Botan::CFB_Mode Class Reference

#include <cfb.h>

Inheritance diagram for Botan::CFB_Mode:

Public Member Functions
virtual bool	authenticated () const
void	clear () override final
size_t	default_nonce_length () const override final
virtual void	finish (secure_vector< uint8_t > &final_block, size_t offset=0)=0
Key_Length_Specification	key_spec () const override final
size_t	minimum_final_size () const override final
std::string	name () const override final
size_t	output_length (size_t input_length) const override final
virtual size_t	process (uint8_t msg[], size_t msg_len)=0
virtual std::string	provider () const
void	reset () override final
template<typename Alloc >
void	set_key (const std::vector< uint8_t, Alloc > &key)
void	set_key (const SymmetricKey &key)
void	set_key (const uint8_t key[], size_t length)
template<typename Alloc >
void	start (const std::vector< uint8_t, Alloc > &nonce)
void	start (const uint8_t nonce[], size_t nonce_len)
void	start ()
virtual size_t	tag_size () const
void	update (secure_vector< uint8_t > &buffer, size_t offset=0)
size_t	update_granularity () const override final
bool	valid_keylength (size_t length) const
bool	valid_nonce_length (size_t n) const override final

Static Public Member Functions
static std::unique_ptr< Cipher_Mode >	create (const std::string &algo, Cipher_Dir direction, const std::string &provider="")
static std::unique_ptr< Cipher_Mode >	create_or_throw (const std::string &algo, Cipher_Dir direction, const std::string &provider="")
static std::vector< std::string >	providers (const std::string &algo_spec)

Protected Member Functions
size_t	block_size () const
	CFB_Mode (BlockCipher *cipher, size_t feedback_bits)
const BlockCipher &	cipher () const
size_t	feedback () const
void	shift_register ()

Protected Attributes
secure_vector< uint8_t >	m_keystream
size_t	m_keystream_pos = 0
secure_vector< uint8_t >	m_state

Detailed Description

CFB Mode

Definition at line 20 of file cfb.h.

Constructor & Destructor Documentation

CFB_Mode()

Botan::CFB_Mode::CFB_Mode ( BlockCipher *  cipher, size_t  feedback_bits  )

protected

Definition at line 13 of file cfb.cpp.

                                                            :
   m_cipher(cipher),
   m_block_size(m_cipher->block_size()),
   m_feedback_bytes(feedback_bits ? feedback_bits / 8 : m_block_size)
   {
   if(feedback_bits % 8 || feedback() > cipher->block_size())
      throw Invalid_Argument(name() + ": feedback bits " +
                                  std::to_string(feedback_bits) + " not supported");
   }

Member Function Documentation

authenticated()

virtual bool Botan::Cipher_Mode::authenticated ( ) const

inlinevirtualinherited

Returns

true iff this mode provides authentication as well as confidentiality.

Reimplemented in Botan::AEAD_Mode.

Definition at line 179 of file cipher_mode.h.

{ return false; }

block_size()

size_t Botan::CFB_Mode::block_size ( ) const

inlineprotected

Definition at line 47 of file cfb.h.

Referenced by default_nonce_length(), name(), shift_register(), and valid_nonce_length().

{ return m_block_size; }

cipher()

const BlockCipher& Botan::CFB_Mode::cipher ( ) const

inlineprotected

Definition at line 46 of file cfb.h.

Referenced by key_spec(), name(), and shift_register().

{ return *m_cipher; }

clear()

void Botan::CFB_Mode::clear ( )

finaloverridevirtual

Zeroise all state See also reset_msg()

Implements Botan::Cipher_Mode.

Definition at line 23 of file cfb.cpp.

References reset().

   {
   m_cipher->clear();
   reset();
   }

create()

std::unique_ptr< Cipher_Mode > Botan::Cipher_Mode::create ( const std::string &  algo, Cipher_Dir  direction, const std::string &  provider = ""  )

staticinherited

Create an AEAD mode

Parameters

algo	the algorithm to create
direction	specify if this should be an encryption or decryption AEAD
provider	optional specification for provider to use

Returns

an AEAD mode or a null pointer if not available

Definition at line 50 of file cipher_mode.cpp.

References Botan::SCAN_Name::algo_name(), Botan::SCAN_Name::arg(), Botan::SCAN_Name::arg_as_integer(), Botan::SCAN_Name::arg_count(), Botan::BlockCipher::create(), Botan::AEAD_Mode::create(), Botan::StreamCipher::create(), Botan::ENCRYPTION, Botan::get_bc_pad(), Botan::make_openssl_cipher_mode(), Botan::parse_algorithm_name(), Botan::Cipher_Mode::provider(), and Botan::split_on().

