Implement the session key exchange
This commit is contained in:
parent
08a7e44a96
commit
6ecea67718
10 changed files with 369 additions and 25 deletions
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@ -2,6 +2,8 @@
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#define AXOLOTL_ACCOUNT_HH_
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#include "axolotl/list.hh"
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#include "axolotl/crypto.hh"
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#include "axolotl/error.hh"
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#include <cstdint>
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@ -25,16 +27,21 @@ struct Account {
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LocalKey identity_key;
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LocalKey last_resort_one_time_key;
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List<LocalKey, MAX_ONE_TIME_KEYS> one_time_keys;
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ErrorCode last_error;
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/** Number of random bytes needed to create a new account */
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std::size_t new_account_random_length();
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/** Create a new account. Returns NOT_ENOUGH_RANDOM if the number of random
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* bytes is too small. */
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ErrorCode new_account(
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std::size_t new_account(
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uint8_t const * random, std::size_t random_length
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);
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LocalKey const * lookup_key(
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std::uint32_t id
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);
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/** The number of bytes needed to persist this account. */
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std::size_t pickle_length();
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@ -12,6 +12,9 @@
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef AXOLOTL_CRYPTO_HH_
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#define AXOLOTL_CRYPTO_HH_
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#include <cstdint>
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#include <cstddef>
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@ -141,3 +144,5 @@ void hkdf_sha256(
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);
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} // namespace axolotl
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#endif /* AXOLOTL_CRYPTO_HH_ */
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@ -10,6 +10,7 @@ enum struct ErrorCode {
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BAD_MESSAGE_VERSION = 3, /*!< The message version is unsupported */
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BAD_MESSAGE_FORMAT = 4, /*!< The message couldn't be decoded */
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BAD_MESSAGE_MAC = 5, /*!< The message couldn't be decrypted */
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BAD_MESSAGE_KEY_ID = 6, /*!< The message references an unknown key id */
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};
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} // namespace axolotl
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@ -12,6 +12,9 @@
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef AXOLOTL_LIST_HH_
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#define AXOLOTL_LIST_HH_
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#include <cstddef>
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namespace axolotl {
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@ -112,3 +115,5 @@ private:
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};
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} // namespace axolotl
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#endif /* AXOLOTL_LIST_HH_ */
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@ -88,6 +88,7 @@ struct PreKeyMessageReader {
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std::uint8_t const * message; std::size_t message_length;
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};
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/**
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* The length of the buffer needed to hold a message.
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*/
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@ -99,6 +100,7 @@ std::size_t encode_one_time_key_message_length(
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std::size_t message_length
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);
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/**
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* Writes the message headers into the output buffer.
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* Populates the writer struct with pointers into the output buffer.
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@ -5,14 +5,13 @@
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namespace axolotl {
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class Account;
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struct RemoteKey {
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std::uint32_t id;
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Curve25519PublicKey key;
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};
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struct RemoteKeys {
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};
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enum struct MessageType {
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PRE_KEY_MESSAGE = 0,
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@ -21,28 +20,34 @@ enum struct MessageType {
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struct Session {
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bool received_message;
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RemoteKey alice_identity_key;
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RemoteKey alice_base_key;
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RemoteKey bob_identity_key;
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RemoteKey bob_one_time_key;
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Session();
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Ratchet ratchet;
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ErrorCode last_error;
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void initialise_outbound_session_random_length();
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bool received_message;
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void initialise_outbound_session(
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RemoteKey alice_identity_key;
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Curve25519PublicKey alice_base_key;
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std::uint32_t bob_one_time_key_id;
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std::size_t new_outbound_session_random_length();
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std::size_t new_outbound_session(
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Account const & local_account,
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RemoteKey const & identity_key,
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Curve25519PublicKey const & identity_key,
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RemoteKey const & one_time_key,
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std::uint8_t const * random, std::size_t random_length
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);
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void initialise_inbound_session(
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std::size_t new_inbound_session(
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Account & local_account,
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std::uint8_t const * one_time_key_message, std::size_t message_length
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);
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void matches_inbound_session(
