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/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2024 Apryse Group NV
    Authors: Apryse Software.

    This program is offered under a commercial and under the AGPL license.
    For commercial licensing, contact us at https://itextpdf.com/sales.  For AGPL licensing, see below.

    AGPL licensing:
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but 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
    along with this program.  If not, see .
 */
package com.itextpdf.signatures;

import com.itextpdf.bouncycastleconnector.BouncyCastleFactoryCreator;
import com.itextpdf.commons.actions.contexts.IMetaInfo;
import com.itextpdf.commons.bouncycastle.IBouncyCastleFactory;
import com.itextpdf.commons.bouncycastle.cert.ocsp.IOCSPResp;
import com.itextpdf.commons.bouncycastle.cert.ocsp.AbstractOCSPException;
import com.itextpdf.commons.bouncycastle.cert.ocsp.IBasicOCSPResp;
import com.itextpdf.commons.utils.DateTimeUtil;
import com.itextpdf.commons.utils.MessageFormatUtil;
import com.itextpdf.forms.PdfAcroForm;
import com.itextpdf.forms.fields.PdfFormCreator;
import com.itextpdf.kernel.pdf.DocumentProperties;
import com.itextpdf.kernel.pdf.PdfArray;
import com.itextpdf.kernel.pdf.PdfDictionary;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfName;
import com.itextpdf.kernel.pdf.PdfReader;
import com.itextpdf.kernel.pdf.PdfStream;
import com.itextpdf.signatures.LtvVerification.CertificateOption;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.security.GeneralSecurityException;
import java.security.cert.Certificate;
import java.security.cert.X509CRL;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Verifies the signatures in an LTV document.
 *
 * @deprecated starting from 8.0.5.
 * {@link com.itextpdf.signatures.validation.v1.SignatureValidator} should be used instead.
 */
@Deprecated
public class LtvVerifier extends RootStoreVerifier {

    private static final IBouncyCastleFactory BOUNCY_CASTLE_FACTORY = BouncyCastleFactoryCreator.getFactory();

    /** The Logger instance */
    protected static final Logger LOGGER = LoggerFactory.getLogger(LtvVerifier.class);

    /** Option to specify level of verification; signing certificate only or the entire chain. */
    protected CertificateOption option = CertificateOption.SIGNING_CERTIFICATE;
    /** Verify root. */
    protected boolean verifyRootCertificate = true;

    /** A document object for the revision that is being verified. */
    protected PdfDocument document;
    /** The fields in the revision that is being verified. */
    protected PdfAcroForm acroForm;
    /** The date the revision was signed, or null for the highest revision. */
    protected Date signDate;
    /** The signature that covers the revision. */
    protected String signatureName;
    /** The PdfPKCS7 object for the signature. */
    protected PdfPKCS7 pkcs7;
    /** Indicates if we're working with the latest revision. */
    protected boolean latestRevision = true;
    /** The document security store for the revision that is being verified */
    protected PdfDictionary dss;
    /** Security provider to use, use null for default*/
    protected String securityProviderCode = null;
    /** The meta info */
    protected IMetaInfo metaInfo;

    private SignatureUtil sgnUtil;

    /**
     * Creates a VerificationData object for a PdfReader
     *
     * @param document The document we want to verify.
     *
     * @throws GeneralSecurityException if some problem with signature or security are occurred
     */
    public LtvVerifier(PdfDocument document) throws GeneralSecurityException {
        super(null);
        initLtvVerifier(document);
    }

    /**
     * Create {@link LtvVerifier} class instance from the {@link PdfDocument} and security provider code.
     *
     * @param document {@link PdfDocument} which will be verified
     * @param securityProviderCode security provider code to read signatures
     *
     * @throws GeneralSecurityException if some problem with signature or security are occurred
     */
    public LtvVerifier(PdfDocument document, String securityProviderCode) throws GeneralSecurityException {
        super(null);
        this.securityProviderCode = securityProviderCode;
        initLtvVerifier(document);
    }