Referenced by botan_cipher_init(), Botan::Cipher_Mode::create_or_throw(), Botan::get_cipher_mode(), Botan::pbes2_decrypt(), and Botan::Cipher_Mode::providers().

   {
#if defined(BOTAN_HAS_OPENSSL)
   if(provider.empty() || provider == "openssl")
      {
      std::unique_ptr<Cipher_Mode> openssl_cipher(make_openssl_cipher_mode(algo, direction));

      if(openssl_cipher)
         return openssl_cipher;

      if(!provider.empty())
         return std::unique_ptr<Cipher_Mode>();
      }
#endif

#if defined(BOTAN_HAS_STREAM_CIPHER)
   if(auto sc = StreamCipher::create(algo))
      {
      return std::unique_ptr<Cipher_Mode>(new Stream_Cipher_Mode(sc.release()));
      }
#endif

#if defined(BOTAN_HAS_AEAD_MODES)
   if(auto aead = AEAD_Mode::create(algo, direction))
      {
      return std::unique_ptr<Cipher_Mode>(aead.release());
      }
#endif

   if(algo.find('/') != std::string::npos)
      {
      const std::vector<std::string> algo_parts = split_on(algo, '/');
      const std::string cipher_name = algo_parts[0];
      const std::vector<std::string> mode_info = parse_algorithm_name(algo_parts[1]);

      if(mode_info.empty())
         return std::unique_ptr<Cipher_Mode>();

      std::ostringstream alg_args;

      alg_args << '(' << cipher_name;
      for(size_t i = 1; i < mode_info.size(); ++i)
         alg_args << ',' << mode_info[i];
      for(size_t i = 2; i < algo_parts.size(); ++i)
         alg_args << ',' << algo_parts[i];
      alg_args << ')';

      const std::string mode_name = mode_info[0] + alg_args.str();
      return Cipher_Mode::create(mode_name, direction, provider);
      }

#if defined(BOTAN_HAS_BLOCK_CIPHER)

   SCAN_Name spec(algo);

   if(spec.arg_count() == 0)
      {
      return std::unique_ptr<Cipher_Mode>();
      }

   std::unique_ptr<BlockCipher> bc(BlockCipher::create(spec.arg(0), provider));

   if(!bc)
      {
      return std::unique_ptr<Cipher_Mode>();
      }

#if defined(BOTAN_HAS_MODE_CBC)
   if(spec.algo_name() == "CBC")
      {
      const std::string padding = spec.arg(1, "PKCS7");

      if(padding == "CTS")
         {
         if(direction == ENCRYPTION)
            return std::unique_ptr<Cipher_Mode>(new CTS_Encryption(bc.release()));
         else
            return std::unique_ptr<Cipher_Mode>(new CTS_Decryption(bc.release()));
         }
      else
         {
         std::unique_ptr<BlockCipherModePaddingMethod> pad(get_bc_pad(padding));

         if(pad)
            {
            if(direction == ENCRYPTION)
               return std::unique_ptr<Cipher_Mode>(new CBC_Encryption(bc.release(), pad.release()));
            else
               return std::unique_ptr<Cipher_Mode>(new CBC_Decryption(bc.release(), pad.release()));
            }
         }
      }
#endif

#if defined(BOTAN_HAS_MODE_XTS)
   if(spec.algo_name() == "XTS")
      {
      if(direction == ENCRYPTION)
         return std::unique_ptr<Cipher_Mode>(new XTS_Encryption(bc.release()));
      else
         return std::unique_ptr<Cipher_Mode>(new XTS_Decryption(bc.release()));
      }
#endif

#if defined(BOTAN_HAS_MODE_CFB)
   if(spec.algo_name() == "CFB")
      {
      const size_t feedback_bits = spec.arg_as_integer(1, 8*bc->block_size());
      if(direction == ENCRYPTION)
         return std::unique_ptr<Cipher_Mode>(new CFB_Encryption(bc.release(), feedback_bits));
      else
         return std::unique_ptr<Cipher_Mode>(new CFB_Decryption(bc.release(), feedback_bits));
      }
#endif

#endif

   return std::unique_ptr<Cipher_Mode>();
   }

create_or_throw()

std::unique_ptr< Cipher_Mode > Botan::Cipher_Mode::create_or_throw ( const std::string &  algo, Cipher_Dir  direction, const std::string &  provider = ""  )

staticinherited

Create an AEAD mode, or throw

Parameters

algo	the algorithm to create
direction	specify if this should be an encryption or decryption AEAD
provider	optional specification for provider to use

Returns

an AEAD mode, or throw an exception

Definition at line 40 of file cipher_mode.cpp.

