Refine Rust architecture boundaries

2026-06-21 08:58:32 +00:00
parent a31862aeeb
commit 7df9b48513
18 changed files with 1376 additions and 1052 deletions
@@ -0,0 +1,311 @@
+use std::{convert::Infallible, time::Duration};
+
+use axum::{
+    Json,
+    http::{
+        HeaderMap, HeaderValue, StatusCode,
+        header::{self, ACCEPT, HeaderName},
+    },
+    response::{
+        IntoResponse, Response,
+        sse::{Event, KeepAlive, Sse},
+    },
+};
+use futures_util::stream;
+use serde_json::Value;
+
+use crate::jsonrpc::{
+    CURRENT_PROTOCOL_VERSION, DEFAULT_PROTOCOL_VERSION, negotiated_protocol_version,
+};
+
+pub(super) const HEADER_MCP_SESSION_ID: &str = "MCP-Session-Id";
+pub(super) const HEADER_MCP_PROTOCOL_VERSION: &str = "MCP-Protocol-Version";
+pub(super) const HEADER_X_REQUEST_ID: HeaderName = HeaderName::from_static("x-request-id");
+const MAX_REQUEST_ID_LEN: usize = 128;
+
+#[derive(Clone, Copy)]
+pub(super) enum ResponseMode {
+    Json,
+    Sse,
+}
+
+#[derive(Clone)]
+pub(super) struct AllowedOrigins {
+    public_origin: Option<String>,
+}
+
+impl AllowedOrigins {
+    pub(super) fn new(public_base_url: Option<String>) -> Self {
+        Self {
+            public_origin: public_base_url.and_then(|value| extract_origin(&value)),
+        }
+    }
+
+    pub(super) fn is_allowed(&self, origin: &str) -> bool {
+        if origin.starts_with("http://localhost")
+            || origin.starts_with("http://127.0.0.1")
+            || origin.starts_with("https://localhost")
+            || origin.starts_with("https://127.0.0.1")
+        {
+            return true;
+        }
+
+        match &self.public_origin {
+            Some(public_origin) => public_origin == origin,
+            None => false,
+        }
+    }
+}
+
+pub(super) fn validate_origin(
+    allowed_origins: &AllowedOrigins,
+    headers: &HeaderMap,
+) -> Result<(), StatusCode> {
+    let Some(origin) = headers.get(header::ORIGIN) else {
+        return Ok(());
+    };
+    let Ok(origin) = origin.to_str() else {
+        return Err(StatusCode::FORBIDDEN);
+    };
+
+    if allowed_origins.is_allowed(origin) {
+        return Ok(());
+    }
+
+    Err(StatusCode::FORBIDDEN)
+}
+
+pub(super) fn negotiate_post_response_mode(
+    headers: &HeaderMap,
+) -> Result<ResponseMode, StatusCode> {
+    let Some(accept) = headers.get(ACCEPT) else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+    let Ok(accept) = accept.to_str() else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+
+    let mut saw_json = false;
+    let mut saw_sse = false;
+    let mut preferred = None;
+
+    for part in accept.split(',') {
+        let media_type = part
+            .split(';')
+            .next()
+            .unwrap_or_default()
+            .trim()
+            .to_ascii_lowercase();
+
+        match media_type.as_str() {
+            "application/json" => {
+                saw_json = true;
+                if preferred.is_none() {
+                    preferred = Some(ResponseMode::Json);
+                }
+            }
+            "text/event-stream" => {
+                saw_sse = true;
+                if preferred.is_none() {
+                    preferred = Some(ResponseMode::Sse);
+                }
+            }
+            _ => {}
+        }
+    }
+
+    if saw_json || saw_sse {
+        return preferred.ok_or(StatusCode::NOT_ACCEPTABLE);
+    }
+
+    Err(StatusCode::NOT_ACCEPTABLE)
+}
+
+pub(super) fn validate_get_accept_header(headers: &HeaderMap) -> Result<(), StatusCode> {
+    let Some(accept) = headers.get(ACCEPT) else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+    let Ok(accept) = accept.to_str() else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+
+    if accept
+        .split(',')
+        .map(|part| {
+            part.split(';')
+                .next()
+                .unwrap_or_default()
+                .trim()
+                .to_ascii_lowercase()
+        })
+        .any(|media_type| media_type == "text/event-stream")
+    {
+        return Ok(());
+    }
+
+    Err(StatusCode::NOT_ACCEPTABLE)
+}
+
+pub(super) fn protocol_version_from_headers(headers: &HeaderMap) -> Result<String, StatusCode> {
+    let Some(version) = headers.get(HEADER_MCP_PROTOCOL_VERSION) else {
+        return Ok(DEFAULT_PROTOCOL_VERSION.to_owned());
+    };
+    let Ok(version) = version.to_str() else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+
+    if negotiated_protocol_version(version).is_some() {
+        return Ok(version.to_owned());
