83 lines
2.6 KiB
C++
83 lines
2.6 KiB
C++
#pragma once
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#include <stdint.h>
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#include "config.h"
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class TimeCheck {
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public:
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/**
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* @brief Create a time checker instance
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*
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* Specify the allowed discrepancy between the time of a received message
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* and the device time (in seconds).
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*
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* A stricter (lower) value better prevents against replay attacks,
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* but may lead to issues when dealing with slow networks and other
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* routing delays.
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*
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* @param offset The allowed time discrepancy in both directions (seconds)
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*/
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TimeCheck(uint32_t allowedTimeOffset = 60);
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/**
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* @brief Configure an NTP server to get the current time
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*
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* @param offsetToGMT The timezone offset in seconds
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* @param offsetDaylightSavings The daylight savings offset in seconds
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* @param serverUrl The url of the NTP server
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*/
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void configureNTP(int32_t offsetToGMT, int32_t offsetDaylightSavings, const char* serverUrl);
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/**
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* @brief Print the current time to the serial output
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*
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* The time must be initialized by calling `configureNTP()` before use.
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*/
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void printLocalTime();
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/**
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* Gets the current epoch time
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*/
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uint32_t getEpochTime();
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/**
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* @brief The allowed time discrepancy (in seconds)
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*
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* Specifies the allowed discrepancy between the time of a received message
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* and the device time (in seconds).
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*
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* A stricter (lower) value better prevents against replay attacks,
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* but may lead to issues when dealing with slow networks and other
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* routing delays.
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*
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* @param offset The offset in both directions (seconds)
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*/
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void setMessageTimeAllowedOffset(uint32_t offset);
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/**
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* @brief Check wether the time of a message is within the allowed bounds regarding freshness.
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*
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* The timestamp is used to ensure 'freshness' of the messages,
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* i.e. that they are not unreasonably delayed or captured and
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* later replayed by an attacker.
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*
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* @param messageTime The timestamp of the message (seconds since epoch)
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* @return true The time is within the acceptable offset of the local time
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* @return false The message time is invalid
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*/
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bool isMessageTimeAcceptable(uint32_t messageTime);
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private:
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/**
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* @brief The allowed discrepancy between the time of a received message
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* and the device time (in seconds)
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*
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* A stricter (lower) value better prevents against replay attacks,
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* but may lead to issues when dealing with slow networks and other
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* routing delays.
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*/
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uint32_t allowedOffset;
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}; |