/*
 * Copyright 2002-2019 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.oidc.authentication;

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Base64;
import java.util.Collection;
import java.util.Map;

import org.springframework.security.authentication.AuthenticationProvider;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.authority.mapping.GrantedAuthoritiesMapper;
import org.springframework.security.oauth2.client.authentication.OAuth2LoginAuthenticationToken;
import org.springframework.security.oauth2.client.endpoint.OAuth2AccessTokenResponseClient;
import org.springframework.security.oauth2.client.endpoint.OAuth2AuthorizationCodeGrantRequest;
import org.springframework.security.oauth2.client.oidc.userinfo.OidcUserRequest;
import org.springframework.security.oauth2.client.oidc.userinfo.OidcUserService;
import org.springframework.security.oauth2.client.registration.ClientRegistration;
import org.springframework.security.oauth2.client.userinfo.OAuth2UserService;
import org.springframework.security.oauth2.core.OAuth2AuthenticationException;
import org.springframework.security.oauth2.core.OAuth2AuthorizationException;
import org.springframework.security.oauth2.core.OAuth2Error;
import org.springframework.security.oauth2.core.endpoint.OAuth2AccessTokenResponse;
import org.springframework.security.oauth2.core.endpoint.OAuth2AuthorizationRequest;
import org.springframework.security.oauth2.core.endpoint.OAuth2AuthorizationResponse;
import org.springframework.security.oauth2.core.oidc.OidcIdToken;
import org.springframework.security.oauth2.core.oidc.OidcScopes;
import org.springframework.security.oauth2.core.oidc.endpoint.OidcParameterNames;
import org.springframework.security.oauth2.core.oidc.user.OidcUser;
import org.springframework.security.oauth2.jwt.Jwt;
import org.springframework.security.oauth2.jwt.JwtDecoder;
import org.springframework.security.oauth2.jwt.JwtDecoderFactory;
import org.springframework.security.oauth2.jwt.JwtException;
import org.springframework.util.Assert;

/**
 * An implementation of an {@link AuthenticationProvider} for the OpenID Connect Core 1.0
 * Authorization Code Grant Flow.
 * <p>
 * This {@link AuthenticationProvider} is responsible for authenticating an Authorization
 * Code credential with the Authorization Server's Token Endpoint and if valid, exchanging
 * it for an Access Token credential.
 * <p>
 * It will also obtain the user attributes of the End-User (Resource Owner) from the
 * UserInfo Endpoint using an {@link OAuth2UserService}, which will create a
 * {@code Principal} in the form of an {@link OidcUser}. The {@code OidcUser} is then
 * associated to the {@link OAuth2LoginAuthenticationToken} to complete the
 * authentication.
 *
 * @author Joe Grandja
 * @author Mark Heckler
 * @since 5.0
 * @see OAuth2LoginAuthenticationToken
 * @see OAuth2AccessTokenResponseClient
 * @see OidcUserService
 * @see OidcUser
 * @see OidcIdTokenDecoderFactory
 * @see <a target="_blank" href=
 * "https://openid.net/specs/openid-connect-core-1_0.html#CodeFlowAuth">Section 3.1
 * Authorization Code Grant Flow</a>
 * @see <a target="_blank" href=
 * "https://openid.net/specs/openid-connect-core-1_0.html#TokenRequest">Section 3.1.3.1
 * Token Request</a>
 * @see <a target="_blank" href=
 * "https://openid.net/specs/openid-connect-core-1_0.html#TokenResponse">Section 3.1.3.3
 * Token Response</a>
 */
public class OidcAuthorizationCodeAuthenticationProvider implements AuthenticationProvider {

	private static final String INVALID_STATE_PARAMETER_ERROR_CODE = "invalid_state_parameter";

	private static final String INVALID_ID_TOKEN_ERROR_CODE = "invalid_id_token";

	private static final String INVALID_NONCE_ERROR_CODE = "invalid_nonce";

	private final OAuth2AccessTokenResponseClient<OAuth2AuthorizationCodeGrantRequest> accessTokenResponseClient;

	private final OAuth2UserService<OidcUserRequest, OidcUser> userService;

	private JwtDecoderFactory<ClientRegistration> jwtDecoderFactory = new OidcIdTokenDecoderFactory();

	private GrantedAuthoritiesMapper authoritiesMapper = ((authorities) -> authorities);

