如何从PKCS#7中提取PKCS#1签名

Question

我知道PKCS#7 = Certificate + Optional raw data + Signature in PKCS#1 format我需要从PKCS#7签名中提取PKCS#1如何在C#中做到这一点。我可以使用弹跳城堡来做这件事吗，这是我的实现。将PKCS#7转换为ASN.1并采用PKCS#1格式的最后一个序列

Asn1InputStream asn1 = new Asn1InputStream(pkcs7Stream);
Asn1Sequence sequence = (Asn1Sequence)asn1.ReadObject().ToAsn1Object();
var sequenceString = sequence.ToString();
var lastCommaIndex = sequenceString.LastIndexOf(",");
var pkcs1HexStr = sequenceString.Substring(lastCommaIndex + 3).Replace("]", string.Empty);

是否有其他符合资格的方法来获取PKCS#1

Answer 1

SignedCms类可以为.NET核心2.1+或.NET框架4.7.2+执行此操作：

SignedCms cms = new SignedCms();
cms.Decode(message);
return cms.SignerInfos[0].GetSignature();

当然，假设您想要第一个签名者的签名。(需要net472+的是GetSignature方法)

其他签名者或副签者也是可用的，只是通过对象模型的不同方面。

Answer 2

感谢@bartonis的帮助和指导

下面是使用bouncy castle的实现

public static byte[] GetRaw(byte[] input)
{
    SignerInfo signerInfo = GetSignerInfo(input);
    return signerInfo?.EncryptedDigest?.GetOctets();
}
private static SignerInfo GetSignerInfo(byte[] input)
{
    Asn1InputStream cmsInputStream = new Asn1InputStream(input);
    Asn1Object asn1Object = cmsInputStream.ReadObject();

    Asn1Sequence asn1Sequence = Asn1Sequence.GetInstance(asn1Object);
    SignedData signedData = GetSignedData(asn1Sequence);
    SignerInfo signerInfo = GetSignerInfo(signedData);
    if (signerInfo?.UnauthenticatedAttributes != null)
    {
        signedData = GetSignerInfo(signerInfo);
        signerInfo = GetSignerInfo(signedData);
    }
    return signerInfo;
}
private static SignerInfo GetSignerInfo(SignedData signedData)
{
    Asn1Encodable[] Asn1Encodables = signedData?.SignerInfos?.ToArray();
    if (Asn1Encodables != null)
    {
        if (Asn1Encodables.Length > 0)
        {
            SignerInfo signerInfo = SignerInfo.GetInstance(Asn1Encodables[0]);
            return signerInfo;
        }
    }
    return null;
}
private static SignedData GetSignedData(Asn1Sequence sequence)
{
    var rootContent = ContentInfo.GetInstance(sequence);
    var signedData = SignedData.GetInstance(rootContent.Content);
    return signedData;
}
private static SignedData GetSignerInfo(SignerInfo signerInfo)
{
    Asn1Encodable[] asn1Encodables = signerInfo.UnauthenticatedAttributes.ToArray();
    foreach (var asn1Encodable in asn1Encodables)
    {
        Asn1Sequence sequence = Asn1Sequence.GetInstance(asn1Encodable);
        DerObjectIdentifier OID = (DerObjectIdentifier)sequence[0];
        if (OID.Id == "1.2.840.113549.1.9.16.2.14")
        {
            Asn1Sequence newSequence =Asn1Sequence.GetInstance(Asn1Set.GetInstance(sequence[1])[0]);
            SignedData signedData = GetSignedData(newSequence);
            return signedData;
        }
    }
    return null;
}