Цифровая подпись больших файлов на .NET в потоковом режиме

Стандартный механизм в .NET по подписи через SignedCms, весьма симпатичный, но есть одна проблема: для подписи необходимо передать массив байт, т.е. если надо подписать большой файл, то вначале прочитать в память в .NET потом засунуть этот же объём системному API, что весьма затратно по памяти.

Конечно, в CryptoPro есть замечательный метод SignHash, который позволяет заранее посчитать хеш и его подписать (что идентично подписи самого файла), но это только у CryptoPro, стандартное API даже на низком уровне не позволяет провести такое.

Гугление выдало код, который может шифровать в потоковом режиме, но у него обнаружилось несколько проблем:

• Почему-то используется FileStream, хотя достаточно просто Stream
• Реально всё равно читается всё содержимое (!) а потом подписывается в потоковом режиме
• Нет поддержки Detached подписи, хотя добавить её несложно
• Внаглую из сертификата берётся приватный ключ, который опять же считается RSA (наивные! совершенно не знают что в России творится)

В общем, я поправил этот код, и выкладываю его здесь, ибо взял из блога исходники, надо их таким же образом вернуть, чтобы людям было приятно.

Код, представляет из себя компиляцию того что было, с тем что надо, по-хорошему его надо причесать, но для демонстрации возможностей, пойдёт.

StreamCms.cs

using System;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Runtime.InteropServices;
using System.ComponentModel;

namespace NS1
{
 [ComVisible(false)]
 public class StreamCms
 {
  // File stream to use in callback function
  private Stream _callbackFile;

  // Streaming callback function for encoding
  private bool StreamOutputCallback(IntPtr pvArg, IntPtr pbData, int cbData, bool fFinal)
  {
   if (cbData == 0) return true;
   // Write all bytes to encoded file
   var bytes = new byte[cbData];
   Marshal.Copy(pbData, bytes, 0, cbData);
   _callbackFile.Write(bytes, 0, cbData);

   if (fFinal)
   {
    // This is the last piece. Close the file
    _callbackFile.Flush();
    _callbackFile.Close();
    _callbackFile = null;
   }

   return true;
  }

  // Encode StreamCms with streaming to support large data
  public void Encode(X509Certificate2 cert, Stream inFile, Stream outFile, bool isDetached)
  {
   // Variables

   IntPtr hProv = IntPtr.Zero;
   IntPtr SignerInfoPtr = IntPtr.Zero;
   IntPtr CertBlobsPtr = IntPtr.Zero;
   IntPtr hMsg = IntPtr.Zero;

   try
   {
    // Prepare stream for encoded info
    _callbackFile = outFile;

    // Get cert chain
    var chain = new X509Chain();
    chain.Build(cert);
    var chainElements = new X509ChainElement[chain.ChainElements.Count];
    chain.ChainElements.CopyTo(chainElements, 0);

    // Get certs in chain
    var certs = new X509Certificate2[chainElements.Length];
    for (int i = 0; i < chainElements.Length; i++)
    {
     certs[i] = chainElements[i].Certificate;
    }

    // Get context of all certs in chain
    var CertContexts = new Win32.CERT_CONTEXT[certs.Length];
    for (int i = 0; i < certs.Length; i++)
    {
     CertContexts[i] = (Win32.CERT_CONTEXT)Marshal.PtrToStructure(certs[i].Handle, typeof(Win32.CERT_CONTEXT));
    }

    // Get cert blob of all certs
    var CertBlobs = new Win32.BLOB[CertContexts.Length];
    for (int i = 0; i < CertContexts.Length; i++)
    {
     CertBlobs[i].cbData = CertContexts[i].cbCertEncoded;
     CertBlobs[i].pbData = CertContexts[i].pbCertEncoded;
    }

