Botan::GCM_SIV_Decryption Class Reference

#include <gcm_siv.h>

Inheritance diagram for Botan::GCM_SIV_Decryption:

Public Member Functions
bool	associated_data_requires_key () const final
	The AD is buffered as-is; it is not processed until finish.
bool	authenticated () const
void	clear () final
size_t	default_nonce_length () const override
void	finish (secure_vector< uint8_t > &final_block, size_t offset=0)
template<concepts::resizable_byte_buffer T>
void	finish (T &final_block, size_t offset=0)
	GCM_SIV_Decryption (std::unique_ptr< BlockCipher > cipher)
bool	has_keying_material () const final
size_t	ideal_granularity () const final
Key_Length_Specification	key_spec () const final
virtual size_t	maximum_associated_data_inputs () const
size_t	maximum_keylength () const
size_t	minimum_final_size () const override
size_t	minimum_keylength () const
std::string	name () const final
size_t	output_length (size_t input_length) const override
size_t	process (std::span< uint8_t > msg)
size_t	process (uint8_t msg[], size_t msg_len)
std::string	provider () const final
bool	requires_entire_message () const final
void	reset () final
void	set_ad (std::span< const uint8_t > ad)
void	set_associated_data (const uint8_t ad[], size_t ad_len)
void	set_associated_data (std::span< const uint8_t > ad)
void	set_associated_data_n (size_t idx, std::span< const uint8_t > ad) final
template<typename Alloc>
void	set_associated_data_vec (const std::vector< uint8_t, Alloc > &ad)
void	set_key (const OctetString &key)
void	set_key (const uint8_t key[], size_t length)
void	set_key (std::span< const uint8_t > key)
void	start ()
void	start (const uint8_t nonce[], size_t nonce_len)
void	start (std::span< const uint8_t > nonce)
size_t	tag_size () const final
template<concepts::resizable_byte_buffer T>
void	update (T &buffer, size_t offset=0)
size_t	update_granularity () const final
bool	valid_keylength (size_t length) const
bool	valid_nonce_length (size_t len) const final

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

Protected Member Functions
void	assert_key_material_set () const
void	assert_key_material_set (bool predicate) const
std::array< uint8_t, BS >	compute_tag (std::span< const uint8_t > ptext)
	Compute the expected tag for the (unpadded) plaintext.
void	ctr_xor (std::span< const uint8_t, BS > tag, uint8_t buf[], size_t len)
	XOR the buffer with the CTR keystream, starting from the tag-derived counter.
bool	in_msg () const
secure_vector< uint8_t > &	msg_buf ()

Static Protected Attributes
static constexpr size_t	BS = 16
static constexpr uint64_t	MAX_INPUT_LEN = static_cast<uint64_t>(1) << 36
	RFC 8452 limits both the plaintext and the AD to 2**36 bytes.

Detailed Description

GCM-SIV Decryption

Definition at line 111 of file gcm_siv.h.

Constructor & Destructor Documentation

GCM_SIV_Decryption()

Botan::GCM_SIV_Decryption::GCM_SIV_Decryption ( std::unique_ptr< BlockCipher > cipher )

inlineexplicit

Parameters

cipher

the 128 bit block cipher to use

Definition at line 116 of file gcm_siv.h.

: GCM_SIV_Mode(std::move(cipher)) {}

References Botan::GCM_SIV_Mode::GCM_SIV_Mode().

Member Function Documentation

assert_key_material_set() [1/2]

void Botan::SymmetricAlgorithm::assert_key_material_set ( ) const

inlineprotectedinherited

Throw Key_Not_Set unless a key has been set on this object

Definition at line 180 of file sym_algo.h.

{ assert_key_material_set(has_keying_material()); }

References assert_key_material_set(), and has_keying_material().

