Merge "Expose extension point for generic OAuth providers" into stable-2.10

Documentation/config-gerrit.txt

@@ -145,6 +145,16 @@ request is the exact string supplied in the dialog by the user.
 The configured <<ldap.username,ldap.username>> identity is not used to obtain
 account information.
 +
+* OAUTH
++
+OAuth is a protocol that lets external apps request authorization to private
+details in a user's account without getting their password. This is
+preferred over Basic Authentication because tokens can be limited to specific
+types of data, and can be revoked by users at any time.
++
+Site owners have to register their application before getting started. Note
+that provider specific plugins must be used with this authentication scheme.
++
 * `DEVELOPMENT_BECOME_ANY_ACCOUNT`
 +
 *DO NOT USE*.  Only for use in a development environment.

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/auth/oauth/OAuthServiceProvider.java

@@ -0,0 +1,74 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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
+//
+// http://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 com.google.gerrit.extensions.auth.oauth;
+
+import com.google.gerrit.extensions.annotations.ExtensionPoint;
+
+import java.io.IOException;
+
+/* Contract that OAuth provider must implement */
+@ExtensionPoint
+public interface OAuthServiceProvider {
+
+  /**
+   * Retrieve the request token.
+   *
+   * @return request token
+   */
+  OAuthToken getRequestToken();
+
+  /**
+   * Returns the URL where you should redirect your users to authenticate
+   * your application.
+   *
+   * @param requestToken the request token you need to authorize
+   * @return the URL where you should redirect your users
+   */
+  String getAuthorizationUrl(OAuthToken requestToken);
+
+  /**
+   * Retrieve the access token
+   *
+   * @param requestToken request token (obtained previously)
+   * @param verifier verifier code
+   * @return access token
+   */
+  OAuthToken getAccessToken(OAuthToken requestToken, OAuthVerifier verifier);
+
+  /**
+   * After establishing of secure communication channel, this method supossed to
+   * access the protected resoure and retrieve the username.
+   *
+   * @param token
+   * @return OAuth user information
+   * @throws IOException
+   */
+  OAuthUserInfo getUserInfo(OAuthToken token) throws IOException;
+
+  /**
+   * Returns the OAuth version of the service.
+   *
+   * @return oauth version as string
+   */
+  String getVersion();
+
+  /**
+   * Returns the name of this service. This name is resented the user to choose
+   * between multiple service providers
+   *
+   * @return name of the service
+   */
+  String getName();
+}

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/auth/oauth/OAuthToken.java

@@ -0,0 +1,41 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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
+//
+// http://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 com.google.gerrit.extensions.auth.oauth;
+
+/* OAuth token */
+public class OAuthToken {
+
+  private final String token;
+  private final String secret;
+  private final String raw;
+
+  public OAuthToken(String token, String secret, String raw) {
+    this.token = token;
+    this.secret = secret;
+    this.raw = raw;
+  }
+
+  public String getToken() {
+    return token;
+  }
+
+  public String getSecret() {
+    return secret;
+  }
+
+  public String getRaw() {
+    return raw;
+  }
+}

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/auth/oauth/OAuthUserInfo.java

@@ -0,0 +1,49 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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
+//
+// http://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 com.google.gerrit.extensions.auth.oauth;
+
+public class OAuthUserInfo {
+
+  private final String externalId;
+  private final String userName;
+  private final String emailAddress;
+  private final String displayName;
+
+  public OAuthUserInfo(String externalId,
+      String userName,
+      String emailAddress,
+      String displayName) {
+    this.externalId = externalId;
+    this.userName = userName;
+    this.emailAddress = emailAddress;
+    this.displayName = displayName;
+  }
+
+  public String getExternalId() {
+    return externalId;
+  }
+
+  public String getUserName() {
+    return userName;
+  }
+
+  public String getEmailAddress() {
+    return emailAddress;
+  }
+
+  public String getDisplayName() {
+    return displayName;
+  }
+}

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/auth/oauth/OAuthVerifier.java

@@ -0,0 +1,29 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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
+//
+// http://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 com.google.gerrit.extensions.auth.oauth;
+
+/* OAuth verifier */
+public class OAuthVerifier {
+
+  private final String value;
+
+  public OAuthVerifier(String value) {
+    this.value = value;
+  }
+
+  public String getValue() {
+    return value;
+  }
+}

gerrit-gwtui/src/main/java/com/google/gerrit/client/Gerrit.java

@@ -718,6 +718,15 @@ public class Gerrit implements EntryPoint {
           });
           break;
 
