Merge branch 'rp-initiated-logout'

Implements a extractor to get the
[RP-Initiated Logout](https://openid.net/specs/openid-connect-rpinitiated-1_0.html) URL.

.gitignore

@@ -1,2 +1,3 @@
 target
 Cargo.lock
+.env

Cargo.toml

@@ -24,3 +24,4 @@ openidconnect = "3.5"
 serde = "1.0"
 futures-util = "0.3"
 reqwest = { version = "0.11", default-features = false }
+urlencoding = "2.1.3"

README.md

@@ -13,6 +13,8 @@ The extractors will always return a value.
 The `OidcClaims`-extractor can be used to get the OpenId Conenct Claims.
 The `OidcAccessToken`-extractor can be used to get the OpenId Connect Access Token.
 
+The `OidcRpInitializedLogout`-extractor can be used to get the rp initialized logout uri.
+
 Your OIDC-Client must be allowed to redirect to **every** subpath of your application base url.
 
 # Examples

examples/basic/Cargo.toml

@@ -11,3 +11,5 @@ axum = "0.7.4"
 axum-oidc = { path = "./../.." }
 tower = "0.4.13"
 tower-sessions = "0.11.0"
+
+dotenvy = "0.15.7"

examples/basic/src/main.rs

@@ -1,8 +1,13 @@
 use axum::{
-    error_handling::HandleErrorLayer, http::Uri, response::IntoResponse, routing::get, Router,
+    error_handling::HandleErrorLayer,
+    http::Uri,
+    response::{IntoResponse, Redirect},
+    routing::get,
+    Router,
 };
 use axum_oidc::{
     error::MiddlewareError, EmptyAdditionalClaims, OidcAuthLayer, OidcClaims, OidcLoginLayer,
+    OidcRpInitiatedLogout,
 };
 use tokio::net::TcpListener;
 use tower::ServiceBuilder;
@@ -13,6 +18,12 @@ use tower_sessions::{
 
 #[tokio::main]
 async fn main() {
+    dotenvy::dotenv().ok();
+    let app_url = std::env::var("APP_URL").expect("APP_URL env variable");
+    let issuer = std::env::var("ISSUER").expect("ISSUER env variable");
+    let client_id = std::env::var("CLIENT_ID").expect("CLIENT_ID env variable");
+    let client_secret = std::env::var("CLIENT_SECRET").ok();
+
     let session_store = MemoryStore::default();
     let session_layer = SessionManagerLayer::new(session_store)
         .with_secure(false)
@@ -31,10 +42,10 @@ async fn main() {
         }))
         .layer(
             OidcAuthLayer::<EmptyAdditionalClaims>::discover_client(
-                Uri::from_static("https://app.example.com"),
-                "https://auth.example.com/auth/realms/example".to_string(),
-                "my-client".to_string(),
-                Some("123456".to_owned()),
+                Uri::from_maybe_shared(app_url).expect("valid APP_URL"),
+                issuer,
+                client_id,
+                client_secret,
                 vec![],
             )
             .await
@@ -43,6 +54,7 @@ async fn main() {
 
     let app = Router::new()
         .route("/foo", get(authenticated))
+        .route("/logout", get(logout))
         .layer(oidc_login_service)
         .route("/bar", get(maybe_authenticated))
         .layer(oidc_auth_service)
@@ -70,3 +82,11 @@ async fn maybe_authenticated(
         "Hello anon!".to_string()
     }
 }
+
+async fn logout(logout: OidcRpInitiatedLogout) -> impl IntoResponse {
+    let logout_uri = logout
+        .with_post_logout_redirect(Uri::from_static("https://pfzetto.de"))
+        .uri()
+        .unwrap();
+    Redirect::temporary(&logout_uri.to_string())
+}

src/error.rs

@@ -10,6 +10,9 @@ use thiserror::Error;
 pub enum ExtractorError {
     #[error("unauthorized")]
     Unauthorized,
+
+    #[error("rp initiated logout information not found")]
+    RpInitiatedLogoutInformationNotFound,
 }
 