References Botan::Cipher_Mode::create(), and Botan::Cipher_Mode::provider().

Referenced by Botan::ECIES_System_Params::create_cipher(), Botan::CryptoBox::decrypt_bin(), Botan::CryptoBox::encrypt(), and Botan::get_cipher().

   {
   if(auto mode = Cipher_Mode::create(algo, direction, provider))
      return mode;

   throw Lookup_Error("Cipher mode", algo, provider);
   }

default_nonce_length()

size_t Botan::CFB_Mode::default_nonce_length ( ) const

finaloverridevirtual

Returns

the default size for a nonce

Implements Botan::Cipher_Mode.

Definition at line 63 of file cfb.cpp.

References block_size().

   {
   return block_size();
   }

feedback()

size_t Botan::CFB_Mode::feedback ( ) const

inlineprotected

Definition at line 45 of file cfb.h.

Referenced by name(), Botan::CFB_Encryption::process(), Botan::CFB_Decryption::process(), shift_register(), and update_granularity().

{ return m_feedback_bytes; }

finish()

virtual void Botan::Cipher_Mode::finish ( secure_vector< uint8_t > &  final_block, size_t  offset = 0  )

pure virtualinherited

Complete processing of a message.

Parameters

final_block	in/out parameter which must be at least minimum_final_size() bytes, and will be set to any final output
offset	an offset into final_block to begin processing

Implemented in Botan::TLS::TLS_CBC_HMAC_AEAD_Decryption, Botan::CTS_Decryption, Botan::TLS::TLS_CBC_HMAC_AEAD_Encryption, Botan::OCB_Decryption, Botan::CBC_Decryption, Botan::CCM_Decryption, Botan::EAX_Decryption, Botan::SIV_Decryption, Botan::GCM_Decryption, Botan::OCB_Encryption, Botan::CTS_Encryption, Botan::CFB_Decryption, Botan::ChaCha20Poly1305_Decryption, Botan::SIV_Encryption, Botan::CCM_Encryption, Botan::XTS_Decryption, Botan::EAX_Encryption, Botan::GCM_Encryption, Botan::CBC_Encryption, Botan::CFB_Encryption, Botan::ChaCha20Poly1305_Encryption, and Botan::XTS_Encryption.

Referenced by botan_cipher_update(), and Botan::TLS::write_record().

key_spec()

Key_Length_Specification Botan::CFB_Mode::key_spec ( ) const

finaloverridevirtual

Returns

object describing limits on key size

Implements Botan::Cipher_Mode.

Definition at line 58 of file cfb.cpp.

References cipher(), and Botan::SymmetricAlgorithm::key_spec().

   {
   return cipher().key_spec();
   }

minimum_final_size()

size_t Botan::CFB_Mode::minimum_final_size ( ) const

finaloverridevirtual

Returns

required minimium size to finalize() - may be any length larger than this.

Implements Botan::Cipher_Mode.

Definition at line 53 of file cfb.cpp.

   {
   return 0;
   }

name()

std::string Botan::CFB_Mode::name ( ) const

finaloverridevirtual

Implements Botan::Cipher_Mode.

Definition at line 35 of file cfb.cpp.

References block_size(), cipher(), feedback(), Botan::SymmetricAlgorithm::name(), and Botan::ASN1::to_string().

   {
   if(feedback() == cipher().block_size())
      return cipher().name() + "/CFB";
   else
      return cipher().name() + "/CFB(" + std::to_string(feedback()*8) + ")";
   }

output_length()

size_t Botan::CFB_Mode::output_length ( size_t  input_length ) const

finaloverridevirtual

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.

Implements Botan::Cipher_Mode.

Definition at line 43 of file cfb.cpp.

   {
   return input_length;
   }

process()

virtual size_t Botan::Cipher_Mode::process ( uint8_t  msg[], size_t  msg_len  )

pure virtualinherited

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 processed) or for certain AEAD modes zero (indicating that the mode requires the entire message be processed in one pass).