+        case OAUTH:
+          menuRight.addItem(C.menuSignIn(), new Command() {
+            @Override
+            public void execute() {
+              doSignIn(History.getToken());
+            }
+          });
+          break;
+
         case OPENID_SSO:
           menuRight.addItem(C.menuSignIn(), new Command() {
             public void execute() {

gerrit-httpd/src/main/java/com/google/gerrit/httpd/GerritConfigProvider.java

@@ -112,6 +112,7 @@ class GerritConfigProvider implements Provider<GerritConfig> {
 
       case CLIENT_SSL_CERT_LDAP:
       case DEVELOPMENT_BECOME_ANY_ACCOUNT:
+      case OAUTH:
       case OPENID:
       case OPENID_SSO:
         break;

gerrit-httpd/src/main/java/com/google/gerrit/httpd/HttpLogoutServlet.java

@@ -35,7 +35,7 @@ import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
 @Singleton
-class HttpLogoutServlet extends HttpServlet {
+public class HttpLogoutServlet extends HttpServlet {
   private static final long serialVersionUID = 1L;
 
   private final DynamicItem<WebSession> webSession;
@@ -44,7 +44,7 @@ class HttpLogoutServlet extends HttpServlet {
   private final AuditService audit;
 
   @Inject
-  HttpLogoutServlet(final AuthConfig authConfig,
+  protected HttpLogoutServlet(final AuthConfig authConfig,
       final DynamicItem<WebSession> webSession,
       @CanonicalWebUrl @Nullable final Provider<String> urlProvider,
       final AccountManager accountManager,
@@ -55,7 +55,7 @@ class HttpLogoutServlet extends HttpServlet {
     this.audit = audit;
   }
 
-  private void doLogout(final HttpServletRequest req,
+  protected void doLogout(final HttpServletRequest req,
       final HttpServletResponse rsp) throws IOException {
     webSession.get().logout();
     if (logoutUrl != null) {

gerrit-httpd/src/main/java/com/google/gerrit/httpd/UrlModule.java

@@ -33,8 +33,10 @@ import com.google.gerrit.httpd.rpc.config.ConfigRestApiServlet;
 import com.google.gerrit.httpd.rpc.doc.QueryDocumentationFilter;
 import com.google.gerrit.httpd.rpc.group.GroupsRestApiServlet;
 import com.google.gerrit.httpd.rpc.project.ProjectsRestApiServlet;
+import com.google.gerrit.reviewdb.client.AuthType;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.server.config.AuthConfig;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gwtexpui.server.CacheControlFilter;
 import com.google.inject.Inject;
@@ -64,10 +66,12 @@ class UrlModule extends ServletModule {
 
   private final UrlConfig cfg;
   private GerritUiOptions uiOptions;
+  private AuthConfig authConfig;
 
-  UrlModule(UrlConfig cfg, GerritUiOptions uiOptions) {
+  UrlModule(UrlConfig cfg, GerritUiOptions uiOptions, AuthConfig authConfig) {
     this.cfg = cfg;
     this.uiOptions = uiOptions;
+    this.authConfig = authConfig;
   }
 
   @Override
@@ -81,8 +85,11 @@ class UrlModule extends ServletModule {
       serve("/Gerrit/*").with(legacyGerritScreen());
     }
     serve("/cat/*").with(CatServlet.class);
-    serve("/logout").with(HttpLogoutServlet.class);
-    serve("/signout").with(HttpLogoutServlet.class);
+
+    if (authConfig.getAuthType() != AuthType.OAUTH) {
+      serve("/logout").with(HttpLogoutServlet.class);
+      serve("/signout").with(HttpLogoutServlet.class);
+    }
     serve("/ssh_info").with(SshInfoServlet.class);
     serve("/static/*").with(StaticServlet.class);
 

gerrit-httpd/src/main/java/com/google/gerrit/httpd/WebModule.java

@@ -101,6 +101,8 @@ public class WebModule extends LifecycleModule {
         install(new BecomeAnyAccountModule());
         break;
 
+      case OAUTH:
+        // OAuth support is bound in WebAppInitializer and Daemon.
       case OPENID:
       case OPENID_SSO:
         // OpenID support is bound in WebAppInitializer and Daemon.
@@ -110,7 +112,7 @@ public class WebModule extends LifecycleModule {
         throw new ProvisionException("Unsupported loginType: " + authConfig.getAuthType());
     }
 
