/*

* DER Encoder

* (C) 1999-2007,2018 Jack Lloyd

*

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

*/

#include <botan/der_enc.h>

#include <botan/asn1_obj.h>

#include <botan/bigint.h>

#include <botan/loadstor.h>

#include <botan/internal/bit_ops.h>

#include <algorithm>

namespace Botan {

namespace {

/*

* DER encode an ASN.1 type tag

*/

void encode_tag(std::vector<uint8_t>& encoded_tag,

                ASN1_Tag type_tag, ASN1_Tag class_tag)

   {

   if((class_tag | 0xE0) != 0xE0)

      throw Encoding_Error("DER_Encoder: Invalid class tag " +

                           std::to_string(class_tag));

   if(type_tag <= 30)

      {

      encoded_tag.push_back(static_cast<uint8_t>(type_tag | class_tag));

      }

   else

      {

      size_t blocks = high_bit(static_cast<uint32_t>(type_tag)) + 6;

      blocks = (blocks - (blocks % 7)) / 7;

      BOTAN_ASSERT_NOMSG(blocks > 0);

      encoded_tag.push_back(static_cast<uint8_t>(class_tag | 0x1F));

      for(size_t i = 0; i != blocks - 1; ++i)

         encoded_tag.push_back(0x80 | ((type_tag >> 7*(blocks-i-1)) & 0x7F));

      encoded_tag.push_back(type_tag & 0x7F);

      }

   }

/*

* DER encode an ASN.1 length field

*/

void encode_length(std::vector<uint8_t>& encoded_length, size_t length)

   {

   if(length <= 127)

      {

      encoded_length.push_back(static_cast<uint8_t>(length));

      }

   else

      {

      const size_t bytes_needed = significant_bytes(length);

      encoded_length.push_back(static_cast<uint8_t>(0x80 | bytes_needed));

      for(size_t i = sizeof(length) - bytes_needed; i < sizeof(length); ++i)

         encoded_length.push_back(get_byte(i, length));

      }

   }

}

DER_Encoder::DER_Encoder(secure_vector<uint8_t>& vec)

   {

   m_append_output = [&vec](const uint8_t b[], size_t l)

      {

      vec.insert(vec.end(), b, b + l);

      };

   }

DER_Encoder::DER_Encoder(std::vector<uint8_t>& vec)

   {

   m_append_output = [&vec](const uint8_t b[], size_t l)

      {

      vec.insert(vec.end(), b, b + l);

      };

   }

/*

* Push the encoded SEQUENCE/SET to the encoder stream

*/

void DER_Encoder::DER_Sequence::push_contents(DER_Encoder& der)

   {

   const ASN1_Tag real_class_tag = ASN1_Tag(m_class_tag | CONSTRUCTED);

   if(m_type_tag == SET)

      {

      std::sort(m_set_contents.begin(), m_set_contents.end());

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

         m_contents += m_set_contents[i];

      m_set_contents.clear();

      }

   der.add_object(m_type_tag, real_class_tag, m_contents.data(), m_contents.size());

   m_contents.clear();

   }

/*

* Add an encoded value to the SEQUENCE/SET

*/

void DER_Encoder::DER_Sequence::add_bytes(const uint8_t data[], size_t length)

   {

   if(m_type_tag == SET)

      m_set_contents.push_back(secure_vector<uint8_t>(data, data + length));

   else

      m_contents += std::make_pair(data, length);

   }

void DER_Encoder::DER_Sequence::add_bytes(const uint8_t hdr[], size_t hdr_len,

                                          const uint8_t val[], size_t val_len)

   {

   if(m_type_tag == SET)

      {

      secure_vector<uint8_t> m;

      m.reserve(hdr_len + val_len);

      m += std::make_pair(hdr, hdr_len);

      m += std::make_pair(val, val_len);

      m_set_contents.push_back(std::move(m));

      }

   else

      {

      m_contents += std::make_pair(hdr, hdr_len);

      m_contents += std::make_pair(val, val_len);

