From 816435a86097a6609cb6e5ad422083bc49b19632 Mon Sep 17 00:00:00 2001
From: Mark Haines <mark.haines@matrix.org>
Date: Thu, 11 Jun 2015 14:20:35 +0100
Subject: [PATCH] Move AES specific details behind a cipher interface
---
include/axolotl/cipher.hh | 127 +++++++++++++++++++++
include/axolotl/list.hh | 2 +-
include/axolotl/message.hh | 22 ++--
include/axolotl/ratchet.hh | 32 +++---
src/cipher.cpp | 125 +++++++++++++++++++++
src/message.cpp | 39 ++++---
src/ratchet.cpp | 218 ++++++++++++++++---------------------
tests/test_message.cpp | 11 +-
tests/test_ratchet.cpp | 16 ++-
9 files changed, 406 insertions(+), 186 deletions(-)
create mode 100644 include/axolotl/cipher.hh
create mode 100644 src/cipher.cpp
diff --git a/include/axolotl/cipher.hh b/include/axolotl/cipher.hh
new file mode 100644
index 0000000..93974fd
--- /dev/null
+++ b/include/axolotl/cipher.hh
@@ -0,0 +1,127 @@
+/* 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.
+ */
+
+#ifndef AXOLOTL_CIPHER_HH_
+#define AXOLOTL_CIPHER_HH_
+
+#include <cstdint>
+
+namespace axolotl {
+
+class Cipher {
+public:
+ virtual ~Cipher();
+
+ /**
+ * Returns the length of the message authentication code that will be
+ * appended to the output.
+ */
+ virtual std::size_t mac_length() const = 0;
+
+ /**
+ * Returns the length of cipher-text for a given length of plain-text.
+ */
+ virtual std::size_t encrypt_ciphertext_length(
+ std::size_t plaintext_length
+ ) const = 0;
+
+ /*
+ * Encrypts the plain-text into the output buffer and authenticates the
+ * contents of the output buffer covering both cipher-text and any other
+ * associated data in the output buffer.
+ *
+ * |---------------------------------------output_length-->|
+ * output |--ciphertext_length-->| |---mac_length-->|
+ * ciphertext
+ *
+ * Returns std::size_t(-1) if the length of the cipher-text or the output
+ * buffer is too small. Otherwise returns the length of the output buffer.
+ */
+ virtual std::size_t encrypt(
+ std::uint8_t const * key, std::size_t key_length,
+ std::uint8_t const * plaintext, std::size_t plaintext_length,
+ std::uint8_t * ciphertext, std::size_t ciphertext_length,
+ std::uint8_t * output, std::size_t output_length
+ ) const = 0;
+
+ /**
+ * Returns the maximum length of plain-text that a given length of
+ * cipher-text can contain.
+ */
+ virtual std::size_t decrypt_max_plaintext_length(
+ std::size_t ciphertext_length
+ ) const = 0;
+
+ /**
+ * Authenticates the input and decrypts the cipher-text into the plain-text
+ * buffer.
+ *
+ * |----------------------------------------input_length-->|
+ * input |--ciphertext_length-->| |---mac_length-->|
+ * ciphertext
+ *
+ * Returns std::size_t(-1) if the length of the plain-text buffer is too
+ * small or if the authentication check fails. Otherwise returns the length
+ * of the plain text.
