Create Java RSAKey from given private key and public key as string variables

Question

For the initial implementation I used RSEKeyGenerator to generate a random key for my project, but now I would like to build the RSAKey using the proper keys, which I have available as strings in two variables.

try {
    RSAKey rsaJWK = new RSAKeyGenerator(RSA_KEY_SIZE_BITS).generate();

    Map<String, Object> header = new HashMap<>();
    header.put("alg", "RS256");
    header.put("x5t#S256", "hash256");

    Map<String, Object> payload = new HashMap<>();
    payload.put("iss", "issuer");
    payload.put("aud", "audience");
    payload.put("exp", Long.toString(Instant.now().plus(8,ChronoUnit.HOURS).getEpochSecond()));
    payload.put("iat", Long.toString(Instant.now().minus(4, ChronoUnit.HOURS).getEpochSecond()));
    payload.put("nbf", Long.toString(Instant.now().minus(3, ChronoUnit.HOURS).getEpochSecond()));
    payload.put("jti", "jtiId");

    JWSSigner signer = new RSASSASigner(rsaJWK);
    JWSObject jwsObject = new JWSObject(
                    JWSHeader.parse(header),
                    new Payload(payload));
    jwsObject.sign(signer);
    jwt2 = jwsObject.serialize();
 } catch (JOSEException | ParseException e) {
    e.printStackTrace();
 }

The keys are received as string of the form

and

Any idea as to build an RSAKey variable to use in the code line "jwsObject.sign(signer)" is appreciated

Answer 1

The import of PEM keys is directly supported, eg for the private key:

String pkcs8Pem = "-----BEGIN PRIVATE KEY-----\r\n"
        + "MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQC6cXloNrocJ8sw\r\n"
        ...
        + "BviZm5AFCQWfke4LZo5mOS10\r\n"
        + "-----END PRIVATE KEY-----";
RSAKey privRsaJWK = RSAKey.parseFromPEMEncodedObjects(pkcs8Pem).toRSAKey();
...
JWSSigner signer = new RSASSASigner(privRsaJWK);

and analogously for the public key:

String x509Pem = "-----BEGIN PUBLIC KEY-----\r\n"
        + "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAunF5aDa6HCfLMMI/MZLT\r\n"
        ...
        + "GwIDAQAB\r\n"
        + "-----END PUBLIC KEY-----";
RSAKey pubRsaJWK = RSAKey.parseFromPEMEncodedObjects(x509Pem).toRSAKey();
...
JWSVerifier verifier = new RSASSAVerifier(pubRsaJWK);

For valid (and related keys) signing and verification works this way.

However, your private key seems to be corrupted and throws an exception. You can check your private key with:

openssl rsa -in <path to private pem file> -check

which will give the following error:

RSA key error: iqmp not inverse of q

Create Java RSAKey from given private key and public key as string variables

Question

1 answers

solution1
0 2022-07-14 21:19:40

Create Java RSAKey from given private key and public key as string variables

Question

1 answers

solution1 0 2022-07-14 21:19:40

solution1
0 2022-07-14 21:19:40