-    install(new UrlModule(urlConfig, uiOptions));
+    install(new UrlModule(urlConfig, uiOptions, authConfig));
     install(new UiRpcModule());
     install(new GerritRequestModule());
     install(new GitOverHttpServlet.Module());

gerrit-oauth/BUCK

@@ -0,0 +1,24 @@
+SRCS = glob(
+  ['src/main/java/**/*.java'],
+)
+RESOURCES = glob(['src/main/resources/**/*'])
+
+java_library(
+  name = 'oauth',
+  srcs = SRCS,
+  resources = RESOURCES,
+  deps = [
+    '//gerrit-common:annotations',
+    '//gerrit-extension-api:api',
+    '//gerrit-httpd:httpd',
+    '//gerrit-server:server',
+    '//lib:gson',
+    '//lib:guava',
+    '//lib/commons:codec',
+    '//lib/guice:guice',
+    '//lib/guice:guice-servlet',
+    '//lib/log:api',
+  ],
+  provided_deps = ['//lib:servlet-api-3_1'],
+  visibility = ['PUBLIC'],
+)

gerrit-oauth/src/main/java/com/google/gerrit/httpd/auth/oauth/OAuthLogoutServlet.java

@@ -0,0 +1,57 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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
+//
+// http://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 com.google.gerrit.httpd.auth.oauth;
+
+import com.google.gerrit.audit.AuditService;
+import com.google.gerrit.common.Nullable;
+import com.google.gerrit.extensions.registration.DynamicItem;
+import com.google.gerrit.httpd.HttpLogoutServlet;
+import com.google.gerrit.httpd.WebSession;
+import com.google.gerrit.server.account.AccountManager;
+import com.google.gerrit.server.config.AuthConfig;
+import com.google.gerrit.server.config.CanonicalWebUrl;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+
+import java.io.IOException;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+@Singleton
+class OAuthLogoutServlet extends HttpLogoutServlet {
+  private static final long serialVersionUID = 1L;
+
+  private final Provider<OAuthSession> oauthSession;
+
+  @Inject
+  OAuthLogoutServlet(AuthConfig authConfig,
+      DynamicItem<WebSession> webSession,
+      @CanonicalWebUrl @Nullable Provider<String> urlProvider,
+      AccountManager accountManager,
+      AuditService audit,
+      Provider<OAuthSession> oauthSession) {
+      super(authConfig, webSession, urlProvider, accountManager, audit);
+    this.oauthSession = oauthSession;
+  }
+
+  @Override
+  protected void doLogout(HttpServletRequest req, HttpServletResponse rsp)
+      throws IOException {
+    super.doLogout(req, rsp);
+    oauthSession.get().logout();
+  }
+}

gerrit-oauth/src/main/java/com/google/gerrit/httpd/auth/oauth/OAuthModule.java

@@ -0,0 +1,31 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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
+//
+// http://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 com.google.gerrit.httpd.auth.oauth;
+
+import com.google.gerrit.extensions.auth.oauth.OAuthServiceProvider;
+import com.google.gerrit.extensions.registration.DynamicMap;
+import com.google.inject.servlet.ServletModule;
+
+/** Servlets and support related to OAuth authentication. */
+public class OAuthModule extends ServletModule {
+
+  @Override
+  protected void configureServlets() {
+    filter("/login", "/login/*", "/oauth").through(OAuthWebFilter.class);
+    // This is needed to invalidate OAuth session during logout
+    serve("/logout").with(OAuthLogoutServlet.class);
+    DynamicMap.mapOf(binder(), OAuthServiceProvider.class);
+  }
+}

