kube_client/client/auth/

oidc.rs

use super::TEN_SEC;
use form_urlencoded::Serializer;
use http::{
    Method, Request, Uri, Version,
    header::{AUTHORIZATION, CONTENT_TYPE, HeaderValue},
};
use http_body_util::BodyExt;
use hyper_util::{
    client::legacy::{Client, connect::HttpConnector},
    rt::TokioExecutor,
};
use secrecy::{ExposeSecret, SecretString};
use serde::{Deserialize, Deserializer};
use serde_json::Number;
use std::collections::HashMap;

/// Possible errors when handling OIDC authentication.
pub mod errors {
    use super::Oidc;
    use http::{StatusCode, uri::InvalidUri};
    use thiserror::Error;

    /// Possible errors when extracting expiration time from an ID token.
    #[derive(Error, Debug)]
    pub enum IdTokenError {
        /// Failed to extract payload from the ID token.
        #[error("not a valid JWT token")]
        InvalidFormat,
        /// ID token payload is not properly encoded in base64.
        #[error("failed to decode base64: {0}")]
        InvalidBase64(
            #[source]
            #[from]
            base64::DecodeError,
        ),
        /// ID token payload is not valid JSON object containing expiration timestamp.
        #[error("failed to unmarshal JSON: {0}")]
        InvalidJson(
            #[source]
            #[from]
            serde_json::Error,
        ),
        /// Expiration timestamp extracted from the ID token payload is not valid.
        #[error("invalid expiration timestamp: {0}")]
        InvalidExpirationTimestamp(
            #[source]
            #[from]
            jiff::Error,
        ),
    }

    /// Possible error when initializing the ID token refreshing.
    #[derive(Error, Debug, Clone)]
    pub enum RefreshInitError {
        /// Missing field in the configuration.
        #[error("missing field {0}")]
        MissingField(&'static str),
        /// Failed to create an HTTPS client.
        #[cfg(feature = "openssl-tls")]
        #[cfg_attr(docsrs, doc(cfg(feature = "openssl-tls")))]
        #[error("failed to create OpenSSL HTTPS connector: {0}")]
        CreateOpensslHttpsConnector(
            #[source]
            #[from]
            openssl::error::ErrorStack,
        ),
        /// No valid native root CA certificates found
        #[error("No valid native root CA certificates found")]
        NoValidNativeRootCA,
    }

    /// Possible errors when using the refresh token.
    #[derive(Error, Debug)]
    pub enum RefreshError {
        /// Failed to parse the provided issuer URL.
        #[error("invalid URI: {0}")]
        InvalidURI(
            #[source]
            #[from]
            InvalidUri,
        ),
        /// [`hyper::Error`] occurred during refreshing.
        #[error("hyper error: {0}")]
        HyperError(
            #[source]
            #[from]
            hyper::Error,
        ),
        /// [`hyper_util::client::legacy::Error`] occurred during refreshing.
        #[error("hyper-util error: {0}")]
        HyperUtilError(
            #[source]
            #[from]
            hyper_util::client::legacy::Error,
        ),
        /// Failed to parse the metadata received from the provider.
        #[error("invalid metadata received from the provider: {0}")]
        InvalidMetadata(#[source] serde_json::Error),
        /// Received an invalid status code from the provider.
        #[error("request failed with status code: {0}")]
        RequestFailed(StatusCode),
        /// [`http::Error`] occurred during refreshing.
        #[error("http error: {0}")]
        HttpError(
            #[source]
            #[from]
            http::Error,
        ),
        /// Failed to authorize with the provider.
        #[error("failed to authorize with the provider using any of known authorization styles")]
        AuthorizationFailure,
        /// Failed to parse the token response from the provider.
        #[error("invalid token response received from the provider: {0}")]
        InvalidTokenResponse(#[source] serde_json::Error),
        /// Token response from the provider did not contain an ID token.
        #[error("no ID token received from the provider")]
        NoIdTokenReceived,
    }

