Add reactive support for OAuth 2.0 Token Exchange Grant

Issue gh-5199

oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/TokenExchangeReactiveOAuth2AuthorizedClientProvider.java

@@ -0,0 +1,166 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.oauth2.client;
+
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.function.Function;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.security.oauth2.client.endpoint.ReactiveOAuth2AccessTokenResponseClient;
+import org.springframework.security.oauth2.client.endpoint.TokenExchangeGrantRequest;
+import org.springframework.security.oauth2.client.endpoint.WebClientReactiveTokenExchangeTokenResponseClient;
+import org.springframework.security.oauth2.client.registration.ClientRegistration;
+import org.springframework.security.oauth2.core.AuthorizationGrantType;
+import org.springframework.security.oauth2.core.OAuth2AuthorizationException;
+import org.springframework.security.oauth2.core.OAuth2Token;
+import org.springframework.util.Assert;
+
+/**
+ * An implementation of an {@link ReactiveOAuth2AuthorizedClientProvider} for the
+ * {@link AuthorizationGrantType#TOKEN_EXCHANGE token-exchange} grant.
+ *
+ * @author Steve Riesenberg
+ * @since 6.3
+ * @see ReactiveOAuth2AuthorizedClientProvider
+ * @see WebClientReactiveTokenExchangeTokenResponseClient
+ */
+public final class TokenExchangeReactiveOAuth2AuthorizedClientProvider
+		implements ReactiveOAuth2AuthorizedClientProvider {
+
+	private ReactiveOAuth2AccessTokenResponseClient<TokenExchangeGrantRequest> accessTokenResponseClient = new WebClientReactiveTokenExchangeTokenResponseClient();
+
+	private Function<OAuth2AuthorizationContext, Mono<OAuth2Token>> subjectTokenResolver = this::resolveSubjectToken;
+
+	private Function<OAuth2AuthorizationContext, Mono<OAuth2Token>> actorTokenResolver = (context) -> Mono.empty();
+
+	private Duration clockSkew = Duration.ofSeconds(60);
+
+	private Clock clock = Clock.systemUTC();
+
+	/**
+	 * Attempt to authorize (or re-authorize) the
+	 * {@link OAuth2AuthorizationContext#getClientRegistration() client} in the provided
+	 * {@code context}. Returns an empty {@code Mono} if authorization (or
+	 * re-authorization) is not supported, e.g. the client's
+	 * {@link ClientRegistration#getAuthorizationGrantType() authorization grant type} is
+	 * not {@link AuthorizationGrantType#TOKEN_EXCHANGE token-exchange} OR the
+	 * {@link OAuth2AuthorizedClient#getAccessToken() access token} is not expired.
+	 * @param context the context that holds authorization-specific state for the client
+	 * @return the {@link OAuth2AuthorizedClient} or an empty {@code Mono} if
+	 * authorization is not supported
+	 */
+	@Override
+	public Mono<OAuth2AuthorizedClient> authorize(OAuth2AuthorizationContext context) {
+		Assert.notNull(context, "context cannot be null");
+		ClientRegistration clientRegistration = context.getClientRegistration();
+		if (!AuthorizationGrantType.TOKEN_EXCHANGE.equals(clientRegistration.getAuthorizationGrantType())) {
+			return Mono.empty();
+		}
+		OAuth2AuthorizedClient authorizedClient = context.getAuthorizedClient();
+		if (authorizedClient != null && !hasTokenExpired(authorizedClient.getAccessToken())) {
+			// If client is already authorized but access token is NOT expired than no
+			// need for re-authorization
+			return Mono.empty();
+		}
+
+		return this.subjectTokenResolver.apply(context)
+			.flatMap((subjectToken) -> this.actorTokenResolver.apply(context)
+				.map((actorToken) -> new TokenExchangeGrantRequest(clientRegistration, subjectToken, actorToken))
+				.defaultIfEmpty(new TokenExchangeGrantRequest(clientRegistration, subjectToken, null)))
+			.flatMap(this.accessTokenResponseClient::getTokenResponse)
+			.onErrorMap(OAuth2AuthorizationException.class,
+					(ex) -> new ClientAuthorizationException(ex.getError(), clientRegistration.getRegistrationId(), ex))
+			.map((tokenResponse) -> new OAuth2AuthorizedClient(clientRegistration, context.getPrincipal().getName(),
+					tokenResponse.getAccessToken()));
+	}
+
+	private Mono<OAuth2Token> resolveSubjectToken(OAuth2AuthorizationContext context) {
+		// @formatter:off
+		return Mono.just(context)
+				.map((ctx) -> ctx.getPrincipal().getPrincipal())
+				.filter((principal) -> principal instanceof OAuth2Token)
+				.cast(OAuth2Token.class);
+		// @formatter:on
+	}
+
+	private boolean hasTokenExpired(OAuth2Token token) {
+		return this.clock.instant().isAfter(token.getExpiresAt().minus(this.clockSkew));
+	}
+
+	/**
+	 * Sets the client used when requesting an access token credential at the Token
+	 * Endpoint for the {@code token-exchange} grant.
+	 * @param accessTokenResponseClient the client used when requesting an access token
+	 * credential at the Token Endpoint for the {@code token-exchange} grant
+	 */
+	public void setAccessTokenResponseClient(
+			ReactiveOAuth2AccessTokenResponseClient<TokenExchangeGrantRequest> accessTokenResponseClient) {
+		Assert.notNull(accessTokenResponseClient, "accessTokenResponseClient cannot be null");
+		this.accessTokenResponseClient = accessTokenResponseClient;
+	}
+
+	/**
+	 * Sets the resolver used for resolving the {@link OAuth2Token subject token}.
+	 * @param subjectTokenResolver the resolver used for resolving the {@link OAuth2Token
+	 * subject token}
+	 */
+	public void setSubjectTokenResolver(Function<OAuth2AuthorizationContext, Mono<OAuth2Token>> subjectTokenResolver) {
+		Assert.notNull(subjectTokenResolver, "subjectTokenResolver cannot be null");
+		this.subjectTokenResolver = subjectTokenResolver;
+	}
+
+	/**
+	 * Sets the resolver used for resolving the {@link OAuth2Token actor token}.
+	 * @param actorTokenResolver the resolver used for resolving the {@link OAuth2Token
+	 * actor token}
+	 */
+	public void setActorTokenResolver(Function<OAuth2AuthorizationContext, Mono<OAuth2Token>> actorTokenResolver) {
+		Assert.notNull(actorTokenResolver, "actorTokenResolver cannot be null");
+		this.actorTokenResolver = actorTokenResolver;
+	}
+
+	/**
+	 * Sets the maximum acceptable clock skew, which is used when checking the
+	 * {@link OAuth2AuthorizedClient#getAccessToken() access token} expiry. The default is
+	 * 60 seconds.
+	 *
+	 * <p>
+	 * An access token is considered expired if
+	 * {@code OAuth2AccessToken#getExpiresAt() - clockSkew} is before the current time
+	 * {@code clock#instant()}.
+	 * @param clockSkew the maximum acceptable clock skew
+	 */
+	public void setClockSkew(Duration clockSkew) {
+		Assert.notNull(clockSkew, "clockSkew cannot be null");
+		Assert.isTrue(clockSkew.getSeconds() >= 0, "clockSkew must be >= 0");
+		this.clockSkew = clockSkew;
+	}
+
+	/**
+	 * Sets the {@link Clock} used in {@link Instant#now(Clock)} when checking the access
+	 * token expiry.
+	 * @param clock the clock
+	 */
+	public void setClock(Clock clock) {
+		Assert.notNull(clock, "clock cannot be null");
+		this.clock = clock;
+	}
+
+}

oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/WebClientReactiveTokenExchangeTokenResponseClient.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.oauth2.client.endpoint;
+
+import java.util.Set;
+
+import org.springframework.security.oauth2.client.registration.ClientRegistration;
+import org.springframework.security.oauth2.core.AuthorizationGrantType;
+import org.springframework.security.oauth2.core.OAuth2AccessToken;
+import org.springframework.security.oauth2.core.OAuth2Token;
+import org.springframework.security.oauth2.core.endpoint.OAuth2ParameterNames;
+import org.springframework.security.oauth2.jwt.Jwt;
+import org.springframework.web.reactive.function.BodyInserters;
+import org.springframework.web.reactive.function.client.WebClient;
+
+/**
+ * The default implementation of an {@link ReactiveOAuth2AccessTokenResponseClient} for
+ * the {@link AuthorizationGrantType#TOKEN_EXCHANGE token-exchange} grant. This
+ * implementation uses {@link WebClient} when requesting an access token credential at the
+ * Authorization Server's Token Endpoint.
+ *
+ * @author Steve Riesenberg
+ * @since 6.3
+ * @see ReactiveOAuth2AccessTokenResponseClient
+ * @see TokenExchangeGrantRequest
+ * @see OAuth2AccessToken
+ * @see <a target="_blank" href="https://tools.ietf.org/html/rfc8693#section-2.1">Section
+ * 2.1 Request</a>
+ * @see <a target="_blank" href="https://tools.ietf.org/html/rfc8693#section-2.2">Section
+ * 2.2 Response</a>
+ */
+public final class WebClientReactiveTokenExchangeTokenResponseClient
+		extends AbstractWebClientReactiveOAuth2AccessTokenResponseClient<TokenExchangeGrantRequest> {
+
+	private static final String ACCESS_TOKEN_TYPE_VALUE = "urn:ietf:params:oauth:token-type:access_token";
+
+	private static final String JWT_TOKEN_TYPE_VALUE = "urn:ietf:params:oauth:token-type:jwt";
+
+	@Override
+	ClientRegistration clientRegistration(TokenExchangeGrantRequest grantRequest) {
+		return grantRequest.getClientRegistration();
+	}
+
+	@Override
+	Set<String> scopes(TokenExchangeGrantRequest grantRequest) {
+		return grantRequest.getClientRegistration().getScopes();
+	}
+
+	@Override
+	BodyInserters.FormInserter<String> populateTokenRequestBody(TokenExchangeGrantRequest grantRequest,
+			BodyInserters.FormInserter<String> body) {
+		super.populateTokenRequestBody(grantRequest, body);
+		body.with(OAuth2ParameterNames.REQUESTED_TOKEN_TYPE, ACCESS_TOKEN_TYPE_VALUE);
+		OAuth2Token subjectToken = grantRequest.getSubjectToken();
+		body.with(OAuth2ParameterNames.SUBJECT_TOKEN, subjectToken.getTokenValue());
+		body.with(OAuth2ParameterNames.SUBJECT_TOKEN_TYPE, tokenType(subjectToken));
+		OAuth2Token actorToken = grantRequest.getActorToken();
+		if (actorToken != null) {
+			body.with(OAuth2ParameterNames.ACTOR_TOKEN, actorToken.getTokenValue());
+			body.with(OAuth2ParameterNames.ACTOR_TOKEN_TYPE, tokenType(actorToken));
+		}
+		return body;
+	}
+
+	private static String tokenType(OAuth2Token token) {
+		return (token instanceof Jwt) ? JWT_TOKEN_TYPE_VALUE : ACCESS_TOKEN_TYPE_VALUE;
+	}
+
+}