Merge pull request #350 from adrg/v3-a5i-pdf-sign

Digital signatures refactoring

pdf/model/appearance.go

@@ -1,50 +0,0 @@
-/*
- * This file is subject to the terms and conditions defined in
- * file 'LICENSE.md', which is part of this source code package.
- */
-
-package model
-
-import "github.com/unidoc/unidoc/pdf/core"
-
-// PdfSignatureAppearance defines a signature with a specified form field and
-// annotation widget for appearance styling.
-type PdfSignatureAppearance struct {
-	*PdfField
-	*PdfAnnotationWidget
-	
-	Signature *PdfSignature
-}
-
-// NewPdfSignatureAppearance returns an initialized signature field appearance.
-func NewPdfSignatureAppearance() *PdfSignatureAppearance {
-	app := &PdfSignatureAppearance{}
-	app.PdfField = NewPdfField()
-	app.PdfAnnotationWidget = NewPdfAnnotationWidget()
-	app.PdfField.SetContext(app)
-	app.PdfAnnotationWidget.SetContext(app)
-	app.PdfAnnotationWidget.container = app.PdfField.container
-	return app
-}
-
-// ToPdfObject implements interface PdfModel.
-func (app *PdfSignatureAppearance) ToPdfObject() core.PdfObject {
-	if app.Signature != nil {
-		app.V = app.Signature.ToPdfObject()
-	}
-	app.PdfAnnotation.ToPdfObject()
-	app.PdfField.ToPdfObject()
-
-	container := app.container
-	d := container.PdfObject.(*core.PdfObjectDictionary)
-
-	d.SetIfNotNil("Subtype", core.MakeName("Widget"))
-	d.SetIfNotNil("H", app.H)
-	d.SetIfNotNil("MK", app.MK)
-	d.SetIfNotNil("A", app.A)
-	d.SetIfNotNil("AA", app.PdfAnnotationWidget.AA)
-	d.SetIfNotNil("BS", app.BS)
-	d.SetIfNotNil("Parent", app.PdfAnnotationWidget.Parent)
-
-	return container
-}

pdf/model/appender.go

@@ -13,7 +13,6 @@ import (
 	"os"
 	"strconv"
 	"strings"
-	"time"
 
 	"github.com/unidoc/unidoc/common"
 	"github.com/unidoc/unidoc/pdf/core"
@@ -381,62 +380,58 @@ func (a *PdfAppender) ReplacePage(pageNum int, page *PdfPage) {
 }
 
 // Sign signs a specific page with a digital signature using a specified signature handler.
-// Returns an Acroform and PdfAppearance that can be used to customize the signature appearance.
+// Returns a PdfFieldSignature that can be used to customize the signature appearance.
-func (a *PdfAppender) Sign(pageNum int, handler SignatureHandler) (acroForm *PdfAcroForm, appearance *PdfSignatureAppearance, err error) {
+func (a *PdfAppender) Sign(pageNum int, field *PdfFieldSignature) error {
-	acroForm = a.Reader.AcroForm
+	if field == nil {
+		return errors.New("signature field cannot be nil")
+	}
+
+	signature := field.V
+	if signature == nil {
+		return errors.New("field signature cannot be nil")
+	}
+
+	// Get a copy of the selected page.
+	pageIndex := pageNum - 1
+	if pageIndex < 0 || pageIndex > len(a.pages)-1 {
+		return fmt.Errorf("page %d not found", pageNum)
+	}
+	page := a.pages[pageIndex].Duplicate()
+
+	// Initialize signature.
+	if err := signature.Initialize(); err != nil {
+		return err
+	}
+	a.addNewObjects(signature.container)
+
+	// Add signature field annotations to the page annotations.
+	for _, annotation := range field.Annotations {
+		annotation.P = page.ToPdfObject()
+		page.Annotations = append(page.Annotations, annotation.PdfAnnotation)
+	}
+
+	// Add signature field to the form.
+	acroForm := a.Reader.AcroForm
 	if acroForm == nil {
 		acroForm = NewPdfAcroForm()
 	}
 
