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// Copyright 2024 New Vector Ltd.
// Copyright 2022-2024 Kévin Commaille.
//
// SPDX-License-Identifier: AGPL-3.0-only
// Please see LICENSE in the repository root for full details.
//! Requests for the [Authorization Code flow].
//!
//! [Authorization Code flow]: https://openid.net/specs/openid-connect-core-1_0.html#CodeFlowAuth
use std::{collections::HashSet, num::NonZeroU32};
use base64ct::{Base64UrlUnpadded, Encoding};
use chrono::{DateTime, Utc};
use language_tags::LanguageTag;
use mas_iana::oauth::{OAuthAuthorizationEndpointResponseType, PkceCodeChallengeMethod};
use mas_jose::claims::{self, TokenHash};
use oauth2_types::{
pkce,
prelude::CodeChallengeMethodExt,
requests::{
AccessTokenRequest, AccessTokenResponse, AuthorizationCodeGrant, AuthorizationRequest,
Display, Prompt,
},
scope::{Scope, OPENID},
};
use rand::{
distributions::{Alphanumeric, DistString},
Rng,
};
use serde::Serialize;
use url::Url;
use super::jose::JwtVerificationData;
use crate::{
error::{AuthorizationError, IdTokenError, TokenAuthorizationCodeError},
requests::{jose::verify_id_token, token::request_access_token},
types::{client_credentials::ClientCredentials, IdToken},
};
/// The data necessary to build an authorization request.
#[derive(Debug, Clone)]
pub struct AuthorizationRequestData {
/// The ID obtained when registering the client.
pub client_id: String,
/// The scope to authorize.
///
/// If the OpenID Connect scope token (`openid`) is not included, it will be
/// added.
pub scope: Scope,
/// The URI to redirect the end-user to after the authorization.
///
/// It must be one of the redirect URIs provided during registration.
pub redirect_uri: Url,
/// The PKCE methods supported by the issuer.
///
/// This field should be cloned from the provider metadata. If it is not
/// set, this security measure will not be used.
pub code_challenge_methods_supported: Option<Vec<PkceCodeChallengeMethod>>,
/// How the Authorization Server should display the authentication and
/// consent user interface pages to the End-User.
pub display: Option<Display>,
/// Whether the Authorization Server should prompt the End-User for
/// reauthentication and consent.
///
/// If [`Prompt::None`] is used, it must be the only value.
pub prompt: Option<Vec<Prompt>>,
/// The allowable elapsed time in seconds since the last time the End-User
/// was actively authenticated by the OpenID Provider.
pub max_age: Option<NonZeroU32>,
/// End-User's preferred languages and scripts for the user interface.
pub ui_locales: Option<Vec<LanguageTag>>,
/// ID Token previously issued by the Authorization Server being passed as a
/// hint about the End-User's current or past authenticated session with the
/// Client.
pub id_token_hint: Option<String>,
/// Hint to the Authorization Server about the login identifier the End-User
/// might use to log in.
pub login_hint: Option<String>,
/// Requested Authentication Context Class Reference values.
pub acr_values: Option<HashSet<String>>,
}
impl AuthorizationRequestData {
/// Constructs a new `AuthorizationRequestData` with all the required
/// fields.
#[must_use]
pub fn new(client_id: String, scope: Scope, redirect_uri: Url) -> Self {
Self {
client_id,
scope,
redirect_uri,
code_challenge_methods_supported: None,
display: None,
prompt: None,
max_age: None,
ui_locales: None,
id_token_hint: None,
login_hint: None,
acr_values: None,
}
}
/// Set the `code_challenge_methods_supported` field of this
/// `AuthorizationRequestData`.
#[must_use]
pub fn with_code_challenge_methods_supported(
mut self,
code_challenge_methods_supported: Vec<PkceCodeChallengeMethod>,
) -> Self {
self.code_challenge_methods_supported = Some(code_challenge_methods_supported);
self
}
/// Set the `display` field of this `AuthorizationRequestData`.
#[must_use]
pub fn with_display(mut self, display: Display) -> Self {
self.display = Some(display);
self
}
/// Set the `prompt` field of this `AuthorizationRequestData`.
#[must_use]
pub fn with_prompt(mut self, prompt: Vec<Prompt>) -> Self {
self.prompt = Some(prompt);
self
}
/// Set the `max_age` field of this `AuthorizationRequestData`.