      }

   }

/*

* Return the type and class taggings

*/

ASN1_Tag DER_Encoder::DER_Sequence::tag_of() const

   {

   return ASN1_Tag(m_type_tag | m_class_tag);

   }

/*

* DER_Sequence Constructor

*/

DER_Encoder::DER_Sequence::DER_Sequence(ASN1_Tag t1, ASN1_Tag t2) :

   m_type_tag(t1), m_class_tag(t2)

   {

   }

/*

* Return the encoded contents

*/

secure_vector<uint8_t> DER_Encoder::get_contents()

   {

   if(m_subsequences.size() != 0)

      throw Invalid_State("DER_Encoder: Sequence hasn't been marked done");

   if(m_append_output)

      throw Invalid_State("DER_Encoder Cannot get contents when using output vector");

   secure_vector<uint8_t> output;

   std::swap(output, m_default_outbuf);

   return output;

   }

std::vector<uint8_t> DER_Encoder::get_contents_unlocked()

   {

   if(m_subsequences.size() != 0)

      throw Invalid_State("DER_Encoder: Sequence hasn't been marked done");

   if(m_append_output)

      throw Invalid_State("DER_Encoder Cannot get contents when using output vector");

   std::vector<uint8_t> output(m_default_outbuf.begin(), m_default_outbuf.end());

   m_default_outbuf.clear();

   return output;

   }

/*

* Start a new ASN.1 SEQUENCE/SET/EXPLICIT

*/

DER_Encoder& DER_Encoder::start_cons(ASN1_Tag type_tag,

                                     ASN1_Tag class_tag)

   {

   m_subsequences.push_back(DER_Sequence(type_tag, class_tag));

   return (*this);

   }

/*

* Finish the current ASN.1 SEQUENCE/SET/EXPLICIT

*/

DER_Encoder& DER_Encoder::end_cons()

   {

   if(m_subsequences.empty())

      throw Invalid_State("DER_Encoder::end_cons: No such sequence");

   DER_Sequence last_seq = std::move(m_subsequences[m_subsequences.size()-1]);

   m_subsequences.pop_back();

   last_seq.push_contents(*this);

   return (*this);

   }

/*

* Start a new ASN.1 EXPLICIT encoding

*/

DER_Encoder& DER_Encoder::start_explicit(uint16_t type_no)

   {

   ASN1_Tag type_tag = static_cast<ASN1_Tag>(type_no);

   // This would confuse DER_Sequence

   if(type_tag == SET)

      throw Internal_Error("DER_Encoder.start_explicit(SET) not supported");

   return start_cons(type_tag, CONTEXT_SPECIFIC);

   }

/*

* Finish the current ASN.1 EXPLICIT encoding

*/

DER_Encoder& DER_Encoder::end_explicit()

   {

   return end_cons();

   }

/*

* Write raw bytes into the stream

*/

DER_Encoder& DER_Encoder::raw_bytes(const uint8_t bytes[], size_t length)

   {

   if(m_subsequences.size())

      {

      m_subsequences[m_subsequences.size()-1].add_bytes(bytes, length);

      }

   else if(m_append_output)

      {

      m_append_output(bytes, length);

      }

   else

      {

      m_default_outbuf += std::make_pair(bytes, length);

      }

   return (*this);

   }

/*

* Write the encoding of the byte(s)

*/

DER_Encoder& DER_Encoder::add_object(ASN1_Tag type_tag, ASN1_Tag class_tag,

                                     const uint8_t rep[], size_t length)

   {

   std::vector<uint8_t> hdr;

   encode_tag(hdr, type_tag, class_tag);

   encode_length(hdr, length);

   if(m_subsequences.size())

      {

      m_subsequences[m_subsequences.size()-1].add_bytes(hdr.data(), hdr.size(), rep, length);

      }

   else if(m_append_output)

      {

      m_append_output(hdr.data(), hdr.size());

      m_append_output(rep, length);

      }

   else

      {

      m_default_outbuf += hdr;

      m_default_outbuf += std::make_pair(rep, length);