    /**
     * Sets an extra verifier.
     *
     * @param verifier the verifier to set
     */
    public void setVerifier(CertificateVerifier verifier) {
        this.verifier = verifier;
    }

    /**
     * Sets the certificate option.
     *
     * @param    option    Either CertificateOption.SIGNING_CERTIFICATE (default) or CertificateOption.WHOLE_CHAIN
     */
    public void setCertificateOption(CertificateOption option) {
        this.option = option;
    }

    /**
     * Set the verifyRootCertificate to false if you can't verify the root certificate.
     *
     * @param verifyRootCertificate false if you can't verify the root certificate, otherwise true
     */
    public void setVerifyRootCertificate(boolean verifyRootCertificate) {
        this.verifyRootCertificate = verifyRootCertificate;
    }

    /**
     * Sets the {@link IMetaInfo} that will be used during {@link PdfDocument} creation.
     *
     * @param metaInfo meta info to set
     */
    public void setEventCountingMetaInfo(IMetaInfo metaInfo) {
        this.metaInfo = metaInfo;
    }

    /**
     * Verifies all the document-level timestamps and all the signatures in the document.
     *
     * @param result a list of {@link VerificationOK} objects
     *
     * @return a list of all {@link VerificationOK} objects after verification
     *
     * @throws IOException              signals that an I/O exception has occurred
     * @throws GeneralSecurityException if some problems with signature or security occurred
     */
    public List verify(List result) throws IOException, GeneralSecurityException {
        if (result == null) {
            result = new ArrayList<>();
        }
        while (pkcs7 != null) {
            result.addAll(verifySignature());
        }
        return result;
    }

    /**
     * Verifies a document level timestamp.
     *
     * @return a list of {@link VerificationOK} objects
     *
     * @throws GeneralSecurityException if some problems with signature or security occurred
     * @throws IOException              signals that an I/O exception has occurred
     */
    public List verifySignature() throws GeneralSecurityException, IOException {
        LOGGER.info("Verifying signature.");
        List result = new ArrayList<>();
        // Get the certificate chain
        Certificate[] chain = pkcs7.getSignCertificateChain();
        verifyChain(chain);
        // how many certificates in the chain do we need to check?
        int total = 1;
        if (CertificateOption.WHOLE_CHAIN.equals(option)) {
            total = chain.length;
        }
        // loop over the certificates
        X509Certificate signCert;
        X509Certificate issuerCert;
        for (int i = 0; i < total; ) {
            // the certificate to check
            signCert = (X509Certificate) chain[i++];
            // its issuer
            issuerCert = (X509Certificate) null;
            if (i < chain.length) {
                issuerCert = (X509Certificate) chain[i];
            }
            // now lets verify the certificate
            LOGGER.info(BOUNCY_CASTLE_FACTORY.createX500Name(signCert).toString());
            List list = verify(signCert, issuerCert, signDate);
            if (list.size() == 0) {
                try {
                    signCert.verify(signCert.getPublicKey());
                    if (latestRevision && chain.length > 1) {
                        list.add(new VerificationOK(signCert, this.getClass(), "Root certificate in final revision"));
                    }
                    if (list.size() == 0 && verifyRootCertificate) {
                        throw new GeneralSecurityException();
                    } else if (chain.length > 1) {
                        list.add(new VerificationOK(signCert, this.getClass(),
                                "Root certificate passed without checking"));
                    }
                } catch (GeneralSecurityException e) {
                    throw new VerificationException(signCert, "Couldn't verify with CRL or OCSP or trusted anchor");
                }
            }
            result.addAll(list);
        }
        // go to the previous revision
        switchToPreviousRevision();
        return result;
    }

