mirror of https://git.matrix.org/git/olm.git
Move AES specific details behind a cipher interface
Mark Haines
parent
8161b56ff0
commit
816435a860
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@ -0,0 +1,127 @@
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/* Copyright 2015 OpenMarket Ltd
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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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_CIPHER_HH_
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#define AXOLOTL_CIPHER_HH_
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#include <cstdint>
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namespace axolotl {
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class Cipher {
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public:
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virtual ~Cipher();
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/**
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* Returns the length of the message authentication code that will be
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* appended to the output.
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*/
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virtual std::size_t mac_length() const = 0;
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/**
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* Returns the length of cipher-text for a given length of plain-text.
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*/
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virtual std::size_t encrypt_ciphertext_length(
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std::size_t plaintext_length
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) const = 0;
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/*
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* Encrypts the plain-text into the output buffer and authenticates the
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* contents of the output buffer covering both cipher-text and any other
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* associated data in the output buffer.
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*
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* |---------------------------------------output_length-->|
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* output |--ciphertext_length-->| |---mac_length-->|
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* ciphertext
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*
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* Returns std::size_t(-1) if the length of the cipher-text or the output
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* buffer is too small. Otherwise returns the length of the output buffer.
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*/
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virtual std::size_t encrypt(
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std::uint8_t const * key, std::size_t key_length,
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std::uint8_t const * plaintext, std::size_t plaintext_length,
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std::uint8_t * ciphertext, std::size_t ciphertext_length,
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std::uint8_t * output, std::size_t output_length
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) const = 0;
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/**
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* Returns the maximum length of plain-text that a given length of
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* cipher-text can contain.
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*/
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virtual std::size_t decrypt_max_plaintext_length(
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std::size_t ciphertext_length
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) const = 0;
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/**
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* Authenticates the input and decrypts the cipher-text into the plain-text
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* buffer.
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*
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* |----------------------------------------input_length-->|
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* input |--ciphertext_length-->| |---mac_length-->|
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* ciphertext
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*
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* Returns std::size_t(-1) if the length of the plain-text buffer is too
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* small or if the authentication check fails. Otherwise returns the length
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* of the plain text.
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*/
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virtual std::size_t decrypt(
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std::uint8_t const * key, std::size_t key_length,
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std::uint8_t const * input, std::size_t input_length,
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std::uint8_t const * ciphertext, std::size_t ciphertext_length,
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std::uint8_t * plaintext, std::size_t max_plaintext_length
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) const = 0;
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};
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class CipherAesSha256 : public Cipher {
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public:
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CipherAesSha256(
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std::uint8_t const * kdf_info, std::size_t kdf_info_length
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);
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virtual std::size_t mac_length() const;
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virtual std::size_t encrypt_ciphertext_length(
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std::size_t plaintext_length
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) const;
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virtual std::size_t encrypt(
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std::uint8_t const * key, std::size_t key_length,
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std::uint8_t const * plaintext, std::size_t plaintext_length,
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std::uint8_t * ciphertext, std::size_t ciphertext_length,
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std::uint8_t * output, std::size_t output_length
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) const;
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virtual std::size_t decrypt_max_plaintext_length(
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std::size_t ciphertext_length
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) const;
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virtual std::size_t decrypt(
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std::uint8_t const * key, std::size_t key_length,
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std::uint8_t const * input, std::size_t input_length,
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std::uint8_t const * ciphertext, std::size_t ciphertext_length,
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std::uint8_t * plaintext, std::size_t max_plaintext_length
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) const;
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private:
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std::uint8_t const * kdf_info;
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std::size_t kdf_info_length;
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};
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} // namespace
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#endif /* AXOLOTL_CIPHER_HH_ */
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@ -92,7 +92,7 @@ public:
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}
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List<T, max_size> & operator=(List<T, max_size> const & other) {
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if (this = &other) {
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if (this == &other) {
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return *this;
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}
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T * this_pos = _data;
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@ -30,22 +30,17 @@ std::size_t encode_message_length(
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struct MessageWriter {
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std::size_t body_length;
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std::uint8_t * ratchet_key;
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std::uint8_t * ciphertext;
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std::uint8_t * mac;
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};
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struct MessageReader {
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std::size_t body_length;
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std::uint8_t version;
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std::uint32_t counter;
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std::size_t ratchet_key_length;
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std::size_t ciphertext_length;
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std::uint8_t const * ratchet_key;
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std::uint8_t const * ciphertext;
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std::uint8_t const * mac;
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std::uint8_t const * input; std::size_t input_length;
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std::uint8_t const * ratchet_key; std::size_t ratchet_key_length;
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std::uint8_t const * ciphertext; std::size_t ciphertext_length;
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};
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@ -53,7 +48,9 @@ struct MessageReader {
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* Writes the message headers into the output buffer.
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* Returns a writer struct populated with pointers into the output buffer.