    /// Possible errors when dealing with OIDC.
    #[derive(Error, Debug)]
    pub enum Error {
        /// Config did not contain the ID token.
        #[error("missing field {}", Oidc::CONFIG_ID_TOKEN)]
        IdTokenMissing,
        /// Failed to retrieve expiration timestamp from the ID token.
        #[error("invalid ID token: {0}")]
        IdToken(
            #[source]
            #[from]
            IdTokenError,
        ),
        /// Failed to initialize ID token refreshing.
        #[error("ID token expired and refreshing is not possible: {0}")]
        RefreshInit(
            #[source]
            #[from]
            RefreshInitError,
        ),
        /// Failed to refresh the ID token.
        #[error("ID token expired and refreshing failed: {0}")]
        Refresh(
            #[source]
            #[from]
            RefreshError,
        ),
    }
}

use base64::Engine as _;
const JWT_BASE64_ENGINE: base64::engine::GeneralPurpose = base64::engine::GeneralPurpose::new(
    &base64::alphabet::URL_SAFE,
    base64::engine::GeneralPurposeConfig::new()
        .with_decode_allow_trailing_bits(true)
        .with_decode_padding_mode(base64::engine::DecodePaddingMode::Indifferent),
);
use base64::engine::general_purpose::STANDARD as STANDARD_BASE64_ENGINE;
use jiff::Timestamp;

#[derive(Debug)]
pub struct Oidc {
    id_token: SecretString,
    refresher: Result<Refresher, errors::RefreshInitError>,
}

impl Oidc {
    /// Config key for the ID token.
    const CONFIG_ID_TOKEN: &'static str = "id-token";

    /// Check whether the stored ID token can still be used.
    fn token_valid(&self) -> Result<bool, errors::IdTokenError> {
        let part = self
            .id_token
            .expose_secret()
            .split('.')
            .nth(1)
            .ok_or(errors::IdTokenError::InvalidFormat)?;
        let payload = JWT_BASE64_ENGINE.decode(part)?;
        let expiry = serde_json::from_slice::<Claims>(&payload)?.expiry;
        let timestamp = Timestamp::from_second(expiry)?;

        let valid = Timestamp::now() + TEN_SEC < timestamp;

        Ok(valid)
    }

    /// Retrieve the ID token. If the stored ID token is or will soon be expired, try refreshing it first.
    pub async fn id_token(&mut self) -> Result<String, errors::Error> {
        if self.token_valid()? {
            return Ok(self.id_token.expose_secret().to_string());
        }

        let id_token = self.refresher.as_mut().map_err(|e| e.clone())?.id_token().await?;

        self.id_token = id_token.clone().into();

        Ok(id_token)
    }

    /// Create an instance of this struct from the auth provider config.
    pub fn from_config(config: &HashMap<String, String>) -> Result<Self, errors::Error> {
        let id_token = config
            .get(Self::CONFIG_ID_TOKEN)
            .ok_or(errors::Error::IdTokenMissing)?
            .clone()
            .into();
        let refresher = Refresher::from_config(config);

        Ok(Self { id_token, refresher })
    }
}

/// Claims extracted from the ID token. Only expiration time here is important.
#[derive(Deserialize)]
struct Claims {
    #[serde(rename = "exp", deserialize_with = "deserialize_expiry")]
    expiry: i64,
}

/// Deserialize expiration time from a JSON number.
fn deserialize_expiry<'de, D: Deserializer<'de>>(deserializer: D) -> core::result::Result<i64, D::Error> {
    let json_number = Number::deserialize(deserializer)?;

    json_number
        .as_i64()
        .or_else(|| Some(json_number.as_f64()? as i64))
        .ok_or(serde::de::Error::custom("cannot be casted to i64"))
}

/// Metadata retrieved from the provider. Only token endpoint here is important.
#[derive(Deserialize)]
struct Metadata {
    token_endpoint: String,
}

/// Authorization styles used by different providers.
/// Some providers require the authorization info in the header, some in the request body.
/// Some providers reject requests when authorization info is passed in both.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum AuthStyle {
    Header,
    Params,
}

impl AuthStyle {
    /// All known authorization styles.
    const ALL: [Self; 2] = [Self::Header, Self::Params];
}

/// Token response from the provider. Only refresh token and id token here are important.
#[derive(Deserialize)]
struct TokenResponse {
    refresh_token: Option<String>,
    id_token: Option<String>,
}

