如何使用 PDFBox 对动态创建的 PDF 文档进行数字签名？

对不起！我java很差。
我哪里不对的地方请指正，我哪里不好的地方请改进！

我正在尝试使用 PDFBox 通过以下程序对动态创建的 pdf 进行数字签名：

计划中的任务：
(i) 创建 PDF 模板
(ii) 更新 ByteRange、xref、startxref
(iii) 构建用于签名创建的原始文档
(iv) 创建分离式封装数字签名
(v) 通过连接原始文档第 I 部分、分离签名和原始 PDF 第 II 部分构建数字签名 PDF 文档

观察结果：
(i) pdfFileOutputStream.write(documentOutputStream.toByteArray());创建带有可见签名的模板 PDF 文档。

(ii) 它创建了一些 PDF 签名文档，但有错误 (a) 无效标记和 (b) 几个解析器错误
（现已在MKL的指导下更正！）

请就以下事项向我提出建议：

(i) 如何在图层 2 的可见签名中添加签名文本。

提前致谢！

    package digitalsignature;

    import java.awt.geom.AffineTransform;
    import java.io.ByteArrayInputStream;
    import java.io.ByteArrayOutputStream;
    import java.security.Signature;
    import java.util.ArrayList;
    import org.bouncycastle.cert.X509CertificateHolder;
    import org.bouncycastle.cert.jcajce.JcaCertStore;
    import org.bouncycastle.cms.CMSProcessableByteArray;
    import org.bouncycastle.cms.CMSTypedData;
    import org.bouncycastle.cms.SignerInfoGenerator;
    import org.bouncycastle.cms.SignerInfoGeneratorBuilder;
    import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;
    import org.bouncycastle.operator.jcajce.JcaDigestCalculatorProviderBuilder;
    import org.bouncycastle.util.Store;

    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.security.KeyStore;
    import java.security.PrivateKey;
    import java.security.cert.CertStore;
    import java.security.cert.Certificate;
    import java.security.cert.CollectionCertStoreParameters;
    import java.security.cert.X509Certificate;
    import java.text.DecimalFormat;
    import java.text.SimpleDateFormat;
    import java.util.Arrays;
    import java.util.Calendar;
    import java.util.Date;
    import java.util.HashMap;
    import java.util.List;

    import java.util.Map;
    import org.apache.pdfbox.cos.COSArray;
    import org.apache.pdfbox.cos.COSDictionary;
    import org.apache.pdfbox.cos.COSName;
    import org.apache.pdfbox.pdmodel.PDDocument;
    import org.apache.pdfbox.pdmodel.PDPage;
    import org.apache.pdfbox.pdmodel.PDResources;
    import org.apache.pdfbox.pdmodel.common.PDRectangle;
    import org.apache.pdfbox.pdmodel.common.PDStream;
    import org.apache.pdfbox.pdmodel.edit.PDPageContentStream;
    import org.apache.pdfbox.pdmodel.font.PDFont;
    import org.apache.pdfbox.pdmodel.font.PDType1Font;
    import org.apache.pdfbox.pdmodel.graphics.xobject.PDJpeg;
    import org.apache.pdfbox.pdmodel.graphics.xobject.PDXObjectForm;
    import org.apache.pdfbox.pdmodel.interactive.annotation.PDAppearanceDictionary;
    import org.apache.pdfbox.pdmodel.interactive.annotation.PDAppearanceStream;
    import org.apache.pdfbox.pdmodel.interactive.digitalsignature.PDSignature;
    import org.apache.pdfbox.pdmodel.interactive.digitalsignature.SignatureOptions;
    import org.apache.pdfbox.pdmodel.interactive.form.PDAcroForm;
    import org.apache.pdfbox.pdmodel.interactive.form.PDField;
    import org.apache.pdfbox.pdmodel.interactive.form.PDSignatureField;
    import org.bouncycastle.cms.CMSSignedData;
    import org.bouncycastle.cms.CMSSignedDataGenerator;
    import org.bouncycastle.cms.CMSSignedGenerator;
    import org.bouncycastle.jce.provider.BouncyCastleProvider;


