Merge pull request #343 from adrg/signature-support

Signature support refactoring

pdf/model/appearance.go

@@ -7,17 +7,17 @@ package model
 
 import "github.com/unidoc/unidoc/pdf/core"
 
-// PdfAppearance contains the common attributes of an appearance form field.
+// PdfSignatureAppearance contains the common attributes of an appearance form field.
-type PdfAppearance struct {
+type PdfSignatureAppearance struct {
 	*PdfField
 	*PdfAnnotationWidget
 	// TODO(gunnsth): Signature is not really part of an appearance.
 	Signature *PdfSignature
 }
 
-// NewPdfAppearance returns an initialized annotation widget.
+// NewPdfSignatureAppearance returns an initialized annotation widget.
-func NewPdfAppearance() *PdfAppearance {
+func NewPdfSignatureAppearance() *PdfSignatureAppearance {
-	app := &PdfAppearance{}
+	app := &PdfSignatureAppearance{}
 	app.PdfField = NewPdfField()
 	app.PdfAnnotationWidget = NewPdfAnnotationWidget()
 	app.PdfField.SetContext(app)
@@ -27,12 +27,13 @@ func NewPdfAppearance() *PdfAppearance {
 }
 
 // ToPdfObject implements interface PdfModel.
-func (app *PdfAppearance) ToPdfObject() core.PdfObject {
+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)
 

pdf/model/appender.go

@@ -382,22 +382,17 @@ 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.
-func (a *PdfAppender) Sign(pageNum int, handler SignatureHandler) (acroForm *PdfAcroForm, appearance *PdfAppearance, err error) {
+func (a *PdfAppender) Sign(pageNum int, handler SignatureHandler) (acroForm *PdfAcroForm, appearance *PdfSignatureAppearance, err error) {
 	acroForm = a.Reader.AcroForm
 	if acroForm == nil {
 		acroForm = NewPdfAcroForm()
 	}
+
 	pageIndex := pageNum - 1
-	var page *PdfPage
+	if pageIndex < 0 || pageIndex > len(a.pages)-1 {
-	for i, p := range a.pages {
-		if i == pageIndex {
-			page = p.Duplicate()
-			break
-		}
-	}
-	if page == nil {
 		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)
@@ -416,7 +411,7 @@ func (a *PdfAppender) Sign(pageNum int, handler SignatureHandler) (acroForm *Pdf
 	}
 	a.addNewObjects(sig.container)
 
-	appearance = NewPdfAppearance()
+	appearance = NewPdfSignatureAppearance()
 
 	fields := append(acroForm.AllFields(), appearance.PdfField)
 	acroForm.Fields = &fields
@@ -456,7 +451,6 @@ func (a *PdfAppender) Write(w io.Writer) error {
 	if a.written {
 		return errors.New("appender write can only be invoked once")
 	}
-	a.written = true
 
 	writer := NewPdfWriter()
 
@@ -704,6 +698,7 @@ func (a *PdfAppender) Write(w io.Writer) error {
 		}
 	}
 
+	a.written = true
 	return nil
 }
 

pdf/model/fields.go

@@ -245,46 +245,37 @@ func (f *PdfField) String() string {
 }
 
 // ToPdfObject sets the common field elements.
-// Note: Call the more field context's ToPdfObject to set both the generic and non-generic information.
+// Note: Call the more field context's ToPdfObject to set both the generic and
+// non-generic information.
 func (f *PdfField) ToPdfObject() core.PdfObject {
 	container := f.container
 	d := container.PdfObject.(*core.PdfObjectDictionary)
 
-	d.SetIfNotNil("FT", f.FT)
-	if f.Parent != nil {
-		d.Set("Parent", f.Parent.GetContainingPdfObject())
-	}
-	kids := core.MakeArray()
-	if f.Kids != nil {
 	// Create an array of the kids (fields or widgets).
+	kids := core.MakeArray()
 	for _, child := range f.Kids {
 		kids.Append(child.ToPdfObject())
 	}
-	}
-
-	if f.Annotations != nil {
 	for _, annot := range f.Annotations {
 		kids.Append(annot.GetContext().ToPdfObject())
 	}
-	}
 
-	if f.Kids != nil || f.Annotations != nil {
+	// Set fields.
+	if f.Parent != nil {
+		d.SetIfNotNil("Parent", f.Parent.GetContainingPdfObject())
+	}
+	if kids.Len() > 0 {
 		d.Set("Kids", kids)
 	}
 
