commit 75ed3b861a85cd18d8473a65cc6a90bc38528527
Author: Paul Z <info@pfz4.de>
Date:   Fri Apr 21 15:11:37 2023 +0200

    init

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..4fffb2f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/target
+/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..8a5cbb9
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,17 @@
+[package]
+name = "axum_oidc"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+axum = "0.6"
+axum-extra = {version="0.7", features=["cookie", "cookie-private"]}
+cookie = "0.17"
+openidconnect = "3.0"
+async-trait = "0.1"
+serde = "1.0"
+thiserror = "1.0"
+reqwest = { version="0.11", default_features=false}
+serde_json = "1.0"
diff --git a/src/error.rs b/src/error.rs
new file mode 100644
index 0000000..9cc2e37
--- /dev/null
+++ b/src/error.rs
@@ -0,0 +1,54 @@
+use axum::response::{IntoResponse, Redirect};
+use axum_extra::extract::PrivateCookieJar;
+use openidconnect::{
+    core::CoreErrorResponseType, url::ParseError, ClaimsVerificationError, DiscoveryError,
+    SigningError, StandardErrorResponse,
+};
+use reqwest::StatusCode;
+
+type RequestTokenError = openidconnect::RequestTokenError<
+    openidconnect::reqwest::Error<reqwest::Error>,
+    StandardErrorResponse<CoreErrorResponseType>,
+>;
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("discovery error: {:?}", 0)]
+    Discovery(#[from] DiscoveryError<openidconnect::reqwest::Error<reqwest::Error>>),
+    #[error("parse error: {:?}", 0)]
+    Parse(#[from] ParseError),
+    #[error("request token error: {:?}", 0)]
+    RequestToken(#[from] RequestTokenError),
+    #[error("claims verification error: {:?}", 0)]
+    ClaimsVerification(#[from] ClaimsVerificationError),
+    #[error("signing error: {:?}", 0)]
+    Signing(#[from] SigningError),
+
+    #[error("json serialization error: {:?}", 0)]
+    Json(#[from] serde_json::Error),
+
+    #[error("csrf token is invalid")]
+    CsrfTokenInvalid,
+
+    #[error("id token not found")]
+    IdTokenNotFound,
+
+    #[error("access token hash is invalid")]
+    AccessTokenHashInvalid,
+
+    #[error("just a redirect")]
+    Redirect((PrivateCookieJar, Redirect)),
+}
+
+impl IntoResponse for Error {
+    fn into_response(self) -> axum::response::Response {
+        match self {
+            Self::CsrfTokenInvalid => {
+                { (StatusCode::BAD_REQUEST, "csrf token is invalid").into_response() }
+                    .into_response()
+            }
+            Self::Redirect(redirect) => redirect.into_response(),
+            _ => (StatusCode::INTERNAL_SERVER_ERROR, "internal server error").into_response(),
+        }
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..25092be
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,221 @@
+use async_trait::async_trait;
+use axum::{
+    extract::{FromRef, FromRequestParts, Query},
+    http::request::Parts,
+    response::Redirect,
+};
+use axum_extra::extract::{
+    cookie::{Cookie, SameSite},
+    PrivateCookieJar,
+};
+use cookie::time::{Duration, OffsetDateTime};
+use error::Error;
+use openidconnect::{
+    core::{
+        CoreAuthDisplay, CoreAuthPrompt, CoreAuthenticationFlow, CoreErrorResponseType,
+        CoreGenderClaim, CoreJsonWebKey, CoreJsonWebKeyType, CoreJsonWebKeyUse,
+        CoreJweContentEncryptionAlgorithm, CoreJwsSigningAlgorithm, CoreProviderMetadata,
+        CoreRevocableToken, CoreRevocationErrorResponse, CoreTokenIntrospectionResponse,
+        CoreTokenType,
+    },
+    reqwest::async_http_client,
+    AccessTokenHash, AuthorizationCode, Client, ClientId, ClientSecret, CsrfToken,
+    EmptyExtraTokenFields, IdTokenClaims, IdTokenFields, IssuerUrl, Nonce, OAuth2TokenResponse,
+    PkceCodeChallenge, PkceCodeVerifier, RedirectUrl, Scope, StandardErrorResponse,
+    StandardTokenResponse, TokenResponse,
+};
+use serde::{Deserialize, Serialize};
+
+pub use cookie::Key;
+
+pub mod error;
+
+const LOGIN_COOKIE_NAME: &str = "OIDC_LOGIN";
+
+pub trait AdditionalClaims: openidconnect::AdditionalClaims + Clone + Sync + Send {}
+
+type OidcTokenResponse<AC> = StandardTokenResponse<
+    IdTokenFields<
+        AC,
+        EmptyExtraTokenFields,
+        CoreGenderClaim,
+        CoreJweContentEncryptionAlgorithm,
+        CoreJwsSigningAlgorithm,
+        CoreJsonWebKeyType,
+    >,
+    CoreTokenType,
+>;
+
+pub type OidcClient<AC> = Client<
+    AC,
+    CoreAuthDisplay,
+    CoreGenderClaim,
+    CoreJweContentEncryptionAlgorithm,
+    CoreJwsSigningAlgorithm,
+    CoreJsonWebKeyType,
+    CoreJsonWebKeyUse,
+    CoreJsonWebKey,
+    CoreAuthPrompt,
+    StandardErrorResponse<CoreErrorResponseType>,
+    OidcTokenResponse<AC>,
+    CoreTokenType,
+    CoreTokenIntrospectionResponse,
+    CoreRevocableToken,
+    CoreRevocationErrorResponse,
+>;
+
+pub struct OidcApplication {
+    application_base: String,
+    issuer: IssuerUrl,
+    client_id: ClientId,