-	pageIndex := pageNum - 1
-	if pageIndex < 0 || pageIndex > len(a.pages)-1 {
-		return nil, nil, fmt.Errorf("page %d not found", pageNum)
-	}
-	page := a.pages[pageIndex].Duplicate()
-
-	// TODO add more checks before set the fields
 	acroForm.SigFlags = core.MakeInteger(3)
 	acroForm.DA = core.MakeString("/F1 0 Tf 0 g")
 	n2ResourcesFont := core.MakeDict()
 	n2ResourcesFont.Set("F1", DefaultFont().ToPdfObject())
 	acroForm.DR = NewPdfPageResources()
 	acroForm.DR.Font = n2ResourcesFont
-	sig := NewPdfSignature()
-	sig.M = core.MakeString(time.Now().Format("D:20060102150405-07'00'"))
-	//sig.M = core.MakeString("D:20150226112648Z")
-	sig.Type = core.MakeName("Sig")
-	sig.Reason = core.MakeString("Test1")
-	if err := handler.InitSignature(sig); err != nil {
-		return nil, nil, err
-	}
-	a.addNewObjects(sig.container)
 
-	appearance = NewPdfSignatureAppearance()
+	fields := append(acroForm.AllFields(), field.PdfField)
-
-	fields := append(acroForm.AllFields(), appearance.PdfField)
 	acroForm.Fields = &fields
-
-	procPage(page)
-
-	appearance.V = sig.ToPdfObject()
-	appearance.FT = core.MakeName("Sig")
-	appearance.V = sig.ToPdfObject()
-	appearance.T = core.MakeString("Signature1")
-	appearance.F = core.MakeInteger(132)
-	appearance.P = page.ToPdfObject()
-	appearance.Rect = core.MakeArray(core.MakeInteger(0), core.MakeInteger(0), core.MakeInteger(0),
-		core.MakeInteger(0))
-	appearance.Signature = sig
-
-	// Add the signature appearance to the page annotations.
-	page.Annotations = append(page.Annotations, appearance.PdfAnnotationWidget.PdfAnnotation)
-
-	a.pages[pageIndex] = page
-
-	// Update acroform.
 	a.ReplaceAcroForm(acroForm)
 
-	return acroForm, appearance, nil
+	// Replace original page.
+	procPage(page)
+	a.pages[pageIndex] = page
+
+	return nil
 }
 
 // ReplaceAcroForm replaces the acrobat form. It appends a new form to the Pdf which

pdf/model/appender_test.go

@@ -13,6 +13,7 @@ import (
 	"os"
 	"path/filepath"
 	"testing"
+	"time"
 
 	"golang.org/x/crypto/pkcs12"
 
@@ -447,15 +448,33 @@ func TestAppenderSignPage4(t *testing.T) {
 		t.Errorf("Fail: %v\n", err)
 		return
 	}
-	_, appearance, err := appender.Sign(1, handler)
+
-	if err != nil {
+	// Create signature field and appearance.
+	signature := model.NewPdfSignature(handler)
+	signature.SetName("Test Appender")
+	signature.SetReason("TestAppenderSignPage4")
+	signature.SetDate(time.Now(), "")
+
+	sigField := model.NewPdfFieldSignature(signature)
+	sigField.T = core.MakeString("Signature1")
+
+	widget := model.NewPdfAnnotationWidget()
+	widget.F = core.MakeInteger(132)
+	widget.Rect = core.MakeArray(
+		core.MakeInteger(0),
+		core.MakeInteger(0),
+		core.MakeInteger(0),
+		core.MakeInteger(0),
+	)
+	widget.Parent = sigField.GetContainingPdfObject()
+
+	sigField.Annotations = append(sigField.Annotations, widget)
+
+	if err = appender.Sign(1, sigField); err != nil {
 		t.Errorf("Fail: %v\n", err)
 		return
 	}
 