gerrit-oauth/src/main/java/com/google/gerrit/httpd/auth/oauth/OAuthSession.java

@@ -0,0 +1,178 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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
+//
+// http://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 com.google.gerrit.httpd.auth.oauth;
+
+import static javax.servlet.http.HttpServletResponse.SC_UNAUTHORIZED;
+
+import com.google.common.base.Strings;
+import com.google.gerrit.extensions.auth.oauth.OAuthServiceProvider;
+import com.google.gerrit.extensions.auth.oauth.OAuthToken;
+import com.google.gerrit.extensions.auth.oauth.OAuthUserInfo;
+import com.google.gerrit.extensions.auth.oauth.OAuthVerifier;
+import com.google.gerrit.extensions.registration.DynamicItem;
+import com.google.gerrit.httpd.WebSession;
+import com.google.gerrit.server.account.AccountException;
+import com.google.gerrit.server.account.AccountManager;
+import com.google.gerrit.server.account.AuthResult;
+import com.google.inject.Inject;
+import com.google.inject.servlet.SessionScoped;
+
+import org.apache.commons.codec.binary.Base64;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.net.URLDecoder;
+import java.nio.charset.StandardCharsets;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+
+import javax.servlet.ServletRequest;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+@SessionScoped
+/* OAuth protocol implementation */
+class OAuthSession {
+  private static final Logger log = LoggerFactory.getLogger(OAuthSession.class);
+  private static final SecureRandom randomState = newRandomGenerator();
+  private final String state;
+  private final DynamicItem<WebSession> webSession;
+  private final AccountManager accountManager;
+  private OAuthServiceProvider serviceProvider;
+  private OAuthToken token;
+  private OAuthUserInfo user;
+  private String redirectUrl;
+
+  @Inject
+  OAuthSession(DynamicItem<WebSession> webSession,
+      AccountManager accountManager) {
+    this.state = generateRandomState();
+    this.webSession = webSession;
+    this.accountManager = accountManager;
+  }
+
+  boolean isLoggedIn() {
+    return token != null && user != null;
+  }
+
+  boolean isOAuthFinal(HttpServletRequest request) {
+    return Strings.emptyToNull(request.getParameter("code")) != null;
+  }
+
+  boolean login(HttpServletRequest request, HttpServletResponse response,
+      OAuthServiceProvider oauth) throws IOException {
+    if (isLoggedIn()) {
+      return true;
+    }
+
+    log.debug("Login " + this);
+
+    if (isOAuthFinal(request)) {
+      if (!checkState(request)) {
+        response.sendError(HttpServletResponse.SC_NOT_FOUND);
+        return false;
+      }
+
+      log.debug("Login-Retrieve-User " + this);
+      token = oauth.getAccessToken(null,
+          new OAuthVerifier(request.getParameter("code")));
+
+      user = oauth.getUserInfo(token);
+
+      if (isLoggedIn()) {
+        log.debug("Login-SUCCESS " + this);
+        authenticateAndRedirect(response);
+        return true;
+      } else {
+        response.sendError(SC_UNAUTHORIZED);
+        return false;
+      }
+    } else {
+      log.debug("Login-PHASE1 " + this);
+      redirectUrl = request.getRequestURI();
+      response.sendRedirect(oauth.getAuthorizationUrl(null) +
+          "&state=" + state);
+      return false;
+    }
+  }
+
+  private void authenticateAndRedirect(HttpServletResponse rsp)
+      throws IOException {
+    com.google.gerrit.server.account.AuthRequest areq =
+        new com.google.gerrit.server.account.AuthRequest(user.getExternalId());
+    areq.setUserName(user.getUserName());
+    areq.setEmailAddress(user.getEmailAddress());
+    areq.setDisplayName(user.getDisplayName());
+    AuthResult arsp;
+    try {
+      arsp = accountManager.authenticate(areq);
+    } catch (AccountException e) {
+      log.error("Unable to authenticate user \"" + user + "\"", e);
+      rsp.sendError(HttpServletResponse.SC_FORBIDDEN);
+      return;
+    }
+
+    webSession.get().login(arsp, true);
+    String suffix = redirectUrl.substring(
+        OAuthWebFilter.GERRIT_LOGIN.length() + 1);
+    suffix = URLDecoder.decode(suffix, StandardCharsets.UTF_8.name());
+    rsp.sendRedirect(suffix);
+  }
+
+  void logout() {
+    token = null;
+    user = null;
+    redirectUrl = null;
+    serviceProvider = null;
+  }
+
+  private boolean checkState(ServletRequest request) {
+    String s = Strings.nullToEmpty(request.getParameter("state"));
+    if (!s.equals(state)) {
+      log.error("Illegal request state '" + s + "' on OAuthProtocol " + this);
+      return false;
+    }
+    return true;
+  }
+
+  private static SecureRandom newRandomGenerator() {
+    try {
+      return SecureRandom.getInstance("SHA1PRNG");
+    } catch (NoSuchAlgorithmException e) {
+      throw new IllegalArgumentException(
+          "No SecureRandom available for GitHub authentication", e);
+    }
+  }
+
+  private static String generateRandomState() {
+    byte[] state = new byte[32];
+    randomState.nextBytes(state);
+    return Base64.encodeBase64URLSafeString(state);
+  }
+
+  @Override
+  public String toString() {
+    return "OAuthSession [token=" + token + ", user=" + user + "]";
+  }
+
+  public void setServiceProvider(OAuthServiceProvider provider) {
+    this.serviceProvider = provider;
+  }
+
+  public OAuthServiceProvider getServiceProvider() {
+    return serviceProvider;
+  }
+}

gerrit-oauth/src/main/java/com/google/gerrit/httpd/auth/oauth/OAuthWebFilter.java

