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https://github.com/CovidBraceletPrj/CovidBracelet.git
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Merge pull request #5 from CovidBraceletPrj/feature/exposure-notification-lib
Use PlatformIO Exposure Notification Library
This commit is contained in:
Patrick Rathje
GitHub
commit
5fea4b55e7
@ -1,52 +0,0 @@
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#include "exposure-notification.h"
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#include "time.h"
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int main(int argc, char **argv) {
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// first init everything
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// TODO: More randomization, we init with NULL to let en init mbdet entropy for us
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en_init(NULL);
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// get the currentTime
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time_t currentTime = time(NULL);
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// The periodKey changes each EN_TEK_ROLLING_PERIOD intervals
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ENIntervalNumber periodInterval = en_get_interval_number_at_period_start(currentTime);
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ENPeriodKey periodKey;
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ENPeriodIdentifierKey periodIdentifierKey;
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ENPeriodMetadataEncryptionKey periodMetadaEncryptionKey;
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// setup period keys at the beginning
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// in theory you could let them generate automatically setting periodInterval to 0
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en_generate_and_derive_period_keys(&periodKey, &periodIdentifierKey, &periodMetadaEncryptionKey);
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char metadata[128] = "";
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while(1) {
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// we check the current time to know if we actually need to regenerate anything
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currentTime = time(NULL);
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ENIntervalNumber currentInterval = en_get_interval_number(currentTime);
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// we check if we need to generate new keys
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if (currentInterval - periodInterval >= EN_TEK_ROLLING_PERIOD) {
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periodInterval = en_get_interval_number_at_period_start(currentTime);
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en_generate_and_derive_period_keys(&periodKey, &periodIdentifierKey, &periodMetadaEncryptionKey);
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// TODO: Store new periodKey with periodInterval
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}
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// we now generate the new interval identifier and re-encrypt the metadata
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ENIntervalIdentifier intervalIdentifier;
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en_derive_interval_identifier(&intervalIdentifier, &periodIdentifierKey, currentInterval);
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char encryptedMetadata[sizeof(metadata)];
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en_encrypt_interval_metadata(&periodMetadaEncryptionKey, &intervalIdentifier, metadata, encryptedMetadata, sizeof(metadata));
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// broadcast intervalIdentifier plus encryptedMetada according to specs
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// TODO: receive packets and store them
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// repeat for 10-20 minutes
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}
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return 0;
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}
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@ -1,170 +0,0 @@
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/*
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* Copyright (c) 2020 Patrick Rathje
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef EXPOSURE_NOTIFICATION_H
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#define EXPOSURE_NOTIFICATION_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include <time.h>
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#include <stdint.h>
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#include <stddef.h>
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#ifndef EN_TEK_ROLLING_PERIOD
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#define EN_TEK_ROLLING_PERIOD 144
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#endif
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#ifndef EN_INTERVAL_LENGTH
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#define EN_INTERVAL_LENGTH 600
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#endif
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#ifndef EN_INIT_MBEDTLS_ENTROPY
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#define EN_INIT_MBEDTLS_ENTROPY 1
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#endif
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/*
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* Type: _ENBaseKey
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* --------------------
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* 16 Byte base key definition
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*/
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typedef struct _ENBaseKey { unsigned char b[16];} _ENBaseKey;
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/*
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* Type: ENIntervalNumber
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* --------------------
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* The number of the 10 minute interval
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*/
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typedef uint32_t ENIntervalNumber;
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/*
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* Type: ENPeriodKey
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* --------------------
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* 16 Byte temporary exposure key used throughout a rolling period (one day)
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*/
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typedef struct _ENBaseKey ENPeriodKey;
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/*
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* Type: ENPeriodIdentifierKey
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* --------------------
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* 16 Byte key used throughout each period to encrypt the identifier for each interval
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*/
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typedef struct _ENBaseKey ENPeriodIdentifierKey;
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/*
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* Type: ENIntervalIdentifier
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* --------------------
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* 16 Byte identifier used within the packet
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*/
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typedef struct _ENBaseKey ENIntervalIdentifier;
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/*
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* Type: ENPeriodMetadataEncryptionKey
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* --------------------
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* 16 Byte key used throughout each interval to encrypt the metadata within one period
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*/
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typedef struct _ENBaseKey ENPeriodMetadataEncryptionKey;
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/*
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* Type: ENPeriodMetadataEncryptionKey
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* --------------------
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* 16 Byte key used throughout each interval to encrypt the metadata within one period
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*/
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typedef struct _ENBaseKey ENPeriodMetadataEncryptionKey;
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typedef int (*ENRandomBytesCallback)(void *buf, size_t len);
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/*
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* Function: en_init
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* --------------------
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* Initializes the random number generator. Use NULL to initialize with the fallback random_bytes_func
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*/
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int en_init(ENRandomBytesCallback user_random_bytes_callback);
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/*
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* Function: en_get_interval_number
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* --------------------
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* computes the interval number according to the given unix timestamp. Each interval lasts for EN_INTERVAL_LENGTH secs (defaults to 10 minutes).