Referenced by assert_key_material_set(), Botan::Salsa20::cipher_bytes(), Botan::Lion::decrypt_n(), Botan::Lion::encrypt_n(), Botan::GHASH::final(), Botan::Polyval::final(), Botan::Salsa20::generate_keystream(), Botan::GHASH::nonce_hash(), Botan::GHASH::reset_associated_data(), Botan::ChaCha::seek(), Botan::CTR_BE::seek(), Botan::Salsa20::seek(), Botan::GHASH::set_associated_data(), Botan::OCB_Mode::set_associated_data_n(), Botan::Salsa20::set_iv_bytes(), Botan::GHASH::update(), Botan::Polyval::update(), Botan::GHASH::update_associated_data(), and Botan::Polyval::zero_pad().

assert_key_material_set() [2/2]

void Botan::SymmetricAlgorithm::assert_key_material_set ( bool predicate ) const

inlineprotectedinherited

Throw Key_Not_Set unless the predicate holds

Parameters

predicate

if false, a Key_Not_Set exception is thrown

Definition at line 186 of file sym_algo.h.

                                                         {
         if(!predicate) {
            throw_key_not_set_error();
         }
      }

associated_data_requires_key()

bool Botan::GCM_SIV_Mode::associated_data_requires_key ( ) const

inlinefinalvirtualinherited

The AD is buffered as-is; it is not processed until finish.

Reimplemented from Botan::AEAD_Mode.

Definition at line 40 of file gcm_siv.h.

{ return false; }

authenticated()

bool Botan::Cipher_Mode::authenticated ( ) const

inlineinherited

Return the length in bytes of the authentication tag this algorithm generates. If the mode is not authenticated, this will return 0.

Returns

true iff this mode provides authentication as well as confidentiality.

Definition at line 272 of file cipher_mode.h.

{ return this->tag_size() > 0; }

References tag_size().

clear()

void Botan::GCM_SIV_Mode::clear ( )

finalvirtualinherited

Reset the internal state. This includes not just the key, but any partial message that may have been in process.

Implements Botan::SymmetricAlgorithm.

Definition at line 52 of file gcm_siv.cpp.

                         {
   m_cipher->clear();
   m_kgk_len = 0;
   zap(m_ad);
   reset();
}

References reset(), and Botan::zap().

compute_tag()

std::array< uint8_t, GCM_SIV_Mode::BS > Botan::GCM_SIV_Mode::compute_tag ( std::span< const uint8_t > ptext )

protectedinherited

Compute the expected tag for the (unpadded) plaintext.

Definition at line 169 of file gcm_siv.cpp.

                                                                                        {
   m_polyval.update(m_ad);
   m_polyval.zero_pad();
   m_polyval.update(ptext);
   m_polyval.zero_pad();
 
   const uint64_t ad_bits = 8 * static_cast<uint64_t>(m_ad.size());
   const uint64_t pt_bits = 8 * static_cast<uint64_t>(ptext.size());
   m_polyval.update(store_le(ad_bits, pt_bits));
 
   std::array<uint8_t, BS> S{};
   m_polyval.final(S);
 
   /*
   RFC 8452 section 4: "XOR the first twelve bytes of S_s with the nonce
   and clear the most significant bit of the last byte.  Encrypt the
   result with AES using the message-encryption key to produce the tag."
   */
   xor_buf(S.data(), m_nonce.data(), m_nonce.size());
   S[15] &= 0x7f;
   m_msg_cipher->encrypt(S);
 
   return S;
}

References Botan::store_le(), and Botan::xor_buf().

create()

std::unique_ptr< AEAD_Mode > Botan::AEAD_Mode::create ( std::string_view algo, Cipher_Dir direction, std::string_view 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 63 of file aead.cpp.

                                                                                                       {
   BOTAN_UNUSED(provider);
#if defined(BOTAN_HAS_AEAD_CHACHA20_POLY1305)
   if(algo == "ChaCha20Poly1305") {
      if(dir == Cipher_Dir::Encryption) {
         return std::make_unique<ChaCha20Poly1305_Encryption>();
      } else {
         return std::make_unique<ChaCha20Poly1305_Decryption>();
      }
   }
#endif
 