    // Get CSP of client certificate

    Win32.CRYPT_KEY_PROV_INFO csp;
    GetPrivateKeyInfo(GetCertContext(cert), out csp);

    bool bResult = Win32.CryptAcquireContext(
     ref hProv,
     csp.pwszContainerName,
     csp.pwszProvName,
     (int)csp.dwProvType,
     0);
    if (!bResult)
    {
     throw new Exception("CryptAcquireContext error #" + Marshal.GetLastWin32Error().ToString(), new Win32Exception(Marshal.GetLastWin32Error()));
    }

    // Populate Signer Info struct
    var SignerInfo = new Win32.CMSG_SIGNER_ENCODE_INFO();
    SignerInfo.cbSize = Marshal.SizeOf(SignerInfo);
    SignerInfo.pCertInfo = CertContexts[0].pCertInfo;
    SignerInfo.hCryptProvOrhNCryptKey = hProv;
    SignerInfo.dwKeySpec = (int)csp.dwKeySpec;
    SignerInfo.HashAlgorithm.pszObjId = cert.SignatureAlgorithm.Value; // Win32.szOID_OIWSEC_sha1;

    // Populate Signed Info struct
    var SignedInfo = new Win32.CMSG_SIGNED_ENCODE_INFO();
    SignedInfo.cbSize = Marshal.SizeOf(SignedInfo);

    SignedInfo.cSigners = 1;
    SignerInfoPtr = Marshal.AllocHGlobal(Marshal.SizeOf(SignerInfo));
    Marshal.StructureToPtr(SignerInfo, SignerInfoPtr, false);
    SignedInfo.rgSigners = SignerInfoPtr;

    SignedInfo.cCertEncoded = CertBlobs.Length;
    CertBlobsPtr = Marshal.AllocHGlobal(Marshal.SizeOf(CertBlobs[0]) * CertBlobs.Length);
    for (int i = 0; i < CertBlobs.Length; i++)
    {
     Marshal.StructureToPtr(CertBlobs[i], new IntPtr(CertBlobsPtr.ToInt64() + (Marshal.SizeOf(CertBlobs[i]) * i)), false);
    }

    SignedInfo.rgCertEncoded = CertBlobsPtr;

    // Populate Stream Info struct
    var StreamInfo = new Win32.CMSG_STREAM_INFO
                      {
                       cbContent = (int)inFile.Length,
                       pfnStreamOutput = StreamOutputCallback
                      };

    // Open message to encode
    hMsg = Win32.CryptMsgOpenToEncode(
     Win32.X509_ASN_ENCODING | Win32.PKCS_7_ASN_ENCODING,
     isDetached ? Win32.CMSG_DETACHED_FLAG : 0,
     Win32.CMSG_SIGNED,
     ref SignedInfo,
     null,
     ref StreamInfo);

    if (hMsg.Equals(IntPtr.Zero))
    {
     throw new Exception("CryptMsgOpenToEncode error #" + Marshal.GetLastWin32Error().ToString(), new Win32Exception(Marshal.GetLastWin32Error()));
    }

    // Process the whole message
    ProcessMessage(hMsg, inFile);
   }
   finally
   {
    // Clean up

    if (inFile != null)
    {
     inFile.Close();
    }

    if (_callbackFile != null)
    {
     _callbackFile.Close();
    }

    if (!CertBlobsPtr.Equals(IntPtr.Zero))
    {
     Marshal.FreeHGlobal(CertBlobsPtr);
    }

    if (!SignerInfoPtr.Equals(IntPtr.Zero))
    {
     Marshal.FreeHGlobal(SignerInfoPtr);
    }

    if (!hProv.Equals(IntPtr.Zero))
    {
     Win32.CryptReleaseContext(hProv, 0);
    }

    if (!hMsg.Equals(IntPtr.Zero))
    {
     Win32.CryptMsgClose(hMsg);
    }
   }
  }

  // Decode StreamCms with streaming to support large data
  public void Decode(Stream dataFile, Stream signFile, Stream outFile, bool isDetached)
  {
   // Variables

   IntPtr hMsg = IntPtr.Zero;
   IntPtr pSignerCertInfo = IntPtr.Zero;
   IntPtr pSignerCertContext = IntPtr.Zero;
   IntPtr hStore = IntPtr.Zero;

   try
   {
    // Get data to decode

    // Prepare stream for decoded info
    _callbackFile = outFile;