+	d.SetIfNotNil("FT", f.FT)
 	d.SetIfNotNil("T", f.T)
 	d.SetIfNotNil("TU", f.TU)
 	d.SetIfNotNil("TM", f.TM)
 	d.SetIfNotNil("Ff", f.Ff)
-	if f.V != nil {
+	d.SetIfNotNil("V", f.V)
-		d.Set("V", f.V)
+	d.SetIfNotNil("DV", f.DV)
-	}
+	d.SetIfNotNil("AA", f.AA)
-	if f.DV != nil {
-		d.Set("DV", f.DV)
-	}
-	if f.AA != nil {
-		d.Set("AA", f.AA)
-	}
 
 	return container
 }

pdf/model/sighandler/sighandler_pkcs7.go

@@ -42,8 +42,8 @@ func (a *adobePKCS7Detached) InitSignature(sig *model.PdfSignature) error {
 	sig.Handler = &handler
 	sig.Filter = core.MakeName("Adobe.PPKLite")
 	sig.SubFilter = core.MakeName("adbe.pkcs7.detached")
-
 	sig.Reference = nil
+
 	digest, err := handler.NewDigest(sig)
 	if err != nil {
 		return err
@@ -73,23 +73,21 @@ func (a *adobePKCS7Detached) NewDigest(sig *model.PdfSignature) (model.Hasher, e
 // Validate validates PdfSignature.
 func (a *adobePKCS7Detached) Validate(sig *model.PdfSignature, digest model.Hasher) (model.SignatureValidationResult, error) {
 	signed := sig.Contents.Bytes()
-
-	buffer := digest.(*bytes.Buffer)
 	p7, err := pkcs7.Parse(signed)
 	if err != nil {
 		return model.SignatureValidationResult{}, err
 	}
+
+	buffer := digest.(*bytes.Buffer)
 	p7.Content = buffer.Bytes()
-	err = p7.Verify()
+	if err = p7.Verify(); err != nil {
-	if err != nil {
 		return model.SignatureValidationResult{}, err
 	}
 
-	result := model.SignatureValidationResult{
+	return model.SignatureValidationResult{
 		IsSigned:   true,
 		IsVerified: true,
-	}
+	}, nil
-	return result, nil
 }
 
 // Sign sets the Contents fields.

pdf/model/sighandler/sighandler_rsa_sha1.go

@@ -45,8 +45,8 @@ func (a *adobeX509RSASHA1) InitSignature(sig *model.PdfSignature) error {
 	//sig.Filter = core.MakeName("Adobe.PPKMS")
 	sig.SubFilter = core.MakeName("adbe.x509.rsa_sha1")
 	sig.Cert = core.MakeString(string(handler.certificate.Raw))
-
 	sig.Reference = nil
+
 	digest, err := handler.NewDigest(sig)
 	if err != nil {
 		return err

pdf/model/signature.go

@@ -140,49 +140,23 @@ func (sig *PdfSignature) ToPdfObject() core.PdfObject {
 	}
 
 	dict.Set("Type", sig.Type)
+	dict.SetIfNotNil("Filter", sig.Filter)
+	dict.SetIfNotNil("SubFilter", sig.SubFilter)
+	dict.SetIfNotNil("Contents", sig.Contents)
+	dict.SetIfNotNil("Cert", sig.Cert)
+	dict.SetIfNotNil("ByteRange", sig.ByteRange)
+	dict.SetIfNotNil("Reference", sig.Reference)
+	dict.SetIfNotNil("Changes", sig.Changes)
+	dict.SetIfNotNil("Name", sig.Name)
+	dict.SetIfNotNil("M", sig.M)
+	dict.SetIfNotNil("Reason", sig.Reason)
+	dict.SetIfNotNil("ContactInfo", sig.ContactInfo)
+	dict.SetIfNotNil("ByteRange", sig.ByteRange)
+	dict.SetIfNotNil("Contents", sig.Contents)
 
-	if sig.Filter != nil {
-		dict.Set("Filter", sig.Filter)
-	}
-	if sig.SubFilter != nil {
-		dict.Set("SubFilter", sig.SubFilter)
-	}
-	if sig.Contents != nil {
-		dict.Set("Contents", sig.Contents)
-	}
-	if sig.Cert != nil {
-		dict.Set("Cert", sig.Cert)
-	}
-	if sig.ByteRange != nil {
-		dict.Set("ByteRange", sig.ByteRange)
-	}
-	if sig.Reference != nil {
-		dict.Set("Reference", sig.Reference)
-	}
-	if sig.Changes != nil {
-		dict.Set("Changes", sig.Changes)
-	}
-	if sig.Name != nil {
-		dict.Set("Name", sig.Name)
-	}
-	if sig.M != nil {
-		dict.Set("M", sig.M)
-	}
-	if sig.Reason != nil {
-		dict.Set("Reason", sig.Reason)
-	}
-	if sig.ContactInfo != nil {
-		dict.Set("ContactInfo", sig.ContactInfo)
-	}
-	if sig.ByteRange != nil {
-		dict.Set("ByteRange", sig.ByteRange)
-	}
-	if sig.Contents != nil {
-		dict.Set("Contents", sig.Contents)
-	}
 	// NOTE: ByteRange and Contents need to be updated dynamically.
-	// TODO: Currently dynamic update is only in the appender, need to support in the PdfWriter
+	// TODO: Currently dynamic update is only in the appender, need to support
-	// too for the initial signature on document creation.
+	// in the PdfWriter too for the initial signature on document creation.
 	return container
 }
 
