Allow CORS requests in Secret Store API (#10584)

* allow CORS requests for Secret Store API (#10582)

* secretstore CORS: fix error with unit tests

* secretstore CORS: removed debug log

* secretstore CORS: add missing response's header

* secretstore CORS: switched to jsonrpc-server-utils for CORS validation

Cargo.lock

@@ -1074,6 +1074,7 @@ dependencies = [
  "ethkey 0.3.0",
  "futures 0.1.25 (registry+https://github.com/rust-lang/crates.io-index)",
  "hyper 0.12.19 (registry+https://github.com/rust-lang/crates.io-index)",
+ "jsonrpc-server-utils 11.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "keccak-hash 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "kvdb 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "kvdb-rocksdb 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1853,6 +1854,18 @@ dependencies = [
  "serde_json 1.0.39 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "jsonrpc-core"
+version = "11.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "futures 0.1.25 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.89 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.89 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_json 1.0.39 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "jsonrpc-derive"
 version = "10.0.2"
@@ -1916,6 +1929,22 @@ dependencies = [
  "unicase 2.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "jsonrpc-server-utils"
+version = "11.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "bytes 0.4.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "globset 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "jsonrpc-core 11.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num_cpus 1.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-codec 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicase 2.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "jsonrpc-tcp-server"
 version = "10.0.1"
@@ -2349,7 +2378,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
  "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand 0.3.22 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -4593,11 +4622,13 @@ dependencies = [
 "checksum jni 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "294eca097d1dc0bf59de5ab9f7eafa5f77129e9f6464c957ed3ddeb705fb4292"
 "checksum jni-sys 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "8eaf4bc02d17cbdd7ff4c7438cafcdf7fb9a4613313ad11b4f8fefe7d3fa0130"
 "checksum jsonrpc-core 10.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7a5152c3fda235dfd68341b3edf4121bc4428642c93acbd6de88c26bf95fc5d7"
+"checksum jsonrpc-core 11.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "97b83fdc5e0218128d0d270f2f2e7a5ea716f3240c8518a58bc89e6716ba8581"
 "checksum jsonrpc-derive 10.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "c14be84e86c75935be83a34c6765bf31f97ed6c9163bb0b83007190e9703940a"
 "checksum jsonrpc-http-server 10.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "99e1ce36c7cc9dcab398024d76849ab2cb917ee812653bce6f74fc9eb7c82d16"
 "checksum jsonrpc-ipc-server 10.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "fac6b8682243740a32bfb288880c71cc06eca29616cdf551e4136a190b11b96d"
 "checksum jsonrpc-pubsub 10.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "56608ed54b1b2a69f4357cb8bdfbcbd99fe1179383c03a09bb428931bd35f592"
 "checksum jsonrpc-server-utils 10.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "5521613b31ea22d36d9f95ad642058dccec846a94ed8690957652d479f620707"
+"checksum jsonrpc-server-utils 11.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "e3372b3248a53abcca8f61924f188052bb0c4cd80b482b2b4eaf9f8667efb9f4"
 "checksum jsonrpc-tcp-server 10.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c873dac37a601fb88d40ba49eeac3f1aa60953c06b2e99ddbf0569b6f8028478"
 "checksum jsonrpc-ws-server 10.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "20b8333a5a6e6ccbcf5c90f90919de557cba4929efa164e9bd0e8e497eb20e46"
 "checksum keccak-hash 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "253bbe643c32c816bf58fa5a88248fafedeebb139705ad17a62add3517854a86"

parity/cli/mod.rs

@@ -623,6 +623,10 @@ usage! {
 			"--no-secretstore-auto-migrate",
 			"Do not run servers set change session automatically when servers set changes. This option has no effect when servers set is read from configuration file.",
 
+			ARG arg_secretstore_http_cors: (String) = "none", or |c: &Config| c.secretstore.as_ref()?.cors.as_ref().map(|vec| vec.join(",")),
+			"--secretstore-http-cors=[URL]",
+			"Specify CORS header for Secret Store HTTP API responses. Special options: \"all\", \"none\".",
+
 			ARG arg_secretstore_acl_contract: (Option<String>) = Some("registry".into()), or |c: &Config| c.secretstore.as_ref()?.acl_contract.clone(),
 			"--secretstore-acl-contract=[SOURCE]",
 			"Secret Store permissioning contract address source: none, registry (contract address is read from 'secretstore_acl_checker' entry in registry) or address.",
@@ -1328,6 +1332,7 @@ struct SecretStore {
 	http_interface: Option<String>,
 	http_port: Option<u16>,
 	path: Option<String>,
+	cors: Option<Vec<String>>
 }
 