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*/
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MessageWriter encode_message(
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void encode_message(
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MessageWriter & writer,
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std::uint8_t version,
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std::uint32_t counter,
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std::size_t ratchet_key_length,
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@ -64,10 +61,11 @@ MessageWriter encode_message(
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/**
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* Reads the message headers from the input buffer.
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* Returns a reader struct populated with pointers into the input buffer.
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* On failure the returned body_length will be 0.
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* Populates the reader struct with pointers into the input buffer.
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* On failure returns std::size_t(-1).
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*/
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MessageReader decode_message(
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std::size_t decode_message(
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MessageReader & reader,
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std::uint8_t const * input, std::size_t input_length,
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std::size_t mac_length
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);
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@ -18,6 +18,8 @@
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namespace axolotl {
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class Cipher;
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typedef std::uint8_t SharedKey[32];
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@ -29,9 +31,7 @@ struct ChainKey {
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struct MessageKey {
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std::uint32_t index;
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Aes256Key cipher_key;
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SharedKey mac_key;
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Aes256Iv iv;
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SharedKey key;
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};
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@ -72,21 +72,23 @@ struct KdfInfo {
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std::size_t root_info_length;
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std::uint8_t const * ratchet_info;
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std::size_t ratchet_info_length;
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std::uint8_t const * message_info;
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std::size_t message_info_length;
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};
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struct Session {
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Session(
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KdfInfo const & kdf_info
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KdfInfo const & kdf_info,
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Cipher const & ratchet_cipher
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);
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/** A some strings identifing the application to feed into the KDF. */
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const KdfInfo &kdf_info;
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/** A some strings identifying the application to feed into the KDF. */
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KdfInfo const & kdf_info;
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/** The last error that happened encypting or decrypting a message. */
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/** The AEAD cipher to use for encrypting messages. */
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Cipher const & ratchet_cipher;
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/** The last error that happened encrypting or decrypting a message. */
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ErrorCode last_error;
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/** The root key is used to generate chain keys from the ephemeral keys.
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@ -98,7 +100,7 @@ struct Session {
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* with a new empheral key when we next send a message. */
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List<SenderChain, 1> sender_chain;
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/** The receiver chain is used to decrypt recieved messages. We store the
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/** The receiver chain is used to decrypt received messages. We store the
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* last few chains so we can decrypt any out of order messages we haven't
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* received yet. */
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List<ReceiverChain, MAX_RECEIVER_CHAINS> receiver_chains;
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@ -114,7 +116,7 @@ struct Session {
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Curve25519PublicKey const & their_ratchet_key
