JWT tokenize - Postman Pre-Request Script

pre-request-jwt.js

function base64url(source) {
	// Encode in classical base64
	encodedSource = CryptoJS.enc.Base64.stringify(source);

	// Remove padding equal characters
	encodedSource = encodedSource.replace(/=+$/, '');

	// Replace characters according to base64url specifications
	encodedSource = encodedSource.replace(/\+/g, '-');
	encodedSource = encodedSource.replace(/\//g, '_');

	return encodedSource;
}

function addIAT(request) {
	var iat = Math.floor(Date.now() / 1000) + 257;
	data.iat = iat;
	return data;
}


var header = {
	"typ": "JWT",
	"alg": "HS256"
};

var data = {
	"fname": "name",
	"lname": "name",
	"email": "[email protected]",
	"password": "abc123$"
};

data = addIAT(data);

var secret = 'myjwtsecret';

// encode header
var stringifiedHeader = CryptoJS.enc.Utf8.parse(JSON.stringify(header));
var encodedHeader = base64url(stringifiedHeader);

// encode data
var stringifiedData = CryptoJS.enc.Utf8.parse(JSON.stringify(data));
var encodedData = base64url(stringifiedData);

// build token
var token = encodedHeader + "." + encodedData;

// sign token
var signature = CryptoJS.HmacSHA256(token, secret);
signature = base64url(signature);
var signedToken = token + "." + signature;

postman.setEnvironmentVariable("payload", signedToken);

This was helpful. I am curious though, what is the reasoning for + 257 on line 16?

didnt work secret for google JWT

i trying RS256
this one generated by your prescript:

eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCIsImtpZCI5IjkzYzA1ZWQ2NTc4NDRiYWM1ZjBmZGFmYTFhZThjMTdlNjFiZjU4ZDAifQ
.
eyJpc2MiOiJ2YWluZ2xvcnktbG9yZS10ZXN0MkB2YWluZ2xvcnktbG9yZS5pYW0uZ3NlcnZpY2VhY2NvdW50LmNvbSIsInN1YiI6InZhaW5nbG9yeS1sb3JlLXRlc3QyQHZhaW5nbG9yeS1sb3JlLmlhbS5nc2VydmljZWFjY291bnQuY29tIiwiYXVkIjoiaHR0cHM6Ly93d3cuZ29vZ2xlYXBpcy5jb20vb2F1dGgyL3Y0L3Rva2VuIiwic2NvcGUiOiJodHRwczovL3d3dy5nb29nbGVhcGlzLmNvbS9hdXRoL2RldnN0b3JhZ2UucmVhZF9vbmx5IiwiaWF0IjoxNTUzMDk2ODc0LCJleHAiOjE1NTMxMDA0NzR9
.
ZaCoMgyjg85nlOgm_dg7ydMe5aZwdR6fj_I5VRKZT7w

and this one by jwt.io:

eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCIsImtpZCI5IjkzYzA1ZWQ2NTc4NDRiYWM1ZjBmZGFmYTFhZThjMTdlNjFiZjU4ZDAifQ
.
eyJpc2MiOiJ2YWluZ2xvcnktbG9yZS10ZXN0MkB2YWluZ2xvcnktbG9yZS5pYW0uZ3NlcnZpY2VhY2NvdW50LmNvbSIsInN1YiI6InZhaW5nbG9yeS1sb3JlLXRlc3QyQHZhaW5nbG9yeS1sb3JlLmlhbS5nc2VydmljZWFjY291bnQuY29tIiwiYXVkIjoiaHR0cHM6Ly93d3cuZ29vZ2xlYXBpcy5jb20vb2F1dGgyL3Y0L3Rva2VuIiwic2NvcGUiOiJodHRwczovL3d3dy5nb29nbGVhcGlzLmNvbS9hdXRoL2RldnN0b3JhZ2UucmVhZF9vbmx5IiwiaWF0IjoxNTUzMDk2ODc0LCJleHAiOjE1NTMxMDA0NzR9
.
Y3-ftstpQEyXHFwtanyIyMFBmqdxr5GMWvLlOtuyzwdFzfOQK4sbfkVYejPQQdnxNH3Ve-PzKMtNO80-djODCKkMk-ZRtyQpidpAS89TNYoGBoGz6N1Ojg84GFdTb15W96-QINPG2MxIk43Ccshjs2VvTyvwG8T2Xo-b8i91t0_z-Q_GgsDSlaJuS0L-bd0ve8sL3wqgp3BXodh0XqpZ5_6_3JbecJAwLCrlNoK8WcwOAi5519Ef9FR_pJJFmu5Oi_jzPAzMqo_13FAe-ej9moy4k3EC45kevwiLDnIBkU2n76f5djjdTrI5UxwtUOkgLg_emYVURzFf5rDSZ_ESJh

third part of secret is not the same.
can you help with this?

