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Split down into multiple functions

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This commit is contained in:
Corentin Mors
2025-05-01 10:13:39 +02:00
parent 9616146853
commit a3b23161c4
6 changed files with 147 additions and 142 deletions
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3
.devcontainer/devcontainer.json
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@@ -13,6 +13,9 @@
"extensions": ["golang.go"]
}
},
"containerEnv": {
"TMPDIR": "/workspaces/pdfsign/tmp"
},
"forwardPorts": [],
"postCreateCommand": "go mod download",
"remoteUser": "root"

1
.gitignore vendored
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@@ -6,3 +6,4 @@ testfiles/*_signed.pdf
testfiles/failed/*
pdfsign
certs/*
tmp/

227
sign/appearance.go
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@@ -8,12 +8,127 @@ import (
)
func (context *SignContext) createAppearance(rect [4]float64) ([]byte, error) {
if len(context.SignData.Signature.Info.Image) > 0 {
if len(context.SignData.Appearance.Image) > 0 {
return context.createImageAppearance(rect)
}
return context.createTextAppearance(rect)
}
// Helper functions for PDF resource components
// writeAppearanceHeader writes the header for the appearance stream.
//
// Should be closed by writeFormTypeAndLength.
func writeAppearanceHeader(buffer *bytes.Buffer, rectWidth, rectHeight float64) {
buffer.WriteString("<<\n")
buffer.WriteString(" /Type /XObject\n")
buffer.WriteString(" /Subtype /Form\n")
buffer.WriteString(fmt.Sprintf(" /BBox [0 0 %f %f]\n", rectWidth, rectHeight))
buffer.WriteString(" /Matrix [1 0 0 1 0 0]\n") // No scaling or translation
}
func createFontResource(buffer *bytes.Buffer) {
buffer.WriteString(" /Font <<\n")
buffer.WriteString(" /F1 <<\n")
buffer.WriteString(" /Type /Font\n")
buffer.WriteString(" /Subtype /Type1\n")
buffer.WriteString(" /BaseFont /Times-Roman\n")
buffer.WriteString(" >>\n")
buffer.WriteString(" >>\n")
}
func createImageResource(buffer *bytes.Buffer, imageObjectId uint32) {
buffer.WriteString(" /XObject <<\n")
buffer.WriteString(fmt.Sprintf(" /Im1 %d 0 R\n", imageObjectId))
buffer.WriteString(" >>\n")
}
func writeFormTypeAndLength(buffer *bytes.Buffer, streamLength int) {
buffer.WriteString(" /FormType 1\n")
buffer.WriteString(fmt.Sprintf(" /Length %d\n", streamLength))
buffer.WriteString(">>\n")
}
func writeBufferStream(buffer *bytes.Buffer, stream []byte) {
buffer.WriteString("stream\n")
buffer.Write(stream)
buffer.WriteString("endstream\n")
}
func (context *SignContext) createImageXObject() ([]byte, error) {
imageData := context.SignData.Appearance.Image
// Read image configuration to get original dimensions
img, _, err := image.DecodeConfig(bytes.NewReader(imageData))
if err != nil {
return nil, fmt.Errorf("failed to decode image configuration: %w", err)
}
// Use original image dimensions
width := float64(img.Width)
height := float64(img.Height)
// Create basic PDF Image XObject
var imageObject bytes.Buffer
imageObject.WriteString("<<\n")
imageObject.WriteString(" /Type /XObject\n")
imageObject.WriteString(" /Subtype /Image\n")
imageObject.WriteString(fmt.Sprintf(" /Width %.0f\n", width))
imageObject.WriteString(fmt.Sprintf(" /Height %.0f\n", height))
imageObject.WriteString(" /ColorSpace /DeviceRGB\n")
imageObject.WriteString(" /BitsPerComponent 8\n")
imageObject.WriteString(" /Filter /DCTDecode\n")
imageObject.WriteString(fmt.Sprintf(" /Length %d\n", len(imageData)))
imageObject.WriteString(">>\n")
imageObject.WriteString("stream\n")
imageObject.Write(imageData)
imageObject.WriteString("\nendstream\n")
return imageObject.Bytes(), nil
}
func computeTextSizeAndPosition(text string, rectWidth, rectHeight float64) (float64, float64, float64) {
// Calculate font size
fontSize := rectHeight * 0.8 // Use most of the height for the font
textWidth := float64(len(text)) * fontSize * 0.5 // Approximate text width