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);
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/** Intialise the session using a shared secret and the public/private key
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/** Initialise the session using a shared secret and the public/private key
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* pair for the first ratchet key */
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void initialise_as_alice(
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std::uint8_t const * shared_secret, std::size_t shared_secret_length,
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@ -150,7 +152,7 @@ struct Session {
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* generate a new ephemeral key, or will be 0 bytes otherwise.*/
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std::size_t encrypt_random_length();
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/** Encrypt some plaintext. Returns the length of the encrypted message
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/** Encrypt some plain-text. Returns the length of the encrypted message
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* or std::size_t(-1) on failure. On failure last_error will be set with
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* an error code. The last_error will be NOT_ENOUGH_RANDOM if the number
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* of random bytes is too small. The last_error will be
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@ -161,16 +163,16 @@ struct Session {
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std::uint8_t * output, std::size_t max_output_length
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);
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/** An upper bound on the number of bytes of plaintext the decrypt method
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/** An upper bound on the number of bytes of plain-text the decrypt method
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* will write for a given input message length. */
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std::size_t decrypt_max_plaintext_length(
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std::size_t input_length
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);
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/** Decrypt a message. Returns the length of the decrypted plaintext or
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/** Decrypt a message. Returns the length of the decrypted plain-text or
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* std::size_t(-1) on failure. On failure last_error will be set with an
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* error code. The last_error will be OUTPUT_BUFFER_TOO_SMALL if the
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* plaintext buffer is too small. The last_error will be
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* plain-text buffer is too small. The last_error will be
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* BAD_MESSAGE_VERSION if the message was encrypted with an unsupported
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* version of the protocol. The last_error will be BAD_MESSAGE_FORMAT if
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* the message headers could not be decoded. The last_error will be
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@ -0,0 +1,125 @@
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#include "axolotl/cipher.hh"
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#include "axolotl/crypto.hh"
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#include "axolotl/memory.hh"
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#include <cstring>
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axolotl::Cipher::~Cipher() {
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}
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namespace {
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static const std::size_t SHA256_LENGTH = 32;
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struct DerivedKeys {
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axolotl::Aes256Key aes_key;
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std::uint8_t mac_key[SHA256_LENGTH];
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axolotl::Aes256Iv aes_iv;
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};
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static void derive_keys(
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std::uint8_t const * kdf_info, std::size_t kdf_info_length,
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std::uint8_t const * key, std::size_t key_length,
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DerivedKeys & keys
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) {
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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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kdf_info, kdf_info_length,
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derived_secrets, sizeof(derived_secrets)
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);
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std::memcpy(keys.aes_key.key, derived_secrets, 32);
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std::memcpy(keys.mac_key, derived_secrets + 32, 32);
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std::memcpy(keys.aes_iv.iv, derived_secrets + 64, 16);
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axolotl::unset(derived_secrets);
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}