    public class AffixSignature {
        String path = "D:\\reports\\";
        String onlyFileName = "";
        String pdfExtension = ".pdf";
        String pdfFileName = "";
        String pdfFilePath = "";
        String signedPdfFileName = "";
        String signedPdfFilePath = "";
        String ownerPassword = "";
        String tempSignedPdfFileName = "";
        String tempSignedPdfFilePath = "";
        String userPassword = "";
        String storePath = "resources/my.p12";
        String entryAlias = "signerCert";
        String keyStorePassword = "password";
        ByteArrayOutputStream documentOutputStream = null;
        private Certificate[] certChain;
        private static BouncyCastleProvider BC = new BouncyCastleProvider();
        int offsetContentStart = 0;
        int offsetContentEnd = 0;
        int secondPartLength = 0;
        int offsetStartxrefs = 0;
        String contentString = "";
        OutputStream signedPdfFileOutputStream;
        OutputStream pdfFileOutputStream;

        public AffixSignature() {
        try {
            SimpleDateFormat timeFormat = new SimpleDateFormat("hh_mm_ss");

            onlyFileName = "Report_" + timeFormat.format(new Date());
            pdfFileName = onlyFileName + ".pdf";
            pdfFilePath = path + pdfFileName;
            File pdfFile = new File(pdfFilePath);
            pdfFileOutputStream = new FileOutputStream(pdfFile);

            signedPdfFileName = "Signed_" + onlyFileName + ".pdf";
            signedPdfFilePath = path + signedPdfFileName;
            File signedPdfFile = new File(signedPdfFilePath);
            signedPdfFileOutputStream = new FileOutputStream(signedPdfFile);

            String tempFileName = "Temp_Report_" + timeFormat.format(new Date());
            String tempPdfFileName = tempFileName + ".pdf";
            String tempPdfFilePath = path + tempPdfFileName;
            File tempPdfFile = new File(tempPdfFilePath);
            OutputStream tempSignedPdfFileOutputStream = new FileOutputStream(tempPdfFile);

            PDDocument document = new PDDocument();
            PDDocumentCatalog catalog = document.getDocumentCatalog();
            PDPage page = new PDPage(PDPage.PAGE_SIZE_A4);
            PDPageContentStream contentStream = new PDPageContentStream(document, page);


            PDFont font = PDType1Font.HELVETICA;
            Map<String, PDFont> fonts = new HashMap<String, PDFont>();
            fonts = new HashMap<String, PDFont>();
            fonts.put("F1", font);

//            contentStream.setFont(font, 12);
            contentStream.setFont(font, 12);
            contentStream.beginText();
            contentStream.moveTextPositionByAmount(100, 700);
            contentStream.drawString("DIGITAL SIGNATURE TEST");
            contentStream.endText();
            contentStream.close();
            document.addPage(page);

//To Affix Visible Digital Signature
            PDAcroForm acroForm = new PDAcroForm(document);
            catalog.setAcroForm(acroForm);

            PDSignatureField sf = new PDSignatureField(acroForm);

            PDSignature pdSignature = new PDSignature();
            page.getAnnotations().add(sf.getWidget());
            pdSignature.setName("sign");
            pdSignature.setByteRange(new int[]{0, 0, 0, 0});
            pdSignature.setContents(new byte[4 * 1024]);
            pdSignature.setFilter(PDSignature.FILTER_ADOBE_PPKLITE);
            pdSignature.setSubFilter(PDSignature.SUBFILTER_ADBE_PKCS7_DETACHED);
            pdSignature.setName("NAME");
            pdSignature.setLocation("LOCATION");
            pdSignature.setReason("SECURITY");
            pdSignature.setSignDate(Calendar.getInstance());
            List<PDField> acroFormFields = acroForm.getFields();

            sf.setSignature(pdSignature);
            sf.getWidget().setPage(page);

            COSDictionary acroFormDict = acroForm.getDictionary();
            acroFormDict.setDirect(true);
            acroFormDict.setInt(COSName.SIG_FLAGS, 3);
            acroFormFields.add(sf);

