With Spring Security 3.2.0.RELEASE, how can I get the CSRF token in a page that is purely HTML with no tag libs - spring

Question

Today I upgraded from Spring Security 3.1.4 with the separate java config dependency, to the new 3.2.0 release which includes java config. CSRF is on by default and I know I can disable it in my overridden configure method with "http.csrf().disable()". But suppose I don't want to disable it, but I need the CSRF token on my login page where no JSP tag libs or Spring tag libs are being used.
My login page is purely HTML that I use in a Backbone app that I've generated using Yeoman. How would I go about including the CSRF token that's contained in the HttpSession in either the form or as a header so that I don't get the "Expected CSRF token not found. Has your session expired?" exception?

Answer 1

You can obtain the CSRF using the request attribute named _csrf as outlined in the reference. To add the CSRF to an HTML page, you will need to use JavaScript to obtain the token that needs to be included in the requests.
It is safer to return the token as a header than in the body as JSON since JSON in the body could be obtained by external domains. For example your JavaScript could request a URL processed by the following:
CsrfToken token = (CsrfToken) request.getAttribute("_csrf");
// Spring Security will allow the Token to be included in this header name
response.setHeader("X-CSRF-HEADER", token.getHeaderName());
// Spring Security will allow the token to be included in this parameter name
response.setHeader("X-CSRF-PARAM", token.getParameterName());
// this is the value of the token to be included as either a header or an HTTP parameter
response.setHeader("X-CSRF-TOKEN", token.getToken());
Your JavaScript would then obtain the header name or the parameter name and the token from the response header and add it to the login request.

Answer 2

Although #rob-winch is right I would suggest to take token from session. If Spring-Security generates new token in SessionManagementFilter using CsrfAuthenticationStrategy it will set it to Session but not on Request. So it is possible you will end up with wrong csrf token.
public static final String DEFAULT_CSRF_TOKEN_ATTR_NAME = HttpSessionCsrfTokenRepository.class.getName().concat(".CSRF_TOKEN");
CsrfToken sessionToken = (CsrfToken) request.getSession().getAttribute(DEFAULT_CSRF_TOKEN_ATTR_NAME);

Answer 3

Note: I'm using CORS and AngularJS.
Note²: I found Stateless Spring Security Part 1: Stateless CSRF protection which would be interesting to keep the AngularJS' way to handle CSRF.
Instead of using Spring Security CSRF Filter which is based on answers (especially #Rob Winch's one), I used the method described in The Login Page: Angular JS and Spring Security Part II.
In addition to this, I had to add Access-Control-Allow-Headers: ..., X-CSRF-TOKEN (due to CORS).
Actually, I find this method cleaner than adding headers to the response.
Here is the code :
HttpHeaderFilter.java
#Component("httpHeaderFilter")
public class HttpHeaderFilter extends OncePerRequestFilter {
#Autowired
private List<HttpHeaderProvider> providerList;
#Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
providerList.forEach(e -> e.filter(request, response));
if (HttpMethod.OPTIONS.toString().equals(request.getMethod())) {
response.setStatus(HttpStatus.OK.value());
}
else {
filterChain.doFilter(request, response);
}
}
}
HttpHeaderProvider.java
public interface HttpHeaderProvider {
void filter(HttpServletRequest request, HttpServletResponse response);
}
CsrfHttpHeaderProvider.java
#Component
public class CsrfHttpHeaderProvider implements HttpHeaderProvider {
#Override
public void filter(HttpServletRequest request, HttpServletResponse response) {
response.addHeader(HttpHeaders.ACCESS_CONTROL_ALLOW_HEADERS, "X-CSRF-TOKEN");
}
}
CsrfTokenFilter.java
#Component("csrfTokenFilter")
public class CsrfTokenFilter extends OncePerRequestFilter {
#Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
CsrfToken csrf = (CsrfToken)request.getAttribute(CsrfToken.class.getName());
if (csrf != null) {
Cookie cookie = WebUtils.getCookie(request, "XSRF-TOKEN");
String token = csrf.getToken();
if (cookie == null || token != null && !token.equals(cookie.getValue())) {
cookie = new Cookie("XSRF-TOKEN", token);
cookie.setPath("/");
response.addCookie(cookie);
}
}
filterChain.doFilter(request, response);
}
}
web.xml
...
<filter>
<filter-name>httpHeaderFilter</filter-name>
<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
<async-supported>true</async-supported>
</filter>
<filter-mapping>
<filter-name>httpHeaderFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
...
security-context.xml
...
<custom-filter ref="csrfTokenFilter" after="CSRF_FILTER"/>
...
app.js
...
.run(['$http', '$cookies', function ($http, $cookies) {
$http.defaults.transformResponse.unshift(function (data, headers) {
var csrfToken = $cookies['XSRF-TOKEN'];
if (!!csrfToken) {
$http.defaults.headers.common['X-CSRF-TOKEN'] = csrfToken;
}
return data;
});
}]);

Answer 4

I use thymeleaf with Spring boot. I had the same problem. I diagnosed problem viewing source of returned html via browser. It should be look like this:
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:sec="http://www.thymeleaf.org/thymeleaf-extras-springsecurity3">
<head>
<title>Spring Security Example </title>
</head>
<body>
<form method="post" action="/login">
<div><label> User Name : <input type="text" name="username" /> </label></div>
<div><label> Password: <input type="password" name="password" /> </label></div>
<input type="hidden" name="_csrf" value=<!--"aaef0ba0-1c75-4434-b6cf-62c975dcc8ba"--> />
<div><input type="submit" value="Sign In" /></div>
</form>
</body>
</html>
If you can't see this html code. You may be forgot to put th: tag before name and value. <input type="hidden" th:name="${_csrf.parameterName}" th:value="${_csrf.token}"/>
login.html
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org" xmlns:sec="http://www.thymeleaf.org/thymeleaf-extras-springsecurity3">
<head>
<title>Spring Security Example </title>
</head>
<body>
<div th:if="${param.error}"> Invalid username and password. </div>
<div th:if="${param.logout}"> You have been logged out. </div>
<form th:action="#{/login}" method="post">
<div><label> User Name : <input type="text" name="username"/> </label></div>
<div><label> Password: <input type="password" name="password"/> </label></div>
<input type="hidden" th:name="${_csrf.parameterName}" th:value="${_csrf.token}"/>
<div><input type="submit" value="Sign In"/></div>
</form>
</body>
</html>