Add runtime config toggle to enable V1

Add an `enable_v1` runtime option to both payjoin-directory and
payjoin-mailroom that controls whether V1 protocol requests are
accepted. Defaults to false (V2-only) and must be explicitly enabled
in the operator's configuration.

When disabled, V1 POST requests return a `version-unsupported` BIP78
error and V1 PUT responses via OHTTP are silently dropped.

Author: DanGould

payjoin-directory/src/config.rs

@@ -16,6 +16,8 @@ pub struct Config {
     pub timeout: Duration,
     pub storage_dir: PathBuf,
     pub ohttp_keys: PathBuf, // TODO OhttpConfig struct with rotation params, etc
+    #[serde(default)]
+    pub enable_v1: bool,
     #[cfg(feature = "acme")]
     pub acme: Option<AcmeConfig>,
 }
@@ -54,6 +56,7 @@ impl Config {
             timeout: Duration::from_secs(built_config.get("timeout")?),
             storage_dir: built_config.get("storage_dir")?,
             ohttp_keys: built_config.get("ohttp_keys")?,
+            enable_v1: built_config.get("enable_v1").unwrap_or(false),
             #[cfg(feature = "acme")]
             acme: if built_config.get_table("acme").is_ok() {
                 Some(AcmeConfig {

payjoin-directory/src/lib.rs

@@ -37,6 +37,8 @@ const V1_MAX_BUFFER_SIZE: usize = 65536;
 const V1_REJECT_RES_JSON: &str =
     r#"{{"errorCode": "original-psbt-rejected ", "message": "Body is not a string"}}"#;
 const V1_UNAVAILABLE_RES_JSON: &str = r#"{{"errorCode": "unavailable", "message": "V2 receiver offline. V1 sends require synchronous communications."}}"#;
+const V1_VERSION_UNSUPPORTED_RES_JSON: &str =
+    r#"{"errorCode": "version-unsupported", "supported": [2], "message": "V1 is not supported"}"#;
 
 pub(crate) mod db;
 
@@ -68,6 +70,7 @@ pub struct Service<D: Db> {
     db: D,
     ohttp: ohttp::Server,
     sentinel_tag: SentinelTag,
+    enable_v1: bool,
 }
 
 impl<D: Db, B> tower::Service<Request<B>> for Service<D>
@@ -91,8 +94,8 @@ where
 }
 
 impl<D: Db> Service<D> {
-    pub fn new(db: D, ohttp: ohttp::Server, sentinel_tag: SentinelTag) -> Self {
-        Self { db, ohttp, sentinel_tag }
+    pub fn new(db: D, ohttp: ohttp::Server, sentinel_tag: SentinelTag, enable_v1: bool) -> Self {
+        Self { db, ohttp, sentinel_tag, enable_v1 }
     }
 
     #[cfg(feature = "_manual-tls")]
@@ -214,7 +217,7 @@ impl<D: Db> Service<D> {
                 self.handle_ohttp_gateway_get(&query).await,
             (Method::POST, ["", ""]) => self.handle_ohttp_gateway(body).await,
             (Method::GET, ["", "ohttp-keys"]) => self.get_ohttp_keys().await,
-            (Method::POST, ["", id]) => self.post_fallback_v1(id, query, body).await,
+            (Method::POST, ["", id]) => self.handle_post_v1(id, query, body).await,
             (Method::GET, ["", "health"]) => health_check().await,
             (Method::GET, ["", ""]) => handle_directory_home_path().await,
             _ => Ok(not_found()),
@@ -227,6 +230,28 @@ impl<D: Db> Service<D> {
         Ok(response)
     }
 
+    /// Route POST /{id}: forward to V1 fallback when enabled, otherwise reject.
+    async fn handle_post_v1<B>(
+        &self,
+        id: &str,
+        query: String,
+        body: B,
+    ) -> Result<Response<BoxBody<Bytes, hyper::Error>>, HandlerError>
+    where
+        B: Body<Data = Bytes> + Send + 'static,
+        B::Error: Into<BoxError>,
+    {
+        if self.enable_v1 {
+            self.post_fallback_v1(id, query, body).await
+        } else {
+            let _ = (id, query, body);
+            Ok(Response::builder()
+                .status(StatusCode::BAD_REQUEST)
+                .header(CONTENT_TYPE, "application/json")
+                .body(full(V1_VERSION_UNSUPPORTED_RES_JSON))?)
+        }
+    }
+
     /// Handle an encapsulated OHTTP request and return an encapsulated response
     async fn handle_ohttp_gateway<B>(
         &self,
@@ -304,7 +329,7 @@ impl<D: Db> Service<D> {
         match (parts.method, path_segments.as_slice()) {
             (Method::POST, &["", id]) => self.post_mailbox(id, body).await,
             (Method::GET, &["", id]) => self.get_mailbox(id).await,
-            (Method::PUT, &["", id]) => self.put_payjoin_v1(id, body).await,
+            (Method::PUT, &["", id]) if self.enable_v1 => self.put_payjoin_v1(id, body).await,
             _ => Ok(not_found()),
         }
     }