            PDRectangle frmRect = new PDRectangle();
//            float[] frmRectParams = {lowerLeftX,lowerLeftY,upperRightX,upperRight};
//            float[] frmRectLowerLeftUpperRightCoordinates = {5f, page.getMediaBox().getHeight() - 50f, 100f, page.getMediaBox().getHeight() - 5f};
            float[] frmRectLowerLeftUpperRightCoordinates = {5f, 5f, 205f, 55f};
            frmRect.setUpperRightX(frmRectLowerLeftUpperRightCoordinates[2]);
            frmRect.setUpperRightY(frmRectLowerLeftUpperRightCoordinates[3]);
            frmRect.setLowerLeftX(frmRectLowerLeftUpperRightCoordinates[0]);
            frmRect.setLowerLeftY(frmRectLowerLeftUpperRightCoordinates[1]);

            sf.getWidget().setRectangle(frmRect);

            COSArray procSetArr = new COSArray();
            procSetArr.add(COSName.getPDFName("PDF"));
            procSetArr.add(COSName.getPDFName("Text"));
            procSetArr.add(COSName.getPDFName("ImageB"));
            procSetArr.add(COSName.getPDFName("ImageC"));
            procSetArr.add(COSName.getPDFName("ImageI"));

            String signImageFilePath = "resources/sign.JPG";
            File signImageFile = new File(signImageFilePath);
            InputStream signImageStream = new FileInputStream(signImageFile);
            PDJpeg img = new PDJpeg(document, signImageStream);

            PDResources holderFormResources = new PDResources();
            PDStream holderFormStream = new PDStream(document);
            PDXObjectForm holderForm = new PDXObjectForm(holderFormStream);
            holderForm.setResources(holderFormResources);
            holderForm.setBBox(frmRect);
            holderForm.setFormType(1);

            PDAppearanceDictionary appearance = new PDAppearanceDictionary();
            appearance.getCOSObject().setDirect(true);
            PDAppearanceStream appearanceStream = new PDAppearanceStream(holderForm.getCOSStream());
            appearance.setNormalAppearance(appearanceStream);
            sf.getWidget().setAppearance(appearance);
            acroFormDict.setItem(COSName.DR, holderFormResources.getCOSDictionary());

            PDResources innerFormResources = new PDResources();
            PDStream innerFormStream = new PDStream(document);
            PDXObjectForm innerForm = new PDXObjectForm(innerFormStream);
            innerForm.setResources(innerFormResources);
            innerForm.setBBox(frmRect);
            innerForm.setFormType(1);

            String innerFormName = holderFormResources.addXObject(innerForm, "FRM");

            PDResources imageFormResources = new PDResources();
            PDStream imageFormStream = new PDStream(document);
            PDXObjectForm imageForm = new PDXObjectForm(imageFormStream);
            imageForm.setResources(imageFormResources);
            byte[] AffineTransformParams = {1, 0, 0, 1, 0, 0};
            AffineTransform affineTransform = new AffineTransform(AffineTransformParams[0], AffineTransformParams[1], AffineTransformParams[2], AffineTransformParams[3], AffineTransformParams[4], AffineTransformParams[5]);
            imageForm.setMatrix(affineTransform);
            imageForm.setBBox(frmRect);
            imageForm.setFormType(1);

            String imageFormName = innerFormResources.addXObject(imageForm, "n");
            String imageName = imageFormResources.addXObject(img, "img");

            innerForm.getResources().getCOSDictionary().setItem(COSName.PROC_SET, procSetArr);
            page.getCOSDictionary().setItem(COSName.PROC_SET, procSetArr);
            innerFormResources.getCOSDictionary().setItem(COSName.PROC_SET, procSetArr);
            imageFormResources.getCOSDictionary().setItem(COSName.PROC_SET, procSetArr);
            holderFormResources.getCOSDictionary().setItem(COSName.PROC_SET, procSetArr);

            String holderFormComment = "q 1 0 0 1 0 0 cm /" + innerFormName + " Do Q \n";
            String innerFormComment = "q 1 0 0 1 0 0 cm /" + imageFormName + " Do Q\n";
            String imgFormComment = "q " + 100 + " 0 0 50 0 0 cm /" + imageName + " Do Q\n";

            appendRawCommands(holderFormStream.createOutputStream(), holderFormComment);
            appendRawCommands(innerFormStream.createOutputStream(), innerFormComment);
            appendRawCommands(imageFormStream.createOutputStream(), imgFormComment);