    // Populate Stream Info struct
    var StreamInfo = new Win32.CMSG_STREAM_INFO
                      {
                       cbContent = (int)signFile.Length,
                       pfnStreamOutput = StreamOutputCallback
                      };

    // Open message to decode
    hMsg = Win32.CryptMsgOpenToDecode(
     Win32.X509_ASN_ENCODING | Win32.PKCS_7_ASN_ENCODING,
     isDetached ? Win32.CMSG_DETACHED_FLAG : 0,
     0,
     IntPtr.Zero,
     IntPtr.Zero,
     ref StreamInfo);
    if (hMsg.Equals(IntPtr.Zero))
    {
     throw new Exception("CryptMsgOpenToDecode error #" + Marshal.GetLastWin32Error().ToString(), new Win32Exception(Marshal.GetLastWin32Error()));
    }

    // Process the whole message
    if (isDetached)
    {
     ProcessMessage(hMsg, signFile);
     ProcessMessage(hMsg, dataFile);
    }
    else
    {
     ProcessMessage(hMsg, signFile);
    }

    // Get signer certificate info
    int cbSignerCertInfo = 0;
    bool bResult = Win32.CryptMsgGetParam(
     hMsg,
     Win32.CMSG_SIGNER_CERT_INFO_PARAM,
     0,
     IntPtr.Zero,
     ref cbSignerCertInfo);
    if (!bResult)
    {
     throw new Exception("CryptMsgGetParam error #" + Marshal.GetLastWin32Error().ToString(), new Win32Exception(Marshal.GetLastWin32Error()));
    }

    pSignerCertInfo = Marshal.AllocHGlobal(cbSignerCertInfo);

    bResult = Win32.CryptMsgGetParam(
     hMsg,
     Win32.CMSG_SIGNER_CERT_INFO_PARAM,
     0,
     pSignerCertInfo,
     ref cbSignerCertInfo);
    if (!bResult)
    {
     throw new Exception("CryptMsgGetParam error #" + Marshal.GetLastWin32Error().ToString(), new Win32Exception(Marshal.GetLastWin32Error()));
    }

    // Open a cert store in memory with the certs from the message
    hStore = Win32.CertOpenStore(
     Win32.CERT_STORE_PROV_MSG,
     Win32.X509_ASN_ENCODING | Win32.PKCS_7_ASN_ENCODING,
     IntPtr.Zero,
     0,
     hMsg);
    if (hStore.Equals(IntPtr.Zero))
    {
     throw new Exception("CertOpenStore error #" + Marshal.GetLastWin32Error().ToString(), new Win32Exception(Marshal.GetLastWin32Error()));
    }

    // Find the signer's cert in the store
    pSignerCertContext = Win32.CertGetSubjectCertificateFromStore(
     hStore,
     Win32.X509_ASN_ENCODING | Win32.PKCS_7_ASN_ENCODING,
     pSignerCertInfo);
    if (pSignerCertContext.Equals(IntPtr.Zero))
    {
     throw new Exception("CertGetSubjectCertificateFromStore error #" + Marshal.GetLastWin32Error().ToString(), new Win32Exception(Marshal.GetLastWin32Error()));
    }

    // Set message for verifying
    var SignerCertContext = (Win32.CERT_CONTEXT)Marshal.PtrToStructure(pSignerCertContext, typeof(Win32.CERT_CONTEXT));
    bResult = Win32.CryptMsgControl(
     hMsg,
     0,
     Win32.CMSG_CTRL_VERIFY_SIGNATURE,
     SignerCertContext.pCertInfo);
    if (!bResult)
    {
     throw new Exception("CryptMsgControl error #" + Marshal.GetLastWin32Error().ToString(), new Win32Exception(Marshal.GetLastWin32Error()));
    }
   }
   finally
   {
    // Clean up
    if (!pSignerCertContext.Equals(IntPtr.Zero))
    {
     Win32.CertFreeCertificateContext(pSignerCertContext);
    }

