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/*
* Cipher Modes
* (C) 2013,2016 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_CIPHER_MODE_H__
#define BOTAN_CIPHER_MODE_H__
#include <botan/secmem.h>
#include <botan/key_spec.h>
#include <botan/exceptn.h>
#include <botan/symkey.h>
#include <string>
#include <vector>
namespace Botan {
/**
* Interface for cipher modes
*/
class BOTAN_DLL Cipher_Mode
{
public:
virtual ~Cipher_Mode() {}
/*
* Prepare for processing a message under the specified nonce
*/
virtual void start_msg(const byte nonce[], size_t nonce_len) = 0;
/**
* Begin processing a message.
* @param nonce the per message nonce
*/
template<typename Alloc>
void start(const std::vector<byte, Alloc>& nonce)
{
start_msg(nonce.data(), nonce.size());
}
/**
* Begin processing a message.
* @param nonce the per message nonce
* @param nonce_len length of nonce
*/
void start(const byte nonce[], size_t nonce_len)
{
start_msg(nonce, nonce_len);
}
/**
* Begin processing a message.
*/
void start()
{
return start_msg(nullptr, 0);
}
/**
* Process message blocks
*
* Input must be a multiple of update_granularity
*
* Processes msg in place and returns bytes written. Normally
* this will be either msg_len (indicating the entire message was
* processes) or for certain AEAD modes zero (indicating that the
* mode requires the entire message be processed in one pass).
*
* @param msg the message to be processed
* @param msg_len length of the message in bytes
*/
virtual size_t process(uint8_t msg[], size_t msg_len) = 0;
/**
* Process some data. Input must be in size update_granularity() byte blocks.
* @param buffer in/out parameter which will possibly be resized
* @param offset an offset into blocks to begin processing
*/
void update(secure_vector<byte>& buffer, size_t offset = 0)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset ok");
byte* buf = buffer.data() + offset;
const size_t buf_size = buffer.size() - offset;
const size_t written = process(buf, buf_size);
buffer.resize(offset + written);
}
/**
* Complete processing of a message.
*
* @param final_block in/out parameter which must be at least
* minimum_final_size() bytes, and will be set to any final output
* @param offset an offset into final_block to begin processing
*/
virtual void finish(secure_vector<byte>& final_block, size_t offset = 0) = 0;
/**
* Returns the size of the output if this transform is used to process a
* message with input_length bytes. Will throw if unable to give a precise
* answer.
*/
virtual size_t output_length(size_t input_length) const = 0;
/**
* @return size of required blocks to update
*/
virtual size_t update_granularity() const = 0;
/**
* @return required minimium size to finalize() - may be any
* length larger than this.
*/
virtual size_t minimum_final_size() const = 0;
/**
* @return the default size for a nonce
*/
virtual size_t default_nonce_length() const = 0;
/**
* @return true iff nonce_len is a valid length for the nonce
*/
virtual bool valid_nonce_length(size_t nonce_len) const = 0;
virtual std::string name() const = 0;
virtual void clear() = 0;
/**
* @return true iff this mode provides authentication as well as
* confidentiality.
*/
virtual bool authenticated() const { return false; }
/**
* @return the size of the authentication tag used (in bytes)
*/
virtual size_t tag_size() const { return 0; }
/**
* @return object describing limits on key size
*/
virtual Key_Length_Specification key_spec() const = 0;
/**
* Check whether a given key length is valid for this algorithm.
* @param length the key length to be checked.
* @return true if the key length is valid.
*/
bool valid_keylength(size_t length) const
{
return key_spec().valid_keylength(length);
}
/**
* Set the symmetric key of this transform
* @param key contains the key material
*/
template<typename Alloc>
void set_key(const std::vector<byte, Alloc>& key)
{
set_key(key.data(), key.size());
}
/**
* Set the symmetric key of this transform
* @param key contains the key material
*/
void set_key(const SymmetricKey& key)
{
set_key(key.begin(), key.length());
}
/**
* Set the symmetric key of this transform
* @param key contains the key material
* @param length in bytes of key param
*/
void set_key(const byte key[], size_t length)
{
if(!valid_keylength(length))
throw Invalid_Key_Length(name(), length);
key_schedule(key, length);
}
/**
* @return provider information about this implementation. Default is "base",
* might also return "sse2", "avx2", "openssl", or some other arbitrary string.
*/
virtual std::string provider() const { return "base"; }
private:
virtual void key_schedule(const byte key[], size_t length) = 0;
};
/**
* The two possible directions for cipher filters, determining whether they
* actually perform encryption or decryption.
*/
enum Cipher_Dir { ENCRYPTION, DECRYPTION };
/**
* Get a cipher mode by name (eg "AES-128/CBC" or "Serpent/XTS")
* @param algo_spec cipher name
* @param direction ENCRYPTION or DECRYPTION
*/
BOTAN_DLL Cipher_Mode* get_cipher_mode(const std::string& algo_spec, Cipher_Dir direction);
}
#endif
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