// Copyright (C) 2002 IAIK
// https://sic.tech/
//
// Copyright (C) 2003 - 2025 Stiftung Secure Information and 
//                           Communication Technologies SIC
// https://sic.tech/
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// $Header: /IAIK-CMS/current/src/demo/cms/envelopedData/EncryptedContentInfoDemo.java 26    12.02.25 17:58 Dbratko $
// $Revision: 26 $
//

package demo.cms.envelopedData;

import iaik.asn1.ASN;
import iaik.asn1.ASN1Object;
import iaik.asn1.INTEGER;
import iaik.asn1.OCTET_STRING;
import iaik.asn1.ObjectID;
import iaik.asn1.SEQUENCE;
import iaik.asn1.structures.AlgorithmID;
import iaik.cms.EncryptedContentInfoStream;
import iaik.cms.EnvelopedDataStream;
import iaik.cms.KeyTransRecipientInfo;
import iaik.cms.RecipientInfo;
import iaik.cms.SecurityProvider;
import iaik.security.random.SecRandom;
import iaik.utils.Util;
import iaik.x509.X509Certificate;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.security.PrivateKey;
import java.security.SecureRandom;
import java.security.spec.AlgorithmParameterSpec;

import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.RC2ParameterSpec;

import demo.keystore.CMSKeyStore;

/**
 * This class demonstrates the EnvelopedDataStream/EncryptedContentInfoStream usages
 * for algorithms that require a specific parameter handling.
 * <p>
 * All keys and certificates are read from a keystore created by the
 * SetupCMSKeyStore program.
 * <p>
 * The following algorithms are demonstrated:
 * <ul>
 * <li>ARCFOUR: Variable-key-size stream cipher; no parameters to be sent
 * <li>RC2_CBC: Variable-key-size block cipher; parameters as used by S/MIME:
 *              rc2ParamterVersion and IV; encoded as SEQUENCE:
 *              <pre>
 *               RC2-CBC parameter ::=  SEQUENCE {
 *                 rc2ParameterVersion  INTEGER,
 *                 iv                   OCTET STRING (8)}
 *
 *               For the effective-key-bits of 40, 64, and 128, the
 *                rc2ParameterVersion values are 160, 120, 58 respectively.
 *              </pre>
 * <li>CAST5_CBC: Feistel type block cipher with key sizes of 40-128 bit in 8 bit
 *              increments; parameters (RFC 2144):
 *              <pre>
 *               Parameters ::=  SEQUENCE {
 *                 iv         OCTET STRING DEFAULT 0,
 *                 keyLength  INTEGER }
 *
 *              </pre>
 * </ul>
 * This class shows how an EncryptedContentInfo is explicit created for encrypting
 * the content and supplying it to an EnvelopedDataStream object. Note that IAIK-CMS
 * also allows to use EnvelopedData(Stream) for algorithms like RC2, ARCFOUR or CAST 
 * without having the necessity of explicit key/parameter handling, see {@link 
 * RC2EnvelopedDataDemo RC2EnvelopedDataDemo} for an example. Note that the usage
 * of algorithms like RC2 is deprecated but used here for this demo since it
 * requires a specific parameter handling.
 */
public class EncryptedContentInfoDemo {

  // certificate of user 1
  X509Certificate user1;
  // private key of user 1
  PrivateKey user1_pk;
  // certificate of user 2
  X509Certificate user2;
  // private key of user 2
  PrivateKey user2_pk;
  // secure random number generator
  SecureRandom random;

  /**
   * Setup the demo certificate chains.
   *
   * Keys and certificate are retrieved from the demo KeyStore.
   *
   * @throws IOException if an file read error occurs
   */
  public EncryptedContentInfoDemo() throws IOException {
    
    System.out.println();
    System.out.println("********************************************************************************************");
    System.out.println("*                               EncryptedContentInfoDemo                                   *");
    System.out.println("* (shows the usage of the EncryptedContentInfo implementation for encrypting some message) *");
    System.out.println("********************************************************************************************");
    System.out.println();
    
    
    // add all certificates to the list
    X509Certificate[] certs = CMSKeyStore.getCertificateChain(CMSKeyStore.RSA, CMSKeyStore.SZ_2048_CRYPT_1);
    user1 = certs[0];
    user1_pk = CMSKeyStore.getPrivateKey(CMSKeyStore.RSA, CMSKeyStore.SZ_2048_CRYPT_1);
    user2 = CMSKeyStore.getCertificateChain(CMSKeyStore.RSA, CMSKeyStore.SZ_2048_CRYPT_2)[0];
    user2_pk = CMSKeyStore.getPrivateKey(CMSKeyStore.RSA, CMSKeyStore.SZ_2048_CRYPT_2);

    random = SecRandom.getDefault();
  }


  /**
   * Creates a CMS <code>EnvelopedDataStream</code> message.
   *
   * @param message the message to be enveloped, as byte representation
   * @param contentEA the content encryption algorithm
   * @param keyLength the key length for the symmetric key
   * @return the DER encoding of the <code>EnvelopedData</code> object just created
   * @throws Exception if the <code>EnvelopedData</code> object cannot be created
   */
  public byte[] createEnvelopedDataStream(byte[] message, AlgorithmID contentEA, int keyLength) throws Exception {