-	appearance.Signature.Name = core.MakeString("Test Appender")
-	appearance.Signature.Reason = core.MakeString("TestAppenderSignPage4")
-
 	err = appender.WriteToFile(tempFile("appender_sign_page_4.pdf"))
 	if err != nil {
 		t.Errorf("Fail: %v\n", err)
@@ -513,16 +532,34 @@ func TestAppenderSignMultiple(t *testing.T) {
 			f.Close()
 			return
 		}
-		_, appearance, err := appender.Sign(1, handler)
+
-		if err != nil {
+		// Create signature field and appearance.
+		signature := model.NewPdfSignature(handler)
+		signature.SetName(fmt.Sprintf("Test Appender - Round %d", i+1))
+		signature.SetReason("TestAppenderSignPage4")
+		signature.SetDate(time.Now(), "")
+
+		sigField := model.NewPdfFieldSignature(signature)
+		sigField.T = core.MakeString("Signature1")
+
+		widget := model.NewPdfAnnotationWidget()
+		widget.F = core.MakeInteger(132)
+		widget.Rect = core.MakeArray(
+			core.MakeInteger(0),
+			core.MakeInteger(0),
+			core.MakeInteger(0),
+			core.MakeInteger(0),
+		)
+		widget.Parent = sigField.GetContainingPdfObject()
+
+		sigField.Annotations = append(sigField.Annotations, widget)
+
+		if err = appender.Sign(1, sigField); err != nil {
 			t.Errorf("Fail: %v\n", err)
 			f.Close()
 			return
 		}
 
-		appearance.Signature.Name = core.MakeString(fmt.Sprintf("Test Appender - Round %d", i+1))
-		appearance.Signature.Reason = core.MakeString("TestAppenderSignPage4")
-
 		outPath := tempFile(fmt.Sprintf("appender_sign_multiple_%d.pdf", i+1))
 
 		err = appender.WriteToFile(outPath)

pdf/model/fields.go

@@ -433,28 +433,38 @@ func (ch *PdfFieldChoice) ToPdfObject() core.PdfObject {
 // the name of the signer and verifying document contents.
 type PdfFieldSignature struct {
 	*PdfField
+
 	V    *PdfSignature
 	Lock *core.PdfIndirectObject
 	SV   *core.PdfIndirectObject
 }
 
+// NewPdfFieldSignature returns an initialized signature field.
+func NewPdfFieldSignature(signature *PdfSignature) *PdfFieldSignature {
+	field := &PdfFieldSignature{
+		PdfField: NewPdfField(),
+		V:        signature,
+	}
+	field.PdfField.SetContext(field)
+	field.FT = core.MakeName("Sig")
+
+	return field
+}
+
 // ToPdfObject returns an indirect object containing the signature field dictionary.
 func (sig *PdfFieldSignature) ToPdfObject() core.PdfObject {
 	// Set general field attributes
 	sig.PdfField.ToPdfObject()
-	container := sig.container
 
 	// Handle signature field specific attributes
+	container := sig.container
+
 	d := container.PdfObject.(*core.PdfObjectDictionary)
-	d.Set("FT", core.MakeName("Sig"))
+	d.SetIfNotNil("FT", core.MakeName("Sig"))
+	d.SetIfNotNil("Lock", sig.Lock)
+	d.SetIfNotNil("SV", sig.SV)
 	if sig.V != nil {
-		d.Set("V", sig.V.ToPdfObject())
+		d.SetIfNotNil("V", sig.V.ToPdfObject())
-	}
-	if sig.Lock != nil {
-		d.Set("Lock", sig.Lock)
-	}
-	if sig.SV != nil {
-		d.Set("SV", sig.SV)
 	}
 
 	return container

pdf/model/signature.go

@@ -7,6 +7,8 @@ package model
 
 import (
 	"bytes"
+	"errors"
+	"time"
 
 	"github.com/unidoc/unidoc/common"
 	"github.com/unidoc/unidoc/pdf/core"
@@ -80,6 +82,7 @@ func (d *pdfSignDictionary) WriteString() string {
 type PdfSignature struct {
 	Handler   SignatureHandler
 	container *core.PdfIndirectObject
+
 	// Type: Sig/DocTimeStamp
 	Type         *core.PdfObjectName
 	Filter       *core.PdfObjectName
@@ -102,25 +105,20 @@ type PdfSignature struct {
 }
 
 // NewPdfSignature creates a new PdfSignature object.
-func NewPdfSignature() *PdfSignature {
+func NewPdfSignature(handler SignatureHandler) *PdfSignature {
-	sig := &PdfSignature{}
+	sig := &PdfSignature{
-	sigDict := &pdfSignDictionary{
+		Type:    core.MakeName("Sig"),
+		Handler: handler,
+	}
+
+	dict := &pdfSignDictionary{
 		PdfObjectDictionary: core.MakeDict(),
-		handler:             &sig.Handler,
+		handler:             &handler,
 		signature:           sig,
 	}
-	sig.container = core.MakeIndirectObject(sigDict)
-	return sig
-}
 