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bool matches_inbound_session(
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std::uint8_t const * one_time_key_message, std::size_t message_length
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);
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@ -26,7 +26,7 @@ static void derive_keys(
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std::uint8_t derived_secrets[80];
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axolotl::hkdf_sha256(
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key, key_length,
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NULL, 0,
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nullptr, 0,
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kdf_info, kdf_info_length,
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derived_secrets, sizeof(derived_secrets)
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);
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@ -198,15 +198,15 @@ void axolotl::decode_message(
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) {
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std::uint8_t const * pos = input;
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std::uint8_t const * end = input + input_length - mac_length;
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std::uint8_t const * unknown = NULL;
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std::uint8_t const * unknown = nullptr;
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if (pos == end) return;
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reader.version = *(pos++);
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reader.input = input;
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reader.input_length = input_length;
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reader.has_counter = false;
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reader.ratchet_key = NULL;
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reader.ciphertext = NULL;
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reader.ratchet_key = nullptr;
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reader.ciphertext = nullptr;
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while (pos != end) {
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pos = decode(
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@ -283,15 +283,15 @@ void axolotl::decode_one_time_key_message(
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) {
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std::uint8_t const * pos = input;
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std::uint8_t const * end = input + input_length;
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std::uint8_t const * unknown = NULL;
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std::uint8_t const * unknown = nullptr;
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if (pos == end) return;
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reader.version = *(pos++);
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reader.has_registration_id = false;
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reader.has_one_time_key_id = false;
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reader.identity_key = NULL;
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reader.base_key = NULL;
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reader.message = NULL;
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reader.identity_key = nullptr;
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reader.base_key = nullptr;
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reader.message = nullptr;
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while (pos != end) {
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pos = decode(
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@ -184,7 +184,7 @@ void axolotl::Ratchet::initialise_as_bob(
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std::uint8_t derived_secrets[64];
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axolotl::hkdf_sha256(
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shared_secret, shared_secret_length,
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NULL, 0,
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nullptr, 0,
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kdf_info.root_info, kdf_info.root_info_length,
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derived_secrets, sizeof(derived_secrets)
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);
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@ -203,7 +203,7 @@ void axolotl::Ratchet::initialise_as_alice(
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std::uint8_t derived_secrets[64];
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axolotl::hkdf_sha256(
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shared_secret, shared_secret_length,
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NULL, 0,
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nullptr, 0,
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kdf_info.root_info, kdf_info.root_info_length,
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derived_secrets, sizeof(derived_secrets)
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);
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@ -477,7 +477,7 @@ std::size_t axolotl::Ratchet::decrypt(
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return std::size_t(-1);
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}
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ReceiverChain * chain = NULL;
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ReceiverChain * chain = nullptr;
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for (axolotl::ReceiverChain & receiver_chain : receiver_chains) {
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if (0 == std::memcmp(
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receiver_chain.ratchet_key.public_key, reader.ratchet_key,
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319
src/session.cpp
Normal file
319
src/session.cpp
Normal file
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@ -0,0 +1,319 @@
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#include "axolotl/session.hh"
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#include "axolotl/cipher.hh"
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#include "axolotl/crypto.hh"
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#include "axolotl/account.hh"
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#include "axolotl/memory.hh"
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#include "axolotl/message.hh"
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#include <cstring>
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namespace {
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static const std::size_t KEY_LENGTH = 32;
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static const std::uint8_t PROTOCOL_VERSION = 0x3;
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static const std::uint8_t ROOT_KDF_INFO[] = "AXOLOTL_ROOT";
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static const std::uint8_t RATCHET_KDF_INFO[] = "AXOLOTL_RATCHET";
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static const std::uint8_t CIPHER_KDF_INFO[] = "AXOLOTL_KEYS";
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static const axolotl::CipherAesSha256 AXOLOTL_CIPHER(
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CIPHER_KDF_INFO, sizeof(CIPHER_KDF_INFO) -1
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);
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static const axolotl::KdfInfo AXOLOTL_KDF_INFO = {
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ROOT_KDF_INFO, sizeof(ROOT_KDF_INFO) - 1,
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RATCHET_KDF_INFO, sizeof(RATCHET_KDF_INFO) - 1
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};
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} // namespace
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axolotl::Session::Session(
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) : ratchet(AXOLOTL_KDF_INFO, AXOLOTL_CIPHER),
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last_error(axolotl::ErrorCode::SUCCESS),
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received_message(false),
