash_name)
   {
   std::unique_ptr<HashFunction> hash(HashFunction::create_or_throw(hash_name));

   m_key_id.resize(hash->output_length());

   hash->update(pub_key);
   hash->final(m_key_id.data());

   // Truncate longer hashes, 192 bits here seems plenty
   const size_t max_skid_len = (192 / 8);
   if(m_key_id.size() > max_skid_len)
      m_key_id.resize(max_skid_len);
   }

/*
* Encode the extension
*/
std::vector<uint8_t> Authority_Key_ID::encode_inner() const
   {
   std::vector<uint8_t> output;
   DER_Encoder(output)
      .start_sequence()
         .encode(m_key_id, ASN1_Type::OctetString, ASN1_Type(0), ASN1_Class::ContextSpecific)
      .end_cons();
   return output;
   }

/*
* Decode the extension
*/
void Authority_Key_ID::decode_inner(const std::vector<uint8_t>& in)
   {
   BER_Decoder(in)
      .start_sequence()
      .decode_optional_string(m_key_id, ASN1_Type::OctetString, 0);
   }

/*
* Encode the extension
*/
std::vector<uint8_t> Subject_Alternative_Name::encode_inner() const
   {
   std::vector<uint8_t> output;
   DER_Encoder(output).encode(m_alt_name);
   return output;
   }

/*
* Encode the extension
*/
std::vector<uint8_t> Issuer_Alternative_Name::encode_inner() const
   {
   std::vector<uint8_t> output;
   DER_Encoder(output).encode(m_alt_name);
   return output;
   }

/*
* Decode the extension
*/
void Subject_Alternative_Name::decode_inner(const std::vector<uint8_t>& in)
   {
   BER_Decoder(in).decode(m_alt_name);
   }

/*
* Decode the extension
*/
void Issuer_Alternative_Name::decode_inner(const std::vector<uint8_t>& in)
   {
   BER_Decoder(in).decode(m_alt_name);
   }

/*
* Encode the extension
*/
std::vector<uint8_t> Extended_Key_Usage::encode_inner() const
   {
   std::vector<uint8_t> output;
   DER_Encoder(output)
      .start_sequence()
         .encode_list(m_oids)
      .end_cons();
   return output;
   }

/*
* Decode the extension
*/
void Extended_Key_Usage::decode_inner(const std::vector<uint8_t>& in)
   {
   BER_Decoder(in).decode_list(m_oids);
   }

/*
* Encode the extension
*/
std::vector<uint8_t> Name_Constraints::encode_inner() const
   {
   throw Not_Implemented("Name_Constraints encoding");
   }


/*
* Decode the extension
*/
void Name_Constraints::decode_inner(const std::vector<uint8_t>& in)
   {
   std::vector<GeneralSubtree> permit, exclude;
   BER_Decoder ber(in);
   BER_Decoder ext = ber.start_sequence();
   BER_Object per = ext.get_next_object();

   ext.push_back(per);
   if(per.is_a(0, ASN1_Class::Constructed | ASN1_Class::ContextSpecific))
      {
      ext.decode_list(permit, ASN1_Type(0), ASN1_Class::Constructed | ASN1_Class::ContextSpecific);
      if(permit.empty())
         throw Encoding_Error("Empty Name Contraint list");
      }

   BER_Object exc = ext.get_next_object();
   ext.push_back(exc);
   if(per.is_a(1, ASN1_Class::Constructed | ASN1_Class::ContextSpecific))
      {
      ext.decode_list(exclude, ASN1_Type(1), ASN1_Class::Constructed | ASN1_Class::ContextSpecific);
      if(exclude.empty())
         throw Encoding_Error("Empty Name Contraint list");
      }

   ext.end_cons();

   if(permit.empty() && exclude.empty())
      throw Encoding_Error("Empty Name Contraint extension");

   m_name_constraints = NameConstraints(std::move(permit),std::move(exclude));
   }

void Name_Constraints::validate(const X509_Certificate& subject, const X509_Certificate& issuer,
      const std::vector<X509_Certificate>& cert_path,
      std::vector<std::set<Certificate_Status_Code>>& cert_status,
      size_t pos)
   {
   if(!m_name_constraints.permitted().empty() || !m_name_constraints.excluded().empty())
      {
      if(!subject.is_CA_cert())
         {
         cert_status.at(pos).insert(Certificate_Status_Code::NAME_CONSTRAINT_ERROR);
         }

      const bool issuer_name_constraint_critical =
         issuer.is_critical("X509v3.NameConstraints");

