Use when an Axum app must decide whether an already-authenticated user is allowed to reach a route: protecting an /admin section, gating an endpoint behind a role, or enforcing a fine-grained permission like users:write. Prevents applying the guard with .layer() instead of .route_layer() (which turns a genuine 404 into a 401 and leaks which routes exist), prevents returning 401 on a failed authorization check when the answer is 403, prevents hardcoding a role hierarchy into every endpoint, prevents re-verifying the token inside a guard extractor, and prevents the wrong middleware argument order. Covers role-based and permission-based access control as from_fn and from_fn_with_state middleware applied with route_layer, the 401-versus-403 status rule, the layer-versus-route_layer decision, and the newtype guard extractor pattern (AdminClaims) with its FromRequestParts impl in both Axum 0.7 and 0.8 form. Keywords: axum authorization, RBAC, role-based access control, permission check, from_fn, from_fn_with_state,
Instrucciones de origen · Vista previa de solo lectura
name
axum-impl-authorization
description
Use when an Axum app must decide whether an already-authenticated user is allowed to reach a route: protecting an /admin section, gating an endpoint behind a role, or enforcing a fine-grained permission like users:write. Prevents applying the guard with .layer() instead of .route_layer() (which turns a genuine 404 into a 401 and leaks which routes exist), prevents returning 401 on a failed authorization check when the answer is 403, prevents hardcoding a role hierarchy into every endpoint, prevents re-verifying the token inside a guard extractor, and prevents the wrong middleware argument order. Covers role-based and permission-based access control as from_fn and from_fn_with_state middleware applied with route_layer, the 401-versus-403 status rule, the layer-versus-route_layer decision, and the newtype guard extractor pattern (AdminClaims) with its FromRequestParts impl in both Axum 0.7 and 0.8 form. Keywords: axum authorization, RBAC, role-based access control, permission check, from_fn, from_fn_with_state, route_layer, layer, Next, FromRequestParts, AdminClaims, guard extractor, middleware guard, 403 Forbidden, 401 Unauthorized, 404 leak, my 404 returns 401, auth guard returns 401 not 404, forbidden vs unauthorized, route exists but forbidden, how do I protect a route, how do I require admin, how do I check permissions, who can access this endpoint, protect /admin routes.
license
MIT
compatibility
Designed for Claude Code. Requires Axum 0.7,0.8.
metadata
{"author":"OpenAEC-Foundation","version":"1.0"}
axum-impl-authorization
Overview
Authorization answers "is this known user allowed to do this". It is a
separate concern from authentication, which answers "who are you".
Authentication is handled by axum-impl-auth-jwt and produces a verified
Claims value. Authorization always runs AFTER authentication and reads that
Claims value.
Axum has no built-in authorization. It provides the building blocks:
FromRequestParts extractors, from_fn and from_fn_with_state middleware,
and the route_layer application method. There are two mechanisms, and they
are NOT interchangeable:
Middleware guard: from_fn or from_fn_with_state applied with
route_layer. Protects a GROUP of routes. The requirement lives on the
router.
Newtype guard extractor: a custom FromRequestParts type such as
AdminClaims. Protects a SINGLE handler. The requirement lives in the
handler signature.
Two rules dominate this skill:
A failed authorization check ALWAYS returns 403 Forbidden, NEVER 401.
A guard is ALWAYS applied with .route_layer(), NEVER .layer().
The authorization mechanisms are version-stable: from_fn,
from_fn_with_state, Next, route_layer, and layer have the same shape
in Axum 0.7 and 0.8. Only the newtype guard's FromRequestParts impl differs
between versions (see the version note in the patterns below).
Quick Reference
Mechanism
Protects
Requirement lives on
Built from
Middleware guard
a group of routes
the router
from_fn / from_fn_with_state + route_layer
Newtype guard extractor
a single handler
the handler signature
a FromRequestParts impl
Status code rule:
Situation
Status
Meaning
Missing or invalid credentials
401 Unauthorized
"I do not know who you are" (authentication layer)
Known user lacks a role or permission
403 Forbidden
"I know who you are, you may not do this" (authorization layer)
.layer() versus .route_layer():
Method
Runs on
Use for
.layer()
EVERY request, including the unmatched fallback (404) path
Middleware guard argument order (from_fn / from_fn_with_state):
[zero or more FromRequestParts extractors], [exactly one FromRequest extractor], Next
State and Claims are FromRequestParts and come first. Request is the
single FromRequest extractor and is second to last. Next is always last.