 #[derive(Default, Debug, PartialEq, Deserialize)]
@@ -1854,6 +1859,7 @@ mod tests {
 			arg_secretstore_http_interface: "local".into(),
 			arg_secretstore_http_port: 8082u16,
 			arg_secretstore_path: "$HOME/.parity/secretstore".into(),
+			arg_secretstore_http_cors: "null".into(),
 
 			// IPFS
 			flag_ipfs_api: false,
@@ -2132,6 +2138,7 @@ mod tests {
 				http_interface: None,
 				http_port: Some(8082),
 				path: None,
+				cors: None,
 			}),
 			private_tx: None,
 			ipfs: Some(Ipfs {

parity/cli/tests/config.full.toml

@@ -105,6 +105,7 @@ http_port = 8082
 interface = "local"
 port = 8083
 path = "$HOME/.parity/secretstore"
+cors = ["null"]
 
 [ipfs]
 enable = false

parity/configuration.rs

@@ -638,6 +638,7 @@ impl Configuration {
 			http_port: self.args.arg_ports_shift + self.args.arg_secretstore_http_port,
 			data_path: self.directories().secretstore,
 			admin_public: self.secretstore_admin_public()?,
+			cors: self.secretstore_cors()
 		})
 	}
 
@@ -1058,6 +1059,10 @@ impl Configuration {
 		self.interface(&self.args.arg_secretstore_http_interface)
 	}
 
+	fn secretstore_cors(&self) -> Option<Vec<String>> {
+		Self::cors(self.args.arg_secretstore_http_cors.as_ref())
+	}
+
 	fn secretstore_self_secret(&self) -> Result<Option<NodeSecretKey>, String> {
 		match self.args.arg_secretstore_secret {
 			Some(ref s) if s.len() == 64 => Ok(Some(NodeSecretKey::Plain(s.parse()
@@ -1969,4 +1974,19 @@ mod tests {
 			_ => panic!("Should be Cmd::Run"),
 		}
 	}
+
+	#[test]
+	fn should_parse_secretstore_cors() {
+		// given
+
+		// when
+		let conf0 = parse(&["parity"]);
+		let conf1 = parse(&["parity", "--secretstore-http-cors", "*"]);
+		let conf2 = parse(&["parity", "--secretstore-http-cors", "http://parity.io,http://something.io"]);
+
+		// then
+		assert_eq!(conf0.secretstore_cors(), Some(vec![]));
+		assert_eq!(conf1.secretstore_cors(), None);
+		assert_eq!(conf2.secretstore_cors(), Some(vec!["http://parity.io".into(),"http://something.io".into()]));
+	}
 }

parity/secretstore.rs

@@ -84,6 +84,8 @@ pub struct Configuration {
 	pub data_path: String,
 	/// Administrator public key.
 	pub admin_public: Option<Public>,
+	// Allowed CORS domains
+	pub cors: Option<Vec<String>>,
 }
 
 /// Secret store dependencies
@@ -195,6 +197,7 @@ mod server {
 					admin_public: conf.admin_public,
 					auto_migrate_enabled: conf.auto_migrate_enabled,
 				},
+				cors: conf.cors
 			};
 
 			cconf.cluster_config.nodes.insert(self_secret.public().clone(), cconf.cluster_config.listener_address.clone());
@@ -234,6 +237,7 @@ impl Default for Configuration {
 			http_interface: "127.0.0.1".to_owned(),
 			http_port: 8082,
 			data_path: replace_home(&data_dir, "$BASE/secretstore"),
+			cors: Some(vec![]),
 		}
 	}
 }

secret-store/Cargo.toml

@@ -36,6 +36,7 @@ tokio = "~0.1.11"
 tokio-io = "0.1"
 tokio-service = "0.1"
 url = "1.0"
+jsonrpc-server-utils = "11.0"
 
