Sheets in PST Mailboxes

PST (Personal Storage Table) is a common file format for storing messages. Electronic discovery commonly involves extracting data from attached spreadsheets in e-mail messages stored in PST archives.

pst-extractor¹ is a NodeJS module designed for extracting objects from PST files. It has been used to extract spreadsheets from the Enron Corpus² and other large mailboxes.

SheetJS is a JavaScript library for reading and writing data from spreadsheets.

This demo uses pst-extractor and SheetJS to read spreadsheets. We'll explore how to load SheetJS in a NodeJS script or website, extract spreadsheets files, and generate HTML and CSV views of the underlying data.

The "Live Demo" reads PST files. Individual spreadsheets within the file can be downloaded or previewed in the browser.

Tested Deployments

This demo was last tested on 2024 March 11 against pst-extractor 1.9.0

Overview

The SheetJS NodeJS module can be imported from scripts that use pst-extractor.

Parsing PST Files

The pst-extractor module exposes a PSTFile class. The constructor requires a proper NodeJS buffer.

The following snippet reads and parses enron.pst from the local filesystem. fs.readFileSync³ accepts a filename and returns a Buffer:

const fs = require("fs"), PSTExtractor = require("pst-extractor");
const file = fs.readFileSync("enron.pst");
const pst = new (PSTExtractor.PSTFile)(file);

Walking the Tree

pst-extractor presents a tree-like structure to inspect the contents of the PST file. It is recommended to use recursive functions to walk the tree.

The following tree walker will collect all XLSX and XLS attachments:

/* walk the PST file and add all attachments to the specified array */
function walk(f,arr) {
  if(f.hasSubfolders) for(let sf of f.getSubFolders()) walk(sf,arr);
  if(f.contentCount <= 0) return;
  for(let e = f.getNextChild(); e != null; e = f.getNextChild()) {
    for(let i = 0; i < e.numberOfAttachments; ++i) {
      var a = e.getAttachment(i);
      /* XLS spreadsheet test by filename */
      if(/.xls[xmb]?$/.test(a.filename)) arr.push(a);
    }
  }
}

/* generate a list of attachments */
const files = [];
walk(pst.getRootFolder(), files);

Generating Buffers

The PSTAttachment class holds attachment metadata. To avoid loading everything in memory, the raw data is exposed as a custom stream object. Since the SheetJS read function requires data in a Buffer or Uint8Array, a helper function is used to collect the data:

/* collect data from the attachment into a "Buffer" */
function collect(file) {
  const strm = file.fileInputStream;
  const data = Buffer.alloc(strm._length.low);
  strm.readCompletely(data);
  return data;
}

/* collect data from the first attachment */
const buf0 = collect(files[0]);

Processing Attachments

Given a NodeJS Buffer, the SheetJS read method⁴ parses the data and returns a workbook object⁵. Individual worksheets can be extracted from the workbook and converted to CSV⁶ or HTML⁷.

The following example prints the contents of each worksheet in CSV form:

const XLSX = require("xlsx");

/* parse workbook and print CSV contents of each sheet */
const wb = XLSX.read(buf0);
wb.SheetNames.forEach(n => {
  const ws = wb.Sheets[n];
  const csv = XLSX.utils.sheet_to_csv(ws);
  console.log(`#### ${file.filename} ! ${n}`);
  console.log(csv);
});

Browser Caveats

The SheetJS Standalone scripts can be loaded through a SCRIPT tag.

This demo uses a special pst-extractor build for the web.

Compared to the NodeJS build, browser scripts require special Buffer wrappers. For example, the following function will fail since the library does not support ArrayBuffer objects:

async function error_fetch_and_parse_pst(url) {
  const ab = await (await fetch(url)).arrayBuffer();
  // this will throw an error
  return new (PSTExtractor.PSTFile)(ab);
}

The browser build exposes the Buffer object in the PSTExtractor global:

async function correct_fetch_and_parse_pst(url) {
  const ab = await (await fetch(url)).arrayBuffer();
  const buf = new PSTExtractor.Buffer(ab);
  return new (PSTExtractor.PSTFile)(buf);
}

Browser Build

The pst-extractor library is designed for NodeJS. Parts of the library expect a NodeJS Buffer, which does not exist in the browser. A fake Buffer can be added and exposed in a script.

pstextractor.js is loaded in the demo page.

Build instructions (click to show)

Initialize a new NodeJS project and install the dependency:

mkdir pstextract
cd pstextract
npm init -y
npm i --save [email protected]

Save the following to shim.js:

shim.js
const PSTExtractor = require("pst-extractor");
module.exports = PSTExtractor;
module.exports.Buffer = Buffer;

Build the script:

npx [email protected] -s PSTExtractor -o pstextractor.js shim.js

Demos

NodeJS

This demo will fetch a test PST and extract all embedded spreadsheets. The script can be adapted to read local PST files or pull PST files from a different URL.

The demo uses fetch and requires NodeJS 18 or later.