#if defined(BOTAN_HAS_ASCON_AEAD128)
   if(algo == "Ascon-AEAD128") {
      if(dir == Cipher_Dir::Encryption) {
         return std::make_unique<Ascon_AEAD128_Encryption>();
      } else {
         return std::make_unique<Ascon_AEAD128_Decryption>();
      }
   }
#endif
 
   if(algo.find('/') != std::string::npos) {
      const std::vector<std::string> algo_parts = split_on(algo, '/');
      if(algo_parts.size() < 2) {
         return std::unique_ptr<AEAD_Mode>();
      }
      const std::string_view 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<AEAD_Mode>();
      }
 
      std::ostringstream mode_name;
 
      mode_name << mode_info[0] << '(' << cipher_name;
      for(size_t i = 1; i < mode_info.size(); ++i) {
         mode_name << ',' << mode_info[i];
      }
      for(size_t i = 2; i < algo_parts.size(); ++i) {
         mode_name << ',' << algo_parts[i];
      }
      mode_name << ')';
 
      return AEAD_Mode::create(mode_name.str(), dir);
   }
 
#if defined(BOTAN_HAS_BLOCK_CIPHER)
 
   const SCAN_Name req(algo);
 
   if(req.arg_count() == 0) {
      return std::unique_ptr<AEAD_Mode>();
   }
 
   auto bc = BlockCipher::create(req.arg(0), provider);
 
   if(!bc) {
      return std::unique_ptr<AEAD_Mode>();
   }
 
   #if defined(BOTAN_HAS_AEAD_CCM)
   if(req.algo_name() == "CCM") {
      const size_t tag_len = req.arg_as_integer(1, 16);
      const size_t L_len = req.arg_as_integer(2, 3);
      if(dir == Cipher_Dir::Encryption) {
         return std::make_unique<CCM_Encryption>(std::move(bc), tag_len, L_len);
      } else {
         return std::make_unique<CCM_Decryption>(std::move(bc), tag_len, L_len);
      }
   }
   #endif
 
   #if defined(BOTAN_HAS_AEAD_GCM)
   if(req.algo_name() == "GCM") {
      const size_t tag_len = req.arg_as_integer(1, 16);
      if(dir == Cipher_Dir::Encryption) {
         return std::make_unique<GCM_Encryption>(std::move(bc), tag_len);
      } else {
         return std::make_unique<GCM_Decryption>(std::move(bc), tag_len);
      }
   }
   #endif
 
   #if defined(BOTAN_HAS_AEAD_GCM_SIV)
   if(req.algo_name() == "GCM-SIV") {
      // Unlike GCM the tag length is fixed, so reject eg "AES-128/GCM-SIV(12)"
      if(req.arg_count() != 1) {
         return std::unique_ptr<AEAD_Mode>();
      }
      if(dir == Cipher_Dir::Encryption) {
         return std::make_unique<GCM_SIV_Encryption>(std::move(bc));
      } else {
         return std::make_unique<GCM_SIV_Decryption>(std::move(bc));
      }
   }
   #endif
 
   #if defined(BOTAN_HAS_AEAD_OCB)
   if(req.algo_name() == "OCB") {
      const size_t tag_len = req.arg_as_integer(1, 16);
      if(dir == Cipher_Dir::Encryption) {
         return std::make_unique<OCB_Encryption>(std::move(bc), tag_len);
      } else {
         return std::make_unique<OCB_Decryption>(std::move(bc), tag_len);
      }
   }
   #endif
 
   #if defined(BOTAN_HAS_AEAD_EAX)
   if(req.algo_name() == "EAX") {
      const size_t tag_len = req.arg_as_integer(1, bc->block_size());
      if(dir == Cipher_Dir::Encryption) {
         return std::make_unique<EAX_Encryption>(std::move(bc), tag_len);
      } else {
         return std::make_unique<EAX_Decryption>(std::move(bc), tag_len);
      }
   }
   #endif
 
   #if defined(BOTAN_HAS_AEAD_SIV)
   if(req.algo_name() == "SIV") {
      if(dir == Cipher_Dir::Encryption) {
         return std::make_unique<SIV_Encryption>(std::move(bc));
      } else {
         return std::make_unique<SIV_Decryption>(std::move(bc));
      }
   }
   #endif
 
#endif
 
   return std::unique_ptr<AEAD_Mode>();
}

References Botan::SCAN_Name::algo_name(), Botan::SCAN_Name::arg(), Botan::SCAN_Name::arg_as_integer(), Botan::SCAN_Name::arg_count(), BOTAN_UNUSED, create(), Botan::BlockCipher::create(), Botan::Encryption, Botan::parse_algorithm_name(), Botan::Cipher_Mode::provider(), and Botan::split_on().

