KeyTransRecipientInfoGenerator.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;
using Org.BouncyCastle.X509;

namespace Org.BouncyCastle.Cms{
  internal class KeyTransRecipientInfoGenerator : RecipientInfoGenerator
  {
    private static readonly CmsEnvelopedHelper Helper = CmsEnvelopedHelper.Instance;

    private TbsCertificateStructure  recipientTbsCert;
    private AsymmetricKeyParameter  recipientPublicKey;
    private Asn1OctetString      subjectKeyIdentifier;

    // Derived fields
    private SubjectPublicKeyInfo info;
    
    internal KeyTransRecipientInfoGenerator()
    {
    }
    
    internal X509Certificate RecipientCert
    {
      set
      {
        try
        {
          this.recipientTbsCert = TbsCertificateStructure.GetInstance(
            Asn1Object.FromByteArray(value.GetTbsCertificate()));
        }
        catch (Exception)
        {
          throw new ArgumentException("can't extract TBS structure from this cert");
        }
        
        this.recipientPublicKey = value.GetPublicKey();
        this.info = recipientTbsCert.SubjectPublicKeyInfo;
      }
    }
    
    internal AsymmetricKeyParameter RecipientPublicKey
    {
      set
      {
        this.recipientPublicKey = value;

        try
        {
          info = SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(
            recipientPublicKey);
        }
        catch (IOException)
        {
          throw new ArgumentException("can't extract key algorithm from this key");
        }
      }
    }
    
    internal Asn1OctetString SubjectKeyIdentifier
    {
      set { this.subjectKeyIdentifier = value; }
    }

    public RecipientInfo Generate(KeyParameter contentEncryptionKey, SecureRandom random)
    {
      byte[] keyBytes = contentEncryptionKey.GetKey();
      AlgorithmIdentifier keyEncAlg = info.AlgorithmID;

      IWrapper keyWrapper = Helper.CreateWrapper(keyEncAlg.ObjectID.Id);
      keyWrapper.Init(true, new ParametersWithRandom(recipientPublicKey, random));
      byte[] encKeyBytes = keyWrapper.Wrap(keyBytes, 0, keyBytes.Length);

      RecipientIdentifier recipId;
      if (recipientTbsCert != null)
      {
        IssuerAndSerialNumber issuerAndSerial = new IssuerAndSerialNumber(
          recipientTbsCert.Issuer, recipientTbsCert.SerialNumber.Value);
        recipId = new RecipientIdentifier(issuerAndSerial);
      }
      else
      {
        recipId = new RecipientIdentifier(subjectKeyIdentifier);
      }

      return new RecipientInfo(new KeyTransRecipientInfo(recipId, keyEncAlg,
        new DerOctetString(encKeyBytes)));
    }
  }
}