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bob_one_time_key_id(0) {
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}
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std::size_t axolotl::Session::new_outbound_session_random_length() {
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return KEY_LENGTH;
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}
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std::size_t axolotl::Session::new_outbound_session(
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axolotl::Account const & local_account,
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axolotl::Curve25519PublicKey const & identity_key,
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axolotl::RemoteKey const & one_time_key,
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std::uint8_t const * random, std::size_t random_length
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) {
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if (random_length < new_outbound_session_random_length()) {
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last_error = axolotl::ErrorCode::NOT_ENOUGH_RANDOM;
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return std::size_t(-1);
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}
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Curve25519KeyPair base_key;
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axolotl::generate_key(random, base_key);
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received_message = false;
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alice_identity_key.id = local_account.identity_key.id;
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alice_identity_key.key = local_account.identity_key.key;
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alice_base_key = base_key;
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bob_one_time_key_id = one_time_key.id;
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std::uint8_t shared_secret[160];
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std::memset(shared_secret, 0xFF, 32);
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axolotl::curve25519_shared_secret(
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);
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axolotl::curve25519_shared_secret(
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base_key, identity_key, shared_secret + 64
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);
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axolotl::curve25519_shared_secret(
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);
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axolotl::curve25519_shared_secret(
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base_key, one_time_key.key, shared_secret + 128
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);
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axolotl::unset(base_key);
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axolotl::unset(shared_secret);
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return std::size_t(0);
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}
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namespace {
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bool check_message_fields(
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axolotl::PreKeyMessageReader & reader
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) {
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bool ok = true;
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ok = ok && reader.identity_key;
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ok = ok && reader.identity_key_length == KEY_LENGTH;
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ok = ok && reader.message;
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ok = ok && reader.base_key;
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ok = ok && reader.base_key_length == KEY_LENGTH;
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ok = ok && reader.has_one_time_key_id;
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ok = ok && reader.has_registration_id;
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return ok;
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}
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} // namespace
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std::size_t axolotl::Session::new_inbound_session(
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axolotl::Account & local_account,
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std::uint8_t const * one_time_key_message, std::size_t message_length
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) {
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axolotl::PreKeyMessageReader reader;
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decode_one_time_key_message(reader, one_time_key_message, message_length);
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if (!check_message_fields(reader)) {
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last_error = axolotl::ErrorCode::BAD_MESSAGE_FORMAT;
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return std::size_t(-1);
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}
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alice_identity_key.id = reader.registration_id;
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std::memcpy(alice_identity_key.key.public_key, reader.identity_key, 32);
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std::memcpy(alice_base_key.public_key, reader.base_key, 32);
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bob_one_time_key_id = reader.one_time_key_id;
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axolotl::LocalKey const * bob_one_time_key = local_account.lookup_key(
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bob_one_time_key_id
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);
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last_error = axolotl::ErrorCode::BAD_MESSAGE_KEY_ID;
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return std::size_t(-1);
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}
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std::uint8_t shared_secret[160];
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std::memset(shared_secret, 0xFF, 32);
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axolotl::curve25519_shared_secret(
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);
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axolotl::curve25519_shared_secret(
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local_account.identity_key.key, alice_base_key, shared_secret + 64
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);
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axolotl::curve25519_shared_secret(
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);
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axolotl::curve25519_shared_secret(
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bob_one_time_key->key, alice_base_key, shared_secret + 128
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);
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return std::size_t(0);
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}
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bool axolotl::Session::matches_inbound_session(
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std::uint8_t const * one_time_key_message, std::size_t message_length
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) {
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axolotl::PreKeyMessageReader reader;
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decode_one_time_key_message(reader, one_time_key_message, message_length);
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if (!check_message_fields(reader)) {
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return false;
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}
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bool same = true;
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same = same && 0 == std::memcmp(
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reader.identity_key, alice_identity_key.key.public_key, KEY_LENGTH
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);
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same = same && 0 == std::memcmp(
