Customizing OAuth 2.0 Scope Handling

/*
 * Copyright 2014-2022 ForgeRock AS. All Rights Reserved
 *
 * Use of this code requires a commercial software license with ForgeRock AS.
 * or with one of its affiliates. All use shall be exclusively subject
 * to such license between the licensee and ForgeRock AS.
 */

package org.forgerock.openam.examples;

import org.forgerock.oauth2.core.AccessToken;
import org.forgerock.oauth2.core.ClientRegistration;
import org.forgerock.oauth2.core.OAuth2Request;
import org.forgerock.oauth2.core.ScopeValidator;
import org.forgerock.oauth2.core.Token;
import org.forgerock.oauth2.core.UserInfoClaims;
import org.forgerock.oauth2.core.exceptions.InvalidClientException;
import org.forgerock.oauth2.core.exceptions.ServerException;
import org.forgerock.oauth2.core.exceptions.UnauthorizedClientException;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/**
 * Custom scope validators implement the
 * {@link org.forgerock.oauth2.core.ScopeValidator} interface.
 *
 * <p>
 * This example sets read and write permissions according to the scopes set.
 * </p>
 *
 * <ul>
 *
 * <li>
 * The {@code validateAuthorizationScope} method
 * adds default scopes, or any allowed scopes provided.
 * </li>
 *
 * <li>
 * The {@code validateAccessTokenScope} method
 * adds default scopes, or any allowed scopes provided.
 * </li>
 *
 * <li>
 * The {@code validateRefreshTokenScope} method
 * adds the scopes from the access token,
 * or any requested scopes provided that are also in the access token scopes.
 * </li>
 *
 * <li>
 * The {@code getUserInfo} method
 * populates scope values and sets the resource owner ID to return.
 * </li>
 *
 * <li>
 * The {@code evaluateScope} method
 * populates scope values to return.
 * </li>
 *
 * <li>
 * The {@code additionalDataToReturnFromAuthorizeEndpoint} method
 * returns no additional data (an empty Map).
 * </li>
 *
 * <li>
 * The {@code additionalDataToReturnFromTokenEndpoint} method
 * adds no additional data.
 * </li>
 *
 * </ul>
 */
public class CustomScopeValidator implements ScopeValidator {
    @Override
    public Set<String> validateAuthorizationScope(
            ClientRegistration clientRegistration,
            Set<String> scope,
            OAuth2Request oAuth2Request) {
        if (scope == null || scope.isEmpty()) {
            return clientRegistration.getDefaultScopes();
        }

        Set<String> scopes = new HashSet<String>(
                clientRegistration.getAllowedScopes());
        scopes.retainAll(scope);
        return scopes;
    }

    @Override
    public Set<String> validateAccessTokenScope(
            ClientRegistration clientRegistration,
            Set<String> scope,
            OAuth2Request request) {
        if (scope == null || scope.isEmpty()) {
            return clientRegistration.getDefaultScopes();
        }

        Set<String> scopes = new HashSet<String>(
                clientRegistration.getAllowedScopes());
        scopes.retainAll(scope);
        return scopes;
    }

    @Override
    public Set<String> validateRefreshTokenScope(
            ClientRegistration clientRegistration,
            Set<String> requestedScope,
            Set<String> tokenScope,
            OAuth2Request request) {
        if (requestedScope == null || requestedScope.isEmpty()) {
            return tokenScope;
        }

        Set<String> scopes = new HashSet<String>(tokenScope);
        scopes.retainAll(requestedScope);
        return scopes;
    }

    /**
     * Set read and write permissions according to scope.
     *
     * @param token The access token presented for validation.
     * @return The map of read and write permissions,
     *         with permissions set to {@code true} or {@code false},
     *         as appropriate.
     */
    private Map<String,Object> mapScopes(AccessToken token) {
        Set<String> scopes = token.getScope();
        Map<String, Object> map = new HashMap<String, Object>();
        final String[] permissions = {"read", "write"};

        for (String scope : permissions) {
            if (scopes.contains(scope)) {
                map.put(scope, true);
            } else {
                map.put(scope, false);
            }
        }
        return map;
    }

    @Override
    public UserInfoClaims getUserInfo(
            AccessToken token,
            OAuth2Request request)
            throws UnauthorizedClientException {
        Map<String, Object> response = mapScopes(token);
        response.put("sub", token.getResourceOwnerId());
        UserInfoClaims userInfoClaims = new UserInfoClaims(response, null);
        return userInfoClaims;
    }

    @Override
    public Map<String, Object> evaluateScope(AccessToken token) {
        return mapScopes(token);
    }

    @Override
    public Map<String, String> additionalDataToReturnFromAuthorizeEndpoint(
            Map<String, Token> tokens,
            OAuth2Request request) {
        return new HashMap<String, String>(); // No special handling
    }

    @Override
    public void additionalDataToReturnFromTokenEndpoint(
            AccessToken token,
            OAuth2Request request)
            throws ServerException, InvalidClientException {
        // No special handling
    }
}