pre-request.js

/*
 * This is a Pre-request script for Postman client to remediate OAuth 1.0a issue
 * where certain request fails if the query parameter includes some specific characters.
 * https://tools.ietf.org/html/rfc3986#section-2.2 (rfc3986, gen-delims reserved characters)
 *
 * NOTE: This Pre-script is intended to use with "GET" request but might be able to
 *       work with other methods that have no request body.
 *       For "POST" request, there's another workaround.
 *       See: https://github.com/twitterdev/postman-twitter-ads-api/issues/2
 * 
 * In order to use this Pre-request script, you need to change your "Authorization" type to
 * "No Auth" only for the target request and do not apply to the top-level object.
 */

const sdk = require('postman-collection');

function toArray(object) {
    let array = [];
    Object.keys(object).forEach(key => {
        array.push(`${key}=${object[key]}`);
    });
    return array
}

// fetch all env variables that are currently defined
const env_variables = pm.environment.toObject({
    excludeDisabled: true
});

const oauth_consumer_key = env_variables.consumer_key;
const oauth_consumer_secret = env_variables.consumer_secret;
const oauth_token = env_variables.access_token;
const oauth_secret = env_variables.token_secret;
const oauth_signing_key = `${oauth_consumer_secret}&${oauth_secret}`;

// create random oauth_nonce string
const random_source = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
var oauth_nonce = '';
for (var i = 0; i < 32; i++) {
    oauth_nonce += random_source.charAt(Math.floor(Math.random() * random_source.length));
}

const oauth_parameter_string_object = {};
oauth_parameter_string_object.oauth_consumer_key = oauth_consumer_key;
oauth_parameter_string_object.oauth_token = oauth_token;
const oauth_nonce_array = CryptoJS.enc.Utf8.parse(oauth_nonce);
oauth_parameter_string_object.oauth_nonce = encodeURIComponent(CryptoJS.enc.Base64.stringify(oauth_nonce_array));
oauth_parameter_string_object.oauth_signature_method = 'HMAC-SHA1';
oauth_parameter_string_object.oauth_version = '1.0';
oauth_parameter_string_object.oauth_timestamp = Math.round((new Date()).getTime() / 1000);

// for Authorization request header (copy object)
const oauth_authorization_header_object = Object.assign({}, oauth_parameter_string_object);

// convert query string into object (+ encode)
const url_query_string_object = {};

const url_query_string_object_array = sdk.QueryParam.parse(
    pm.request.url.getQueryString({
        ignoreDisabled: true
    })
);

url_query_string_object_array.forEach(item => {
    url_query_string_object[item.key] = encodeURIComponent(item.value);
});

// merge query parameter
Object.assign(oauth_parameter_string_object, url_query_string_object);

// sort object by key
const oauth_parameter_string_object_ordered = {};
Object.keys(oauth_parameter_string_object).sort().forEach(function(key) {
    oauth_parameter_string_object_ordered[key] = oauth_parameter_string_object[key];
});

// generate parameter string
const oauth_parameter_string = toArray(oauth_parameter_string_object_ordered).join('&');

// replace dynamic variables
let base_host = pm.request.url.getOAuth1BaseUrl();
let regexp = /{{(.*?)}}/g;
while (result = regexp.exec(base_host)) {
    let value = env_variables[result[1]];
    base_host = base_host.replace(new RegExp(`{{${result[1]}}}`, 'g'), value);
}

// generate base string
const oauth_base_string = `${pm.request.method}&${encodeURIComponent(base_host)}&${encodeURIComponent(oauth_parameter_string)}`;

// generate signature
const oauth_signature = CryptoJS.enc.Base64.stringify(CryptoJS.HmacSHA1(oauth_base_string, oauth_signing_key));

oauth_authorization_header_object.oauth_signature = encodeURIComponent(oauth_signature);

// generate Authorization header string
const oauth_authorization_header = toArray(oauth_authorization_header_object).join(', ');

// generate Authorization header
pm.request.headers.add({
    key: 'Authorization',
    value: `OAuth ${oauth_authorization_header}`
});

// Escape URI parameters using encodeURIComponent => RFC3986
if (Object.keys(url_query_string_object).length !== 0) {
    // generate query parameter string
    const request_parameter_string = toArray(url_query_string_object).join('&');

    pm.request.url = `${pm.request.url.getOAuth1BaseUrl()}?${request_parameter_string}`;
}