	/**
	 * Constructs an {@code OidcAuthorizationCodeAuthenticationProvider} using the
	 * provided parameters.
	 * @param accessTokenResponseClient the client used for requesting the access token
	 * credential from the Token Endpoint
	 * @param userService the service used for obtaining the user attributes of the
	 * End-User from the UserInfo Endpoint
	 */
	public OidcAuthorizationCodeAuthenticationProvider(
			OAuth2AccessTokenResponseClient<OAuth2AuthorizationCodeGrantRequest> accessTokenResponseClient,
			OAuth2UserService<OidcUserRequest, OidcUser> userService) {
		Assert.notNull(accessTokenResponseClient, "accessTokenResponseClient cannot be null");
		Assert.notNull(userService, "userService cannot be null");
		this.accessTokenResponseClient = accessTokenResponseClient;
		this.userService = userService;
	}

	@Override
	public Authentication authenticate(Authentication authentication) throws AuthenticationException {
		OAuth2LoginAuthenticationToken authorizationCodeAuthentication = (OAuth2LoginAuthenticationToken) authentication;
		// Section 3.1.2.1 Authentication Request -
		// https://openid.net/specs/openid-connect-core-1_0.html#AuthRequest
		// scope
		// REQUIRED. OpenID Connect requests MUST contain the "openid" scope value.
		if (!authorizationCodeAuthentication.getAuthorizationExchange().getAuthorizationRequest().getScopes()
				.contains(OidcScopes.OPENID)) {
			// This is NOT an OpenID Connect Authentication Request so return null
			// and let OAuth2LoginAuthenticationProvider handle it instead
			return null;
		}
		OAuth2AuthorizationRequest authorizationRequest = authorizationCodeAuthentication.getAuthorizationExchange()
				.getAuthorizationRequest();
		OAuth2AuthorizationResponse authorizationResponse = authorizationCodeAuthentication.getAuthorizationExchange()
				.getAuthorizationResponse();
		if (authorizationResponse.statusError()) {
			throw new OAuth2AuthenticationException(authorizationResponse.getError(),
					authorizationResponse.getError().toString());
		}
		if (!authorizationResponse.getState().equals(authorizationRequest.getState())) {
			OAuth2Error oauth2Error = new OAuth2Error(INVALID_STATE_PARAMETER_ERROR_CODE);
			throw new OAuth2AuthenticationException(oauth2Error, oauth2Error.toString());
		}
		OAuth2AccessTokenResponse accessTokenResponse = getResponse(authorizationCodeAuthentication);
		ClientRegistration clientRegistration = authorizationCodeAuthentication.getClientRegistration();
		Map<String, Object> additionalParameters = accessTokenResponse.getAdditionalParameters();
		if (!additionalParameters.containsKey(OidcParameterNames.ID_TOKEN)) {
			OAuth2Error invalidIdTokenError = new OAuth2Error(INVALID_ID_TOKEN_ERROR_CODE,
					"Missing (required) ID Token in Token Response for Client Registration: "
							+ clientRegistration.getRegistrationId(),
					null);
			throw new OAuth2AuthenticationException(invalidIdTokenError, invalidIdTokenError.toString());
		}
		OidcIdToken idToken = createOidcToken(clientRegistration, accessTokenResponse);
		validateNonce(authorizationRequest, idToken);
		OidcUser oidcUser = this.userService.loadUser(new OidcUserRequest(clientRegistration,
				accessTokenResponse.getAccessToken(), idToken, additionalParameters));
		Collection<? extends GrantedAuthority> mappedAuthorities = this.authoritiesMapper
				.mapAuthorities(oidcUser.getAuthorities());
		OAuth2LoginAuthenticationToken authenticationResult = new OAuth2LoginAuthenticationToken(
				authorizationCodeAuthentication.getClientRegistration(),
				authorizationCodeAuthentication.getAuthorizationExchange(), oidcUser, mappedAuthorities,
				accessTokenResponse.getAccessToken(), accessTokenResponse.getRefreshToken());
		authenticationResult.setDetails(authorizationCodeAuthentication.getDetails());
		return authenticationResult;
	}

