[UP-14] Add new examples for the DocMDP

go.mod

@@ -12,15 +12,14 @@ require (
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/sirupsen/logrus v1.8.1 // indirect
 	github.com/trimmer-io/go-xmp v1.0.0
-	github.com/unidoc/unipdf/v3 v3.31.0
+	github.com/unidoc/unipdf/v3 v3.32.0
 	github.com/wcharczuk/go-chart/v2 v2.1.0
 	golang.org/x/crypto v0.0.0-20210421170649-83a5a9bb288b
-	golang.org/x/image v0.0.0-20210220032944-ac19c3e999fb // indirect
 	golang.org/x/sys v0.0.0-20210423185535-09eb48e85fd7 // indirect
 	golang.org/x/text v0.3.6
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect
 	gopkg.in/gographics/imagick.v2 v2.6.0
 	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )
 
-go 1.13
+go 1.13

go.sum

@@ -55,11 +55,15 @@ github.com/thales-e-security/pool v0.0.2 h1:RAPs4q2EbWsTit6tpzuvTFlgFRJ3S8Evf5gt
 github.com/thales-e-security/pool v0.0.2/go.mod h1:qtpMm2+thHtqhLzTwgDBj/OuNnMpupY8mv0Phz0gjhU=
 github.com/trimmer-io/go-xmp v1.0.0 h1:zY8bolSga5kOjBAaHS6hrdxLgEoYuT875xTy0QDwZWs=
 github.com/trimmer-io/go-xmp v1.0.0/go.mod h1:Aaptr9sp1lLv7UnCAdQ+gSHZyY2miYaKmcNVj7HRBwA=
+github.com/unidoc/freetype v0.0.0-20220130190903-3efbeefd0c90 h1:Rk4easgDQslR3DK7vwtl6jYMZTF3JqZ3ceUdyT6a3UM=
+github.com/unidoc/freetype v0.0.0-20220130190903-3efbeefd0c90/go.mod h1:mJ/Q7JnqEoWtajJVrV6S1InbRv0K/fJerPB5SQs32KI=
 github.com/unidoc/pkcs7 v0.0.0-20200411230602-d883fd70d1df/go.mod h1:UEzOZUEpJfDpywVJMUT8QiugqEZC29pDq7kdIZhWCr8=
 github.com/unidoc/pkcs7 v0.1.0 h1:9bQfbWMYsIfUP8PyhTcBudOsvbLpNH0MBv4U0P/jDTE=
 github.com/unidoc/pkcs7 v0.1.0/go.mod h1:UEzOZUEpJfDpywVJMUT8QiugqEZC29pDq7kdIZhWCr8=
 github.com/unidoc/timestamp v0.0.0-20200412005513-91597fd3793a h1:RLtvUhe4DsUDl66m7MJ8OqBjq8jpWBXPK6/RKtqeTkc=
 github.com/unidoc/timestamp v0.0.0-20200412005513-91597fd3793a/go.mod h1:j+qMWZVpZFTvDey3zxUkSgPJZEX33tDgU/QIA0IzCUw=
+github.com/unidoc/unipdf/v3 v3.32.0 h1:GpQAHDFpQJatXf/iH6ryP1J0GnwPyXhIFuIS219cg1o=
+github.com/unidoc/unipdf/v3 v3.32.0/go.mod h1:OUIt+FTxVqRJl3OFuqiPTPaxPwoYUjkmqPiRRh/SfLo=
 github.com/unidoc/unitype v0.2.1 h1:x0jMn7pB/tNrjEVjy3Ukpxo++HOBQaTCXcTYFA6BH3w=
 github.com/unidoc/unitype v0.2.1/go.mod h1:mafyug7zYmDOusqa7G0dJV45qp4b6TDAN+pHN7ZUIBU=
 github.com/wcharczuk/go-chart/v2 v2.1.0 h1:tY2slqVQ6bN+yHSnDYwZebLQFkphK4WNrVwnt7CJZ2I=
@@ -69,8 +73,8 @@ golang.org/x/crypto v0.0.0-20201002170205-7f63de1d35b0/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.0.0-20210421170649-83a5a9bb288b h1:7mWr3k41Qtv8XlltBkDkl8LoP3mpSgBW8BUoxtEdbXg=
 golang.org/x/crypto v0.0.0-20210421170649-83a5a9bb288b/go.mod h1:T9bdIzuCu7OtxOm1hfPfRQxPLYneinmdGuTeoZ9dtd4=
 golang.org/x/image v0.0.0-20200927104501-e162460cd6b5/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
-golang.org/x/image v0.0.0-20210220032944-ac19c3e999fb h1:fqpd0EBDzlHRCjiphRR5Zo/RSWWQlWv34418dnEixWk=
-golang.org/x/image v0.0.0-20210220032944-ac19c3e999fb/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
+golang.org/x/image v0.0.0-20211028202545-6944b10bf410 h1:hTftEOvwiOq2+O8k2D5/Q7COC7k5Qcrgc2TFURJYnvQ=
+golang.org/x/image v0.0.0-20211028202545-6944b10bf410/go.mod h1:023OzeP/+EPmXeapQh35lcL3II3LrY8Ic+EFFKVhULM=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

