ZgaPdfSigner

A javascript tool to sign a pdf in web browser.
And it also can be used in Google Apps Script.

PS: ZGA is the abbreviation of my father's name.
And I use this name to hope the merits from this application will be dedicated to my parents.

About signing with TSA

This tool supports signing with a timestamp from TSA(Time Stamp Authority), but because of the CORS security restrictions in web browser, this function can only be used in Google Apps Script.

And because node-forge hasn't supported unauthenticated attributes in pkcs7 yet, so when use this function, the edited version needs to be imported.

The Dependencies

• pdf-lib
• node-forge

How to use this tool

Just import the dependencies and this tool.

<script src="https://unpkg.com/pdf-lib/dist/pdf-lib.min.js" type="text/javascript"></script>
<script src="https://unpkg.com/node-forge/dist/forge.min.js" type="text/javascript"></script>
<script src="https://github.com/zboris12/zgapdfsigner/releases/download/1.2.0/zgapdfsigner.js" type="text/javascript"></script>

Let's sign

Sign with an invisible signature.

/**
 * @param {ArrayBuffer} pdf
 * @param {ArrayBuffer} cert
 * @param {string} pwd
 * @return {Promise<Blob>}
 */
async function sign1(pdf, cert, pwd){
  /** @type {SignOption} */
  var sopt = {
    p12cert: cert,
    pwd: pwd,
  };
  var signer = new Zga.PdfSigner(sopt);
  var u8arr = await signer.sign(pdf);
  return new Blob([u8arr], {"type" : "application/pdf"});
}

Sign with a visible signature of a picture.

/**
 * @param {ArrayBuffer} pdf
 * @param {ArrayBuffer} cert
 * @param {string} pwd
 * @param {ArrayBuffer} imgdat
 * @param {string} imgtyp
 * @return {Promise<Blob>}
 */
async function sign2(pdf, cert, pwd, imgdat, imgtyp){
  /** @type {SignOption} */
  var sopt = {
    p12cert: cert,
    pwd: pwd,
    drawinf: {
      area: {
        x: 25,  // left
        y: 150, // top
        w: 60,  // width
        h: 60,  // height
      },
      imgData: imgdat,
      imgType: imgtyp,
    },
  };
  var signer = new Zga.PdfSigner(sopt);
  var u8arr = await signer.sign(pdf);
  return new Blob([u8arr], {"type" : "application/pdf"});
}

Sign with a visible signature of drawing a text.

//TODO

Use it in Google Apps Script

// Simulate setTimeout function for pdf-lib
function setTimeout(func, sleep){
  Utilities.sleep(sleep);
  func();
}
// Simulate window for node-forge
var window = globalThis;
// Load pdf-lib
eval(UrlFetchApp.fetch("https://unpkg.com/pdf-lib@1.17.1/dist/pdf-lib.min.js").getContentText());
// Load node-forge
eval(UrlFetchApp.fetch("https://github.com/zboris12/zgapdfsigner/releases/download/1.2.0/forge.min.edited.js").getContentText());
// Load ZgaPdfSigner
eval(UrlFetchApp.fetch("https://github.com/zboris12/zgapdfsigner/releases/download/1.2.0/zgapdfsigner.js").getContentText());

// Load pdf, certificate
var pdfBlob = DriveApp.getFilesByName("_test.pdf").next().getBlob();
var certBlob = DriveApp.getFilesByName("_test.pfx").next().getBlob();
// Sign the pdf
var sopt = {
  p12cert: certBlob.getBytes(),
  pwd: "some passphrase",
  signdate: "1",
};
var signer = new Zga.PdfSigner(sopt);
var u8arr = await signer.sign(pdfBlob.getBytes());
// Save the result pdf to some folder
var fld = DriveApp.getFolderById("a folder's id");
fld.createFile(Utilities.newBlob(u8arr, "application/pdf").setName("signed_test.pdf"));

Detail of SignOption

• p12cert: Array|Uint8Array|ArrayBuffer|string 👉 Certificate's data
• pwd: string 👉 The passphrase of the certificate
• reason: string 👉 (Optional) The reason for signing
• location: string 👉 (Optional) Your location
• contact: string 👉 (Optional) Your contact information
• signdate: Date|string|TsaServiceInfo 👉 (Optional)
  • When it is a Date, it means the date and time for signing.
  • When it is a string, it can be an url of TSA or an index of the preset TSA as below:
    • "1": http://ts.ssl.com
    • "2": http://timestamp.digicert.com
    • "3": http://timestamp.sectigo.com
    • "4": http://timestamp.entrust.net/TSS/RFC3161sha2TS
    • "5": http://timestamp.apple.com/ts01
    • "6": http://www.langedge.jp/tsa
    • "7": https://freetsa.org/tsr
  • When it is a TsaServiceInfo, it means a full customized information of TSA.
    • url: string 👉 The url of TSA
    • len: number 👉 (Optional) The length of signature's placeholder
• signame: string 👉 (Optional) The name of the signature
• drawinf: SignDrawInfo 👉 (Optional) Visible signature's information
  • area: SignAreaInfo 👉 The signature's drawing area
    • x: number 👉 Distance from left
    • y: number 👉 Distance from top
    • w: number 👉 Width
    • h: number 👉 Height
  • pageidx: number 👉 (Optional) The page index for drawing the signature
  • imgData: Array|Uint8Array|ArrayBuffer|string 👉 (Optional) The image's data
  • imgType: string 👉 (Optional) The image's type, only support jpg and png
  • text: string 👉 (Optional) A text drawing on signature, not implemented yet
  • fontData: PDFLib.StandardFonts|Array|Uint8Array|ArrayBuffer|string 👉 (Optional) The font's data for drawing text, not implemented yet

License

This tool is available under the MIT license.