    if (!pSignerCertInfo.Equals(IntPtr.Zero))
    {
     Marshal.FreeHGlobal(pSignerCertInfo);
    }

    if (!hStore.Equals(IntPtr.Zero))
    {
     Win32.CertCloseStore(hStore, Win32.CERT_CLOSE_STORE_FORCE_FLAG);
    }

    if (dataFile != null)
    {
     dataFile.Close();
    }

    if (signFile != null)
    {
     signFile.Close();
    }

    if (_callbackFile != null)
    {
     _callbackFile.Close();
    }

    if (!hMsg.Equals(IntPtr.Zero))
    {
     Win32.CryptMsgClose(hMsg);
    }
   }
  }

  private void ProcessMessage(IntPtr hMsg, Stream dataStream)
  {
   long streamSize = dataStream.Length;
   if (streamSize == 0)
    throw new CryptographicException("Cannot encode zero length data");
   var gchandle = new GCHandle();
   const int ChunkSize = 1024 * 1024;
   var dwSize = (int)((streamSize < ChunkSize) ? streamSize : ChunkSize);
   var pbData = new byte[dwSize];

   try
   {
    var dwRemaining = streamSize;
    gchandle = GCHandle.Alloc(pbData, GCHandleType.Pinned);
    var pbPtr = gchandle.AddrOfPinnedObject();

    while (dwRemaining > 0)
    {
     dataStream.Read(pbData, 0, dwSize);

     // Update message piece by piece     
     var bResult = Win32.CryptMsgUpdate(hMsg, pbPtr, dwSize, (dwRemaining <= dwSize));
     if (!bResult)
     {
      throw new Exception(
       "CryptMsgUpdate error #" + Marshal.GetLastWin32Error().ToString(),
       new Win32Exception(Marshal.GetLastWin32Error()));
     }

     dwRemaining -= dwSize;
     if (dwRemaining < dwSize)
      dwSize = (int)dwRemaining;

     // if (gchandle.IsAllocated)
     //  gchandle.Free();
    }
   }
   finally
   {
    if (gchandle.IsAllocated)
    {
     gchandle.Free();
    }
   }
  }

  internal static Win32.CertHandle GetCertContext(X509Certificate2 certificate)
  {
   var handle = Win32.CertDuplicateCertificateContext(certificate.Handle);
   GC.KeepAlive(certificate);
   return handle;
  }

  internal static bool GetPrivateKeyInfo(Win32.CertHandle safeCertContext, out Win32.CRYPT_KEY_PROV_INFO parameters)
  {
   parameters = new Win32.CRYPT_KEY_PROV_INFO();
   var invalidHandle = new Win32.SafeHandle(IntPtr.Zero);
   uint pcbData = 0;
   if (!Win32.CertGetCertificateContextProperty(safeCertContext, 2, invalidHandle.DangerousGetHandle(), ref pcbData))
   {
    if (Marshal.GetLastWin32Error() != -2146885628)
    {
     throw new CryptographicException(Marshal.GetLastWin32Error());
    }

    return false;
   }

   invalidHandle = Win32.LocalAlloc(0, new IntPtr(pcbData));
   if (!Win32.CertGetCertificateContextProperty(safeCertContext, 2, invalidHandle.DangerousGetHandle(), ref pcbData))
   {
    if (Marshal.GetLastWin32Error() != -2146885628)
    {
     throw new CryptographicException(Marshal.GetLastWin32Error());
    }

    return false;
   }

   parameters = (Win32.CRYPT_KEY_PROV_INFO)Marshal.PtrToStructure(invalidHandle.DangerousGetHandle(), typeof(Win32.CRYPT_KEY_PROV_INFO));
   invalidHandle.Dispose();
   return true;
  }
 }
}

