Crypto works!

src/mesh/CryptoEngine.h

@@ -5,27 +5,46 @@
 /**
  * see docs/software/crypto.md for details.
  *
- * The NONCE is constructed by concatenating:
- * a 32 bit sending node number + a 64 bit packet number + a 32 bit block counter (starts at zero)
  */
 
 class CryptoEngine
 {
+  protected:
+    /** Our per packet nonce */
+    uint8_t nonce[16];
+
   public:
+    virtual ~CryptoEngine() {}
+
     /**
      * Set the key used for encrypt, decrypt.
      *
      * As a special case: If all bytes are zero, we assume _no encryption_ and send all data in cleartext.
      *
-     * @param numBytes must be 32 for now (AES256)
+     * @param numBytes must be 16 (AES128), 32 (AES256) or 0 (no crypt)
+     * @param bytes a _static_ buffer that will remain valid for the life of this crypto instance (i.e. this class will cache the
+     * provided pointer)
      */
-    void setKey(size_t numBytes, const uint8_t *bytes);
+    virtual void setKey(size_t numBytes, uint8_t *bytes);
 
     /**
      * Encrypt a packet
      *
      * @param bytes is updated in place
      */
-    void encrypt(uint32_t fromNode, uint64_t packetNum, size_t numBytes, uint8_t *bytes);
-    void decrypt(uint32_t fromNode, uint64_t packetNum, size_t numBytes, uint8_t *bytes);
-};
+    virtual void encrypt(uint32_t fromNode, uint64_t packetNum, size_t numBytes, uint8_t *bytes);
+    virtual void decrypt(uint32_t fromNode, uint64_t packetNum, size_t numBytes, uint8_t *bytes);
+
+  protected:
+    /**
+     * Init our 128 bit nonce for a new packet
+     *
+     * The NONCE is constructed by concatenating (from MSB to LSB):
+     * a 64 bit packet number (stored in little endian order)
+     * a 32 bit sending node number (stored in little endian order)
+     * a 32 bit block counter (starts at zero)
+     */
+    void initNonce(uint32_t fromNode, uint64_t packetNum);
+};
+
+extern CryptoEngine *crypto;