-// PdfSignatureReference represents a signature reference dictionary.
+	sig.container = core.MakeIndirectObject(dict)
-// (Table 253 - p. 477 in PDF32000_2008).
+	return sig
-type PdfSignatureReference struct {
-	// Type: SigRef
-	TransformMethod *core.PdfObjectName
-	TransformParams *core.PdfObjectDictionary
-	Data            core.PdfObject
-	DigestMethod    *core.PdfObjectName
 }
 
 // GetContainingPdfObject implements interface PdfModel.
@@ -128,6 +126,34 @@ func (sig *PdfSignature) GetContainingPdfObject() core.PdfObject {
 	return sig.container
 }
 
+// SetName sets the `Name` field of the signature.
+func (sig *PdfSignature) SetName(name string) {
+	sig.Name = core.MakeString(name)
+}
+
+// SetDate sets the `M` field of the signature.
+func (sig *PdfSignature) SetDate(date time.Time, format string) {
+	if format == "" {
+		format = "D:20060102150405-07'00'"
+	}
+
+	sig.M = core.MakeString(date.Format(format))
+}
+
+// SetReason sets the `Reason` field of the signature.
+func (sig *PdfSignature) SetReason(reason string) {
+	sig.Reason = core.MakeString(reason)
+}
+
+// Initialize initializes the PdfSignature.
+func (sig *PdfSignature) Initialize() error {
+	if sig.Handler == nil {
+		return errors.New("signature handler cannot be nil")
+	}
+
+	return sig.Handler.InitSignature(sig)
+}
+
 // ToPdfObject implements interface PdfModel.
 func (sig *PdfSignature) ToPdfObject() core.PdfObject {
 	container := sig.container
@@ -213,146 +239,3 @@ func (r *PdfReader) newPdfSignatureFromIndirect(container *core.PdfIndirectObjec
 
