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

using System;
using System.Collections;
using System.IO;

using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.Cms;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Utilities;

namespace Org.BouncyCastle.Cms{
  /**
  * Parsing class for an CMS Authenticated Data object from an input stream.
  * <p>
  * Note: that because we are in a streaming mode only one recipient can be tried and it is important
  * that the methods on the parser are called in the appropriate order.
  * </p>
  * <p>
  * Example of use - assuming the first recipient matches the private key we have.
  * <pre>
  *      CMSAuthenticatedDataParser     ad = new CMSAuthenticatedDataParser(inputStream);
  *
  *      RecipientInformationStore  recipients = ad.getRecipientInfos();
  *
  *      Collection  c = recipients.getRecipients();
  *      Iterator    it = c.iterator();
  *
  *      if (it.hasNext())
  *      {
  *          RecipientInformation   recipient = (RecipientInformation)it.next();
  *
  *          CMSTypedStream recData = recipient.getContentStream(privateKey, "BC");
  *
  *          processDataStream(recData.getContentStream());
  *
  *          if (!Arrays.equals(ad.getMac(), recipient.getMac())
  *          {
  *              System.err.println("Data corrupted!!!!");
  *          }
  *      }
  *  </pre>
  *  Note: this class does not introduce buffering - if you are processing large files you should create
  *  the parser with:
  *  <pre>
  *          CMSAuthenticatedDataParser     ep = new CMSAuthenticatedDataParser(new BufferedInputStream(inputStream, bufSize));
  *  </pre>
  *  where bufSize is a suitably large buffer size.
  * </p>
  */
  public class CmsAuthenticatedDataParser
    : CmsContentInfoParser
  {
    internal RecipientInformationStore  _recipientInfoStore;
    internal AuthenticatedDataParser  authData;

    private AlgorithmIdentifier      macAlg;
    private byte[]            mac;
    private Asn1.Cms.AttributeTable    authAttrs;
    private Asn1.Cms.AttributeTable    unauthAttrs;

    private bool authAttrNotRead;
    private bool unauthAttrNotRead;

    public CmsAuthenticatedDataParser(
      byte[] envelopedData)
      : this(new MemoryStream(envelopedData, false))
    {
    }

    public CmsAuthenticatedDataParser(
      Stream envelopedData)
      : base(envelopedData)
    {
      this.authAttrNotRead = true;
      this.authData = new AuthenticatedDataParser(
        (Asn1SequenceParser)contentInfo.GetContent(Asn1Tags.Sequence));

      // TODO Validate version?
      //DerInteger version = this.authData.getVersion();

      //
      // load the RecipientInfoStore
      //
      Asn1SetParser s = authData.GetRecipientInfos();
      IList baseInfos = new ArrayList();

      IAsn1Convertible entry;
      while ((entry = s.ReadObject()) != null)
      {
        baseInfos.Add(RecipientInfo.GetInstance(entry.ToAsn1Object()));
      }

      this.macAlg = authData.GetMacAlgorithm();

      //
      // read the encrypted content info
      //
      ContentInfoParser data = authData.GetEnapsulatedContentInfo();

      //
      // prime the recipients
      //
      Stream contentStream = ((Asn1OctetStringParser)data.GetContent(Asn1Tags.OctetString)).GetOctetStream();
      IList infos = CmsEnvelopedHelper.ReadRecipientInfos(
        baseInfos, contentStream, null, macAlg, null);

      _recipientInfoStore = new RecipientInformationStore(infos);
    }

    public AlgorithmIdentifier MacAlgorithmID
    {
      get { return macAlg; }
    }

    /**
    * return the object identifier for the mac algorithm.
    */
    public string MacAlgOid
    {
      get { return macAlg.ObjectID.Id; }
    }


    /**
     * return the ASN.1 encoded encryption algorithm parameters, or null if
     * there aren't any.
     */
    public Asn1Object MacAlgParams
    {
      get
      {
        Asn1Encodable ae = macAlg.Parameters;

        return ae == null ? null : ae.ToAsn1Object();
      }
    }

    /**
    * return a store of the intended recipients for this message
    */
    public RecipientInformationStore GetRecipientInfos()
    {
      return _recipientInfoStore;
    }

    public byte[] GetMac()
    {
      if (mac == null)
      {
        GetAuthAttrs();
        mac = authData.GetMac().GetOctets();
      }
      return Arrays.Clone(mac);
    }

    /**
    * return a table of the unauthenticated attributes indexed by
    * the OID of the attribute.
    * @exception java.io.IOException
    */
    public Asn1.Cms.AttributeTable GetAuthAttrs()
    {
      if (authAttrs == null && authAttrNotRead)
      {
        Asn1SetParser s = authData.GetAuthAttrs();

        authAttrNotRead = false;

        if (s != null)
        {
          Asn1EncodableVector v = new Asn1EncodableVector();

          IAsn1Convertible o;
          while ((o = s.ReadObject()) != null)
          {
            Asn1SequenceParser seq = (Asn1SequenceParser)o;

            v.Add(seq.ToAsn1Object());
          }

          authAttrs = new Asn1.Cms.AttributeTable(new DerSet(v));
        }
      }

      return authAttrs;
    }

    /**
    * return a table of the unauthenticated attributes indexed by
    * the OID of the attribute.
    * @exception java.io.IOException
    */
    public Asn1.Cms.AttributeTable GetUnauthAttrs()
    {
      if (unauthAttrs == null && unauthAttrNotRead)
      {
        Asn1SetParser s = authData.GetUnauthAttrs();

        unauthAttrNotRead = false;

        if (s != null)
        {
          Asn1EncodableVector v = new Asn1EncodableVector();

          IAsn1Convertible o;
          while ((o = s.ReadObject()) != null)
          {
            Asn1SequenceParser seq = (Asn1SequenceParser)o;

            v.Add(seq.ToAsn1Object());
          }

          unauthAttrs = new Asn1.Cms.AttributeTable(new DerSet(v));
        }
      }

      return unauthAttrs;
    }
  }
}