基于Apache PDFBox的PDF数字签名
在Java语言环境中完成数字签名主要基于itext-pdf、PDFBox两种工具，itext-pdf受商业限制，应用于商业服务中需要购买授权。PDFBox是apache基金会开源项目，基于apache2.0开源协议，不受商业限制，开发者可放心使用。以下是基于PDFBox的数字签名源码，使用该源码可使用PDFBox对PDF格式的文件进行数字。此外，完成数字签名还生成数字证书，全流程的数字签名示例可下载开源项目模拟数字签名全流程。开源数字签名访问地址：https://gitee.com/kaifangqian
`package org.resrun.sdk.pdfbox;
import org.resrun.sdk.pdfbox.vo.AssinaturaModel;
import org.apache.pdfbox.Loader;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.io.IOUtils;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
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.graphics.form.PDFormXObject;
import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject;
import org.apache.pdfbox.pdmodel.interactive.annotation.PDAnnotationWidget;
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.apache.pdfbox.util.Matrix;
import java.awt.geom.AffineTransform;
import java.awt.geom.Rectangle2D;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;
import java.util.Calendar;
import java.util.List;
public class AssinaturaPDF extends SignatureBase {
private SignatureOptions signatureOptions;
private AssinaturaModel assinatura;
public AssinaturaPDF(AssinaturaModel assinaturaModel) throws KeyStoreException, UnrecoverableKeyException, NoSuchAlgorithmException, IOException, CertificateException {
super(assinaturaModel.getCertInfo());
this.assinatura = assinaturaModel;
if (assinaturaModel.getTsa() != null && !assinaturaModel.getTsa().equals("")) {
setTsaUrl(assinaturaModel.getTsa());
}
}
public byte [] assina() throws Exception {
if (assinatura.getPdf() == null || assinatura.getPdf().length == 0) {
throw new Exception("pdf file null");
}
try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
PDDocument doc = Loader.loadPDF(assinatura.getPdf())) {
if (doc.isEncrypted()) {
try {
doc.setAllSecurityToBeRemoved(true);
} catch (Exception e) {
throw new Exception("pdf passwd error", e);
}
}
int accessPermissions = SigUtils.getMDPPermission(doc);
if (accessPermissions == 1)
{
throw new IllegalStateException("No changes to the document are permitted due to DocMDP transform parameters dictionary");
}
PDSignature signature = null;
PDAcroForm acroForm = doc.getDocumentCatalog().getAcroForm(null);
PDRectangle rect = null;
// TODO 签名域的位置 可能需要再计算
Rectangle2D humanRect = new Rectangle2D.Float(assinatura.getPosition().getParseX(), assinatura.getPosition().getParseY(),
assinatura.getPosition().getSignWidthFloat(), assinatura.getPosition().getSignHeightFloat());
// sign a PDF with an existing empty signature, as created by the CreateEmptySignatureForm example.
if (acroForm != null)
{
signature = findExistingSignature(acroForm, assinatura.getSignatureKey());
if (signature != null)
{
rect = acroForm.getField(assinatura.getSignatureKey()).getWidgets().get(0).getRectangle();
}
}
if (signature == null)
{
// create signature dictionary
signature = new PDSignature();
}
if (rect == null)
{
rect = createSignatureRectangle(doc, humanRect);
}
if (doc.getVersion() >= 1.5f && accessPermissions == 0)
{
SigUtils.setMDPPermission(doc, signature, 2);
}
if (acroForm != null && acroForm.getNeedAppearances())
{
// PDFBOX-3738 NeedAppearances true results in visible signature becoming invisible
// with Adobe Reader
if (acroForm.getFields().isEmpty())
{
// we can safely delete it if there are no fields
acroForm.getCOSObject().removeItem(COSName.NEED_APPEARANCES);
// note that if you've set MDP permissions, the removal of this item
// may result in Adobe Reader claiming that the document has been changed.
// and/or that field content won't be displayed properly.
// ==> decide what you prefer and adjust your code accordingly.
