diff --git a/.buckconfig b/.buckconfig
new file mode 100644
index 0000000..561d6eb
--- /dev/null
+++ b/.buckconfig
@@ -0,0 +1,13 @@
+[alias]
+  cfoauth = //:cfoauth
+  plugin = //:cfoauth
+
+[java]
+  src_roots = java, resources
+
+[project]
+  ignore = .git
+
+[cache]
+  mode = dir
+  dir = buck-out/cache
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b4277e3
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,10 @@
+/.buckversion
+/.buckd
+/.watchmanconfig
+/buck-out
+/bucklets
+/target
+/.classpath
+/.project
+/.settings/org.maven.ide.eclipse.prefs
+/.settings/org.eclipse.m2e.core.prefs
diff --git a/BUCK b/BUCK
new file mode 100644
index 0000000..f20aa8a
--- /dev/null
+++ b/BUCK
@@ -0,0 +1,54 @@
+include_defs('//bucklets/gerrit_plugin.bucklet')
+include_defs('//bucklets/maven_jar.bucklet')
+define_license('scribe')
+
+gerrit_plugin(
+  name = 'cfoauth',
+  srcs = glob(['src/main/java/**/*.java']),
+  resources = glob(['src/main/**/*']),
+  manifest_entries = [
+    'Gerrit-PluginName: cfoauth',
+    'Gerrit-ApiType: plugin',
+    'Gerrit-ApiVersion: 2.12-SNAPSHOT',
+    'Gerrit-HttpModule: com.googlesource.gerrit.plugins.cfoauth.HttpModule',
+    'Gerrit-InitStep: com.googlesource.gerrit.plugins.cfoauth.InitOAuthConfig',
+    'Implementation-Title: Cloud Foundry UAA OAuth 2.0 Authentication Provider',
+    'Implementation-URL: https://gerrit-review.googlesource.com/#/admin/projects/plugins/cfoauth',
+  ],
+  deps = [
+    ':scribe'
+  ],
+  provided_deps = [
+    '//lib:guava',
+    '//lib:gson',
+    '//lib/commons:codec'
+  ],
+)
+
+# this is required for bucklets/tools/eclipse/project.py to work
+java_library(
+  name = 'classpath',
+  deps = [':cfoauth__plugin'],
+)
+
+java_test(
+  name = 'cfoauth_tests',
+  srcs = glob(['src/test/java/**/*.java']),
+  labels = ['cfoauth'],
+  deps = [
+    ':cfoauth__plugin',
+    ':scribe',
+    '//lib:junit',
+    '//lib:guava',
+    '//lib:gson',
+    '//lib/commons:codec'
+  ],
+)
+
+maven_jar(
+  name = 'scribe',
+  id = 'org.scribe:scribe:1.3.7',
+  sha1 = '583921bed46635d9f529ef5f14f7c9e83367bc6e',
+  license = 'scribe',
+  local_license = True,
+)
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..11069ed
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
+
+   "Licensor" shall mean the copyright owner or entity authorized by
+   the copyright owner that is granting the License.
+
+   "Legal Entity" shall mean the union of the acting entity and all
+   other entities that control, are controlled by, or are under common
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+   direction or management of such entity, whether by contract or
+   otherwise, or (ii) ownership of fifty percent (50%) or more of the
+   outstanding shares, or (iii) beneficial ownership of such entity.
+
+   "You" (or "Your") shall mean an individual or Legal Entity
+   exercising permissions granted by this License.
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+   "Source" form shall mean the preferred form for making modifications,
+   including but not limited to software source code, documentation
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+
+   "Object" form shall mean any form resulting from mechanical
+   transformation or translation of a Source form, including but
+   not limited to compiled object code, generated documentation,
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+
+   "Work" shall mean the work of authorship, whether in Source or
+   Object form, made available under the License, as indicated by a
+   copyright notice that is included in or attached to the work
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+
+   "Derivative Works" shall mean any work, whether in Source or Object
+   form, that is based on (or derived from) the Work and for which the
+   editorial revisions, annotations, elaborations, or other modifications
+   represent, as a whole, an original work of authorship. For the purposes
+   of this License, Derivative Works shall not include works that remain
+   separable from, or merely link (or bind by name) to the interfaces of,
+   the Work and Derivative Works thereof.
