LetsEncrypt certificate returns CertPathValidatorException

[Alphexoed]

Good evening everyone,

I'm trying to do do SSL Pinning for my app and the Lets Encrypt certificate (ISRG Root X1) is returning CertPathValidatorException: Trust anchor for certification path not found.

I've tried changing certificates but no luck, I've read on one of these issues that its the key store but still didn't work out.

I'm on Android Studios using Kotlin, using Fuel for the web requests, here is the code I have, thanks!

fun pinning(ctx: Context): Pair<SSLSocketFactory, KeyStore> {
    val cf: CertificateFactory = CertificateFactory.getInstance("X.509")
    val caInput: InputStream = BufferedInputStream(ctx.resources.openRawResource(R.raw.isrgrootx1))
    val ca: X509Certificate = caInput.use {
        cf.generateCertificate(it) as X509Certificate
    }
    Log.println(Log.DEBUG, "SYSTEM-CA", ca.subjectDN.toString())

    // Create a KeyStore containing our trusted CAs
    val keyStoreType = KeyStore.getDefaultType()
    val keyStore = KeyStore.getInstance(keyStoreType).apply {
        load(null, null)
        setCertificateEntry("ca", ca)
    }

    // Create a TrustManager that trusts the CAs inputStream our KeyStore
    val tmfAlgorithm: String = TrustManagerFactory.getDefaultAlgorithm()
    val tmf: TrustManagerFactory = TrustManagerFactory.getInstance(tmfAlgorithm).apply {
        init(keyStore)
    }

    // Create an SSLContext that uses our TrustManager
    val context: SSLContext = SSLContext.getInstance("TLS").apply {
        init(null, tmf.trustManagers, null)
    }

    return Pair(context.socketFactory, keyStore)
}


val (pin, key) = pinning(this)
FuelManager.instance.socketFactory = pin
FuelManager.instance.keystore = key
Log.println(Log.INFO, "FUEL-MANAGER", "Imported instances successfully")

The FuelManager is run as soon as the app starts (override fun onStart())