 [dev-dependencies]
 env_logger = "0.5"

secret-store/src/lib.rs

@@ -37,6 +37,7 @@ extern crate tokio;
 extern crate tokio_io;
 extern crate tokio_service;
 extern crate url;
+extern crate jsonrpc_server_utils;
 
 #[macro_use]
 extern crate ethabi_derive;
@@ -107,7 +108,7 @@ pub fn start(client: Arc<Client>, sync: Arc<SyncProvider>, miner: Arc<Miner>, se
 
 	// prepare HTTP listener
 	let http_listener = match config.listener_address {
-		Some(listener_address) => Some(listener::http_listener::KeyServerHttpListener::start(listener_address, Arc::downgrade(&key_server), executor)?),
+		Some(listener_address) => Some(listener::http_listener::KeyServerHttpListener::start(listener_address, config.cors, Arc::downgrade(&key_server), executor)?),
 		None => None,
 	};
 

secret-store/src/listener/http_listener.rs

@@ -34,6 +34,7 @@ use traits::KeyServer;
 use serialization::{SerializableEncryptedDocumentKeyShadow, SerializableBytes, SerializablePublic};
 use types::{Error, Public, MessageHash, NodeAddress, RequestSignature, ServerKeyId,
 	EncryptedDocumentKey, EncryptedDocumentKeyShadow, NodeId};
+use jsonrpc_server_utils::cors::{self, AllowCors, AccessControlAllowOrigin};
 
 /// Key server http-requests listener. Available requests:
 /// To generate server key:							POST		/shadow/{server_key_id}/{signature}/{threshold}
@@ -45,6 +46,8 @@ use types::{Error, Public, MessageHash, NodeAddress, RequestSignature, ServerKey
 /// To generate ECDSA signature with server key:	GET			/ecdsa/{server_key_id}/{signature}/{message_hash}
 /// To change servers set:							POST		/admin/servers_set_change/{old_signature}/{new_signature} + BODY: json array of hex-encoded nodes ids
 
+type CorsDomains = Option<Vec<AccessControlAllowOrigin>>;
+
 pub struct KeyServerHttpListener {
 	_executor: Executor,
 	_handler: Arc<KeyServerSharedHttpHandler>,
@@ -77,6 +80,7 @@ enum Request {
 #[derive(Clone)]
 struct KeyServerHttpHandler {
 	handler: Arc<KeyServerSharedHttpHandler>,
+	cors: CorsDomains,
 }
 
 /// Shared http handler
@@ -84,13 +88,14 @@ struct KeyServerSharedHttpHandler {
 	key_server: Weak<KeyServer>,
 }
 
+
 impl KeyServerHttpListener {
 	/// Start KeyServer http listener
-	pub fn start(listener_address: NodeAddress, key_server: Weak<KeyServer>, executor: Executor) -> Result<Self, Error> {
+	pub fn start(listener_address: NodeAddress, cors_domains: Option<Vec<String>>, key_server: Weak<KeyServer>, executor: Executor) -> Result<Self, Error> {
 		let shared_handler = Arc::new(KeyServerSharedHttpHandler {
 			key_server: key_server,
 		});
-
+		let cors: CorsDomains = cors_domains.map(|domains| domains.into_iter().map(AccessControlAllowOrigin::from).collect());
 		let listener_address = format!("{}:{}", listener_address.address, listener_address.port).parse()?;
 		let listener = TcpListener::bind(&listener_address)?;
 
@@ -101,7 +106,7 @@ impl KeyServerHttpListener {
 			.for_each(move |socket| {
 				let http = Http::new();
 				let serve = http.serve_connection(socket,
-					KeyServerHttpHandler { handler: shared_handler2.clone() }
+					KeyServerHttpHandler { handler: shared_handler2.clone(), cors: cors.clone() }
 				).map(|_| ()).map_err(|e| {
 					warn!("Key server handler error: {:?}", e);
 				});
@@ -121,10 +126,10 @@ impl KeyServerHttpListener {
 }
 
