itextpdf-master/itext/src/test/java/com/itextpdf/text/pdf/PdfEncryptionTest.java
/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2022 iText Group NV
    Authors: iText Software.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License version 3
    as published by the Free Software Foundation with the addition of the
    following permission added to Section 15 as permitted in Section 7(a):
    FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
    ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
    OF THIRD PARTY RIGHTS
    
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    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE.
    See the GNU Affero General Public License for more details.
    You should have received a copy of the GNU Affero General Public License
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    Boston, MA, 02110-1301 USA, or download the license from the following URL:
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    of this program must display Appropriate Legal Notices, as required under
    Section 5 of the GNU Affero General Public License.
    
    In accordance with Section 7(b) of the GNU Affero General Public License,
    a covered work must retain the producer line in every PDF that is created
    or manipulated using iText.
    
    You can be released from the requirements of the license by purchasing
    a commercial license. Buying such a license is mandatory as soon as you
    develop commercial activities involving the iText software without
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 */
package com.itextpdf.text.pdf;

import com.itextpdf.testutils.CompareTool;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.security.BouncyCastleDigest;
import com.itextpdf.text.pdf.security.DigestAlgorithms;
import com.itextpdf.text.pdf.security.ExternalDigest;
import com.itextpdf.text.pdf.security.ExternalSignature;
import com.itextpdf.text.pdf.security.MakeSignature;
import com.itextpdf.text.pdf.security.PrivateKeySignature;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.junit.Before;
import org.junit.Test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.security.GeneralSecurityException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.Security;
import java.security.UnrecoverableKeyException;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;

import static junit.framework.Assert.assertNull;

public class PdfEncryptionTest {

    public static final String DEST_FOLDER = "./target/com/itextpdf/test/pdf/PdfEncryptionTest/";
    public static final String SOURCE_FOLDER = "./src/test/resources/com/itextpdf/text/pdf/PdfEncryptionTest/";

    public static byte[] ownerPassword = "ownerPassword".getBytes();

    @Before
    public void setUp() {
        new File(DEST_FOLDER).mkdirs();
    }

    @Test
    public void encryptAES256() throws IOException, DocumentException, InterruptedException {
        String outPdf = DEST_FOLDER + "AES256Encrypted.pdf";
        String cmpPdf = SOURCE_FOLDER + "cmp_AES256Encrypted.pdf";
        Document doc = new Document();
        PdfWriter pdfWriter = PdfWriter.getInstance(doc, new FileOutputStream(outPdf));
//        byte[] userPassword = "userPassword".getBytes();
        byte[] userPassword = null;
        pdfWriter.setEncryption(userPassword, ownerPassword, -1852, PdfWriter.ENCRYPTION_AES_256);
        doc.open();
        doc.add(new Paragraph("hello encrypted world"));
        doc.close();
        pdfWriter.close();

        assertNull(new CompareTool().compareByContent(outPdf, cmpPdf, DEST_FOLDER, "diff_"));
    }

    @Test
    public void stampAES256() throws IOException, DocumentException, InterruptedException {
        String outPdf = DEST_FOLDER + "stampAES256.pdf";
        String cmpPdf = SOURCE_FOLDER + "cmp_stampAES256.pdf";
        PdfReader reader = new PdfReader(SOURCE_FOLDER + "AES256EncryptedDocument.pdf", ownerPassword);
        PdfStamper pdfStamper = new PdfStamper(reader, new FileOutputStream(outPdf));
        pdfStamper.close();

        assertNull(new CompareTool().compareByContent(outPdf, cmpPdf, DEST_FOLDER, "diff_"));

    }

    @Test
    public void unethicalStampAES256() throws IOException, DocumentException, InterruptedException {
        String outPdf = DEST_FOLDER + "unethicalStampAES256.pdf";
        String cmpPdf = SOURCE_FOLDER + "cmp_unethicalStampAES256.pdf";
        PdfReader reader = new PdfReader(SOURCE_FOLDER + "AES256EncryptedDocument.pdf");
        PdfReader.unethicalreading = true;
        PdfStamper pdfStamper = new PdfStamper(reader, new FileOutputStream(outPdf));
        pdfStamper.close();

        assertNull(new CompareTool().compareByContent(outPdf, cmpPdf, DEST_FOLDER, "diff_"));
    }

    @Test
    public void computeUserPasswordAES256() throws Exception {
        String encryptedPdf = SOURCE_FOLDER + "cmp_AES256Encrypted.pdf";
        PdfReader reader = new PdfReader(encryptedPdf, ownerPassword);
        byte[] password = reader.computeUserPassword();
        reader.close();

        assertNull(password);
    }

    @Test
    public void encryptWithCertificateAndSignTest() throws IOException, DocumentException, GeneralSecurityException {
        removeCryptographyRestrictions();
        Security.addProvider(new BouncyCastleProvider());
        String inPdf = SOURCE_FOLDER + "in.pdf";
        String outPdf = DEST_FOLDER + "encrypt_cert_signed.pdf";
        String tmpPdf = DEST_FOLDER + "encrypt_cert.pdf";

        encryptPdfWithCertificate(inPdf, tmpPdf, SOURCE_FOLDER + "test.cer");