	private OAuth2AccessTokenResponse getResponse(OAuth2LoginAuthenticationToken authorizationCodeAuthentication) {
		try {
			return this.accessTokenResponseClient.getTokenResponse(
					new OAuth2AuthorizationCodeGrantRequest(authorizationCodeAuthentication.getClientRegistration(),
							authorizationCodeAuthentication.getAuthorizationExchange()));
		}
		catch (OAuth2AuthorizationException ex) {
			OAuth2Error oauth2Error = ex.getError();
			throw new OAuth2AuthenticationException(oauth2Error, oauth2Error.toString(), ex);
		}
	}

	private void validateNonce(OAuth2AuthorizationRequest authorizationRequest, OidcIdToken idToken) {
		String requestNonce = authorizationRequest.getAttribute(OidcParameterNames.NONCE);
		if (requestNonce == null) {
			return;
		}
		String nonceHash = getNonceHash(requestNonce);
		String nonceHashClaim = idToken.getNonce();
		if (nonceHashClaim == null || !nonceHashClaim.equals(nonceHash)) {
			OAuth2Error oauth2Error = new OAuth2Error(INVALID_NONCE_ERROR_CODE);
			throw new OAuth2AuthenticationException(oauth2Error, oauth2Error.toString());
		}
	}

	private String getNonceHash(String requestNonce) {
		try {
			return createHash(requestNonce);
		}
		catch (NoSuchAlgorithmException ex) {
			OAuth2Error oauth2Error = new OAuth2Error(INVALID_NONCE_ERROR_CODE);
			throw new OAuth2AuthenticationException(oauth2Error, oauth2Error.toString());
		}
	}

	/**
	 * Sets the {@link JwtDecoderFactory} used for {@link OidcIdToken} signature
	 * verification. The factory returns a {@link JwtDecoder} associated to the provided
	 * {@link ClientRegistration}.
	 * @param jwtDecoderFactory the {@link JwtDecoderFactory} used for {@link OidcIdToken}
	 * signature verification
	 * @since 5.2
	 */
	public final void setJwtDecoderFactory(JwtDecoderFactory<ClientRegistration> jwtDecoderFactory) {
		Assert.notNull(jwtDecoderFactory, "jwtDecoderFactory cannot be null");
		this.jwtDecoderFactory = jwtDecoderFactory;
	}

	/**
	 * Sets the {@link GrantedAuthoritiesMapper} used for mapping
	 * {@link OidcUser#getAuthorities()}} to a new set of authorities which will be
	 * associated to the {@link OAuth2LoginAuthenticationToken}.
	 * @param authoritiesMapper the {@link GrantedAuthoritiesMapper} used for mapping the
	 * user's authorities
	 */
	public final void setAuthoritiesMapper(GrantedAuthoritiesMapper authoritiesMapper) {
		Assert.notNull(authoritiesMapper, "authoritiesMapper cannot be null");
		this.authoritiesMapper = authoritiesMapper;
	}

	@Override
	public boolean supports(Class<?> authentication) {
		return OAuth2LoginAuthenticationToken.class.isAssignableFrom(authentication);
	}

	private OidcIdToken createOidcToken(ClientRegistration clientRegistration,
			OAuth2AccessTokenResponse accessTokenResponse) {
		JwtDecoder jwtDecoder = this.jwtDecoderFactory.createDecoder(clientRegistration);
		Jwt jwt = getJwt(accessTokenResponse, jwtDecoder);
		OidcIdToken idToken = new OidcIdToken(jwt.getTokenValue(), jwt.getIssuedAt(), jwt.getExpiresAt(),
				jwt.getClaims());
		return idToken;
	}

	private Jwt getJwt(OAuth2AccessTokenResponse accessTokenResponse, JwtDecoder jwtDecoder) {
		try {
			Map<String, Object> parameters = accessTokenResponse.getAdditionalParameters();
			return jwtDecoder.decode((String) parameters.get(OidcParameterNames.ID_TOKEN));
		}
		catch (JwtException ex) {
			OAuth2Error invalidIdTokenError = new OAuth2Error(INVALID_ID_TOKEN_ERROR_CODE, ex.getMessage(), null);
			throw new OAuth2AuthenticationException(invalidIdTokenError, invalidIdTokenError.toString(), ex);
		}
	}

	static String createHash(String nonce) throws NoSuchAlgorithmException {
		MessageDigest md = MessageDigest.getInstance("SHA-256");
		byte[] digest = md.digest(nonce.getBytes(StandardCharsets.US_ASCII));
		return Base64.getUrlEncoder().withoutPadding().encodeToString(digest);
	}

}