 impl KeyServerHttpHandler {
-	fn process(self, req_method: HttpMethod, req_uri: Uri, path: &str, req_body: &[u8]) -> HttpResponse<Body> {
+	fn process(self, req_method: HttpMethod, req_uri: Uri, path: &str, req_body: &[u8], cors: AllowCors<AccessControlAllowOrigin>) -> HttpResponse<Body> {
 		match parse_request(&req_method, &path, &req_body) {
 			Request::GenerateServerKey(document, signature, threshold) => {
-				return_server_public_key(&req_uri, self.handler.key_server.upgrade()
+				return_server_public_key(&req_uri, cors, self.handler.key_server.upgrade()
 					.map(|key_server| key_server.generate_key(&document, &signature.into(), threshold))
 					.unwrap_or(Err(Error::Internal("KeyServer is already destroyed".into())))
 					.map_err(|err| {
@@ -133,7 +138,7 @@ impl KeyServerHttpHandler {
 					}))
 			},
 			Request::StoreDocumentKey(document, signature, common_point, encrypted_document_key) => {
-				return_empty(&req_uri, self.handler.key_server.upgrade()
+				return_empty(&req_uri, cors, self.handler.key_server.upgrade()
 					.map(|key_server| key_server.store_document_key(&document, &signature.into(), common_point, encrypted_document_key))
 					.unwrap_or(Err(Error::Internal("KeyServer is already destroyed".into())))
 					.map_err(|err| {
@@ -142,7 +147,7 @@ impl KeyServerHttpHandler {
 					}))
 			},
 			Request::GenerateDocumentKey(document, signature, threshold) => {
-				return_document_key(&req_uri, self.handler.key_server.upgrade()
+				return_document_key(&req_uri, cors, self.handler.key_server.upgrade()
 					.map(|key_server| key_server.generate_document_key(&document, &signature.into(), threshold))
 					.unwrap_or(Err(Error::Internal("KeyServer is already destroyed".into())))
 					.map_err(|err| {
@@ -151,7 +156,7 @@ impl KeyServerHttpHandler {
 					}))
 			},
 			Request::GetDocumentKey(document, signature) => {
-				return_document_key(&req_uri, self.handler.key_server.upgrade()
+				return_document_key(&req_uri, cors, self.handler.key_server.upgrade()
 					.map(|key_server| key_server.restore_document_key(&document, &signature.into()))
 					.unwrap_or(Err(Error::Internal("KeyServer is already destroyed".into())))
 					.map_err(|err| {
@@ -160,7 +165,7 @@ impl KeyServerHttpHandler {
 					}))
 			},
 			Request::GetDocumentKeyShadow(document, signature) => {
-				return_document_key_shadow(&req_uri, self.handler.key_server.upgrade()
+				return_document_key_shadow(&req_uri, cors, self.handler.key_server.upgrade()
 					.map(|key_server| key_server.restore_document_key_shadow(&document, &signature.into()))
 					.unwrap_or(Err(Error::Internal("KeyServer is already destroyed".into())))
 					.map_err(|err| {
@@ -169,7 +174,7 @@ impl KeyServerHttpHandler {
 					}))
 			},
 			Request::SchnorrSignMessage(document, signature, message_hash) => {
-				return_message_signature(&req_uri, self.handler.key_server.upgrade()
+				return_message_signature(&req_uri, cors, self.handler.key_server.upgrade()
 					.map(|key_server| key_server.sign_message_schnorr(&document, &signature.into(), message_hash))
 					.unwrap_or(Err(Error::Internal("KeyServer is already destroyed".into())))
 					.map_err(|err| {
@@ -178,7 +183,7 @@ impl KeyServerHttpHandler {
 					}))
 				},
 			Request::EcdsaSignMessage(document, signature, message_hash) => {
-				return_message_signature(&req_uri, self.handler.key_server.upgrade()
+				return_message_signature(&req_uri, cors, self.handler.key_server.upgrade()
 					.map(|key_server| key_server.sign_message_ecdsa(&document, &signature.into(), message_hash))
 					.unwrap_or(Err(Error::Internal("KeyServer is already destroyed".into())))
 					.map_err(|err| {
@@ -187,7 +192,7 @@ impl KeyServerHttpHandler {
 					}))
 			},
 			Request::ChangeServersSet(old_set_signature, new_set_signature, new_servers_set) => {
-				return_empty(&req_uri, self.handler.key_server.upgrade()
+				return_empty(&req_uri, cors, self.handler.key_server.upgrade()
 					.map(|key_server| key_server.change_servers_set(old_set_signature, new_set_signature, new_servers_set))
 					.unwrap_or(Err(Error::Internal("KeyServer is already destroyed".into())))
 					.map_err(|err| {
@@ -213,14 +218,21 @@ impl Service for KeyServerHttpHandler {
 	type Future = Box<Future<Item = HttpResponse<Self::ResBody>, Error=Self::Error> + Send>;
 
