Add support for Phabricator OAuth provider

Phabricator instances implement an OAuth 2.0 server, as documented in
https://secure.phabricator.com/book/phabcontrib/article/using_oauthserver/.

Change-Id: Id0cab0593c5c83937c895ad4cdfab5b5c23885a6
diff --git a/README.md b/README.md
index dae7dcb..de036fb 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@
 * [Keycloak](http://www.keycloak.org/)
 * [LemonLDAP::NG](https://lemonldap-ng.org)
 * [Office365](https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-v2-protocols)
+* [Phabricator](https://secure.phabricator.com/book/phabcontrib/article/using_oauthserver/)
 
 See the [Wiki](https://github.com/davido/gerrit-oauth-provider/wiki) what it can do for you.
 
diff --git a/src/main/java/com/googlesource/gerrit/plugins/oauth/HttpModule.java b/src/main/java/com/googlesource/gerrit/plugins/oauth/HttpModule.java
index c28f932..80bc605 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/oauth/HttpModule.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/oauth/HttpModule.java
@@ -112,5 +112,12 @@
           .annotatedWith(Exports.named(AirVantageOAuthService.CONFIG_SUFFIX))
           .to(AirVantageOAuthService.class);
     }
+
+    cfg = cfgFactory.getFromGerritConfig(pluginName + PhabricatorOAuthService.CONFIG_SUFFIX);
+    if (cfg.getString(InitOAuth.CLIENT_ID) != null) {
+      bind(OAuthServiceProvider.class)
+          .annotatedWith(Exports.named(PhabricatorOAuthService.CONFIG_SUFFIX))
+          .to(PhabricatorOAuthService.class);
+    }
   }
 }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/oauth/InitOAuth.java b/src/main/java/com/googlesource/gerrit/plugins/oauth/InitOAuth.java
index 8c874e6..854ba5b 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/oauth/InitOAuth.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/oauth/InitOAuth.java
@@ -49,6 +49,7 @@
   private final Section keycloakOAuthProviderSection;
   private final Section office365OAuthProviderSection;
   private final Section airVantageOAuthProviderSection;
+  private final Section phabricatorOAuthProviderSection;
 
   @Inject
   InitOAuth(ConsoleUI ui, Section.Factory sections, @PluginName String pluginName) {
@@ -75,6 +76,8 @@
         sections.get(PLUGIN_SECTION, pluginName + Office365OAuthService.CONFIG_SUFFIX);
     this.airVantageOAuthProviderSection =
         sections.get(PLUGIN_SECTION, pluginName + AirVantageOAuthService.CONFIG_SUFFIX);
+    this.phabricatorOAuthProviderSection =
+        sections.get(PLUGIN_SECTION, pluginName + PhabricatorOAuthService.CONFIG_SUFFIX);
   }
 
   @Override
@@ -170,6 +173,14 @@
     if (configureAirVantageOAuthProvider) {
       configureOAuth(airVantageOAuthProviderSection);
     }
+
+    boolean configurePhabricatorOAuthProvider =
+        ui.yesno(
+            isConfigured(phabricatorOAuthProviderSection),
+            "Use Phabricator OAuth provider for Gerrit login ?");
+    if (configurePhabricatorOAuthProvider && configureOAuth(phabricatorOAuthProviderSection)) {
+      checkRootUrl(phabricatorOAuthProviderSection.string("Phabricator Root URL", ROOT_URL, null));
+    }
   }
 
