Implement interfaces for ESP32

include/interface/ESP32CryptoSource.h

@@ -0,0 +1,62 @@
+#pragma once
+
+#include "relay/interface/CryptoSource.h"
+#include "ESP32NoiseSource.h"
+
+class ESP32CryptoSource: CryptoSource {
+
+public:
+
+    ESP32CryptoSource(const char* rngInitTag);
+
+    bool isAvailable() override {
+        return true;
+    }
+
+    /**
+     * @brief Create a new random private key
+     * 
+     * @param key The output buffer where the key will be stored
+     * @return true The key was created
+     * @return false The key could not be created
+     */
+    bool createPrivateKey(PrivateKey* key) override;
+
+    /**
+     * @brief Create a the public key corresponding to a private key
+     * 
+     * @param privateKey The private key to use
+     * @param publicKey The output buffer where the public key will be stored
+     * @return true The key was created
+     * @return false The key could not be created
+     */
+    bool createPublicKey(const PrivateKey* privateKey, PublicKey* publicKey) override;
+
+    /**
+     * @brief Sign a message
+     * 
+     * @param message The message payload to include in the message
+     * @param length The length of the payload
+     * @param signature The output buffer where the signature is written
+     * @return true The signature was created
+     * @return false The signature creation failed
+     */
+    bool sign(const uint8_t *message, uint16_t length, Signature* signature, const PrivateKey* privateKey, const PublicKey* publicKey) override;
+
+    /**
+     * @brief Verify a message
+     *
+     * @param signature The message signature
+     * @param publicKey The public key with which the message was signed
+     * @param message The pointer to the message data
+     * @param length The length of the message
+     * @return true The signature is valid
+     * @return false The signature is invalid
+     */
+    bool
+    verify(const Signature* signature, const PublicKey* publicKey, const void *message, uint16_t length) override;
+
+private:
+
+    ESP32NoiseSource noise{};
+};

include/interface/ESP32NoiseSource.h

@@ -0,0 +1,64 @@
+#pragma once
+
+#include <NoiseSource.h>
+
+/// @brief The size of the internal buffer when generating entropy
+constexpr size_t randomNumberBatchSize = 32;
+
+/**
+ * @brief A noise source for crypto operations specifically for the ESP32.
+ * 
+ */
+class ESP32NoiseSource: public NoiseSource {
+
+public:
+    /**
+     * \brief Constructs a new random noise source.
+     */
+    ESP32NoiseSource();
+
+    /**
+     * \brief Destroys this random noise source.
+     */
+    ~ESP32NoiseSource() {}
+
+    /**
+     * @brief Determine if the noise source is still calibrating itself.
+     * 
+     * Noise sources that require calibration start doing so at system startup
+     * and then switch over to random data generation once calibration is complete.
+     * Since no random data is being generated during calibration, the output
+     * from `RNGClass::rand()` and `RNG.rand()` may be predictable.
+     * Use `RNGClass::available()` or `RNG.available()` to determine
+     * when sufficient entropy is available to generate good random values.
+     *
+     * It is possible that the noise source never exits calibration.  This can
+     * happen if the input voltage is insufficient to trigger noise or if the
+     * noise source is not connected.  Noise sources may also periodically
+     * recalibrate themselves.
+     *
+     * @return Returns true if calibration is in progress; false if the noise
+     * source is generating valid random data.
+     * 
+     */
+    bool calibrating() const override;
+
+    /**
+     * @brief Stirs entropy from this noise source into the global random
+     * number pool.
+     *
+     * This function should call `output()` to add the entropy from this noise
+     * source to the global random number pool.
+     *
+     * The noise source should batch up the entropy data, providing between
+     * 16 and 48 bytes of data each time.  If the noise source does not have
+     * sufficient entropy data at the moment, it should return without stiring
+     * the current data in.
+     */
+    void stir() override;
+
+private:
+
+    /// @brief Temporary buffer to hold random bytes before handing them to the crypto module
+    uint8_t data[randomNumberBatchSize];
+};

include/interface/ESP32StorageSource.h

@@ -0,0 +1,17 @@
+
+#include "relay/interface/StorageSource.h"
+
+class ESP32StorageSource: StorageSource {
+
+    bool writeByteAtIndex(uint8_t byte, uint16_t index) override;
+
+    bool canProvideStorageWithSize(uint16_t size) override;
+
+    bool commitData();
+
+    uint8_t readByteAtIndex(uint16_t index) override;
+
+    uint16_t readBytes(uint16_t startIndex, uint16_t count, uint8_t* output) override;
+
+    uint16_t writeBytes(uint8_t* bytes, uint16_t count, uint16_t startIndex) override;
+};