+
+   "Contribution" shall mean any work of authorship, including
+   the original version of the Work and any modifications or additions
+   to that Work or Derivative Works thereof, that is intentionally
+   submitted to Licensor for inclusion in the Work by the copyright owner
+   or by an individual or Legal Entity authorized to submit on behalf of
+   the copyright owner. For the purposes of this definition, "submitted"
+   means any form of electronic, verbal, or written communication sent
+   to the Licensor or its representatives, including but not limited to
+   communication on electronic mailing lists, source code control systems,
+   and issue tracking systems that are managed by, or on behalf of, the
+   Licensor for the purpose of discussing and improving the Work, but
+   excluding communication that is conspicuously marked or otherwise
+   designated in writing by the copyright owner as "Not a Contribution."
+
+   "Contributor" shall mean Licensor and any individual or Legal Entity
+   on behalf of whom a Contribution has been received by Licensor and
+   subsequently incorporated within the Work.
+
+2. Grant of Copyright License. Subject to the terms and conditions of
+   this License, each Contributor hereby grants to You a perpetual,
+   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+   copyright license to reproduce, prepare Derivative Works of,
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+   Work and such Derivative Works in Source or Object form.
+
+3. Grant of Patent License. Subject to the terms and conditions of
+   this License, each Contributor hereby grants to You a perpetual,
+   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+   (except as stated in this section) patent license to make, have made,
+   use, offer to sell, sell, import, and otherwise transfer the Work,
+   where such license applies only to those patent claims licensable
+   by such Contributor that are necessarily infringed by their
+   Contribution(s) alone or by combination of their Contribution(s)
+   with the Work to which such Contribution(s) was submitted. If You
+   institute patent litigation against any entity (including a
+   cross-claim or counterclaim in a lawsuit) alleging that the Work
+   or a Contribution incorporated within the Work constitutes direct
+   or contributory patent infringement, then any patent licenses
+   granted to You under this License for that Work shall terminate
+   as of the date such litigation is filed.
+
+4. Redistribution. You may reproduce and distribute copies of the
+   Work or Derivative Works thereof in any medium, with or without
+   modifications, and in Source or Object form, provided that You
+   meet the following conditions:
+
+   (a) You must give any other recipients of the Work or
+       Derivative Works a copy of this License; and
+
+   (b) You must cause any modified files to carry prominent notices
+       stating that You changed the files; and
+
+   (c) You must retain, in the Source form of any Derivative Works
+       that You distribute, all copyright, patent, trademark, and
+       attribution notices from the Source form of the Work,
+       excluding those notices that do not pertain to any part of
+       the Derivative Works; and
+
+   (d) If the Work includes a "NOTICE" text file as part of its
+       distribution, then any Derivative Works that You distribute must
+       include a readable copy of the attribution notices contained
+       within such NOTICE file, excluding those notices that do not
+       pertain to any part of the Derivative Works, in at least one
+       of the following places: within a NOTICE text file distributed
+       as part of the Derivative Works; within the Source form or
+       documentation, if provided along with the Derivative Works; or,
+       within a display generated by the Derivative Works, if and
+       wherever such third-party notices normally appear. The contents
+       of the NOTICE file are for informational purposes only and
+       do not modify the License. You may add Your own attribution
+       notices within Derivative Works that You distribute, alongside
+       or as an addendum to the NOTICE text from the Work, provided
+       that such additional attribution notices cannot be construed
+       as modifying the License.
+
+   You may add Your own copyright statement to Your modifications and
+   may provide additional or different license terms and conditions
+   for use, reproduction, or distribution of Your modifications, or
+   for any such Derivative Works as a whole, provided Your use,
+   reproduction, and distribution of the Work otherwise complies with
+   the conditions stated in this License.
+
+5. Submission of Contributions. Unless You explicitly state otherwise,
+   any Contribution intentionally submitted for inclusion in the Work
+   by You to the Licensor shall be under the terms and conditions of
+   this License, without any additional terms or conditions.
+   Notwithstanding the above, nothing herein shall supersede or modify
+   the terms of any separate license agreement you may have executed
+   with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade
+   names, trademarks, service marks, or product names of the Licensor,
+   except as required for reasonable and customary use in describing the
+   origin of the Work and reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty. Unless required by applicable law or
+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+   implied, including, without limitation, any warranties or conditions
+   of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+   PARTICULAR PURPOSE. You are solely responsible for determining the
+   appropriateness of using or redistributing the Work and assume any
+   risks associated with Your exercise of permissions under this License.
+
+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
+   incidental, or consequential damages of any character arising as a
+   result of this License or out of the use or inability to use the
+   Work (including but not limited to damages for loss of goodwill,
+   work stoppage, computer failure or malfunction, or any and all
+   other commercial damages or losses), even if such Contributor
+   has been advised of the possibility of such damages.
