PasswordRecipientInformation.cs :  » PDF » iTextSharp » Org » BouncyCastle » Cms » C# / CSharp Open Source

using System;
using System.IO;

using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.Cms;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Security;

namespace Org.BouncyCastle.Cms{
  /**
   * the RecipientInfo class for a recipient who has been sent a message
   * encrypted using a password.
   */
  public class PasswordRecipientInformation
    : RecipientInformation
  {
    private readonly PasswordRecipientInfo  info;

    [Obsolete]
    public PasswordRecipientInformation(
      PasswordRecipientInfo  info,
      AlgorithmIdentifier    encAlg,
      Stream          data)
      : this(info, encAlg, null, null, data)
    {
    }

    [Obsolete]
    public PasswordRecipientInformation(
      PasswordRecipientInfo  info,
      AlgorithmIdentifier    encAlg,
      AlgorithmIdentifier    macAlg,
      Stream          data)
      : this(info, encAlg, macAlg, null, data)
    {
    }

    public PasswordRecipientInformation(
      PasswordRecipientInfo  info,
      AlgorithmIdentifier    encAlg,
      AlgorithmIdentifier    macAlg,
      AlgorithmIdentifier    authEncAlg,
      Stream          data)
      : base(encAlg, macAlg, authEncAlg, info.KeyEncryptionAlgorithm, data)
    {
      this.info = info;
      this.rid = new RecipientID();
    }

    /**
     * return the object identifier for the key derivation algorithm, or null
     * if there is none present.
     *
     * @return OID for key derivation algorithm, if present.
     */
    public virtual AlgorithmIdentifier KeyDerivationAlgorithm
    {
      get { return info.KeyDerivationAlgorithm; }
    }

    /**
     * decrypt the content and return an input stream.
     */
    public override CmsTypedStream GetContentStream(
      ICipherParameters key)
    {
      try
      {
        AlgorithmIdentifier kekAlg = AlgorithmIdentifier.GetInstance(info.KeyEncryptionAlgorithm);
        Asn1Sequence        kekAlgParams = (Asn1Sequence)kekAlg.Parameters;
        byte[]              encryptedKey = info.EncryptedKey.GetOctets();
        string              kekAlgName = DerObjectIdentifier.GetInstance(kekAlgParams[0]).Id;
        string        cName = CmsEnvelopedHelper.Instance.GetRfc3211WrapperName(kekAlgName);
        IWrapper      keyWrapper = WrapperUtilities.GetWrapper(cName);

        byte[] iv = Asn1OctetString.GetInstance(kekAlgParams[1]).GetOctets();

        ICipherParameters parameters = ((CmsPbeKey)key).GetEncoded(kekAlgName);
        parameters = new ParametersWithIV(parameters, iv);

        keyWrapper.Init(false, parameters);

        AlgorithmIdentifier aid = GetActiveAlgID();

        string alg = aid.ObjectID.Id;

        KeyParameter sKey = ParameterUtilities.CreateKeyParameter(
          alg, keyWrapper.Unwrap(encryptedKey, 0, encryptedKey.Length));

        return GetContentFromSessionKey(sKey);
      }
      catch (SecurityUtilityException e)
      {
        throw new CmsException("couldn't create cipher.", e);
      }
      catch (InvalidKeyException e)
      {
        throw new CmsException("key invalid in message.", e);
      }
    }
  }
}