diff options
Diffstat (limited to 'include/axolotl')
-rw-r--r-- | include/axolotl/axolotl.hh | 114 | ||||
-rw-r--r-- | include/axolotl/crypto.hh | 90 | ||||
-rw-r--r-- | include/axolotl/list.hh | 100 | ||||
-rw-r--r-- | include/axolotl/message.hh | 62 |
4 files changed, 366 insertions, 0 deletions
diff --git a/include/axolotl/axolotl.hh b/include/axolotl/axolotl.hh new file mode 100644 index 0000000..ead52fc --- /dev/null +++ b/include/axolotl/axolotl.hh @@ -0,0 +1,114 @@ + +#include "axolotl/crypto.hh" +#include "axolotl/list.hh" + +namespace axolotl { + +typedef std::uint8_t SharedKey[32]; + + +struct ChainKey { + std::uint32_t index; + SharedKey key; +}; + + +struct MessageKey { + std::uint32_t index; + Aes256Key cipher_key; + SharedKey mac_key; + Aes256Iv iv; +}; + + +struct SenderChain { + Curve25519KeyPair ratchet_key; + ChainKey chain_key; +}; + + +struct ReceiverChain { + Curve25519PublicKey ratchet_key; + ChainKey chain_key; +}; + + +struct SkippedMessageKey { + Curve25519PublicKey ratchet_key; + MessageKey message_key; +}; + + +enum struct ErrorCode { + SUCCESS = 0, /*!< There wasn't an error */ + NOT_ENOUGH_RANDOM = 1, /*!< Not enough entropy was supplied */ + OUTPUT_BUFFER_TOO_SMALL = 2, /*!< Supplied output buffer is too small */ + BAD_MESSAGE_VERSION = 3, /*!< The message version is unsupported */ + BAD_MESSAGE_FORMAT = 4, /*!< The message couldn't be decoded */ + BAD_MESSAGE_MAC = 5, /*!< The message couldn't be decrypted */ +}; + + +static std::size_t const MAX_RECEIVER_CHAINS = 5; +static std::size_t const MAX_SKIPPED_MESSAGE_KEYS = 40; + + +struct KdfInfo { + std::uint8_t const * root_info; + std::size_t root_info_length; + std::uint8_t const * ratchet_info; + std::size_t ratchet_info_length; + std::uint8_t const * message_info; + std::size_t message_info_length; +}; + + +struct Session { + + Session( + KdfInfo const & kdf_info + ); + + /** A pair of string to feed into the KDF identifing the application */ + KdfInfo kdf_info; + /** The last error that happened encypting or decrypting a message */ + ErrorCode last_error; + SharedKey root_key; + List<SenderChain, 1> sender_chain; + List<ReceiverChain, MAX_RECEIVER_CHAINS> receiver_chains; + List<SkippedMessageKey, MAX_SKIPPED_MESSAGE_KEYS> skipped_message_keys; + + void initialise_as_bob( + std::uint8_t const * shared_secret, std::size_t shared_secret_length, + Curve25519PublicKey const & their_ratchet_key + ); + + void initialise_as_alice( + std::uint8_t const * shared_secret, std::size_t shared_secret_length, + Curve25519KeyPair const & our_ratchet_key + ); + + std::size_t encrypt_max_output_length( + std::size_t plaintext_length + ); + + std::size_t encrypt_random_length(); + + std::size_t encrypt( + std::uint8_t const * plaintext, std::size_t plaintext_length, + std::uint8_t const * random, std::size_t random_length, + std::uint8_t * output, std::size_t max_output_length + ); + + std::size_t decrypt_max_plaintext_length( + std::size_t input_length + ); + + std::size_t decrypt( + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * plaintext, std::size_t max_plaintext_length + ); +}; + + +} // namespace axololt diff --git a/include/axolotl/crypto.hh b/include/axolotl/crypto.hh new file mode 100644 index 0000000..f1e81ac --- /dev/null +++ b/include/axolotl/crypto.hh @@ -0,0 +1,90 @@ +#include <cstdint> +#include <cstddef> + +namespace axolotl { + + +struct Curve25519PublicKey { + static const int LENGTH = 32; + std::uint8_t public_key[32]; +}; + + +struct Curve25519KeyPair : public Curve25519PublicKey { + std::uint8_t private_key[32]; +}; + + +void generate_key( + std::uint8_t const * random_32_bytes, + Curve25519KeyPair & key_pair +); + + +const std::size_t CURVE25519_SHARED_SECRET_LENGTH = 32; + + +void curve25519_shared_secret( + Curve25519KeyPair const & our_key, + Curve25519PublicKey const & their_key, + std::uint8_t * output +); + + +struct Aes256Key { + static const int LENGTH = 32; + std::uint8_t key[32]; +}; + + +struct Aes256Iv { + static const int LENGTH = 16; + std::uint8_t iv[16]; +}; + + +std::size_t aes_encrypt_cbc_length( + std::size_t input_length +); + + +void aes_encrypt_cbc( + Aes256Key const & key, + Aes256Iv const & iv, + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * output +); + + +std::size_t aes_decrypt_cbc( + Aes256Key const & key, + Aes256Iv const & iv, + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * output +); + + +void sha256( + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * output +); + + +const std::size_t HMAC_SHA256_OUTPUT_LENGTH = 32; + + +void hmac_sha256( + std::uint8_t const * key, std::size_t key_length, + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * output +); + + +void hkdf_sha256( + std::uint8_t const * input, std::size_t input_length, + std::uint8_t const * info, std::size_t info_length, + std::uint8_t const * salt, std::size_t salt_length, + std::uint8_t * output, std::size_t output_length +); + +} // namespace axolotl diff --git a/include/axolotl/list.hh b/include/axolotl/list.hh new file mode 100644 index 0000000..4c87630 --- /dev/null +++ b/include/axolotl/list.hh @@ -0,0 +1,100 @@ +#include <cstddef> + +namespace axolotl { + +template<typename T, std::size_t max_size> +class List { +public: + List() : _end(_data) {} + + typedef T * iterator; + typedef T const * const_iterator; + + T * begin() { return _data; } + T * end() { return _end; } + T const * begin() const { return _data; } + T const * end() const { return _end; } + + /** + * Is the list empty? + */ + bool empty() const { return _end == _data; } + + /** + * The number of items in the list. + */ + std::size_t size() const { return _end - _data; } + + T & operator[](std::size_t index) { return _data[index]; } + + T const & operator[](std::size_t index) const { return _data[index]; } + + /** + * Erase the item from the list at the given position. + */ + void erase(T * pos) { + --_end; + while (pos != _end) { + *pos = *(pos + 1); + ++pos; + } + } + + /** + * Make space for an item in the list at a given position. + * If inserting the item makes the list longer than max_size then + * the end of the list is discarded. + * Returns the where the item is inserted. + */ + T * insert(T * pos) { + if (_end != _data + max_size) { + ++_end; + } else if (pos == _end) { + --pos; + } + T * tmp = pos; + while (tmp != _end - 1) { + *(tmp + 1) = *tmp; + ++tmp; + } + return pos; + } + + /** + * Make space for an item in the list at the start of the list + */ + T * insert() { return insert(begin()); } + + /** + * Insert an item into the list at a given position. + * If inserting the item makes the list longer than max_size then + * the end of the list is discarded. + * Returns the where the item is inserted. + */ + T * insert(T * pos, T const & value) { + pos = insert(pos); + *pos = value; + return pos; + } + + List<T, max_size> & operator=(List<T, max_size> const & other) { + if (this = &other) { + return *this; + } + T * this_pos = _data; + T * const other_pos = other._data; + while (other_pos != other._end) { + *this_pos = *other; + ++this_pos; + ++other_pos; + } + _end = this_pos; + return *this; + } + +private: + T * _end; + T _data[max_size]; +}; + +} // namespace axolotl diff --git a/include/axolotl/message.hh b/include/axolotl/message.hh new file mode 100644 index 0000000..ac4b3e0 --- /dev/null +++ b/include/axolotl/message.hh @@ -0,0 +1,62 @@ +#include <cstddef> +#include <cstdint> + + +namespace axolotl { + +/** + * The length of the buffer needed to hold a message. + */ +std::size_t encode_message_length( + std::uint32_t counter, + std::size_t ratchet_key_length, + std::size_t ciphertext_length, + std::size_t mac_length +); + + +struct MessageWriter { + std::size_t body_length; + std::uint8_t * ratchet_key; + std::uint8_t * ciphertext; + std::uint8_t * mac; +}; + + +struct MessageReader { + std::size_t body_length; + std::uint8_t version; + std::uint32_t counter; + std::size_t ratchet_key_length; + std::size_t ciphertext_length; + std::uint8_t const * ratchet_key; + std::uint8_t const * ciphertext; + std::uint8_t const * mac; +}; + + +/** + * Writes the message headers into the output buffer. + * Returns a writer struct populated with pointers into the output buffer. + */ +MessageWriter encode_message( + std::uint8_t version, + std::uint32_t counter, + std::size_t ratchet_key_length, + std::size_t ciphertext_length, + std::uint8_t * output +); + + +/** + * Reads the message headers from the input buffer. + * Returns a reader struct populated with pointers into the input buffer. + * On failure the returned body_length will be 0. + */ +MessageReader decode_message( + std::uint8_t const * input, std::size_t input_length, + std::size_t mac_length +); + + +} // namespace axolotl |