      SecurityProvider provider = SecurityProvider.getSecurityProvider();
      ByteArrayInputStream is = new ByteArrayInputStream(message);

      AlgorithmParameterSpec params = null;
      SecretKey secretKey = null;

      // create iv
      byte[] iv = new byte[8];
      random.nextBytes(iv);

      int rc2_param = 58;
      if (contentEA.equals(AlgorithmID.rc2_CBC)) {
         
         switch (keyLength) {
           case 40:
             rc2_param = 160;
             break;
           case 64:
             rc2_param = 120;
             break;
           default:    // 128
             rc2_param = 58;
             keyLength = 128;
         }
         // create the paramters (SEQUENCE) to be sent
         SEQUENCE parameter = new SEQUENCE();
         parameter.addComponent(new INTEGER(rc2_param));
         parameter.addComponent(new OCTET_STRING(iv));
         contentEA.setParameter(parameter);
         params = new RC2ParameterSpec(keyLength,iv);
      }  else if (contentEA.equals(AlgorithmID.arcfour)){
         // no params for ARCFOUR
         params = null;
      } else if (contentEA.equals(AlgorithmID.cast5_CBC)) {
         SEQUENCE parameter = new SEQUENCE();
         parameter.addComponent(new OCTET_STRING(iv));
         parameter.addComponent(new INTEGER(keyLength));
         contentEA.setParameter(parameter);
         params = new IvParameterSpec(iv);

      } else {
         throw new Exception("Algorithm " + contentEA + " not supportted for this test!");
      }

      KeyGenerator keyGen = provider.getKeyGenerator(contentEA, keyLength);
      // generate a new key
      secretKey = keyGen.generateKey();

      // create the EncryptedContentInfo for the content to be encrypted
      EncryptedContentInfoStream eci = new EncryptedContentInfoStream(ObjectID.pkcs7_data, is);
      // setup the cipher for encryption
      eci.setupCipher(contentEA, secretKey, params);

       // create the recipient infos
      RecipientInfo[] recipients = new RecipientInfo[2];
      // user1 is the first receiver
      recipients[0] = new KeyTransRecipientInfo(user1, (AlgorithmID)AlgorithmID.rsaEncryption.clone());
      // encrypt the secret key for recipient 1
      recipients[0].encryptKey(secretKey);
      // user2 is the second receiver
      recipients[1] = new KeyTransRecipientInfo(user2, (AlgorithmID)AlgorithmID.rsaEncryption.clone());
      // encrypt the secret key for recipient 2
      recipients[1].encryptKey(secretKey);
      // now create the EnvelopedDataStream
      EnvelopedDataStream enveloped_data = new EnvelopedDataStream(recipients, eci);

      // return the EnvelopedDate as DER encoded byte array with block size 2048
      ByteArrayOutputStream os = new ByteArrayOutputStream();
      enveloped_data.writeTo(os, 2048);
      byte[] enc = os.toByteArray();
      return enc;

  }

  /**
   * Decrypts the encrypted content of the given CMS <code>EnvelopedData</code> object for the
   * specified recipient and returns the decrypted (= original) message.
   *
   * @param encoding the <code>EnvelopedData</code> object as DER encoded byte array
   * @param privateKey the private key to decrypt the message
   * @param recipientInfoIndex the index into the <code>RecipientInfo</code> array
   *                           to which the specified private key belongs
   *
   * @return the recovered message, as byte array
   * @throws Exception if the message cannot be recovered
   */
  public byte[] getEnvelopedDataStream(byte[] encoding, PrivateKey privateKey, int recipientInfoIndex) throws Exception {

    // create the EnvelopedData object from a DER encoded byte array
    // we are testing the stream interface
    ByteArrayInputStream is = new ByteArrayInputStream(encoding);
    EnvelopedDataStream enveloped_data = new EnvelopedDataStream(is);

    AlgorithmParameterSpec params = null;
    // get the recipient infos
    RecipientInfo[]  recipients = enveloped_data.getRecipientInfos();

    System.out.println("\nThis message can be decrypted by the owners of the following certificates:");

    for (int i=0; i<recipients.length; i++) {
      System.out.println("Recipient "+(i+1)+":");
      System.out.println(recipients[i].getRecipientIdentifiers()[0]);
    }
    // decrypt symmetric content encryption key, e.g.:
    SecretKey secretKey = recipients[recipientInfoIndex].decryptKey(user1_pk);