            documentOutputStream = new ByteArrayOutputStream();
            document.save(documentOutputStream);
            document.close();
            tempSignedPdfFileOutputStream.write(documentOutputStream.toByteArray());
            generateSignedPdf();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void appendRawCommands(OutputStream os, String commands) throws IOException {
        os.write(commands.getBytes("ISO-8859-1"));
        os.close();
    }

    public void generateSignedPdf() {
        try {
            //Find the Initial Byte Range Offsets
            String docString = new String(documentOutputStream.toByteArray(), "ISO-8859-1");
            offsetContentStart = (documentOutputStream.toString().indexOf("Contents <") + 10 - 1);
            offsetContentEnd = (documentOutputStream.toString().indexOf("000000>") + 7);
            secondPartLength = (documentOutputStream.size() - documentOutputStream.toString().indexOf("000000>") - 7);
            //Calculate the Updated ByteRange
            String initByteRange = "";
            if (docString.indexOf("/ByteRange [0 1000000000 1000000000 1000000000]") > 0) {
                initByteRange = "/ByteRange [0 1000000000 1000000000 1000000000]";
            } else if (docString.indexOf("/ByteRange [0 0 0 0]") > 0) {
                initByteRange = "/ByteRange [0 0 0 0]";
            } else {
                System.out.println("No /ByteRange Token is Found!");
                System.exit(1);
            }

            String interimByteRange = "/ByteRange [0 " + offsetContentStart + " " + offsetContentEnd + " " + secondPartLength + "]";
            int byteRangeLengthDifference = interimByteRange.length() - initByteRange.length();
            offsetContentStart = offsetContentStart + byteRangeLengthDifference;
            offsetContentEnd = offsetContentEnd + byteRangeLengthDifference;
            String finalByteRange = "/ByteRange [0 " + offsetContentStart + " " + offsetContentEnd + " " + secondPartLength + "]";
            byteRangeLengthDifference += interimByteRange.length() - finalByteRange.length();
            //Replace the ByteRange
            docString = docString.replace(initByteRange, finalByteRange);

            //Update xref Table
            int xrefOffset = docString.indexOf("xref");
            int startObjOffset = docString.indexOf("0000000000 65535 f") + "0000000000 65535 f".length() + 1;
            int trailerOffset = docString.indexOf("trailer") - 2;
            String initialXrefTable = docString.substring(startObjOffset, trailerOffset);
            int signObjectOffset = docString.indexOf("/Type /Sig") - 3;
            String updatedXrefTable = "";
            while (initialXrefTable.indexOf("n") > 0) {
                String currObjectRefEntry = initialXrefTable.substring(0, initialXrefTable.indexOf("n") + 1);
                String currObjectRef = currObjectRefEntry.substring(0, currObjectRefEntry.indexOf(" 00000 n"));
                int currObjectOffset = Integer.parseInt(currObjectRef.trim().replaceFirst("^0+(?!$)", ""));
                if ((currObjectOffset + byteRangeLengthDifference) > signObjectOffset) {
                    currObjectOffset += byteRangeLengthDifference;
                    int currObjectOffsetDigitsCount = Integer.toString(currObjectOffset).length();
                    currObjectRefEntry = currObjectRefEntry.replace(currObjectRefEntry.substring(currObjectRef.length() - currObjectOffsetDigitsCount, currObjectRef.length()), Integer.toString(currObjectOffset));
                    updatedXrefTable += currObjectRefEntry;
                } else {
                    updatedXrefTable += currObjectRefEntry;
                }
                initialXrefTable = initialXrefTable.substring(initialXrefTable.indexOf("n") + 1);
            }
            //Replace with Updated xref Table
            docString = docString.substring(0, startObjOffset).concat(updatedXrefTable).concat(docString.substring(trailerOffset));

            //Update startxref
            int startxrefOffset = docString.indexOf("startxref");
            //Replace with Updated startxref
            docString = docString.substring(0, startxrefOffset).concat("startxref\n".concat(Integer.toString(xrefOffset))).concat("\n%%EOF\n");

            //Construct Original Document For Signature by Removing Temporary Enveloped Detached Signed Content(000...000)
            contentString = docString.substring(offsetContentStart + 1, offsetContentEnd - 1);
            String docFirstPart = docString.substring(0, offsetContentStart);
            String docSecondPart = docString.substring(offsetContentEnd);
            String docForSign = docFirstPart.concat(docSecondPart);

