Decrypting OpenID Connect Encrypted ID Tokens

The WSO2 Identity Server provides encrypted ID Tokens to address some security vulnerabilities in the production environment.

Unencrypted JWT ID tokens can contain only two base64 encoded portions separated by "."
```
<header>.<body>
```
The following is an example where unencrypted ID tokens contain only two base64 encoded portions separated by "."
```
eyJhbGciOiJSUzI1NiJ9.eyJzdWIiOiJhbGljZSIsImlzcyI6Imh0dHBzOlwvXC9jMmlkLmNvbSIsImlhdCI6MTQxNjE1ODU0MX0
```

Encrypted ID Tokens containing five base64 encoded portions separated by "."

<header>.<Encrypted_Key>.<Initialization_Vector>.<Ciphertext>.<Authentication_Tag>

The following is an example where the encrypted ID token contains five base64 encoded portions separated by "."

eyJ4NXQiOiJOVEF4Wm1NeE5ETXlaRGczTVRVMVpHTTBNekV6T0RKaFpXSTRORE5sWkRVMU9HRmtOakZpTVEiLCJraWQiOiJOVEF4Wm1NeE5ETXlaRGczTVRVMVpHTTBNekV6T0RKaFpXSTRORE5sWkRVMU9HRmtOakZpTVEiLCJlbmMiOiJBMjU2R0NNIiwiYWxnIjoiUlNBMV81In0.Zwp2xDvYER9lAo43QrYrcaKz-tPLFPYZb2s4RontDDVyvdo-seYl6II2C1Wb4cQhXdipcB_Qj093xvLrJyZXWxeavqYhryeuHi2jgcs59MfV1U9hMaKqqjVN1pcZYSrxDzn5leBF5bw7_YKaD_R6cFY8VtpVv5j_U8WohtyIjM7_n2CsZ55vY8MUHCAYxzXK9_s75e6Ug8L4MEqpgeoJGQzYCxFrBFgGyDMv1jadLwNl4Y3yLhv4RLtQMU5AM6nODI601UfYdrapObF3mpl_74H_YdRqT28LepGMtkEXbjeRgB-FiFGLvYlrK4wygczLBKrcviVyzyhrIrqz3TYV3g.Lf5lECzAdyAGgP8t.SHBUZoWkqwW_7u0GElrUqX1tewqRaUMWdGPHxpLRPmpVuc7FwQ27-kdsQ6O1_twhZ7uzjzZaEkatNhMxy9k10733-r4GT1lTGVqidKiBZq3mRQu7qJpcz7JWUroNFRLxhSoqpLpC8_tAhkohzG-mE42xdEh4tNDy3pBtAG0fe42WrLtWTuyg5lpmOYSppOc2Gb6LcDr4MmxFNPgoatF0edJSgO-CpFJQTcXn-22lU2g7o22x3RcBx9_KZH0At3g9y9uTuBncExOoBRK_ZweKOl0q76TaLiv5faXINW15xz9hILA.RGYIL7FaQqAIMPAiQdkOig

If you want to see the exact JSON values of the ID Token, you have to decrypt it.

The following is a simple Java program to decrypt the ID Token using the default wso2carbon.jks key store in WSO2 products.

package org.wso2.sample;

import com.nimbusds.jose.crypto.RSADecrypter;
import com.nimbusds.jwt.EncryptedJWT;

import java.io.InputStream;
import java.security.KeyStore;
import java.security.interfaces.RSAPrivateKey;

public class DecryptIDToken {
	public static void main(String[] args) throws Exception {

    	// Get keystore as a resource.
    	InputStream file = ClassLoader.getSystemResourceAsStream("wso2carbon.jks");
    	KeyStore keystore = KeyStore.getInstance(KeyStore.getDefaultType());
    	keystore.load(file, "wso2carbon".toCharArray());

    	String alias = "wso2carbon";

    	// Get the private key. Password for the key store is 'wso2carbon'.
    	RSAPrivateKey privateKey = (RSAPrivateKey) keystore.getKey(alias, "wso2carbon".toCharArray());