Initialize a new project:

mkdir sheetjs-pst
cd sheetjs-pst
npm init -y

Install the SheetJS NodeJS module and pst-extractor:

npm
pnpm
Yarn

npm i --save https://cdn.sheetjs.com/xlsx-0.20.3/xlsx-0.20.3.tgz pst-extractor

pnpm install --save https://cdn.sheetjs.com/xlsx-0.20.3/xlsx-0.20.3.tgz pst-extractor

yarn add https://cdn.sheetjs.com/xlsx-0.20.3/xlsx-0.20.3.tgz pst-extractor

Download SheetJSPST.js into project folder:

curl -LO https://docs.sheetjs.com/pst/SheetJSPST.js

Run the script:

node SheetJSPST.js

The process will fetch the test PST and extract the embedded spreadsheets. The terminal will display info on the exported files.

Lines starting with saving file show how attachments correspond to files. The following line states that the first attachment (index 0) was originally named RedRockA.xls and was saved to file0.xls on the file system:

saving file 0 |RedRockA.xls| to file0.xls

Lines starting with #### show the attachment file name and the worksheet name. The following line explains that there is a worksheet named "Oneok at 2500" in the file RedRockA.xls:

#### RedRockA.xls ! Oneok at 2500

Every other line is a CSV row from the named worksheet. For example, the first four lines of worksheet "Oneok at 2500" in RedRockA.xls are shown below:

#### RedRockA.xls ! Oneok at 2500
RED ROCK EXPANSION PROJECT,,,,,,,,
,,,,,,,,
,,REQUESTED,REQUESTED,,,,,
,,RECEIPT,DELIVERY,,,Allocation,,

Live Demo

This demo reads PST mailboxes. Due to browser limitations, PST files larger than 100 MB may crash the browser.

After parsing the PST file, the "Attachments" table will list attached XLSX and XLS spreadsheets in the file. The "preview" link will display an HTML table with the data in the spreadsheet. The "download" link will download the attachment.

The test file was based on the EDRM clean extract from the "Enron Corpus" and includes a few XLS attachments.

If the live demo shows a message

Please reload the page

please refresh the page. This is a known bug in the documentation generator.

Result

Live Editor

function SheetJSPreviewPSTSheets() {
  const [ files, setFiles ] = React.useState([]);
  const [ __html, setHTML ] = React.useState("");

  /* recursively walk PST and collect attachments */
  const walk = (f,arr) => {
    if(f.hasSubfolders) for(let sf of f.getSubFolders()) walk(sf,arr);
    if(f.contentCount <= 0) return;
    for(let e = f.getNextChild(); e != null; e = f.getNextChild()) {
      for(let i = 0; i < e.numberOfAttachments; ++i) {
        var a = e.getAttachment(i);
        /* XLS spreadsheet test by filename */
        if(/.xls[xmb]?$/.test(a.filename)) arr.push(a);
      }
    }
  }

  /* collect data from the attachment into a "Buffer" */
  const collect = (j) => {
    const strm = files[j].fileInputStream;
    const data = new PSTExtractor.Buffer(strm._length.low);
    strm.readCompletely(data);
    return data;
  }

  /* view selected attachment */
  const view = (j) => {
    const data = collect(j);

    /* parse */
    const wb = XLSX.read(data);

    /* convert first sheet to HTML */
    const ws = wb.Sheets[wb.SheetNames[0]];
    setHTML(XLSX.utils.sheet_to_html(ws));
  }

  /* process array buffer */
  const process_ab = (ab) => {
    const pst = new (PSTExtractor.PSTFile)(new PSTExtractor.Buffer(ab));
    const data = [];
    walk(pst.getRootFolder(), data);
    setFiles(data);
  };

  /* on click, fetch and process file */
  const doit = async() => {
    const ab = await (await fetch("/pst/enron.pst")).arrayBuffer();
    process_ab(ab);
  };
  const chg = async(e) => process_ab(await e.target.files[0].arrayBuffer());

  /* download selected attachment */
  const dl = (j) => {
    const a = document.createElement("a");
    a.download = files[j].filename;
    a.href = URL.createObjectURL(new Blob([collect(j)]));
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
  }

  if(typeof PSTExtractor == "undefined") return <b>Please reload the page</b>;
  return ( <>
    <p>Use the file input to select a file, or click "Use a Sample PST"</p>
    <input type="file" accept=".pst" onChange={chg}/>
    <button onClick={doit}>Use a Sample PST!</button><br/><br/>
    <table><thead><tr><th colspan="3">Attachments</th></tr></thead>
      <tbody>{files.map((f,j) => (
        <tr key={j}><th>{f.filename}</th>
          <td><a onClick={()=>view(j)}>(preview)</a></td>
          <td><a onClick={()=>dl(j)}>(download)</a></td>
        </tr>
      ))}</tbody>
    </table>
    <b>Preview of first worksheet</b><br/>
    <div dangerouslySetInnerHTML={{__html}}></div>
  </> );
}

The project has no official website. The official repository is hosted on GitHub. ↩
Extracted spreadsheets are available on GitHub ↩
See fs.readFileSync in the NodeJS documentation ↩
See read in "Reading Files" ↩
See "Workbook Object" ↩
See sheet_to_csv in "CSV and Text" ↩
See sheet_to_html in "Utilities" ↩

Overview​

Parsing PST Files​

Walking the Tree​

Generating Buffers​

Processing Attachments​

Browser Caveats​

Browser Build​

Demos​

NodeJS​

Live Demo​

Footnotes​