            //Generate Signature
            pdfFileOutputStream.write(docForSign.getBytes("ISO-8859-1"));
            File keyStorefile = new File(storePath);
            InputStream keyStoreInputStream = new FileInputStream(keyStorefile);
            KeyStore keyStore = KeyStore.getInstance("PKCS12");
            keyStore.load(keyStoreInputStream, keyStorePassword.toCharArray());
            certChain = keyStore.getCertificateChain(entryAlias);
            PrivateKey privateKey = (PrivateKey) keyStore.getKey(entryAlias, keyStorePassword.toCharArray());
            List<Certificate> certList = new ArrayList<Certificate>();
            certList = Arrays.asList(certChain);
            Store store = new JcaCertStore(certList);
//            String algorithm="SHA1WithRSA";
//            String algorithm="SHA2WithRSA";
            String algorithm = "MD5WithRSA";
            //String algorithm = "DSA";

            //Updated Sign Method
            CMSTypedData msg = new CMSProcessableByteArray(docForSign.getBytes("ISO-8859-1"));
            CMSSignedDataGenerator generator = new CMSSignedDataGenerator();
            /* Build the SignerInfo generator builder, that will build the generator... that will generate the SignerInformation... */
            SignerInfoGeneratorBuilder signerInfoBuilder = new SignerInfoGeneratorBuilder(new JcaDigestCalculatorProviderBuilder().setProvider(BC).build());
            //JcaContentSignerBuilder contentSigner = new JcaContentSignerBuilder("SHA2withRSA");
            JcaContentSignerBuilder contentSigner = new JcaContentSignerBuilder(algorithm);
            contentSigner.setProvider(BC);
            SignerInfoGenerator signerInfoGenerator = signerInfoBuilder.build(contentSigner.build(privateKey), new X509CertificateHolder(certList.get(0).getEncoded()));
            generator.addSignerInfoGenerator(signerInfoGenerator);
            generator.addCertificates(store);
            CMSSignedData signedData = generator.generate(msg, false);
            String apHexEnvelopedData = org.apache.commons.codec.binary.Hex.encodeHexString(signedData.getEncoded()).toUpperCase();
            //Construct Content Tag Data
            contentString = apHexEnvelopedData.concat(contentString).substring(0, contentString.length());
            contentString = "<".concat(contentString).concat(">");
            //Construct Signed Document
            String signedDoc = docFirstPart.concat(contentString).concat(docSecondPart);
            //Write Signed Document to File
            signedPdfFileOutputStream.write(signedDoc.getBytes("ISO-8859-1"));
            signedPdfFileOutputStream.close();
            signedDoc = null;
        } catch (Exception e) {
            throw new RuntimeException("Error While Generating Signed Data", e);
        }
    }

    public static void main(String[] args) {
        AffixSignature affixSignature = new AffixSignature();
    }
}

在 MKL 的有力指导下，现在更新的代码签署了新创建的文档。感谢 MKL！

虽然最初这些提示是作为对原始问题的评论提出的，但现在值得将它们表述为答案：

代码问题

虽然有太多代码需要在不花费大量时间的情况下进行审查和修复，而且最初缺少示例 PDF 是一个障碍，但快速扫描代码会发现一些问题：

• The appendRawCommands(XXXFormStream.createOutputStream(), YYY)调用很可能会导致 PDFBox 出现问题：多次为同一表单创建输出流可能会成为问题，并且还会在表单之间来回切换。

• 此外，写入同一流的多个字符串之间似乎没有空格，从而导致未知Qq运营商。此外appendRawCommands方法使用 UTF-8，这对于 PDF 来说是陌生的。

• The generateSignedDocument最有可能造成相当大的损害，因为它假设它可以像处理文本文件一样处理 PDF。一般来说情况并非如此。

结果 PDF 问题

OP 最终提供的示例结果 PDF 可以查明一些实际实现的问题：

• 比较两个文档（Report_08_05_23.pdf 和 Signed_Report_08_05_23.pdf）的字节，我们会发现有许多不需要的更改，乍一看尤其是用问号替换某些字节。这是由于使用ByteArrayOutputStream.toString()轻松地对文档进行操作并最终将其更改回byte[].

