问使用IText、ITextSharp或BouncyCastle从pdf文件中提取pkcs7 (byte[]

EN

public static byte[] ExtractPKCS7From(string path)
{
    AcroFields acroFields = new PdfReader(path).AcroFields;
    List<string> names = acroFields.GetSignatureNames();

    foreach(var name in names)
    {
        PdfDictionary dict = acroFields.GetSignatureDictionary(name);
        PdfString contents =
            (PdfString)PdfReader.GetPdfObject(dict.Get(PdfName.CONTENTS));

        return contents.GetOriginalBytes();
    }
    return null;
}

PdfReader r = new PdfReader(fOs);
AcroFields af = r.getAcroFields();
ArrayList<String> listNames = af.getSignatureNames();
for(String x : listNames){
    PdfPKCS7 pkcs7 = af.verifySignature(signature);
}