java - Itext 签名空签名字段

Question

在我的应用程序中，我有一个用于签署 pdf 文件的选项。 pdf 签名有两种选项，一种是创建新签名，第二种是我需要签署空签名字段。我完成了创建新签名字段的部分，它工作正常，现在我在签署空签名字段时遇到问题。这是我的代码

 KeyStore ks = KeyStore.getInstance("Windows-MY");
    ks.load(null, null) ;
    //ovo smo ubacili
    Enumeration en = ks.aliases();
    // String alias = (String)en.nextElement();
    PrivateKey key = (PrivateKey)ks.getKey(alias, "password".toCharArray());
    java.security.cert.Certificate[] chain = ks.getCertificateChain(alias);
//location of pdf document to sign
    PdfReader reader = new PdfReader(jTextField1.getText());

    String [] delovi=jTextField1.getText().split("\\\\");
    String potisaniFajl=delovi[delovi.length-1];

    new File(System.getProperty("user.home") + "\\Desktop\\Potpisani Fajlovi\\").mkdirs();
//signed pdf location
    FileOutputStream fout = new FileOutputStream(System.getProperty("user.home") + "\\Desktop\\Potpisani Fajlovi\\"+potisaniFajl);
    PdfStamper stp = PdfStamper.createSignature(reader, fout, '\0',null,true);

    PdfSignatureAppearance appearance = stp.getSignatureAppearance();
    appearance.setCrypto(null, chain, null, PdfSignatureAppearance.SELF_SIGNED);
    //appearance.setCrypto(key, chain, null,PdfSignatureAppearance.WINCER_SIGNED);
    //appearance.setCrypto(null, chain, null, PdfSignatureAppearance.WINCER_SIGNED);
    appearance.setReason("Potpis kompenzacije");
    appearance.setLocation("Foobar");
    //lokacija potpisa
    appearance.setVisibleSignature(new Rectangle(100, 100, 200, 200), 1, "dva");

    appearance.setExternalDigest(new byte[128], null, "RSA");
    appearance.preClose();
    Signature signature = Signature.getInstance("SHA1withRSA");
    signature.initSign(key);
    byte buf[] = new byte[8192];
    int n;
    InputStream inp = appearance.getRangeStream();
    while ((n = inp.read(buf)) > 0) {
    signature.update(buf, 0, n);
    }
    PdfPKCS7 sig = appearance.getSigStandard().getSigner();
    sig.setExternalDigest(signature.sign(), null, "RSA");
    PdfDictionary dic = new PdfDictionary();
    dic.put(PdfName.CONTENTS,new PdfString(sig.getEncodedPKCS1()).setHexWriting(true));

    appearance.close(dic);

此代码添加了一个新签名，我需要进行哪些更改才能签署空签名字段名称“GoodSignature”

Answer 1

what changes I need to do to sign empty signature field name "GoodSignature"

在当前代码中，您调用 PdfSignatureAppearance.setVisibleSignature 的重载来创建新的签名字段:

appearance.setVisibleSignature(new Rectangle(100, 100, 200, 200), 1, "dva");

它被记录(JavaDocs)为:

/**
 * Sets the signature to be visible. It creates a new visible signature field.
 * @param pageRect the position and dimension of the field in the page
 * @param page the page to place the field. The fist page is 1
 * @param fieldName the field name or <CODE>null</CODE> to generate automatically a new field name
 */
public void setVisibleSignature(Rectangle pageRect, int page, String fieldName)

对于您的新任务，您必须使用此重载:

/**
 * Sets the signature to be visible. An empty signature field with the same name must already exist.
 * @param fieldName the existing empty signature field name
 */
public void setVisibleSignature(String fieldName)

在您的情况下，调用将是:

appearance.setVisibleSignature("GoodSignature");

话虽如此，我建议您阅读 Digital Signatures for PDF documents ，Bruno Lowagie(iText Software)的白皮书。您的代码似乎使用了许多过时的技术，您应该更新。