 #[derive(Debug, Error)]
@@ -65,6 +68,9 @@ pub enum Error {
     #[error("url parsing: {0:?}")]
     UrlParsing(#[from] openidconnect::url::ParseError),
 
+    #[error("invalid end_session_endpoint uri: {0:?}")]
+    InvalidEndSessionEndpoint(http::uri::InvalidUri),
+
     #[error("discovery: {0:?}")]
     Discovery(#[from] openidconnect::DiscoveryError<openidconnect::reqwest::Error<reqwest::Error>>),
 
@@ -77,7 +83,12 @@ pub enum Error {
 
 impl IntoResponse for ExtractorError {
     fn into_response(self) -> axum_core::response::Response {
-        (StatusCode::UNAUTHORIZED, "unauthorized").into_response()
+        match self {
+            Self::Unauthorized => (StatusCode::UNAUTHORIZED, "unauthorized").into_response(),
+            Self::RpInitiatedLogoutInformationNotFound => {
+                (StatusCode::INTERNAL_SERVER_ERROR, "intenal server error").into_response()
+            }
+        }
     }
 }
 

src/extractor.rs

@@ -1,9 +1,9 @@
-use std::ops::Deref;
+use std::{borrow::Cow, ops::Deref};
 
 use crate::{error::ExtractorError, AdditionalClaims};
 use async_trait::async_trait;
 use axum_core::extract::FromRequestParts;
-use http::request::Parts;
+use http::{request::Parts, uri::PathAndQuery, Uri};
 use openidconnect::{core::CoreGenderClaim, IdTokenClaims};
 
 /// Extractor for the OpenID Connect Claims.
@@ -78,6 +78,84 @@ impl Deref for OidcAccessToken {
 
 impl AsRef<str> for OidcAccessToken {
     fn as_ref(&self) -> &str {
-        self.0.as_str()
+        &self.0
+    }
+}
+
+/// Extractor for the [OpenID Connect RP-Initialized Logout](https://openid.net/specs/openid-connect-rpinitiated-1_0.html) URL
+///
+/// This Extractor will only succed when the cached session is valid, [crate::middleware::OidcAuthMiddleware] is loaded and the issuer supports RP-Initialized Logout.
+#[derive(Clone)]
+pub struct OidcRpInitiatedLogout {
+    pub(crate) end_session_endpoint: Uri,
+    pub(crate) id_token_hint: String,
+    pub(crate) client_id: String,
+    pub(crate) post_logout_redirect_uri: Option<Uri>,
+    pub(crate) state: Option<String>,
+}
+
+impl OidcRpInitiatedLogout {
+    /// set uri that the user is redirected to after logout.
+    /// This uri must be in the allowed by issuer.
+    pub fn with_post_logout_redirect(mut self, uri: Uri) -> Self {
+        self.post_logout_redirect_uri = Some(uri);
+        self
+    }
+    /// set the state parameter that is appended as a query to the post logout redirect uri.
+    pub fn with_state(mut self, state: String) -> Self {
+        self.state = Some(state);
+        self
+    }
+    /// get the uri that the client needs to access for logout
+    pub fn uri(&self) -> Result<Uri, http::Error> {
+        let mut parts = self.end_session_endpoint.clone().into_parts();
+
+        let query = {
+            let mut query: Vec<(&str, Cow<'_, str>)> = Vec::with_capacity(4);
+            query.push(("id_token_hint", Cow::Borrowed(&self.id_token_hint)));
+            query.push(("client_id", Cow::Borrowed(&self.client_id)));
+
+            if let Some(post_logout_redirect_uri) = &self.post_logout_redirect_uri {
+                query.push((
+                    "post_logout_redirect_uri",
+                    Cow::Owned(post_logout_redirect_uri.to_string()),
+                ));
+            }
+            if let Some(state) = &self.state {
+                query.push(("state", Cow::Borrowed(state)));
+            }
+
+            query
+                .into_iter()
+                .map(|(k, v)| format!("{}={}", k, urlencoding::encode(&v)))
+                .collect::<Vec<_>>()
+                .join("&")
+        };
+
+        let path_and_query = match parts.path_and_query {
+            Some(path_and_query) => {
+                PathAndQuery::from_maybe_shared(format!("{}?{}", path_and_query.path(), query))
+            }
+            None => PathAndQuery::from_maybe_shared(format!("?{}", query)),
+        };
+        parts.path_and_query = Some(path_and_query?);
+
+        Ok(Uri::from_parts(parts)?)
+    }
+}
+
+#[async_trait]
+impl<S> FromRequestParts<S> for OidcRpInitiatedLogout
+where
+    S: Send + Sync,
+{
+    type Rejection = ExtractorError;
+
+    async fn from_request_parts(parts: &mut Parts, _: &S) -> Result<Self, Self::Rejection> {
+        parts
+            .extensions
+            .get::<Self>()
+            .cloned()
+            .ok_or(ExtractorError::Unauthorized)
     }
 }