include/relay/interface/CryptoSource.h

@@ -0,0 +1,68 @@
+#pragma once
+
+#include <stdint.h>
+#include "relay/CryptoPrimitives.h"
+
+/**
+ * @brief An abstract definition of an instance capable of crypto operations
+ * 
+ */
+class CryptoSource {
+
+public:
+
+    /**
+     * @brief Indicate that the crypto functions can be used.
+     * 
+     * @return true The crypto functions are available
+     * @return false Some error prevents the use of the crypto functions.
+     */
+    virtual
+    bool isAvailable() = 0;
+
+    /**
+     * @brief Create a new random private key
+     * 
+     * @param key The output buffer where the key will be stored
+     * @return true The key was created
+     * @return false The key could not be created
+     */
+    virtual
+    bool createPrivateKey(PrivateKey* key) = 0;
+
+    /**
+     * @brief Create a the public key corresponding to a private key
+     * 
+     * @param privateKey The private key to use
+     * @param publicKey The output buffer where the public key will be stored
+     * @return true The key was created
+     * @return false The key could not be created
+     */
+    virtual
+    bool createPublicKey(const PrivateKey* privateKey, PublicKey* publicKey) = 0;
+
+    /**
+     * @brief Sign a message
+     * 
+     * @param message The message payload to include in the message
+     * @param length The length of the payload
+     * @param signature The output buffer where the signature is written
+     * @return true The signature was created
+     * @return false The signature creation failed
+     */
+    virtual
+    bool sign(const uint8_t *message, uint16_t length, Signature* signature, const PrivateKey* privateKey, const PublicKey* publicKey) = 0;
+
+    /**
+     * @brief Verify a message
+     * 
+     * @param signature The message signature
+     * @param publicKey The public key with which the message was signed
+     * @param message The pointer to the message data
+     * @param length The length of the message
+     * @return true The signature is valid
+     * @return false The signature is invalid
+     */
+    virtual
+    bool verify(const Signature* signature, const PublicKey* publicKey, const void *message, uint16_t length) = 0;
+};

include/relay/interface/StorageSource.h

@@ -0,0 +1,98 @@
+#pragma once
+
+#include <stdint.h>
+
+/**
+ * @brief An abstract interface for persistent storage
+ * 
+ * @note It is assumed that read operations are cached and therefore quick.
+ */
+class StorageSource {
+
+public:
+
+    /**
+     * @brief Write a byte to disk
+     * 
+     * @note The data is only persisted if the function `commitData()` is called afterwards.
+     * 
+     * @param byte The byte to write
+     * @param index The index where to write the byte
+     * @return true 
+     * @return false 
+     */
+    virtual
+    bool writeByteAtIndex(uint8_t byte, uint16_t index) = 0;
+
+    /**
+     * @brief Ensure that enough storage is available for all data
+     * 
+     * @param size 
+     * @return true The space was initialized an has sufficient size
+     * @return false 
+     */
+    virtual
+    bool canProvideStorageWithSize(uint16_t size) = 0;
+
+    /**
+     * @brief Write the data to persistent storage after a block of bytes was changed.
+     * 
+     * @return true The data was persisted
+     * @return false The data could not be saved
+     */
+    virtual
+    bool commitData() = 0;
+
+    /**
+     * @brief Read a single byte from persistent storage
+     * 
+     * @param index The index of the byte in the data
+     * @return uint8_t The byte at the given index
+     */
+    virtual
+    uint8_t readByteAtIndex(uint16_t index) = 0;
+
+    /**
+     * @brief Read a number of bytes from storage
+     * 
+     * @param startIndex The index of the start byte
+     * @param count The number of bytes to read
+     * @param output The location to write the bytes
+     * @return uint8_t The number of bytes read
+     */
+    virtual
+    uint16_t readBytes(uint16_t startIndex, uint16_t count, uint8_t* output) {
+        uint16_t endIndex = startIndex + count;
+        if (endIndex < startIndex) {
+            return 0; // Overflow
+        }
+        for (uint16_t i = 0; i < endIndex; i += 1) {
+            output[i] = readByteAtIndex(startIndex + i);
+        }
+        return count;
+    }
+
+    /**
+     * @brief Write a number of bytes to storage
+     * 
+     * @note The data is only persisted if the function `commitData()` is called afterwards.
+     * 
+     * @param bytes The memory holding the bytes
+     * @param count The number of bytes to write
+     * @param startIndex The index where the bytes should be written
+     * @return uint16_t The number of bytes written to storage
+     */
+    virtual
+    uint16_t writeBytes(uint8_t* bytes, uint16_t count, uint16_t startIndex) {
+        uint16_t endIndex = startIndex + count;
+        if (endIndex < startIndex) {
+            return 0; // Overflow
+        }
+        for (uint16_t i = 0; i < endIndex; i += 1) {
+            if (!writeByteAtIndex(bytes[i], startIndex + i)) {
+                return i; // Failed to write byte
+            }
+        }
+        return count;
+    }
+};