+    client_secret: Option<ClientSecret>,
+    scopes: Vec<String>,
+    cookie_key: Key,
+}
+impl OidcApplication {
+    pub fn new(
+        application_base: String,
+        issuer: String,
+        client_id: String,
+        client_secret: Option<String>,
+        scopes: Vec<String>,
+        cookie_key: Key,
+    ) -> Self {
+        Self {
+            application_base,
+            issuer: IssuerUrl::new(issuer).unwrap(),
+            client_id: ClientId::new(client_id),
+            client_secret: client_secret.map(ClientSecret::new),
+            scopes,
+            cookie_key,
+        }
+    }
+    async fn create_client<AC: AdditionalClaims>(
+        &self,
+        redirect: String,
+    ) -> Result<OidcClient<AC>, Error> {
+        let provider_metadata =
+            CoreProviderMetadata::discover_async(self.issuer.clone(), async_http_client).await?;
+        let client = OidcClient::<AC>::from_provider_metadata(
+            provider_metadata,
+            self.client_id.clone(),
+            self.client_secret.clone(),
+        )
+        .set_redirect_uri(RedirectUrl::new(redirect)?);
+        Ok(client)
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct EmptyAdditionalClaims {}
+impl openidconnect::AdditionalClaims for EmptyAdditionalClaims {}
+impl AdditionalClaims for EmptyAdditionalClaims {}
+
+pub struct ClaimsExtractor<AC: AdditionalClaims>(pub IdTokenClaims<AC, CoreGenderClaim>);
+
+#[async_trait]
+impl<S, AC> FromRequestParts<S> for ClaimsExtractor<AC>
+where
+    S: Send + Sync,
+    AC: AdditionalClaims,
+    OidcApplication: FromRef<S>,
+{
+    type Rejection = Error;
+
+    async fn from_request_parts(parts: &mut Parts, state: &S) -> Result<Self, Self::Rejection> {
+        let application: OidcApplication = OidcApplication::from_ref(state);
+        let client = application
+            .create_client(format!(
+                "{}/{}",
+                application.application_base,
+                parts.uri.path()
+            ))
+            .await?;
+        let mut jar = PrivateCookieJar::from_headers(&parts.headers, application.cookie_key);
+
+        let login_session = jar.get(LOGIN_COOKIE_NAME);
+        let query = Query::<OidcQuery>::from_request_parts(parts, state)
+            .await
+            .ok();
+
+        if let (Some(login_session), Some(Query(query))) = (login_session, query) {
+            let login_session: LoginSession = serde_json::from_str(login_session.value())?;
+
+            if login_session.csrf_token.secret() != &query.state {
+                return Err(Error::CsrfTokenInvalid);
+            }
+
+            let token_response = client
+                .exchange_code(AuthorizationCode::new(query.code.to_string()))
+                // Set the PKCE code verifier.
+                .set_pkce_verifier(login_session.pkce_verifier)
+                .request_async(async_http_client)
+                .await?;
+
+            // Extract the ID token claims after verifying its authenticity and nonce.
+            let id_token = token_response.id_token().ok_or(Error::IdTokenNotFound)?;
+            let claims = id_token.claims(&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(Error::AccessTokenHashInvalid);
+                }
+            }
+
+            Ok(Self(claims.clone()))
+        } else {
+            let (pkce_challenge, pkce_verifier) = PkceCodeChallenge::new_random_sha256();
+            let (auth_url, csrf_token, nonce) = {
+                let mut auth = client.authorize_url(
+                    CoreAuthenticationFlow::AuthorizationCode,
+                    CsrfToken::new_random,
+                    Nonce::new_random,
+                );
+
+                for scope in application.scopes.iter() {
+                    auth = auth.add_scope(Scope::new(scope.to_string()));
+                }
+                auth.set_pkce_challenge(pkce_challenge).url()
+            };
+
+            let login_session = LoginSession {
+                nonce,
+                csrf_token,
+                pkce_verifier,
+            };
+            let login_session = serde_json::to_string(&login_session)?;
+            let mut cookie = Cookie::new(LOGIN_COOKIE_NAME, login_session);
+            cookie.set_same_site(SameSite::Lax);
+            cookie.set_secure(true);
+            cookie.set_http_only(true);
+            cookie.set_expires(OffsetDateTime::now_utc() + Duration::hours(1));
+            jar = jar.add(cookie);
+
+            Err(Error::Redirect((
+                jar,
+                Redirect::temporary(auth_url.as_str()),
+            )))
+        }
+    }
+}
+
+#[derive(Debug, Deserialize)]
+struct OidcQuery {
+    code: String,
+    state: String,
+    #[allow(dead_code)]
+    session_state: String,
+}
+
+#[derive(Serialize, Deserialize)]
+struct LoginSession {
+    nonce: Nonce,
+    csrf_token: CsrfToken,
+    pkce_verifier: PkceCodeVerifier,
+}