+    }
+
+    Err(StatusCode::BAD_REQUEST)
+}
+
+pub(super) fn validate_session_protocol_version(
+    headers: &HeaderMap,
+    negotiated_session_version: &str,
+) -> Result<(), StatusCode> {
+    let Some(version) = headers.get(HEADER_MCP_PROTOCOL_VERSION) else {
+        return Ok(());
+    };
+    let Ok(version) = version.to_str() else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+
+    if negotiated_protocol_version(version).is_none() {
+        return Err(StatusCode::BAD_REQUEST);
+    }
+
+    if version != negotiated_session_version {
+        return Err(StatusCode::BAD_REQUEST);
+    }
+
+    Ok(())
+}
+
+pub(super) fn session_id_from_headers(headers: &HeaderMap) -> Result<Option<String>, StatusCode> {
+    let Some(session_id) = headers.get(HEADER_MCP_SESSION_ID) else {
+        return Ok(None);
+    };
+    let Ok(session_id) = session_id.to_str() else {
+        return Err(StatusCode::BAD_REQUEST);
+    };
+
+    Ok(Some(session_id.to_owned()))
+}
+
+pub(super) fn json_response(
+    status: StatusCode,
+    payload: Value,
+    session_id: Option<&str>,
+    protocol_version: Option<&str>,
+) -> Response {
+    let mut response = (status, Json(payload)).into_response();
+
+    if let Some(session_id) = session_id {
+        response.headers_mut().insert(
+            HEADER_MCP_SESSION_ID,
+            HeaderValue::from_str(session_id)
+                .unwrap_or_else(|_| HeaderValue::from_static("invalid")),
+        );
+    }
+
+    if let Some(protocol_version) = protocol_version {
+        response.headers_mut().insert(
+            HEADER_MCP_PROTOCOL_VERSION,
+            HeaderValue::from_str(protocol_version)
+                .unwrap_or_else(|_| HeaderValue::from_static(CURRENT_PROTOCOL_VERSION)),
+        );
+    }
+
+    response
+}
+
+pub(super) fn transport_response(
+    status: StatusCode,
+    payload: Value,
+    response_mode: ResponseMode,
+    session_id: Option<&str>,
+    protocol_version: Option<&str>,
+) -> Response {
+    if status == StatusCode::OK && matches!(response_mode, ResponseMode::Sse) {
+        let payload = payload.to_string();
+        let stream = stream::once(async move { Ok(Event::default().data(payload)) });
+
+        return sse_response(status, stream, session_id, protocol_version);
+    }
+
+    json_response(status, payload, session_id, protocol_version)
+}
+
+pub(super) fn with_request_id_header(mut response: Response, request_id: &str) -> Response {
+    if let Ok(value) = HeaderValue::from_str(request_id) {
+        response.headers_mut().insert(HEADER_X_REQUEST_ID, value);
+    }
+    response
+}
+
+pub(super) fn sse_response<S>(
+    status: StatusCode,
+    stream: S,
+    session_id: Option<&str>,
+    protocol_version: Option<&str>,
+) -> Response
+where
+    S: futures_util::stream::Stream<Item = Result<Event, Infallible>> + Send + 'static,
+{
+    let mut response = (
+        status,
+        Sse::new(stream).keep_alive(KeepAlive::new().interval(Duration::from_secs(15))),
+    )
+        .into_response();
+
+    if let Some(session_id) = session_id {
+        response.headers_mut().insert(
+            HEADER_MCP_SESSION_ID,
+            HeaderValue::from_str(session_id)
+                .unwrap_or_else(|_| HeaderValue::from_static("invalid")),
+        );
+    }
+
+    if let Some(protocol_version) = protocol_version {
+        response.headers_mut().insert(
+            HEADER_MCP_PROTOCOL_VERSION,
+            HeaderValue::from_str(protocol_version)
+                .unwrap_or_else(|_| HeaderValue::from_static(CURRENT_PROTOCOL_VERSION)),
+        );
+    }
+
+    response
+}
+
+pub(super) fn resolve_request_id(headers: &HeaderMap) -> String {
+    headers
+        .get(&HEADER_X_REQUEST_ID)
+        .and_then(|value| value.to_str().ok())
+        .map(str::trim)
+        .filter(|value| is_valid_request_id(value))
+        .map(ToOwned::to_owned)
+        .unwrap_or_else(|| uuid::Uuid::now_v7().to_string())
+}
+
+pub(super) fn is_valid_request_id(value: &str) -> bool {
+    !value.is_empty()
+        && value.len() <= MAX_REQUEST_ID_LEN
+        && value
+            .bytes()
+            .all(|byte| matches!(byte, 0x21..=0x7e) && byte != b',' && byte != b';')
+}
+
+pub(super) fn extract_origin(url: &str) -> Option<String> {
+    let mut parts = url.split('/');
+    let scheme = parts.next()?;
+    let empty = parts.next()?;
+    let authority = parts.next()?;
+
+    if empty.is_empty() {
+        return Some(format!("{scheme}//{authority}"));
+    }
+
+    None
+}