   /**
diff --git a/src/main/java/com/googlesource/gerrit/plugins/oauth/PhabricatorApi.java b/src/main/java/com/googlesource/gerrit/plugins/oauth/PhabricatorApi.java
new file mode 100644
index 0000000..a2a52ff
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/oauth/PhabricatorApi.java
@@ -0,0 +1,44 @@
+// Copyright (C) 2020 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.googlesource.gerrit.plugins.oauth;
+
+import com.github.scribejava.core.builder.api.DefaultApi20;
+import com.github.scribejava.core.oauth2.bearersignature.BearerSignature;
+import com.github.scribejava.core.oauth2.bearersignature.BearerSignatureURIQueryParameter;
+
+public class PhabricatorApi extends DefaultApi20 {
+  private static final String AUTHORIZE_URL = "%s/oauthserver/auth/";
+
+  private final String rootUrl;
+
+  public PhabricatorApi(String rootUrl) {
+    this.rootUrl = rootUrl;
+  }
+
+  @Override
+  public String getAuthorizationBaseUrl() {
+    return String.format(AUTHORIZE_URL, rootUrl);
+  }
+
+  @Override
+  public String getAccessTokenEndpoint() {
+    return String.format("%s/oauthserver/token/", rootUrl);
+  }
+
+  @Override
+  public BearerSignature getBearerSignature() {
+    return BearerSignatureURIQueryParameter.instance();
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/oauth/PhabricatorOAuthService.java b/src/main/java/com/googlesource/gerrit/plugins/oauth/PhabricatorOAuthService.java
new file mode 100644
index 0000000..18086ec
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/oauth/PhabricatorOAuthService.java
@@ -0,0 +1,156 @@
+// Copyright (C) 2020 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.googlesource.gerrit.plugins.oauth;
+
+import static com.google.gerrit.json.OutputFormat.JSON;
+
+import com.github.scribejava.core.builder.ServiceBuilder;
+import com.github.scribejava.core.model.OAuth2AccessToken;
+import com.github.scribejava.core.model.OAuthRequest;
+import com.github.scribejava.core.model.Response;
+import com.github.scribejava.core.model.Verb;
+import com.github.scribejava.core.oauth.OAuth20Service;
+import com.google.common.base.CharMatcher;
+import com.google.gerrit.extensions.annotations.PluginName;
+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.server.config.CanonicalWebUrl;
+import com.google.gerrit.server.config.PluginConfig;
+import com.google.gerrit.server.config.PluginConfigFactory;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.ProvisionException;
+import com.google.inject.Singleton;
+import java.io.IOException;
+import java.net.URI;
+import java.util.concurrent.ExecutionException;
+import javax.servlet.http.HttpServletResponse;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+@Singleton
+class PhabricatorOAuthService implements OAuthServiceProvider {
+  private static final Logger log = LoggerFactory.getLogger(PhabricatorOAuthService.class);
+  static final String CONFIG_SUFFIX = "-phabricator-oauth";
+  private static final String PHABRICATOR_PROVIDER_PREFIX = "phabricator-oauth:";
+  private static final String PROTECTED_RESOURCE_URL = "%s/api/user.whoami";
+  private final String rootUrl;
+  private final OAuth20Service service;
+
+  @Inject
+  PhabricatorOAuthService(
+      PluginConfigFactory cfgFactory,
+      @PluginName String pluginName,
+      @CanonicalWebUrl Provider<String> urlProvider) {
+    PluginConfig cfg = cfgFactory.getFromGerritConfig(pluginName + CONFIG_SUFFIX);
+    String canonicalWebUrl = CharMatcher.is('/').trimTrailingFrom(urlProvider.get()) + "/";
+    rootUrl = cfg.getString(InitOAuth.ROOT_URL);
+    if (!URI.create(rootUrl).isAbsolute()) {
+      throw new ProvisionException("Root URL must be absolute URL");
+    }
+    this.service =
+        new ServiceBuilder(cfg.getString(InitOAuth.CLIENT_ID))
+            .apiSecret(cfg.getString(InitOAuth.CLIENT_SECRET))
+            .callback(canonicalWebUrl + "oauth")
+            .build(new PhabricatorApi(rootUrl));
+    if (log.isDebugEnabled()) {
+      log.debug("OAuth2: canonicalWebUrl={}", canonicalWebUrl);
+    }
+  }
+
+  @Override
+  public OAuthUserInfo getUserInfo(OAuthToken token) throws IOException {
+    OAuthRequest request =
+        new OAuthRequest(Verb.GET, String.format(PROTECTED_RESOURCE_URL, rootUrl));
+    OAuth2AccessToken t = new OAuth2AccessToken(token.getToken(), token.getRaw());
+    service.signRequest(t, request);
+
+    JsonElement userJson = null;
+    try (Response response = service.execute(request)) {
