EWS - 數字簽名電子郵件（smime.p7m）

Question

我正在嘗試使用EWS閱讀數字簽名電子郵件的內容。不幸的是，當我使用的方法與EnvelopeCMS我得到一個異常：

System.Security.Cryptography.CryptographicException：ASN1 - 壞標籤 價值滿足。

在System.Security.Cryptography.Pkcs.EnvelopedCms.OpenToDecode（字節[] encodedMessage）
在System.Security.Cryptography.Pkcs.EnvelopedCms.Decode（字節[] encodedMessage）在myExchange.Email.DecryptToFile（

Byte [] data）

（encodedMessage是smime.p7m電子郵件的附件）。

編輯：這是一個關鍵的代碼片段：

foreach (Attachment attachment in emailMessage.Attachments) 
{ 
    if (attachment is FileAttachment) 
    { 
     FileAttachment fileAttachment = attachment as FileAttachment; 

     if (fileAttachment.Name == "smime.p7m")       
     { 
       byte[] content = fileAttachment.Content; 

       MemoryStream stream = new MemoryStream(); 
       fileAttachment.Load(stream); 
       StreamReader stReader = new StreamReader(stream); 
       stream.Seek(0, SeekOrigin.Begin); 
       content = stream.GetBuffer(); 

       var encrypted = new System.Security.Cryptography.Pkcs.EnvelopedCms(); 
       encrypted.Decode(content); // <==== Here occurs exception 

       encrypted.Decrypt(); 
       byte[] unencryptedButRawMimeEntity = encrypted.ContentInfo.Content; 
     } 
    } 
} 

更多的電子郵件 - EWS輸出控制檯說，它有一個附件「mutipart /簽訂了」內涵式

<m:ResponseCode>NoError</m:ResponseCode> 
      <m:Attachments> 
       <t:FileAttachment> 
       <t:AttachmentId Id="AAMkADNi(... CUT ...)T5PWd/bDM=" /> 
       <t:Name>smime.p7m</t:Name> 
       <t:ContentType>multipart/signed</t:ContentType> 

Answer 1

沒有測試過，所以請讓我知道我會想象這樣的事情...

foreach (Attachment attachment in emailMessage.Attachments) 
{ 
    FileAttachment fileAttachment = attachment as FileAttachment 
    if (attachment != null) 
    {   
     fileAttachment.Load(); 
     if (fileAttachment.Name == "smime.p7m")       
     { 
       byte[] content = fileAttachment.Content; 

       var encrypted = new EnvelopedCms(); 
       encrypted.Decode(content); 
       encrypted.Decrypt(); 
       byte[] unencryptedButRawMimeEntity = encrypted.ContentInfo.Content; 
     } 
    } 
}