JWT.io says for secret

RSASHA256(
base64UrlEncode(header) + "." +
base64UrlEncode(payload)

I am trying to RS256 too.
could you share the script ? thanks.

thanks for this code snippet ;)

didnt work secret for google JWT

i trying RS256 this one generated by your prescript:

eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCIsImtpZCI5IjkzYzA1ZWQ2NTc4NDRiYWM1ZjBmZGFmYTFhZThjMTdlNjFiZjU4ZDAifQ
.
eyJpc2MiOiJ2YWluZ2xvcnktbG9yZS10ZXN0MkB2YWluZ2xvcnktbG9yZS5pYW0uZ3NlcnZpY2VhY2NvdW50LmNvbSIsInN1YiI6InZhaW5nbG9yeS1sb3JlLXRlc3QyQHZhaW5nbG9yeS1sb3JlLmlhbS5nc2VydmljZWFjY291bnQuY29tIiwiYXVkIjoiaHR0cHM6Ly93d3cuZ29vZ2xlYXBpcy5jb20vb2F1dGgyL3Y0L3Rva2VuIiwic2NvcGUiOiJodHRwczovL3d3dy5nb29nbGVhcGlzLmNvbS9hdXRoL2RldnN0b3JhZ2UucmVhZF9vbmx5IiwiaWF0IjoxNTUzMDk2ODc0LCJleHAiOjE1NTMxMDA0NzR9
.
ZaCoMgyjg85nlOgm_dg7ydMe5aZwdR6fj_I5VRKZT7w

and this one by jwt.io:

eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCIsImtpZCI5IjkzYzA1ZWQ2NTc4NDRiYWM1ZjBmZGFmYTFhZThjMTdlNjFiZjU4ZDAifQ
.
eyJpc2MiOiJ2YWluZ2xvcnktbG9yZS10ZXN0MkB2YWluZ2xvcnktbG9yZS5pYW0uZ3NlcnZpY2VhY2NvdW50LmNvbSIsInN1YiI6InZhaW5nbG9yeS1sb3JlLXRlc3QyQHZhaW5nbG9yeS1sb3JlLmlhbS5nc2VydmljZWFjY291bnQuY29tIiwiYXVkIjoiaHR0cHM6Ly93d3cuZ29vZ2xlYXBpcy5jb20vb2F1dGgyL3Y0L3Rva2VuIiwic2NvcGUiOiJodHRwczovL3d3dy5nb29nbGVhcGlzLmNvbS9hdXRoL2RldnN0b3JhZ2UucmVhZF9vbmx5IiwiaWF0IjoxNTUzMDk2ODc0LCJleHAiOjE1NTMxMDA0NzR9
.
Y3-ftstpQEyXHFwtanyIyMFBmqdxr5GMWvLlOtuyzwdFzfOQK4sbfkVYejPQQdnxNH3Ve-PzKMtNO80-djODCKkMk-ZRtyQpidpAS89TNYoGBoGz6N1Ojg84GFdTb15W96-QINPG2MxIk43Ccshjs2VvTyvwG8T2Xo-b8i91t0_z-Q_GgsDSlaJuS0L-bd0ve8sL3wqgp3BXodh0XqpZ5_6_3JbecJAwLCrlNoK8WcwOAi5519Ef9FR_pJJFmu5Oi_jzPAzMqo_13FAe-ej9moy4k3EC45kevwiLDnIBkU2n76f5djjdTrI5UxwtUOkgLg_emYVURzFf5rDSZ_ESJh

third part of secret is not the same. can you help with this?

