/* * DER Encoder * (C) 1999-2007 Jack Lloyd * * Botan is released under the Simplified BSD License (see license.txt) */ #include #include #include #include #include #include namespace Botan { namespace { /* * DER encode an ASN.1 type tag */ secure_vector encode_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)); secure_vector encoded_tag; if(type_tag <= 30) encoded_tag.push_back(static_cast(type_tag | class_tag)); else { size_t blocks = high_bit(type_tag) + 6; blocks = (blocks - (blocks % 7)) / 7; BOTAN_ASSERT(blocks > 0, "Math works"); encoded_tag.push_back(static_cast(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); } return encoded_tag; } /* * DER encode an ASN.1 length field */ secure_vector encode_length(size_t length) { secure_vector encoded_length; if(length <= 127) encoded_length.push_back(static_cast(length)); else { const size_t bytes_needed = significant_bytes(length); encoded_length.push_back(static_cast(0x80 | bytes_needed)); for(size_t i = sizeof(length) - bytes_needed; i < sizeof(length); ++i) encoded_length.push_back(get_byte(i, length)); } return encoded_length; } } /* * Return the encoded SEQUENCE/SET */ secure_vector DER_Encoder::DER_Sequence::get_contents() { 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(); } secure_vector result; result += encode_tag(m_type_tag, real_class_tag); result += encode_length(m_contents.size()); result += m_contents; m_contents.clear(); return result; } /* * 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(data, data + length)); else m_contents += std::make_pair(data, length); } /* * 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 DER_Encoder::get_contents() { if(m_subsequences.size() != 0) throw Invalid_State("DER_Encoder: Sequence hasn't been marked done"); secure_vector output; std::swap(output, m_contents); 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"); secure_vector seq = m_subsequences[m_subsequences.size()-1].get_contents(); m_subsequences.pop_back(); raw_bytes(seq); 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(type_no); if(type_tag == SET) throw Internal_Error("DER_Encoder.start_explicit(SET); cannot perform"); 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 m_contents += std::make_pair(bytes, 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 contents(extra_zero + n.bytes()); BigInt::encode(&contents[extra_zero], n); 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 secure_vector& bytes, ASN1_Tag real_type, ASN1_Tag type_tag, ASN1_Tag class_tag) { return encode(bytes.data(), bytes.size(), real_type, type_tag, class_tag); } /* * DER encode an OCTET STRING or BIT STRING */ DER_Encoder& DER_Encoder::encode(const std::vector& bytes, ASN1_Tag real_type, ASN1_Tag type_tag, ASN1_Tag class_tag) { return encode(bytes.data(), bytes.size(), real_type, type_tag, class_tag); } /* * 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 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); } /* * Conditionally write some values to the stream */ DER_Encoder& DER_Encoder::encode_if(bool cond, DER_Encoder& codec) { if(cond) return raw_bytes(codec.get_contents()); return (*this); } DER_Encoder& DER_Encoder::encode_if(bool cond, const ASN1_Object& obj) { if(cond) encode(obj); return (*this); } /* * Request for an object to encode itself */ 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 uint8_t rep[], size_t length) { secure_vector buffer; buffer += encode_tag(type_tag, class_tag); buffer += encode_length(length); buffer += std::make_pair(rep, length); return raw_bytes(buffer); } /* * 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); } }