Core rules:
ALWAYS apply an authorization guard with .route_layer(). NEVER .layer().
ALWAYS return 403 Forbidden on a failed role or permission check.
ALWAYS register routes BEFORE attaching .route_layer(); it only wraps
routes that already exist.
ALWAYS reuse the Claims extractor for identity. NEVER re-verify the token
inside a guard.
ALWAYS check a permission (articles:write) rather than a coarse role when
the role set may grow.
NEVER implement both FromRequest and FromRequestParts for a guard
newtype; the official docs warn this makes the extractor unusable.
Decision Trees
Middleware guard or newtype extractor
How many routes does this requirement protect?
a whole group (every route under /admin)
-> middleware guard: from_fn(_) or from_fn_with_state(_) + .route_layer()
exactly one handler
-> newtype guard extractor: a FromRequestParts type in the handler signature
one handler, and the requirement must be visible in the signature
-> newtype guard extractor (self-documenting, impossible to forget)
from_fn or from_fn_with_state
Does the authorization decision need application state?
no, it only reads fields already inside Claims (claims.role, claims.permissions)
-> from_fn(guard)
yes, it queries a permissions database, a policy cache, or a role-to-permission table
-> from_fn_with_state(state.clone(), guard), and call .with_state(state) on the router
Which status code
Why is the request being rejected?
no credentials, or the token is invalid or expired
-> 401 Unauthorized (this is the Claims extractor's job, not the guard's)
the user is known but the role or permission does not match
-> 403 Forbidden (the guard returns this)
NEVER return 401 from an authorization guard.
Patterns
Pattern: role-based middleware guard with route_layer
from_fn turns an async fn into a Layer. The guard reads the verified
Claims, checks the role, and either returns 403 or calls next.run.
use axum::{
extract::Request,
http::StatusCode,
middleware::{self, Next},
response::Response,
routing::get,
Router,
};
// `Claims` is the verified JWT extractor from axum-impl-auth-jwt.// It is FromRequestParts, so it runs first and a missing or invalid// token already rejects with 401 before this guard body runs.asyncfnrequire_admin(
claims: Claims, // FromRequestParts: runs first
request: Request, // FromRequest: the single body extractor
next: Next, // Next: always last
) ->Result<Response, StatusCode> {
if claims.role != "admin" {
// authenticated but not authorized: 403, NEVER 401returnErr(StatusCode::FORBIDDEN);
}
Ok(next.run(request).await)
}
letadmin_routes = Router::new()
.route("/admin/users", get(list_users))
.route("/admin/settings", get(settings))
// route_layer, NOT layer: a non-existent /admin/* path stays 404
.route_layer(middleware::from_fn(require_admin));
Pattern: from_fn_with_state for a state-dependent permission check
When the decision needs application state (a permission store, a policy
cache), use from_fn_with_state. Verified signature:
State surfaces inside the guard as a State<S> extractor.
use axum::{
extract::{Request, State},
http::StatusCode,
middleware::{self, Next},
response::Response,
routing::get,
Router,
};
#[derive(Clone)]structAppState {
perms: PermissionStore,
}
asyncfnrequire_users_write(
State(state): State<AppState>, // FromRequestParts: first
claims: Claims, // FromRequestParts: still before Request
request: Request, // FromRequest: second to last
next: Next, // Next: last
) ->Result<Response, StatusCode> {
letallowed = state
.perms
.has(&claims.sub, "users:write")
.await
.map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
if !allowed {
returnErr(StatusCode::FORBIDDEN);
}
Ok(next.run(request).await)
}
letstate = AppState { perms: PermissionStore::new() };
letapp = Router::new()
.route("/admin/users", get(list_users))
// the same state value is passed twice: clone for the layer
.route_layer(middleware::from_fn_with_state(state.clone(), require_users_write))
.with_state(state);
ALWAYS pass the state twice: state.clone() into from_fn_with_state and the
original state into .with_state(). The official docs example uses exactly
this route_layer plus double-pass shape.