    //get the ECI from the enveloped data:
    EncryptedContentInfoStream eci = (EncryptedContentInfoStream)enveloped_data.getEncryptedContentInfo();
    //get the content encryption algorithm:
    AlgorithmID contentEA = eci.getContentEncryptionAlgorithm();
    System.out.println("\nContent Encryption Algorithm: " + contentEA);
    if (contentEA.equals(AlgorithmID.rc2_CBC)) {
        // get the parameters as SEQUENCE
        SEQUENCE seq = (SEQUENCE)contentEA.getParameter();
        // the iv is the second component
        OCTET_STRING oct = (OCTET_STRING)seq.getComponentAt(1);
        // create an IvParameterSpec:
        //params = new IvParameterSpec((byte[])oct.getValue());
        int rc2ParameterVersion = ((BigInteger)seq.getComponentAt(0).getValue()).intValue();
        int effective_key_bits = 32;
        switch (rc2ParameterVersion) {
              case 160:
                effective_key_bits = 40;
                break;
              case 120:
                effective_key_bits = 64;
                break;
              case 58:
                effective_key_bits = 128;
                break;
              default:
                throw new Exception("Invalid rc2ParameterVersion " + rc2ParameterVersion + "!");

             }
             params = new RC2ParameterSpec(effective_key_bits,(byte[])seq.getComponentAt(1).getValue());

      }
      else if (contentEA.equals(AlgorithmID.rc5_CBC)) {
         OCTET_STRING oct = (OCTET_STRING)contentEA.getParameter();
         // create an IvParameterSpec:
         params = new IvParameterSpec((byte[])oct.getValue());
      } else if (contentEA.equals(AlgorithmID.arcfour)) {
         params = null;
      } else if (contentEA.equals(AlgorithmID.cast5_CBC)) {
          // get the parameters
          ASN1Object asn1Params = contentEA.getParameter();
          if (asn1Params.isA(ASN.SEQUENCE)) {
            // the iv is the first component
            params = new IvParameterSpec((byte[])asn1Params.getComponentAt(0).getValue());
          } else {
            // to be compatible with (invalid) CAST AlgorithmIDs only using the IV as parameters
            params = new IvParameterSpec((byte[])asn1Params.getValue());
          }  
      } else {
         throw new Exception("Algorithm " + contentEA + " not supportted for this test!");
      }


      //now setup the cipher with previously decrypted recipient key amd params
      eci.setupCipher(secretKey, params);
      //get and read the data thereby actually performing the decryption
      InputStream data_is = eci.getInputStream();
      ByteArrayOutputStream baos = new ByteArrayOutputStream();
      Util.copyStream(data_is, baos, null);
      byte[] decrypted = baos.toByteArray();
      return decrypted;

  }
  
  
  /**
   * Starts the test.
   */
  public void start() {
     // the test message
    String m = "This is the test message.";
    System.out.println("Test message: \""+m+"\"");
    System.out.println();
    byte[] message = m.getBytes();

    try {
      byte[] data;
      byte[] received_message = null;


      // the stream implementation
      //
      // test CMS EnvelopedDataStream
      //

      // ARCFOUR
      System.out.println("\nEnvelopedDataStream demo for algorithm ARCFOUR [create]:\n");
      data = createEnvelopedDataStream(message, (AlgorithmID)AlgorithmID.arcfour.clone(), 128);
      // transmit data
      System.out.println("\nEnvelopedDataStream demo [parse]:\n");
      // user1 means index 0 (hardcoded for this demo)
      received_message = getEnvelopedDataStream(data, user1_pk, 0);
      System.out.print("\nDecrypted content: ");
      System.out.println(new String(received_message));

      // RC2
      System.out.println("\nEnvelopedDataStream demo for algorithm RC2 [create]:\n");
      data = createEnvelopedDataStream(message, (AlgorithmID)AlgorithmID.rc2_CBC.clone(), 128);
      // transmit data
      System.out.println("\nEnvelopedDataStream demo [parse]:\n");
      // user1 means index 0 (hardcoded for this demo)
      received_message = getEnvelopedDataStream(data, user1_pk, 0);
      System.out.print("\nDecrypted content: ");
      System.out.println(new String(received_message));

      // CAST5_CBC
      System.out.println("\nEnvelopedDataStream demo for algorithm CAST5_CBC [create]:\n");
      data = createEnvelopedDataStream(message, (AlgorithmID)AlgorithmID.cast5_CBC.clone(), 128);
      // transmit data
      System.out.println("\nEnvelopedDataStream demo [parse]:\n");
      // user1 means index 0 (hardcoded for this demo)
      received_message = getEnvelopedDataStream(data, user1_pk, 0);
      System.out.print("\nDecrypted content: ");
      System.out.println(new String(received_message));
      
        } catch (Exception ex) {
          ex.printStackTrace();
          throw new RuntimeException(ex.toString());
        }
  }

  /**
   * The main method.
   *
   * @throws IOException
   *            if an I/O error occurs when reading required keys
   *            and certificates from files
   */
  public static void main(String argv[]) throws Exception {

        demo.DemoUtil.initDemos();

    (new EncryptedContentInfoDemo()).start();
    System.out.println("\nReady!");
    System.in.read();
  }
}