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static const std::size_t MAC_LENGTH = 8;
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} // namespace
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axolotl::CipherAesSha256::CipherAesSha256(
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std::uint8_t const * kdf_info, std::size_t kdf_info_length
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) : kdf_info(kdf_info), kdf_info_length(kdf_info_length) {
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}
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std::size_t axolotl::CipherAesSha256::mac_length() const {
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return MAC_LENGTH;
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}
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std::size_t axolotl::CipherAesSha256::encrypt_ciphertext_length(
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std::size_t plaintext_length
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) const {
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return axolotl::aes_encrypt_cbc_length(plaintext_length);
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}
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std::size_t axolotl::CipherAesSha256::encrypt(
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std::uint8_t const * key, std::size_t key_length,
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std::uint8_t const * plaintext, std::size_t plaintext_length,
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std::uint8_t * ciphertext, std::size_t ciphertext_length,
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std::uint8_t * output, std::size_t output_length
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) const {
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if (encrypt_ciphertext_length(plaintext_length) < ciphertext_length) {
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return std::size_t(-1);
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}
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struct DerivedKeys keys;
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std::uint8_t mac[SHA256_LENGTH];
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derive_keys(kdf_info, kdf_info_length, key, key_length, keys);
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axolotl::aes_encrypt_cbc(
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keys.aes_key, keys.aes_iv, plaintext, plaintext_length, ciphertext
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);
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axolotl::hmac_sha256(
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keys.mac_key, SHA256_LENGTH, output, output_length - MAC_LENGTH, mac
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);
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std::memcpy(output + output_length - MAC_LENGTH, mac, MAC_LENGTH);
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axolotl::unset(keys);
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return output_length;
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}
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std::size_t axolotl::CipherAesSha256::decrypt_max_plaintext_length(
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std::size_t ciphertext_length
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) const {
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return ciphertext_length;
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}
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std::size_t axolotl::CipherAesSha256::decrypt(
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std::uint8_t const * key, std::size_t key_length,
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std::uint8_t const * input, std::size_t input_length,
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std::uint8_t const * ciphertext, std::size_t ciphertext_length,
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std::uint8_t * plaintext, std::size_t max_plaintext_length
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) const {
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DerivedKeys keys;
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std::uint8_t mac[SHA256_LENGTH];
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derive_keys(kdf_info, kdf_info_length, key, key_length, keys);
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axolotl::hmac_sha256(
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keys.mac_key, SHA256_LENGTH, input, input_length - MAC_LENGTH, mac
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);
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std::uint8_t const * input_mac = input + input_length - MAC_LENGTH;
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if (!axolotl::is_equal(input_mac, mac, MAC_LENGTH)) {
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axolotl::unset(keys);
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return std::size_t(-1);
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}
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std::size_t plaintext_length = axolotl::aes_decrypt_cbc(
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keys.aes_key, keys.aes_iv, ciphertext, ciphertext_length, plaintext
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);
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axolotl::unset(keys);
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return plaintext_length;
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}
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@ -94,55 +94,52 @@ std::size_t axolotl::encode_message_length(
