tls_reader.h

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/*
* TLS Data Reader
* (C) 2010-2011,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#ifndef BOTAN_TLS_READER_H_
#define BOTAN_TLS_READER_H_
 
#include <botan/exceptn.h>
#include <botan/secmem.h>
#include <botan/internal/loadstor.h>
#include <botan/internal/fmt.h>
#include <string>
#include <vector>
#include <span>
 
namespace Botan {
 
namespace TLS {
 
/**
* Helper class for decoding TLS protocol messages
*/
class TLS_Data_Reader final
   {
   public:
      TLS_Data_Reader(const char* type, std::span<const uint8_t> buf_in) :
         m_typename(type), m_buf(buf_in), m_offset(0) {}
 
      void assert_done() const
         {
         if(has_remaining())
            throw_decode_error("Extra bytes at end of message");
         }
 
      size_t read_so_far() const { return m_offset; }
 
      size_t remaining_bytes() const { return m_buf.size() - m_offset; }
 
      bool has_remaining() const { return (remaining_bytes() > 0); }
 
      std::vector<uint8_t> get_remaining()
         {
         return std::vector<uint8_t>(m_buf.begin() + m_offset, m_buf.end());
         }
 
      std::vector<uint8_t> get_data_read_so_far()
         {
         return std::vector<uint8_t>(m_buf.begin(), m_buf.begin() + m_offset);
         }
 
      void discard_next(size_t bytes)
         {
         assert_at_least(bytes);
         m_offset += bytes;
         }
 
      uint32_t get_uint32_t()
         {
         assert_at_least(4);
         uint32_t result = make_uint32(m_buf[m_offset  ], m_buf[m_offset+1],
                                     m_buf[m_offset+2], m_buf[m_offset+3]);
         m_offset += 4;
         return result;
         }
 
      uint32_t get_uint24_t()
         {
         assert_at_least(3);
         uint32_t result = make_uint32(0,                 m_buf[m_offset],
                                       m_buf[m_offset+1], m_buf[m_offset+2]);
         m_offset += 3;
         return result;
         }
 
      uint16_t get_uint16_t()
         {
         assert_at_least(2);
         uint16_t result = make_uint16(m_buf[m_offset], m_buf[m_offset+1]);
         m_offset += 2;
         return result;
         }
 
      uint16_t peek_uint16_t() const
         {
         assert_at_least(2);
         return make_uint16(m_buf[m_offset], m_buf[m_offset+1]);
         }
 
      uint8_t get_byte()
         {
         assert_at_least(1);
         uint8_t result = m_buf[m_offset];
         m_offset += 1;
         return result;
         }
 
      template<typename T, typename Container>
      Container get_elem(size_t num_elems)
         {
         assert_at_least(num_elems * sizeof(T));
 
         Container result(num_elems);
 
         for(size_t i = 0; i != num_elems; ++i)
            result[i] = load_be<T>(&m_buf[m_offset], i);
 
         m_offset += num_elems * sizeof(T);
 
         return result;
         }
 
      std::vector<uint8_t> get_tls_length_value(size_t len_bytes)
         {
         return get_fixed<uint8_t>(get_length_field(len_bytes));
         }
 
      template<typename T>
      std::vector<T> get_range(size_t len_bytes,
                               size_t min_elems,
                               size_t max_elems)
         {
         const size_t num_elems =
            get_num_elems(len_bytes, sizeof(T), min_elems, max_elems);
 
         return get_elem<T, std::vector<T>>(num_elems);
         }
 
      template<typename T>
      std::vector<T> get_range_vector(size_t len_bytes,
                                      size_t min_elems,
                                      size_t max_elems)
         {
         const size_t num_elems =
            get_num_elems(len_bytes, sizeof(T), min_elems, max_elems);
 
         return get_elem<T, std::vector<T>>(num_elems);
         }
 
      std::string get_string(size_t len_bytes,
                             size_t min_bytes,
                             size_t max_bytes)
         {
         std::vector<uint8_t> v =
            get_range_vector<uint8_t>(len_bytes, min_bytes, max_bytes);
 
         return std::string(cast_uint8_ptr_to_char(v.data()), v.size());
         }
 
      template<typename T>
      std::vector<T> get_fixed(size_t size)
         {
         return get_elem<T, std::vector<T>>(size);
         }
 
   private:
      size_t get_length_field(size_t len_bytes)
         {
         assert_at_least(len_bytes);
 
         if(len_bytes == 1)
            return get_byte();
         else if(len_bytes == 2)
            return get_uint16_t();
         else if(len_bytes == 3)
            return get_uint24_t();
 
         throw_decode_error("Bad length size");
         }
 
      size_t get_num_elems(size_t len_bytes,
                           size_t T_size,
                           size_t min_elems,
                           size_t max_elems)
         {
         const size_t byte_length = get_length_field(len_bytes);
 
         if(byte_length % T_size != 0)
            throw_decode_error("Size isn't multiple of T");
 
         const size_t num_elems = byte_length / T_size;
 
         if(num_elems < min_elems || num_elems > max_elems)
            throw_decode_error("Length field outside parameters");
 
         return num_elems;
         }
 
      void assert_at_least(size_t n) const
         {
         if(m_buf.size() - m_offset < n)
            throw_decode_error("Expected " + std::to_string(n) +
                               " bytes remaining, only " +
                               std::to_string(m_buf.size()-m_offset) +
                               " left");
         }
 
      [[noreturn]] void throw_decode_error(std::string_view why) const
         {
         throw Decoding_Error(fmt("Invalid {}: {}", m_typename, why));
         }
 
      const char* m_typename;
      std::span<const uint8_t> m_buf;
      size_t m_offset;
   };
 
/**
* Helper function for encoding length-tagged vectors
*/
template<typename T, typename Alloc>
void append_tls_length_value(std::vector<uint8_t, Alloc>& buf,
                             const T* vals,
                             size_t vals_size,
                             size_t tag_size)
   {
   const size_t T_size = sizeof(T);
   const size_t val_bytes = T_size * vals_size;
 
   if(tag_size != 1 && tag_size != 2 && tag_size != 3)
      throw Invalid_Argument("append_tls_length_value: invalid tag size");
 
   if((tag_size == 1 && val_bytes > 255) ||
      (tag_size == 2 && val_bytes > 65535) ||
      (tag_size == 3 && val_bytes > 16777215))
      throw Invalid_Argument("append_tls_length_value: value too large");
 
   for(size_t i = 0; i != tag_size; ++i)
      buf.push_back(get_byte_var(sizeof(val_bytes)-tag_size+i, val_bytes));
 
   for(size_t i = 0; i != vals_size; ++i)
      for(size_t j = 0; j != T_size; ++j)
         buf.push_back(get_byte_var(j, vals[i]));
   }
 
template<typename T, typename Alloc, typename Alloc2>
void append_tls_length_value(std::vector<uint8_t, Alloc>& buf,
                             const std::vector<T, Alloc2>& vals,
                             size_t tag_size)
   {
   append_tls_length_value(buf, vals.data(), vals.size(), tag_size);
   }
 
template<typename Alloc>
void append_tls_length_value(std::vector<uint8_t, Alloc>& buf,
                             std::string_view str,
                             size_t tag_size)
   {
   append_tls_length_value(buf,
                           cast_char_ptr_to_uint8(str.data()),
                           str.size(),
                           tag_size);
   }
 
}
 
}
 
#endif