payjoin-directory/src/main.rs

@@ -29,7 +29,7 @@ async fn main() -> Result<(), BoxError> {
         .await
         .expect("Failed to initialize persistent storage");
 
-    let service = Service::new(db, ohttp.into(), SentinelTag::new([0u8; 32]));
+    let service = Service::new(db, ohttp.into(), SentinelTag::new([0u8; 32]), config.enable_v1);
 
     let listener = TcpListener::bind(config.listen_addr).await?;
 

payjoin-mailroom/src/config.rs

@@ -12,6 +12,7 @@ pub struct Config {
     pub storage_dir: PathBuf,
     #[serde(deserialize_with = "deserialize_duration_secs")]
     pub timeout: Duration,
+    pub enable_v1: bool,
     #[cfg(feature = "telemetry")]
     pub telemetry: Option<TelemetryConfig>,
     #[cfg(feature = "acme")]
@@ -58,6 +59,7 @@ impl Default for Config {
             listener: "[::]:8080".parse().expect("valid default listener address"),
             storage_dir: PathBuf::from("./data"),
             timeout: Duration::from_secs(30),
+            enable_v1: false,
             #[cfg(feature = "telemetry")]
             telemetry: None,
             #[cfg(feature = "acme")]
@@ -75,11 +77,17 @@ where
 }
 
 impl Config {
-    pub fn new(listener: ListenerAddress, storage_dir: PathBuf, timeout: Duration) -> Self {
+    pub fn new(
+        listener: ListenerAddress,
+        storage_dir: PathBuf,
+        timeout: Duration,
+        enable_v1: bool,
+    ) -> Self {
         Self {
             listener,
             storage_dir,
             timeout,
+            enable_v1,
             #[cfg(feature = "telemetry")]
             telemetry: None,
             #[cfg(feature = "acme")]

payjoin-mailroom/src/lib.rs

@@ -167,7 +167,7 @@ async fn init_directory(
     let ohttp_keys_dir = config.storage_dir.join("ohttp-keys");
     let ohttp_config = init_ohttp_config(&ohttp_keys_dir)?;
 
-    Ok(payjoin_directory::Service::new(db, ohttp_config.into(), sentinel_tag))
+    Ok(payjoin_directory::Service::new(db, ohttp_config.into(), sentinel_tag, config.enable_v1))
 }
 
 fn init_ohttp_config(
@@ -260,6 +260,7 @@ mod tests {
             "[::]:0".parse().expect("valid listener address"),
             tempdir.path().to_path_buf(),
             Duration::from_secs(2),
+            false,
         );
 
         let mut root_store = RootCertStore::empty();
@@ -284,7 +285,7 @@ mod tests {
 
         // Make a request through the relay that targets this same instance's directory.
         // The path format is /{gateway_url} where gateway_url points back to ourselves.
-        let ohttp_req_url = format!("{}/{}", base_url, base_url);
+        let ohttp_req_url = format!("{base_url}/{base_url}");
 
         let response = client
             .post(&ohttp_req_url)
@@ -354,6 +355,7 @@ mod tests {
             "[::]:0".parse().expect("valid listener address"),
             tempdir.path().to_path_buf(),
             Duration::from_secs(2),
+            false,
         );
 
         let sentinel_tag = generate_sentinel_tag();

payjoin-test-utils/src/lib.rs

@@ -121,6 +121,7 @@ pub async fn init_directory(
         "[::]:0".parse().expect("valid listener address"),
         tempdir.path().to_path_buf(),
         Duration::from_secs(2),
+        true,
     );
 
     let tls_config = RustlsConfig::from_der(vec![local_cert_key.0], local_cert_key.1).await?;
@@ -148,6 +149,7 @@ async fn init_ohttp_relay(
         "[::]:0".parse().expect("valid listener address"),
         tempdir.path().to_path_buf(),
         Duration::from_secs(2),
+        false,
     );
 
     let (port, handle) = payjoin_mailroom::serve_manual_tls(config, None, root_store)