#[cfg(all(feature = "rustls-tls", not(any(feature = "ring", feature = "aws-lc-rs"))))]
compile_error!("At least one of ring or aws-lc-rs feature must be enabled to use rustls-tls feature");

#[cfg(not(any(feature = "rustls-tls", feature = "openssl-tls")))]
compile_error!(
    "At least one of rustls-tls or openssl-tls feature must be enabled to use refresh-oidc feature"
);
// Current TLS feature precedence when more than one are set:
// 1. rustls-tls
// 2. openssl-tls
#[cfg(feature = "rustls-tls")]
type HttpsConnector = hyper_rustls::HttpsConnector<HttpConnector>;
#[cfg(all(not(feature = "rustls-tls"), feature = "openssl-tls"))]
type HttpsConnector = hyper_openssl::client::legacy::HttpsConnector<HttpConnector>;

/// Struct for refreshing the ID token with the refresh token.
#[derive(Debug)]
struct Refresher {
    issuer: String,
    /// Token endpoint exposed by the provider.
    /// Retrieved from the provider metadata with the first refresh request.
    token_endpoint: Option<String>,
    /// Refresh token used in the refresh requests.
    /// Updated when a new refresh token is returned by the provider.
    refresh_token: SecretString,
    client_id: SecretString,
    client_secret: SecretString,
    https_client: Client<HttpsConnector, String>,
    /// Authorization style used by the provider.
    /// Determined with the first refresh request by trying all known styles.
    auth_style: Option<AuthStyle>,
}

impl Refresher {
    /// Config key for the client ID.
    const CONFIG_CLIENT_ID: &'static str = "client-id";
    /// Config key for the client secret.
    const CONFIG_CLIENT_SECRET: &'static str = "client-secret";
    /// Config key for the issuer url.
    const CONFIG_ISSUER_URL: &'static str = "idp-issuer-url";
    /// Config key for the refresh token.
    const CONFIG_REFRESH_TOKEN: &'static str = "refresh-token";

    /// Create a new instance of this struct from the provider config.
    fn from_config(config: &HashMap<String, String>) -> Result<Self, errors::RefreshInitError> {
        let get_field = |name: &'static str| {
            config
                .get(name)
                .cloned()
                .ok_or(errors::RefreshInitError::MissingField(name))
        };

        let issuer = get_field(Self::CONFIG_ISSUER_URL)?;
        let refresh_token = get_field(Self::CONFIG_REFRESH_TOKEN)?.into();
        let client_id = get_field(Self::CONFIG_CLIENT_ID)?.into();
        let client_secret = get_field(Self::CONFIG_CLIENT_SECRET)?.into();

        #[cfg(all(feature = "rustls-tls", feature = "aws-lc-rs"))]
        {
            if rustls::crypto::CryptoProvider::get_default().is_none() {
                // the only error here is if it's been initialized in between: we can ignore it
                // since our semantic is only to set the default value if it does not exist.
                let _ = rustls::crypto::aws_lc_rs::default_provider().install_default();
            }
        }

        #[cfg(all(feature = "rustls-tls", not(feature = "webpki-roots")))]
        let https = hyper_rustls::HttpsConnectorBuilder::new()
            .with_native_roots()
            .map_err(|_| errors::RefreshInitError::NoValidNativeRootCA)?
            .https_only()
            .enable_http1()
            .build();
        #[cfg(all(feature = "rustls-tls", feature = "webpki-roots"))]
        let https = hyper_rustls::HttpsConnectorBuilder::new()
            .with_webpki_roots()
            .https_only()
            .enable_http1()
            .build();
        #[cfg(all(not(feature = "rustls-tls"), feature = "openssl-tls"))]
        let https = hyper_openssl::client::legacy::HttpsConnector::new()?;

        let https_client = hyper_util::client::legacy::Client::builder(TokioExecutor::new()).build(https);

        Ok(Self {
            issuer,
            token_endpoint: None,
            refresh_token,
            client_id,
            client_secret,
            https_client,
            auth_style: None,
        })
    }

