123 lines
3.5 KiB
C#
123 lines
3.5 KiB
C#
using System;
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using System.IO;
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using Org.BouncyCastle.Asn1;
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using Org.BouncyCastle.Asn1.Cms;
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using Org.BouncyCastle.Asn1.Pkcs;
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using Org.BouncyCastle.Asn1.X509;
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using Org.BouncyCastle.Crypto;
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using Org.BouncyCastle.Crypto.Parameters;
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using Org.BouncyCastle.Math;
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using Org.BouncyCastle.Pkcs;
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using Org.BouncyCastle.Security;
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using Org.BouncyCastle.X509;
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namespace Org.BouncyCastle.Cms
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{
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/**
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* the RecipientInfo class for a recipient who has been sent a message
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* encrypted using key agreement.
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*/
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public class KeyAgreeRecipientInformation
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: RecipientInformation
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{
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private KeyAgreeRecipientInfo _info;
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// private AlgorithmIdentifier _encAlg;
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private Asn1OctetString _encryptedKey;
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public KeyAgreeRecipientInformation(
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KeyAgreeRecipientInfo info,
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AlgorithmIdentifier encAlg,
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Stream data)
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: base(encAlg, AlgorithmIdentifier.GetInstance(info.KeyEncryptionAlgorithm), data)
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{
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_info = info;
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// _encAlg = encAlg;
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try
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{
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Asn1Sequence s = _info.RecipientEncryptedKeys;
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RecipientEncryptedKey id = RecipientEncryptedKey.GetInstance(s[0]);
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Asn1.Cms.IssuerAndSerialNumber iAnds = id.Identifier.IssuerAndSerialNumber;
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// byte[] issuerBytes = iAnds.Name.GetEncoded();
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_rid = new RecipientID();
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// _rid.SetIssuer(issuerBytes);
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_rid.Issuer = iAnds.Name;
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_rid.SerialNumber = iAnds.SerialNumber.Value;
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_encryptedKey = id.EncryptedKey;
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}
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catch (IOException e)
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{
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throw new ArgumentException("invalid rid in KeyAgreeRecipientInformation", e);
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}
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}
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/**
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* decrypt the content and return an input stream.
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*/
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public override CmsTypedStream GetContentStream(
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// Key key)
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ICipherParameters key)
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{
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if (!(key is AsymmetricKeyParameter))
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throw new ArgumentException("KeyAgreement requires asymmetric key", "key");
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AsymmetricKeyParameter privKey = (AsymmetricKeyParameter) key;
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if (!privKey.IsPrivate)
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throw new ArgumentException("Expected private key", "key");
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try
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{
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OriginatorPublicKey origK = _info.Originator.OriginatorKey;
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PrivateKeyInfo privInfo = PrivateKeyInfoFactory.CreatePrivateKeyInfo(privKey);
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SubjectPublicKeyInfo pubInfo = new SubjectPublicKeyInfo(privInfo.AlgorithmID, origK.PublicKey.GetBytes());
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AsymmetricKeyParameter pubKey = PublicKeyFactory.CreateKey(pubInfo);
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string wrapAlg = DerObjectIdentifier.GetInstance(
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Asn1Sequence.GetInstance(_keyEncAlg.Parameters)[0]).Id;
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IBasicAgreement agreement = AgreementUtilities.GetBasicAgreementWithKdf(
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_keyEncAlg.ObjectID, wrapAlg);
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agreement.Init(privKey);
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BigInteger wKeyNum = agreement.CalculateAgreement(pubKey);
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// TODO Fix the way bytes are derived from the secret
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byte[] wKeyBytes = wKeyNum.ToByteArrayUnsigned();
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KeyParameter wKey = ParameterUtilities.CreateKeyParameter(wrapAlg, wKeyBytes);
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IWrapper keyCipher = WrapperUtilities.GetWrapper(wrapAlg);
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keyCipher.Init(false, wKey);
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AlgorithmIdentifier aid = _encAlg;
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string alg = aid.ObjectID.Id;
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byte[] encryptedKey = _encryptedKey.GetOctets();
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byte[] sKeyBytes = keyCipher.Unwrap(encryptedKey, 0, encryptedKey.Length);
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KeyParameter sKey = ParameterUtilities.CreateKeyParameter(alg, sKeyBytes);
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return GetContentFromSessionKey(sKey);
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}
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catch (SecurityUtilityException e)
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{
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throw new CmsException("couldn't create cipher.", e);
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}
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catch (InvalidKeyException e)
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{
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throw new CmsException("key invalid in message.", e);
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}
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catch (Exception e)
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{
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throw new CmsException("originator key invalid.", e);
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}
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}
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}
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}
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