ubus: add CORS header support

In order to support cross-domain AJAX requests to the /ubus endpoint
we need to implement the Cross-Origin Resource Sharing (CORS) spec
in the ubus plugin.

- Implement a new option "-X" to enable CORS support in ubus
- Implement rudimentary support for "OPTIONS" HTTP requests
- Implement essential CORS headers the ubus plugin

The current CORS response headers merely reflect the request headers
sent by the client, this way any requesting origin is automatically
allowed. Cross-domain cookies (Access-Control-Allow-Credentials) are
unconditionally enabled.

Restricting permitted origins and toggle the credential accepting can
be made configurable in a future commit to allow more fine grained
control over permitted AJAX clients.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/uhttpd.h b/uhttpd.h
index daf68ce..6ef28d9 100644
--- a/uhttpd.h
+++ b/uhttpd.h
@@ -68,6 +68,7 @@ struct config {
 	int http_keepalive;
 	int script_timeout;
 	int ubus_noauth;
+	int ubus_cors;
 };
 
 struct auth_realm {
@@ -81,6 +82,7 @@ enum http_method {
 	UH_HTTP_MSG_GET,
 	UH_HTTP_MSG_POST,
 	UH_HTTP_MSG_HEAD,
+	UH_HTTP_MSG_OPTIONS,
 };
 
 enum http_version {