#[must_use]
pub fn with_max_age(mut self, max_age: NonZeroU32) -> Self {
self.max_age = Some(max_age);
self
}
/// Set the `ui_locales` field of this `AuthorizationRequestData`.
#[must_use]
pub fn with_ui_locales(mut self, ui_locales: Vec<LanguageTag>) -> Self {
self.ui_locales = Some(ui_locales);
self
}
/// Set the `id_token_hint` field of this `AuthorizationRequestData`.
#[must_use]
pub fn with_id_token_hint(mut self, id_token_hint: String) -> Self {
self.id_token_hint = Some(id_token_hint);
self
}
/// Set the `login_hint` field of this `AuthorizationRequestData`.
#[must_use]
pub fn with_login_hint(mut self, login_hint: String) -> Self {
self.login_hint = Some(login_hint);
self
}
/// Set the `acr_values` field of this `AuthorizationRequestData`.
#[must_use]
pub fn with_acr_values(mut self, acr_values: HashSet<String>) -> Self {
self.acr_values = Some(acr_values);
self
}
}
/// The data necessary to validate a response from the Token endpoint in the
/// Authorization Code flow.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct AuthorizationValidationData {
/// A unique identifier for the request.
pub state: String,
/// A string to mitigate replay attacks.
pub nonce: String,
/// The URI where the end-user will be redirected after authorization.
pub redirect_uri: Url,
/// A string to correlate the authorization request to the token request.
pub code_challenge_verifier: Option<String>,
}
#[derive(Clone, Serialize)]
struct FullAuthorizationRequest {
#[serde(flatten)]
inner: AuthorizationRequest,
#[serde(flatten, skip_serializing_if = "Option::is_none")]
pkce: Option<pkce::AuthorizationRequest>,
}
/// Build the authorization request.
fn build_authorization_request(
authorization_data: AuthorizationRequestData,
rng: &mut impl Rng,
) -> Result<(FullAuthorizationRequest, AuthorizationValidationData), AuthorizationError> {
let AuthorizationRequestData {
client_id,
mut scope,
redirect_uri,
code_challenge_methods_supported,
display,
prompt,
max_age,
ui_locales,
id_token_hint,
login_hint,
acr_values,
} = authorization_data;
// Generate a random CSRF "state" token and a nonce.
let state = Alphanumeric.sample_string(rng, 16);
let nonce = Alphanumeric.sample_string(rng, 16);
// Use PKCE, whenever possible.
let (pkce, code_challenge_verifier) = if code_challenge_methods_supported
.iter()
.any(|methods| methods.contains(&PkceCodeChallengeMethod::S256))
{
let mut verifier = [0u8; 32];
rng.fill(&mut verifier);
let method = PkceCodeChallengeMethod::S256;
let verifier = Base64UrlUnpadded::encode_string(&verifier);
let code_challenge = method.compute_challenge(&verifier)?.into();
let pkce = pkce::AuthorizationRequest {
code_challenge_method: method,
code_challenge,
};
(Some(pkce), Some(verifier))
} else {
(None, None)
};
scope.insert(OPENID);
let auth_request = FullAuthorizationRequest {
inner: AuthorizationRequest {
response_type: OAuthAuthorizationEndpointResponseType::Code.into(),
client_id,
redirect_uri: Some(redirect_uri.clone()),
scope,
state: Some(state.clone()),
response_mode: None,
nonce: Some(nonce.clone()),
display,
prompt,
max_age,
ui_locales,
id_token_hint,
login_hint,
acr_values,
request: None,
request_uri: None,
registration: None,
},
pkce,
};
let auth_data = AuthorizationValidationData {
state,
nonce,
redirect_uri,
code_challenge_verifier,
};
Ok((auth_request, auth_data))
}
/// Build the URL for authenticating at the Authorization endpoint.
///
/// # Arguments
///
/// * `authorization_endpoint` - The URL of the issuer's authorization endpoint.
///
/// * `authorization_data` - The data necessary to build the authorization
/// request.
///
/// * `rng` - A random number generator.
///
/// # Returns
///
/// A URL to be opened in a web browser where the end-user will be able to
/// authorize the given scope, and the [`AuthorizationValidationData`] to
/// validate this request.
///
/// The redirect URI will receive parameters in its query:
///
/// * A successful response will receive a `code` and a `state`.