+
+9. Accepting Warranty or Additional Liability. While redistributing
+   the Work or Derivative Works thereof, You may choose to offer,
+   and charge a fee for, acceptance of support, warranty, indemnity,
+   or other liability obligations and/or rights consistent with this
+   License. However, in accepting such obligations, You may act only
+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
+   defend, and hold each Contributor harmless for any liability
+   incurred by, or claims asserted against, such Contributor by reason
+   of your accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
+   To apply the Apache License to your work, attach the following
+   boilerplate notice, with the fields enclosed by brackets "[]"
+   replaced with your own identifying information. (Don't include
+   the brackets!)  The text should be enclosed in the appropriate
+   comment syntax for the file format. We also recommend that a
+   file or class name and description of purpose be included on the
+   same "printed page" as the copyright notice for easier
+   identification within third-party archives.
+
+Copyright [yyyy] [name of copyright owner]
+
+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.
diff --git a/LICENSE-scribe b/LICENSE-scribe
new file mode 100644
index 0000000..7cea02d
--- /dev/null
+++ b/LICENSE-scribe
@@ -0,0 +1,22 @@
+The MIT License
+
+Copyright (c) 2010 Pablo Fernandez
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..dd37c20
--- /dev/null
+++ b/README.md
@@ -0,0 +1,15 @@
+Cloud Foundry UAA OAuth 2.0 Authentication Provider
+===================================================
+
+With this plugin Gerrit can use OAuth2 protocol to authenticate users
+accessing Gerrit's Web UI with a
+[CloudFoundry User Account and Authentication (UAA)](https://github.com/cloudfoundry/uaa)
+server. The `Sign In` link will redirect the user to the UAA login screen.
+
+For Git-over-HTTP communication users still need to generate and use
+an HTTP password.
+
+License
+-------
+
+Apache License 2.0
diff --git a/VERSION b/VERSION
new file mode 100644
index 0000000..cfb4e97
--- /dev/null
+++ b/VERSION
@@ -0,0 +1,4 @@
+# Used by BUCK to include "Implementation-Version" in plugin Manifest.
+# If this file doesn't exist the output of 'git describe' is used
+# instead.
+PLUGIN_VERSION = '2.12-SNAPSHOT'
diff --git a/lib/BUCK b/lib/BUCK
new file mode 100644
index 0000000..ab803a7
--- /dev/null
+++ b/lib/BUCK
@@ -0,0 +1,15 @@
+include_defs('//bucklets/maven_jar.bucklet')
+
+maven_jar(
+  name = 'gson',
+  id = 'com.google.code.gson:gson:2.3.1',
+  sha1 = 'ecb6e1f8e4b0e84c4b886c2f14a1500caf309757',
+  license = 'Apache2.0',
+)
+
+maven_jar(
+  name = 'guava',
+  id = 'com.google.guava:guava:18.0',
+  sha1 = 'cce0823396aa693798f8882e64213b1772032b09',
+  license = 'Apache2.0',
+)
diff --git a/lib/commons/BUCK b/lib/commons/BUCK
new file mode 100644
index 0000000..7aafa82
--- /dev/null
+++ b/lib/commons/BUCK
@@ -0,0 +1,9 @@
+include_defs('//bucklets/maven_jar.bucklet')
+
+maven_jar(
+  name = 'codec',
+  id = 'commons-codec:commons-codec:1.4',
+  sha1 = '4216af16d38465bbab0f3dff8efa14204f7a399a',
+  license = 'Apache2.0',
+  exclude = ['META-INF/LICENSE.txt', 'META-INF/NOTICE.txt'],
+)
diff --git a/lib/gerrit/BUCK b/lib/gerrit/BUCK
new file mode 100644
index 0000000..85b90a8
--- /dev/null
+++ b/lib/gerrit/BUCK
@@ -0,0 +1,12 @@
+include_defs('//bucklets/maven_jar.bucklet')
+
+VER = '2.12-SNAPSHOT'
+REPO = MAVEN_LOCAL
+
+maven_jar(
+  name = 'plugin-api',
+  id = 'com.google.gerrit:gerrit-plugin-api:' + VER,
+  license = 'Apache2.0',
+  attach_source = False,
+  repository = REPO,
+)
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/AccessToken.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/AccessToken.java
new file mode 100644
index 0000000..3e9e4f3
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/AccessToken.java
@@ -0,0 +1,124 @@
+// 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.googlesource.gerrit.plugins.cfoauth;
+
+import com.google.gerrit.reviewdb.client.AccountExternalId;
+
+import java.util.Objects;
+
+class AccessToken {
+
+  private final String value;
+
+  private final String externalId;
+  private final String username;
+  private final String emailAddress;
+  private final long expiresAt;
+
+  /**
+   * Creates an access token.
