preflight OPTIONS check gives 403 with Access-Control-Allow-Origin ”*” - ajax

Question

I have a single page app served on one subdomain and an api on another. I get a 403 Forbidden on the pre-flight check for an XHR POST to the api.
Debugging it in curl shows:
curl -H "Host: backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com" \
-H "Origin: http://frontend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com" \
-H "Access-Control-Request-Method: POST" \
-H "Access-Control-Request-Headers: content-type" \
-X OPTIONS --verbose http://backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com/api/users
* Trying 54.153.79.158...
* TCP_NODELAY set
* Connected to backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com (54.153.79.158) port 80 (#0)
> OPTIONS /api/users HTTP/1.1
> Host: backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com
> User-Agent: curl/7.54.0
> Accept: */*
> Origin: http://frontend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com
> Access-Control-Request-Method: POST
> Access-Control-Request-Headers: content-type
>
* HTTP 1.0, assume close after body
< HTTP/1.0 403 Forbidden
< Date: Fri, 04 May 2018 21:16:52 GMT
< Server: Apache/2.4.27 (Red Hat) OpenSSL/1.0.1e-fips
< Cache-Control: no-cache, private
< Access-Control-Allow-Origin: *
< Access-Control-Allow-Headers: accept, access-control-allow-origin, content-type
< Access-Control-Allow-Methods: PUT, GET, POST, DELETE, OPTIONS
< Content-Length: 18
< Content-Type: text/html; charset=UTF-8
< Set-Cookie: 45fe47f0bb613513b8e98d0599b628f9=dd4b5c95b51d6168419458748b392421; path=/; HttpOnly
* HTTP/1.0 connection set to keep alive!
< Connection: keep-alive
<
* Connection #0 to host backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com left intact
Origin not allowed
Yet the Access-Control-Allow-Origin: * in the response suggests that it should allow the Origin: http://frontend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com named the request.
If I drop the Origin header from the request I get a 200.
I tried explicitly setting the Access-Control-Allow-Origin on the server to match match the Origin of the request but that also gets back a 403:
curl -H "Host: backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com" \
-H "Origin: http://frontend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com" \
-H "Access-Control-Request-Method: POST" \
-H "Access-Control-Request-Headers: content-type" \
-X OPTIONS --verbose http://backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com/api/users
* Trying 54.153.79.158...
* TCP_NODELAY set
* Connected to backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com (54.153.79.158) port 80 (#0)
> OPTIONS /api/users HTTP/1.1
> Host: backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com
> User-Agent: curl/7.54.0
> Accept: */*
> Origin: http://frontend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com
> Access-Control-Request-Method: POST
> Access-Control-Request-Headers: content-type
>
* HTTP 1.0, assume close after body
< HTTP/1.0 403 Forbidden
< Date: Fri, 04 May 2018 21:32:52 GMT
< Server: Apache/2.4.27 (Red Hat) OpenSSL/1.0.1e-fips
< Cache-Control: no-cache, private
< Access-Control-Allow-Origin: http://frontend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com
< Access-Control-Allow-Headers: accept, access-control-allow-origin, content-type
< Access-Control-Allow-Methods: PUT, GET, POST, DELETE, OPTIONS
< Content-Length: 18
< Content-Type: text/html; charset=UTF-8
< Set-Cookie: 45fe47f0bb613513b8e98d0599b628f9=a913ecc9ded73c3ac76fbb38d93e15a7; path=/; HttpOnly
* HTTP/1.0 connection set to keep alive!
< Connection: keep-alive
<
* Connection #0 to host backend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com left intact
Origin not allowed
On the server the .htaccess has the following configuration:
<IfModule mod_headers.c>
Header add Access-Control-Allow-Origin "http://frontend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com"
Header add Access-Control-Allow-Headers "accept, access-control-allow-origin, content-type"
Header add Access-Control-Allow-Methods "PUT, GET, POST, DELETE, OPTIONS"
</IfModule>
Setting the Access-Control-Allow-Origin to "*" doesn't fix the issue.
Why is the response 403 forbidden when the origin seems to be allowed and how might I fix it?
Thanks!
UPDATE
Here is my latest .htaccess which is for the laravel PHP backend:
<IfModule mod_rewrite.c>
<IfModule mod_negotiation.c>
Options -MultiViews -Indexes
</IfModule>
RewriteEngine On
# Handle Authorization Header
RewriteCond %{HTTP:Authorization} .
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
# Redirect Trailing Slashes If Not A Folder...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} (.+)/$
RewriteRule ^ %1 [L,R=301]
# Handle Front Controller...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]
</IfModule>
<IfModule mod_headers.c>
Header add Access-Control-Allow-Origin "*"
Header add Access-Control-Allow-Headers "*"
Header add Access-Control-Allow-Methods "PUT, GET, POST, DELETE, OPTIONS"
</IfModule>

Answer 1

As #roryhewitt suggested in a comment to the question this wasn't an apache .htaccess issue. The problem was the backend API laravel app was giving 403 to any CORS request.
I deleted the mod_headers.c configuration and configured the barryvdh/laravel-cors module used by the backend app using an environment variable CORS_ALLOWED_ORIGINS=frontend-sjm-staging.a3c1.starter-us-west-1.openshiftapps.com. This sets the allowedOrigins as shown here.