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*/
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ENIntervalNumber en_get_interval_number(time_t timestamp);
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/*
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* Function: en_get_period_start_interval_number
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* --------------------
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* computes the first interval number for the period given by the unix timestamp.
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*/
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ENIntervalNumber en_get_interval_number_at_period_start(time_t timestamp);
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/*
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* Function: en_generate_period_key
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* --------------------
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* Generates a new period key using a cryptographic number generator. Used when the next period is dues (once a day).
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*/
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void en_generate_period_key(ENPeriodKey* periodKey);
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/*
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* Function: en_derive_period_identifier_key
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* --------------------
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* Derives the interval identifier key based on the current period key
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*/
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void en_derive_period_identifier_key(ENPeriodIdentifierKey *periodIdentifierKey, const ENPeriodKey *periodKey);
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/*
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* Function: en_derive_interval_identifier
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* --------------------
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* Get the identifier for a specific interval based on the identifierKey
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*/
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void en_derive_interval_identifier(ENIntervalIdentifier *intervalIdentifier, const ENPeriodIdentifierKey *periodIdentifierKey, const ENIntervalNumber intervalNumber);
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/*
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* Function: en_derive_period_metadata_encryption_key
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* --------------------
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* Derives the interval metadata encryption key based on the current period key
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*/
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void en_derive_period_metadata_encryption_key(ENPeriodMetadataEncryptionKey *periodMetadataEncryptionKey, const ENPeriodKey *periodKey);
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/*
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* Function: en_encrypt_interval_metadata
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* --------------------
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* Encrypts the metadata.
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*/
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void en_encrypt_interval_metadata(const ENPeriodMetadataEncryptionKey *periodMetadataEncryptionKey, const ENIntervalIdentifier *intervalIdentifier, unsigned char *input, unsigned char *output, size_t inputSize);
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/*
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* Function: en_decrypt_interval_metadata
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* --------------------
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* Decrypts the metadata.
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*/
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void en_decrypt_interval_metadata(const ENPeriodMetadataEncryptionKey *periodMetadataEncryptionKey, const ENIntervalIdentifier *intervalIdentifier, unsigned char *input, unsigned char *output, size_t inputSize);
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/*
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* Function: en_generate_period_relevant_keys()
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* --------------------
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* This function generates all period keys at once (convenient right?)
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*/
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static inline void en_generate_and_derive_period_keys(ENPeriodKey *periodKey, ENPeriodIdentifierKey *periodIdentifierKey, ENPeriodMetadataEncryptionKey *periodMetadataEncryptionKey) {
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en_generate_period_key(periodKey);
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en_derive_period_identifier_key(periodIdentifierKey, periodKey);
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en_derive_period_metadata_encryption_key(periodMetadataEncryptionKey, periodKey);
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}
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#ifdef __cplusplus
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}
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#endif
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#endif
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@ -1,14 +0,0 @@
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{
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"description": "exposure-notification",
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"frameworks": "*",
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"keywords": "exposure, notification, contact, tracking, tracing",
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"name": "exposure-notification",
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"platforms": "*",
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"version": "0.1",
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"dependencies": [
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{
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"name": "mbedtls",
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"version": "^2.16.4"
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}
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]
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}
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@ -1,140 +0,0 @@
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/*
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* Copyright (c) 2020 Patrick Rathje
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#if EN_INCLUDE_ZEPHYR_DEPS
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#include <zephyr.h>
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#include <zephyr/types.h>
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#include <stddef.h>
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#include <sys/printk.h>
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#include <sys/util.h>
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#endif
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#include <string.h>
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#include "mbedtls/entropy.h"
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#include "mbedtls/ctr_drbg.h"
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#include "mbedtls/hkdf.h"
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#include "mbedtls/sha256.h"
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#include "mbedtls/aes.h"
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#include "exposure-notification.h"
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static mbedtls_ctr_drbg_context ctr_drbg;
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static ENRandomBytesCallback random_bytes_callback = NULL;
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int en_mbedtls_random_bytes_fallback(void *buf, size_t len) {
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return mbedtls_ctr_drbg_random(&ctr_drbg, buf, len);
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}
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#if EN_INIT_MBEDTLS_ENTROPY
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int init_mbedtls_entropy() {
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mbedtls_entropy_context entropy;
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mbedtls_entropy_init( &entropy );
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static char *personalization = "exposure-notification";
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mbedtls_ctr_drbg_init( &ctr_drbg );
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int ret = mbedtls_ctr_drbg_seed( &ctr_drbg , mbedtls_entropy_func, &entropy,
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(const unsigned char *) personalization,
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strlen( personalization ) );
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return ret;
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}
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#endif
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int en_init(ENRandomBytesCallback user_random_bytes_callback) {
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int ret = 0;
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#if EN_INIT_MBEDTLS_ENTROPY
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ret = init_mbedtls_entropy();
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#endif
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// Fallback to mbedtls random bytes implementation and init the entropy
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if (user_random_bytes_callback == NULL) {
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random_bytes_callback = en_mbedtls_random_bytes_fallback;
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} else {
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random_bytes_callback = user_random_bytes_callback;
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}
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return ret;
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}
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ENIntervalNumber en_get_interval_number(time_t timestamp) {
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return timestamp / EN_INTERVAL_LENGTH;
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}
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ENIntervalNumber en_get_interval_number_at_period_start(time_t timestamp) {
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ENIntervalNumber current = en_get_interval_number(timestamp);
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// round to period start
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return (current/EN_TEK_ROLLING_PERIOD)*EN_TEK_ROLLING_PERIOD;
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}
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void en_generate_period_key(ENPeriodKey* periodKey) {
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// TODO: error handling
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random_bytes_callback(periodKey->b, sizeof(periodKey->b));
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}
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void en_derive_period_identifier_key(ENPeriodIdentifierKey *periodIdentifierKey, const ENPeriodKey *periodKey) {
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const mbedtls_md_info_t *sha256_info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
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// TODO: Include \0 in the string?