Referenced by Botan::ChaCha20Poly1305_Mode::ChaCha20Poly1305_Mode(), create(), Botan::Cipher_Mode::create(), create_or_throw(), Botan::get_aead(), and Botan::TLS::Cipher_State::is_compatible_with().

create_or_throw()

std::unique_ptr< AEAD_Mode > Botan::AEAD_Mode::create_or_throw ( std::string_view algo, Cipher_Dir direction, std::string_view 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 53 of file aead.cpp.

                                                                               {
   if(auto aead = AEAD_Mode::create(algo, dir, provider)) {
      return aead;
   }
 
   throw Lookup_Error("AEAD", algo, provider);
}

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

Referenced by Botan::TLS::Cipher_State::advance_with_server_hello(), Botan::TLS::Connection_Cipher_State::Connection_Cipher_State(), Botan::TLS::Session::decrypt(), and Botan::TLS::Session::encrypt().

ctr_xor()

void Botan::GCM_SIV_Mode::ctr_xor ( std::span< const uint8_t, BS > tag, uint8_t buf[], size_t len )

protectedinherited

XOR the buffer with the CTR keystream, starting from the tag-derived counter.

Definition at line 194 of file gcm_siv.cpp.

                                                                                    {
   /*
   RFC 8452 section 4: "The initial counter block is the tag with the
   most significant bit of the last byte set to one.  The counter
   advances by incrementing the first 32 bits interpreted as an
   unsigned, little-endian integer, wrapping at 2^32."
   */
   std::array<uint8_t, BS> ctr_block{};
   copy_mem(ctr_block, tag);
   ctr_block[15] |= 0x80;
 
   uint32_t ctr32 = load_le<uint32_t>(ctr_block.data(), 0);
 
   secure_vector<uint8_t> ks(m_msg_cipher->parallel_bytes());
 
   while(len > 0) {
      const size_t blocks = std::min((len + BS - 1) / BS, ks.size() / BS);
 
      for(size_t i = 0; i != blocks; ++i) {
         copy_mem(&ks[BS * i], ctr_block.data(), BS);
         store_le(ctr32, &ks[BS * i]);
         ctr32 += 1;
      }
 
      m_msg_cipher->encrypt_n(ks.data(), ks.data(), blocks);
 
      const size_t todo = std::min(len, blocks * BS);
      xor_buf(buf, ks.data(), todo);
      buf += todo;
      len -= todo;
   }
}

References BS, Botan::copy_mem(), Botan::load_le(), Botan::store_le(), and Botan::xor_buf().

default_nonce_length()

size_t Botan::AEAD_Mode::default_nonce_length ( ) const

inlineoverridevirtualinherited

Return the default nonce length for this mode

Returns

default AEAD nonce size (a commonly supported value among AEAD modes, and large enough that random collisions are unlikely)

Implements Botan::Cipher_Mode.

Reimplemented in Botan::Ascon_AEAD128_Mode, Botan::CCM_Mode, and Botan::TLS::TLS_CBC_HMAC_AEAD_Mode.

Definition at line 139 of file aead.h.

{ return 12; }

finish() [1/2]

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

inlineinherited

Complete procession of a message with a final input of buffer, which is treated the same as with update(). If you have the entire message in hand, calling finish() without ever calling update() is both efficient and convenient.

When using an AEAD_Mode, if the supplied authentication tag does not validate, this will throw an instance of Invalid_Authentication_Tag.

