MultiFS Branch

[tobozo]

Discussion around this PR chrisjoyce911#92

Followup for chrisjoyce911#25, chrisjoyce911#47, chrisjoyce911#60, chrisjoyce911#74, chrisjoyce911#79, chrisjoyce911#91

Functional changes

• SPIFFS is removed from the library core and replaced with an optional fs::FS filesystem abstraction.
• JSON Manifest accepts new keys spiffs, littlefs, fatfs holding path to filesystem image
• When one of the new keys is set in the manifest, execOTA will also flash the spiffs partition with the provided filesystem image (which can also be signed)

⚠️ ESP32FOTA should detect when #include <LittleFS> (on any other filesystem) is included from the sketch, and automatically use that filesystem to verify certificate signatures. If no filesystem is detected, firmware signature check will always fail!

// include filesystem first !

//#include <SD.h>
//#include <SD_MMC.h>
//#include <SPIFFS.h>
#include <LittleFS.h>
//#include <PSRamFS.h>
#include <esp32fota.h>

A new set of helper objects were added to handle the crypto assets in mixed situations:

// pick pubkey/rootca from filesystem
CryptoFileAsset( const char* path, fs::FS* filesystem ); 
// pick pubkey/rootca from progmem
CryptoMemAsset( const char* name, const char* bytes, size_t len );

Crypto asset usage with progmem:

// could also be a byte array
const char* rsa_key_pub = R"RSA_KEY(
-----BEGIN PUBLIC KEY-----
BlahBlahBlah ... My RSA Key ... BlahBlahBlah
BlahBlahBlah ... My RSA Key ... BlahBlahBlah
BlahBlahBlah ... My RSA Key ... BlahBlahBlah
-----END PUBLIC KEY-----
)RSA_KEY";

CryptoMemAsset *MyRSAKey = new CryptoMemAsset("RSA Public Key", rsa_key_pub, strlen(rsa_key_pub)+1 );

void setup()
{
     // ...
    esp32FOTA.setPubKey( MyRSAKey );

}

Crypto asset usage with filesystem (can be different for each file):

CryptoAsset* MyRSAKey = new CryptoFileAsset( "/path/to/public.key", &LittleFS  );
CryptoAsset* MyRootCA = new CryptoFileAsset( "/path/to/root_ca", &SD  );

void setup()
{
    // ....
    esp32FOTA.setPubKey( MyRSAKey );
    esp32FOTA.setRootCA( MyRootCA );
}

Sketches using more than one filesystem or compiled with older versions of platformio or may use this new method:

    esp32FOTA.setCertFileSystem( &LittleFS ); // works with &SD, &SD_MMC, &SPIFFS