      // Check that all subordinate certs pass the name constraint
      for(size_t j = 0; j < pos; ++j)
         {
         bool permitted = m_name_constraints.permitted().empty();
         bool failed = false;

         for(auto c: m_name_constraints.permitted())
            {
            switch(c.base().matches(cert_path.at(j)))
               {
               case GeneralName::MatchResult::NotFound:
               case GeneralName::MatchResult::All:
                  permitted = true;
                  break;
               case GeneralName::MatchResult::UnknownType:
                  failed = issuer_name_constraint_critical;
                  permitted = true;
                  break;
               default:
                  break;
               }
            }

         for(auto c: m_name_constraints.excluded())
            {
            switch(c.base().matches(cert_path.at(j)))
               {
               case GeneralName::MatchResult::All:
               case GeneralName::MatchResult::Some:
                  failed = true;
                  break;
               case GeneralName::MatchResult::UnknownType:
                  failed = issuer_name_constraint_critical;
                  break;
               default:
                  break;
               }
            }

         if(failed || !permitted)
            {
            cert_status.at(j).insert(Certificate_Status_Code::NAME_CONSTRAINT_ERROR);
            }
         }
      }
   }

namespace {

/*
* A policy specifier
*/
class Policy_Information final : public ASN1_Object
   {
   public:
      Policy_Information() = default;
      explicit Policy_Information(const OID& oid) : m_oid(oid) {}

      const OID& oid() const { return m_oid; }

      void encode_into(DER_Encoder& codec) const override
         {
         codec.start_sequence()
            .encode(m_oid)
            .end_cons();
         }

      void decode_from(BER_Decoder& codec) override
         {
         codec.start_sequence()
            .decode(m_oid)
            .discard_remaining()
            .end_cons();
         }

   private:
      OID m_oid;
   };

}

/*
* Encode the extension
*/
std::vector<uint8_t> Certificate_Policies::encode_inner() const
   {
   std::vector<Policy_Information> policies;

   for(size_t i = 0; i != m_oids.size(); ++i)
      policies.push_back(Policy_Information(m_oids[i]));

   std::vector<uint8_t> output;
   DER_Encoder(output)
      .start_sequence()
         .encode_list(policies)
      .end_cons();
   return output;
   }

/*
* Decode the extension
*/
void Certificate_Policies::decode_inner(const std::vector<uint8_t>& in)
   {
   std::vector<Policy_Information> policies;

   BER_Decoder(in).decode_list(policies);
   m_oids.clear();
   for(size_t i = 0; i != policies.size(); ++i)
      m_oids.push_back(policies[i].oid());
   }

void Certificate_Policies::validate(
   const X509_Certificate& /*subject*/,
   const X509_Certificate& /*issuer*/,
   const std::vector<X509_Certificate>& /*cert_path*/,
   std::vector<std::set<Certificate_Status_Code>>& cert_status,
   size_t pos)
   {
   std::set<OID> oid_set(m_oids.begin(), m_oids.end());
   if(oid_set.size() != m_oids.size())
      {
      cert_status.at(pos).insert(Certificate_Status_Code::DUPLICATE_CERT_POLICY);
      }
   }

std::vector<uint8_t> Authority_Information_Access::encode_inner() const
   {
   ASN1_String url(m_ocsp_responder, ASN1_Type::Ia5String);

   std::vector<uint8_t> output;
   DER_Encoder(output)
      .start_sequence()
      .start_sequence()
      .encode(OID::from_string("PKIX.OCSP"))
      .add_object(ASN1_Type(6), ASN1_Class::ContextSpecific, url.value())
      .end_cons()
      .end_cons();
   return output;
   }

void Authority_Information_Access::decode_inner(const std::vector<uint8_t>& in)
   {
   BER_Decoder ber = BER_Decoder(in).start_sequence();

   while(ber.more_items())
      {
      OID oid;