If this occurs, all plaintext previously output via calls to update must be destroyed and not used in any way that an attacker could observe the effects of. This could be anything from echoing the plaintext back (perhaps in an error message), or by making an external RPC whose destination or contents depend on the plaintext. The only thing you can do is buffer it, and in the event of an invalid tag, erase the previously decrypted content from memory.

One simple way to assure this could never happen is to never call update, and instead always marshal the entire message into a single buffer and call finish on it when decrypting.

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

Definition at line 185 of file cipher_mode.h.

{ finish_msg(final_block, offset); }

References finish_msg().

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

finish() [2/2]

template<concepts::resizable_byte_buffer T>

void Botan::Cipher_Mode::finish ( T & final_block, size_t offset = 0 )

inlineinherited

Complete procession of a message.

Note: Using this overload with anything but a Botan::secure_vector<> is copying the bytes in the in/out buffer.

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

Definition at line 198 of file cipher_mode.h.

                                                   {
         Botan::secure_vector<uint8_t> tmp(final_block.begin(), final_block.end());
         finish_msg(tmp, offset);
         final_block.resize(tmp.size());
         std::copy(tmp.begin(), tmp.end(), final_block.begin());
      }

References finish_msg().

has_keying_material()

bool Botan::GCM_SIV_Mode::has_keying_material ( ) const

finalvirtualinherited

Test whether a key has been set on this object

Returns

true if a key has been set on this object

Implements Botan::SymmetricAlgorithm.

Definition at line 92 of file gcm_siv.cpp.

                                             {
   return m_cipher->has_keying_material();
}

ideal_granularity()

size_t Botan::GCM_SIV_Mode::ideal_granularity ( ) const

finalvirtualinherited

Return an ideal granularity. This will be a multiple of the result of update_granularity but may be larger. If so it indicates that better performance may be achieved by providing buffers that are at least that size (due to SIMD execution, etc).

Implements Botan::Cipher_Mode.

Definition at line 80 of file gcm_siv.cpp.

                                             {
   return BS * std::max<size_t>(2, BlockCipher::ParallelismMult);
}

References BS, and Botan::BlockCipher::ParallelismMult.

in_msg()

bool Botan::GCM_SIV_Mode::in_msg ( ) const

inlineprotectedinherited

Definition at line 62 of file gcm_siv.h.

{ return m_in_msg; }

key_spec()

Key_Length_Specification Botan::GCM_SIV_Mode::key_spec ( ) const

finalvirtualinherited

Return the key lengths supported by this algorithm

Returns

object describing limits on key size

Implements Botan::SymmetricAlgorithm.

Definition at line 88 of file gcm_siv.cpp.

                                                      {
   return m_key_spec;
}

maximum_associated_data_inputs()

virtual size_t Botan::AEAD_Mode::maximum_associated_data_inputs ( ) const

inlinevirtualinherited

Returns the maximum supported number of associated data inputs which can be provided to set_associated_data_n

If returns 0, then no associated data is supported.

Reimplemented in Botan::SIV_Mode.

Definition at line 99 of file aead.h.

{ return 1; }

maximum_keylength()

size_t Botan::SymmetricAlgorithm::maximum_keylength ( ) const

inlineinherited

Return the largest acceptable key length

Returns

maximum allowed key length

Definition at line 130 of file sym_algo.h.

{ return key_spec().maximum_keylength(); }

References key_spec().

minimum_final_size()

size_t Botan::GCM_SIV_Decryption::minimum_final_size ( ) const

inlineoverridevirtual

Return the smallest input accepted by finish()

Returns

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

Implements Botan::Cipher_Mode.

Definition at line 120 of file gcm_siv.h.

{ return tag_size(); }

References Botan::GCM_SIV_Mode::tag_size().

minimum_keylength()

size_t Botan::SymmetricAlgorithm::minimum_keylength ( ) const

inlineinherited

Return the smallest acceptable key length

Returns

minimum allowed key length

Definition at line 136 of file sym_algo.h.

{ return key_spec().minimum_keylength(); }

References key_spec().

msg_buf()

secure_vector< uint8_t > & Botan::GCM_SIV_Mode::msg_buf ( )

inlineprotectedinherited

Definition at line 60 of file gcm_siv.h.