src/lib.rs

@@ -1,32 +1,38 @@
+#![deny(unsafe_code)]
+#![deny(clippy::unwrap_used)]
+#![deny(warnings)]
 #![doc = include_str!("../README.md")]
 
-use std::str::FromStr;
-
 use crate::error::Error;
 use http::Uri;
 use openidconnect::{
     core::{
-        CoreAuthDisplay, CoreAuthPrompt, CoreErrorResponseType, CoreGenderClaim, CoreJsonWebKey,
-        CoreJsonWebKeyType, CoreJsonWebKeyUse, CoreJweContentEncryptionAlgorithm,
-        CoreJwsSigningAlgorithm, CoreProviderMetadata, CoreRevocableToken,
-        CoreRevocationErrorResponse, CoreTokenIntrospectionResponse, CoreTokenType,
+        CoreAuthDisplay, CoreAuthPrompt, CoreClaimName, CoreClaimType, CoreClientAuthMethod,
+        CoreErrorResponseType, CoreGenderClaim, CoreGrantType, CoreJsonWebKey, CoreJsonWebKeyType,
+        CoreJsonWebKeyUse, CoreJweContentEncryptionAlgorithm, CoreJweKeyManagementAlgorithm,
+        CoreJwsSigningAlgorithm, CoreResponseMode, CoreResponseType, CoreRevocableToken,
+        CoreRevocationErrorResponse, CoreSubjectIdentifierType, CoreTokenIntrospectionResponse,
+        CoreTokenType,
     },
     reqwest::async_http_client,
-    ClientId, ClientSecret, CsrfToken, EmptyExtraTokenFields, IdTokenFields, IssuerUrl, Nonce,
-    PkceCodeVerifier, RefreshToken, StandardErrorResponse, StandardTokenResponse,
+    AccessToken, ClientId, ClientSecret, CsrfToken, EmptyExtraTokenFields, IdTokenFields,
+    IssuerUrl, Nonce, PkceCodeVerifier, RefreshToken, StandardErrorResponse, StandardTokenResponse,
 };
-use serde::{Deserialize, Serialize};
+use serde::{de::DeserializeOwned, Deserialize, Serialize};
 
 pub mod error;
 mod extractor;
 mod middleware;
 
-pub use extractor::{OidcAccessToken, OidcClaims};
+pub use extractor::{OidcAccessToken, OidcClaims, OidcRpInitiatedLogout};
 pub use middleware::{OidcAuthLayer, OidcAuthMiddleware, OidcLoginLayer, OidcLoginMiddleware};
 
 const SESSION_KEY: &str = "axum-oidc";
 
-pub trait AdditionalClaims: openidconnect::AdditionalClaims + Clone + Sync + Send {}
+pub trait AdditionalClaims:
+    openidconnect::AdditionalClaims + Clone + Sync + Send + Serialize + DeserializeOwned
+{
+}
 
 type OidcTokenResponse<AC> = StandardTokenResponse<
     IdTokenFields<
@@ -66,14 +72,34 @@ type Client<AC> = openidconnect::Client<
     CoreRevocationErrorResponse,
 >;
 