    /**
     * Checks the certificates in a certificate chain:
     * are they valid on a specific date, and
     * do they chain up correctly?
     *
     * @param chain the certificate chain
     *
     * @throws GeneralSecurityException when requested cryptographic algorithm or security provider
     *                                  is not available, if the certificate is invalid on a specific date and if the
     *                                  certificates chained up incorrectly
     */
    public void verifyChain(Certificate[] chain) throws GeneralSecurityException {
        // Loop over the certificates in the chain
        for (int i = 0; i < chain.length; i++) {
            X509Certificate cert = (X509Certificate) chain[i];
            // check if the certificate was/is valid
            cert.checkValidity(signDate);
            // check if the previous certificate was issued by this certificate
            if (i > 0) {
                chain[i - 1].verify(chain[i].getPublicKey());
            }
        }
        LOGGER.info("All certificates are valid on " + signDate.toString());
    }

    /**
     * Verifies certificates against a list of CRLs and OCSP responses.
     *
     * @param signCert   the signing certificate
     * @param issuerCert the issuer's certificate
     *
     * @return a list of VerificationOK objects.
     * The list will be empty if the certificate couldn't be verified.
     *
     * @throws GeneralSecurityException if some problems with signature or security occurred
     * @see com.itextpdf.signatures.RootStoreVerifier#verify(java.security.cert.X509Certificate,
     *         java.security.cert.X509Certificate, java.util.Date)
     */
    public List verify(X509Certificate signCert, X509Certificate issuerCert, Date signDate)
            throws GeneralSecurityException {
        // we'll verify against the rootstore (if present)
        RootStoreVerifier rootStoreVerifier = new RootStoreVerifier(verifier);
        rootStoreVerifier.setRootStore(rootStore);
        // We'll verify against a list of CRLs
        CRLVerifier crlVerifier = new CRLVerifier(rootStoreVerifier, getCRLsFromDSS());
        crlVerifier.setRootStore(rootStore);
        crlVerifier.setOnlineCheckingAllowed(latestRevision || onlineCheckingAllowed);
        // We'll verify against a list of OCSPs
        OCSPVerifier ocspVerifier = new OCSPVerifier(crlVerifier, getOCSPResponsesFromDSS());
        ocspVerifier.setRootStore(rootStore);
        ocspVerifier.setOnlineCheckingAllowed(latestRevision || onlineCheckingAllowed);
        // We verify the chain
        return ocspVerifier.verify(signCert, issuerCert, signDate);
    }

    /**
     * Switches to the previous revision.
     *
     * @throws IOException              signals that an I/O exception has occurred
     * @throws GeneralSecurityException if some problems with signature or security occurred
     */
    public void switchToPreviousRevision() throws IOException, GeneralSecurityException {
        LOGGER.info("Switching to previous revision.");
        latestRevision = false;
        dss = document.getCatalog().getPdfObject().getAsDictionary(PdfName.DSS);
        Calendar cal = pkcs7.getTimeStampDate();
        if (cal == TimestampConstants.UNDEFINED_TIMESTAMP_DATE) {
            cal = pkcs7.getSignDate();
        }
        signDate = cal.getTime();
        List names = sgnUtil.getSignatureNames();
        if (names.size() > 1) {
            signatureName = names.get(names.size() - 2);
            try (PdfReader readerTmp = new PdfReader(sgnUtil.extractRevision(signatureName))) {
                document = new PdfDocument(readerTmp, new DocumentProperties().setEventCountingMetaInfo(metaInfo));
                this.acroForm = PdfFormCreator.getAcroForm(document, true);
                this.sgnUtil = new SignatureUtil(document);
                names = sgnUtil.getSignatureNames();
                signatureName = names.get(names.size() - 1);
                pkcs7 = coversWholeDocument();
                LOGGER.info(
                        MessageFormatUtil.format("Checking {0}signature {1}", pkcs7.isTsp()
                                ? "document-level timestamp "
                                : "", signatureName));
            }
        } else {
            LOGGER.info("No signatures in revision");
            pkcs7 = null;
        }
    }