{ return m_msg_buf; }

References msg_buf().

Referenced by msg_buf().

name()

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

finalvirtualinherited

Return the name of this algorithm

Returns

the algorithm name

Implements Botan::SymmetricAlgorithm.

Definition at line 68 of file gcm_siv.cpp.

                                   {
   return fmt("{}/GCM-SIV", m_cipher_name);
}

References Botan::fmt().

Referenced by GCM_SIV_Mode().

output_length()

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

overridevirtual

Returns the size of the output if this transform is used to process a message with input_length bytes. In most cases the answer is precise. If it is not possible to precise (namely for CBC decryption) instead an upper bound is returned.

Implements Botan::Cipher_Mode.

Definition at line 249 of file gcm_siv.cpp.

                                                                  {
   BOTAN_ARG_CHECK(input_length >= tag_size(), "Message too short to be valid");
   return input_length - tag_size();
}

References BOTAN_ARG_CHECK, and Botan::GCM_SIV_Mode::tag_size().

process() [1/2]

size_t Botan::Cipher_Mode::process ( std::span< uint8_t > msg )

inlineinherited

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

Returns

bytes written in-place

Definition at line 132 of file cipher_mode.h.

{ return this->process_msg(msg.data(), msg.size()); }

References process_msg().

Referenced by botan_cipher_update(), Botan::TLS::TLS_NULL_HMAC_AEAD_Decryption::finish_msg(), and update().

process() [2/2]

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

inlineinherited

Process message blocks in place

Parameters

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

Returns

bytes written in-place

Definition at line 140 of file cipher_mode.h.

{ return this->process_msg(msg, msg_len); }

References process_msg().

provider()

std::string Botan::GCM_SIV_Mode::provider ( ) const

finalvirtualinherited

Return the name of the provider implementing this object

Returns

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

Reimplemented from Botan::Cipher_Mode.

Definition at line 72 of file gcm_siv.cpp.

                                       {
   return m_polyval.provider();
}

providers()

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

staticinherited

List the providers available for a given cipher mode

Returns

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

Parameters

algo_spec

algorithm name

Definition at line 174 of file cipher_mode.cpp.

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

References create(), Botan::Encryption, and providers().

Referenced by providers().

requires_entire_message()

bool Botan::GCM_SIV_Mode::requires_entire_message ( ) const

inlinefinalvirtualinherited

Certain modes require the entire message be available before any processing can occur. For such modes, input will be consumed but not returned, until finish is called, which returns the entire message.

This function returns true if this mode has this style of operation.

Reimplemented from Botan::Cipher_Mode.

Definition at line 37 of file gcm_siv.h.

{ return true; }

reset()

void Botan::GCM_SIV_Mode::reset ( )

finalvirtualinherited

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

Implements Botan::Cipher_Mode.

Definition at line 59 of file gcm_siv.cpp.

                         {
   // The derived keys are per-message; start_msg rekeys both
   m_msg_cipher->clear();
   m_polyval.clear();
   secure_scrub_memory(m_nonce);
   m_msg_buf.clear();
   m_in_msg = false;
}

References Botan::secure_scrub_memory().

Referenced by clear().

set_ad()

void Botan::AEAD_Mode::set_ad ( std::span< const uint8_t > ad )

inlineinherited

Set associated data that is not included in the ciphertext but that should be authenticated. Must be called after set_key() and before start().

See set_associated_data().

Parameters

ad	the associated data

Definition at line 132 of file aead.h.

{ set_associated_data(ad); }

References set_ad(), and set_associated_data().

Referenced by set_ad().

set_associated_data() [1/2]

void Botan::AEAD_Mode::set_associated_data ( const uint8_t ad[], size_t ad_len )

inlineinherited

Set associated data that is not included in the ciphertext but that should be authenticated. Must be called after set_key() and before start().

Parameters

ad	the associated data
ad_len	length of ad in bytes

Definition at line 69 of file aead.h.

{ set_associated_data(std::span(ad, ad_len)); }

References set_associated_data().