JWT.io says for secret

RSASHA256( base64UrlEncode(header) + "." + base64UrlEncode(payload)

I am facing the same hurdle. any solution to overcome this?

didnt work secret for google JWT
i trying RS256 this one generated by your prescript:

eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCIsImtpZCI5IjkzYzA1ZWQ2NTc4NDRiYWM1ZjBmZGFmYTFhZThjMTdlNjFiZjU4ZDAifQ
.
eyJpc2MiOiJ2YWluZ2xvcnktbG9yZS10ZXN0MkB2YWluZ2xvcnktbG9yZS5pYW0uZ3NlcnZpY2VhY2NvdW50LmNvbSIsInN1YiI6InZhaW5nbG9yeS1sb3JlLXRlc3QyQHZhaW5nbG9yeS1sb3JlLmlhbS5nc2VydmljZWFjY291bnQuY29tIiwiYXVkIjoiaHR0cHM6Ly93d3cuZ29vZ2xlYXBpcy5jb20vb2F1dGgyL3Y0L3Rva2VuIiwic2NvcGUiOiJodHRwczovL3d3dy5nb29nbGVhcGlzLmNvbS9hdXRoL2RldnN0b3JhZ2UucmVhZF9vbmx5IiwiaWF0IjoxNTUzMDk2ODc0LCJleHAiOjE1NTMxMDA0NzR9
.
ZaCoMgyjg85nlOgm_dg7ydMe5aZwdR6fj_I5VRKZT7w

and this one by jwt.io:

eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCIsImtpZCI5IjkzYzA1ZWQ2NTc4NDRiYWM1ZjBmZGFmYTFhZThjMTdlNjFiZjU4ZDAifQ
.
eyJpc2MiOiJ2YWluZ2xvcnktbG9yZS10ZXN0MkB2YWluZ2xvcnktbG9yZS5pYW0uZ3NlcnZpY2VhY2NvdW50LmNvbSIsInN1YiI6InZhaW5nbG9yeS1sb3JlLXRlc3QyQHZhaW5nbG9yeS1sb3JlLmlhbS5nc2VydmljZWFjY291bnQuY29tIiwiYXVkIjoiaHR0cHM6Ly93d3cuZ29vZ2xlYXBpcy5jb20vb2F1dGgyL3Y0L3Rva2VuIiwic2NvcGUiOiJodHRwczovL3d3dy5nb29nbGVhcGlzLmNvbS9hdXRoL2RldnN0b3JhZ2UucmVhZF9vbmx5IiwiaWF0IjoxNTUzMDk2ODc0LCJleHAiOjE1NTMxMDA0NzR9
.
Y3-ftstpQEyXHFwtanyIyMFBmqdxr5GMWvLlOtuyzwdFzfOQK4sbfkVYejPQQdnxNH3Ve-PzKMtNO80-djODCKkMk-ZRtyQpidpAS89TNYoGBoGz6N1Ojg84GFdTb15W96-QINPG2MxIk43Ccshjs2VvTyvwG8T2Xo-b8i91t0_z-Q_GgsDSlaJuS0L-bd0ve8sL3wqgp3BXodh0XqpZ5_6_3JbecJAwLCrlNoK8WcwOAi5519Ef9FR_pJJFmu5Oi_jzPAzMqo_13FAe-ej9moy4k3EC45kevwiLDnIBkU2n76f5djjdTrI5UxwtUOkgLg_emYVURzFf5rDSZ_ESJh

third part of secret is not the same. can you help with this?
JWT.io says for secret
RSASHA256( base64UrlEncode(header) + "." + base64UrlEncode(payload)

I am facing the same hurdle. any solution to overcome this?

I am also facing the same issue. Has anyone found a solution to this?

In my case changed secret to base64 worked perfectly. Those who are facing problem can try this out

var signature = CryptoJS.HmacSHA256(token, CryptoJS.enc.Base64.parse(secret));

reference this:
https://www.postman.com/postman/workspace/postman-team-collections/request/8140651-fa914e7e-362a-4698-8a5a-0c81dfebf5f9?tab=scripts

`var navigator = {};
var window = {};
eval(pm.environment.get("jsrsasign-js"));

var scope = pm.environment.get('scope');
var iss = pm.environment.get('iss');
var privateKey = pm.environment.get('privateKey');

const header = {"alg" : "RS256", "typ" : "JWT"};

const claimSet =
{
"iss": iss,
"scope": scope ,
"aud":"https://oauth2.googleapis.com/token",
"exp":KJUR.jws.IntDate.get("now + 1hour").toString(),
"iat": KJUR.jws.IntDate.get("now").toString()
}

console.log(header: ${ JSON.stringify(header)});
console.log(claim set: ${ JSON.stringify(claimSet) });
console.log(Private Key: ${ privateKey });

// let jws = new KJUR.jws.JWS();
var jwt = KJUR.jws.JWS.sign(null, header, claimSet, privateKey);
console.log(jwt);

pm.environment.set('jwt', jwt);`