144 lines
3.7 KiB
C++
144 lines
3.7 KiB
C++
#pragma once
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#include <stdint.h>
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#include <stddef.h>
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/**
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* @brief The size of a message authentication code
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*
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* The MAC size is determined by the size of the output
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* of the hash function used. In this case, for SHA256,
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* the size is 32 bytes (= 256 bit)
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*/
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#define SHA256_MAC_SIZE 32
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#pragma pack(push, 1)
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enum class MessageType: uint8_t {
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/// @brief The initial message from remote to device to request a challenge.
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initial = 0,
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/// @brief The second message in an unlock with the challenge from the device to the remote
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challenge = 1,
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/// @brief The third message with the signed challenge from the remote to the device
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request = 2,
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/// @brief The final message with the unlock result from the device to the remote
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response = 3,
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};
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enum class MessageResult: uint8_t {
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/// @brief The message was accepted.
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MessageAccepted = 0,
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/// @brief The web socket received text while waiting for binary data.
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TextReceivedOverSocket = 1,
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/// @brief An unexpected socket event occured while performing the exchange.
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UnexpectedSocketEvent = 2,
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/// @brief The received message size is invalid.
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InvalidMessageSizeFromRemote = 3,
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/// @brief The message signature was incorrect.
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InvalidSignatureFromRemote = 4,
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/// @brief The server challenge of the message did not match previous messages
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InvalidServerChallengeFromRemote = 5,
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/// @brief The client challenge of the message did not match previous messages
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InvalidClientChallengeFromRemote = 6,
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/// @brief An unexpected or unsupported message type was received
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InvalidMessageTypeFromRemote = 7,
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/// @brief A message is already being processed
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TooManyRequests = 8,
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/// @brief The received message result was invalid
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InvalidMessageResultFromRemote = 9,
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/// @brief An invalid Url parameter was set sending a message to the device over a local connection
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InvalidUrlParameter = 10,
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};
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/**
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* @brief A generic message to exchange during challenge-response authentication.
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*/
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typedef struct {
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/// @brief The type of message being sent.
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MessageType messageType;
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/**
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* @brief The random nonce created by the remote
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*
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* This nonce is a random number created by the remote, different for each unlock request.
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* It is set for all message types.
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*/
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uint32_t clientChallenge;
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/**
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* @brief A random number to sign by the remote
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*
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* This nonce is set by the server after receiving an initial message.
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* It is set for the message types `challenge`, `request`, and `response`.
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*/
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uint32_t serverChallenge;
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/**
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* @brief The response status for the previous message.
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*
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* It is set only for messages from the server, e.g. the `challenge` and `response` message types.
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* Must be set to `MessageAccepted` for other messages.
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*/
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MessageResult result;
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} Message;
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/**
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* @brief The signed version of a message.
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*
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*/
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typedef struct {
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/**
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* @brief The authentication code of the message
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*
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* The code is created by performing HMAC-SHA256
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* over the bytes of the `Message`.
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*/
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uint8_t mac[SHA256_MAC_SIZE];
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/// @brief The message
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Message message;
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} SignedMessage;
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constexpr size_t messageCounterSize = sizeof(uint32_t);
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#pragma pack(pop)
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constexpr int MESSAGE_CONTENT_SIZE = sizeof(Message);
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constexpr int SIGNED_MESSAGE_SIZE = sizeof(SignedMessage);
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/**
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* @brief A callback for messages received over the socket
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*
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* The first parameter is a pointer to the byte buffer.
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* The second parameter indicates the number of received bytes.
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*/
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typedef void (*MessageCallback)(uint8_t* payload, size_t length);
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/**
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* @brief A callback for socket errors
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*/
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typedef void (*ErrorCallback)(MessageResult event);
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