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using System;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Security;
namespace Org.BouncyCastle.Crypto.Signers
{
public class DsaDigestSigner
: ISigner
{
private readonly IDsa dsa;
private readonly IDigest digest;
private readonly IDsaEncoding encoding;
private bool forSigning;
public DsaDigestSigner(IDsa dsa, IDigest digest)
: this(dsa, digest, StandardDsaEncoding.Instance)
{
}
public DsaDigestSigner(IDsa dsa, IDigest digest, IDsaEncoding encoding)
{
this.dsa = dsa;
this.digest = digest;
this.encoding = encoding;
}
public virtual string AlgorithmName
{
get { return digest.AlgorithmName + "with" + dsa.AlgorithmName; }
}
public virtual void Init(bool forSigning, ICipherParameters parameters)
{
this.forSigning = forSigning;
AsymmetricKeyParameter k;
if (parameters is ParametersWithRandom withRandom)
{
k = (AsymmetricKeyParameter)withRandom.Parameters;
}
else
{
k = (AsymmetricKeyParameter)parameters;
}
if (forSigning && !k.IsPrivate)
throw new InvalidKeyException("Signing Requires Private Key.");
if (!forSigning && k.IsPrivate)
throw new InvalidKeyException("Verification Requires Public Key.");
Reset();
dsa.Init(forSigning, parameters);
}
public virtual void Update(byte input)
{
digest.Update(input);
}
public virtual void BlockUpdate(byte[] input, int inOff, int inLen)
{
digest.BlockUpdate(input, inOff, inLen);
}
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
public virtual void BlockUpdate(ReadOnlySpan<byte> input)
{
digest.BlockUpdate(input);
}
#endif
public virtual int GetMaxSignatureSize() => encoding.GetMaxEncodingSize(GetOrder());
public virtual byte[] GenerateSignature()
{
if (!forSigning)
throw new InvalidOperationException("DSADigestSigner not initialised for signature generation.");
byte[] hash = new byte[digest.GetDigestSize()];
digest.DoFinal(hash, 0);
BigInteger[] sig = dsa.GenerateSignature(hash);
try
{
return encoding.Encode(GetOrder(), sig[0], sig[1]);
}
catch (Exception)
{
throw new InvalidOperationException("unable to encode signature");
}
}
public virtual bool VerifySignature(byte[] signature)
{
if (forSigning)
throw new InvalidOperationException("DSADigestSigner not initialised for verification");
byte[] hash = new byte[digest.GetDigestSize()];
digest.DoFinal(hash, 0);
try
{
BigInteger[] sig = encoding.Decode(GetOrder(), signature);
return dsa.VerifySignature(hash, sig[0], sig[1]);
}
catch (Exception)
{
return false;
}
}
public virtual void Reset()
{
digest.Reset();
}
protected virtual BigInteger GetOrder()
{
return dsa.Order;
}
}
}
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