signatures/pdf_sign_docmdp.go

@@ -0,0 +1,179 @@
+/*
+ * This example showcases how to sign a PDF document with the DocMDP restriction.
+ * The file is signed using a private/public key pair.
+ *
+ * $ ./pdf_sign_docmdp <INPUT_PDF_PATH> <OUTPUT_PDF_PATH>
+ */
+package main
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"fmt"
+	"log"
+	"math/big"
+	"os"
+	"time"
+
+	"github.com/unidoc/unipdf/v3/annotator"
+	"github.com/unidoc/unipdf/v3/common/license"
+	"github.com/unidoc/unipdf/v3/core"
+	"github.com/unidoc/unipdf/v3/model"
+	"github.com/unidoc/unipdf/v3/model/mdp"
+	"github.com/unidoc/unipdf/v3/model/sighandler"
+)
+
+func init() {
+	// Make sure to load your metered License API key prior to using the library.
+	// If you need a key, you can sign up and create a free one at https://cloud.unidoc.io
+	err := license.SetMeteredKey(os.Getenv(`UNIDOC_LICENSE_API_KEY`))
+	if err != nil {
+		panic(err)
+	}
+}
+
+func main() {
+	args := os.Args
+	if len(args) < 3 {
+		log.Fatalln("Usage: go run pdf_sign_docmdp INPUT_PDF_PATH OUTPUT_PDF_PATH")
+	}
+
+	inputPath := args[1]
+	outputPath := args[2]
+
+	// Read the original file.
+	f, err := os.Open(inputPath)
+	if err != nil {
+		log.Fatalf("Fail: %v\n", err)
+	}
+	defer f.Close()
+
+	pdfReader, err := model.NewPdfReader(f)
+	if err != nil {
+		log.Fatalf("Fail: %v\n", err)
+	}
+
+	totalPage, err := pdfReader.GetNumPages()
+	if err != nil {
+		log.Fatalf("Fail: %v\n", err)
+	}
+
+	// Add signature and write it to output.pdf file.
+	err = addSignature(pdfReader, totalPage, outputPath)
+	if err != nil {
+		log.Fatalf("Fail: %v\n", err)
+	}
+
+	fmt.Println("Done")
+}
+
+func addSignature(reader *model.PdfReader, pageNum int, outputPath string) error {
+	// Create appender.
+	appender, err := model.NewPdfAppender(reader)
+	if err != nil {
+		return err
+	}
+
+	// Generate key pair.
+	priv, cert, err := generateSigKeys()
+	if err != nil {
+		return err
+	}
+
+	// Create signature handler.
+	inner_handler, err := sighandler.NewAdobePKCS7Detached(priv, cert)
+	if err != nil {
+		return err
+	}
+
+	handler, err := sighandler.NewDocMDPHandler(inner_handler, mdp.FillForms)
+	if err != nil {
+		return err
+	}
+
+	// Create signature.
+	signature := model.NewPdfSignature(handler)
+	signature.SetName("Test Signature Appearance Name")
+	signature.SetReason("TestSignatureAppearance Reason")
+	signature.SetDate(time.Now(), "")
+
+	// Initialize signature.
+	if err := signature.Initialize(); err != nil {
+		return err
+	}
+
+	opts := annotator.NewSignatureFieldOpts()
+	opts.FontSize = 8
+	opts.Rect = []float64{250, 250, 325, 300}
+	opts.TextColor = model.NewPdfColorDeviceRGB(255, 0, 0)
+
+	sigField, err := annotator.NewSignatureField(
+		signature,
+		[]*annotator.SignatureLine{
+			annotator.NewSignatureLine("Name", "John Doe"),
+			annotator.NewSignatureLine("Date", "2019.03.14"),
+			annotator.NewSignatureLine("Reason", "No reason"),
+			annotator.NewSignatureLine("Location", "London"),
+			annotator.NewSignatureLine("DN", "authority2:name2"),
+		},
+		opts,
+	)
+	if err != nil {
+		return err
+	}
+
+	sigField.T = core.MakeString("New Page Signature")
+
+	if err = appender.Sign(pageNum, sigField); err != nil {
+		log.Fatalf("Fail: %v\n", err)
+	}
+
+	// Write output PDF file.
+	if err = appender.WriteToFile(outputPath); err != nil {
+		return err
+	}
+
+	log.Printf("PDF file successfully signed. Output path: %s\n", outputPath)
+
+	return nil
+}
+
+func generateSigKeys() (*rsa.PrivateKey, *x509.Certificate, error) {
+	var now = time.Now()
+
+	// Generate private key.
+	priv, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Initialize X509 certificate template.
+	template := x509.Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject: pkix.Name{
+			CommonName:   "any",
+			Organization: []string{"Test Company"},
+		},
+		NotBefore: now.Add(-time.Hour),
+		NotAfter:  now.Add(time.Hour * 24 * 365),
+
+		KeyUsage:              x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+	}
+
+	// Generate X509 certificate.
+	certData, err := x509.CreateCertificate(rand.Reader, &template, &template, priv.Public(), priv)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	cert, err := x509.ParseCertificate(certData)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return priv, cert, nil
+}