@@ -0,0 +1,223 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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
+//
+// http://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 com.google.gerrit.httpd.auth.oauth;
+
+import com.google.common.base.Objects;
+import com.google.common.base.Strings;
+import com.google.common.collect.Iterables;
+import com.google.gerrit.common.Nullable;
+import com.google.gerrit.extensions.auth.oauth.OAuthServiceProvider;
+import com.google.gerrit.extensions.registration.DynamicMap;
+import com.google.gerrit.httpd.HtmlDomUtil;
+import com.google.gerrit.httpd.LoginUrlToken;
+import com.google.gerrit.httpd.template.SiteHeaderFooter;
+import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.config.CanonicalWebUrl;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.SortedSet;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.FilterConfig;
+import javax.servlet.ServletException;
+import javax.servlet.ServletOutputStream;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpSession;
+
+@Singleton
+/* OAuth web filter uses active OAuth session to perform OAuth requests */
+class OAuthWebFilter implements Filter {
+  static final String GERRIT_LOGIN = "/login";
+
+  private final Provider<String> urlProvider;
+  private final Provider<CurrentUser> currentUserProvider;
+  private final Provider<OAuthSession> oauthSessionProvider;
+  private final DynamicMap<OAuthServiceProvider> oauthServiceProviders;
+  private final SiteHeaderFooter header;
+  private OAuthServiceProvider ssoProvider;
+
+  @Inject
+  OAuthWebFilter(@CanonicalWebUrl @Nullable Provider<String> urlProvider,
+      Provider<CurrentUser> currentUserProvider,
+      DynamicMap<OAuthServiceProvider> oauthServiceProviders,
+      Provider<OAuthSession> oauthSessionProvider,
+      SiteHeaderFooter header) {
+    this.urlProvider = urlProvider;
+    this.currentUserProvider = currentUserProvider;
+    this.oauthServiceProviders = oauthServiceProviders;
+    this.oauthSessionProvider = oauthSessionProvider;
+    this.header = header;
+  }
+
+  @Override
+  public void init(FilterConfig filterConfig) throws ServletException {
+    pickSSOServiceProvider();
+  }
+
+  @Override
+  public void destroy() {
+  }
+
+  @Override
+  public void doFilter(ServletRequest request, ServletResponse response,
+      FilterChain chain) throws IOException, ServletException {
+    HttpServletRequest httpRequest = (HttpServletRequest) request;
+    HttpSession httpSession = ((HttpServletRequest) request).getSession(false);
+    if (currentUserProvider.get().isIdentifiedUser()) {
+      if (httpSession != null) {
+        httpSession.invalidate();
+      }
+      chain.doFilter(request, response);
+      return;
+    }
+
+    HttpServletResponse httpResponse = (HttpServletResponse) response;
+
+    String provider = httpRequest.getParameter("provider");
+    OAuthSession oauthSession = oauthSessionProvider.get();
+    OAuthServiceProvider service = ssoProvider == null
+        ? oauthSession.getServiceProvider()
+        : ssoProvider;
+
+    if ((isGerritLogin(httpRequest)
+        || oauthSession.isOAuthFinal(httpRequest))
+        && !oauthSession.isLoggedIn()) {
+      if (service == null && Strings.isNullOrEmpty(provider)) {
+        selectProvider(httpRequest, httpResponse, null);
+        return;
+      } else {
+        if (service == null) {
+          service = findService(provider);
+        }
+        oauthSession.setServiceProvider(service);
+        oauthSession.login(httpRequest, httpResponse, service);
+      }
+    } else {
+      chain.doFilter(httpRequest, response);
+    }
+  }
+
+  private OAuthServiceProvider findService(String providerId)
