fix(rpc): remove non-standard "jsonrpc: 1.0" from lightwalletd

zebrad/src/components/rpc.rs

@@ -1,8 +1,9 @@
 //! An RPC endpoint.
 
+use futures::TryStreamExt;
+use hyper::{body::Bytes, Body};
 use jsonrpc_core;
-
-use jsonrpc_http_server::ServerBuilder;
+use jsonrpc_http_server::{DomainsValidation, RequestMiddleware, ServerBuilder};
 
 use zebra_rpc::rpc::{Rpc, RpcImpl};
 
@@ -24,7 +25,12 @@ impl RpcServer {
             io.extend_with(RpcImpl.to_delegate());
 
             let server = ServerBuilder::new(io)
+                // TODO: use the same tokio executor as the rest of Zebra
+                //.event_loop_executor(tokio::runtime::Handle::current())
                 .threads(1)
+                // TODO: if we enable this security check, does lightwalletd still work?
+                .allowed_hosts(DomainsValidation::Disabled)
+                .request_middleware(FixHttpRequestMiddleware)
                 .start_http(&config.listen_addr)
                 .expect("Unable to start RPC server");
 
@@ -35,3 +41,72 @@ impl RpcServer {
         RpcServer {}
     }
 }
+
+/// HTTP [`RequestMiddleware`] with compatibility wrokarounds.
+///
+/// This middleware makes the following changes to requests:
+///
+/// ## JSON RPC 1.0 `jsonrpc` field
+///
+/// Removes "jsonrpc: 1.0" fields from requests,
+/// because the "jsonrpc" field was only added in JSON-RPC 2.0.
+///
+/// <http://www.simple-is-better.org/rpc/#differences-between-1-0-and-2-0>
+//
+// TODO: put this HTTP middleware in a separate module
+#[derive(Copy, Clone, Debug, Default, Eq, PartialEq)]
+pub struct FixHttpRequestMiddleware;
+
+impl RequestMiddleware for FixHttpRequestMiddleware {
+    fn on_request(
+        &self,
+        request: hyper::Request<hyper::Body>,
+    ) -> jsonrpc_http_server::RequestMiddlewareAction {
+        let request = request.map(|body| {
+            let body = body.map_ok(|data| {
+                // To simplify data handling, we assume that any search strings won't be split
+                // across multiple `Bytes` data buffers.
+                //
+                // To simplify error handling, Zebra only supports valid UTF-8 requests,
+                // and uses lossy UTF-8 conversion.
+                //
+                // JSON-RPC requires all requests to be valid UTF-8.
+                // The lower layers should reject invalid requests with lossy changes.
+                // But if they accept some lossy changes, that's ok,
+                // because the request was non-standard anyway.
+                //
+                // We're not concerned about performance here, so we just clone the Cow<str>
+                let data = String::from_utf8_lossy(data.as_ref()).to_string();
+
+                // Fix up the request.
+                let data = Self::remove_json_1_fields(data);
+
+                Bytes::from(data)
+            });
+
+            Body::wrap_stream(body)
+        });
+
+        jsonrpc_http_server::RequestMiddlewareAction::Proceed {
+            // TODO: if we enable this security check, does lightwalletd still work?
+            should_continue_on_invalid_cors: true,
+            request,
+        }
+    }
+}
+
+impl FixHttpRequestMiddleware {
+    /// Remove any "jsonrpc: 1.0" fields in `data`, and return the resulting string.
+    pub fn remove_json_1_fields(data: String) -> String {
+        // Replace "jsonrpc = 1.0":
+        // - at the start or middle of a list, and
+        // - at the end of a list;
+        // with no spaces (lightwalletd format), and spaces after separators (example format).
+        //
+        // TODO: replace this with a regular expression if we see errors from lightwalletd.
+        data.replace("\"jsonrpc\":\"1.0\",", "")
+            .replace("\"jsonrpc\": \"1.0\",", "")
+            .replace(",\"jsonrpc\":\"1.0\"", "")
+            .replace(", \"jsonrpc\": \"1.0\"", "")
+    }
+}