Thursday, September 12, 2019

How to view an LtpaToken2 token

If you use any WebSphere-based applications (DASH, Impact, BPM, ODM, etc.), you're using LTPA Tokens. An LTPA Token is a browser cookie named LtpaToken2. You can see it if you turn on developer tools in your browser (F12) after you log into one of these applications. You'll see it in the "COOKIES" request header. The value of that header will look something like this:

s_vi=[CS]v1|2E7C0CDA8507BB19-4000010FA0013DFE[CE]; s_cc=true; s_sq=%5B%5BB%5D%5D; JSESSIONID=00004FX-3-uu2ZoYHx1t9p8fJIb:52e767f1-e67e-4220-8435-fa54d8776107; CSRFCookie=C9495874E4D5BA23D8E1330E4F76EA5C9495874E4D5BA23D8E1330E4F76EA5; LtpaToken2=i/InlYuq2tm3rPdd/3BEzA8m9BCc8WGNR3q6eu7OfeQ7s1ICiMvPv0QCNQar5cCQlyVH5GE0N0VNbJj1Z6sUGe2S3nb1kwwbzdzPWzCbNPPtN3uiPWnfLyXzi5T4p2Pz/URwCfP6zWW2NOob/yQoG5vYg/JAgJag9CWP5tqd9+6FgInahSj3VaYYvu69O4hY+h6e6D+v7mpLTYBRM33TlVugTxOkx64JTMAdwFAfH553Ob2T+sW4aqyiGc7arLodIMlWjiVbkBBEgYZ0PXMyCPKb7JPa+5lFxfMRBK0P1kMsC34OXnQ1jUaedx44U4I5

Notice that each cookie=value pair is separated by a semicolon (;). The LtpaToken2 cookie and value are in bold above. That cookie contains the "principal" (user) name, the "realm" (a named security policy domain), and the expiration date of the token. This token is used by a WebSphere server (whether it's WebSphere ND, WebSphere Liberty, or any other flavor of WebSphere) to make authorization decisions to determine which resources the user has access to. It's also used for authentication across WebSphere servers if the two servers share the same LTPA keys. This sharing of keys is how one server "trusts" an LTPA token created by another server.

For troubleshooting purposes, sometimes you want/need to see what's inside an LTPA token. I found the best article on the web that provides the code to allow you to do exactly that. The page is found here: http://tech.srij.it/2012/04/how-to-decrypt-ltpa-cookie-and-view.html , but it leaves out some basic steps that I'm including here. I'm also copying the Java code at the bottom of this blog post just in case the linked article disappears.

Once you've copied the code into a file named DecryptLTPA.java (the file MUST have this name to match the name of the class defined in the file), you then need to specify several values in the file. Specifically, you need to provide values for the following variables:


ltpaKey : the com.ibm.websphere.ltpa.3DESKey value from ltpa.keys file. This file already exists if you're using WebSphere Liberty. If you're using "full" WebSphere, you need to create this file (with whatever name you want) by exporting the LTPA keys from the WebSphere Administration Console. In the ltpa.keys file, this value will end with the characters "\=" (backslash equals). When you paste the value into the DecryptLTPA.java, remove that backslash.

ltpaPassword : WebAS  - This is the default password on WebSphere Liberty. If you're using "full" WebSphere, the password will be whatever you specify when you export the LTPA keys using the WebSphere Administration Console.

tokenCipher : the entire value of the ltpatoken2 header from the COOKIES header in the Request.


Once you've done the above, the beginning of the definition of the main() function in the DecryptLTPA.java file should look something like:

 public static void main(String[] args) {
  String ltpaKey = "ADbpPpqPf3bnkj0b34sNaNC2FYHYygub3/cGjIn+mR4=";
  String ltpaPassword = "WebAS";
  String tokenCipher = "i/InlYuq2tm3rPdd/3BEzA8m9BCc8WGNR3q6eu7OfeQ7s1ICiMvPv0QCNQar5cCQlyVH5GE0N0VNbJj1Z6sUGe2S3nb1kwwbzdzPWzCbNPPtN3uiPWnfLyXzi5T4p2Pz/URwCfP6zWW2NOob/yQoG5vYg/JAgJag9CWP5tqd9+6FgInahSj3VaYYvu69O4hY+h6e6D+v7mpLTYBRM33TlVugTxOkx64JTMAdwFAfH553Ob2T+sW4aqyiGc7arLodIMlWjiVbkBBEgYZ0PXMyCPKb7JPa+5lFxfMRBK0P1kMsC34OXnQ1jUaedx44U4I5";

You then need to compile the java file with a command similar to the following:

 javac -cp /opt/IBM/tivoli/impact/wlp/usr/servers/ImpactUI/apps/blaze.war/WEB-INF/lib/commons-codec-1.10.jar DecryptLTPA.java

That command points to the commons-codec.1.10.jar file, which contains the definition of the Base64 class referenced by the code. That command was run on a Netcool Impact version 7.1.0.16 server which uses WebSphere Liberty. If you were to compile the code on a DASH version 3.1.3.0 server, the command would look like this:

javac -cp /opt/IBM/tivoli/JazzSM/profile/installedApps/JazzSMNode01Cell/IBM Cognos.ear/p2pd.war/WEB-INF/lib/commons-codec-1.3.jar DecryptLTPA.java

In both cases, my path includes the Java 1.7 SDK binaries and my JAVA_HOME is set to the Java 1.7 SDK directory.

