Tryanks/pdfsign
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Fixes and support for ApprovalSignature and TimeStampSignature

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This commit is contained in:
Paul van Brouwershaven
2024-11-14 13:00:58 +01:00
parent 0899875647
commit 7946d5266d
20 changed files with 1204 additions and 841 deletions
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69
sign/pdfxref.go
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@@ -19,10 +19,11 @@ const (
pngUpPredictor = 12
)
// writeXref writes the cross-reference table or stream based on the PDF type.
func (context *SignContext) writeXref() error {
switch context.PDFReader.XrefInformation.Type {
case "table":
return context.writeXrefTable()
return context.writeIncrXrefTable()
case "stream":
return context.writeXrefStream()
default:
@@ -33,15 +34,13 @@ func (context *SignContext) writeXref() error {
// writeXrefTable writes the cross-reference table to the output buffer.
func (context *SignContext) writeXrefTable() error {
// Seek to the start of the xref table
_, err := context.InputFile.Seek(context.PDFReader.XrefInformation.StartPos, 0)
if err != nil {
if _, err := context.InputFile.Seek(context.PDFReader.XrefInformation.StartPos, io.SeekStart); err != nil {
return fmt.Errorf("failed to seek to xref table: %w", err)
}
// Read the existing xref table
xrefContent := make([]byte, context.PDFReader.XrefInformation.Length)
_, err = context.InputFile.Read(xrefContent)
if err != nil {
if _, err := context.InputFile.Read(xrefContent); err != nil {
return fmt.Errorf("failed to read xref table: %w", err)
}
@@ -69,8 +68,7 @@ func (context *SignContext) writeXrefTable() error {
}{
{context.Filesize, "visual signature"},
{context.Filesize + context.VisualSignData.Length, "catalog"},
{context.Filesize + context.VisualSignData.Length + context.CatalogData.Length, "info"},
{context.Filesize + context.VisualSignData.Length + context.CatalogData.Length + context.InfoData.Length, "signature"},
{context.Filesize + context.VisualSignData.Length + context.CatalogData.Length, "signature"},
}
// Write new xref table
@@ -91,7 +89,7 @@ func (context *SignContext) writeXrefTable() error {
// Write new entries
for _, entry := range newEntries {
xrefLine := fmt.Sprintf("%010d 00000 n \n", entry.startPosition)
xrefLine := fmt.Sprintf("%010d 00000 n\r\n", entry.startPosition)
if _, err := context.OutputBuffer.Write([]byte(xrefLine)); err != nil {
return fmt.Errorf("failed to write new xref entry for %s: %w", entry.name, err)
}
@@ -100,6 +98,46 @@ func (context *SignContext) writeXrefTable() error {
return nil
}
// writeIncrXrefTable writes the incremental cross-reference table to the output buffer.
func (context *SignContext) writeIncrXrefTable() error {
// Seek to the start of the xref table
if _, err := context.InputFile.Seek(context.PDFReader.XrefInformation.StartPos, io.SeekStart); err != nil {
return fmt.Errorf("failed to seek to xref table: %w", err)
}
// Calculate new entries
newEntries := []struct {
objectID uint32
startPosition int64
name string
}{
{context.VisualSignData.ObjectId, context.Filesize, "visual signature"},
{context.CatalogData.ObjectId, context.Filesize + context.VisualSignData.Length, "catalog"},
{context.SignData.ObjectId, context.Filesize + context.VisualSignData.Length + context.CatalogData.Length, "signature"},
}
// Write xref header
if _, err := context.OutputBuffer.Write([]byte("xref\n")); err != nil {
return fmt.Errorf("failed to write incremental xref header: %w", err)
}
// Write xref subsection header
startXrefObj := fmt.Sprintf("%d %d\n", newEntries[0].objectID, len(newEntries))
if _, err := context.OutputBuffer.Write([]byte(startXrefObj)); err != nil {
return fmt.Errorf("failed to write starting xref object: %w", err)
}
// Write new entries
for _, entry := range newEntries {
xrefLine := fmt.Sprintf("%010d 00000 n \r\n", entry.startPosition)
if _, err := context.OutputBuffer.Write([]byte(xrefLine)); err != nil {
return fmt.Errorf("failed to write incremental xref entry for %s: %w", entry.name, err)
}
}
return nil
}
// writeXrefStream writes the cross-reference stream to the output buffer.