      BER_Decoder info = ber.start_sequence();

      info.decode(oid);

      if(oid == OID::from_string("PKIX.OCSP"))
         {
         BER_Object name = info.get_next_object();

         if(name.is_a(6, ASN1_Class::ContextSpecific))
            {
            m_ocsp_responder = ASN1::to_string(name);
            }

         }
      if(oid == OID::from_string("PKIX.CertificateAuthorityIssuers"))
         {
         BER_Object name = info.get_next_object();

         if(name.is_a(6, ASN1_Class::ContextSpecific))
            {
            m_ca_issuers.push_back(ASN1::to_string(name));
            }
         }
      }
   }

/*
* Checked accessor for the crl_number member
*/
size_t CRL_Number::get_crl_number() const
   {
   if(!m_has_value)
      throw Invalid_State("CRL_Number::get_crl_number: Not set");
   return m_crl_number;
   }

/*
* Copy a CRL_Number extension
*/
std::unique_ptr<Certificate_Extension> CRL_Number::copy() const
   {
   if(!m_has_value)
      throw Invalid_State("CRL_Number::copy: Not set");
   return std::make_unique<CRL_Number>(m_crl_number);
   }

/*
* Encode the extension
*/
std::vector<uint8_t> CRL_Number::encode_inner() const
   {
   std::vector<uint8_t> output;
   DER_Encoder(output).encode(m_crl_number);
   return output;
   }

/*
* Decode the extension
*/
void CRL_Number::decode_inner(const std::vector<uint8_t>& in)
   {
   BER_Decoder(in).decode(m_crl_number);
   m_has_value = true;
   }

/*
* Encode the extension
*/
std::vector<uint8_t> CRL_ReasonCode::encode_inner() const
   {
   std::vector<uint8_t> output;
   DER_Encoder(output).encode(static_cast<size_t>(m_reason), ASN1_Type::Enumerated, ASN1_Class::Universal);
   return output;
   }

/*
* Decode the extension
*/
void CRL_ReasonCode::decode_inner(const std::vector<uint8_t>& in)
   {
   size_t reason_code = 0;
   BER_Decoder(in).decode(reason_code, ASN1_Type::Enumerated, ASN1_Class::Universal);
   m_reason = static_cast<CRL_Code>(reason_code);
   }

std::vector<uint8_t> CRL_Distribution_Points::encode_inner() const
   {
   throw Not_Implemented("CRL_Distribution_Points encoding");
   }

void CRL_Distribution_Points::decode_inner(const std::vector<uint8_t>& buf)
   {
   BER_Decoder(buf)
      .decode_list(m_distribution_points)
      .verify_end();

   std::stringstream ss;

   for(size_t i = 0; i != m_distribution_points.size(); ++i)
      {
      auto contents = m_distribution_points[i].point().contents();

      for(const auto& pair : contents)
         {
         ss << pair.first << ": " << pair.second << " ";
         }
      }

   m_crl_distribution_urls.push_back(ss.str());
   }

void CRL_Distribution_Points::Distribution_Point::encode_into(class DER_Encoder&) const
   {
   throw Not_Implemented("CRL_Distribution_Points encoding");
   }

void CRL_Distribution_Points::Distribution_Point::decode_from(class BER_Decoder& ber)
   {
   ber.start_sequence()
      .start_context_specific(0)
        .decode_optional_implicit(m_point, ASN1_Type(0),
                                  ASN1_Class::ContextSpecific | ASN1_Class::Constructed,
                                  ASN1_Type::Sequence, ASN1_Class::Constructed)
      .end_cons().end_cons();
   }

std::vector<uint8_t> CRL_Issuing_Distribution_Point::encode_inner() const
   {
   throw Not_Implemented("CRL_Issuing_Distribution_Point encoding");
   }

void CRL_Issuing_Distribution_Point::decode_inner(const std::vector<uint8_t>& buf)
   {
   BER_Decoder(buf).decode(m_distribution_point).verify_end();
   }

std::vector<uint8_t> Unknown_Extension::encode_inner() const
   {
   return m_bytes;
   }

void Unknown_Extension::decode_inner(const std::vector<uint8_t>& bytes)
   {
   // Just treat as an opaque blob at this level
   m_bytes = bytes;
   }

}

}