Referenced by set_associated_data().

set_associated_data() [2/2]

void Botan::AEAD_Mode::set_associated_data ( std::span< const uint8_t > ad )

inlineinherited

Set associated data that is not included in the ciphertext but that should be authenticated. Must be called after set_key() and before start().

Unless reset by another call, the associated data is kept between messages. Thus, if the AD does not change, calling once (after set_key()) is the optimum.

Parameters

ad	the associated data

Definition at line 59 of file aead.h.

{ set_associated_data_n(0, ad); }

References set_associated_data_n().

Referenced by set_ad(), set_associated_data_vec(), and Botan::TLS::write_record().

set_associated_data_n()

void Botan::GCM_SIV_Mode::set_associated_data_n ( size_t idx, std::span< const uint8_t > ad )

finalvirtualinherited

Set associated data that is not included in the ciphertext but that should be authenticated. Must be called after set_key() and before start().

Unless reset by another call, the associated data is kept between messages. Thus, if the AD does not change, calling once (after set_key()) is the optimum.

Some AEADs (namely SIV) support multiple AD inputs. For all other modes only nominal AD input 0 is supported; all other values of idx will cause an exception.

Derived AEADs must implement this. For AEADs where maximum_associated_data_inputs() returns 1 (the default), the idx must simply be ignored.

Parameters

idx	which associated data to set
ad	the associated data

Implements Botan::AEAD_Mode.

Definition at line 102 of file gcm_siv.cpp.

                                                                              {
   BOTAN_ARG_CHECK(idx == 0, "GCM-SIV: cannot handle non-zero index in set_associated_data_n");
   BOTAN_STATE_CHECK(!m_in_msg);
   BOTAN_ARG_CHECK(static_cast<uint64_t>(ad.size()) <= MAX_INPUT_LEN, "GCM-SIV AD too large");
   m_ad.assign(ad.begin(), ad.end());
}

References BOTAN_ARG_CHECK, BOTAN_STATE_CHECK, and MAX_INPUT_LEN.

set_associated_data_vec()

template<typename Alloc>

void Botan::AEAD_Mode::set_associated_data_vec ( const std::vector< uint8_t, Alloc > & ad )

inlineinherited

Set associated data that is not included in the ciphertext but that should be authenticated. Must be called after set_key() and before start().

See set_associated_data().

Parameters

ad	the associated data

Definition at line 119 of file aead.h.

                                                                        {
         set_associated_data(ad);
      }

References set_associated_data(), and set_associated_data_vec().

Referenced by set_associated_data_vec().

set_key() [1/3]

void Botan::SymmetricAlgorithm::set_key ( const OctetString & key )

inherited

Set the symmetric key of this object.

Parameters

key	the SymmetricKey to be set.

Definition at line 14 of file sym_algo.cpp.

                                                       {
   set_key(std::span{key.begin(), key.length()});
}

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

Referenced by Botan::create_aes_row_generator(), Botan::Sodium::crypto_stream_salsa20(), Botan::Sodium::crypto_stream_salsa20_xor_ic(), Botan::Sodium::crypto_stream_xsalsa20(), Botan::Sodium::crypto_stream_xsalsa20_xor_ic(), Botan::FPE::fe1_decrypt(), Botan::FPE::fe1_encrypt(), Botan::Sphincs_Hash_Functions_Sha2::PRF_msg(), Botan::Sodium::randombytes_buf_deterministic(), Botan::TLS::TLS_NULL_HMAC_AEAD_Mode::reset(), and set_key().

set_key() [2/3]

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

inlineinherited

Set the symmetric key of this object.

Parameters

key	the to be set as a byte array.
length	in bytes of key param

Definition at line 162 of file sym_algo.h.

{ set_key(std::span{key, length}); }

References set_key().

Referenced by set_key().

set_key() [3/3]

void Botan::SymmetricAlgorithm::set_key ( std::span< const uint8_t > key )

inherited

Set the symmetric key of this object.

Parameters

key	the contiguous byte range to be set.

Definition at line 22 of file sym_algo.cpp.

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

References name(), and valid_keylength().

start() [1/3]

void Botan::Cipher_Mode::start ( )

inlineinherited

Begin processing a message.