+ */
+ virtual std::size_t decrypt(
+ std::uint8_t const * key, std::size_t key_length,
+ std::uint8_t const * input, std::size_t input_length,
+ std::uint8_t const * ciphertext, std::size_t ciphertext_length,
+ std::uint8_t * plaintext, std::size_t max_plaintext_length
+ ) const = 0;
+};
+
+
+class CipherAesSha256 : public Cipher {
+public:
+ CipherAesSha256(
+ std::uint8_t const * kdf_info, std::size_t kdf_info_length
+ );
+
+ virtual std::size_t mac_length() const;
+
+ virtual std::size_t encrypt_ciphertext_length(
+ std::size_t plaintext_length
+ ) const;
+
+ virtual std::size_t encrypt(
+ std::uint8_t const * key, std::size_t key_length,
+ std::uint8_t const * plaintext, std::size_t plaintext_length,
+ std::uint8_t * ciphertext, std::size_t ciphertext_length,
+ std::uint8_t * output, std::size_t output_length
+ ) const;
+
+ virtual std::size_t decrypt_max_plaintext_length(
+ std::size_t ciphertext_length
+ ) const;
+
+ virtual std::size_t decrypt(
+ std::uint8_t const * key, std::size_t key_length,
+ std::uint8_t const * input, std::size_t input_length,
+ std::uint8_t const * ciphertext, std::size_t ciphertext_length,
+ std::uint8_t * plaintext, std::size_t max_plaintext_length
+ ) const;
+
+private:
+ std::uint8_t const * kdf_info;
+ std::size_t kdf_info_length;
+};
+
+
+} // namespace
+
+
+#endif /* AXOLOTL_CIPHER_HH_ */
diff --git a/include/axolotl/list.hh b/include/axolotl/list.hh
index d1407b8..ae8900c 100644
--- a/include/axolotl/list.hh
+++ b/include/axolotl/list.hh
@@ -92,7 +92,7 @@ public:
}
List<T, max_size> & operator=(List<T, max_size> const & other) {
- if (this = &other) {
+ if (this == &other) {
return *this;
}
T * this_pos = _data;
diff --git a/include/axolotl/message.hh b/include/axolotl/message.hh
index 5cd4211..cfbb715 100644
--- a/include/axolotl/message.hh
+++ b/include/axolotl/message.hh
@@ -30,22 +30,17 @@ std::size_t encode_message_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;
+ std::uint8_t const * input; std::size_t input_length;
+ std::uint8_t const * ratchet_key; std::size_t ratchet_key_length;
+ std::uint8_t const * ciphertext; std::size_t ciphertext_length;
};
@@ -53,7 +48,9 @@ struct MessageReader {
* Writes the message headers into the output buffer.
* Returns a writer struct populated with pointers into the output buffer.
*/
-MessageWriter encode_message(
+
+void encode_message(
+ MessageWriter & writer,
std::uint8_t version,
std::uint32_t counter,
std::size_t ratchet_key_length,
@@ -64,10 +61,11 @@ MessageWriter encode_message(
/**
* 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.
+ * Populates the reader struct with pointers into the input buffer.
+ * On failure returns std::size_t(-1).
*/
-MessageReader decode_message(
+std::size_t decode_message(
+ MessageReader & reader,
std::uint8_t const * input, std::size_t input_length,
std::size_t mac_length
);
diff --git a/include/axolotl/ratchet.hh b/include/axolotl/ratchet.hh
index cf41359..f4eeafa 100644
--- a/include/axolotl/ratchet.hh
+++ b/include/axolotl/ratchet.hh
@@ -18,6 +18,8 @@
namespace axolotl {
+class Cipher;
+
typedef std::uint8_t SharedKey[32];
@@ -29,9 +31,7 @@ struct ChainKey {
struct MessageKey {
std::uint32_t index;
- Aes256Key cipher_key;
- SharedKey mac_key;
- Aes256Iv iv;
+ SharedKey key;
};
@@ -72,21 +72,23 @@ struct KdfInfo {
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
+ KdfInfo const & kdf_info,
+ Cipher const & ratchet_cipher
);
- /** A some strings identifing the application to feed into the KDF. */
- const KdfInfo &kdf_info;
+ /** A some strings identifying the application to feed into the KDF. */
+ KdfInfo const & kdf_info;
+
+ /** The AEAD cipher to use for encrypting messages. */
+ Cipher const & ratchet_cipher;
- /** The last error that happened encypting or decrypting a message. */
+ /** The last error that happened encrypting or decrypting a message. */
ErrorCode last_error;
/** The root key is used to generate chain keys from the ephemeral keys.