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length += 1 + varstring_length(ratchet_key_length);
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length += 1 + varint_length(counter);
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length += 1 + varstring_length(ciphertext_length);
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return length + mac_length;
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length += mac_length;
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return length;
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}
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axolotl::MessageWriter axolotl::encode_message(
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void axolotl::encode_message(
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axolotl::MessageWriter & writer,
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std::uint8_t version,
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std::uint32_t counter,
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std::size_t ratchet_key_length,
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std::size_t ciphertext_length,
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std::uint8_t * output
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) {
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axolotl::MessageWriter result;
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std::uint8_t * pos = output;
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*(pos++) = version;
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*(pos++) = COUNTER_TAG;
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pos = varint_encode(pos, counter);
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*(pos++) = RATCHET_KEY_TAG;
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pos = varint_encode(pos, ratchet_key_length);
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result.ratchet_key = pos;
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writer.ratchet_key = pos;
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pos += ratchet_key_length;
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*(pos++) = CIPHERTEXT_TAG;
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pos = varint_encode(pos, ciphertext_length);
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result.ciphertext = pos;
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writer.ciphertext = pos;
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pos += ciphertext_length;
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result.body_length = pos - output;
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result.mac = pos;
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return result;
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}
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axolotl::MessageReader axolotl::decode_message(
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std::size_t axolotl::decode_message(
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axolotl::MessageReader & reader,
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std::uint8_t const * input, std::size_t input_length,
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std::size_t mac_length
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) {
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axolotl::MessageReader result;
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result.body_length = 0;
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std::uint8_t const * pos = input;
|
||||
std::uint8_t const * end = input + input_length - mac_length;
|
||||
std::uint8_t flags = 0;
|
||||
result.mac = end;
|
||||
std::size_t result = std::size_t(-1);
|
||||
if (pos == end) return result;
|
||||
result.version = *(pos++);
|
||||
reader.version = *(pos++);
|
||||
while (pos != end) {
|
||||
uint8_t tag = *(pos);
|
||||
if (tag == COUNTER_TAG) {
|
||||
++pos;
|
||||
std::uint8_t const * counter_start = pos;
|
||||
pos = varint_skip(pos, end);
|
||||
result.counter = varint_decode<std::uint32_t>(counter_start, pos);
|
||||
reader.counter = varint_decode<std::uint32_t>(counter_start, pos);
|
||||
flags |= 1;
|
||||
} else if (tag == RATCHET_KEY_TAG) {
|
||||
++pos;
|
||||
|
|
@ -150,8 +147,8 @@ axolotl::MessageReader axolotl::decode_message(
|
|||
pos = varint_skip(pos, end);
|
||||
std::size_t len = varint_decode<std::size_t>(len_start, pos);
|
||||
if (len > end - pos) return result;
|
||||
result.ratchet_key_length = len;
|
||||
result.ratchet_key = pos;
|
||||
reader.ratchet_key_length = len;
|
||||
reader.ratchet_key = pos;
|
||||
pos += len;
|
||||
flags |= 2;
|
||||
} else if (tag == CIPHERTEXT_TAG) {
|
||||
|
|
@ -160,8 +157,8 @@ axolotl::MessageReader axolotl::decode_message(
|
|||
pos = varint_skip(pos, end);
|
||||
std::size_t len = varint_decode<std::size_t>(len_start, pos);
|
||||
if (len > end - pos) return result;
|
||||
result.ciphertext_length = len;
|
||||
result.ciphertext = pos;
|
||||
reader.ciphertext_length = len;
|
||||
reader.ciphertext = pos;
|
||||
pos += len;
|
||||
flags |= 4;
|
||||
} else if (tag & 0x7 == 0) {
|
||||
|
|
@ -174,11 +171,13 @@ axolotl::MessageReader axolotl::decode_message(
|
|||
if (len > end - pos) return result;
|
||||
pos += len;
|
||||
} else {
|
||||
return result;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
}
|
||||
if (flags == 0x7) {
|
||||
result.body_length = end - input;
|
||||
reader.input = input;
|
||||
reader.input_length = input_length;
|
||||
return std::size_t(pos - input);
|
||||
}
|
||||
return result;
|
||||
}
|
||||
|
|
|
|||
214
src/ratchet.cpp
214
src/ratchet.cpp
|
|
@ -15,13 +15,13 @@