+      if (response.getCode() != HttpServletResponse.SC_OK) {
+        throw new IOException(
+            String.format(
+                "Status %s (%s) for request %s",
+                response.getCode(), response.getBody(), request.getUrl()));
+      }
+      userJson = JSON.newGson().fromJson(response.getBody(), JsonElement.class);
+      if (log.isDebugEnabled()) {
+        log.debug("User info response: {}", response.getBody());
+      }
+      if (userJson.isJsonObject()) {
+        JsonObject jsonObject = userJson.getAsJsonObject();
+        JsonElement jsonResult = jsonObject.get("result");
+        if (jsonResult == null) {
+          throw new IOException("Response doesn't contain result field");
+        }
+        JsonObject resultObject = jsonResult.getAsJsonObject();
+        JsonElement id = resultObject.get("phid");
+        if (id == null || id.isJsonNull()) {
+          throw new IOException("Response doesn't contain id field");
+        }
+        JsonElement email = resultObject.get("primaryEmail");
+        JsonElement name = resultObject.get("realName");
+        JsonElement username = resultObject.get("userName");
+        String login = null;
+
+        if (!username.isJsonNull()) {
+          login = username.getAsString();
+        }
+        return new OAuthUserInfo(
+            PHABRICATOR_PROVIDER_PREFIX + id.getAsString() /*externalId*/,
+            login /*username*/,
+            email == null || email.isJsonNull() ? null : email.getAsString() /*email*/,
+            name == null || name.isJsonNull() ? null : name.getAsString() /*displayName*/,
+            null);
+      }
+    } catch (ExecutionException | InterruptedException e) {
+      throw new RuntimeException("Cannot retrieve user info resource", e);
+    }
+
+    throw new IOException(String.format("Invalid JSON '%s': not a JSON Object", userJson));
+  }
+
+  @Override
+  public OAuthToken getAccessToken(OAuthVerifier rv) {
+    try {
+      OAuth2AccessToken accessToken = service.getAccessToken(rv.getValue());
+      return new OAuthToken(
+          accessToken.getAccessToken(), accessToken.getTokenType(), accessToken.getRawResponse());
+    } catch (InterruptedException | ExecutionException | IOException e) {
+      String msg = "Cannot retrieve access token";
+      log.error(msg, e);
+      throw new RuntimeException(msg, e);
+    }
+  }
+
+  @Override
+  public String getAuthorizationUrl() {
+    return service.getAuthorizationUrl();
+  }
+
+  @Override
+  public String getVersion() {
+    return service.getVersion();
+  }
+
+  @Override
+  public String getName() {
+    return "Phabricator OAuth2";
+  }
+}
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index a97fd16..19eb426 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -43,6 +43,11 @@
   [plugin "@PLUGIN@-airvantage-oauth"]
     client-id = "<client-id>"
     client-secret = "<client-secret>"
+
+  [plugin "@PLUGIN@-phabricator-oauth"]
+    client-id = "<client-id>"
+    client-secret = "<client-secret>"
+    root-url = "<phabricator url>"
 ```
 
 When one from the sections above is omitted, OAuth SSO is used.
@@ -211,3 +216,9 @@
 The client-id and client-secret for AirVantage OAuth can be obtained by registering
 a Client application.
 See [Getting Started](https://source.sierrawireless.com/airvantage/av/howto/cloud/gettingstarted_api).
+
+### Phabricator
+
+The client-id and client-secret for Phabricator can be obtained by registering a
+Client application.
+See [Using the Phabricator OAuth Server](https://secure.phabricator.com/book/phabcontrib/article/using_oauthserver/).
diff --git a/src/test/java/com/googlesource/gerrit/plugins/oauth/PhabricatorApiTest.java b/src/test/java/com/googlesource/gerrit/plugins/oauth/PhabricatorApiTest.java
new file mode 100644
index 0000000..9a9646c
--- /dev/null
+++ b/src/test/java/com/googlesource/gerrit/plugins/oauth/PhabricatorApiTest.java
@@ -0,0 +1,35 @@
+// Copyright (C) 2020 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.googlesource.gerrit.plugins.oauth;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.github.scribejava.core.extractors.OAuth2AccessTokenJsonExtractor;
+import org.junit.Before;
+import org.junit.Test;
+
+public class PhabricatorApiTest {
+  private PhabricatorApi api;
+
+  @Before
+  public void setUp() {
+    api = new PhabricatorApi("");
+  }
+
+  @Test
+  public void testAccessTokenExtractor() {
+    assertThat(api.getAccessTokenExtractor()).isInstanceOf(OAuth2AccessTokenJsonExtractor.class);
+  }
+}