    /// If the token endpoint is not yet cached in this struct, extract it from the provider metadata and store in the cache.
    /// Provider metadata is retrieved from a well-known path.
    async fn token_endpoint(&mut self) -> Result<String, errors::RefreshError> {
        if let Some(endpoint) = self.token_endpoint.clone() {
            return Ok(endpoint);
        }

        let discovery = format!("{}/.well-known/openid-configuration", self.issuer).parse::<Uri>()?;
        let response = self.https_client.get(discovery).await?;

        if response.status().is_success() {
            let body = response.into_body().collect().await?.to_bytes();
            let metadata = serde_json::from_slice::<Metadata>(body.as_ref())
                .map_err(errors::RefreshError::InvalidMetadata)?;

            self.token_endpoint.replace(metadata.token_endpoint.clone());

            Ok(metadata.token_endpoint)
        } else {
            Err(errors::RefreshError::RequestFailed(response.status()))
        }
    }

    /// Prepare a token request to the provider.
    fn token_request(
        &self,
        endpoint: &str,
        auth_style: AuthStyle,
    ) -> Result<Request<String>, errors::RefreshError> {
        let mut builder = Request::builder()
            .uri(endpoint)
            .method(Method::POST)
            .header(
                CONTENT_TYPE,
                HeaderValue::from_static("application/x-www-form-urlencoded"),
            )
            .version(Version::HTTP_11);
        let mut params = vec![
            ("grant_type", "refresh_token"),
            ("refresh_token", self.refresh_token.expose_secret()),
        ];

        match auth_style {
            AuthStyle::Header => {
                builder = builder.header(
                    AUTHORIZATION,
                    format!(
                        "Basic {}",
                        STANDARD_BASE64_ENGINE.encode(format!(
                            "{}:{}",
                            self.client_id.expose_secret(),
                            self.client_secret.expose_secret()
                        ))
                    ),
                );
            }
            AuthStyle::Params => {
                params.extend([
                    ("client_id", self.client_id.expose_secret()),
                    ("client_secret", self.client_secret.expose_secret()),
                ]);
            }
        };

        let body = Serializer::new(String::new()).extend_pairs(params).finish();

        builder.body(body).map_err(Into::into)
    }

    /// Fetch a new ID token from the provider.
    async fn id_token(&mut self) -> Result<String, errors::RefreshError> {
        let token_endpoint = self.token_endpoint().await?;

        let response = match self.auth_style {
            Some(style) => {
                let request = self.token_request(&token_endpoint, style)?;
                self.https_client.request(request).await?
            }
            None => {
                let mut ok_response = None;

                for style in AuthStyle::ALL {
                    let request = self.token_request(&token_endpoint, style)?;
                    let response = self.https_client.request(request).await?;
                    if response.status().is_success() {
                        ok_response.replace(response);
                        self.auth_style.replace(style);
                        break;
                    }
                }

                ok_response.ok_or(errors::RefreshError::AuthorizationFailure)?
            }
        };

        if !response.status().is_success() {
            return Err(errors::RefreshError::RequestFailed(response.status()));
        }

        let body = response.into_body().collect().await?.to_bytes();
        let token_response = serde_json::from_slice::<TokenResponse>(body.as_ref())
            .map_err(errors::RefreshError::InvalidTokenResponse)?;

        if let Some(token) = token_response.refresh_token {
            self.refresh_token = token.into();
        }

        token_response
            .id_token
            .ok_or(errors::RefreshError::NoIdTokenReceived)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn token_valid() {
        let mut oidc = Oidc {
            id_token: String::new().into(),
            refresher: Err(errors::RefreshInitError::MissingField(
                Refresher::CONFIG_REFRESH_TOKEN,
            )),
        };

