Refuse private ranges unconditionally; the proxy's network is never the user's

crates-server/yaak-send-proxy/README.md

@@ -35,7 +35,6 @@ arguments; `--help` lists them all.
 | --- | --- | --- |
 | `--bind` | `127.0.0.1:9227` | Listen address. `0.0.0.0:9227` inside a container. |
 | `--allowed-origins` | `*` | CORS origins, comma-separated. A hosted instance should name its web origin. |
-| `--allow-private-networks` | off | Let sends reach private, loopback and link-local addresses. **Off by default; see below.** |
 | `--max-request-bytes` | 16 MiB | Largest rendered request accepted from the tab. |
 | `--max-response-bytes` | 64 MiB | Largest upstream body relayed before the send is cut off. |
 | `--max-timeout-secs` | 60 | Ceiling on a send's timeout; a request asking for more (or none) gets this. |
@@ -47,7 +46,7 @@ arguments; `--help` lists them all.
 
 A hosted proxy is, by construction, a machine that makes HTTP requests on
 behalf of strangers. Left alone that is an open relay into whatever network it
-sits on. So by default it refuses to connect to:
+sits on. So it refuses, always, to connect to:
 
 - loopback (`127/8`, `::1`), private (`10/8`, `172.16/12`, `192.168/16`,
   `fc00::/7`), link-local (`169.254/16` — where cloud metadata lives — and
@@ -62,9 +61,9 @@ caught, and so is a `Location:` header that points at one. It also refuses body
 types that would read files on the proxy's disk (`binary`, multipart file
 fields), since no browser tab could legitimately mean those.
 
-Refusals are logged with the reason. A self-hosted instance on a private network
-that legitimately needs to reach the services next to it turns the range check
-off with `--allow-private-networks`.
+Refusals are logged with the reason. There is no switch to turn this off: the
+proxy's private network is the cloud's, not the user's, so a `localhost` or LAN
+API can never be reached through it — that is what the desktop app is for.
 
 ## Self-hosting
 

crates-server/yaak-send-proxy/src/config.rs

@@ -22,18 +22,6 @@ pub struct Config {
     )]
     pub allowed_origins: Vec<String>,
 
-    /// Allow sends to private, loopback, link-local and other non-public addresses.
-    ///
-    /// Off by default: a hosted instance must not become a relay into its own network. A
-    /// self-hosted instance on a private network legitimately needs this on to reach the
-    /// services next to it.
-    #[arg(
-        long,
-        env = "YAAK_PROXY_ALLOW_PRIVATE_NETWORKS",
-        default_value_t = false
-    )]
-    pub allow_private_networks: bool,
-
     /// Largest request the proxy accepts from the tab (the rendered request JSON, body included).
     #[arg(long, env = "YAAK_PROXY_MAX_REQUEST_BYTES", default_value_t = 16 * 1024 * 1024)]
     pub max_request_bytes: usize,

crates-server/yaak-send-proxy/src/guard.rs

@@ -20,17 +20,13 @@ use yaak_http::dns::AddressFilter;
 use yaak_http::sender::{HttpResponse, HttpResponseEvent, HttpSender};
 use yaak_http::types::SendableHttpRequest;
 
-/// The destination policy, built once from config and shared by every send.
-#[derive(Clone)]
-pub struct DestinationPolicy {
-    allow_private_networks: bool,
-}
+/// The destination policy, shared by every send: public addresses only, always. A hosted
+/// proxy's "private network" is the cloud's, not the user's, so there is no configuration
+/// that makes reaching it right.
+#[derive(Clone, Default)]
+pub struct DestinationPolicy;
 
 impl DestinationPolicy {
-    pub fn new(allow_private_networks: bool) -> Self {
-        Self { allow_private_networks }
-    }
-
     /// Check a URL before a hop is attempted: scheme and literal IPs. A hostname that passes
     /// here still has its resolved addresses checked by [`Self::address_filter`].
     pub fn check_url(&self, raw: &str) -> Result<(), String> {
@@ -57,9 +53,6 @@ impl DestinationPolicy {
     }
 
     pub fn check_ip(&self, ip: IpAddr) -> Result<(), String> {
-        if self.allow_private_networks {
-            return Ok(());
-        }
         match non_public_reason(ip) {
             Some(reason) => Err(format!(
                 "Refusing to connect to {ip}: {reason}. This proxy only sends to public addresses"
@@ -248,11 +241,8 @@ mod tests {
     }
 
     #[test]
-    fn private_networks_can_be_opted_in() {
-        let policy = DestinationPolicy::new(true);
-        assert!(policy.check_url("http://127.0.0.1/").is_ok());
-        assert!(policy.check_url("http://169.254.169.254/").is_ok());
-        let policy = DestinationPolicy::new(false);
+    fn literal_private_addresses_in_urls_are_refused() {
+        let policy = DestinationPolicy;
         assert!(policy.check_url("http://127.0.0.1/").is_err());
         assert!(policy.check_url("http://[::1]/").is_err());
         assert!(policy.check_url("http://169.254.169.254/latest/meta-data").is_err());
@@ -260,7 +250,7 @@ mod tests {
 
     #[test]
     fn only_http_schemes() {
-        let policy = DestinationPolicy::new(true);
+        let policy = DestinationPolicy;
         assert!(policy.check_url("ftp://example.com/").is_err());
         assert!(policy.check_url("file:///etc/passwd").is_err());
         assert!(policy.check_url("https://example.com/").is_ok());

crates-server/yaak-send-proxy/src/main.rs

@@ -49,7 +49,7 @@ async fn main() {
     env_logger::Builder::from_env(env_logger::Env::default().default_filter_or("info")).init();
     let config = Config::parse();
 
-    let policy = DestinationPolicy::new(config.allow_private_networks);
+    let policy = DestinationPolicy;
     let state = AppState {
         limits: Arc::new(SendLimits {
             policy,
@@ -81,8 +81,7 @@ async fn main() {
         std::process::exit(1);
     });
     info!(
-        "yaak-send-proxy listening on http://{bind} (private networks: {}, rate limit: {}/min)",
-        if state.config.allow_private_networks { "allowed" } else { "refused" },
+        "yaak-send-proxy listening on http://{bind} (rate limit: {}/min)",
         state.config.rate_limit_per_minute,
     );
 
@@ -108,7 +107,6 @@ async fn health(State(state): State<AppState>) -> impl IntoResponse {
     Json(json!({
         "ok": true,
         "version": env!("CARGO_PKG_VERSION"),
-        "privateNetworks": state.config.allow_private_networks,
         "maxResponseBytes": state.config.max_response_bytes,
         "maxTimeoutSecs": state.config.max_timeout_secs,
     }))