|
|||
#include "axolotl/ratchet.hh"
|
||||
#include "axolotl/message.hh"
|
||||
#include "axolotl/memory.hh"
|
||||
#include "axolotl/cipher.hh"
|
||||
|
||||
#include <cstring>
|
||||
|
||||
namespace {
|
||||
|
||||
std::uint8_t PROTOCOL_VERSION = 3;
|
||||
std::size_t MAC_LENGTH = 8;
|
||||
std::size_t KEY_LENGTH = axolotl::Curve25519PublicKey::LENGTH;
|
||||
std::uint8_t MESSAGE_KEY_SEED[1] = {0x01};
|
||||
std::uint8_t CHAIN_KEY_SEED[1] = {0x02};
|
||||
|
|
@ -70,59 +70,43 @@ void create_message_keys(
|
|||
axolotl::KdfInfo const & info,
|
||||
axolotl::MessageKey & message_key
|
||||
) {
|
||||
axolotl::SharedKey secret;
|
||||
axolotl::hmac_sha256(
|
||||
chain_key.key, sizeof(chain_key.key),
|
||||
MESSAGE_KEY_SEED, sizeof(MESSAGE_KEY_SEED),
|
||||
secret
|
||||
message_key.key
|
||||
);
|
||||
std::uint8_t derived_secrets[80];
|
||||
axolotl::hkdf_sha256(
|
||||
secret, sizeof(secret),
|
||||
NULL, 0,
|
||||
info.message_info, info.message_info_length,
|
||||
derived_secrets, sizeof(derived_secrets)
|
||||
);
|
||||
std::memcpy(message_key.cipher_key.key, derived_secrets, 32);
|
||||
std::memcpy(message_key.mac_key, derived_secrets + 32, 32);
|
||||
std::memcpy(message_key.iv.iv, derived_secrets + 64, 16);
|
||||
message_key.index = chain_key.index;
|
||||
axolotl::unset(derived_secrets);
|
||||
axolotl::unset(secret);
|
||||
}
|
||||
|
||||
|
||||
bool verify_mac(
|
||||
std::size_t verify_mac_and_decrypt(
|
||||
axolotl::Cipher const & cipher,
|
||||
axolotl::MessageKey const & message_key,
|
||||
std::uint8_t const * input,
|
||||
axolotl::MessageReader const & reader
|
||||
axolotl::MessageReader const & reader,
|
||||
std::uint8_t * plaintext, std::size_t max_plaintext_length
|
||||
) {
|
||||
std::uint8_t mac[axolotl::HMAC_SHA256_OUTPUT_LENGTH];
|
||||
axolotl::hmac_sha256(
|
||||
message_key.mac_key, sizeof(message_key.mac_key),
|
||||
input, reader.body_length,
|
||||
mac
|
||||
return cipher.decrypt(
|
||||
message_key.key, sizeof(message_key.key),
|
||||
reader.input, reader.input_length,
|
||||
reader.ciphertext, reader.ciphertext_length,
|
||||
plaintext, max_plaintext_length
|
||||
);
|
||||
|
||||
bool result = axolotl::is_equal(mac, reader.mac, MAC_LENGTH);
|
||||
axolotl::unset(mac);
|
||||
return result;
|
||||
}
|
||||
|
||||
|
||||
bool verify_mac_for_existing_chain(
|
||||
std::size_t verify_mac_and_decrypt_for_existing_chain(
|
||||
axolotl::Session const & session,
|
||||
axolotl::ChainKey const & chain,
|
||||
std::uint8_t const * input,
|
||||
axolotl::MessageReader const & reader
|
||||
axolotl::MessageReader const & reader,
|
||||
std::uint8_t * plaintext, std::size_t max_plaintext_length
|
||||
) {
|
||||
if (reader.counter < chain.index) {
|
||||
return false;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
|
||||
/* Limit the number of hashes we're prepared to compute */
|
||||
if (reader.counter - chain.index > MAX_MESSAGE_GAP) {
|
||||
return false;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
|
||||
axolotl::ChainKey new_chain = chain;
|
||||
|
|
@ -134,16 +118,20 @@ bool verify_mac_for_existing_chain(
|
|||
axolotl::MessageKey message_key;
|
||||
create_message_keys(new_chain, session.kdf_info, message_key);
|
||||
|
||||
bool result = verify_mac(message_key, input, reader);
|
||||
std::size_t result = verify_mac_and_decrypt(
|
||||
session.ratchet_cipher, message_key, reader,
|
||||
plaintext, max_plaintext_length
|
||||
);
|
||||
|
||||
axolotl::unset(new_chain);
|
||||
return result;
|
||||
}
|
||||
|
||||
|
||||
bool verify_mac_for_new_chain(
|
||||
std::size_t verify_mac_and_decrypt_for_new_chain(
|
||||
axolotl::Session const & session,
|
||||
std::uint8_t const * input,
|
||||
axolotl::MessageReader const & reader
|
||||
axolotl::MessageReader const & reader,
|
||||
std::uint8_t * plaintext, std::size_t max_plaintext_length
|
||||
) {
|
||||
axolotl::SharedKey new_root_key;
|
||||
axolotl::ReceiverChain new_chain;
|
||||
|
|
@ -168,8 +156,9 @@ bool verify_mac_for_new_chain(
|
|||
new_root_key, new_chain.chain_key
|
||||
);
|
||||
|
||||
bool result = verify_mac_for_existing_chain(
|
||||
session, new_chain.chain_key, input, reader
|
||||
std::size_t result = verify_mac_and_decrypt_for_existing_chain(
|
||||
session, new_chain.chain_key, reader,
|
||||
plaintext, max_plaintext_length
|
||||
);
|
||||
axolotl::unset(new_root_key);
|
||||
axolotl::unset(new_chain);
|
||||
|
|
@ -180,8 +169,11 @@ bool verify_mac_for_new_chain(
|
|||
|
||||
|
||||
axolotl::Session::Session(
|
||||
axolotl::KdfInfo const & kdf_info
|
||||
) : kdf_info(kdf_info), last_error(axolotl::ErrorCode::SUCCESS) {
|
||||
axolotl::KdfInfo const & kdf_info,
|
||||
Cipher const & ratchet_cipher
|
||||
) : kdf_info(kdf_info),
|
||||
ratchet_cipher(ratchet_cipher),
|
||||
last_error(axolotl::ErrorCode::SUCCESS) {
|
||||
}
|
||||
|
||||
|
||||
|
|
@ -232,7 +224,7 @@ std::size_t axolotl::Session::pickle_max_output_length() {
|
|||
pickle_length += sender_chain.size() * send_chain_length;
|
||||
pickle_length += receiver_chains.size() * recv_chain_length;
|
||||
pickle_length += skipped_message_keys.size() * skip_key_length;
|
||||
return axolotl::aes_encrypt_cbc_length(pickle_length) + MAC_LENGTH;
|
||||
return pickle_length;
|
||||
}
|
||||
|
||||
namespace {
|
||||
|
|
@ -299,11 +291,10 @@ std::size_t axolotl::Session::pickle(
|
|||
}
|
||||
for (const axolotl::SkippedMessageKey &key : skipped_message_keys) {
|
||||
pos = pickle_counter(pos, key.message_key.index);
|
||||
pos = pickle_bytes(pos, 32, key.message_key.cipher_key.key);
|
||||
pos = pickle_bytes(pos, 32, key.message_key.mac_key);
|
||||
pos = pickle_bytes(pos, 16, key.message_key.iv.iv);
|
||||
pos = pickle_bytes(pos, 32, key.message_key.key);
