Question

我正在尝试检查PDF文件的给定签名是否存在时间戳。到目前为止，我来到了这段代码：

RandomAccessFileOrArray random = 
    new RandomAccessFileOrArray(new File("temp.pdf").getAbsolutePath());

PdfReader reader = new PdfReader(random, null);
AcroFields af = reader.getAcroFields();
ArrayList<?> names = af.getSignatureNames();

//this are the signatures?
for (Object o : names){

    AcroFields.Item item = (Item) af.getFields().get((String)o);

    //this is the class for verifying the signature, 
    //how do I get it from the item?
    PdfPKCS7 pdfPKCS7 = null; //XYZ ??? 

    Calendar signingDate = pdfPKCS7.getTimeStampDate();
}

我显然可以访问签名，但我应该到PdfPKCS7类来验证签名。有谁知道我怎么去那里？

Answer 1

您应该使用AcroFields方法verifySignature(String name)返回PdfPKCS7对象以继续验证。

该方法的JavaDocs显示了它的一个使用示例：

KeyStore kall = PdfPKCS7.loadCacertsKeyStore();
PdfReader reader = new PdfReader("my_signed_doc.pdf");
AcroFields af = reader.getAcroFields();
ArrayList names = af.getSignatureNames();
for (int k = 0; k < names.size(); ++k) {
    String name = (String)names.get(k);
    System.out.println("Signature name: " + name);
    System.out.println("Signature covers whole document: " + af.signatureCoversWholeDocument(name));
    PdfPKCS7 pk = af.verifySignature(name);
    Calendar cal = pk.getSignDate();
    Certificate pkc[] = pk.getCertificates();
    System.out.println("Subject: " + PdfPKCS7.getSubjectFields(pk.getSigningCertificate()));
    System.out.println("Document modified: " + !pk.verify());
    Object fails[] = PdfPKCS7.verifyCertificates(pkc, kall, null, cal);
    if (fails == null)
        System.out.println("Certificates verified against the KeyStore");
    else
        System.out.println("Certificate failed: " + fails[1]);
}

您可以使用PdfPKCS7实例轻松添加其他代码。

Ceterum censeo ...除非您受到古老的iText版本的约束（例如由于兼容性或许可证问题），否则您应该考虑更新到当前版本。

使用iText 2.1.7检查时间戳

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