Once you have the file compiled, you can actually run it, which requires a similar command:

 java -cp /opt/IBM/tivoli/impact/wlp/usr/servers/ImpactUI/apps/blaze.war/WEB-INF/lib/commons-codec-1.10.jar:. DecryptLTPA

Notice that you must include "." (present working directory) in the classpath (-cp flag) in addition to the commons-codec jar file.

Once that runs, you should see output similar to:

Algorithm:[AES]
Full token string:[expire:1568250479184$u:user\:customRealm/impactadmin%1568250479184%zoQ7cb1BSWekvxdd3slUpxmCRlBCBmMO1nu8iztv73PKQN3MIybuCx/C9EdKGwoeoguJHKrj0BOOAeXxVLDgIQL5Jz2Tg6LQcIyTpAtRAVMsqWTPFzDBrs85Zxs9kP0zFEiOvEsDUmRXXm92dN6zxWooEyGz453x1VPmqGoZ0ww=]
Token is for:[expire:1568250479184$u:user\:customRealm/impactadmin]
Token expires at:[2019-09-11-21:07:59 EDT]
Token signature:[zoQ7cb1BSWekvxdd3slUpxmCRlBCBmMO1nu8iztv73PKQN3MIybuCx/C9EdKGwoeoguJHKrj0BOOAeXxVLDgIQL5Jz2Tg6LQcIyTpAtRAVMsqWTPFzDBrs85Zxs9kP0zFEiOvEsDUmRXXm92dN6zxWooEyGz453x1VPmqGoZ0ww=]

As you can see, the user (principal) ID and expiration timestamps are easily visible, which was my goal from the beginning.

Full Java code:

import java.security.MessageDigest;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.StringTokenizer;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESedeKeySpec;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;

public class DecryptLTPA {
 private static final String AES = "AES/CBC/PKCS5Padding";
 private static final String DES = "DESede/ECB/PKCS5Padding";

 public static void main(String[] args) {
  String ltpaKey = "<DES key from ltpa token>";
  String ltpaPassword = "<password used to export ltpa token>";
  String tokenCipher = "<the header text to dercypt>";

  try {
   Base64 b = new Base64();
   byte[] secretKey = null;
   MessageDigest md = MessageDigest.getInstance("SHA");
   md.update(ltpaPassword.getBytes());
   byte[] hash3DES = new byte[24];
   System.arraycopy(md.digest(), 0, hash3DES, 0, 20);
   Arrays.fill(hash3DES, 20, 24, (byte) 0);
   secretKey = decrypt(b.decode(ltpaKey), hash3DES, DES);
   byte[] ltpaByteArray = b.decode(tokenCipher);

   String algorithm, userInfo, expires, signature, ltpaPlaintext;
   try {
    algorithm="DES";
    ltpaPlaintext = new String(decrypt(ltpaByteArray, secretKey, DES));
   } catch (Exception e) {
    algorithm="AES";
    ltpaPlaintext = new String(decrypt(ltpaByteArray, secretKey, AES));
   }

   System.err.println("Algorithm:["+algorithm+"]");
   StringTokenizer st = new StringTokenizer(ltpaPlaintext, "%");
   userInfo = st.nextToken();
   expires = st.nextToken();
   signature = st.nextToken();
   System.err.println("Full token string:[" + ltpaPlaintext + "]");
   Date d = new Date(Long.parseLong(expires));
   SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd-HH:mm:ss z");
   System.err.println("Token is for:[" + userInfo + "]");
   System.err.println("Token expires at:[" + sdf.format(d) + "]");
   System.err.println("Token signature:[" + signature + "]");

  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public static byte[] decrypt(byte[] ciphertext, byte[] key, String algorithm) throws Exception {
  SecretKey sKey = null;

  if (algorithm.indexOf("AES") != -1) {
   sKey = new SecretKeySpec(key, 0, 16, "AES");
  } else {
   DESedeKeySpec kSpec = new DESedeKeySpec(key);
   SecretKeyFactory kFact = SecretKeyFactory.getInstance("DESede");
   sKey = kFact.generateSecret(kSpec);
  }
  Cipher cipher = Cipher.getInstance(algorithm);

  if (algorithm.indexOf("ECB") == -1) {
   if (algorithm.indexOf("AES") != -1) {
    IvParameterSpec ivs16 = generateIvParameterSpec(key, 16);
    cipher.init(Cipher.DECRYPT_MODE, sKey, ivs16);
   } else {
    IvParameterSpec ivs8 = generateIvParameterSpec(key, 8);
    cipher.init(Cipher.DECRYPT_MODE, sKey, ivs8);
   }
  } else {
   cipher.init(Cipher.DECRYPT_MODE, sKey);
  }
  return cipher.doFinal(ciphertext);
 }

 private static IvParameterSpec generateIvParameterSpec(byte key[], int size) {
  byte[] row = new byte[size];

  for (int i = 0; i < size; i++) {
   row[i] = key[i];
  }

  return new IvParameterSpec(row);
 }
}

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