Parameters

msg	the message to be processed
msg_len	length of the message in bytes

Implemented in Botan::OCB_Decryption, Botan::CBC_Decryption, Botan::EAX_Decryption, Botan::GCM_Decryption, Botan::OCB_Encryption, Botan::CFB_Decryption, Botan::ChaCha20Poly1305_Decryption, Botan::XTS_Decryption, Botan::EAX_Encryption, Botan::GCM_Encryption, Botan::CBC_Encryption, Botan::CFB_Encryption, Botan::ChaCha20Poly1305_Encryption, Botan::XTS_Encryption, Botan::TLS::TLS_CBC_HMAC_AEAD_Mode, Botan::SIV_Mode, and Botan::CCM_Mode.

provider()

virtual std::string Botan::Cipher_Mode::provider ( ) const

inlinevirtualinherited

Returns

provider information about this implementation. Default is "base", might also return "sse2", "avx2", "openssl", or some other arbitrary string.

Reimplemented in Botan::GCM_Mode.

Definition at line 236 of file cipher_mode.h.

Referenced by Botan::AEAD_Mode::create(), Botan::Cipher_Mode::create(), Botan::AEAD_Mode::create_or_throw(), and Botan::Cipher_Mode::create_or_throw().

{ return "base"; }

providers()

std::vector< std::string > Botan::Cipher_Mode::providers ( const std::string &  algo_spec )

staticinherited

Returns

list of available providers for this algorithm, empty if not available

Parameters

algo_spec

algorithm name

Definition at line 173 of file cipher_mode.cpp.

References Botan::Cipher_Mode::create(), and Botan::ENCRYPTION.

   {
   const std::vector<std::string>& possible = { "base", "openssl" };
   std::vector<std::string> providers;
   for(auto&& prov : possible)
      {
      std::unique_ptr<Cipher_Mode> mode = Cipher_Mode::create(algo_spec, ENCRYPTION, prov);
      if(mode)
         {
         providers.push_back(prov); // available
         }
      }
   return providers;
   }

reset()

void Botan::CFB_Mode::reset ( )

finaloverridevirtual

Resets just the message specific state and allows encrypting again under the existing key

Implements Botan::Cipher_Mode.

Definition at line 29 of file cfb.cpp.

References m_keystream, and m_state.

Referenced by clear().

   {
   m_state.clear();
   m_keystream.clear();
   }

set_key() [1/3]

template<typename Alloc >

void Botan::Cipher_Mode::set_key ( const std::vector< uint8_t, Alloc > &  key )

inlineinherited

Set the symmetric key of this transform

Parameters

key	contains the key material

Definition at line 206 of file cipher_mode.h.

Referenced by botan_cipher_set_key().

         {
         set_key(key.data(), key.size());
         }

set_key() [2/3]

void Botan::Cipher_Mode::set_key ( const SymmetricKey &  key )

inlineinherited

Set the symmetric key of this transform

Parameters

key	contains the key material

Definition at line 215 of file cipher_mode.h.

References Botan::OctetString::begin(), and Botan::OctetString::length().

         {
         set_key(key.begin(), key.length());
         }

set_key() [3/3]

void Botan::Cipher_Mode::set_key ( const uint8_t  key[], size_t  length  )

inlineinherited

Set the symmetric key of this transform

Parameters

key	contains the key material
length	in bytes of key param

Definition at line 225 of file cipher_mode.h.

         {
         if(!valid_keylength(length))
            throw Invalid_Key_Length(name(), length);
         key_schedule(key, length);
         }

shift_register()

void Botan::CFB_Mode::shift_register ( )

protected

Definition at line 100 of file cfb.cpp.

References block_size(), cipher(), Botan::copy_mem(), Botan::BlockCipher::encrypt(), feedback(), m_keystream, m_keystream_pos, and m_state.

Referenced by Botan::CFB_Encryption::process(), and Botan::CFB_Decryption::process().

   {
   const size_t shift = feedback();
   const size_t carryover = block_size() - shift;

   if(carryover > 0)
      {
      copy_mem(m_state.data(), &m_state[shift], carryover);
      }
   copy_mem(&m_state[carryover], m_keystream.data(), shift);
   cipher().encrypt(m_state, m_keystream);
   m_keystream_pos = 0;
   }

start() [1/3]

template<typename Alloc >

void Botan::Cipher_Mode::start ( const std::vector< uint8_t, Alloc > &  nonce )

inlineinherited

Begin processing a message.

Parameters

nonce

the per message nonce

Definition at line 72 of file cipher_mode.h.