}
else
{
System.out.println("/NeedAppearances is set, signature may be ignored by Adobe Reader");
}
}
// default filter
signature.setFilter(PDSignature.FILTER_ADOBE_PPKLITE);
// subfilter for basic and PAdES Part 2 signatures
signature.setSubFilter(PDSignature.SUBFILTER_ADBE_PKCS7_DETACHED);
signature.setName("Name");
signature.setLocation("Location");
signature.setReason("Reason");
// the signing date, needed for valid signature
signature.setSignDate(Calendar.getInstance());
signatureOptions = new SignatureOptions();
signatureOptions.setVisualSignature(createVisualSignatureTemplate(doc, 0, rect, signature));
signatureOptions.setPage(assinatura.getPosition().getPage());
// signatureOptions.setPreferredSignatureSize(SignatureOptions.DEFAULT_SIGNATURE_SIZE * 2);
doc.addSignature(signature, this, signatureOptions);
// doc.saveIncremental(bos);
doc.saveIncremental(bos);
IOUtils.closeQuietly(signatureOptions);
doc.close();
return bos.toByteArray();
// return null;
}
}
private InputStream createVisualSignatureTemplate(PDDocument srcDoc, int pageNum,
PDRectangle rect, PDSignature signature) throws IOException
{
try (PDDocument doc = new PDDocument())
{
PDPage page = new PDPage(srcDoc.getPage(pageNum).getMediaBox());
doc.addPage(page);
PDAcroForm acroForm = new PDAcroForm(doc);
doc.getDocumentCatalog().setAcroForm(acroForm);
PDSignatureField signatureField = new PDSignatureField(acroForm);
PDAnnotationWidget widget = signatureField.getWidgets().get(0);
List
acroForm.setSignaturesExist(true);
acroForm.setAppendOnly(true);
acroForm.getCOSObject().setDirect(true);
acroFormFields.add(signatureField);
widget.setRectangle(rect);
// from PDVisualSigBuilder.createHolderForm()
PDStream stream = new PDStream(doc);
PDFormXObject form = new PDFormXObject(stream);
PDResources res = new PDResources();
form.setResources(res);
form.setFormType(1);
PDRectangle bbox = new PDRectangle(rect.getWidth(), rect.getHeight());
float height = bbox.getHeight();
Matrix initialScale = null;
switch (srcDoc.getPage(pageNum).getRotation())
{
case 90:
form.setMatrix(AffineTransform.getQuadrantRotateInstance(1));
initialScale = Matrix.getScaleInstance(bbox.getWidth() / bbox.getHeight(), bbox.getHeight() / bbox.getWidth());
height = bbox.getWidth();
break;
case 180:
form.setMatrix(AffineTransform.getQuadrantRotateInstance(2));
break;
case 270:
form.setMatrix(AffineTransform.getQuadrantRotateInstance(3));
initialScale = Matrix.getScaleInstance(bbox.getWidth() / bbox.getHeight(), bbox.getHeight() / bbox.getWidth());
height = bbox.getWidth();
break;
case 0:
default:
break;
}
form.setBBox(bbox);
// from PDVisualSigBuilder.createAppearanceDictionary()
PDAppearanceDictionary appearance = new PDAppearanceDictionary();
appearance.getCOSObject().setDirect(true);
PDAppearanceStream appearanceStream = new PDAppearanceStream(form.getCOSObject());
appearance.setNormalAppearance(appearanceStream);
widget.setAppearance(appearance);
try (PDPageContentStream cs = new PDPageContentStream(doc, appearanceStream))
{
// for 90° and 270° scale ratio of width / height
// not really sure about this
// why does scale have no effect when done in the form matrix???
if (initialScale != null)
{
cs.transform(initialScale);
}
// show background (just for debugging, to see the rect size + position)
// cs.setNonStrokingColor(Color.yellow);
// cs.addRect(-5000, -5000, 10000, 10000);
cs.fill();
if (assinatura.getSignatureImage() != null)
{
PDImageXObject img = PDImageXObject.createFromByteArray(doc,assinatura.getSignatureImage(),"test");
int imgHeight = img.getHeight();
int imgWidth = img.getWidth();
cs.saveGraphicsState();
cs.transform(Matrix.getScaleInstance(rect.getWidth()/imgWidth*1.0f,rect.getHeight()/imgHeight*1.0f));
cs.drawImage(img, 0,0);
cs.restoreGraphicsState();
}
}
// no need to set annotations and /P entry
ByteArrayOutputStream baos = new ByteArrayOutputStream();
doc.save(baos);
// FileUtils.writeByteArrayToFile(new File("C:\Users\Administrator\Desktop\tem\pdfbox\sign-t.pdf"), baos.toByteArray());
return new ByteArrayInputStream(baos.toByteArray());
}
}
private PDRectangle createSignatureRectangle(PDDocument doc, Rectangle2D humanRect)
{
float x = (float) humanRect.getX();
float y = (float) humanRect.getY();
float width = (float) humanRect.getWidth();
float height = (float) humanRect.getHeight();
PDPage page = doc.getPage(0);
PDRectangle pageRect = page.getCropBox();
PDRectangle rect = new PDRectangle();
// signing should be at the same position regardless of page rotation.
switch (page.getRotation())
{
case 90:
rect.setLowerLeftY(x);
rect.setUpperRightY(x + width);
rect.setLowerLeftX(y);
rect.setUpperRightX(y + height);
break;
case 180:
rect.setUpperRightX(pageRect.getWidth() - x);
rect.setLowerLeftX(pageRect.getWidth() - x - width);
rect.setLowerLeftY(y);
rect.setUpperRightY(y + height);
break;
case 270:
rect.setLowerLeftY(pageRect.getHeight() - x - width);
rect.setUpperRightY(pageRect.getHeight() - x);
rect.setLowerLeftX(pageRect.getWidth() - y - height);
rect.setUpperRightX(pageRect.getWidth() - y);
break;
case 0:
default:
rect.setLowerLeftX(x);
rect.setUpperRightX(x + width);
rect.setLowerLeftY(pageRect.getHeight() - y - height);
rect.setUpperRightY(pageRect.getHeight() - y);
break;
}
return rect;
}
private PDSignature findExistingSignature(PDAcroForm acroForm, String sigFieldName)
{
PDSignature signature = null;
PDSignatureField signatureField;
if (acroForm != null)
{
signatureField = (PDSignatureField) acroForm.getField(sigFieldName);
if (signatureField != null)
{
// retrieve signature dictionary
signature = signatureField.getSignature();
if (signature == null)
{
signature = new PDSignature();
// after solving PDFBOX-3524
// signatureField.setValue(signature)
// until then:
signatureField.getCOSObject().setItem(COSName.V, signature);
}
else
{
throw new IllegalStateException("The signature field " + sigFieldName + " is already signed.");
}
}
}
return signature;
}
}
`