    /**
     * Gets a list of X509CRL objects from a Document Security Store.
     *
     * @return a list of CRLs
     * 
     * @throws GeneralSecurityException when requested cryptographic algorithm or security provider
     *                                  is not available
     */
    public List getCRLsFromDSS() throws GeneralSecurityException {
        List crls = new ArrayList<>();
        if (dss == null) {
            return crls;
        }
        PdfArray crlarray = dss.getAsArray(PdfName.CRLs);
        if (crlarray == null) {
            return crls;
        }
        for (int i = 0; i < crlarray.size(); i++) {
            PdfStream stream = crlarray.getAsStream(i);
            crls.add((X509CRL) SignUtils.parseCrlFromStream(new ByteArrayInputStream(stream.getBytes())));
        }
        return crls;
    }

    /**
     * Gets OCSP responses from the Document Security Store.
     *
     * @return a list of IBasicOCSPResp objects
     *
     * @throws GeneralSecurityException if OCSP response failed
     */
    public List getOCSPResponsesFromDSS() throws GeneralSecurityException {
        List ocsps = new ArrayList<>();
        if (dss == null) {
            return ocsps;
        }
        PdfArray ocsparray = dss.getAsArray(PdfName.OCSPs);
        if (ocsparray == null) {
            return ocsps;
        }
        for (int i = 0; i < ocsparray.size(); i++) {
            PdfStream stream = ocsparray.getAsStream(i);
            IOCSPResp ocspResponse;
            try {
                ocspResponse = BOUNCY_CASTLE_FACTORY.createOCSPResp(stream.getBytes());
            } catch (IOException e) {
                throw new GeneralSecurityException(e.getMessage());
            }
            if (ocspResponse.getStatus() == 0) {
                try {
                    ocsps.add(BOUNCY_CASTLE_FACTORY.createBasicOCSPResp(ocspResponse.getResponseObject()));
                } catch (AbstractOCSPException e) {
                    throw new GeneralSecurityException(e.toString());
                }
            }
        }
        return ocsps;
    }

    /**
     * Initialize {@link LtvVerifier} object by using provided document.
     * This method reads all the existing signatures and mathematically validates the last one.
     *
     * @param document {@link PdfDocument} instance to be verified
     *
     * @throws GeneralSecurityException if some problems with signature or security are occurred
     */
    protected void initLtvVerifier(PdfDocument document) throws GeneralSecurityException {
        this.document = document;
        this.acroForm = PdfFormCreator.getAcroForm(document, true);
        this.sgnUtil = new SignatureUtil(document);
        List names = sgnUtil.getSignatureNames();
        signatureName = names.get(names.size() - 1);
        this.signDate = DateTimeUtil.getCurrentTimeDate();
        pkcs7 = coversWholeDocument();
        LOGGER.info(
                MessageFormatUtil.format(
                        "Checking {0}signature {1}", pkcs7.isTsp()
                                ? "document-level timestamp "
                                : "",
                        signatureName));
    }

    /**
     * Checks if the signature covers the whole document
     * and throws an exception if the document was altered
     *
     * @return a PdfPKCS7 object
     *
     * @throws GeneralSecurityException if some problems with signature or security occurred
     */
    protected PdfPKCS7 coversWholeDocument() throws GeneralSecurityException {
        PdfPKCS7 pkcs7 = sgnUtil.readSignatureData(signatureName, securityProviderCode);
        if (sgnUtil.signatureCoversWholeDocument(signatureName)) {
            LOGGER.info("The timestamp covers whole document.");
        } else {
            throw new VerificationException((Certificate) null, "Signature doesn't cover whole document.");
        }
        if (pkcs7.verifySignatureIntegrityAndAuthenticity()) {
            LOGGER.info("The signed document has not been modified.");
            return pkcs7;
        } else {
            throw new VerificationException((Certificate) null,
                    "The document was altered after the final signature was applied.");
        }
    }
}




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