diff options
Diffstat (limited to 'include/axolotl')
| -rw-r--r-- | include/axolotl/axolotl.hh | 167 | ||||
| -rw-r--r-- | include/axolotl/crypto.hh | 123 | ||||
| -rw-r--r-- | include/axolotl/list.hh | 114 | ||||
| -rw-r--r-- | include/axolotl/memory.hh | 17 | ||||
| -rw-r--r-- | include/axolotl/message.hh | 76 |
5 files changed, 497 insertions, 0 deletions
diff --git a/include/axolotl/axolotl.hh b/include/axolotl/axolotl.hh new file mode 100644 index 0000000..9d7ff9a --- /dev/null +++ b/include/axolotl/axolotl.hh @@ -0,0 +1,167 @@ +/* Copyright 2015 OpenMarket Ltd + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#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 some strings identifing the application to feed into the KDF. */ + KdfInfo kdf_info; + + /** The last error that happened encypting or decrypting a message. */ + ErrorCode last_error; + + /** The root key is used to generate chain keys from the ephemeral keys. + * A new root_key derived each time a chain key is derived. */ + SharedKey root_key; + + /** The sender chain is used to send messages. Each time a new ephemeral + * key is received from the remote server we generate a new sender chain + * with a new empheral key when we next send a message. */ + List<SenderChain, 1> sender_chain; + + /** The receiver chain is used to decrypt recieved messages. We store the + * last few chains so we can decrypt any out of order messages we haven't + * received yet. */ + List<ReceiverChain, MAX_RECEIVER_CHAINS> receiver_chains; + + /** List of message keys we've skipped over when advancing the receiver + * chain. */ + List<SkippedMessageKey, MAX_SKIPPED_MESSAGE_KEYS> skipped_message_keys; + + /** Initialise the session using a shared secret and the public part of the + * remote's first ratchet key */ + void initialise_as_bob( + std::uint8_t const * shared_secret, std::size_t shared_secret_length, + Curve25519PublicKey const & their_ratchet_key + ); + + /** Intialise the session using a shared secret and the public/private key + * pair for the first ratchet key */ + void initialise_as_alice( + std::uint8_t const * shared_secret, std::size_t shared_secret_length, + Curve25519KeyPair const & our_ratchet_key + ); + + /** The maximum number of bytes of output the encrypt method will write for + * a given message length. */ + std::size_t encrypt_max_output_length( + std::size_t plaintext_length + ); + + /** The number of bytes of random data the encrypt method will need to + * encrypt a message. This will be 32 bytes if the session needs to + * generate a new ephemeral key, or will be 0 bytes otherwise.*/ + std::size_t encrypt_random_length(); + + /** Encrypt some plaintext. Returns the length of the encrypted message + * or std::size_t(-1) on failure. On failure last_error will be set with + * an error code. The last_error will be NOT_ENOUGH_RANDOM if the number + * of random bytes is too small. The last_error will be + * OUTPUT_BUFFER_TOO_SMALL if the output buffer is too small. */ + 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 + ); + + /** An upper bound on the number of bytes of plaintext the decrypt method + * will write for a given input message length. */ + std::size_t decrypt_max_plaintext_length( + std::size_t input_length + ); + + /** Decrypt a message. Returns the length of the decrypted plaintext or + * std::size_t(-1) on failure. On failure last_error will be set with an + * error code. The last_error will be OUTPUT_BUFFER_TOO_SMALL if the + * plaintext buffer is too small. The last_error will be + * BAD_MESSAGE_VERSION if the message was encrypted with an unsupported + * version of the protocol. The last_error will be BAD_MESSAGE_FORMAT if + * the message headers could not be decoded. The last_error will be + * BAD_MESSAGE_MAC if the message could not be verified */ + 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 axolotl diff --git a/include/axolotl/crypto.hh b/include/axolotl/crypto.hh new file mode 100644 index 0000000..162099f --- /dev/null +++ b/include/axolotl/crypto.hh @@ -0,0 +1,123 @@ +/* Copyright 2015 OpenMarket Ltd + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +#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]; +}; + + +/** Generate a curve25519 key pair from 32 random bytes. */ +void generate_key( + std::uint8_t const * random_32_bytes, + Curve25519KeyPair & key_pair +); + + +const std::size_t CURVE25519_SHARED_SECRET_LENGTH = 32; + + +/** Create a shared secret using our private key and their public key. + * The output buffer must be at least 32 bytes long. */ +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]; +}; + + +/** The length of output the aes_encrypt_cbc function will write */ +std::size_t aes_encrypt_cbc_length( + std::size_t input_length +); + + +/** Encrypts the input using AES256 in CBC mode with PKCS#7 padding. + * The output buffer must be big enough to hold the output including padding */ +void aes_encrypt_cbc( + Aes256Key const & key, + Aes256Iv const & iv, + std::uint8_t const * input, std::size_t input_length, + std::uint8_t * output +); + + +/** Decrypts the input using AES256 in CBC mode. The output buffer must be at + * least the same size as the input buffer. Returns the length of the plaintext + * without padding on success or std::size_t(-1) if the padding is invalid. + */ +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 +); + + +/** Computes SHA-256 of the input. The output buffer must be a least 32 + * bytes long. */ +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; + + +/** HMAC: Keyed-Hashing for Message Authentication + * http://tools.ietf.org/html/rfc2104 + * Computes HMAC-SHA-256 of the input for the key. The output buffer must + * be at least 32 bytes long. */ +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 +); + + +/** HMAC-based Key Derivation Function (HKDF) + * https://tools.ietf.org/html/rfc5869 + * Derives key material from the input bytes. */ +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..d1407b8 --- /dev/null +++ b/include/axolotl/list.hh @@ -0,0 +1,114 @@ +/* Copyright 2015 OpenMarket Ltd + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +#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/memory.hh b/include/axolotl/memory.hh new file mode 100644 index 0000000..7749c54 --- /dev/null +++ b/include/axolotl/memory.hh @@ -0,0 +1,17 @@ +#include <cstddef> + +namespace axolotl { + +/** Clear the memory held in the buffer */ +void unset( + volatile void * buffer, std::size_t buffer_length +); + +/** Clear the memory backing an object */ +template<typename T> +void unset(T & value) { + unset(reinterpret_cast<volatile void *>(&value), sizeof(T)); +} + + +} // namespace axolotl diff --git a/include/axolotl/message.hh b/include/axolotl/message.hh new file mode 100644 index 0000000..5cd4211 --- /dev/null +++ b/include/axolotl/message.hh @@ -0,0 +1,76 @@ +/* Copyright 2015 OpenMarket Ltd + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +#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 |