|
||||
pos = pickle_bytes(pos, 32, key.ratchet_key.public_key);
|
||||
}
|
||||
return pos - output;
|
||||
}
|
||||
|
||||
std::size_t axolotl::Session::unpickle(
|
||||
|
|
@ -352,11 +343,10 @@ std::size_t axolotl::Session::unpickle(
|
|||
skipped_message_keys.end()
|
||||
);
|
||||
pos = unpickle_counter(pos, key.message_key.index);
|
||||
pos = unpickle_bytes(pos, 32, key.message_key.cipher_key.key);
|
||||
pos = unpickle_bytes(pos, 32, key.message_key.mac_key);
|
||||
pos = unpickle_bytes(pos, 16, key.message_key.iv.iv);
|
||||
pos = unpickle_bytes(pos, 32, key.message_key.key);
|
||||
pos = unpickle_bytes(pos, 32, key.ratchet_key.public_key);
|
||||
}
|
||||
return pos - input;
|
||||
}
|
||||
|
||||
|
||||
|
|
@ -369,7 +359,7 @@ std::size_t axolotl::Session::encrypt_max_output_length(
|
|||
}
|
||||
std::size_t padded = axolotl::aes_encrypt_cbc_length(plaintext_length);
|
||||
return axolotl::encode_message_length(
|
||||
counter, KEY_LENGTH, padded, MAC_LENGTH
|
||||
counter, KEY_LENGTH, padded, ratchet_cipher.mac_length()
|
||||
);
|
||||
}
|
||||
|
||||
|
|
@ -384,11 +374,13 @@ std::size_t axolotl::Session::encrypt(
|
|||
std::uint8_t const * random, std::size_t random_length,
|
||||
std::uint8_t * output, std::size_t max_output_length
|
||||
) {
|
||||
std::size_t output_length = encrypt_max_output_length(plaintext_length);
|
||||
|
||||
if (random_length < encrypt_random_length()) {
|
||||
last_error = axolotl::ErrorCode::NOT_ENOUGH_RANDOM;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
if (max_output_length < encrypt_max_output_length(plaintext_length)) {
|
||||
if (max_output_length < output_length) {
|
||||
last_error = axolotl::ErrorCode::OUTPUT_BUFFER_TOO_SMALL;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
|
|
@ -409,32 +401,29 @@ std::size_t axolotl::Session::encrypt(
|
|||
create_message_keys(sender_chain[0].chain_key, kdf_info, keys);
|
||||
advance_chain_key(sender_chain[0].chain_key, sender_chain[0].chain_key);
|
||||
|
||||
std::size_t padded = axolotl::aes_encrypt_cbc_length(plaintext_length);
|
||||
std::size_t ciphertext_length = ratchet_cipher.encrypt_ciphertext_length(
|
||||
plaintext_length
|
||||
);
|
||||
std::uint32_t counter = keys.index;
|
||||
Curve25519PublicKey const & ratchet_key = sender_chain[0].ratchet_key;
|
||||
|
||||
axolotl::MessageWriter writer(axolotl::encode_message(
|
||||
PROTOCOL_VERSION, counter, KEY_LENGTH, padded, output
|
||||
));
|
||||
axolotl::MessageWriter writer;
|
||||
|
||||
axolotl::encode_message(
|
||||
writer, PROTOCOL_VERSION, counter, KEY_LENGTH, ciphertext_length, output
|
||||
);
|
||||
|
||||
std::memcpy(writer.ratchet_key, ratchet_key.public_key, KEY_LENGTH);
|
||||
|
||||
axolotl::aes_encrypt_cbc(
|
||||
keys.cipher_key, keys.iv,
|
||||
ratchet_cipher.encrypt(
|
||||
keys.key, sizeof(keys.key),
|
||||
plaintext, plaintext_length,
|
||||
writer.ciphertext
|
||||
writer.ciphertext, ciphertext_length,
|
||||
output, output_length
|
||||
);
|
||||
|
||||
std::uint8_t mac[axolotl::HMAC_SHA256_OUTPUT_LENGTH];
|
||||
axolotl::hmac_sha256(
|
||||
keys.mac_key, sizeof(keys.mac_key),
|
||||
output, writer.body_length,
|
||||
mac
|
||||
);
|
||||
std::memcpy(writer.mac, mac, MAC_LENGTH);
|
||||
|
||||
axolotl::unset(keys);
|
||||
return writer.body_length + MAC_LENGTH;
|
||||
return output_length;
|
||||
}
|
||||
|
||||
|
||||
|
|
@ -454,16 +443,17 @@ std::size_t axolotl::Session::decrypt(
|
|||
return std::size_t(-1);
|
||||
}
|
||||
|
||||
axolotl::MessageReader reader(axolotl::decode_message(
|
||||
input, input_length, MAC_LENGTH
|
||||
));
|
||||
axolotl::MessageReader reader;
|
||||
std::size_t body_length = axolotl::decode_message(
|
||||
reader, input, input_length, ratchet_cipher.mac_length()
|
||||
);
|
||||
|
||||
if (reader.version != PROTOCOL_VERSION) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_VERSION;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
|
||||
if (reader.body_length == 0 || reader.ratchet_key_length != KEY_LENGTH) {
|
||||
if (body_length == size_t(-1) || reader.ratchet_key_length != KEY_LENGTH) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_FORMAT;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
|
|
@ -479,40 +469,30 @@ std::size_t axolotl::Session::decrypt(
|
|||
}
|
||||
}
|
||||
|
||||
std::size_t result = std::size_t(-1);
|
||||
|
||||
if (!chain) {
|
||||
if (!verify_mac_for_new_chain(*this, input, reader)) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_MAC;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
} else {
|
||||
if (chain->chain_key.index > reader.counter) {
|
||||
/* Chain already advanced beyond the key for this message
|
||||
* Check if the message keys are in the skipped key list. */
|
||||
for (axolotl::SkippedMessageKey & skipped : skipped_message_keys) {
|
||||
if (reader.counter == skipped.message_key.index
|
||||
&& 0 == std::memcmp(
|
||||
skipped.ratchet_key.public_key, reader.ratchet_key,
|
||||
KEY_LENGTH
|
||||
)
|
||||
) {
|
||||
/* Found the key for this message. Check the MAC. */
|
||||
if (!verify_mac(skipped.message_key, input, reader)) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_MAC;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
result = verify_mac_and_decrypt_for_new_chain(
|
||||
*this, reader, plaintext, max_plaintext_length
|
||||
);
|
||||
} else if (chain->chain_key.index > reader.counter) {
|
||||
/* Chain already advanced beyond the key for this message
|
||||
* Check if the message keys are in the skipped key list. */
|
||||
for (axolotl::SkippedMessageKey & skipped : skipped_message_keys) {
|
||||
if (reader.counter == skipped.message_key.index
|
||||
&& 0 == std::memcmp(
|
||||