 	fn call(&mut self, req: HttpRequest<Body>) -> Self::Future {
-		if req.headers().contains_key(header::ORIGIN) {
+		let cors = cors::get_cors_allow_origin(
-			warn!(target: "secretstore", "Ignoring {}-request {} with Origin header", req.method(), req.uri());
+			req.headers().get(header::ORIGIN).and_then(|value| value.to_str().ok()),
-			return Box::new(future::ok(HttpResponse::builder()
+			req.headers().get(header::HOST).and_then(|value| value.to_str().ok()),
+			&self.cors
+		);
+		match cors {
+			AllowCors::Invalid => {
+				warn!(target: "secretstore", "Ignoring {}-request {} with unauthorized Origin header", req.method(), req.uri());
+				Box::new(future::ok(HttpResponse::builder()
 						.status(HttpStatusCode::NOT_FOUND)
 						.body(Body::empty())
-					.expect("Nothing to parse, cannot fail; qed")))
+						.expect("Nothing to parse, cannot fail; qed")
-		}
+					))
-
+			},
+			_ => {
 				let req_method = req.method().clone();
 				let req_uri = req.uri().clone();
 				// We cannot consume Self because of the Service trait requirement.
@@ -229,7 +241,7 @@ impl Service for KeyServerHttpHandler {
 				Box::new(req.into_body().concat2().map(move |body| {
 					let path = req_uri.path().to_string();
 					if path.starts_with("/") {
-				this.process(req_method, req_uri, &path, &body)
+						this.process(req_method, req_uri, &path, &body, cors)
 					} else {
 						warn!(target: "secretstore", "Ignoring invalid {}-request {}", req_method, req_uri);
 						HttpResponse::builder()
@@ -240,42 +252,46 @@ impl Service for KeyServerHttpHandler {
 				}))
 			}
 		}
-
+	}
-fn return_empty(req_uri: &Uri, empty: Result<(), Error>) -> HttpResponse<Body> {
-	return_bytes::<i32>(req_uri, empty.map(|_| None))
 }
 
-fn return_server_public_key(req_uri: &Uri, server_public: Result<Public, Error>) -> HttpResponse<Body> {
+fn return_empty(req_uri: &Uri, cors: AllowCors<AccessControlAllowOrigin>, empty: Result<(), Error>) -> HttpResponse<Body> {
-	return_bytes(req_uri, server_public.map(|k| Some(SerializablePublic(k))))
+	return_bytes::<i32>(req_uri, cors, empty.map(|_| None))
 }
 
-fn return_message_signature(req_uri: &Uri, signature: Result<EncryptedDocumentKey, Error>) -> HttpResponse<Body> {
+fn return_server_public_key(req_uri: &Uri, cors: AllowCors<AccessControlAllowOrigin>, server_public: Result<Public, Error>) -> HttpResponse<Body> {
-	return_bytes(req_uri, signature.map(|s| Some(SerializableBytes(s))))
+	return_bytes(req_uri, cors, server_public.map(|k| Some(SerializablePublic(k))))
 }
 
-fn return_document_key(req_uri: &Uri, document_key: Result<EncryptedDocumentKey, Error>) -> HttpResponse<Body> {
+fn return_message_signature(req_uri: &Uri, cors: AllowCors<AccessControlAllowOrigin>, signature: Result<EncryptedDocumentKey, Error>) -> HttpResponse<Body> {
-	return_bytes(req_uri, document_key.map(|k| Some(SerializableBytes(k))))
+	return_bytes(req_uri, cors, signature.map(|s| Some(SerializableBytes(s))))
 }
 