platformio.ini

@@ -18,6 +18,6 @@ lib_deps =
 	ottowinter/ESPAsyncWebServer-esphome@^3.0.0
 	arduino-libraries/Ethernet@^2.0.2
 	https://github.com/christophhagen/arduinoWebSockets#master
-	
+	rweather/Crypto@^0.4.0
 monitor_speed = 115200
 build_flags= -D WEBSOCKETS_NETWORK_TYPE=NETWORK_W5100

src/crypto/ESP32CryptoSource.cpp

@@ -0,0 +1,29 @@
+#include "interface/ESP32CryptoSource.h"
+
+#include <Ed25519.h>
+#include <RNG.h>
+#include <NoiseSource.h>
+
+ESP32CryptoSource::ESP32CryptoSource(const char* rngInitTag) {
+    RNG.begin(rngInitTag);
+    RNG.addNoiseSource(noise);
+}
+
+bool ESP32CryptoSource::createPrivateKey(PrivateKey* key) {
+    Ed25519::generatePrivateKey(key->bytes);
+    return true;
+}
+
+bool ESP32CryptoSource::createPublicKey(const PrivateKey* privateKey, PublicKey* publicKey) {
+    Ed25519::derivePublicKey(publicKey->bytes, privateKey->bytes);
+    return true;
+} 
+
+bool ESP32CryptoSource::sign(const uint8_t *message, uint16_t length, Signature* signature, const PrivateKey* privateKey, const PublicKey* publicKey) {
+    Ed25519::sign(signature->bytes, privateKey->bytes, publicKey->bytes, message, length);
+    return true;
+}
+
+bool ESP32CryptoSource::verify(const Signature* signature, const PublicKey* publicKey, const void *message, uint16_t length) {
+    return Ed25519::verify(signature->bytes, publicKey->bytes, message, length);
+}

src/crypto/ESP32NoiseSource.cpp

@@ -0,0 +1,18 @@
+#include "interface/ESP32NoiseSource.h"
+
+#include <esp_random.h>
+#include <bootloader_random.h>
+
+ESP32NoiseSource::ESP32NoiseSource() {
+    // Ensure that there is randomness even if Bluetooth and WiFi are disabled
+    bootloader_random_enable();
+}
+
+bool ESP32NoiseSource::calibrating() const {
+    return false;
+}
+
+void ESP32NoiseSource::stir() {
+    esp_fill_random(data, randomNumberBatchSize);
+    output(data, randomNumberBatchSize, randomNumberBatchSize * 8);
+}

src/crypto/ESP32StorageSource.cpp

@@ -0,0 +1,28 @@
+#include "interface/ESP32StorageSource.h"
+#include <EEPROM.h>
+
+bool ESP32StorageSource::writeByteAtIndex(uint8_t byte, uint16_t index) {
+    // TODO: What does return value mean?
+    EEPROM.writeByte((int) index, byte);
+    return true;
+}
+
+bool ESP32StorageSource::canProvideStorageWithSize(uint16_t size) {
+    return EEPROM.begin(size);
+}
+
+bool ESP32StorageSource::commitData() {
+    return EEPROM.commit();
+} 
+
+uint8_t ESP32StorageSource::readByteAtIndex(uint16_t index) {
+    return EEPROM.readByte((int) index);
+}
+
+uint16_t ESP32StorageSource::readBytes(uint16_t startIndex, uint16_t count, uint8_t* output) {
+    return EEPROM.readBytes(startIndex, output, count);
+}
+
+uint16_t ESP32StorageSource::writeBytes(uint8_t* bytes, uint16_t count, uint16_t startIndex) {
+    return EEPROM.writeBytes(startIndex, bytes, count);
+}