///
/// * If the authorization fails, it should receive an `error` parameter with a
/// [`ClientErrorCode`] and optionally an `error_description`.
///
/// # Errors
///
/// Returns an error if preparing the URL fails.
///
/// [`VerifiedClientMetadata`]: oauth2_types::registration::VerifiedClientMetadata
/// [`ClientErrorCode`]: oauth2_types::errors::ClientErrorCode
pub fn build_authorization_url(
authorization_endpoint: Url,
authorization_data: AuthorizationRequestData,
rng: &mut impl Rng,
) -> Result<(Url, AuthorizationValidationData), AuthorizationError> {
tracing::debug!(
scope = ?authorization_data.scope,
"Authorizing..."
);
let (authorization_request, validation_data) =
build_authorization_request(authorization_data, rng)?;
let authorization_query = serde_urlencoded::to_string(authorization_request)?;
let mut authorization_url = authorization_endpoint;
// Add our parameters to the query, because the URL might already have one.
let mut full_query = authorization_url
.query()
.map(ToOwned::to_owned)
.unwrap_or_default();
if !full_query.is_empty() {
full_query.push('&');
}
full_query.push_str(&authorization_query);
authorization_url.set_query(Some(&full_query));
Ok((authorization_url, validation_data))
}
/// Exchange an authorization code for an access token.
///
/// This should be used as the first step for logging in, and to request a
/// token with a new scope.
///
/// # Arguments
///
/// * `http_client` - The reqwest client to use for making HTTP requests.
///
/// * `client_credentials` - The credentials obtained when registering the
/// client.
///
/// * `token_endpoint` - The URL of the issuer's Token endpoint.
///
/// * `code` - The authorization code returned at the Authorization endpoint.
///
/// * `validation_data` - The validation data that was returned when building
/// the Authorization URL, for the state returned at the Authorization
/// endpoint.
///
/// * `id_token_verification_data` - The data required to verify the ID Token in
/// the response.
///
/// The signing algorithm corresponds to the `id_token_signed_response_alg`
/// field in the client metadata.
///
/// If it is not provided, the ID Token won't be verified. Note that in the
/// OpenID Connect specification, this verification is required.
///
/// * `now` - The current time.
///
/// * `rng` - A random number generator.
///
/// # Errors
///
/// Returns an error if the request fails, the response is invalid or the
/// verification of the ID Token fails.
#[allow(clippy::too_many_arguments)]
#[tracing::instrument(skip_all, fields(token_endpoint))]
pub async fn access_token_with_authorization_code(
http_client: &reqwest::Client,
client_credentials: ClientCredentials,
token_endpoint: &Url,
code: String,
validation_data: AuthorizationValidationData,
id_token_verification_data: Option<JwtVerificationData<'_>>,
now: DateTime<Utc>,
rng: &mut impl Rng,
) -> Result<(AccessTokenResponse, Option<IdToken<'static>>), TokenAuthorizationCodeError> {
tracing::debug!("Exchanging authorization code for access token...");
let token_response = request_access_token(
http_client,
client_credentials,
token_endpoint,
AccessTokenRequest::AuthorizationCode(AuthorizationCodeGrant {
code: code.clone(),
redirect_uri: Some(validation_data.redirect_uri),
code_verifier: validation_data.code_challenge_verifier,
}),
now,
rng,
)
.await?;
let id_token = if let Some(verification_data) = id_token_verification_data {
let signing_alg = verification_data.signing_algorithm;
let id_token = token_response
.id_token
.as_deref()
.ok_or(IdTokenError::MissingIdToken)?;
let id_token = verify_id_token(id_token, verification_data, None, now)?;
let mut claims = id_token.payload().clone();
// Access token hash must match.
claims::AT_HASH
.extract_optional_with_options(
&mut claims,
TokenHash::new(signing_alg, &token_response.access_token),
)
.map_err(IdTokenError::from)?;
// Code hash must match.
claims::C_HASH
.extract_optional_with_options(&mut claims, TokenHash::new(signing_alg, &code))
.map_err(IdTokenError::from)?;
// Nonce must match.
claims::NONCE
.extract_required_with_options(&mut claims, validation_data.nonce.as_str())
.map_err(IdTokenError::from)?;
Some(id_token.into_owned())
} else {
None
};
Ok((token_response, id_token))
}