+      throws ServletException {
+    Set<String> plugins = oauthServiceProviders.plugins();
+    for (String pluginName : plugins) {
+      Map<String, Provider<OAuthServiceProvider>> m =
+          oauthServiceProviders.byPlugin(pluginName);
+        for (Map.Entry<String, Provider<OAuthServiceProvider>> e
+            : m.entrySet()) {
+          if (providerId.equals(
+              String.format("%s_%s", pluginName, e.getKey()))) {
+            return e.getValue().get();
+          }
+        }
+    }
+    throw new ServletException("No provider found for: " + providerId);
+  }
+
+  private void selectProvider(HttpServletRequest req, HttpServletResponse res,
+      @Nullable String errorMessage)
+      throws IOException {
+    String self = req.getRequestURI();
+    String cancel = Objects.firstNonNull(
+        urlProvider != null ? urlProvider.get() : "/", "/");
+    cancel += LoginUrlToken.getToken(req);
+
+    Document doc = header.parse(OAuthWebFilter.class, "LoginForm.html");
+    HtmlDomUtil.find(doc, "hostName").setTextContent(req.getServerName());
+    HtmlDomUtil.find(doc, "login_form").setAttribute("action", self);
+    HtmlDomUtil.find(doc, "cancel_link").setAttribute("href", cancel);
+
+    Element emsg = HtmlDomUtil.find(doc, "error_message");
+    if (Strings.isNullOrEmpty(errorMessage)) {
+      emsg.getParentNode().removeChild(emsg);
+    } else {
+      emsg.setTextContent(errorMessage);
+    }
+
+    Element providers = HtmlDomUtil.find(doc, "providers");
+
+    Set<String> plugins = oauthServiceProviders.plugins();
+    for (String pluginName : plugins) {
+      Map<String, Provider<OAuthServiceProvider>> m =
+          oauthServiceProviders.byPlugin(pluginName);
+        for (Map.Entry<String, Provider<OAuthServiceProvider>> e
+            : m.entrySet()) {
+          addProvider(providers, pluginName, e.getKey(),
+              e.getValue().get().getName());
+        }
+    }
+
+    sendHtml(res, doc);
+  }
+
+  private static void addProvider(Element form, String pluginName,
+      String id, String serviceName) {
+    Element div = form.getOwnerDocument().createElement("div");
+    div.setAttribute("id", id);
+    Element hyperlink = form.getOwnerDocument().createElement("a");
+    hyperlink.setAttribute("href", String.format("?provider=%s_%s",
+        pluginName, id));
+    hyperlink.setTextContent(serviceName +
+        " (" + pluginName + " plugin)");
+    div.appendChild(hyperlink);
+    form.appendChild(div);
+  }
+
+  private static void sendHtml(HttpServletResponse res, Document doc)
+      throws IOException {
+    byte[] bin = HtmlDomUtil.toUTF8(doc);
+    res.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
+    res.setContentType("text/html");
+    res.setCharacterEncoding(StandardCharsets.UTF_8.name());
+    res.setContentLength(bin.length);
+    try (ServletOutputStream out = res.getOutputStream()) {
+      out.write(bin);
+    }
+  }
+
+  private void pickSSOServiceProvider()
+      throws ServletException {
+    SortedSet<String> plugins = oauthServiceProviders.plugins();
+    if (plugins.isEmpty()) {
+      throw new ServletException(
+          "OAuth service provider wasn't installed");
+    }
+    if (plugins.size() == 1) {
+      SortedMap<String, Provider<OAuthServiceProvider>> services =
+          oauthServiceProviders.byPlugin(Iterables.getOnlyElement(plugins));
+      if (services.size() == 1) {
+        ssoProvider = Iterables.getOnlyElement(services.values()).get();
+      }
+    }
+  }
+
+  private static boolean isGerritLogin(HttpServletRequest request) {
+    return request.getRequestURI().indexOf(GERRIT_LOGIN) >= 0;
+  }
+}

