firmware/src/portduino/CrossPlatformCryptoEngine.cpp

#include "AES.h"
#include "CTR.h"
#include "CryptoEngine.h"
#include "configuration.h"

/** A platform independent AES engine implemented using Tiny-AES
 */
class CrossPlatformCryptoEngine : public CryptoEngine
{

    CTRCommon *ctr = NULL;

  public:
    CrossPlatformCryptoEngine() {}

    ~CrossPlatformCryptoEngine() {}

    /**
     * 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 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)
     */
    virtual void setKey(const CryptoKey &k)
    {
        CryptoEngine::setKey(k);
        DEBUG_MSG("Installing AES%d key!\n", key.length * 8);
        if (ctr) {
            delete ctr;
            ctr = NULL;
        }
        if (key.length != 0) {
            if (key.length == 16)
                ctr = new CTR<AES128>();
            else
                ctr = new CTR<AES256>();

            ctr->setKey(key.bytes, key.length);
        }
    }

    /**
     * Encrypt a packet
     *
     * @param bytes is updated in place
     */
    virtual void encrypt(uint32_t fromNode, uint64_t packetNum, size_t numBytes, uint8_t *bytes)
    {
        if (key.length > 0) {
            uint8_t stream_block[16];
            static uint8_t scratch[MAX_BLOCKSIZE];
            size_t nc_off = 0;

            // DEBUG_MSG("ESP32 encrypt!\n");
            initNonce(fromNode, packetNum);
            assert(numBytes <= MAX_BLOCKSIZE);
            memcpy(scratch, bytes, numBytes);
            memset(scratch + numBytes, 0,
                   sizeof(scratch) - numBytes); // Fill rest of buffer with zero (in case cypher looks at it)

            ctr->setIV(nonce, sizeof(nonce));
            ctr->setCounterSize(4);
            ctr->encrypt(bytes, scratch, numBytes);
        }
    }

    virtual void decrypt(uint32_t fromNode, uint64_t packetNum, size_t numBytes, uint8_t *bytes)
    {
        // For CTR, the implementation is the same
        encrypt(fromNode, packetNum, numBytes, bytes);
    }

  private:
};

CryptoEngine *crypto = new CrossPlatformCryptoEngine();