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/*
* TLS Data Reader
* (C) 2010-2011 Jack Lloyd
*
* Released under the terms of the Botan license
*/
#ifndef BOTAN_TLS_READER_H__
#define BOTAN_TLS_READER_H__
#include <botan/exceptn.h>
#include <botan/secmem.h>
#include <botan/loadstor.h>
#include <string>
#include <vector>
#include <stdexcept>
namespace Botan {
/**
* Helper class for decoding TLS protocol messages
*/
class TLS_Data_Reader
{
public:
TLS_Data_Reader(const MemoryRegion<byte>& buf_in) :
buf(buf_in), offset(0) {}
void assert_done() const
{
if(has_remaining())
throw Decoding_Error("Extra bytes at end of message");
}
size_t remaining_bytes() const
{
return buf.size() - offset;
}
bool has_remaining() const
{
return (remaining_bytes() > 0);
}
void discard_next(size_t bytes)
{
assert_at_least(bytes);
offset += bytes;
}
u16bit get_u16bit()
{
assert_at_least(2);
u16bit result = make_u16bit(buf[offset], buf[offset+1]);
offset += 2;
return result;
}
byte get_byte()
{
assert_at_least(1);
byte result = buf[offset];
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>(&buf[offset], i);
offset += num_elems * sizeof(T);
return result;
}
template<typename T>
SecureVector<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, SecureVector<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<byte> v =
get_range_vector<byte>(len_bytes, min_bytes, max_bytes);
return std::string(reinterpret_cast<char*>(&v[0]), v.size());
}
template<typename T>
SecureVector<T> get_fixed(size_t size)
{
return get_elem<T, SecureVector<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_u16bit();
throw Decoding_Error("TLS_Data_Reader: 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 Decoding_Error("TLS_Data_Reader: 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 Decoding_Error("TLS_Data_Reader: Range outside paramaters");
return num_elems;
}
void assert_at_least(size_t n) const
{
if(buf.size() - offset < n)
{
abort();
throw Decoding_Error("TLS_Data_Reader: Corrupt packet");
}
}
const MemoryRegion<byte>& buf;
size_t offset;
};
/**
* Helper function for encoding length-tagged vectors
*/
template<typename T>
void append_tls_length_value(MemoryRegion<byte>& 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)
throw std::invalid_argument("append_tls_length_value: invalid tag size");
if((tag_size == 1 && val_bytes > 255) ||
(tag_size == 2 && val_bytes > 65535))
throw std::invalid_argument("append_tls_length_value: value too large");
for(size_t i = 0; i != tag_size; ++i)
buf.push_back(get_byte(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(j, vals[i]));
}
template<typename T>
void append_tls_length_value(MemoryRegion<byte>& buf,
const MemoryRegion<T>& vals,
size_t tag_size)
{
append_tls_length_value(buf, &vals[0], vals.size(), tag_size);
}
template<typename T>
void append_tls_length_value(MemoryRegion<byte>& buf,
const std::vector<T>& vals,
size_t tag_size)
{
append_tls_length_value(buf, &vals[0], vals.size(), tag_size);
}
}
#endif
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