if textWidth > rectWidth {
fontSize = rectWidth / (float64(len(text)) * 0.5) // Adjust font size to fit text within rect width
}
// Center text horizontally and vertically
textWidth = float64(len(text)) * fontSize * 0.5
textX := (rectWidth - textWidth) / 2
if textX < 0 {
textX = 0
}
textY := (rectHeight-fontSize)/2 + fontSize/3 // Approximate vertical centering
return fontSize, textX, textY
}
func drawText(buffer *bytes.Buffer, text string, fontSize float64, x, y float64) {
buffer.WriteString("q\n") // Save graphics state
buffer.WriteString("BT\n") // Begin text
buffer.WriteString(fmt.Sprintf("/F1 %.2f Tf\n", fontSize)) // Set font and size
buffer.WriteString(fmt.Sprintf("%.2f %.2f Td\n", x, y)) // Set text position
buffer.WriteString("0.2 0.2 0.6 rg\n") // Set font color to ballpoint-like color (RGB)
buffer.WriteString(fmt.Sprintf("%s Tj\n", pdfString(text))) // Show text
buffer.WriteString("ET\n") // End text
buffer.WriteString("Q\n") // Restore graphics state
}
func drawImage(buffer *bytes.Buffer, rectWidth, rectHeight float64) {
// We save state twice on purpose due to the cm operation
buffer.WriteString("q\n") // Save graphics state
buffer.WriteString("q\n") // Save before image transformation
buffer.WriteString(fmt.Sprintf("%.2f 0 0 %.2f 0 0 cm\n", rectWidth, rectHeight))
buffer.WriteString("/Im1 Do\n") // Draw image
buffer.WriteString("Q\n") // Restore after transformation
buffer.WriteString("Q\n") // Restore graphics state
}
func (context *SignContext) createTextAppearance(rect [4]float64) ([]byte, error) {
rectWidth := rect[2] - rect[0]
rectHeight := rect[3] - rect[1]
@@ -22,61 +137,26 @@ func (context *SignContext) createTextAppearance(rect [4]float64) ([]byte, error
return nil, fmt.Errorf("invalid rectangle dimensions: width %.2f and height %.2f must be greater than 0", rectWidth, rectHeight)
}
var appearance_stream_buffer bytes.Buffer
text := context.SignData.Signature.Info.Name
// Calculate font size
fontSize := rectHeight * 0.8 // Use most of the height for the font
textWidth := float64(len(text)) * fontSize * 0.5 // Approximate text width
if textWidth > rectWidth {
fontSize = rectWidth / (float64(len(text)) * 0.5) // Adjust font size to fit text within rect width
}
fontSize, textX, textY := computeTextSizeAndPosition(text, rectWidth, rectHeight)
appearance_stream_buffer.WriteString("q\n") // Save graphics state
appearance_stream_buffer.WriteString("BT\n") // Begin text
appearance_stream_buffer.WriteString(fmt.Sprintf("/F1 %.2f Tf\n", fontSize)) // Font and size
var appearance_stream_buffer bytes.Buffer
// Center text horizontally and vertically
textWidth = float64(len(text)) * fontSize * 0.5
textX := (rectWidth - textWidth) / 2
if textX < 0 {
textX = 0
}
textY := (rectHeight-fontSize)/2 + fontSize/3 // Approximate vertical centering
appearance_stream_buffer.WriteString(fmt.Sprintf("%.2f %.2f Td\n", textX, textY)) // Position text
appearance_stream_buffer.WriteString("0.2 0.2 0.6 rg\n") // Set font color to ballpoint-like color (RGB)
appearance_stream_buffer.WriteString(fmt.Sprintf("%s Tj\n", pdfString(text))) // Show text
appearance_stream_buffer.WriteString("ET\n") // End text
appearance_stream_buffer.WriteString("Q\n") // Restore graphics state
drawText(&appearance_stream_buffer, text, fontSize, textX, textY)
// Create the appearance XObject
var appearance_buffer bytes.Buffer
appearance_buffer.WriteString("<<\n")
appearance_buffer.WriteString(" /Type /XObject\n")
appearance_buffer.WriteString(" /Subtype /Form\n")
appearance_buffer.WriteString(fmt.Sprintf(" /BBox [0 0 %f %f]\n", rectWidth, rectHeight))
appearance_buffer.WriteString(" /Matrix [1 0 0 1 0 0]\n") // No scaling or translation
writeAppearanceHeader(&appearance_buffer, rectWidth, rectHeight)
// Resources dictionary with font
appearance_buffer.WriteString(" /Resources <<\n")
appearance_buffer.WriteString(" /Font <<\n")
appearance_buffer.WriteString(" /F1 <<\n")