+type ProviderMetadata = openidconnect::ProviderMetadata<
+    AdditionalProviderMetadata,
+    CoreAuthDisplay,
+    CoreClientAuthMethod,
+    CoreClaimName,
+    CoreClaimType,
+    CoreGrantType,
+    CoreJweContentEncryptionAlgorithm,
+    CoreJweKeyManagementAlgorithm,
+    CoreJwsSigningAlgorithm,
+    CoreJsonWebKeyType,
+    CoreJsonWebKeyUse,
+    CoreJsonWebKey,
+    CoreResponseMode,
+    CoreResponseType,
+    CoreSubjectIdentifierType,
+>;
+
 pub type BoxError = Box<dyn std::error::Error + Send + Sync>;
 
 /// OpenID Connect Client
 #[derive(Clone)]
 pub struct OidcClient<AC: AdditionalClaims> {
     scopes: Vec<String>,
+    client_id: String,
     client: Client<AC>,
     application_base_url: Uri,
+    end_session_endpoint: Option<Uri>,
 }
 
 impl<AC: AdditionalClaims> OidcClient<AC> {
@@ -85,17 +111,25 @@ impl<AC: AdditionalClaims> OidcClient<AC> {
         scopes: Vec<String>,
     ) -> Result<Self, Error> {
         let provider_metadata =
-            CoreProviderMetadata::discover_async(IssuerUrl::new(issuer)?, async_http_client)
-                .await?;
+            ProviderMetadata::discover_async(IssuerUrl::new(issuer)?, async_http_client).await?;
+        let end_session_endpoint = provider_metadata
+            .additional_metadata()
+            .end_session_endpoint
+            .clone()
+            .map(Uri::from_maybe_shared)
+            .transpose()
+            .map_err(Error::InvalidEndSessionEndpoint)?;
         let client = Client::from_provider_metadata(
             provider_metadata,
-            ClientId::new(client_id),
+            ClientId::new(client_id.clone()),
             client_secret.map(ClientSecret::new),
         );
         Ok(Self {
             scopes,
             client,
+            client_id,
             application_base_url,
+            end_session_endpoint,
         })
     }
 }
@@ -117,24 +151,26 @@ struct OidcQuery {
 
 /// oidc session
 #[derive(Serialize, Deserialize, Debug)]
-struct OidcSession {
+#[serde(bound = "AC: Serialize + DeserializeOwned")]
+struct OidcSession<AC: AdditionalClaims> {
     nonce: Nonce,
     csrf_token: CsrfToken,
     pkce_verifier: PkceCodeVerifier,
-    id_token: Option<String>,
-    access_token: Option<String>,
-    refresh_token: Option<String>,
+    authenticated: Option<AuthenticatedSession<AC>>,
 }
 
-impl OidcSession {
-    pub(crate) fn id_token<AC: AdditionalClaims>(&self) -> Option<IdToken<AC>> {
-        self.id_token
-            .as_ref()
-            .map(|x| IdToken::<AC>::from_str(x).unwrap())
-    }
-    pub(crate) fn refresh_token(&self) -> Option<RefreshToken> {
-        self.refresh_token
-            .as_ref()
-            .map(|x| RefreshToken::new(x.to_string()))
-    }
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(bound = "AC: Serialize + DeserializeOwned")]
+struct AuthenticatedSession<AC: AdditionalClaims> {
+    id_token: IdToken<AC>,
+    access_token: AccessToken,
+    refresh_token: Option<RefreshToken>,
 }
+
+/// additional metadata that is discovered on client creation via the
+/// `.well-knwon/openid-configuration` endpoint.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+struct AdditionalProviderMetadata {
+    end_session_endpoint: Option<String>,
+}
+impl openidconnect::AdditionalProviderMetadata for AdditionalProviderMetadata {}

src/middleware.rs

@@ -9,24 +9,25 @@ use axum::{
 };
 use axum_core::{extract::FromRequestParts, response::Response};
 use futures_util::future::BoxFuture;
-use http::{uri::PathAndQuery, Request, Uri};
+use http::{request::Parts, uri::PathAndQuery, Request, Uri};
 use tower_layer::Layer;
 use tower_service::Service;
 use tower_sessions::Session;
 
