Improve Signature fields

@@ -81,11 +81,28 @@ class PdfCatalog extends PdfObjectDict {
     params['/PageMode'] = PdfName(_PdfPageModes[pageMode.index]);
 
     if (pdfDocument.sign != null) {
+      if (pdfDocument.sign!.value.hasMDP) {
         params['/Perms'] = PdfDict({
           '/DocMDP': pdfDocument.sign!.ref(),
         });
       }
 
+      final dss = PdfDict();
+      if (pdfDocument.sign!.crl.isNotEmpty) {
+        dss['/CRLs'] = PdfArray.fromObjects(pdfDocument.sign!.crl);
+      }
+      if (pdfDocument.sign!.cert.isNotEmpty) {
+        dss['/Certs'] = PdfArray.fromObjects(pdfDocument.sign!.cert);
+      }
+      if (pdfDocument.sign!.ocsp.isNotEmpty) {
+        dss['/OCSPs'] = PdfArray.fromObjects(pdfDocument.sign!.ocsp);
+      }
+
+      if (dss.values.isNotEmpty) {
+        params['/DSS'] = dss;
+      }
+    }
+
     final widgets = <PdfAnnot>[];
     for (var page in pdfDocument.pdfPageList.pages) {
       for (var annot in page.annotations) {
@@ -100,6 +117,13 @@ class PdfCatalog extends PdfObjectDict {
         '/SigFlags': PdfNum(pdfDocument.sign?.flagsValue ?? 0),
         '/Fields': PdfArray.fromObjects(widgets),
       });
+
+      // final acroForm = (params['/AcroForm'] ??= PdfDict()) as PdfDict;
+      // acroForm['/SigFlags'] = PdfNum(pdfDocument.sign?.flagsValue ?? 0);
+      // final fields = (acroForm['/Fields'] ??= PdfArray()) as PdfArray;
+      // for (final w in widgets) {
+      //   fields.add(w.ref());
+      // }
     }
   }
 }

@@ -47,7 +47,9 @@ class PdfPage extends PdfObjectDict with PdfGraphicStream {
     this.pageFormat = PdfPageFormat.standard,
     this.rotate = PdfPageRotation.none,
     int? index,
-  }) : super(pdfDocument, type: '/Page') {
+    int? objser,
+    int objgen = 0,
+  }) : super(pdfDocument, type: '/Page', objser: objser, objgen: objgen) {
     if (index != null) {
       pdfDocument.pdfPageList.pages.insert(index, this);
     } else {

@@ -14,20 +14,53 @@
  * limitations under the License.
  */
 
+import 'dart:typed_data';
+
+import 'package:pdf/src/pdf/object_stream.dart';
+
 import 'data_types.dart';
 import 'document.dart';
 import 'object.dart';
 import 'object_dict.dart';
 import 'stream.dart';
 
-enum PdfSigFlags { signaturesExist, appendOnly }
+/// Signature flags
+enum PdfSigFlags {
+  /// The document contains at least one signature field.
+
+  signaturesExist,
+
+  /// The document contains signatures that may be invalidated if the file is
+  /// saved (written) in a way that alters its previous contents, as opposed
+  /// to an incremental update.
+  appendOnly,
+}
 
 class PdfSignature extends PdfObjectDict {
   PdfSignature(
     PdfDocument pdfDocument, {
     required this.value,
     required this.flags,
-  }) : super(pdfDocument, type: '/Sig');
+    List<Uint8List>? crl,
+    List<Uint8List>? cert,
+    List<Uint8List>? ocsp,
+  }) : super(pdfDocument, type: '/Sig') {
+    if (crl != null) {
+      for (final o in crl) {
+        this.crl.add(PdfObjectStream(pdfDocument)..buf.putBytes(o));
+      }
+    }
+    if (cert != null) {
+      for (final o in cert) {
+        this.cert.add(PdfObjectStream(pdfDocument)..buf.putBytes(o));
+      }
+    }
+    if (ocsp != null) {
+      for (final o in ocsp) {
+        this.ocsp.add(PdfObjectStream(pdfDocument)..buf.putBytes(o));
+      }
+    }
+  }
 
   final Set<PdfSigFlags> flags;
 
@@ -39,7 +72,14 @@ class PdfSignature extends PdfObjectDict {
           .map<int>((PdfSigFlags e) => 1 >> e.index)
           .reduce((int a, int b) => a | b);
 
+  final crl = <PdfObjectStream>[];
+
+  final cert = <PdfObjectStream>[];
+
+  final ocsp = <PdfObjectStream>[];
+
   int? _offsetStart;
+
   int? _offsetEnd;
 
   @override
@@ -60,6 +100,9 @@ class PdfSignature extends PdfObjectDict {
 }
 
 abstract class PdfSignatureBase {
+  /// Modification detection and prevention
+  bool get hasMDP => false;
+
   void preSign(PdfObject object, PdfDict params);
 
   Future<void> sign(PdfObject object, PdfStream os, PdfDict params,

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+import 'dart:typed_data';
+
 import 'package:pdf/pdf.dart';
 import 'package:vector_math/vector_math_64.dart';
 
@@ -320,6 +322,9 @@ class Signature extends SingleChildWidget {
     this.date,
     this.color,
     this.highlighting,
+    this.crl,
+    this.cert,
+    this.ocsp,
   })  : value = value ?? crypto,
         super(child: child);
 
@@ -346,6 +351,15 @@ class Signature extends SingleChildWidget {
   /// Field highlighting
   final PdfAnnotHighlighting? highlighting;
 
+  /// Certificate revocation lists
+  final List<Uint8List>? crl;
+
+  /// Additional X509 certificates
+  final List<Uint8List>? cert;
+
+  /// Online Certificate Status Protocol
+  final List<Uint8List>? ocsp;
+
   @override
   void paint(Context context) {
     super.paint(context);
@@ -358,6 +372,9 @@ class Signature extends SingleChildWidget {
           PdfSigFlags.signaturesExist,
           if (appendOnly) PdfSigFlags.appendOnly,
         },
+        crl: crl,
+        cert: cert,
+        ocsp: ocsp,
       );
     } else {
       paintChild(context);