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// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
// <OWNER>Microsoft</OWNER>
//
//
// RSAPKCS1SignatureDeformatter.cs
//
using System;
using System.Diagnostics.Contracts;
using System.Security.Cryptography.X509Certificates;
namespace System.Security.Cryptography {
[System.Runtime.InteropServices.ComVisible(true)]
public class RSAPKCS1SignatureDeformatter : AsymmetricSignatureDeformatter {
//
// This class provides the PKCS#1 v1.5 signature format processing during
// the verification process (i.e. decrypting the object). The class has
// some special code for dealing with the CSP based RSA keys as the
// formatting and verification is done within the CSP rather than in
// managed code.
//
private RSA _rsaKey; // RSA Key value to do decrypt operation
private String _strOID; // OID value for the HASH algorithm
private bool? _rsaOverridesVerifyHash;
//
// public constructors
//
public RSAPKCS1SignatureDeformatter() {}
public RSAPKCS1SignatureDeformatter(AsymmetricAlgorithm key) {
if (key == null)
throw new ArgumentNullException("key");
Contract.EndContractBlock();
_rsaKey = (RSA) key;
}
//
// public methods
//
public override void SetKey(AsymmetricAlgorithm key) {
if (key == null)
throw new ArgumentNullException("key");
Contract.EndContractBlock();
_rsaKey = (RSA) key;
_rsaOverridesVerifyHash = default(bool?);
}
public override void SetHashAlgorithm(String strName) {
_strOID = CryptoConfig.MapNameToOID(strName, OidGroup.HashAlgorithm);
}
[System.Security.SecuritySafeCritical] // auto-generated
public override bool VerifySignature(byte[] rgbHash, byte[] rgbSignature) {
if (rgbHash == null)
throw new ArgumentNullException("rgbHash");
if (rgbSignature == null)
throw new ArgumentNullException("rgbSignature");
Contract.EndContractBlock();
if (_strOID == null)
throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingOID"));
if (_rsaKey == null)
throw new CryptographicUnexpectedOperationException(Environment.GetResourceString("Cryptography_MissingKey"));
// Two cases here -- if we are talking to the CSP version or if we are talking to some other RSA provider.
if (_rsaKey is RSACryptoServiceProvider) {
// This path is kept around for desktop compat: in case someone is using this with a hash algorithm that's known to GetAlgIdFromOid but
// not from OidToHashAlgorithmName.
int calgHash = X509Utils.GetAlgIdFromOid(_strOID, OidGroup.HashAlgorithm);
return ((RSACryptoServiceProvider)_rsaKey).VerifyHash(rgbHash, calgHash, rgbSignature);
}
else if (OverridesVerifyHash) {
HashAlgorithmName hashAlgorithmName = Utils.OidToHashAlgorithmName(_strOID);
return _rsaKey.VerifyHash(rgbHash, rgbSignature, hashAlgorithmName, RSASignaturePadding.Pkcs1);
}
else {
// Fallback compat path for 3rd-party RSA classes that don't override VerifyHash()
byte[] pad = Utils.RsaPkcs1Padding(_rsaKey, CryptoConfig.EncodeOID(_strOID), rgbHash);
// Apply the public key to the signature data to get back the padded buffer actually signed.
// Compare the two buffers to see if they match; ignoring any leading zeros
return Utils.CompareBigIntArrays(_rsaKey.EncryptValue(rgbSignature), pad);
}
}
private bool OverridesVerifyHash {
get {
if (!_rsaOverridesVerifyHash.HasValue) {
_rsaOverridesVerifyHash = Utils.DoesRsaKeyOverride(_rsaKey, "VerifyHash", new Type[] { typeof(byte[]), typeof(byte[]), typeof(HashAlgorithmName), typeof(RSASignaturePadding) });
}
return _rsaOverridesVerifyHash.Value;
}
}
}
}
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