 use openidconnect::{
-    core::{CoreAuthenticationFlow, CoreErrorResponseType},
+    core::{CoreAuthenticationFlow, CoreErrorResponseType, CoreGenderClaim},
     reqwest::async_http_client,
-    AccessTokenHash, AuthorizationCode, CsrfToken, Nonce, OAuth2TokenResponse, PkceCodeChallenge,
-    PkceCodeVerifier, RedirectUrl,
+    AccessToken, AccessTokenHash, AuthorizationCode, CsrfToken, IdTokenClaims, Nonce,
+    OAuth2TokenResponse, PkceCodeChallenge, PkceCodeVerifier, RedirectUrl, RefreshToken,
     RequestTokenError::ServerResponse,
     Scope, TokenResponse,
 };
 
 use crate::{
     error::{Error, MiddlewareError},
-    extractor::{OidcAccessToken, OidcClaims},
-    AdditionalClaims, BoxError, OidcClient, OidcQuery, OidcSession, SESSION_KEY,
+    extractor::{OidcAccessToken, OidcClaims, OidcRpInitiatedLogout},
+    AdditionalClaims, AuthenticatedSession, BoxError, IdToken, OidcClient, OidcQuery, OidcSession,
+    SESSION_KEY,
 };
 
 /// Layer for the [OidcLoginMiddleware].
@@ -121,7 +122,7 @@ where
                     .extensions
                     .get::<Session>()
                     .ok_or(MiddlewareError::SessionNotFound)?;
-                let login_session: Option<OidcSession> = session
+                let login_session: Option<OidcSession<AC>> = session
                     .get(SESSION_KEY)
                     .await
                     .map_err(MiddlewareError::from)?;
@@ -158,26 +159,15 @@ where
                     let claims = id_token
                         .claims(&oidcclient.client.id_token_verifier(), &login_session.nonce)?;
 
-                    // Verify the access token hash to ensure that the access token hasn't been substituted for
-                    // another user's.
-                    if let Some(expected_access_token_hash) = claims.access_token_hash() {
-                        let actual_access_token_hash = AccessTokenHash::from_token(
-                            token_response.access_token(),
-                            &id_token.signing_alg()?,
-                        )?;
-                        if actual_access_token_hash != *expected_access_token_hash {
-                            return Err(MiddlewareError::AccessTokenHashInvalid);
-                        }
-                    }
+                    validate_access_token_hash(id_token, token_response.access_token(), claims)?;
 
-                    login_session.id_token = Some(id_token.to_string());
-                    login_session.access_token =
-                        Some(token_response.access_token().secret().to_string());
-                    login_session.refresh_token = token_response
-                        .refresh_token()
-                        .map(|x| x.secret().to_string());
+                    login_session.authenticated = Some(AuthenticatedSession {
+                        id_token: id_token.clone(),
+                        access_token: token_response.access_token().clone(),
+                        refresh_token: token_response.refresh_token().cloned(),
+                    });
 
-                    session.insert(SESSION_KEY, login_session).await.unwrap();
+                    session.insert(SESSION_KEY, login_session).await?;
 
                     Ok(Redirect::temporary(&handler_uri.to_string()).into_response())
                 } else {
@@ -198,16 +188,14 @@ where
                         auth.set_pkce_challenge(pkce_challenge).url()
                     };
 
-                    let oidc_session = OidcSession {
+                    let oidc_session = OidcSession::<AC> {
                         nonce,
                         csrf_token,
                         pkce_verifier,
-                        id_token: None,
-                        access_token: None,
-                        refresh_token: None,
+                        authenticated: None,
                     };
 
-                    session.insert(SESSION_KEY, oidc_session).await.unwrap();
+                    session.insert(SESSION_KEY, oidc_session).await?;
 
