Hi all,
i'm trying to setup a backend system able to send push notification to mobile app (not developed in creatio) through FCM rest API.
The first hurdle is obtaining a valid token to authenticate to notification api exposed by firebase. In order to obtain this token i do have to call another rest api passing a jwt token generated by me and signed by a private key downloaded from fcm.
I've got a code (pasted below) that manages to generate this encrypted token and it's working in visual studio. But if i try to use it in a script task i got the exception
'RSA' does not contain a definition for 'ImportPkcs8PrivateKey' and no accessible extension method 'ImportPkcs8PrivateKey' accepting a first argument of type 'RSA' could be found (are you missing a using directive or an assembly reference?)
As far as i know this exception is thrown if .net core being used is version 5 or below. But i'm on a demo instance with creation 8.2.0.4183 which should be already using net core 6 right?
Do you have any suggestion? (the flow is already configured to import System.Security.Cryptography)
--code--
var now = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
var header = new Dictionary
{
{ "alg", "RS256" },
{ "typ", "JWT" }
};
string headerJson = JsonConvert.SerializeObject(header);
string encodedHeader = Convert.ToBase64String(Encoding.UTF8.GetBytes(headerJson)).TrimEnd('=').Replace('+', '-').Replace('/', '_');
var payload = new Dictionary
{
{ "iss", CLIENT_EMAIL },
{ "scope", SCOPE },
{ "aud", TOKEN_URI },
{ "iat", now },
{ "exp", now + 3600 }
};
string payloadJson = JsonConvert.SerializeObject(payload);
string encodedPayload = Convert.ToBase64String(Encoding.UTF8.GetBytes(payloadJson)).TrimEnd('=').Replace('+', '-').Replace('/', '_');
string unsignedJwt = $"{encodedHeader}.{encodedPayload}";
byte[] dataBytes = Encoding.UTF8.GetBytes(unsignedJwt);
// Decode PEM -> PKCS#8 bytes
string cleanKey = PRIVATE_KEY
.Replace("-----BEGIN PRIVATE KEY-----", "")
.Replace("-----END PRIVATE KEY-----", "")
.Replace("\\n", "\n") // ← decodifica reale da stringa JSON
.Trim();
byte[] privateKeyBytes = Convert.FromBase64String(cleanKey);
// Firma con RSA-SHA256
byte[] signature;
using (var rsa = RSA.Create())
{
rsa.ImportPkcs8PrivateKey(privateKeyBytes, out _);
signature = rsa.SignData(dataBytes, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
}
string encodedSignature = Convert.ToBase64String(signature)
.TrimEnd('=').Replace('+', '-').Replace('/', '_');
string jwt = $"{unsignedJwt}.{encodedSignature}";
return true;
