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Mark Haines
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2 changed files with 60 additions and 4 deletions
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@ -83,41 +83,80 @@ struct Session {
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KdfInfo const & kdf_info
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);
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/** A pair of string to feed into the KDF identifing the application */
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/** A some strings identifing the application to feed into the KDF. */
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KdfInfo kdf_info;
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/** The last error that happened encypting or decrypting a message */
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/** The last error that happened encypting 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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* A new root_key derived each time a chain key is derived. */
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SharedKey root_key;
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/** The sender chain is used to send messages. Each time a new ephemeral
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* key is received from the remote server we generate a new sender chain
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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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* 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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/** List of message keys we've skipped over when advancing the receiver
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* chain. */
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List<SkippedMessageKey, MAX_SKIPPED_MESSAGE_KEYS> skipped_message_keys;
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/** Initialise the session using a shared secret and the public part of the
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* remote's first ratchet key */
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void initialise_as_bob(
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std::uint8_t const * shared_secret, std::size_t shared_secret_length,
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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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* 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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Curve25519KeyPair const & our_ratchet_key
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);
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/** The maximum number of bytes of output the encrypt method will write for
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* a given message length. */
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std::size_t encrypt_max_output_length(
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std::size_t plaintext_length
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);
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/** The number of bytes of random data the encrypt method will need to
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* encrypt a message. This will be 32 bytes if the session needs to
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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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* 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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* OUTPUT_BUFFER_TOO_SMALL if the output buffer is too small. */
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std::size_t 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 * 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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* 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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* 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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* 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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* BAD_MESSAGE_MAC if the message could not be verified */
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std::size_t decrypt(
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std::uint8_t const * input, std::size_t input_length,
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std::uint8_t * plaintext, std::size_t max_plaintext_length
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@ -28,7 +28,7 @@ struct Curve25519KeyPair : public Curve25519PublicKey {
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std::uint8_t private_key[32];
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};
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/** Generate a curve25519 key pair from 32 random bytes. */
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void generate_key(
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std::uint8_t const * random_32_bytes,
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Curve25519KeyPair & key_pair
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@ -37,7 +37,8 @@ void generate_key(
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const std::size_t CURVE25519_SHARED_SECRET_LENGTH = 32;
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/** Create a shared secret using our private key and their public key.
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* The output buffer must be at least 32 bytes long. */
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void curve25519_shared_secret(
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Curve25519KeyPair const & our_key,
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Curve25519PublicKey const & their_key,
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@ -57,11 +58,14 @@ struct Aes256Iv {
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};
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/** The length of output the aes_encrypt_cbc function will write */
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std::size_t aes_encrypt_cbc_length(
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std::size_t input_length
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);
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/** Encrypts the input using AES256 in CBC mode with PKCS#7 padding.
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* The output buffer must be big enough to hold the output including padding */
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void aes_encrypt_cbc(
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Aes256Key const & key,
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Aes256Iv const & iv,
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@ -70,6 +74,10 @@ void aes_encrypt_cbc(
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);
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/** Decrypts the input using AES256 in CBC mode. The output buffer must be at
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* least the same size as the input buffer. Returns the length of the plaintext
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* without padding on success or std::size_t(-1) if the padding is invalid.
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*/
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std::size_t aes_decrypt_cbc(
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Aes256Key const & key,
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Aes256Iv const & iv,
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@ -78,6 +86,8 @@ std::size_t aes_decrypt_cbc(
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);
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/** Computes SHA-256 of the input. The output buffer must be a least 32
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* bytes long. */
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void sha256(
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std::uint8_t const * input, std::size_t input_length,
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std::uint8_t * output
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@ -87,6 +97,10 @@ void sha256(
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const std::size_t HMAC_SHA256_OUTPUT_LENGTH = 32;
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/** HMAC: Keyed-Hashing for Message Authentication
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* http://tools.ietf.org/html/rfc2104
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* Computes HMAC-SHA-256 of the input for the key. The output buffer must
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* be at least 32 bytes long. */
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void hmac_sha256(
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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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@ -94,6 +108,9 @@ void hmac_sha256(
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);
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/** HMAC-based Key Derivation Function (HKDF)
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* https://tools.ietf.org/html/rfc5869
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* Derives key material from the input bytes. */
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void hkdf_sha256(
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std::uint8_t const * input, std::size_t input_length,
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std::uint8_t const * info, std::size_t info_length,
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