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// TODO: Check return value
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// TODO: Is this utf-8 info correct?
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// TODO: Correct erros in en_get_period_metadata_encryption_key as well!
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const unsigned char info[7] = "EN-RPIK";
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mbedtls_hkdf(sha256_info, 0, 0, periodKey->b, sizeof(periodKey->b), info, sizeof(info), periodIdentifierKey->b, sizeof(periodIdentifierKey->b));
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}
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void en_derive_interval_identifier(ENIntervalIdentifier *intervalIdentifier, const ENPeriodIdentifierKey *periodIdentifierKey, const ENIntervalNumber intervalNumber) {
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unsigned char paddedData[16] = "EN-RPI";
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// copy intervalNumber in little endian format
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paddedData[12] = (intervalNumber >> 0) &0xFF;
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paddedData[13] = (intervalNumber >> 8) &0xFF;
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paddedData[14] = (intervalNumber >> 16) &0xFF;
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paddedData[15] = (intervalNumber >> 24) &0xFF;
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mbedtls_aes_context aes;
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mbedtls_aes_init( &aes );
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// Encrypt the padded data to get the identifier
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mbedtls_aes_setkey_enc( &aes, (const unsigned char*) periodIdentifierKey->b, sizeof(periodIdentifierKey->b) * 8 );
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mbedtls_aes_crypt_ecb(&aes, MBEDTLS_AES_ENCRYPT, paddedData, intervalIdentifier->b);
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mbedtls_aes_free( &aes );
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}
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void en_derive_period_metadata_encryption_key(ENPeriodMetadataEncryptionKey *periodMetadataEncryptionKey, const ENPeriodKey *periodKey) {
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const mbedtls_md_info_t *sha256_info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
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const unsigned char info[7] = "EN-AEMK";
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mbedtls_hkdf(sha256_info, 0, 0, periodKey->b, sizeof(periodKey->b), info, sizeof(info), periodMetadataEncryptionKey->b, sizeof(periodMetadataEncryptionKey->b));
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}
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void en_encrypt_interval_metadata(const ENPeriodMetadataEncryptionKey *periodMetadataEncryptionKey, const ENIntervalIdentifier *intervalIdentifier, unsigned char *input, unsigned char *output, size_t inputSize) {
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mbedtls_aes_context aes;
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mbedtls_aes_init( &aes );
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// Encrypt the padded data to get the identifier
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size_t nonceOffset = 0;
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unsigned char nonceCounter[16];
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unsigned char streamBlock[16];
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// init nonce/IV to intervalIdentifer
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memcpy(nonceCounter, intervalIdentifier->b, sizeof(nonceCounter));
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memset(streamBlock, 0, sizeof(streamBlock));
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mbedtls_aes_setkey_enc( &aes, (const unsigned char*) periodMetadataEncryptionKey->b, sizeof(periodMetadataEncryptionKey->b) * 8 );
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mbedtls_aes_crypt_ctr(&aes, inputSize, &nonceOffset, nonceCounter, streamBlock, input, output);
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mbedtls_aes_free( &aes );
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}
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void en_decrypt_interval_metadata(const ENPeriodMetadataEncryptionKey *periodMetadataEncryptionKey, const ENIntervalIdentifier *intervalIdentifier, unsigned char *input, unsigned char *output, size_t inputSize) {
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en_encrypt_interval_metadata(periodMetadataEncryptionKey, intervalIdentifier, input, output, inputSize);
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}
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@ -22,14 +22,18 @@ build_flags =
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# For testing: -DUNITY_EXCLUDE_SETJMP_H=1
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-DEN_INCLUDE_ZEPHYR_DEPS=1
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-DEN_INIT_MBEDTLS_ENTROPY=0
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lib_deps = exposure-notification
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lib_deps =
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prathje/exposure-notification @ ^0.1
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lib_ignore =
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mbedtls
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[env:desktop]
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platform = native
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test_ignore = test_embedded
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lib_compat_mode = off
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lib_deps = mbedtls@~2
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lib_deps =
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mbedtls@~2
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prathje/exposure-notification @ ^0.1
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build_flags =
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-Iinclude/desktop
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-Iinclude/tls_config
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