                     Ok(Redirect::temporary(auth_url.as_str()).into_response())
                 }
@@ -307,7 +295,7 @@ where
                 .extensions
                 .get::<Session>()
                 .ok_or(MiddlewareError::SessionNotFound)?;
-            let mut login_session: Option<OidcSession> = session
+            let mut login_session: Option<OidcSession<AC>> = session
                 .get(SESSION_KEY)
                 .await
                 .map_err(MiddlewareError::from)?;
@@ -320,88 +308,37 @@ where
                 .set_redirect_uri(RedirectUrl::new(handler_uri.to_string())?);
 
             if let Some(login_session) = &mut login_session {
-                let id_token_claims = login_session.id_token::<AC>().and_then(|id_token| {
-                    id_token
+                let id_token_claims = login_session.authenticated.as_ref().and_then(|session| {
+                    session
+                        .id_token
                         .claims(&oidcclient.client.id_token_verifier(), &login_session.nonce)
                         .ok()
                         .cloned()
+                        .map(|claims| (session, claims))
                 });
 
-                match (id_token_claims, login_session.refresh_token()) {
+                if let Some((session, claims)) = id_token_claims {
                     // stored id token is valid and can be used
-                    (Some(claims), _) => {
-                        parts.extensions.insert(OidcClaims(claims));
-                        parts.extensions.insert(OidcAccessToken(
-                            login_session.access_token.clone().unwrap_or_default(),
-                        ));
-                    }
-                    // stored id token is invalid and can't be uses, but we have a refresh token
-                    // and can use it and try to get another id token.
-                    (_, Some(refresh_token)) => {
-                        let mut refresh_request =
-                            oidcclient.client.exchange_refresh_token(&refresh_token);
+                    insert_extensions(&mut parts, claims.clone(), &oidcclient, session);
+                } else if let Some(refresh_token) = login_session
+                    .authenticated
+                    .as_ref()
+                    .and_then(|x| x.refresh_token.as_ref())
+                {
+                    if let Some((claims, authenticated_session)) =
+                        try_refresh_token(&oidcclient, refresh_token, &login_session.nonce).await?
+                    {
+                        insert_extensions(&mut parts, claims, &oidcclient, &authenticated_session);
+                        login_session.authenticated = Some(authenticated_session);
+                    };
 
-                        for scope in oidcclient.scopes.iter() {
-                            refresh_request =
-                                refresh_request.add_scope(Scope::new(scope.to_string()));
-                        }
+                    // save refreshed session or delete it when the token couldn't be refreshed
+                    let session = parts
+                        .extensions
+                        .get::<Session>()
+                        .ok_or(MiddlewareError::SessionNotFound)?;
 
-                        match refresh_request.request_async(async_http_client).await {
-                            Ok(token_response) => {
-                                // Extract the ID token claims after verifying its authenticity and nonce.
-                                let id_token = token_response
-                                    .id_token()
-                                    .ok_or(MiddlewareError::IdTokenMissing)?;
-                                let claims = id_token.claims(
-                                    &oidcclient.client.id_token_verifier(),
-                                    &login_session.nonce,
-                                )?;
-
-                                // Verify the access token hash to ensure that the access token hasn't been substituted for
-                                // another user's.
-                                if let Some(expected_access_token_hash) = claims.access_token_hash()
-                                {
-                                    let actual_access_token_hash = AccessTokenHash::from_token(
-                                        token_response.access_token(),
-                                        &id_token.signing_alg()?,
-                                    )?;
-                                    if actual_access_token_hash != *expected_access_token_hash {
-                                        return Err(MiddlewareError::AccessTokenHashInvalid);
-                                    }
-                                }
-
-                                login_session.id_token = Some(id_token.to_string());
-                                login_session.access_token =
-                                    Some(token_response.access_token().secret().to_string());
-                                login_session.refresh_token = token_response
-                                    .refresh_token()
-                                    .map(|x| x.secret().to_string());
-
-                                parts.extensions.insert(OidcClaims(claims.clone()));
-                                parts.extensions.insert(OidcAccessToken(
-                                    login_session.access_token.clone().unwrap_or_default(),
-                                ));
-                            }
-                            Err(ServerResponse(e))
-                                if *e.error() == CoreErrorResponseType::InvalidGrant =>
-                            {
-                                // Refresh failed, refresh_token most likely expired or
-                                // invalid, the session can be considered lost
-                                login_session.refresh_token = None;
-                            }
-                            Err(err) => {
-                                return Err(err.into());
-                            }
-                        };
-
-                        let session = parts
-                            .extensions
-                            .get::<Session>()
-                            .ok_or(MiddlewareError::SessionNotFound)?;
-
-                        session.insert(SESSION_KEY, login_session).await.unwrap();
-                    }
-                    (None, None) => {}
+                    session.insert(SESSION_KEY, login_session).await?;
                 }
             }
 
