systemprompt_api/services/middleware/
client_addr.rs

1//! Client-address resolution that does not blindly trust hop headers.
2//!
3//! [`resolve_client_ip`] is the single helper every middleware that
4//! cares about the originating client (rate-limiter, IP banlist,
5//! bot-scoring, abuse heuristics) must use. The contract:
6//!
7//! 1. If the immediate socket peer (`ConnectInfo<SocketAddr>`) is not contained
8//!    in `trusted_proxies`, return the peer address. Hop headers are ignored
9//!    entirely — they are untrusted in this case.
10//! 2. If the peer is trusted, walk `X-Forwarded-For` right-to-left and take the
11//!    first hop that is itself outside `trusted_proxies`. That hop is the
12//!    closest entity our proxy chain still sees, and the earliest one a client
13//!    could have spoofed.
14//! 3. If the chain is empty or every hop is trusted, fall back to the peer
15//!    address.
16//!
17//! `X-Real-IP`, `Fly-Client-IP`, and `CF-Connecting-IP` are honoured only
18//! under rule 2's trust gate; otherwise they are ignored.
19//!
20//! The trusted-proxy CIDR set is parsed and validated when the profile
21//! loads (`ServerConfig::trusted_proxies` deserialises to `Vec<IpNet>`);
22//! an invalid entry fails boot rather than being silently dropped, so this
23//! resolver only ever sees a validated set.
24//!
25//! A request arriving through a proxy the server does not trust has its
26//! forwarded client-IP headers discarded and the peer's own address used
27//! instead. That is almost always a misconfiguration: something is adding
28//! `X-Forwarded-For`, so a proxy is in the path, but its address is absent
29//! from `server.trusted_proxies`, and every client behind it then resolves to
30//! one address and shares one rate-limit bucket, one ban entry and one set of
31//! abuse heuristics. The warning is not gated on the peer being in a private
32//! range: a reverse proxy on a host network has a public address. Whether the
33//! peer is public or private has
34//! no bearing on whether the operator wants to know.
35//!
36//! Copyright (c) systemprompt.io — Business Source License 1.1.
37//! See <https://systemprompt.io> for licensing details.
38
39use std::convert::Infallible;
40use std::future::{Future, ready};
41use std::net::{IpAddr, SocketAddr};
42
43use axum::extract::{ConnectInfo, FromRequestParts};
44use axum::http::HeaderMap;
45use axum::http::request::Parts;
46use ipnet::IpNet;
47
48fn is_trusted(addr: IpAddr, trusted: &[IpNet]) -> bool {
49    trusted.iter().any(|net| net.contains(&addr))
50}
51
52#[must_use]
53pub fn resolve_client_ip(
54    headers: &HeaderMap,
55    connect_info: Option<&ConnectInfo<SocketAddr>>,
56    trusted: &[IpNet],
57) -> Option<IpAddr> {
58    let peer_ip = connect_info.map(|c| c.0.ip())?;
59
60    if !is_trusted(peer_ip, trusted) {
61        return Some(peer_ip);
62    }
63
64    if let Some(xff) = headers.get("x-forwarded-for").and_then(|v| v.to_str().ok()) {
65        let hops: Vec<&str> = xff
66            .split(',')
67            .map(str::trim)
68            .filter(|s| !s.is_empty())
69            .collect();
70        for hop in hops.iter().rev() {
71            if let Ok(addr) = hop.parse::<IpAddr>()
72                && !is_trusted(addr, trusted)
73            {
74                return Some(addr);
75            }
76        }
77    }
78
79    for header in ["x-real-ip", "fly-client-ip", "cf-connecting-ip"] {
80        if let Some(raw) = headers.get(header).and_then(|v| v.to_str().ok())
81            && let Ok(addr) = raw.trim().parse::<IpAddr>()
82            && !is_trusted(addr, trusted)
83        {
84            return Some(addr);
85        }
86    }
87
88    Some(peer_ip)
89}
90
91#[must_use]
92pub fn forwarded_headers_ignored(headers: &HeaderMap, peer_ip: IpAddr, trusted: &[IpNet]) -> bool {
93    !is_trusted(peer_ip, trusted) && headers.contains_key("x-forwarded-for")
94}
95
96#[must_use]
97pub fn resolve_client_ip_from_config(
98    headers: &HeaderMap,
99    connect_info: Option<&ConnectInfo<SocketAddr>>,
100) -> Option<IpAddr> {
101    let trusted = systemprompt_manifest::Config::get()
102        .map(|c| c.trusted_proxies.clone())
103        .unwrap_or_default();
104    resolve_client_ip(headers, connect_info, &trusted)
105}
106
107#[must_use]
108pub fn client_ip_from_request(request: &axum::extract::Request) -> Option<IpAddr> {
109    resolve_client_ip_from_config(
110        request.headers(),
111        request.extensions().get::<ConnectInfo<SocketAddr>>(),
112    )
113}
114
115#[derive(Debug, Clone, Copy)]
116pub struct ClientIp(pub Option<IpAddr>);
117
118impl<S: Sync> FromRequestParts<S> for ClientIp {
119    type Rejection = Infallible;
120
121    fn from_request_parts(
122        parts: &mut Parts,
123        _state: &S,
124    ) -> impl Future<Output = Result<Self, Infallible>> + Send {
125        let resolved = resolve_client_ip_from_config(
126            &parts.headers,
127            parts.extensions.get::<ConnectInfo<SocketAddr>>(),
128        );
129        ready(Ok(Self(resolved)))
130    }
131}
systemprompt_api/services/middleware/client_addr.rs

systemprompt_api/services/middleware/
client_addr.rs