@@ -98,7 +100,7 @@ struct Session {
* 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
+ /** The receiver chain is used to decrypt received 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;
@@ -114,7 +116,7 @@ struct Session {
Curve25519PublicKey const & their_ratchet_key
);
- /** Intialise the session using a shared secret and the public/private key
+ /** Initialise 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,
@@ -150,7 +152,7 @@ struct Session {
* 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
+ /** Encrypt some plain-text. 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
@@ -161,16 +163,16 @@ struct Session {
std::uint8_t * output, std::size_t max_output_length
);
- /** An upper bound on the number of bytes of plaintext the decrypt method
+ /** An upper bound on the number of bytes of plain-text 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
+ /** Decrypt a message. Returns the length of the decrypted plain-text 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
+ * plain-text 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
diff --git a/src/cipher.cpp b/src/cipher.cpp
new file mode 100644
index 0000000..86cde88
--- /dev/null
+++ b/src/cipher.cpp
@@ -0,0 +1,125 @@
+#include "axolotl/cipher.hh"
+#include "axolotl/crypto.hh"
+#include "axolotl/memory.hh"
+#include <cstring>
+
+axolotl::Cipher::~Cipher() {
+
+}
+
+namespace {
+
+static const std::size_t SHA256_LENGTH = 32;
+
+struct DerivedKeys {
+ axolotl::Aes256Key aes_key;
+ std::uint8_t mac_key[SHA256_LENGTH];
+ axolotl::Aes256Iv aes_iv;
+};
+
+
+static void derive_keys(
+ std::uint8_t const * kdf_info, std::size_t kdf_info_length,
+ std::uint8_t const * key, std::size_t key_length,
+ DerivedKeys & keys
+) {
+ std::uint8_t derived_secrets[80];
+ axolotl::hkdf_sha256(
+ key, key_length,
+ NULL, 0,
+ kdf_info, kdf_info_length,
+ derived_secrets, sizeof(derived_secrets)
+ );
+ std::memcpy(keys.aes_key.key, derived_secrets, 32);
+ std::memcpy(keys.mac_key, derived_secrets + 32, 32);
+ std::memcpy(keys.aes_iv.iv, derived_secrets + 64, 16);
+ axolotl::unset(derived_secrets);
+}
+
+static const std::size_t MAC_LENGTH = 8;
+
+} // namespace
+
+
+axolotl::CipherAesSha256::CipherAesSha256(
+ std::uint8_t const * kdf_info, std::size_t kdf_info_length
+) : kdf_info(kdf_info), kdf_info_length(kdf_info_length) {
+
+}
+
+
+std::size_t axolotl::CipherAesSha256::mac_length() const {
+ return MAC_LENGTH;
+}
+
+
+std::size_t axolotl::CipherAesSha256::encrypt_ciphertext_length(
+ std::size_t plaintext_length
+) const {
+ return axolotl::aes_encrypt_cbc_length(plaintext_length);
+}
+
+
+std::size_t axolotl::CipherAesSha256::encrypt(
+ std::uint8_t const * key, std::size_t key_length,
+ std::uint8_t const * plaintext, std::size_t plaintext_length,
+ std::uint8_t * ciphertext, std::size_t ciphertext_length,
+ std::uint8_t * output, std::size_t output_length
+) const {
+ if (encrypt_ciphertext_length(plaintext_length) < ciphertext_length) {
+ return std::size_t(-1);
+ }
+ struct DerivedKeys keys;
+ std::uint8_t mac[SHA256_LENGTH];
+
+ derive_keys(kdf_info, kdf_info_length, key, key_length, keys);
+
+ axolotl::aes_encrypt_cbc(
+ keys.aes_key, keys.aes_iv, plaintext, plaintext_length, ciphertext
+ );
+
+ axolotl::hmac_sha256(
+ keys.mac_key, SHA256_LENGTH, output, output_length - MAC_LENGTH, mac
+ );
+
+ std::memcpy(output + output_length - MAC_LENGTH, mac, MAC_LENGTH);
+
+ axolotl::unset(keys);
+ return output_length;
+}
+
+