func (context *SignContext) writeXrefStream() error {
buffer := new(bytes.Buffer)
@@ -134,7 +172,6 @@ func writeXrefStreamEntries(buffer *bytes.Buffer, context *SignContext) error {
{context.Filesize},
{context.Filesize + context.VisualSignData.Length},
{context.Filesize + context.VisualSignData.Length + context.CatalogData.Length},
{context.Filesize + context.VisualSignData.Length + context.CatalogData.Length + context.InfoData.Length},
{context.NewXrefStart},
}
@@ -168,22 +205,20 @@ func encodeXrefStream(data []byte, predictor int64) ([]byte, error) {
// writeXrefStreamHeader writes the header for the xref stream.
func writeXrefStreamHeader(context *SignContext, streamLength int) error {
newInfo := fmt.Sprintf("Info %d 0 R", context.InfoData.ObjectId)
newRoot := fmt.Sprintf("Root %d 0 R", context.CatalogData.ObjectId)
id := context.PDFReader.Trailer().Key("ID")
id0 := hex.EncodeToString([]byte(id.Index(0).RawString()))
id1 := hex.EncodeToString([]byte(id.Index(0).RawString()))
newXref := fmt.Sprintf("%d 0 obj\n<< /Type /XRef /Length %d /Filter /FlateDecode /DecodeParms << /Columns %d /Predictor %d >> /W [ 1 3 1 ] /Prev %d /Size %d /Index [ %d 5 ] /%s /%s /ID [<%s><%s>] >>\n",
newXref := fmt.Sprintf("%d 0 obj\n<< /Type /XRef /Length %d /Filter /FlateDecode /DecodeParms << /Columns %d /Predictor %d >> /W [ 1 3 1 ] /Prev %d /Size %d /Index [ %d 4 ] /%s /ID [<%s><%s>] >>\n",
context.SignData.ObjectId+1,
streamLength,
xrefStreamColumns,
xrefStreamPredictor,
context.PDFReader.XrefInformation.StartPos,
context.PDFReader.XrefInformation.ItemCount+5,
context.PDFReader.XrefInformation.ItemCount+4,
context.PDFReader.XrefInformation.ItemCount,
newInfo,
newRoot,
id0,
id1,
@@ -210,22 +245,25 @@ func writeXrefStreamContent(context *SignContext, streamBytes []byte) error {
return nil
}
// writeXrefStreamLine writes a single line in the xref stream.
func writeXrefStreamLine(b *bytes.Buffer, xreftype byte, offset int, gen byte) {
b.WriteByte(xreftype)
b.Write(encodeInt(offset))
b.WriteByte(gen)
}
// encodeInt encodes an integer to a 3-byte slice.
func encodeInt(i int) []byte {
result := make([]byte, 4)
binary.BigEndian.PutUint32(result, uint32(i))
return result[1:4]
}
// EncodePNGSUBBytes encodes data using PNG SUB filter.
func EncodePNGSUBBytes(columns int, data []byte) ([]byte, error) {
rowCount := len(data) / columns
if len(data)%columns != 0 {
return nil, errors.New("Invalid row/column length")
return nil, errors.New("invalid row/column length")
}
buffer := bytes.NewBuffer(nil)
@@ -253,10 +291,11 @@ func EncodePNGSUBBytes(columns int, data []byte) ([]byte, error) {
return b.Bytes(), nil
}
// EncodePNGUPBytes encodes data using PNG UP filter.
func EncodePNGUPBytes(columns int, data []byte) ([]byte, error) {
rowCount := len(data) / columns
if len(data)%columns != 0 {
return nil, errors.New("Invalid row/column length")
return nil, errors.New("invalid row/column length")
}
prevRowData := make([]byte, columns)