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reader.base_key, alice_base_key.public_key, KEY_LENGTH
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);
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same = same && reader.one_time_key_id == bob_one_time_key_id;
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same = same && reader.registration_id == alice_identity_key.id;
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return same;
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}
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axolotl::MessageType axolotl::Session::encrypt_message_type() {
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if (received_message) {
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return axolotl::MessageType::MESSAGE;
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} else {
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return axolotl::MessageType::PRE_KEY_MESSAGE;
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}
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}
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std::size_t axolotl::Session::encrypt_message_length(
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std::size_t plaintext_length
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) {
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std::size_t message_length = ratchet.encrypt_output_length(
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plaintext_length
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);
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if (received_message) {
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return message_length;
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}
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return encode_one_time_key_message_length(
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alice_identity_key.id,
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bob_one_time_key_id,
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KEY_LENGTH,
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KEY_LENGTH,
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message_length
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);
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}
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std::size_t axolotl::Session::encrypt_random_length() {
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return ratchet.encrypt_random_length();
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}
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std::size_t axolotl::Session::encrypt(
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std::uint8_t const * plaintext, std::size_t plaintext_length,
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std::uint8_t const * random, std::size_t random_length,
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std::uint8_t * message, std::size_t message_length
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) {
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if (message_length < encrypt_message_length(plaintext_length)) {
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last_error = axolotl::ErrorCode::OUTPUT_BUFFER_TOO_SMALL;
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return std::size_t(-1);
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}
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std::uint8_t * message_body;
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std::size_t message_body_length = ratchet.encrypt_output_length(
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plaintext_length
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);
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if (received_message) {
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message_body = message;
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} else {
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axolotl::PreKeyMessageWriter writer;
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encode_one_time_key_message(
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writer,
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PROTOCOL_VERSION,
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alice_identity_key.id,
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bob_one_time_key_id,
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KEY_LENGTH,
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KEY_LENGTH,
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message_body_length,
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message
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);
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std::memcpy(
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writer.identity_key, alice_identity_key.key.public_key, KEY_LENGTH
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);
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std::memcpy(
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writer.base_key, alice_base_key.public_key, KEY_LENGTH
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);
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message_body = writer.message;
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}
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std::size_t result = ratchet.encrypt(
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plaintext, plaintext_length,
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random, random_length,
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message_body, message_body_length
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);
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if (result == std::size_t(-1)) {
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last_error = ratchet.last_error;
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ratchet.last_error = axolotl::ErrorCode::SUCCESS;
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}
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return result;
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}
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|
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|
||||
std::size_t axolotl::Session::decrypt_max_plaintext_length(
|
||||
MessageType message_type,
|
||||
std::uint8_t const * message, std::size_t message_length
|
||||
) {
|
||||
std::uint8_t const * message_body;
|
||||
std::size_t message_body_length;
|
||||
if (message_type == axolotl::MessageType::MESSAGE) {
|
||||
message_body = message;
|
||||
message_body_length = message_length;
|
||||
} else {
|
||||
axolotl::PreKeyMessageReader reader;
|
||||
decode_one_time_key_message(reader, message, message_length);
|
||||
if (!reader.message) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_FORMAT;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
message_body = reader.message;
|
||||
message_body_length = reader.message_length;
|
||||
}
|
||||
|
||||
std::size_t result = ratchet.decrypt_max_plaintext_length(
|
||||
message_body, message_body_length
|
||||
);
|
||||
|
||||
if (result == std::size_t(-1)) {
|
||||
last_error = ratchet.last_error;
|
||||
ratchet.last_error = axolotl::ErrorCode::SUCCESS;
|
||||
}
|
||||
return result;
|
||||
}
|
||||
|
||||
|
||||
std::size_t axolotl::Session::decrypt(
|
||||
axolotl::MessageType message_type,
|
||||
std::uint8_t const * message, std::size_t message_length,
|
||||
std::uint8_t * plaintext, std::size_t max_plaintext_length
|
||||
) {
|
||||
std::uint8_t const * message_body;
|
||||
std::size_t message_body_length;
|
||||
if (message_type == axolotl::MessageType::MESSAGE) {
|
||||
message_body = message;
|
||||
message_body_length = message_length;
|
||||
} else {
|
||||
axolotl::PreKeyMessageReader reader;
|
||||
decode_one_time_key_message(reader, message, message_length);
|
||||
if (!reader.message) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_FORMAT;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
message_body = reader.message;
|
||||
message_body_length = reader.message_length;
|
||||
}
|
||||
|
||||
std::size_t result = ratchet.decrypt(
|
||||
message_body, message_body_length, plaintext, max_plaintext_length
|
||||
);
|
||||
|
||||
if (result == std::size_t(-1)) {
|
||||
last_error = ratchet.last_error;
|
||||
ratchet.last_error = axolotl::ErrorCode::SUCCESS;
|
||||
}
|
||||
return result;
|
||||
}
|
Loading…
Reference in a new issue