postman-azure-iot-sas-token-pre-request-script.js

var iotHubName = pm.environment.get("iotHubName");
var iotHubKey = pm.environment.get("iotHubKey");
var iotHubTokenExpiration = pm.environment.get("iotHubTokenExpiration");
var iotHubPolicyName = pm.environment.get("iotHubPolicyName");

pm.globals.clear("iotHubSasToken"); // clear out token on first run.

// See this doc for details: https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-security
var resourceUri = encodeURIComponent(iotHubName + '.azure-devices.net'); // The resource uri
var expiry = Math.ceil((Date.now() / 1000) + iotHubTokenExpiration * 60); // Expire the token 60 minutes from now
var uriExpiry = resourceUri + '\n' + expiry; // this is the string format to gen signature from
var decodedKey = CryptoJS.enc.Base64.parse(iotHubKey); // The SHA256 key is the Base64 decoded version of the IoT Hub key
var signature = CryptoJS.HmacSHA256(uriExpiry, decodedKey); // The signature generated from the decodedKey
var encodedUri = encodeURIComponent(CryptoJS.enc.Base64.stringify(signature)); // The url encoded version of the Base64 signature

// Construct authorization string (shared access signature)
var iotHubSasToken = "SharedAccessSignature sr=" + resourceUri + "&sig=" + encodedUri + "&se=" + expiry;

// Add token if one is present
if (iotHubPolicyName) {
    iotHubSasToken += "&skn="+ iotHubPolicyName;
}

// Put in variable to be used in other requests.
pm.globals.set("iotHubSasToken", iotHubSasToken);

console.log("Shared Access Signature:" + pm.globals.get("iotHubSasToken"));