documenso/packages/signing/node-signpdf/dist/helpers/extractSignature.js

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true,
});
exports.default = void 0;

var _SignPdfError = _interopRequireDefault(require("../SignPdfError"));

function _interopRequireDefault(obj) {
  return obj && obj.__esModule ? obj : { default: obj };
}

const getSubstringIndex = (str, substring, n) => {
  let times = 0;
  let index = null;

  while (times < n && index !== -1) {
    index = str.indexOf(substring, index + 1);
    times += 1;
  }

  return index;
};
/**
 * Basic implementation of signature extraction.
 *
 * Really basic. Would work in the simplest of cases where there is only one signature
 * in a document and ByteRange is only used once in it.
 *
 * @param {Buffer} pdf
 * @returns {Object} {ByteRange: Number[], signature: Buffer, signedData: Buffer}
 */

const extractSignature = (pdf, signatureCount = 1) => {
  if (!(pdf instanceof Buffer)) {
    throw new _SignPdfError.default("PDF expected as Buffer.", _SignPdfError.default.TYPE_INPUT);
  } // const byteRangePos = pdf.indexOf('/ByteRange [');

  const byteRangePos = getSubstringIndex(pdf, "/ByteRange [", signatureCount);

  if (byteRangePos === -1) {
    throw new _SignPdfError.default("Failed to locate ByteRange.", _SignPdfError.default.TYPE_PARSE);
  }

  const byteRangeEnd = pdf.indexOf("]", byteRangePos);

  if (byteRangeEnd === -1) {
    throw new _SignPdfError.default(
      "Failed to locate the end of the ByteRange.",
      _SignPdfError.default.TYPE_PARSE
    );
  }

  const byteRange = pdf.slice(byteRangePos, byteRangeEnd + 1).toString();
  const matches = /\/ByteRange \[(\d+) +(\d+) +(\d+) +(\d+) *\]/.exec(byteRange);

  if (matches === null) {
    throw new _SignPdfError.default("Failed to parse the ByteRange.", _SignPdfError.default.TYPE_PARSE);
  }

  const ByteRange = matches.slice(1).map(Number);
  const signedData = Buffer.concat([
    pdf.slice(ByteRange[0], ByteRange[0] + ByteRange[1]),
    pdf.slice(ByteRange[2], ByteRange[2] + ByteRange[3]),
  ]);
  const signatureHex = pdf
    .slice(ByteRange[0] + ByteRange[1] + 1, ByteRange[2])
    .toString("binary")
    .replace(/(?:00|>)+$/, "");
  const signature = Buffer.from(signatureHex, "hex").toString("binary");
  return {
    ByteRange: matches.slice(1, 5).map(Number),
    signature,
    signedData,
  };
};

var _default = extractSignature;
exports.default = _default;