Improve documentation of PdfPKCS7#getTimeStampDate. Make UNDEFINED_TIMESTAMP_DATE public and move to a separate class

DEVSIX-3509

Author: ars18wrw

sign/src/main/java/com/itextpdf/signatures/CRLVerifier.java

@@ -127,8 +127,9 @@ public List<VerificationOK> verify(X509Certificate signCert, X509Certificate iss
      * @throws GeneralSecurityException
      */
     public boolean verify(X509CRL crl, X509Certificate signCert, X509Certificate issuerCert, Date signDate) throws GeneralSecurityException {
-        if (crl == null || signDate == SignUtils.UNDEFINED_TIMESTAMP_DATE)
+        if (crl == null || signDate == TimestampConstants.UNDEFINED_TIMESTAMP_DATE) {
             return false;
+        }
         // We only check CRLs valid on the signing date for which the issuer matches
         if (crl.getIssuerX500Principal().equals(signCert.getIssuerX500Principal()) && signDate.before(crl.getNextUpdate())) {
             // the signing certificate may not be revoked

sign/src/main/java/com/itextpdf/signatures/LtvVerifier.java

@@ -279,8 +279,9 @@ public void switchToPreviousRevision() throws IOException, GeneralSecurityExcept
         latestRevision = false;
         dss = document.getCatalog().getPdfObject().getAsDictionary(PdfName.DSS);
         Calendar cal = pkcs7.getTimeStampDate();
-        if (cal == SignUtils.UNDEFINED_TIMESTAMP_DATE)
+        if (cal == TimestampConstants.UNDEFINED_TIMESTAMP_DATE) {
             cal = pkcs7.getSignDate();
+        }
         // TODO: get date from signature
         signDate = cal.getTime();
         List<String> names = sgnUtil.getSignatureNames();

sign/src/main/java/com/itextpdf/signatures/PdfPKCS7.java

@@ -538,10 +538,11 @@ public void setLocation(String location) {
      */
     public Calendar getSignDate() {
         Calendar dt = getTimeStampDate();
-        if (dt == SignUtils.UNDEFINED_TIMESTAMP_DATE)
+        if (dt == TimestampConstants.UNDEFINED_TIMESTAMP_DATE) {
             return this.signDate;
-        else
+        } else {
             return dt;
+        }
     }
 
     /**
@@ -1470,13 +1471,17 @@ public TimeStampToken getTimeStampToken() {
     }
 
     /**
-     * Gets the timestamp date
+     * Gets the timestamp date.
      *
-     * @return a date
+     * In case the signed document doesn't contain timestamp,
+     * {@link TimestampConstants#UNDEFINED_TIMESTAMP_DATE} will be returned.
+     *
+     * @return the timestamp date
      */
     public Calendar getTimeStampDate() {
-        if (timeStampToken == null)
-            return (Calendar) SignUtils.UNDEFINED_TIMESTAMP_DATE;
+        if (timeStampToken == null) {
+            return (Calendar) TimestampConstants.UNDEFINED_TIMESTAMP_DATE;
+        }
         return SignUtils.getTimeStampDate(timeStampToken);
     }
 

sign/src/main/java/com/itextpdf/signatures/SignUtils.java

@@ -115,8 +115,6 @@ This file is part of the iText (R) project.
 import org.bouncycastle.x509.util.StreamParsingException;
 
 final class SignUtils {
-    static final Object UNDEFINED_TIMESTAMP_DATE = null;
-
     static String getPrivateKeyAlgorithm(PrivateKey pk) {
         String algorithm = pk.getAlgorithm();
 

sign/src/main/java/com/itextpdf/signatures/TimestampConstants.java

@@ -0,0 +1,32 @@
+/*
+    This file is part of the iText (R) project.
+    Copyright (c) 1998-2020 iText Group NV
+    Authors: iText 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 <https://www.gnu.org/licenses/>.
+ */
+package com.itextpdf.signatures;
+
+public class TimestampConstants {
+
+    /**
+     * The timestamp which is returned in case the signed document doesn't contain timestamp.
+     * The constant's value is different in Java and .NET.
+     */
+    public static final Object UNDEFINED_TIMESTAMP_DATE = null;
+}