appearance_buffer.WriteString(" /Type /Font\n")
appearance_buffer.WriteString(" /Subtype /Type1\n")
appearance_buffer.WriteString(" /BaseFont /Times-Roman\n")
appearance_buffer.WriteString(" >>\n")
appearance_buffer.WriteString(" >>\n")
createFontResource(&appearance_buffer)
appearance_buffer.WriteString(" >>\n")
appearance_buffer.WriteString(" /FormType 1\n")
appearance_buffer.WriteString(fmt.Sprintf(" /Length %d\n", appearance_stream_buffer.Len()))
appearance_buffer.WriteString(">>\n")
writeFormTypeAndLength(&appearance_buffer, appearance_stream_buffer.Len())
appearance_buffer.WriteString("stream\n")
appearance_buffer.Write(appearance_stream_buffer.Bytes())
appearance_buffer.WriteString("endstream\n")
writeBufferStream(&appearance_buffer, appearance_stream_buffer.Bytes())
return appearance_buffer.Bytes(), nil
}
@@ -102,71 +182,20 @@ func (context *SignContext) createImageAppearance(rect [4]float64) ([]byte, erro
var appearance_stream_buffer bytes.Buffer
// We save state twice on purpose due to the cm operation
appearance_stream_buffer.WriteString("q\n") // Save graphics state
appearance_stream_buffer.WriteString("q\n") // Save before image transformation
appearance_stream_buffer.WriteString(fmt.Sprintf("%.2f 0 0 %.2f 0 0 cm\n", rectWidth, rectHeight))
appearance_stream_buffer.WriteString("/Im1 Do\n")
appearance_stream_buffer.WriteString("Q\n") // Restore after transformation
appearance_stream_buffer.WriteString("Q\n") // Restore graphics state
drawImage(&appearance_stream_buffer, rectWidth, rectHeight)
// Create the appearance XObject
var appearance_buffer bytes.Buffer
appearance_buffer.WriteString("<<\n")
appearance_buffer.WriteString(" /Type /XObject\n")
appearance_buffer.WriteString(" /Subtype /Form\n")
appearance_buffer.WriteString(fmt.Sprintf(" /BBox [0 0 %f %f]\n", rectWidth, rectHeight))
writeAppearanceHeader(&appearance_buffer, rectWidth, rectHeight)
// Resources dictionary with XObject
appearance_buffer.WriteString(" /Resources <<\n")
appearance_buffer.WriteString(" /XObject <<\n")
appearance_buffer.WriteString(fmt.Sprintf(" /Im1 %d 0 R\n", imageObjectId))
appearance_buffer.WriteString(" >>\n")
createImageResource(&appearance_buffer, imageObjectId)
appearance_buffer.WriteString(" >>\n")
appearance_buffer.WriteString(" /FormType 1\n")
appearance_buffer.WriteString(fmt.Sprintf(" /Length %d\n", appearance_stream_buffer.Len()))
appearance_buffer.WriteString(">>\n")
writeFormTypeAndLength(&appearance_buffer, appearance_stream_buffer.Len())
appearance_buffer.WriteString("stream\n")
appearance_buffer.Write(appearance_stream_buffer.Bytes())
appearance_buffer.WriteString("endstream\n")
writeBufferStream(&appearance_buffer, appearance_stream_buffer.Bytes())
return appearance_buffer.Bytes(), nil
}
func (context *SignContext) createImageXObject() ([]byte, error) {
imageData := context.SignData.Signature.Info.Image
// Read image configuration to get original dimensions
img, _, err := image.DecodeConfig(bytes.NewReader(imageData))
if err != nil {
return nil, fmt.Errorf("failed to decode image configuration: %w", err)
}
// Use original image dimensions
width := float64(img.Width)
height := float64(img.Height)
// Create basic PDF Image XObject
var imageObject bytes.Buffer
imageObject.WriteString("<<\n")
imageObject.WriteString(" /Type /XObject\n")
imageObject.WriteString(" /Subtype /Image\n")
imageObject.WriteString(fmt.Sprintf(" /Width %.0f\n", width))
imageObject.WriteString(fmt.Sprintf(" /Height %.0f\n", height))
imageObject.WriteString(" /ColorSpace /DeviceRGB\n")
imageObject.WriteString(" /BitsPerComponent 8\n")
imageObject.WriteString(" /Filter /DCTDecode\n") // JPEG compression
imageObject.WriteString(fmt.Sprintf(" /Length %d\n", len(imageData)))
imageObject.WriteString(">>\n")
imageObject.WriteString("stream\n")
imageObject.Write(imageData)
imageObject.WriteString("\nendstream\n")
return imageObject.Bytes(), nil
}