skipped.ratchet_key.public_key, reader.ratchet_key,
|
||||
KEY_LENGTH
|
||||
)
|
||||
) {
|
||||
/* Found the key for this message. Check the MAC. */
|
||||
|
||||
std::size_t result = axolotl::aes_decrypt_cbc(
|
||||
skipped.message_key.cipher_key,
|
||||
skipped.message_key.iv,
|
||||
reader.ciphertext, reader.ciphertext_length,
|
||||
plaintext
|
||||
);
|
||||
|
||||
if (result == std::size_t(-1)) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_MAC;
|
||||
return result;
|
||||
}
|
||||
result = verify_mac_and_decrypt(
|
||||
ratchet_cipher, skipped.message_key, reader,
|
||||
plaintext, max_plaintext_length
|
||||
);
|
||||
|
||||
if (result != std::size_t(-1)) {
|
||||
/* Remove the key from the skipped keys now that we've
|
||||
* decoded the message it corresponds to. */
|
||||
axolotl::unset(skipped);
|
||||
|
|
@ -520,15 +500,16 @@ std::size_t axolotl::Session::decrypt(
|
|||
return result;
|
||||
}
|
||||
}
|
||||
/* No matching keys for the message, fail with bad mac */
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_MAC;
|
||||
return std::size_t(-1);
|
||||
} else if (!verify_mac_for_existing_chain(
|
||||
*this, chain->chain_key, input, reader
|
||||
)) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_MAC;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
} else {
|
||||
result = verify_mac_and_decrypt_for_existing_chain(
|
||||
*this, chain->chain_key, reader, plaintext, max_plaintext_length
|
||||
);
|
||||
}
|
||||
|
||||
if (result == std::size_t(-1)) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_MAC;
|
||||
return std::size_t(-1);
|
||||
}
|
||||
|
||||
if (!chain) {
|
||||
|
|
@ -555,22 +536,7 @@ std::size_t axolotl::Session::decrypt(
|
|||
advance_chain_key(chain->chain_key, chain->chain_key);
|
||||
}
|
||||
|
||||
axolotl::MessageKey message_key;
|
||||
create_message_keys(chain->chain_key, kdf_info, message_key);
|
||||
std::size_t result = axolotl::aes_decrypt_cbc(
|
||||
message_key.cipher_key,
|
||||
message_key.iv,
|
||||
reader.ciphertext, reader.ciphertext_length,
|
||||
plaintext
|
||||
);
|
||||
axolotl::unset(message_key);
|
||||
|
||||
advance_chain_key(chain->chain_key, chain->chain_key);
|
||||
|
||||
if (result == std::size_t(-1)) {
|
||||
last_error = axolotl::ErrorCode::BAD_MESSAGE_MAC;
|
||||
return std::size_t(-1);
|
||||
} else {
|
||||
return result;
|
||||
}
|
||||
return result;
|
||||
}
|
||||
|
|
|
|||
|
|
@ -27,9 +27,9 @@ std::uint8_t hmacsha2[9] = "hmacsha2";
|
|||
|
||||
TestCase test_case("Message decode test");
|
||||
|
||||
axolotl::MessageReader reader(axolotl::decode_message(message1, 35, 8));
|
||||
axolotl::MessageReader reader;
|
||||
axolotl::decode_message(reader, message1, 35, 8);
|
||||
|
||||
assert_equals(std::size_t(27), reader.body_length);
|
||||
assert_equals(std::uint8_t(3), reader.version);
|
||||
assert_equals(std::uint32_t(1), reader.counter);
|
||||
assert_equals(std::size_t(10), reader.ratchet_key_length);
|
||||
|
|
@ -37,7 +37,6 @@ assert_equals(std::size_t(10), reader.ciphertext_length);
|
|||
|
||||
assert_equals(ratchetkey, reader.ratchet_key, 10);
|
||||
assert_equals(ciphertext, reader.ciphertext, 10);
|
||||
assert_equals(hmacsha2, reader.mac, 8);
|
||||
|
||||
|
||||
} /* Message decode test */
|
||||
|
|
@ -51,12 +50,12 @@ assert_equals(std::size_t(35), length);
|
|||
|
||||
std::uint8_t output[length];
|
||||
|
||||
axolotl::MessageWriter writer(axolotl::encode_message(3, 1, 10, 10, output));
|
||||
assert_equals(std::size_t(27), writer.body_length);
|
||||
axolotl::MessageWriter writer;
|
||||
axolotl::encode_message(writer, 3, 1, 10, 10, output);
|
||||
|
||||
std::memcpy(writer.ratchet_key, ratchetkey, 10);
|
||||
std::memcpy(writer.ciphertext, ciphertext, 10);
|
||||
std::memcpy(writer.mac, hmacsha2, 8);
|
||||
std::memcpy(output + length - 8, hmacsha2, 8);
|
||||
|
||||
assert_equals(message2, output, 35);
|
||||
|
||||
|
|
|
|||
|
|
@ -13,6 +13,7 @@
|
|||
* limitations under the License.
|
||||
*/
|
||||
#include "axolotl/ratchet.hh"
|
||||
#include "axolotl/cipher.hh"
|
||||
#include "unittest.hh"
|
||||
|
||||
|
||||
|
|
@ -24,10 +25,13 @@ std::uint8_t message_info[] = "AxolotlMessageKeys";
|
|||
|
||||
axolotl::KdfInfo kdf_info = {
|
||||
root_info, sizeof(root_info) - 1,
|
||||
ratchet_info, sizeof(ratchet_info - 1),
|
||||
message_info, sizeof(ratchet_info - 1)
|
||||
ratchet_info, sizeof(ratchet_info) - 1
|
||||
};
|
||||
|
||||
axolotl::CipherAesSha256 cipher(
|
||||
message_info, sizeof(message_info) - 1
|
||||
);
|
||||
|
||||
std::uint8_t random_bytes[] = "0123456789ABDEF0123456789ABCDEF";
|
||||
axolotl::Curve25519KeyPair bob_key;
|
||||
axolotl::generate_key(random_bytes, bob_key);
|
||||
|
|
@ -37,8 +41,8 @@ std::uint8_t shared_secret[] = "A secret";
|
|||
{ /* Send/Receive test case */
|
||||
TestCase test_case("Axolotl Send/Receive");
|
||||
|
||||
axolotl::Session alice(kdf_info);
|
||||
axolotl::Session bob(kdf_info);
|
||||
axolotl::Session alice(kdf_info, cipher);
|
||||
axolotl::Session bob(kdf_info, cipher);
|
||||
|
||||
alice.initialise_as_bob(shared_secret, sizeof(shared_secret) - 1, bob_key);
|
||||
bob.initialise_as_alice(shared_secret, sizeof(shared_secret) - 1, bob_key);
|
||||
|
|
@ -106,8 +110,8 @@ std::size_t encrypt_length, decrypt_length;
|
|||
|
||||
TestCase test_case("Axolotl Out of Order");
|
||||
|
||||
axolotl::Session alice(kdf_info);
|
||||
axolotl::Session bob(kdf_info);
|
||||
axolotl::Session alice(kdf_info, cipher);
|
||||
axolotl::Session bob(kdf_info, cipher);
|
||||
|
||||
alice.initialise_as_bob(shared_secret, sizeof(shared_secret) - 1, bob_key);
|
||||
bob.initialise_as_alice(shared_secret, sizeof(shared_secret) - 1, bob_key);
|
||||
|
|
|
|||
Loading…
Reference in New Issue