From 6b914d1698bcd1dbe52340fed23044eaff57200d Mon Sep 17 00:00:00 2001
From: tigp <24852530+tigp@users.noreply.github.com>
Date: Fri, 29 Jun 2018 18:12:49 +0200
Subject: [PATCH] WIP - use another API for signing

---
 sign.go                         |  4 ++--
 sign/pdfcatalog.go              | 19 +++++++++---------
 sign/pdfinfo_test.go            | 11 ++++++-----
 sign/pdfsignature.go            | 34 +++++++++++++++++++--------------
 sign/pdfsignature_test.go       |  4 ++--
 sign/pdfvisualsignature_test.go |  4 ++--
 sign/sign.go                    | 23 +++++++++++++++++++---
 sign/sign_test.go               | 12 ++++++------
 8 files changed, 68 insertions(+), 43 deletions(-)

diff --git a/sign.go b/sign.go
index d4b2e58..f6495f5 100644
--- a/sign.go
+++ b/sign.go
@@ -123,8 +123,8 @@ func main() {
 					ContactInfo: "Geen",
 					Date:        time.Now().Local(),
 				},
-				CertType: 2,
-				Approval: false,
+				CertType:   sign.CertificationSignature,
+				DocMDPPerm: sign.AllowFillingExistingFormFieldsAndSignatures,
 			},
 			Signer:            pkey,
 			Certificate:       cert,
diff --git a/sign/pdfcatalog.go b/sign/pdfcatalog.go
index 10f8b5b..4c79acb 100644
--- a/sign/pdfcatalog.go
+++ b/sign/pdfcatalog.go
@@ -30,24 +30,25 @@ func (context *SignContext) createCatalog() (catalog string, err error) {
 	catalog += " /AcroForm <<"
 	catalog += " /Fields [" + strconv.Itoa(int(context.VisualSignData.ObjectId)) + " 0 R]"
 
-	if !context.SignData.Signature.Approval {
+	switch context.SignData.Signature.CertType {
+	case CertificationSignature, UsageRightsSignature:
 		catalog += " /NeedAppearances false"
 	}
 
-	if context.SignData.Signature.CertType > 0 {
+	switch context.SignData.Signature.CertType {
+	case CertificationSignature:
 		catalog += " /SigFlags 3"
-	} else {
+	case UsageRightsSignature:
 		catalog += " /SigFlags 1"
 	}
 
 	catalog += " >>"
 
-	if !context.SignData.Signature.Approval {
-		if context.SignData.Signature.CertType > 0 {
-			catalog += " /Perms << /DocMDP " + strconv.Itoa(int(context.SignData.ObjectId)) + " 0 R >>"
-		} else {
-			catalog += " /Perms << /UR3 " + strconv.Itoa(int(context.SignData.ObjectId)) + " 0 R >>"
-		}
+	switch context.SignData.Signature.CertType {
+	case CertificationSignature:
+		catalog += " /Perms << /DocMDP " + strconv.Itoa(int(context.SignData.ObjectId)) + " 0 R >>"
+	case UsageRightsSignature:
+		catalog += " /Perms << /UR3 " + strconv.Itoa(int(context.SignData.ObjectId)) + " 0 R >>"
 	}
 
 	catalog += " >>"
diff --git a/sign/pdfinfo_test.go b/sign/pdfinfo_test.go
index f7b71c0..b9cb560 100644
--- a/sign/pdfinfo_test.go
+++ b/sign/pdfinfo_test.go
@@ -4,8 +4,9 @@ import (
 	"os"
 	"testing"
 
-	"bitbucket.org/digitorus/pdf"
 	"time"
+
+	"bitbucket.org/digitorus/pdf"
 )
 
 func TestCreateInfoEmpty(t *testing.T) {
@@ -37,8 +38,8 @@ func TestCreateInfoEmpty(t *testing.T) {
 				ContactInfo: "Geen",
 				Date:        time.Now().Local(),
 			},
-			CertType: 2,
-			Approval: false,
+			CertType:   CertificationSignature,
+			DocMDPPerm: AllowFillingExistingFormFieldsAndSignatures,
 		},
 	}
 
@@ -101,8 +102,8 @@ func TestCreateInfo(t *testing.T) {
 				ContactInfo: "Geen",
 				Date:        time.Now().Local(),
 			},
-			CertType: 2,
-			Approval: false,
+			CertType:   CertificationSignature,
+			DocMDPPerm: AllowFillingExistingFormFieldsAndSignatures,
 		},
 	}
 
diff --git a/sign/pdfsignature.go b/sign/pdfsignature.go
index 3ec80c0..ffe0117 100644
--- a/sign/pdfsignature.go
+++ b/sign/pdfsignature.go
@@ -49,22 +49,28 @@ func (context *SignContext) createSignaturePlaceholder() (dssd string, byte_rang
 	signature_buffer.Write(bytes.Repeat([]byte("0"), int(context.SignatureMaxLength)))
 	signature_buffer.WriteString(">")
 
-	if !context.SignData.Signature.Approval {
-		signature_buffer.WriteString(" /Reference [") // array of signature reference dictionaries
+	switch context.SignData.Signature.CertType {
+	case CertificationSignature, UsageRightsSignature:
+		signature_buffer.WriteString(" /Reference [") // start array of signature reference dictionaries
 		signature_buffer.WriteString(" << /Type /SigRef")
-		if context.SignData.Signature.CertType > 0 {
-			signature_buffer.WriteString(" /TransformMethod /DocMDP")
-			signature_buffer.WriteString(" /TransformParams <<")
-			signature_buffer.WriteString(" /Type /TransformParams")
-			signature_buffer.WriteString(" /P " + strconv.Itoa(int(context.SignData.Signature.CertType)))
-			signature_buffer.WriteString(" /V /1.2")
-		} else {
-			signature_buffer.WriteString(" /TransformMethod /UR3")
-			signature_buffer.WriteString(" /TransformParams <<")
-			signature_buffer.WriteString(" /Type /TransformParams")
-			signature_buffer.WriteString(" /V /2.2")
-		}
+	}
 
