Server: Adds an option to allow CORS

server/src/main.rs

@@ -1,7 +1,7 @@
 use anyhow::{anyhow, bail, Context, Error};
 use clap::{Parser, Subcommand};
 use flate2::read::MultiGzDecoder;
-use oxhttp::model::{Body, HeaderName, HeaderValue, Request, Response, Status};
+use oxhttp::model::{Body, HeaderName, HeaderValue, Method, Request, Response, Status};
 use oxhttp::Server;
 use oxigraph::io::{DatasetFormat, DatasetSerializer, GraphFormat, GraphSerializer};
 use oxigraph::model::{
@@ -52,6 +52,9 @@ enum Command {
         /// Host and port to listen to.
         #[arg(short, long, default_value = "localhost:7878")]
         bind: String,
+        /// Allows cross-origin requests
+        #[arg(long)]
+        cors: bool,
     },
     /// Start Oxigraph HTTP server in read-only mode.
     ///
@@ -62,6 +65,9 @@ enum Command {
         /// Host and port to listen to.
         #[arg(short, long, default_value = "localhost:7878")]
         bind: String,
+        /// Allows cross-origin requests
+        #[arg(long)]
+        cors: bool,
     },
     /// Start Oxigraph HTTP server in secondary mode.
     ///
@@ -82,6 +88,9 @@ enum Command {
         /// Host and port to listen to.
         #[arg(short, long, default_value = "localhost:7878")]
         bind: String,
+        /// Allows cross-origin requests
+        #[arg(long)]
+        cors: bool,
     },
     /// Creates database backup into a target directory.
     ///
@@ -219,7 +228,7 @@ enum Command {
 pub fn main() -> anyhow::Result<()> {
     let matches = Args::parse();
     match matches.command {
-        Command::Serve { bind } => serve(
+        Command::Serve { bind, cors } => serve(
             if let Some(location) = matches.location {
                 Store::open(location)
             } else {
@@ -227,8 +236,9 @@ pub fn main() -> anyhow::Result<()> {
             }?,
             bind,
             false,
+            cors,
         ),
-        Command::ServeReadOnly { bind } => serve(
+        Command::ServeReadOnly { bind, cors } => serve(
             Store::open_read_only(
                 matches
                     .location
@@ -236,11 +246,13 @@ pub fn main() -> anyhow::Result<()> {
             )?,
             bind,
             true,
+            cors,
         ),
         Command::ServeSecondary {
             primary_location,
             secondary_location,
             bind,
+            cors,
         } => {
             let primary_location = primary_location.or(matches.location).ok_or_else(|| {
                 anyhow!("Either the --location or the --primary-location argument is required")
@@ -253,6 +265,7 @@ pub fn main() -> anyhow::Result<()> {
                 }?,
                 bind,
                 true,
+                cors,
             )
         }
         Command::Backup { destination } => {
@@ -745,11 +758,18 @@ impl FromStr for GraphOrDatasetFormat {
     }
 }
 
-fn serve(store: Store, bind: String, read_only: bool) -> anyhow::Result<()> {
-    let mut server = Server::new(move |request| {
-        handle_request(request, store.clone(), read_only)
-            .unwrap_or_else(|(status, message)| error(status, message))
-    });
+fn serve(store: Store, bind: String, read_only: bool, cors: bool) -> anyhow::Result<()> {
+    let mut server = if cors {
+        Server::new(cors_middleware(move |request| {
+            handle_request(request, store.clone(), read_only)
+                .unwrap_or_else(|(status, message)| error(status, message))
+        }))
+    } else {
+        Server::new(move |request| {
+            handle_request(request, store.clone(), read_only)
+                .unwrap_or_else(|(status, message)| error(status, message))
+        })
+    };
     server.set_global_timeout(HTTP_TIMEOUT);
     server.set_server_name(concat!("Oxigraph/", env!("CARGO_PKG_VERSION")))?;
     eprintln!("Listening for requests at http://{}", &bind);
@@ -757,6 +777,50 @@ fn serve(store: Store, bind: String, read_only: bool) -> anyhow::Result<()> {
     Ok(())
 }
 
+fn cors_middleware(
+    on_request: impl Fn(&mut Request) -> Response + Send + Sync + 'static,
+) -> impl Fn(&mut Request) -> Response + Send + Sync + 'static {
+    let origin = HeaderName::from_str("Origin").unwrap();
+    let access_control_allow_origin = HeaderName::from_str("Access-Control-Allow-Origin").unwrap();
+    let access_control_request_method =
+        HeaderName::from_str("Access-Control-Request-Method").unwrap();
+    let access_control_allow_method = HeaderName::from_str("Access-Control-Allow-Methods").unwrap();
+    let access_control_request_headers =
+        HeaderName::from_str("Access-Control-Request-Headers").unwrap();
+    let access_control_allow_headers =
+        HeaderName::from_str("Access-Control-Allow-Headers").unwrap();
+    let star = HeaderValue::from_str("*").unwrap();
+    move |request| {
+        if *request.method() == Method::OPTIONS {
+            let mut response = Response::builder(Status::NO_CONTENT);
+            if request.header(&origin).is_some() {
+                response
+                    .headers_mut()
+                    .append(access_control_allow_origin.clone(), star.clone());
+            }
+            if let Some(method) = request.header(&access_control_request_method) {
+                response
+                    .headers_mut()
+                    .append(access_control_allow_method.clone(), method.clone());
+            }
+            if let Some(headers) = request.header(&access_control_request_headers) {
+                response
+                    .headers_mut()
+                    .append(access_control_allow_headers.clone(), headers.clone());
+            }
+            response.build()
+        } else {
+            let mut response = on_request(request);
+            if request.header(&origin).is_some() {
+                response
+                    .headers_mut()
+                    .append(access_control_allow_origin.clone(), star.clone());
+            }
+            response
+        }
+    }
+}
+
 type HttpError = (Status, String);
 
 fn handle_request(