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Ghassan Karwchan
Ghassan Karwchan

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Parse Azure SAS token using regular expression

If you have an Azure SAS token that is not working, it is good idea to parse it and understand what permissions and values it contains.

This is a JavaScript code that uses Regular Expression to parse he SAS token, and an running example where you can try your own SAS token.

var paramNames = {
  sig: 'cryptographic signature',
  st: 'start time',
  se: 'end time',
  spr: 'protocol',
  srt: 'resource types',
  sv: 'version',
  sp: 'permissions',
  ss: 'services'

let valueLookups = {
  sp : {
     r: 'read', d: 'delete', w: 'write', l: 'list', a: 'add',
    c: 'create', u: 'update', p: 'process', f: 'filter'
  srt: {
    s: 'service', c: 'container', o: 'object'
  ss : {
    b: 'blob', f: 'file', q: 'queue', t: 'table'

let valueConvertor = (key, inputValue) => 
      valueLookups[key] ? [...inputValue].map(x => valueLookups[key][x] || x)
        : inputValue;

function parseData(sasToken) {
  let regExpressionPattern = /[?&]([a-z]*)=([^\&]*)/g;
  var parameters = [...sasToken.matchAll(regExpressionPattern)];
const finalObject = parameters.reduce((acc, row) => {
  return {...acc, [paramNames[row[1]] || row[1]]: valueConvertor(row[1], row[2])}
}, {});

var outputObject = ParseData(inputSasToken);

// The output object will be in the format
  "resource types":["service","container","object"],
  "end time":"2023-02-04T03:03:37Z",
  "start time":"2023-02-03T19:03:37Z",
  "cryptographic signature":"..jhh"

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