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using System;
using System.IO;
using Org.BouncyCastle.Tls.Crypto;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Utilities;
using Org.BouncyCastle.Utilities.IO;
namespace Org.BouncyCastle.Tls
{
/// <summary>(D)TLS SRP key exchange (RFC 5054).</summary>
public class TlsSrpKeyExchange
: AbstractTlsKeyExchange
{
private static int CheckKeyExchange(int keyExchange)
{
switch (keyExchange)
{
case KeyExchangeAlgorithm.SRP:
case KeyExchangeAlgorithm.SRP_DSS:
case KeyExchangeAlgorithm.SRP_RSA:
return keyExchange;
default:
throw new ArgumentException("unsupported key exchange algorithm", "keyExchange");
}
}
protected TlsSrpIdentity m_srpIdentity;
protected TlsSrpConfigVerifier m_srpConfigVerifier;
protected TlsCertificate m_serverCertificate = null;
protected byte[] m_srpSalt = null;
protected TlsSrp6Client m_srpClient = null;
protected TlsSrpLoginParameters m_srpLoginParameters;
protected TlsCredentialedSigner m_serverCredentials = null;
protected TlsSrp6Server m_srpServer = null;
protected BigInteger m_srpPeerCredentials = null;
public TlsSrpKeyExchange(int keyExchange, TlsSrpIdentity srpIdentity, TlsSrpConfigVerifier srpConfigVerifier)
: base(CheckKeyExchange(keyExchange))
{
this.m_srpIdentity = srpIdentity;
this.m_srpConfigVerifier = srpConfigVerifier;
}
public TlsSrpKeyExchange(int keyExchange, TlsSrpLoginParameters srpLoginParameters)
: base(CheckKeyExchange(keyExchange))
{
this.m_srpLoginParameters = srpLoginParameters;
}
public override void SkipServerCredentials()
{
if (m_keyExchange != KeyExchangeAlgorithm.SRP)
throw new TlsFatalAlert(AlertDescription.internal_error);
}
public override void ProcessServerCredentials(TlsCredentials serverCredentials)
{
if (m_keyExchange == KeyExchangeAlgorithm.SRP)
throw new TlsFatalAlert(AlertDescription.internal_error);
this.m_serverCredentials = TlsUtilities.RequireSignerCredentials(serverCredentials);
}
public override void ProcessServerCertificate(Certificate serverCertificate)
{
if (m_keyExchange == KeyExchangeAlgorithm.SRP)
throw new TlsFatalAlert(AlertDescription.internal_error);
this.m_serverCertificate = serverCertificate.GetCertificateAt(0);
}
public override bool RequiresServerKeyExchange
{
get { return true; }
}
public override byte[] GenerateServerKeyExchange()
{
TlsSrpConfig config = m_srpLoginParameters.Config;
this.m_srpServer = m_context.Crypto.CreateSrp6Server(config, m_srpLoginParameters.Verifier);
BigInteger B = m_srpServer.GenerateServerCredentials();
BigInteger[] ng = config.GetExplicitNG();
ServerSrpParams srpParams = new ServerSrpParams(ng[0], ng[1], m_srpLoginParameters.Salt, B);
DigestInputBuffer digestBuffer = new DigestInputBuffer();
srpParams.Encode(digestBuffer);
if (m_serverCredentials != null)
{
TlsUtilities.GenerateServerKeyExchangeSignature(m_context, m_serverCredentials, null, digestBuffer);
}
return digestBuffer.ToArray();
}
public override void ProcessServerKeyExchange(Stream input)
{
DigestInputBuffer digestBuffer = null;
Stream teeIn = input;
if (m_keyExchange != KeyExchangeAlgorithm.SRP)
{
digestBuffer = new DigestInputBuffer();
teeIn = new TeeInputStream(input, digestBuffer);
}
ServerSrpParams srpParams = ServerSrpParams.Parse(teeIn);
if (digestBuffer != null)
{
TlsUtilities.VerifyServerKeyExchangeSignature(m_context, input, m_serverCertificate, null,
digestBuffer);
}
TlsSrpConfig config = new TlsSrpConfig();
config.SetExplicitNG(new BigInteger[]{ srpParams.N, srpParams.G });
if (!m_srpConfigVerifier.Accept(config))
throw new TlsFatalAlert(AlertDescription.insufficient_security);
this.m_srpSalt = srpParams.S;
/*
* RFC 5054 2.5.3: The client MUST abort the handshake with an "illegal_parameter" alert if
* B % N = 0.
*/
this.m_srpPeerCredentials = ValidatePublicValue(srpParams.N, srpParams.B);
this.m_srpClient = m_context.Crypto.CreateSrp6Client(config);
}
public override void ProcessClientCredentials(TlsCredentials clientCredentials)
{
throw new TlsFatalAlert(AlertDescription.internal_error);
}
public override void GenerateClientKeyExchange(Stream output)
{
byte[] identity = m_srpIdentity.GetSrpIdentity();
byte[] password = m_srpIdentity.GetSrpPassword();
BigInteger A = m_srpClient.GenerateClientCredentials(m_srpSalt, identity, password);
TlsSrpUtilities.WriteSrpParameter(A, output);
m_context.SecurityParameters.m_srpIdentity = Arrays.Clone(identity);
}
public override void ProcessClientKeyExchange(Stream input)
{
/*
* RFC 5054 2.5.4: The server MUST abort the handshake with an "illegal_parameter" alert if
* A % N = 0.
*/
this.m_srpPeerCredentials = ValidatePublicValue(m_srpLoginParameters.Config.GetExplicitNG()[0],
TlsSrpUtilities.ReadSrpParameter(input));
m_context.SecurityParameters.m_srpIdentity = Arrays.Clone(m_srpLoginParameters.Identity);
}
public override TlsSecret GeneratePreMasterSecret()
{
BigInteger S = m_srpServer != null
? m_srpServer.CalculateSecret(m_srpPeerCredentials)
: m_srpClient.CalculateSecret(m_srpPeerCredentials);
// TODO Check if this needs to be a fixed size
return m_context.Crypto.CreateSecret(BigIntegers.AsUnsignedByteArray(S));
}
protected static BigInteger ValidatePublicValue(BigInteger N, BigInteger val)
{
val = val.Mod(N);
// Check that val % N != 0
if (val.Equals(BigInteger.Zero))
throw new TlsFatalAlert(AlertDescription.illegal_parameter);
return val;
}
}
}
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