Win32.cs

using System;
using System.Runtime.InteropServices;

using Microsoft.Win32.SafeHandles;

namespace NS1
{
 [ComVisible(false)]
 public class Win32
 {
  #region "CONSTS"

  public const int X509_ASN_ENCODING = 0x00000001;

  public const int PKCS_7_ASN_ENCODING = 0x00010000;

  public const int CMSG_SIGNED = 2;

  public const int CMSG_DETACHED_FLAG = 0x00000004;

  public const int AT_KEYEXCHANGE = 1;

  public const int AT_SIGNATURE = 2;

  // public const string szOID_OIWSEC_sha1 = "1.3.14.3.2.26";

  public const int CMSG_CTRL_VERIFY_SIGNATURE = 1;

  public const int CMSG_CERT_PARAM = 12;

  public const int CMSG_SIGNER_CERT_INFO_PARAM = 7;

  public const int CERT_STORE_PROV_MSG = 1;

  public const int CERT_CLOSE_STORE_FORCE_FLAG = 1;

  #endregion

  #region "STRUCTS"

  [StructLayout(LayoutKind.Sequential)]
  [ComVisible(false)]
  public struct CRYPT_ALGORITHM_IDENTIFIER
  {
   public string pszObjId;
   public BLOB Parameters;
  }

  [StructLayout(LayoutKind.Sequential)]
  [ComVisible(false)]
  public struct CERT_ID
  {
   public int dwIdChoice;
   public BLOB IssuerSerialNumberOrKeyIdOrHashId;
  }

  [StructLayout(LayoutKind.Sequential)]
  [ComVisible(false)]
  public struct CMSG_SIGNER_ENCODE_INFO
  {
   public int cbSize;
   public IntPtr pCertInfo;
   public IntPtr hCryptProvOrhNCryptKey;
   public int dwKeySpec;
   public CRYPT_ALGORITHM_IDENTIFIER HashAlgorithm;
   public IntPtr pvHashAuxInfo;
   public int cAuthAttr;
   public IntPtr rgAuthAttr;
   public int cUnauthAttr;
   public IntPtr rgUnauthAttr;
   public CERT_ID SignerId;
   public CRYPT_ALGORITHM_IDENTIFIER HashEncryptionAlgorithm;
   public IntPtr pvHashEncryptionAuxInfo;
  }

  [StructLayout(LayoutKind.Sequential)]
  [ComVisible(false)]
  public struct CERT_CONTEXT
  {
   public int dwCertEncodingType;
   public IntPtr pbCertEncoded;
   public int cbCertEncoded;
   public IntPtr pCertInfo;
   public IntPtr hCertStore;
  }

  [StructLayout(LayoutKind.Sequential)]
  [ComVisible(false)]
  public struct BLOB
  {
   public int cbData;
   public IntPtr pbData;
  }

  [StructLayout(LayoutKind.Sequential)]
  [ComVisible(false)]
  public struct CMSG_SIGNED_ENCODE_INFO
  {
   public int cbSize;
   public int cSigners;
   public IntPtr rgSigners;
   public int cCertEncoded;
   public IntPtr rgCertEncoded;
   public int cCrlEncoded;
   public IntPtr rgCrlEncoded;
   public int cAttrCertEncoded;
   public IntPtr rgAttrCertEncoded;
  }

  [StructLayout(LayoutKind.Sequential)]
  [ComVisible(false)]
  public struct CMSG_STREAM_INFO
  {
   public int cbContent;
   public StreamOutputCallbackDelegate pfnStreamOutput;
   public IntPtr pvArg;
  }

  [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
  [ComVisible(false)]
  internal struct CRYPT_KEY_PROV_INFO
  {
   internal string pwszContainerName;
   internal string pwszProvName;
   internal uint dwProvType;
   internal uint dwFlags;
   internal uint cProvParam;
   internal IntPtr rgProvParam;
   internal uint dwKeySpec;
  }

  #endregion

  #region "DELEGATES"

  [ComVisible(false)]
  public delegate bool StreamOutputCallbackDelegate(IntPtr pvArg, IntPtr pbData, int cbData, Boolean fFinal);