        // Proper JWT expiring at 2123-06-28T15:18:12.629Z
        let token_valid = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9\
.eyJpc3MiOiJPbmxpbmUgSldUIEJ1aWxkZXIiLCJpYXQiOjE2ODc5NjU0NTIsImV4cCI6NDg0MzYzOTA5MiwiYXVkIjoid3d3LmV4YW1wbGUuY29tIiwic3ViIjoianJvY2tldEBleGFtcGxlLmNvbSIsIkVtYWlsIjoiYmVlQGV4YW1wbGUuY29tIn0\
.GKTkPMywcNQv0n01iBfv_A6VuCCCcAe72RhP0OrZsQM";
        // Proper JWT expired at 2023-06-28T15:19:53.421Z
        let token_expired = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9\
.eyJpc3MiOiJPbmxpbmUgSldUIEJ1aWxkZXIiLCJpYXQiOjE2ODc5NjU0NTIsImV4cCI6MTY4Nzk2NTU5MywiYXVkIjoid3d3LmV4YW1wbGUuY29tIiwic3ViIjoianJvY2tldEBleGFtcGxlLmNvbSIsIkVtYWlsIjoiYmVlQGV4YW1wbGUuY29tIn0\
.zTDnfI_zXIa6yPKY_ZE8r6GoLK7Syj-URcTU5_ryv1M";

        oidc.id_token = token_valid.to_string().into();
        assert!(oidc.token_valid().expect("proper token failed validation"));

        oidc.id_token = token_expired.to_string().into();
        assert!(!oidc.token_valid().expect("proper token failed validation"));

        let malformed_token = token_expired.split_once('.').unwrap().0.to_string();
        oidc.id_token = malformed_token.into();
        oidc.token_valid().expect_err("malformed token passed validation");

        let invalid_base64_token = token_valid
            .split_once('.')
            .map(|(prefix, suffix)| format!("{}.?{}", prefix, suffix))
            .unwrap();
        oidc.id_token = invalid_base64_token.into();
        oidc.token_valid()
            .expect_err("token with invalid base64 encoding passed validation");

        let invalid_claims = [("sub", "jrocket@example.com"), ("aud", "www.example.com")]
            .into_iter()
            .collect::<HashMap<_, _>>();
        let invalid_claims_token = format!(
            "{}.{}.{}",
            token_valid.split_once('.').unwrap().0,
            JWT_BASE64_ENGINE.encode(serde_json::to_string(&invalid_claims).unwrap()),
            token_valid.rsplit_once('.').unwrap().1,
        );
        oidc.id_token = invalid_claims_token.into();
        oidc.token_valid()
            .expect_err("token without expiration timestamp passed validation");
    }

    #[cfg(any(feature = "openssl-tls", feature = "rustls-tls"))]
    #[test]
    fn from_minimal_config() {
        let minimal_config = [(Oidc::CONFIG_ID_TOKEN.into(), "some_id_token".into())]
            .into_iter()
            .collect();

        let oidc = Oidc::from_config(&minimal_config)
            .expect("failed to create oidc from minimal config (only id-token)");
        assert_eq!(oidc.id_token.expose_secret(), "some_id_token");
        assert!(oidc.refresher.is_err());
    }

    #[cfg(any(feature = "openssl-tls", feature = "rustls-tls"))]
    #[test]
    fn from_full_config() {
        let full_config = [
            (Oidc::CONFIG_ID_TOKEN.into(), "some_id_token".into()),
            (Refresher::CONFIG_ISSUER_URL.into(), "some_issuer".into()),
            (
                Refresher::CONFIG_REFRESH_TOKEN.into(),
                "some_refresh_token".into(),
            ),
            (Refresher::CONFIG_CLIENT_ID.into(), "some_client_id".into()),
            (
                Refresher::CONFIG_CLIENT_SECRET.into(),
                "some_client_secret".into(),
            ),
        ]
        .into_iter()
        .collect();

        let oidc = Oidc::from_config(&full_config).expect("failed to create oidc from full config");
        assert_eq!(oidc.id_token.expose_secret(), "some_id_token");
        let refresher = oidc
            .refresher
            .as_ref()
            .expect("failed to create oidc refresher from full config");
        assert_eq!(refresher.issuer, "some_issuer");
        assert_eq!(refresher.token_endpoint, None);
        assert_eq!(refresher.refresh_token.expose_secret(), "some_refresh_token");
        assert_eq!(refresher.client_id.expose_secret(), "some_client_id");
        assert_eq!(refresher.client_secret.expose_secret(), "some_client_secret");
        assert_eq!(refresher.auth_style, None);
    }
}