如何：将经过身份验证的属性添加到签名邮件
此示例使用 System.Security.Cryptography.Pkcs 创建 CMS/PKCS #7 签名邮件。该邮件由单个签名者签名。邮件包含时间戳作为经过身份验证的属性。这意味着邮件内容和时间戳都经过签名。然后验证该邮件上的签名，验证邮件内容和时间戳是否是真实的。
示例
此示例还说明了分离的 CMS/PKCS #7 邮件的用法。这意味着邮件内容不存储在 CMS/PKCS #7 邮件中。因此，邮件内容必须传递到验证 CMS/PKCS #7 邮件的方法中。
此示例使用下列类：
以下示例要求“我的证书”存储中包含使用者名称为“MessageSigner1”的公钥证书，并且存在关联的私钥。
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这只是一个说明性的示例。生产环境可能会使用不同的模型，邮件的发件人和收件人在不同的进程中使用唯一的公钥凭据执行操作。 |
使用 Makecert.exe 实用程序设置此示例，可以通过多种方法实现。Certificate Creation Tool (Makecert.exe) 是用于生成测试证书的一种很方便的实用程序。在生产环境中，证书由证书颁发机构生成。
下列 Makecert 命令生成所需的公钥证书和私钥。
Makecert -n "CN=MessageSigner1" -ss My
// Copyright (c) Microsoft Corporation. All rights reserved.
#region Using directives
using System;
using System.Security.Cryptography;
using System.Security.Cryptography.Pkcs;
using System.Security.Cryptography.X509Certificates;
using System.Text;
#endregion
namespace AddAnAuthenticatedAttributeToASignedMessage
{
class SignedCmsAuthenticatedAttribute
{
const String signerName = "MessageSigner1";
static void Main(string[] args)
{
Console.WriteLine("System.Security.Cryptography.Pkcs " +
"Sample: Single-signer signed and verified message");
// Original message.
const String msg = "This is the message to be signed. " +
"A time stamp is included as an authenticated " +
"attribute.";
Console.WriteLine("\nOriginal message (len {0}): {1} ",
msg.Length, msg);
// Convert message to array of bytes for signing.
Encoding unicode = Encoding.Unicode;
byte[] msgBytes = unicode.GetBytes(msg);
Console.WriteLine("\n\n------------------------------");
Console.WriteLine(" SETUP OF CREDENTIALS ");
Console.WriteLine("------------------------------\n");
X509Certificate2 signerCert = GetSignerCert();
Console.WriteLine("\n\n----------------------");
Console.WriteLine(" SENDER SIDE ");
Console.WriteLine("----------------------\n");
byte[] encodedSignedCms = SignMsg(msgBytes, signerCert);
Console.WriteLine("\n\n------------------------");
Console.WriteLine(" RECIPIENT SIDE ");
Console.WriteLine("------------------------\n");
if (VerifyMsg(msgBytes, encodedSignedCms))
{
Console.WriteLine("\nMessage verified");
}
else
{
Console.WriteLine("\nMessage failed to verify");
}
}
// Open the My (or Personal) certificate store and search for
// credentials to sign the message with. The certificate
// must have the subject name "MessageSigner1".
static public X509Certificate2 GetSignerCert()
{
// Open the My certificate store.
X509Store storeMy = new X509Store(StoreName.My,
StoreLocation.CurrentUser);
storeMy.Open(OpenFlags.ReadOnly);
// Display certificates to help troubleshoot
// the example's setup.
Console.WriteLine("Found certs with the following subject " +
"names in the {0} store:", storeMy.Name);
foreach (X509Certificate2 cert in storeMy.Certificates)
{
Console.WriteLine("\t{0}", cert.SubjectName.Name);
}
// Find the signer's certificate.
X509Certificate2Collection certColl =
storeMy.Certificates.Find(X509FindType.FindBySubjectName,
signerName, false);
Console.WriteLine(
"Found {0} certificates in the {1} store with name {2}",
certColl.Count, storeMy.Name, signerName);
// Check to see if the certificate suggested by the example
// requirements is not present.
if (certColl.Count == 0)
{
Console.WriteLine(
"A suggested certificate to use for this example " +
"is not in the certificate store. Select " +
"an alternate certificate to use for " +
"signing the message.");
}
storeMy.Close();
// If more than one matching cert, return the first one.
return certColl[0];
}
// Sign the message with the private key of the signer.
static public byte[] SignMsg(
Byte[] msg,
X509Certificate2 signerCert)
{
// Place message in a ContentInfo object.
// This is required to build a SignedCms object.
ContentInfo contentInfo = new ContentInfo(msg);
// Instantiate SignedCms object with the ContentInfo above.
// Has default SubjectIdentifierType IssuerAndSerialNumber.
// Set the Detached property value to true, so message is
// not included in the encoded SignedCms.
SignedCms signedCms = new SignedCms(contentInfo, true);
// Formulate a CmsSigner object for the signer.
CmsSigner cmsSigner = new CmsSigner(signerCert);
// Add an authenticated time stamp attribute to the signer.
// The signing time is the current time.
cmsSigner.SignedAttributes.Add(new Pkcs9SigningTime());
// Sign the CMS/PKCS #7 message.
Console.Write("Computing signature with signer subject " +
"name {0} ... ", signerCert.SubjectName.Name);
signedCms.ComputeSignature(cmsSigner);
Console.WriteLine("Done.");
// Encode the CMS/PKCS #7 message.
return signedCms.Encode();
}
// Verify the encoded SignedCms message and return a Boolean
// value that specifies whether the verification was successful.
static public bool VerifyMsg(byte[] msgBytes, byte[] encodedSignedCms)
{
Pkcs9SigningTime st = new Pkcs9SigningTime();
// Build a ContentInfo object with the message bytes. This
// is necessary because the message is detached from the
// SignedCms object.
ContentInfo contentInfo = new ContentInfo(msgBytes);
// Prepare an object in which to decode and verify.
SignedCms signedCms = new SignedCms(contentInfo, true);
signedCms.Decode(encodedSignedCms);
// Catch a verification exception if you want to
// advise the message recipient that
// security actions might be appropriate.
try
{
// Verify signature. Do not validate signer
// certificate for the purposes of this example.
// Note that in a production environment, validating
// the signer certificate chain will probably
// be necessary.
Console.Write("Checking signature on message ... ");
signedCms.CheckSignature(true);
Console.WriteLine("Done.");
// Report the signing time for the CMS/PKCS #7 message.
for (int i = 0; i < signedCms.SignerInfos[0].SignedAttributes.Count; i++)
{
//if (signedCms.SignerInfos[0].SignedAttributes[i].
//Values[0].GetType().Equals(st.GetType()))
if (signedCms.SignerInfos[0].SignedAttributes[i].Values[0] is Pkcs9SigningTime)
{
Pkcs9SigningTime signingTime = (Pkcs9SigningTime)signedCms.SignerInfos[0].SignedAttributes[i].Values[0];
Console.WriteLine("Signing time: {0}", signingTime.SigningTime);
}
}
}
catch (System.Security.Cryptography.CryptographicException e)
{
Console.WriteLine("VerifyMsg caught exception: {0}",
e.Message);
Console.WriteLine("Verification of the signed PKCS #7 " +
"failed. The message, signatures, " +
" countersignatures, or authenticated attributes " +
" may have been modified in transit or storage. The " +
" message signers or countersigners may not be who " +
" they claim to be. The message's authenticity or " +
" integrity, or both, are not guaranteed.");
return false;
}
return true;
}
}
}
请参见
参考
CmsSigner
ContentInfo
SignedCms
X509Certificate2
X509Certificate2Collection
X509Store
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