        Certificate cert = getPublicCertificate(SOURCE_FOLDER + "test.cer");
        PrivateKey privateKey = getPrivateKey(SOURCE_FOLDER + "test.p12");
        certSign(getPublicCertificate(SOURCE_FOLDER + "test.cer"), privateKey, outPdf, new PdfReader(tmpPdf, cert, privateKey, new BouncyCastleProvider().getName()), "reason", "location");
        restoreCryptographyRestrictions();
    }

    private static void encryptPdfWithCertificate(String sourceDocument, String targetDocument, String certPath) throws IOException, DocumentException, CertificateException {
        Certificate cert = getPublicCertificate(certPath);
        Certificate[] certs = new Certificate[] {cert};
        PdfReader reader = new PdfReader(sourceDocument);
        PdfStamper st = new PdfStamper(reader, new FileOutputStream(targetDocument), '\0', false);
        int[] x = new int[1];
        x[0] = PdfWriter.ALLOW_SCREENREADERS;
        st.setEncryption(certs, x, PdfWriter.STANDARD_ENCRYPTION_40);
        st.close();
    }

    private static Certificate getPublicCertificate(String path) throws IOException, CertificateException {
        FileInputStream is = new FileInputStream(path);
        CertificateFactory cf = CertificateFactory.getInstance("X.509");
        X509Certificate cert = (X509Certificate) cf.generateCertificate(is);
        return cert;
    }

    private static PrivateKey getPrivateKey(String path) throws IOException, KeyStoreException, CertificateException, NoSuchAlgorithmException, UnrecoverableKeyException {
        KeyStore ks = KeyStore.getInstance("PKCS12");
        ks.load(new FileInputStream(path), "kspass".toCharArray());
        String alias = ks.aliases().nextElement();
        PrivateKey pk = (PrivateKey) ks.getKey(alias, "kspass".toCharArray());
        return pk;
    }

    private static void certSign(Certificate cert, PrivateKey privateKey, String destinationPath, PdfReader reader, String reason, String location) throws IOException, DocumentException, GeneralSecurityException {
        Certificate[] chain = new Certificate[] {cert};

        BouncyCastleProvider provider = new BouncyCastleProvider();
        ExternalSignature pks = new PrivateKeySignature(privateKey, DigestAlgorithms.SHA1, provider.getName());

        FileOutputStream fout = new FileOutputStream(destinationPath);
        PdfStamper stamper = PdfStamper.createSignature(reader, fout, '\0', null, true);
        PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
        appearance.setReason(reason);
        appearance.setLocation(location);
        ExternalDigest digest = new BouncyCastleDigest();
        MakeSignature.signDetached(appearance, digest, pks, chain, null, null, null, 0,
                MakeSignature.CryptoStandard.CADES);
        stamper.close();
    }

    /**
     * Due to import control restrictions by the governments of a few countries,
     * the encryption libraries shipped by default with the Java SDK restrict the
     * length, and as a result the strength, of encryption keys. Be aware that by
     * using this method we remove cryptography restrictions via reflection for
     * testing purposes.
     * <br/>
     * For more conventional way of solving this problem you need to replace the
     * default security JARs in your Java installation with the Java Cryptography
     * Extension (JCE) Unlimited Strength Jurisdiction Policy Files. These JARs
     * are available for download from http://java.oracle.com/ in eligible countries.
     */
    public static void removeCryptographyRestrictions() {
        try {
            Field field = Class.forName("javax.crypto.JceSecurity").
                    getDeclaredField("isRestricted");
            if (field.isAccessible()) {
                // unexpected case
                return;
            }

            Field modifiersField = Field.class.getDeclaredField("modifiers");
            modifiersField.setAccessible(true);
            modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
            modifiersField.setAccessible(false);

            field.setAccessible(true);
            if (field.getBoolean(null)) {
                field.set(null, java.lang.Boolean.FALSE);
            } else {
                field.setAccessible(false);
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    /**
     * By using this method we restore cryptography restrictions via reflection.
     */
    public static void restoreCryptographyRestrictions() {
        try {
            Field field = Class.forName("javax.crypto.JceSecurity").
                    getDeclaredField("isRestricted");
            if (field.isAccessible()) {
                field.set(null, java.lang.Boolean.TRUE);
                field.setAccessible(false);
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

}