@@ -280,20 +254,15 @@ func (sf *PdfSignatureField) ToPdfObject() core.PdfObject {
 	container := sf.container
 	dict := container.PdfObject.(*core.PdfObjectDictionary)
 
-	dict.Set("FT", core.MakeName("Sig"))
+	// Set fields.
-
 	if sf.V != nil {
 		dict.Set("V", sf.V.ToPdfObject())
 	}
-	if sf.Lock != nil {
+
-		dict.Set("Lock", sf.Lock)
+	dict.Set("FT", core.MakeName("Sig"))
-	}
+	dict.SetIfNotNil("Lock", sf.Lock)
-	if sf.SV != nil {
+	dict.SetIfNotNil("SV", sf.SV)
-		dict.Set("SV", sf.SV)
+	dict.SetIfNotNil("Kids", sf.Kids)
-	}
-	if sf.Kids != nil {
-		dict.Set("Kids", sf.Kids)
-	}
 	// Other standard fields...
 
 	return container
@@ -332,45 +301,20 @@ func (pss *PdfSignatureFieldSeed) ToPdfObject() core.PdfObject {
 	container := pss.container
 	dict := container.PdfObject.(*core.PdfObjectDictionary)
 
-	if pss.Ff != nil {
+	dict.SetIfNotNil("Ff", pss.Ff)
-		dict.Set("Ff", pss.Ff)
+	dict.SetIfNotNil("Filter", pss.Filter)
-	}
+	dict.SetIfNotNil("SubFilter", pss.SubFilter)
-	if pss.Filter != nil {
+	dict.SetIfNotNil("DigestMethod", pss.DigestMethod)
-		dict.Set("Filter", pss.Filter)
+	dict.SetIfNotNil("V", pss.V)
-	}
+	dict.SetIfNotNil("Cert", pss.Cert)
-	if pss.SubFilter != nil {
+	dict.SetIfNotNil("Reasons", pss.Reasons)
-		dict.Set("SubFilter", pss.SubFilter)
+	dict.SetIfNotNil("MDP", pss.MDP)
-	}
+	dict.SetIfNotNil("TimeStamp", pss.TimeStamp)
-	if pss.DigestMethod != nil {
+	dict.SetIfNotNil("LegalAttestation", pss.LegalAttestation)
-		dict.Set("DigestMethod", pss.DigestMethod)
+	dict.SetIfNotNil("AddRevInfo", pss.AddRevInfo)
-	}
+	dict.SetIfNotNil("LockDocument", pss.LockDocument)
-	if pss.V != nil {
+	dict.SetIfNotNil("AppearanceFilter", pss.AppearanceFilter)
-		dict.Set("V", pss.V)
+
-	}
-	if pss.Cert != nil {
-		dict.Set("Cert", pss.Cert)
-	}
-	if pss.Reasons != nil {
-		dict.Set("Reasons", pss.Reasons)
-	}
-	if pss.MDP != nil {
-		dict.Set("MDP", pss.MDP)
-	}
-	if pss.TimeStamp != nil {
-		dict.Set("TimeStamp", pss.TimeStamp)
-	}
-	if pss.LegalAttestation != nil {
-		dict.Set("LegalAttestation", pss.LegalAttestation)
-	}
-	if pss.AddRevInfo != nil {
-		dict.Set("AddRevInfo", pss.AddRevInfo)
-	}
-	if pss.LockDocument != nil {
-		dict.Set("LockDocument", pss.LockDocument)
-	}
-	if pss.AppearanceFilter != nil {
-		dict.Set("AppearanceFilter", pss.AppearanceFilter)
-	}
 	return container
 }
 