+std::size_t axolotl::CipherAesSha256::decrypt_max_plaintext_length(
+ std::size_t ciphertext_length
+) const {
+ return ciphertext_length;
+}
+
+std::size_t axolotl::CipherAesSha256::decrypt(
+ std::uint8_t const * key, std::size_t key_length,
+ std::uint8_t const * input, std::size_t input_length,
+ std::uint8_t const * ciphertext, std::size_t ciphertext_length,
+ std::uint8_t * plaintext, std::size_t max_plaintext_length
+) const {
+ DerivedKeys keys;
+ std::uint8_t mac[SHA256_LENGTH];
+
+ derive_keys(kdf_info, kdf_info_length, key, key_length, keys);
+
+ axolotl::hmac_sha256(
+ keys.mac_key, SHA256_LENGTH, input, input_length - MAC_LENGTH, mac
+ );
+
+ std::uint8_t const * input_mac = input + input_length - MAC_LENGTH;
+ if (!axolotl::is_equal(input_mac, mac, MAC_LENGTH)) {
+ axolotl::unset(keys);
+ return std::size_t(-1);
+ }
+
+ std::size_t plaintext_length = axolotl::aes_decrypt_cbc(
+ keys.aes_key, keys.aes_iv, ciphertext, ciphertext_length, plaintext
+ );
+
+ axolotl::unset(keys);
+ return plaintext_length;
+}
diff --git a/src/message.cpp b/src/message.cpp
index 289faa3..46cadd8 100644
--- a/src/message.cpp
+++ b/src/message.cpp
@@ -94,55 +94,52 @@ std::size_t axolotl::encode_message_length(
length += 1 + varstring_length(ratchet_key_length);
length += 1 + varint_length(counter);
length += 1 + varstring_length(ciphertext_length);
- return length + mac_length;
+ length += mac_length;
+ return length;
}
-axolotl::MessageWriter axolotl::encode_message(
+void axolotl::encode_message(
+ axolotl::MessageWriter & writer,
std::uint8_t version,
std::uint32_t counter,
std::size_t ratchet_key_length,
std::size_t ciphertext_length,
std::uint8_t * output
) {
- axolotl::MessageWriter result;
std::uint8_t * pos = output;
*(pos++) = version;
*(pos++) = COUNTER_TAG;
pos = varint_encode(pos, counter);
*(pos++) = RATCHET_KEY_TAG;
pos = varint_encode(pos, ratchet_key_length);
- result.ratchet_key = pos;
+ writer.ratchet_key = pos;
pos += ratchet_key_length;
*(pos++) = CIPHERTEXT_TAG;
pos = varint_encode(pos, ciphertext_length);
- result.ciphertext = pos;
+ writer.ciphertext = pos;
pos += ciphertext_length;
- result.body_length = pos - output;
- result.mac = pos;
- return result;
}
-axolotl::MessageReader axolotl::decode_message(
+std::size_t axolotl::decode_message(
+ axolotl::MessageReader & reader,
std::uint8_t const * input, std::size_t input_length,
std::size_t mac_length
) {
- axolotl::MessageReader result;
- result.body_length = 0;
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;
}
diff --git a/src/ratchet.cpp b/src/ratchet.cpp
index b17e162..cd4f8f7 100644
--- a/src/ratchet.cpp
+++ b/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(
}
}
- 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);
- }
-
- 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;
- }
+ std::size_t result = std::size_t(-1);
+ if (!chain) {
+ 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. */
+
+ 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;
}
diff --git a/tests/test_message.cpp b/tests/test_message.cpp
index ca36ff5..9c0ab4a 100644
--- a/tests/test_message.cpp
+++ b/tests/test_message.cpp
@@ -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);
diff --git a/tests/test_ratchet.cpp b/tests/test_ratchet.cpp
index 95391e3..18c22e3 100644
--- a/tests/test_ratchet.cpp
+++ b/tests/test_ratchet.cpp
@@ -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);
--
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