// CsrfFilter enables CSRF request token creation and verification.
//
// Usage:
// 1) Add `csrf.CsrfFilter` to the app's filters (it must come after the revel.SessionFilter).
// 2) Add CSRF fields to a form with the template tag `{{ csrftoken . }}`. The filter adds a function closure to the `RenderArgs` that can pull out the secret and make the token as-needed, caching the value in the request. Ajax support provided through the `X-CSRFToken` header.
func CsrfFilter(c *revel.Controller, fc []revel.Filter) {
token, foundToken := c.Session["csrf_token"]
if !foundToken {
RefreshToken(c)
}
referer, refErr := url.Parse(c.Request.Header.Get("Referer"))
isSameOrigin := sameOrigin(c.Request.URL, referer)
// If the Request method isn't in the white listed methods
if !allowedMethods[c.Request.Method] && !IsExempt(c) {
// Token wasn't present at all
if !foundToken {
c.Result = c.Forbidden("REVEL CSRF: Session token missing.")
return
}
// Referer header is invalid
if refErr != nil {
c.Result = c.Forbidden("REVEL CSRF: HTTP Referer malformed.")
return
}
// Same origin
if !isSameOrigin {
c.Result = c.Forbidden("REVEL CSRF: Same origin mismatch.")
return
}
var requestToken string
// First check for token in post data
if c.Request.Method == "POST" {
requestToken = c.Request.FormValue("csrftoken")
}
// Then check for token in custom headers, as with AJAX
if requestToken == "" {
requestToken = c.Request.Header.Get("X-CSRFToken")
}
if requestToken == "" || !compareToken(requestToken, token) {
c.Result = c.Forbidden("REVEL CSRF: Invalid token.")
return
}
}
fc[0](c, fc[1:])
// Only add token to RenderArgs if the request is: not AJAX, not missing referer header, and is same origin.
if c.Request.Header.Get("X-CSRFToken") == "" && isSameOrigin {
c.RenderArgs["_csrftoken"] = token
}
}