gerrit-pgm/BUCK

@@ -99,6 +99,7 @@ java_library(
     '//gerrit-gwtexpui:server',
     '//gerrit-httpd:httpd',
     '//gerrit-lucene:lucene',
+    '//gerrit-oauth:oauth',
     '//gerrit-openid:openid',
     '//gerrit-reviewdb:server',
     '//gerrit-server:server',

gerrit-pgm/src/main/java/com/google/gerrit/pgm/Daemon.java

@@ -27,6 +27,7 @@ import com.google.gerrit.httpd.HttpCanonicalWebUrlProvider;
 import com.google.gerrit.httpd.RequestContextFilter;
 import com.google.gerrit.httpd.WebModule;
 import com.google.gerrit.httpd.WebSshGlueModule;
+import com.google.gerrit.httpd.auth.oauth.OAuthModule;
 import com.google.gerrit.httpd.auth.openid.OpenIdModule;
 import com.google.gerrit.httpd.plugins.HttpPluginModule;
 import com.google.gerrit.lifecycle.LifecycleManager;
@@ -430,6 +431,8 @@ public class Daemon extends SiteProgram {
     if (authConfig.getAuthType() == AuthType.OPENID ||
         authConfig.getAuthType() == AuthType.OPENID_SSO) {
       modules.add(new OpenIdModule());
+    } else if (authConfig.getAuthType() == AuthType.OAUTH) {
+      modules.add(new OAuthModule());
     }
     modules.add(sysInjector.getInstance(GetUserFilter.Module.class));
 

gerrit-pgm/src/main/java/com/google/gerrit/pgm/init/InitAuth.java

@@ -60,6 +60,7 @@ class InitAuth implements InitStep {
       case DEVELOPMENT_BECOME_ANY_ACCOUNT:
       case LDAP:
       case LDAP_BIND:
+      case OAUTH:
       case OPENID:
       case OPENID_SSO:
         break;
@@ -94,6 +95,7 @@ class InitAuth implements InitStep {
       case CUSTOM_EXTENSION:
       case DEVELOPMENT_BECOME_ANY_ACCOUNT:
       case HTTP:
+      case OAUTH:
       case OPENID:
       case OPENID_SSO:
         break;

gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AuthType.java

@@ -80,5 +80,8 @@ public enum AuthType {
   CUSTOM_EXTENSION,
 
   /** Development mode to enable becoming anyone you want. */
-  DEVELOPMENT_BECOME_ANY_ACCOUNT
+  DEVELOPMENT_BECOME_ANY_ACCOUNT,
+
+  /** Generic OAuth provider over HTTP. */
+  OAUTH
 }

gerrit-server/src/main/java/com/google/gerrit/server/account/DefaultRealm.java

@@ -40,7 +40,8 @@ public class DefaultRealm implements Realm {
 
   @Override
   public boolean allowsEdit(final Account.FieldName field) {
-    if (authConfig.getAuthType() == AuthType.HTTP) {
+    if (authConfig.getAuthType() == AuthType.HTTP
+        || authConfig.getAuthType() == AuthType.OAUTH) {
       switch (field) {
         case USER_NAME:
           return false;

gerrit-server/src/main/java/com/google/gerrit/server/config/AuthConfig.java

@@ -197,7 +197,7 @@ public class AuthConfig {
       case LDAP_BIND:
       case CLIENT_SSL_CERT_LDAP:
       case CUSTOM_EXTENSION:
-        // Its safe to assume yes for an HTTP authentication type, as the
+      case OAUTH:
         // only way in is through some external system that the admin trusts
         //
         return true;

gerrit-war/BUCK

@@ -8,6 +8,7 @@ java_library(
     '//gerrit-extension-api:api',
     '//gerrit-httpd:httpd',
     '//gerrit-lucene:lucene',
+    '//gerrit-oauth:oauth',
     '//gerrit-openid:openid',
     '//gerrit-pgm:init-api',
     '//gerrit-pgm:init-base',

gerrit-war/src/main/java/com/google/gerrit/httpd/WebAppInitializer.java

@@ -19,6 +19,7 @@ import static com.google.inject.Stage.PRODUCTION;
 
 import com.google.common.base.Splitter;
 import com.google.gerrit.common.ChangeHookRunner;
+import com.google.gerrit.httpd.auth.oauth.OAuthModule;
 import com.google.gerrit.httpd.auth.openid.OpenIdModule;
 import com.google.gerrit.httpd.plugins.HttpPluginModule;
 import com.google.gerrit.lifecycle.LifecycleManager;
@@ -343,6 +344,8 @@ public class WebAppInitializer extends GuiceServletContextListener
     AuthConfig authConfig = cfgInjector.getInstance(AuthConfig.class);
     if (authConfig.getAuthType() == AuthType.OPENID) {
       modules.add(new OpenIdModule());
+    } else if (authConfig.getAuthType() == AuthType.OAUTH) {
+      modules.add(new OAuthModule());
     }
 
     return sysInjector.createChildInjector(modules);