33
sign/helpers.go
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@@ -7,7 +7,6 @@ import (
"fmt"
"io"
"math"
"os"
"strings"
"time"
@@ -196,35 +195,3 @@ func isASCII(s string) bool {
}
return true
}
// CopyFile copies a file from src to dst.
// It's a replacement for os.Rename that works across filesystems.
func CopyFile(src, dst string) error {
// Open the source file
srcFile, err := os.Open(src)
if err != nil {
return fmt.Errorf("failed to open source file: %w", err)
}
defer srcFile.Close()
// Create the destination directory if it doesn't exist
dstDir := dst[:strings.LastIndex(dst, "/")]
if err := os.MkdirAll(dstDir, 0o755); err != nil {
return fmt.Errorf("failed to create destination directory: %w", err)
}
// Create the destination file
dstFile, err := os.Create(dst)
if err != nil {
return fmt.Errorf("failed to create destination file: %w", err)
}
defer dstFile.Close()
// Copy the contents
_, err = io.Copy(dstFile, srcFile)
if err != nil {
return fmt.Errorf("failed to copy file contents: %w", err)
}
return nil
}

7
sign/sign.go
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@@ -45,12 +45,16 @@ type SignData struct {
// Appearance represents the appearance of the signature
type Appearance struct {
Visible bool
Visible bool
Page uint32
LowerLeftX float64
LowerLeftY float64
UpperRightX float64
UpperRightY float64
Image []byte // Image data to use as signature appearance
ImageAsWatermark bool // If true, the text will be drawn over the image
}
type VisualSignData struct {
@@ -93,7 +97,6 @@ type SignDataSignatureInfo struct {
Reason string
ContactInfo string
Date time.Time
Image []byte // Image data to use in signature appearance
}
type SignContext struct {

18
sign/sign_test.go
View File

@@ -80,9 +80,9 @@ func verifySignedFile(t *testing.T, tmpfile *os.File, originalFileName string) {
if err != nil {
t.Fatalf("%s: %s", tmpfile.Name(), err.Error())
destinationPath := "../testfiles/failed/" + originalFileName
if copyErr := CopyFile(tmpfile.Name(), destinationPath); copyErr != nil {
t.Errorf("Failed to copy failed test file: %s", copyErr)
err2 := os.Rename(tmpfile.Name(), "../testfiles/failed/"+originalFileName)
if err2 != nil {
t.Error(err2)
}
}
}
@@ -214,7 +214,8 @@ func TestSignPDFFileUTF8(t *testing.T) {
info, err := verify.File(tmpfile)
if err != nil {
t.Fatalf("%s: %s", tmpfile.Name(), err.Error())
if err := CopyFile(tmpfile.Name(), "../testfiles/failed/"+originalFileName); err != nil {
err := os.Rename(tmpfile.Name(), "../testfiles/failed/"+originalFileName)
if err != nil {
t.Error(err)
}
} else if len(info.Signers) == 0 {
@@ -271,7 +272,8 @@ func TestSignPDFVisible(t *testing.T) {
_, err = verify.File(tmpfile)
if err != nil {
t.Fatalf("%s: %s", tmpfile.Name(), err.Error())
if err := CopyFile(tmpfile.Name(), "../testfiles/failed/"+originalFileName); err != nil {
err := os.Rename(tmpfile.Name(), "../testfiles/failed/"+originalFileName)
if err != nil {
t.Error(err)
}
}
@@ -504,7 +506,6 @@ func TestSignPDFWithImage(t *testing.T) {
Reason: "Test with visible signature and image",
ContactInfo: "None",
Date: time.Now().Local(),
Image: signatureImage, // Use the signature image
},
CertType: ApprovalSignature,
DocMDPPerm: AllowFillingExistingFormFieldsAndSignaturesPerms,
@@ -515,6 +516,7 @@ func TestSignPDFWithImage(t *testing.T) {
LowerLeftY: 50,
UpperRightX: 600,
UpperRightY: 125,
Image: signatureImage, // Use the signature image
},
DigestAlgorithm: crypto.SHA512,
Signer: pkey,
@@ -555,7 +557,6 @@ func TestSignPDFWithTwoImages(t *testing.T) {
Reason: "First signature with image",
ContactInfo: "None",
Date: time.Now().Local(),
Image: signatureImage,
},
CertType: ApprovalSignature,
DocMDPPerm: AllowFillingExistingFormFieldsAndSignaturesPerms,
@@ -566,6 +567,7 @@ func TestSignPDFWithTwoImages(t *testing.T) {
LowerLeftY: 50,
UpperRightX: 250,
UpperRightY: 125,
Image: signatureImage,
},
DigestAlgorithm: crypto.SHA512,
Signer: pkey,
@@ -594,7 +596,6 @@ func TestSignPDFWithTwoImages(t *testing.T) {
Reason: "Second signature with image",
ContactInfo: "None",
Date: time.Now().Local(),
Image: signatureImage,
},
CertType: ApprovalSignature,
DocMDPPerm: AllowFillingExistingFormFieldsAndSignaturesPerms,
@@ -605,6 +606,7 @@ func TestSignPDFWithTwoImages(t *testing.T) {
LowerLeftY: 50,
UpperRightX: 500,
UpperRightY: 125,
Image: signatureImage,
},
DigestAlgorithm: crypto.SHA512,
Signer: pkey,