@@ -396,41 +340,19 @@ type PdfCertificateSeed struct {
 func (pcs *PdfCertificateSeed) ToPdfObject() core.PdfObject {
 	container := pcs.container
 	dict := container.PdfObject.(*core.PdfObjectDictionary)
-	if pcs.Ff != nil {
+
-		dict.Set("Ff", pcs.Ff)
+	dict.SetIfNotNil("Ff", pcs.Ff)
-	}
+	dict.SetIfNotNil("Subject", pcs.Subject)
-	if pcs.Subject != nil {
+	dict.SetIfNotNil("SignaturePolicyOID", pcs.SignaturePolicyOID)
-		dict.Set("Subject", pcs.Subject)
+	dict.SetIfNotNil("SignaturePolicyHashValue", pcs.SignaturePolicyHashValue)
-	}
+	dict.SetIfNotNil("SignaturePolicyHashAlgorithm", pcs.SignaturePolicyHashAlgorithm)
-	if pcs.SignaturePolicyOID != nil {
+	dict.SetIfNotNil("SignaturePolicyCommitmentType", pcs.SignaturePolicyCommitmentType)
-		dict.Set("SignaturePolicyOID", pcs.SignaturePolicyOID)
+	dict.SetIfNotNil("SubjectDN", pcs.SubjectDN)
-	}
+	dict.SetIfNotNil("KeyUsage", pcs.KeyUsage)
-	if pcs.SignaturePolicyHashValue != nil {
+	dict.SetIfNotNil("Issuer", pcs.Issuer)
-		dict.Set("SignaturePolicyHashValue", pcs.SignaturePolicyHashValue)
+	dict.SetIfNotNil("OID", pcs.OID)
-	}
+	dict.SetIfNotNil("URL", pcs.URL)
-	if pcs.SignaturePolicyHashAlgorithm != nil {
+	dict.SetIfNotNil("URLType", pcs.URLType)
-		dict.Set("SignaturePolicyHashAlgorithm", pcs.SignaturePolicyHashAlgorithm)
+
-	}
-	if pcs.SignaturePolicyCommitmentType != nil {
-		dict.Set("SignaturePolicyCommitmentType", pcs.SignaturePolicyCommitmentType)
-	}
-	if pcs.SubjectDN != nil {
-		dict.Set("SubjectDN", pcs.SubjectDN)
-	}
-	if pcs.KeyUsage != nil {
-		dict.Set("KeyUsage", pcs.KeyUsage)
-	}
-	if pcs.Issuer != nil {
-		dict.Set("Issuer", pcs.Issuer)
-	}
-	if pcs.OID != nil {
-		dict.Set("OID", pcs.OID)
-	}
-	if pcs.URL != nil {
-		dict.Set("URL", pcs.URL)
-	}
-	if pcs.URLType != nil {
-		dict.Set("URLType", pcs.URLType)
-	}
 	return container
 }

pdf/model/signature_handler.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/unidoc/unidoc/common"
 	"github.com/unidoc/unidoc/pdf/core"
 )
 
@@ -104,35 +105,44 @@ func (r *PdfReader) ValidateSignatures(handlers []SignatureHandler) ([]Signature
 		field   *PdfField
 		handler SignatureHandler
 	}
-	var pairs []*sigFieldPair
 
+	var pairs []*sigFieldPair
 	for _, f := range r.AcroForm.AllFields() {
 		if f.V == nil {
 			continue
 		}
 		if d, found := core.GetDict(f.V); found {
 			if name, ok := core.GetNameVal(d.Get("Type")); ok && name == "Sig" {
-				ind, _ := core.GetIndirect(f.V) // TODO refactoring
+				ind, found := core.GetIndirect(f.V)
+				if !found {
+					common.Log.Debug("ERROR: Signature container is nil")
+					return nil, ErrTypeCheck
+				}
+
 				sig, err := r.newPdfSignatureFromIndirect(ind)
 				if err != nil {
 					return nil, err
 				}
-				pairs = append(pairs, &sigFieldPair{sig: sig, field: f})
+
-			}
+				// Search for an appropriate handler.
+				var sigHandler SignatureHandler
+				for _, handler := range handlers {
+					if handler.IsApplicable(sig) {
+						sigHandler = handler
+						break
 					}
 				}
 
-	for _, pair := range pairs {
+				pairs = append(pairs, &sigFieldPair{
-		for _, handler := range handlers {
+					sig:     sig,
-			if handler.IsApplicable(pair.sig) {
+					field:   f,
-				pair.handler = handler
+					handler: sigHandler,
-				break
+				})
 			}
 		}
 	}
 
 	var results []SignatureValidationResult
-
 	for _, pair := range pairs {
 		defaultResult := SignatureValidationResult{
 			IsSigned: true,

pdf/model/writer.go

@@ -226,9 +226,11 @@ func copyObject(obj core.PdfObject, objectToObjectCopyMap map[core.PdfObject]cor
 		objectToObjectCopyMap[obj] = &newObj
 		return &newObj
 	case *pdfSignDictionary:
-		newObj := &pdfSignDictionary{PdfObjectDictionary: MakeDict()}
+		newObj := &pdfSignDictionary{
-		newObj.handler = t.handler
+			PdfObjectDictionary: core.MakeDict(),
-		newObj.signature = t.signature
+			handler:             t.handler,
+			signature:           t.signature,
+		}
 		objectToObjectCopyMap[obj] = newObj
 		for _, key := range t.Keys() {
 			val := t.Get(key)