@@ -448,3 +385,85 @@ pub fn strip_oidc_from_path(base_url: Uri, uri: &Uri) -> Result<Uri, MiddlewareE
 
     Ok(Uri::from_parts(base_url)?)
 }
+
+/// insert all extensions that are used by the extractors
+fn insert_extensions<AC: AdditionalClaims>(
+    parts: &mut Parts,
+    claims: IdTokenClaims<AC, CoreGenderClaim>,
+    client: &OidcClient<AC>,
+    authenticated_session: &AuthenticatedSession<AC>,
+) {
+    parts.extensions.insert(OidcClaims(claims));
+    parts.extensions.insert(OidcAccessToken(
+        authenticated_session.access_token.secret().to_string(),
+    ));
+    if let Some(end_session_endpoint) = &client.end_session_endpoint {
+        parts.extensions.insert(OidcRpInitiatedLogout {
+            end_session_endpoint: end_session_endpoint.clone(),
+            id_token_hint: authenticated_session.id_token.to_string(),
+            client_id: client.client_id.clone(),
+            post_logout_redirect_uri: None,
+            state: None,
+        });
+    }
+}
+
+/// Verify the access token hash to ensure that the access token hasn't been substituted for
+/// another user's.
+/// Returns `Ok` when access token is valid
+fn validate_access_token_hash<AC: AdditionalClaims>(
+    id_token: &IdToken<AC>,
+    access_token: &AccessToken,
+    claims: &IdTokenClaims<AC, CoreGenderClaim>,
+) -> Result<(), MiddlewareError> {
+    if let Some(expected_access_token_hash) = claims.access_token_hash() {
+        let actual_access_token_hash =
+            AccessTokenHash::from_token(access_token, &id_token.signing_alg()?)?;
+        if actual_access_token_hash == *expected_access_token_hash {
+            Ok(())
+        } else {
+            Err(MiddlewareError::AccessTokenHashInvalid)
+        }
+    } else {
+        Ok(())
+    }
+}
+
+async fn try_refresh_token<AC: AdditionalClaims>(
+    client: &OidcClient<AC>,
+    refresh_token: &RefreshToken,
+    nonce: &Nonce,
+) -> Result<Option<(IdTokenClaims<AC, CoreGenderClaim>, AuthenticatedSession<AC>)>, MiddlewareError>
+{
+    let mut refresh_request = client.client.exchange_refresh_token(refresh_token);
+
+    for scope in client.scopes.iter() {
+        refresh_request = refresh_request.add_scope(Scope::new(scope.to_string()));
+    }
+
+    match refresh_request.request_async(async_http_client).await {
+        Ok(token_response) => {
+            // Extract the ID token claims after verifying its authenticity and nonce.
+            let id_token = token_response
+                .id_token()
+                .ok_or(MiddlewareError::IdTokenMissing)?;
+            let claims = id_token.claims(&client.client.id_token_verifier(), nonce)?;
+
+            validate_access_token_hash(id_token, token_response.access_token(), claims)?;
+
+            let authenticated_session = AuthenticatedSession {
+                id_token: id_token.clone(),
+                access_token: token_response.access_token().clone(),
+                refresh_token: token_response.refresh_token().cloned(),
+            };
+
+            Ok(Some((claims.clone(), authenticated_session)))
+        }
+        Err(ServerResponse(e)) if *e.error() == CoreErrorResponseType::InvalidGrant => {
+            // Refresh failed, refresh_token most likely expired or
+            // invalid, the session can be considered lost
+            Ok(None)
+        }
+        Err(err) => Err(err.into()),
+    }
+}