Pattern: permission-based check is the preferred default
A role check hardcodes a fixed hierarchy into every endpoint. A permission
check names the CAPABILITY the endpoint needs, independent of which roles hold
it. The mechanism is identical; only the predicate changes.
// BRITTLE: every editor-or-above guard must repeat the role list.// Adding a "moderator" role means editing every one of these.asyncfnrequire_editor(claims: Claims, request: Request, next: Next)
->Result<Response, StatusCode>
{
if claims.role != "editor" && claims.role != "admin" {
returnErr(StatusCode::FORBIDDEN);
}
Ok(next.run(request).await)
}
// STABLE: the endpoint names the capability, not the roles that have it.// Adding a "moderator" role only changes the role-to-permission mapping.asyncfnrequire_articles_write(claims: Claims, request: Request, next: Next)
->Result<Response, StatusCode>
{
if !claims.permissions.contains("articles:write") {
returnErr(StatusCode::FORBIDDEN);
}
Ok(next.run(request).await)
}
The Claims struct SHOULD carry a permission set (HashSet<String> or
Vec<String>) using a resource:action convention (users:read,
users:write, billing:refund). The authentication step expands a role into
its permission set when minting the token, so guards only ever check
permissions.
Pattern: newtype guard extractor (AdminClaims)
For a SINGLE protected handler, a newtype FromRequestParts extractor makes
the requirement visible in the signature. It composes WITH the Claims
extractor by calling Claims::from_request_parts, never re-verifying the
token.
use axum::{
extract::FromRequestParts,
http::{request::Parts, StatusCode},
};
// A handler that takes `AdminClaims` is provably admin-only.pubstructAdminClaims(pub Claims);
// axum 0.8: native async fn in trait, no attribute needed.impl<S> FromRequestParts<S> forAdminClaimswhere
S: Send + Sync,
{
typeRejection = StatusCode;
asyncfnfrom_request_parts(parts: &mut Parts, state: &S)
->Result<Self, Self::Rejection>
{
// Reuse the existing Claims extractor for identity.letclaims = Claims::from_request_parts(parts, state)
.await
.map_err(|_| StatusCode::UNAUTHORIZED)?; // bad/no token: 401if claims.role != "admin" {
returnErr(StatusCode::FORBIDDEN); // known, not admin: 403
}
Ok(AdminClaims(claims))
}
}
// axum 0.7: the SAME impl block must be annotated with #[async_trait].#[async_trait::async_trait]impl<S> FromRequestParts<S> forAdminClaimswhere
S: Send + Sync,
{
typeRejection = StatusCode;
asyncfnfrom_request_parts(parts: &mut Parts, state: &S)
->Result<Self, Self::Rejection>
{ /* identical body as the axum 0.8 version above */ }
}
Used in a handler, the requirement is self-documenting:
use axum::Json;
// The argument type PROVES this handler is admin-only.asyncfndelete_user(AdminClaims(claims): AdminClaims)
->Result<Json<()>, StatusCode>
{
tracing::info!(admin = %claims.sub, "admin deleting user");
Ok(Json(()))
}
NEVER implement both FromRequest and FromRequestParts for the newtype; the
official docs warn this makes the extractor unusable. A guard inspects request
parts (headers, claims) only, so FromRequestParts alone is correct.
Reference Links
references/methods.md: verified signatures for from_fn,
from_fn_with_state, Next, route_layer, layer, with_state, and
FromRequestParts, plus the middleware argument-order rule.
references/examples.md: full working programs, a permission store wired
through from_fn_with_state, a generic RequirePermission extractor, and
the 0.7 versus 0.8 newtype-guard forms.
references/anti-patterns.md: the seven recurring authorization mistakes
with the root cause of each and the fix.
Related skills:
axum-impl-auth-jwt: defines the Claims extractor that every guard here
reuses for identity.
axum-impl-middleware: from_fn argument-order rules and layer ordering.
axum-syntax-custom-extractors: the FromRequestParts trait the newtype
guard implements.
