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

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+#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

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+
+#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;
+};