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using System.Collections.Generic;
using System.IO;
using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.Cms;
using Org.BouncyCastle.Asn1.Cms.Ecc;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Asn1.X9;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.X509;
namespace Org.BouncyCastle.Cms
{
internal class KeyAgreeRecipientInfoGenerator
: RecipientInfoGenerator
{
private static readonly CmsEnvelopedHelper Helper = CmsEnvelopedHelper.Instance;
private readonly List<KeyAgreeRecipientIdentifier> m_recipientIDs = new List<KeyAgreeRecipientIdentifier>();
private readonly List<AsymmetricKeyParameter> m_recipientKeys = new List<AsymmetricKeyParameter>();
private DerObjectIdentifier m_keyAgreementOid;
private DerObjectIdentifier m_keyEncryptionOid;
private AsymmetricCipherKeyPair m_senderKeyPair;
internal KeyAgreeRecipientInfoGenerator(IEnumerable<X509Certificate> recipientCerts)
{
foreach (var recipientCert in recipientCerts)
{
m_recipientIDs.Add(new KeyAgreeRecipientIdentifier(CmsUtilities.GetIssuerAndSerialNumber(recipientCert)));
m_recipientKeys.Add(recipientCert.GetPublicKey());
}
}
internal KeyAgreeRecipientInfoGenerator(byte[] subjectKeyID, AsymmetricKeyParameter publicKey)
{
m_recipientIDs.Add(new KeyAgreeRecipientIdentifier(new RecipientKeyIdentifier(subjectKeyID)));
m_recipientKeys.Add(publicKey);
}
internal DerObjectIdentifier KeyAgreementOid
{
set { m_keyAgreementOid = value; }
}
internal DerObjectIdentifier KeyEncryptionOid
{
set { m_keyEncryptionOid = value; }
}
internal AsymmetricCipherKeyPair SenderKeyPair
{
set { m_senderKeyPair = value; }
}
public RecipientInfo Generate(KeyParameter contentEncryptionKey, SecureRandom random)
{
byte[] keyBytes = contentEncryptionKey.GetKey();
AsymmetricKeyParameter senderPublicKey = m_senderKeyPair.Public;
ICipherParameters senderPrivateParams = m_senderKeyPair.Private;
OriginatorIdentifierOrKey originator;
try
{
originator = new OriginatorIdentifierOrKey(
CreateOriginatorPublicKey(senderPublicKey));
}
catch (IOException e)
{
throw new InvalidKeyException("cannot extract originator public key: " + e);
}
Asn1OctetString ukm = null;
if (CmsUtilities.IsMqv(m_keyAgreementOid))
{
try
{
IAsymmetricCipherKeyPairGenerator ephemKPG =
GeneratorUtilities.GetKeyPairGenerator(m_keyAgreementOid);
ephemKPG.Init(
((ECPublicKeyParameters)senderPublicKey).CreateKeyGenerationParameters(random));
AsymmetricCipherKeyPair ephemKP = ephemKPG.GenerateKeyPair();
ukm = new DerOctetString(
new MQVuserKeyingMaterial(
CreateOriginatorPublicKey(ephemKP.Public), null));
senderPrivateParams = new MqvPrivateParameters(
(ECPrivateKeyParameters)senderPrivateParams,
(ECPrivateKeyParameters)ephemKP.Private,
(ECPublicKeyParameters)ephemKP.Public);
}
catch (IOException e)
{
throw new InvalidKeyException("cannot extract MQV ephemeral public key: " + e);
}
catch (SecurityUtilityException e)
{
throw new InvalidKeyException("cannot determine MQV ephemeral key pair parameters from public key: " + e);
}
}
DerSequence paramSeq = new DerSequence(m_keyEncryptionOid, DerNull.Instance);
AlgorithmIdentifier keyEncAlg = new AlgorithmIdentifier(m_keyAgreementOid, paramSeq);
Asn1EncodableVector recipientEncryptedKeys = new Asn1EncodableVector(m_recipientIDs.Count);
for (int i = 0; i < m_recipientIDs.Count; ++i)
{
var recipientID = m_recipientIDs[i];
ICipherParameters recipientPublicParams = m_recipientKeys[i];
if (m_keyAgreementOid.Id.Equals(CmsEnvelopedGenerator.ECMqvSha1Kdf))
{
recipientPublicParams = new MqvPublicParameters(
(ECPublicKeyParameters)recipientPublicParams,
(ECPublicKeyParameters)recipientPublicParams);
}
// Use key agreement to choose a wrap key for this recipient
IBasicAgreement keyAgreement = AgreementUtilities.GetBasicAgreementWithKdf(
m_keyAgreementOid, m_keyEncryptionOid);
keyAgreement.Init(new ParametersWithRandom(senderPrivateParams, random));
BigInteger agreedValue = keyAgreement.CalculateAgreement(recipientPublicParams);
int keyEncryptionKeySize = GeneratorUtilities.GetDefaultKeySize(m_keyEncryptionOid) / 8;
byte[] keyEncryptionKeyBytes = X9IntegerConverter.IntegerToBytes(agreedValue, keyEncryptionKeySize);
KeyParameter keyEncryptionKey = ParameterUtilities.CreateKeyParameter(
m_keyEncryptionOid, keyEncryptionKeyBytes);
// Wrap the content encryption key with the agreement key
IWrapper keyWrapper = WrapperUtilities.GetWrapper(m_keyEncryptionOid.Id);
keyWrapper.Init(true, new ParametersWithRandom(keyEncryptionKey, random));
byte[] encryptedKeyBytes = keyWrapper.Wrap(keyBytes, 0, keyBytes.Length);
Asn1OctetString encryptedKey = new DerOctetString(encryptedKeyBytes);
recipientEncryptedKeys.Add(new RecipientEncryptedKey(recipientID, encryptedKey));
}
return new RecipientInfo(new KeyAgreeRecipientInfo(originator, ukm, keyEncAlg,
new DerSequence(recipientEncryptedKeys)));
}
private static OriginatorPublicKey CreateOriginatorPublicKey(AsymmetricKeyParameter publicKey) =>
CreateOriginatorPublicKey(SubjectPublicKeyInfoFactory.CreateSubjectPublicKeyInfo(publicKey));
private static OriginatorPublicKey CreateOriginatorPublicKey(SubjectPublicKeyInfo originatorKeyInfo) =>
new OriginatorPublicKey(originatorKeyInfo.Algorithm, originatorKeyInfo.PublicKey);
}
}
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