+	switch context.SignData.Signature.CertType {
+	case CertificationSignature:
+		signature_buffer.WriteString(" /TransformMethod /DocMDP")
+		signature_buffer.WriteString(" /TransformParams <<")
+		signature_buffer.WriteString(" /Type /TransformParams")
+		signature_buffer.WriteString(" /P " + strconv.Itoa(int(context.SignData.Signature.DocMDPPerm)))
+		signature_buffer.WriteString(" /V /1.2")
+	case UsageRightsSignature:
+		signature_buffer.WriteString(" /TransformMethod /UR3")
+		signature_buffer.WriteString(" /TransformParams <<")
+		signature_buffer.WriteString(" /Type /TransformParams")
+		signature_buffer.WriteString(" /V /2.2")
+	}
+
+	switch context.SignData.Signature.CertType {
+	case CertificationSignature, UsageRightsSignature:
 		signature_buffer.WriteString(" >>") // close TransformParams
 		signature_buffer.WriteString(" >>")
 		signature_buffer.WriteString(" ]") // end of reference
diff --git a/sign/pdfsignature_test.go b/sign/pdfsignature_test.go
index ba639e2..5a569f2 100644
--- a/sign/pdfsignature_test.go
+++ b/sign/pdfsignature_test.go
@@ -40,8 +40,8 @@ func TestCreateSignature(t *testing.T) {
 				ContactInfo: "Geen",
 				Date:        now,
 			},
-			CertType: 2,
-			Approval: false,
+			CertType:   CertificationSignature,
+			DocMDPPerm: AllowFillingExistingFormFieldsAndSignatures,
 		},
 	}
 
diff --git a/sign/pdfvisualsignature_test.go b/sign/pdfvisualsignature_test.go
index bca6507..f7b1b01 100644
--- a/sign/pdfvisualsignature_test.go
+++ b/sign/pdfvisualsignature_test.go
@@ -40,8 +40,8 @@ func TestVisualSignature(t *testing.T) {
 				ContactInfo: "Geen",
 				Date:        now,
 			},
-			CertType: 2,
-			Approval: false,
+			CertType:   CertificationSignature,
+			DocMDPPerm: AllowFillingExistingFormFieldsAndSignatures,
 		},
 	}
 
diff --git a/sign/sign.go b/sign/sign.go
index 45a86bc..b445197 100644
--- a/sign/sign.go
+++ b/sign/sign.go
@@ -50,11 +50,23 @@ type InfoData struct {
 }
 
 type SignDataSignature struct {
-	Approval bool
-	CertType uint
-	Info     SignDataSignatureInfo
+	CertType   uint
+	DocMDPPerm uint
+	Info       SignDataSignatureInfo
 }
 
+const (
+	ApprovalSignature = iota
+	CertificationSignature
+	UsageRightsSignature
+)
+
+const (
+	DoNotAllowAnyChangesPerms = iota + 1
+	AllowFillingExistingFormFieldsAndSignatures
+	AllowFillingExistingFormFieldsAndSignaturesAndCRUDAnnotations
+)
+
 type SignDataSignatureInfo struct {
 	Name        string
 	Location    string
@@ -137,6 +149,11 @@ func Sign(input io.ReadSeeker, output io.Writer, rdr *pdf.Reader, size int64, si
 }
 
 func (context *SignContext) SignPDF() error {
+	// set defaults
+	if context.SignData.Signature.DocMDPPerm == 0 {
+		context.SignData.Signature.DocMDPPerm = 1
+	}
+
 	context.OutputBuffer = filebuffer.New([]byte{})
 
 	// Copy old file into new file.
diff --git a/sign/sign_test.go b/sign/sign_test.go
index e1771e5..03ac50a 100644
--- a/sign/sign_test.go
+++ b/sign/sign_test.go
@@ -180,8 +180,8 @@ func TestSignPDF(t *testing.T) {
 						ContactInfo: "Geen",
 						Date:        time.Now().Local(),
 					},
-					CertType: 2,
-					Approval: false,
+					CertType:   CertificationSignature,
+					DocMDPPerm: AllowFillingExistingFormFieldsAndSignatures,
 				},
 				Signer:            pkey,
 				Certificate:       cert,
@@ -253,8 +253,8 @@ func TestSignPDFFile(t *testing.T) {
 				ContactInfo: "Geen",
 				Date:        time.Now().Local(),
 			},
-			CertType: 2,
-			Approval: false,
+			CertType:   CertificationSignature,
+			DocMDPPerm: AllowFillingExistingFormFieldsAndSignatures,
 		},
 		Signer:            pkey,
 		Certificate:       cert,
@@ -332,8 +332,8 @@ func BenchmarkSignPDF(b *testing.B) {
 					ContactInfo: "Geen",
 					Date:        time.Now().Local(),
 				},
-				CertType: 2,
-				Approval: false,
+				CertType:   CertificationSignature,
+				DocMDPPerm: AllowFillingExistingFormFieldsAndSignatures,
 			},
 			Signer:            pkey,
 			Certificate:       cert,