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|
//! Pages of other origins reading this node: the dashboards of other members, which a
//! page subscribes to for their own links and messages (`/admin/dashboard/links/own`,
//! `/admin/dashboard/messages/own/events`, and one written out), refreshing its
//! token on any node (`/auth/refresh`, `/auth/whoami`). Only those endpoints, only for
//! the origins of the dashboards the member list names and those of `--cors-origins`,
//! and without credentials: a page sends its token itself (`Authorization: Bearer`),
//! so no cookie or password crosses origins (`access.md`, Tokens).
use axum::{
body::Body,
extract::State,
http::{HeaderValue, Method, Request, StatusCode, header},
response::{IntoResponse, Response},
};
use crate::state::AppState;
use crate::swarm::members;
/// The endpoints other origins may call.
fn open(path: &str) -> bool {
// A message written out (`/admin/dashboard/messages/own/{seq}`).
let message = path
.strip_prefix("/admin/dashboard/messages/own/")
.is_some_and(|seq| !seq.is_empty() && seq.bytes().all(|byte| byte.is_ascii_digit()));
message
|| matches!(
path,
"/admin/dashboard/links/own"
| "/admin/dashboard/links/own/events"
| "/admin/dashboard/messages/own/events"
| "/auth/refresh"
| "/auth/whoami"
)
}
/// `url`'s origin (`scheme://host[:port]`), if it is a URL with one.
fn origin_of(url: &str) -> Option<String> {
let parsed = url::Url::parse(url).ok()?;
let origin = parsed.origin();
origin.is_tuple().then(|| origin.ascii_serialization())
}
/// Whether pages of `origin` may call `open` endpoints: a member's dashboard's, or one
/// of `--cors-origins`.
async fn allowed(state: &AppState, origin: &str) -> bool {
if state.cors_origins.iter().any(|allowed| allowed == origin) {
return true;
}
let replica = state.doc.read().await;
members::members(&replica.doc).iter().any(|member| {
members::dashboard(&replica.doc, member)
.and_then(|url| origin_of(&url))
.is_some_and(|theirs| theirs == origin)
})
}
/// Answers a preflight (`OPTIONS` with `Access-Control-Request-Method`) to an open
/// endpoint from an allowed origin, and adds the CORS headers to the answers of the
/// others from there; leaves everything else as it is (a browser then keeps a page of
/// another origin from reading it). Outside authentication: a preflight brings no
/// credentials.
pub(crate) async fn cors(
State(state): State<AppState>,
request: Request<Body>,
next: axum::middleware::Next,
) -> Response {
let origin = request
.headers()
.get(header::ORIGIN)
.and_then(|value| value.to_str().ok())
.map(str::to_owned);
let Some(origin) = origin.filter(|_| open(request.uri().path())) else {
return next.run(request).await;
};
if !allowed(&state, &origin).await {
return next.run(request).await;
}
let Ok(origin) = HeaderValue::from_str(&origin) else {
return next.run(request).await;
};
let preflight = request.method() == Method::OPTIONS
&& request
.headers()
.contains_key(header::ACCESS_CONTROL_REQUEST_METHOD);
// Chrome's Private Network Access: a page on a public origin reaching a private
// address asks first.
let private = request
.headers()
.get("access-control-request-private-network")
.is_some_and(|value| value == "true");
let mut response = if preflight {
let mut response = StatusCode::NO_CONTENT.into_response();
let headers = response.headers_mut();
headers.insert(
header::ACCESS_CONTROL_ALLOW_METHODS,
HeaderValue::from_static("GET, POST"),
);
headers.insert(
header::ACCESS_CONTROL_ALLOW_HEADERS,
HeaderValue::from_static("authorization, content-type"),
);
headers.insert(
header::ACCESS_CONTROL_MAX_AGE,
HeaderValue::from_static("600"),
);
if private {
headers.insert(
"access-control-allow-private-network",
HeaderValue::from_static("true"),
);
}
response
} else {
next.run(request).await
};
let headers = response.headers_mut();
headers.insert(header::ACCESS_CONTROL_ALLOW_ORIGIN, origin);
headers.append(header::VARY, HeaderValue::from_static("Origin"));
response
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn origins() {
assert_eq!(
origin_of("https://a.example.org/admin/dashboard").as_deref(),
Some("https://a.example.org")
);
assert_eq!(
origin_of("http://10.0.0.1:3000/admin/dashboard").as_deref(),
Some("http://10.0.0.1:3000")
);
assert_eq!(
origin_of("https://a.example.org:443/").as_deref(),
Some("https://a.example.org")
);
assert_eq!(origin_of("not a url"), None);
}
#[test]
fn only_some_endpoints() {
assert!(open("/admin/dashboard/links/own"));
assert!(open("/admin/dashboard/messages/own/42"));
assert!(!open("/admin/dashboard/messages/own/x"));
assert!(open("/auth/refresh"));
assert!(!open("/auth/login"));
assert!(!open("/store"));
assert!(!open("/admin/dashboard/state"));
}
}
|