  例如。参见JavaDocs 的ByteArrayOutputStream.toString()

  * <p> This method always replaces malformed-input and unmappable-character
  * sequences with the default replacement string for the platform's
  * default character set. The {@linkplain java.nio.charset.CharsetDecoder}
  * class should be used when more control over the decoding process is
  * required.
  

  某些字节值不代表中的字符平台的默认字符集因此被转化为Unicode 替换角色并在最终转变为byte[]变为 0x3f（问号的 ASCII 代码）。此更改会终止压缩流内容，包括内容流和图像流。

  要解决这个问题，必须与byte and byte[]操作而不是String在这里进行操作。

• 流 8 0 在其 XObject 资源中引用自身，这可能会使任何 pdf 查看器出现问题。请避免这种循环。

签名容器问题

签名不验证。因此，也对其进行审查。

• 检查签名容器可以发现它是错误的：尽管签名是adbe.pkcs7.detached，签名容器嵌入数据。看看代码，原因就很清楚了：

  CMSSignedData sigData = generator.generate(msg, true);
  

  The true参数要求 BC 嵌入msg data.

• 开始查看签名代码后，另一个问题变得明显：msg上面的数据不仅仅是摘要，它们已经是签名：

  Signature signature = Signature.getInstance(algorithm, BC);
  signature.initSign(privateKey);
  signature.update(docForSign.getBytes());
  CMSTypedData msg = new CMSProcessableByteArray(signature.sign());
  

这是错误的，因为后来创建的SignerInfoGenerator用于创建实际签名。

Edit:在修复或至少解决了前面提到的问题后，Adobe Reader 仍然不接受签名。因此，再看一下代码：

哈希值计算问题

OP构建了这个字节范围 value

String finalByteRange = "/ByteRange [0 " + offsetContentStart + " " + offsetContentEnd + " " + secondPartLength + "]";

以及后来的几集

String docFirstPart = docString.substring(0, offsetContentStart + 1);
String docSecondPart = docString.substring(offsetContentEnd - 1);

The + 1 and - 1旨在使这些文档部分还包括< and >封装签名字节。但OP也使用这些字符串来构造签名数据：

String docForSign = docFirstPart.concat(docSecondPart);

这是错误的，有符号字节不包含< and >。因此，后来计算的哈希值也是错误的，Adobe Reader 有充分的理由假设该文档已被操纵。

话虽如此，还有其他问题肯定会时不时地出现：

偏移和长度更新问题

OP插入字节范围如下：

String interimByteRange = "/ByteRange [0 " + offsetContentStart + " " + offsetContentEnd + " " + secondPartLength + "]";
int byteRangeLengthDifference = interimByteRange.length() - initByteRange.length();
offsetContentStart = offsetContentStart + byteRangeLengthDifference;
offsetContentEnd = offsetContentEnd + byteRangeLengthDifference;
String finalByteRange = "/ByteRange [0 " + offsetContentStart + " " + offsetContentEnd + " " + secondPartLength + "]";
byteRangeLengthDifference += interimByteRange.length() - finalByteRange.length();
//Replace the ByteRange
docString = docString.replace(initByteRange, finalByteRange);

每一个在一段时间offsetContentStart or offsetContentEnd将略低于约 10^n，然后略高于。线路

byteRangeLengthDifference += interimByteRange.length() - finalByteRange.length();

试图弥补这一点，但是finalByteRange（最终被插入到文档中）仍然包含未更正的值。

以类似的方式，外部参照的表示开始像这样插入

docString = docString.substring(0, startxrefOffset).concat("startxref\n".concat(Integer.toString(xrefOffset))).concat("\n%%EOF\n");

也可能比以前更长，这使得字节范围（预先计算）无法覆盖整个文档。

此外，使用整个文档的文本搜索来查找相关 PDF 对象的偏移量

offsetContentStart = (documentOutputStream.toString().indexOf("Contents <") + 10 - 1);
offsetContentEnd = (documentOutputStream.toString().indexOf("000000>") + 7);
...
int xrefOffset = docString.indexOf("xref");
...
int startxrefOffset = docString.indexOf("startxref");

对于通用文档将失败。例如。如果文档中已经有以前的签名，很可能会像这样识别出错误的索引。