 	return sig, nil
 }
-
-// PdfSignatureField represents a form field that contains a digital signature.
-// (12.7.4.5 - Signature Fields p. 454 in PDF32000_2008).
-//
-// The signature form field serves two primary purposes. 1. Define the form field that will provide the
-// visual signing properties for display but may also hold information needed when the actual signing
-// takes place such as signature method. This carries information from the author of the document to the
-// software that later does signing.
-//
-// Filling in (signing) the signature field entails updating at least the V entry and usually the AP entry of the
-// associated widget annotation. (Exporting a signature field exports the T, V, AP entries)
-//
-// The annotation rectangle (Rect) in such a dictionary shall give the position of the field on its page. Signature
-// fields that are not intended to be visible shall have an annotation rectangle that has zero height and width. PDF
-// processors shall treat such signatures as not visible. PDF processors shall also treat signatures as not
-// visible if either the Hidden bit or the NoView bit of the F entry is true
-//
-// The location of a signature within a document can have a bearing on its legal meaning. For this reason,
-// signature fields shall never refer to more than one annotation.
-type PdfSignatureField struct {
-	container *core.PdfIndirectObject
-
-	V    *PdfSignature
-	Lock *core.PdfIndirectObject
-	SV   *core.PdfIndirectObject
-	Kids *core.PdfObjectArray
-}
-
-// NewPdfSignatureField prepares a PdfSignatureField from a PdfSignature.
-func NewPdfSignatureField(signature *PdfSignature) *PdfSignatureField {
-	return &PdfSignatureField{
-		V:         signature,
-		container: core.MakeIndirectObject(core.MakeDict()),
-	}
-}
-
-// ToPdfObject implements interface PdfModel.
-func (sf *PdfSignatureField) ToPdfObject() core.PdfObject {
-	container := sf.container
-	dict := container.PdfObject.(*core.PdfObjectDictionary)
-
-	// Set fields.
-	if sf.V != nil {
-		dict.Set("V", sf.V.ToPdfObject())
-	}
-
-	dict.Set("FT", core.MakeName("Sig"))
-	dict.SetIfNotNil("Lock", sf.Lock)
-	dict.SetIfNotNil("SV", sf.SV)
-	dict.SetIfNotNil("Kids", sf.Kids)
-	// Other standard fields...
-
-	return container
-}
-
-// PdfSignatureFieldLock represents signature field lock dictionary.
-// (Table 233 - p. 455 in PDF32000_2008).
-type PdfSignatureFieldLock struct {
-	Type   core.PdfObject
-	Action *core.PdfObjectName
-	Fields *core.PdfObjectArray
-	P      *core.PdfObjectInteger
-}
-
-// PdfSignatureFieldSeed represents signature field seed value dictionary.
-// (Table 234 - p. 455 in PDF32000_2008).
-type PdfSignatureFieldSeed struct {
-	container *core.PdfIndirectObject
-
-	Ff               *core.PdfObjectInteger
-	Filter           *core.PdfObjectName
-	SubFilter        *core.PdfObjectArray
-	DigestMethod     *core.PdfObjectArray
-	V                *core.PdfObjectInteger
-	Cert             core.PdfObject
-	Reasons          *core.PdfObjectArray
-	MDP              *core.PdfObjectDictionary
-	TimeStamp        *core.PdfObjectDictionary
-	LegalAttestation *core.PdfObjectArray
-	AddRevInfo       *core.PdfObjectBool
-	LockDocument     *core.PdfObjectName
-	AppearanceFilter *core.PdfObjectString
-}
-
-func (pss *PdfSignatureFieldSeed) ToPdfObject() core.PdfObject {
-	container := pss.container
-	dict := container.PdfObject.(*core.PdfObjectDictionary)
-
-	dict.SetIfNotNil("Ff", pss.Ff)
-	dict.SetIfNotNil("Filter", pss.Filter)
-	dict.SetIfNotNil("SubFilter", pss.SubFilter)
-	dict.SetIfNotNil("DigestMethod", pss.DigestMethod)
-	dict.SetIfNotNil("V", pss.V)
-	dict.SetIfNotNil("Cert", pss.Cert)
-	dict.SetIfNotNil("Reasons", pss.Reasons)
-	dict.SetIfNotNil("MDP", pss.MDP)
-	dict.SetIfNotNil("TimeStamp", pss.TimeStamp)
-	dict.SetIfNotNil("LegalAttestation", pss.LegalAttestation)
-	dict.SetIfNotNil("AddRevInfo", pss.AddRevInfo)
-	dict.SetIfNotNil("LockDocument", pss.LockDocument)
-	dict.SetIfNotNil("AppearanceFilter", pss.AppearanceFilter)
-
-	return container
-}
-
-// PdfCertificateSeed represents certificate seed value dictionary.
-// (Table 235 - p. 457 in PDF32000_2008).
-type PdfCertificateSeed struct {
-	container *core.PdfIndirectObject
-	// Type
-	Ff                            *core.PdfObjectInteger
-	Subject                       *core.PdfObjectArray
-	SignaturePolicyOID            *core.PdfObjectString
-	SignaturePolicyHashValue      *core.PdfObjectString
-	SignaturePolicyHashAlgorithm  *core.PdfObjectName
-	SignaturePolicyCommitmentType *core.PdfObjectArray
-	SubjectDN                     *core.PdfObjectArray
-	KeyUsage                      *core.PdfObjectArray
-	Issuer                        *core.PdfObjectArray
-	OID                           *core.PdfObjectArray
-	URL                           *core.PdfObjectString
-	URLType                       *core.PdfObjectName
-}
-
-func (pcs *PdfCertificateSeed) ToPdfObject() core.PdfObject {
-	container := pcs.container
-	dict := container.PdfObject.(*core.PdfObjectDictionary)
-
-	dict.SetIfNotNil("Ff", pcs.Ff)
-	dict.SetIfNotNil("Subject", pcs.Subject)
-	dict.SetIfNotNil("SignaturePolicyOID", pcs.SignaturePolicyOID)
-	dict.SetIfNotNil("SignaturePolicyHashValue", pcs.SignaturePolicyHashValue)
-	dict.SetIfNotNil("SignaturePolicyHashAlgorithm", pcs.SignaturePolicyHashAlgorithm)
-	dict.SetIfNotNil("SignaturePolicyCommitmentType", pcs.SignaturePolicyCommitmentType)
-	dict.SetIfNotNil("SubjectDN", pcs.SubjectDN)
-	dict.SetIfNotNil("KeyUsage", pcs.KeyUsage)
-	dict.SetIfNotNil("Issuer", pcs.Issuer)
-	dict.SetIfNotNil("OID", pcs.OID)
-	dict.SetIfNotNil("URL", pcs.URL)
-	dict.SetIfNotNil("URLType", pcs.URLType)
-
-	return container
-}