-fn return_document_key_shadow(req_uri: &Uri, document_key_shadow: Result<EncryptedDocumentKeyShadow, Error>)
+fn return_document_key(req_uri: &Uri, cors: AllowCors<AccessControlAllowOrigin>, document_key: Result<EncryptedDocumentKey, Error>) -> HttpResponse<Body> {
+	return_bytes(req_uri, cors, document_key.map(|k| Some(SerializableBytes(k))))
+}
+
+fn return_document_key_shadow(req_uri: &Uri, cors: AllowCors<AccessControlAllowOrigin>, document_key_shadow: Result<EncryptedDocumentKeyShadow, Error>)
 	-> HttpResponse<Body>
 {
-	return_bytes(req_uri, document_key_shadow.map(|k| Some(SerializableEncryptedDocumentKeyShadow {
+	return_bytes(req_uri, cors, document_key_shadow.map(|k| Some(SerializableEncryptedDocumentKeyShadow {
 		decrypted_secret: k.decrypted_secret.into(),
 		common_point: k.common_point.expect("always filled when requesting document_key_shadow; qed").into(),
-		decrypt_shadows: k.decrypt_shadows.expect("always filled when requesting document_key_shadow; qed").into_iter().map(Into::into).collect(),
+		decrypt_shadows: k.decrypt_shadows.expect("always filled when requesting document_key_shadow; qed").into_iter().map(Into::into).collect()
 	})))
 }
 
-fn return_bytes<T: Serialize>(req_uri: &Uri, result: Result<Option<T>, Error>) -> HttpResponse<Body> {
+fn return_bytes<T: Serialize>(req_uri: &Uri, cors: AllowCors<AccessControlAllowOrigin>, result: Result<Option<T>, Error>) -> HttpResponse<Body> {
 	match result {
 		Ok(Some(result)) => match serde_json::to_vec(&result) {
 			Ok(result) => {
 				let body: Body = result.into();
-				HttpResponse::builder()
+				let mut builder = HttpResponse::builder();
-					.header(header::CONTENT_TYPE, HeaderValue::from_static("application/json; charset=utf-8"))
+				builder.header(header::CONTENT_TYPE, HeaderValue::from_static("application/json; charset=utf-8"));
-					.body(body)
+				if let AllowCors::Ok(AccessControlAllowOrigin::Value(origin)) = cors {
-					.expect("Error creating http response")
+					builder.header(header::ACCESS_CONTROL_ALLOW_ORIGIN, origin.to_string());
+				}
+				builder.body(body).expect("Error creating http response")
 			},
 			Err(err) => {
 				warn!(target: "secretstore", "response to request {} has failed with: {}", req_uri, err);
@@ -286,10 +302,12 @@ fn return_bytes<T: Serialize>(req_uri: &Uri, result: Result<Option<T>, Error>) -
 			}
 		},
 		Ok(None) => {
-			HttpResponse::builder()
+			let mut builder = HttpResponse::builder();
-					.status(HttpStatusCode::OK)
+			builder.status(HttpStatusCode::OK);
-					.body(Body::empty())
+			if let AllowCors::Ok(AccessControlAllowOrigin::Value(origin)) = cors {
-					.expect("Nothing to parse, cannot fail; qed")
+				builder.header(header::ACCESS_CONTROL_ALLOW_ORIGIN, origin.to_string());
+			}
+			builder.body(Body::empty()).expect("Nothing to parse, cannot fail; qed")
 		},
 		Err(err) => return_error(err),
 	}
@@ -423,7 +441,7 @@ mod tests {
 		let key_server: Arc<KeyServer> = Arc::new(DummyKeyServer::default());
 		let address = NodeAddress { address: "127.0.0.1".into(), port: 9000 };
 		let runtime = Runtime::with_thread_count(1);
-		let listener = KeyServerHttpListener::start(address, Arc::downgrade(&key_server),
+		let listener = KeyServerHttpListener::start(address, None, Arc::downgrade(&key_server),
 			runtime.executor()).unwrap();
 		drop(listener);
 	}

secret-store/src/types/all.rs

@@ -70,6 +70,8 @@ pub struct ServiceConfiguration {
 	pub acl_check_contract_address: Option<ContractAddress>,
 	/// Cluster configuration.
 	pub cluster_config: ClusterConfiguration,
+	// Allowed CORS domains
+	pub cors: Option<Vec<String>>,
 }
 
 /// Key server cluster configuration