The exact semantics of this depend on the mode. For many modes, the call will fail since a nonce must be provided.

For certain modes such as CBC this will instead cause the last ciphertext block to be used as the nonce of the new message; doing this isn't a good idea, but some (mostly older) protocols do this.

Definition at line 117 of file cipher_mode.h.

{ return start_msg(nullptr, 0); }

References start_msg().

start() [2/3]

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

inlineinherited

Begin processing a message with a fresh nonce.

Parameters

nonce	the per message nonce
nonce_len	length of nonce

Definition at line 105 of file cipher_mode.h.

{ start_msg(nonce, nonce_len); }

References start_msg().

start() [3/3]

void Botan::Cipher_Mode::start ( std::span< const uint8_t > nonce )

inlineinherited

Begin processing a message with a fresh nonce.

Warning

Typically one must not reuse the same nonce for more than one message under the same key. For most cipher modes this would mean total loss of security and/or authenticity guarantees.

Note

If reliably generating unique nonces is difficult in your environment, use SIV which retains security even if nonces are repeated.

Parameters

nonce

the per message nonce

Definition at line 98 of file cipher_mode.h.

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

References start_msg().

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

tag_size()

size_t Botan::GCM_SIV_Mode::tag_size ( ) const

inlinefinalvirtualinherited

Return the authentication tag length of this mode

Returns

the size of the authentication tag used (in bytes)

Reimplemented from Botan::Cipher_Mode.

Definition at line 35 of file gcm_siv.h.

{ return 16; }

Referenced by Botan::GCM_SIV_Decryption::minimum_final_size(), Botan::GCM_SIV_Decryption::output_length(), and Botan::GCM_SIV_Encryption::output_length().

update()

template<concepts::resizable_byte_buffer T>

void Botan::Cipher_Mode::update ( T & buffer, size_t offset = 0 )

inlineinherited

Process some data. Input must be in size update_granularity() uint8_t blocks. The buffer is an in/out parameter and may be resized. In particular, some modes require that all input be consumed before any output is produced; with these modes, buffer will be returned empty.

The first offset bytes of buffer will be ignored (this allows in place processing of a buffer that contains an initial plaintext header).

Parameters

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

Definition at line 155 of file cipher_mode.h.

                                              {
         const size_t written = process(std::span(buffer).subspan(offset));
         buffer.resize(offset + written);
      }

References process().

update_granularity()

size_t Botan::GCM_SIV_Mode::update_granularity ( ) const

finalvirtualinherited

The :cpp:class:Cipher_Mode interface requires message processing in multiples of the block size. This returns size of required blocks to update. If the mode implementation does not require buffering it will return 1.

Returns

size of required blocks to update

Implements Botan::Cipher_Mode.

Definition at line 76 of file gcm_siv.cpp.

                                              {
   return 1;
}

valid_keylength()

bool Botan::SymmetricAlgorithm::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 143 of file sym_algo.h.

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

References key_spec().

Referenced by set_key().

valid_nonce_length()

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

finalvirtualinherited

Test if a nonce length is valid for this mode

Returns

true iff nonce_len is a valid length for the nonce

Implements Botan::Cipher_Mode.

Definition at line 84 of file gcm_siv.cpp.

                                                      {
   return len == 12;
}

Member Data Documentation

BS

size_t Botan::GCM_SIV_Mode::BS = 16

staticconstexprprotectedinherited

Definition at line 55 of file gcm_siv.h.

Referenced by ctr_xor(), and ideal_granularity().

MAX_INPUT_LEN

uint64_t Botan::GCM_SIV_Mode::MAX_INPUT_LEN = static_cast<uint64_t>(1) << 36

staticconstexprprotectedinherited

RFC 8452 limits both the plaintext and the AD to 2**36 bytes.

Definition at line 58 of file gcm_siv.h.

Referenced by set_associated_data_n().

---

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

• src/lib/modes/aead/gcm_siv/gcm_siv.h
• src/lib/modes/aead/gcm_siv/gcm_siv.cpp