    	// Enter encrypted JWT String here.
    	String encryptedJWTString = "eyJ4NXQiOiJOVEF4Wm1NeE5ETXlaRGczTVRVMVpHTTBNekV6T0RKaFpXSTRORE5sWkRVMU9HRmtOakZp" +
            	"TVEiLCJraWQiOiJOVEF4Wm1NeE5ETXlaRGczTVRVMVpHTTBNekV6T0RKaFpXSTRORE5sWkRVMU9HRmtOakZpTVEiLCJlbmMiOiJ" +
            	"BMjU2R0NNIiwiYWxnIjoiUlNBMV81In0.Zwp2xDvYER9lAo43QrYrcaKz-tPLFPYZb2s4RontDDVyvdo-seYl6II2C1Wb4cQhXd" +
            	"ipcB_Qj093xvLrJyZXWxeavqYhryeuHi2jgcs59MfV1U9hMaKqqjVN1pcZYSrxDzn5leBF5bw7_YKaD_R6cFY8VtpVv5j_U8Woh" +
            	"tyIjM7_n2CsZ55vY8MUHCAYxzXK9_s75e6Ug8L4MEqpgeoJGQzYCxFrBFgGyDMv1jadLwNl4Y3yLhv4RLtQMU5AM6nODI601UfY" +
            	"drapObF3mpl_74H_YdRqT28LepGMtkEXbjeRgB-FiFGLvYlrK4wygczLBKrcviVyzyhrIrqz3TYV3g.Lf5lECzAdyAGgP8t.SHB" +
            	"UZoWkqwW_7u0GElrUqX1tewqRaUMWdGPHxpLRPmpVuc7FwQ27-kdsQ6O1_twhZ7uzjzZaEkatNhMxy9k10733-r4GT1lTGVqidK" +
            	"iBZq3mRQu7qJpcz7JWUroNFRLxhSoqpLpC8_tAhkohzG-mE42xdEh4tNDy3pBtAG0fe42WrLtWTuyg5lpmOYSppOc2Gb6LcDr4M" +
            	"mxFNPgoatF0edJSgO-CpFJQTcXn-22lU2g7o22x3RcBx9_KZH0At3g9y9uTuBncExOoBRK_ZweKOl0q76TaLiv5faXINW15xz9h" +
            	"ILA.RGYIL7FaQqAIMPAiQdkOig";

    	EncryptedJWT jwt = EncryptedJWT.parse(encryptedJWTString);

    	// Create a decrypter with the specified private RSA key.
    	RSADecrypter decrypter = new RSADecrypter(privateKey);

    	jwt.decrypt(decrypter);

    	// Printing decrypted id token header.
    	System.out.println("ID token header: " + jwt.getHeader().toJSONObject());

    	// Printing decrypted id token header.
    	System.out.println("ID token claims: " + jwt.getJWTClaimsSet().toJSONObject());
	}
}

When encrypted id tokens are produced, two encryption processes happen. First, a random content encryption key (CEK) is generated. Then the payload is encrypted using this CEK and a symmetric encryption algorithm, which is called the Encryption Method. Then the CEK is encrypted again using the public key of the client and an asymmetric encryption algorithm, which is called the Encryption Algorithm.

You can read more about these concepts from here.

You can configure the default values of above-mentioned Encryption Method and Encryption Algorithm by making changes in the <IS_HOME>/repository/conf/identity/identity.xml file.

<OpenIDConnect>
	...
	<!-- Default asymmetric encryption algorithm that used to encrypt CEK. -->
	<IDTokenEncryptionAlgorithm>RSA-OAEP</IDTokenEncryptionAlgorithm>
	<!-- Default symmetric encryption algorithm that used to encrypt JWT claims set. -->
	<IDTokenEncryptionMethod>A128GCM</IDTokenEncryptionMethod>
	...
</OpenIDConnect>

For Encryption Algorithm, currently, WSO2 IS supports following algorithms.

RSA1_5
RSA-OAEP

For Encryption Method, currently, WSO2 IS supports following algorithms.

A128GCM
A192GCM
A256GCM
A128CBC-HS256
A128CBC+HS256

<OpenIDConnect>
	...
	<!-- Supported versions: IS 5.5.0 onwards. -->
	<SupportedIDTokenEncryptionAlgorithms>
		<SupportedIDTokenEncryptionAlgorithm>RSA1_5</SupportedIDTokenEncryptionAlgorithm>
		<SupportedIDTokenEncryptionAlgorithm>RSA-OAEP</SupportedIDTokenEncryptionAlgorithm>
	</SupportedIDTokenEncryptionAlgorithms>
	<SupportedIDTokenEncryptionMethods>
		<SupportedIDTokenEncryptionMethod>A128GCM</SupportedIDTokenEncryptionMethod>
		<SupportedIDTokenEncryptionMethod>A192GCM</SupportedIDTokenEncryptionMethod>
		<SupportedIDTokenEncryptionMethod>A256GCM</SupportedIDTokenEncryptionMethod>
		<SupportedIDTokenEncryptionMethod>A128CBC-HS256</SupportedIDTokenEncryptionMethod>
		<SupportedIDTokenEncryptionMethod>A128CBC+HS256</SupportedIDTokenEncryptionMethod>
	</SupportedIDTokenEncryptionMethods>
	...
</OpenIDConnect>

By default WSO2 products ship with wso2carbon.jks. The password for the keystore is "wso2carbon" and the certificate alias is also "wso2carbon". In a production environment, we recommend that you change those values.