      }

   return (*this);

   }

/*

* Encode a NULL object

*/

DER_Encoder& DER_Encoder::encode_null()

   {

   return add_object(NULL_TAG, UNIVERSAL, nullptr, 0);

   }

/*

* DER encode a BOOLEAN

*/

DER_Encoder& DER_Encoder::encode(bool is_true)

   {

   return encode(is_true, BOOLEAN, UNIVERSAL);

   }

/*

* DER encode a small INTEGER

*/

DER_Encoder& DER_Encoder::encode(size_t n)

   {

   return encode(BigInt(n), INTEGER, UNIVERSAL);

   }

/*

* DER encode a small INTEGER

*/

DER_Encoder& DER_Encoder::encode(const BigInt& n)

   {

   return encode(n, INTEGER, UNIVERSAL);

   }

/*

* Encode this object

*/

DER_Encoder& DER_Encoder::encode(const uint8_t bytes[], size_t length,

                                 ASN1_Tag real_type)

   {

   return encode(bytes, length, real_type, real_type, UNIVERSAL);

   }

/*

* DER encode a BOOLEAN

*/

DER_Encoder& DER_Encoder::encode(bool is_true,

                                 ASN1_Tag type_tag, ASN1_Tag class_tag)

   {

   uint8_t val = is_true ? 0xFF : 0x00;

   return add_object(type_tag, class_tag, &val, 1);

   }

/*

* DER encode a small INTEGER

*/

DER_Encoder& DER_Encoder::encode(size_t n,

                                 ASN1_Tag type_tag, ASN1_Tag class_tag)

   {

   return encode(BigInt(n), type_tag, class_tag);

   }

/*

* DER encode an INTEGER

*/

DER_Encoder& DER_Encoder::encode(const BigInt& n,

                                 ASN1_Tag type_tag, ASN1_Tag class_tag)

   {

   if(n == 0)

      return add_object(type_tag, class_tag, 0);

   const size_t extra_zero = (n.bits() % 8 == 0) ? 1 : 0;

   secure_vector<uint8_t> contents(extra_zero + n.bytes());

   n.binary_encode(&contents[extra_zero]);

   if(n < 0)

      {

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

         contents[i] = ~contents[i];

      for(size_t i = contents.size(); i > 0; --i)

         if(++contents[i-1])

            break;

      }

   return add_object(type_tag, class_tag, contents);

   }

/*

* DER encode an OCTET STRING or BIT STRING

*/

DER_Encoder& DER_Encoder::encode(const uint8_t bytes[], size_t length,

                                 ASN1_Tag real_type,

                                 ASN1_Tag type_tag, ASN1_Tag class_tag)

   {

   if(real_type != OCTET_STRING && real_type != BIT_STRING)

      throw Invalid_Argument("DER_Encoder: Invalid tag for byte/bit string");

   if(real_type == BIT_STRING)

      {

      secure_vector<uint8_t> encoded;

      encoded.push_back(0);

      encoded += std::make_pair(bytes, length);

      return add_object(type_tag, class_tag, encoded);

      }

   else

      return add_object(type_tag, class_tag, bytes, length);

   }

DER_Encoder& DER_Encoder::encode(const ASN1_Object& obj)

   {

   obj.encode_into(*this);

   return (*this);

   }

/*

* Write the encoding of the byte(s)

*/

DER_Encoder& DER_Encoder::add_object(ASN1_Tag type_tag, ASN1_Tag class_tag,

                                     const std::string& rep_str)

   {

   const uint8_t* rep = cast_char_ptr_to_uint8(rep_str.data());

   const size_t rep_len = rep_str.size();

   return add_object(type_tag, class_tag, rep, rep_len);

   }

/*

* Write the encoding of the byte

*/

DER_Encoder& DER_Encoder::add_object(ASN1_Tag type_tag,

                                     ASN1_Tag class_tag, uint8_t rep)

   {

   return add_object(type_tag, class_tag, &rep, 1);

   }

}