Create JWT token on receiver side

JWT token script:

import com.sap.gateway.ip.core.customdev.util.Message;

import io.jsonwebtoken.Claims

import io.jsonwebtoken.Jwts

import io.jsonwebtoken.Header

import io.jsonwebtoken.JwtBuilder

import io.jsonwebtoken.SignatureAlgorithm

import io.jsonwebtoken.impl.DefaultClaims

import java.security.KeyFactory

import java.security.PrivateKey

import java.security.spec.EncodedKeySpec

import java.security.spec.PKCS8EncodedKeySpec

import java.time.LocalDateTime;

import java.time.ZoneId



def Message processData(Message message) {


def mProp = message.getProperties();

String keyString = mProp.get("privateKey"); // Provided by the receiver.

LocalDateTime now = LocalDateTime.now();

Date nowDate = Date.from(now.atZone(ZoneId.systemDefault()).toInstant());

Date expDate = Date.from(now.plusMinutes(60).atZone(ZoneId.systemDefault()).toInstant());

Map<String, Object> header = new HashMap<String, Object>();



header.put("alg", "PS256");

header.put("typ", "JWT");

String kid = mProp.get("kid");

header.put("kid", kid);

message.setProperty("JWT Token Header",header)

Claims claims = new DefaultClaims();

String iss = mProp.get("clientID");

claims.put("iss", iss);

claims.put("scope", "restlets,rest_webservices");

String aud = mProp.get("Audience");

claims.put("aud", aud);


//claims.put("region","dummy");

message.setProperty("JWT Token Payload",claims);

/* Create JWT json with JwtBuilder */

JwtBuilder jwtBuilder = Jwts.builder()

.setClaims(claims)

.setIssuedAt(nowDate)

.setExpiration(expDate)

.setHeader((Map<String, Object>) header);

byte[] keyBytes = Base64.getDecoder().decode(keyString);

KeyFactory kf = KeyFactory.getInstance("RSA");

EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);

PrivateKey privateKey = kf.generatePrivate(keySpec);

String jwtToken = (jwtBuilder.signWith(SignatureAlgorithm.PS256, kf.generatePrivate(keySpec)).compact());

message.setBody(jwtToken)

return message;

}


After that need to get the assertion and set signed jwt with below script.




Set Signed JWT:



import com.sap.gateway.ip.core.customdev.util.Message;

import java.util.HashMap;

def Message processData(Message message) {

def assertion = message.getBody(java.lang.String) as String;

body = "grant_type=client_credentials" + "&client_assertion_type="+"urn:ietf:params:oauth:client-assertion-type:jwt-bearer"+"&client_assertion="+assertion;

message.setHeader("Content-Type", "application/x-www-form-urlencoded");

message.setBody(body);

return message;

}