Referenced by botan_cipher_start(), and Botan::TLS::write_record().

         {
         start_msg(nonce.data(), nonce.size());
         }

start() [2/3]

void Botan::Cipher_Mode::start ( const uint8_t  nonce[], size_t  nonce_len  )

inlineinherited

Begin processing a message.

Parameters

nonce	the per message nonce
nonce_len	length of nonce

Definition at line 82 of file cipher_mode.h.

         {
         start_msg(nonce, nonce_len);
         }

start() [3/3]

void Botan::Cipher_Mode::start ( )

inlineinherited

Begin processing a message.

Definition at line 90 of file cipher_mode.h.

         {
         return start_msg(nullptr, 0);
         }

tag_size()

virtual size_t Botan::Cipher_Mode::tag_size ( ) const

inlinevirtualinherited

Returns

the size of the authentication tag used (in bytes)

Reimplemented in Botan::SIV_Mode, Botan::OCB_Mode, Botan::CCM_Mode, Botan::TLS::TLS_CBC_HMAC_AEAD_Mode, Botan::ChaCha20Poly1305_Mode, Botan::GCM_Mode, and Botan::EAX_Mode.

Definition at line 184 of file cipher_mode.h.

Referenced by botan_cipher_get_tag_length().

{ return 0; }

update()

void Botan::Cipher_Mode::update ( secure_vector< uint8_t > &  buffer, size_t  offset = 0  )

inlineinherited

Process some data. Input must be in size update_granularity() uint8_t blocks.

Parameters

buffer	in/out parameter which will possibly be resized
offset	an offset into blocks to begin processing

Definition at line 115 of file cipher_mode.h.

References BOTAN_ASSERT.

Referenced by botan_cipher_update(), Botan::XTS_Encryption::finish(), Botan::ChaCha20Poly1305_Encryption::finish(), Botan::CFB_Encryption::finish(), Botan::CBC_Encryption::finish(), Botan::EAX_Encryption::finish(), Botan::XTS_Decryption::finish(), Botan::CFB_Decryption::finish(), Botan::CTS_Encryption::finish(), Botan::CBC_Decryption::finish(), Botan::TLS::TLS_CBC_HMAC_AEAD_Encryption::finish(), Botan::CTS_Decryption::finish(), and Botan::TLS::TLS_CBC_HMAC_AEAD_Decryption::finish().

         {
         BOTAN_ASSERT(buffer.size() >= offset, "Offset ok");
         uint8_t* buf = buffer.data() + offset;
         const size_t buf_size = buffer.size() - offset;

         const size_t written = process(buf, buf_size);
         buffer.resize(offset + written);
         }

update_granularity()

size_t Botan::CFB_Mode::update_granularity ( ) const

finaloverridevirtual

Returns

size of required blocks to update

Implements Botan::Cipher_Mode.

Definition at line 48 of file cfb.cpp.

References feedback().

   {
   return feedback();
   }

valid_keylength()

bool Botan::Cipher_Mode::valid_keylength ( size_t  length ) const

inlineinherited

Check whether a given key length is valid for this algorithm.

Parameters

length

the key length to be checked.

Returns

true if the key length is valid.

Definition at line 196 of file cipher_mode.h.

         {
         return key_spec().valid_keylength(length);
         }

valid_nonce_length()

bool Botan::CFB_Mode::valid_nonce_length ( size_t  nonce_len ) const

finaloverridevirtual

Returns

true iff nonce_len is a valid length for the nonce

Implements Botan::Cipher_Mode.

Definition at line 68 of file cfb.cpp.

References block_size().

   {
   return (n == 0 || n == block_size());
   }

Member Data Documentation

m_keystream

secure_vector<uint8_t> Botan::CFB_Mode::m_keystream

protected

Definition at line 50 of file cfb.h.

Referenced by Botan::CFB_Encryption::process(), Botan::CFB_Decryption::process(), reset(), and shift_register().

m_keystream_pos

size_t Botan::CFB_Mode::m_keystream_pos = 0

protected

Definition at line 51 of file cfb.h.

Referenced by Botan::CFB_Encryption::process(), Botan::CFB_Decryption::process(), and shift_register().

m_state

secure_vector<uint8_t> Botan::CFB_Mode::m_state

protected

Definition at line 49 of file cfb.h.

Referenced by reset(), and shift_register().

---

The documentation for this class was generated from the following files:

• src/lib/modes/cfb/cfb.h
• src/lib/modes/cfb/cfb.cpp