  #endregion

  #region "API"

  [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
  [ComVisible(false)]
  public static extern Boolean CryptAcquireContext(
    ref IntPtr hProv,
    String pszContainer,
    String pszProvider,
    int dwProvType,
    int dwFlags);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern IntPtr CryptMsgOpenToEncode(
   int dwMsgEncodingType,
   int dwFlags,
   int dwMsgType,
   ref CMSG_SIGNED_ENCODE_INFO pvMsgEncodeInfo,
   String pszInnerContentObjID,
   ref CMSG_STREAM_INFO pStreamInfo);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern IntPtr CryptMsgOpenToDecode(
   int dwMsgEncodingType,
   int dwFlags,
   int dwMsgType,
   IntPtr hCryptProv,
   IntPtr pRecipientInfo,
   ref CMSG_STREAM_INFO pStreamInfo);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern Boolean CryptMsgClose(IntPtr hCryptMsg);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern Boolean CryptMsgUpdate(
   IntPtr hCryptMsg,
   Byte[] pbData,
   int cbData,
   Boolean fFinal);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern Boolean CryptMsgUpdate(
   IntPtr hCryptMsg,
   IntPtr pbData,
   int cbData,
   Boolean fFinal);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern Boolean CryptMsgGetParam(
   IntPtr hCryptMsg,
   int dwParamType,
   int dwIndex,
   IntPtr pvData,
   ref int pcbData);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern Boolean CryptMsgControl(
   IntPtr hCryptMsg,
   int dwFlags,
   int dwCtrlType,
   IntPtr pvCtrlPara);

  [DllImport("advapi32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern Boolean CryptReleaseContext(
   IntPtr hProv,
   int dwFlags);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern IntPtr CertCreateCertificateContext(
   int dwCertEncodingType,
   IntPtr pbCertEncoded,
   int cbCertEncoded);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern bool CertFreeCertificateContext(IntPtr pCertContext);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern IntPtr CertOpenStore(
   int lpszStoreProvider,
   int dwMsgAndCertEncodingType,
   IntPtr hCryptProv,
   int dwFlags,
   IntPtr pvPara);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern IntPtr CertGetSubjectCertificateFromStore(
   IntPtr hCertStore,
   int dwCertEncodingType,
   IntPtr pCertId);

  [DllImport("Crypt32.dll", SetLastError = true)]
  [ComVisible(false)]
  public static extern IntPtr CertCloseStore(
   IntPtr hCertStore,
   int dwFlags);

  [DllImport("crypt32.dll", CharSet = CharSet.Auto, SetLastError = true)]
  internal static extern CertHandle CertDuplicateCertificateContext([In] IntPtr pCertContext);

  [DllImport("crypt32.dll", CharSet = CharSet.Auto, SetLastError = true)]
  internal static extern bool CertGetCertificateContextProperty([In] CertHandle pCertContext, [In] uint dwPropId, [In, Out] IntPtr pvData, [In, Out] ref uint pcbData);

  [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
  internal static extern SafeHandle LocalAlloc([In] uint uFlags, [In] IntPtr sizetdwBytes);

  [DllImport("kernel32.dll", SetLastError = true)]
  private static extern IntPtr LocalFree(IntPtr handle);

  #endregion

  public class SafeHandle : SafeHandleZeroOrMinusOneIsInvalid
  {
   public SafeHandle(IntPtr handle) : base(true)
   {
    SetHandle(handle);
   }


   public SafeHandle()
    : base(true)
   {
   }

   protected override bool ReleaseHandle()
   {
    return (LocalFree(handle) == IntPtr.Zero);
   }
  }

  public class CertHandle : SafeHandleZeroOrMinusOneIsInvalid
  {
   public CertHandle()
    : base(true)
   {
   }

   public CertHandle(bool ownsHandle)
    : base(ownsHandle)
   {
   }

   protected override bool ReleaseHandle()
   {
    return CertFreeCertificateContext(handle);
   }
  }
 }
}