REST API Authentication from Postman vs Web App - authentication

Question

I am trying to perform some actions on the Tableau server via REST API for which I require the Auth token. I tried using the signin API from Postman and it works like a charm. However the same code is giving "Bad Request" error whe tried calling from javacript code from my webpage.
var dataVal = {
"credentials": {
"name": "admin",
"password": "admin",
"site": {
"contentUrl": "MySite"
}
}
};
$.ajax({
contentType: 'application/json',
data: JSON.stringify(dataVal),
dataType: 'jsonp',
success: function (data) {
console.log("call succeeded");
},
error: function (request, textStatus, errorThrown) {
console.log(request.getAllResponseHeaders());
},
processData: false,
type: 'POST',
url: 'http://mytableauserver/api/2.6/auth/signin'
});
The above code return token, siteid, userid from postman but return ""BAD REQUEST" error from javascript code. Any pointers will be highly appreciated.

Answer 1

For anyone else looking, Tableau now supports CORS but only on Tableau Server at this point.
Enabling CORS on Tableau Server for the REST API
For security, most web browsers restrict HTTP requests to the same origin. That is, to
access a resource on a server through an API, the request must come from the same
origin (server), or a proxy must be set up to handle the request.
Tableau Server now supports Cross-Origin Resource Sharing (CORS), so you can do away
with your proxy and call the REST API from the browser. The CORS mechanism is
currently only enabled for Tableau Server, and can be turned on by server
administrators in a couple of steps using the TSM command-line tool. To learn more,
see the description of the vizportal.rest_api.cors.allow_origin option in tsm
configuration set Options. As a security measure, you should make API calls to Tableau
Server using the HTTPS protocol (SSL or TLS). See Using HTTPS (SSL/TLS) for API Calls.
Add the origins that need access to the Tableau Server.
Determine the origins (servers) you want to allow access to the REST API, and use the
tsm configuration set command with the vizportal.rest_api.cors.allow_origin option.
For example, to grant access to one two origins, https://mysite and https://yoursite,
you would stop the server (tsm stop) and then use the following command:
tsm configuration set -k vizportal.rest_api.cors.allow_origin -v
https://mysite,https://yoursite
You can enter multiple origins. Use a comma to separate the entries.
Note: You could also use an asterisk (*) as a wild card to match all sites. This is
not recommended as it allows access from any origin that has access to the server and
could present a security risk. Do not use an asterisk (*) unless you fully understand
the implications and risks for your site.
Enable CORS on Tableau Server.
Use the tsm configuration set command with the vizportal.rest_api.cors.enabled option.
The default setting is false, so set this to true as follows:
tsm configuration set -k vizportal.rest_api.cors.enabled -v true
Update your Tableau Server configuration (tsm pending-changes apply) to restart
Tableau Server and make the changes take effect. Only the origins you specify will
have access.
https://help.tableau.com/current/api/rest_api/en-us/REST/rest_api_concepts_fundamentals.htm