+   *
+   * @param value the raw value of the access token.
+   * @param username the name of the token owner.
+   * @param emailAddress the email address of the token owner.
+   * @param expiresAt time to expiration of this tokens in seconds
+   * since midnight January, 1st, 1970.
+   */
+  public AccessToken(String value, String username, String emailAddress,
+      long expiresAt) {
+    if (value == null) {
+      throw new IllegalArgumentException("token value must not be null");
+    }
+    if (username == null) {
+      throw new IllegalArgumentException("username must not be null");
+    }
+    if (emailAddress == null) {
+      throw new IllegalArgumentException("emailAddress must not be null");
+    }
+    this.value = value;
+    this.username = username;
+    this.externalId = AccountExternalId.SCHEME_EXTERNAL + username;
+    this.emailAddress = emailAddress;
+    this.expiresAt = expiresAt;
+  }
+
+  /**
+   * Returns the value of the access token.
+   */
+  public String getValue() {
+    return value;
+  }
+
+  /**
+   * Returns the external id of the token owner.
+   */
+  public String getExternalId() {
+    return externalId;
+  }
+
+  /**
+   * Returns the name of the token owner.
+   */
+  public String getUserName() {
+    return username;
+  }
+
+  /**
+   * Returns the email address of the token owner.
+   */
+  public String getEmailAddress() {
+    return emailAddress;
+  }
+
+  /**
+   * Returns the timestamp when this token will expire in seconds
+   * since midnight January, 1st, 1970.
+   */
+  public long getExpiresAt() {
+    return expiresAt;
+  }
+
+  /**
+   * Returns <code>true</code> if this token has already expired.
+   */
+  public boolean isExpired() {
+    return System.currentTimeMillis() > expiresAt * 1000;
+  }
+
+  @Override
+  public String toString() {
+    return "{'value':'" + value
+        + "','externalId':'" + externalId
+        + "','userName':'" + username
+        + "','emailAddress':'" + emailAddress
+        + "','expiresAt':" + expiresAt + "}";
+  }
+
+  @Override
+  public int hashCode() {
+    return value.hashCode();
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (this == obj) {
+        return true;
+    }
+    if (!(obj instanceof AccessToken)) {
+      return false;
+    }
+    return Objects.equals(value, ((AccessToken) obj).value);
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/CFOAuthService.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/CFOAuthService.java
new file mode 100644
index 0000000..dbc9e20
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/CFOAuthService.java
@@ -0,0 +1,90 @@
+// 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.googlesource.gerrit.plugins.cfoauth;
+
+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.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+
+import java.io.IOException;
+
+@Singleton
+class CFOAuthService implements OAuthServiceProvider {
+
+  private static final String OAUTH_VERSION = "2.0";
+  private static final String NAME = "Cloud Foundry UAA OAuth2";
+
+  private final UAAClient uaaClient;
+
+  @Inject
+  CFOAuthService(PluginConfigFactory cfgFactory,
+      @PluginName String pluginName,
+      @CanonicalWebUrl Provider<String> urlProvider) {
+    PluginConfig cfg = cfgFactory.getFromGerritConfig(pluginName);
+    String uaaServerUrl = CharMatcher.is('/')
+        .trimTrailingFrom(cfg.getString(InitOAuthConfig.SERVER_URL));
+    String redirectUrl = CharMatcher.is('/')
+        .trimTrailingFrom(urlProvider.get()) + "/oauth";
+    this.uaaClient = new UAAClient(uaaServerUrl,
+        cfg.getString(InitOAuthConfig.CLIENT_ID),
+        cfg.getString(InitOAuthConfig.CLIENT_SECRET),
+        cfg.getBoolean(InitOAuthConfig.VERIFIY_SIGNATURES, true),
+        redirectUrl);
+  }
+
+  @Override
+  public String getAuthorizationUrl() {
+    return uaaClient.getAuthorizationUrl();
+  }
+
+  @Override
+  public OAuthToken getAccessToken(OAuthVerifier rv) {
+    return getAsOAuthToken(uaaClient.getAccessToken(rv.getValue()));
+  }
+
+  @Override
+  public OAuthUserInfo getUserInfo(OAuthToken token) throws IOException {
+    return getAsOAuthUserInfo(uaaClient.toAccessToken(token.getToken()));
+  }
+
+  @Override
+  public String getVersion() {
+    return OAUTH_VERSION;
+  }
+
+  @Override
+  public String getName() {
+    return NAME;
+  }
+
+  private OAuthToken getAsOAuthToken(AccessToken accessToken) {
+    return new OAuthToken(accessToken.getValue(), null, null);
+  }
+
+  private OAuthUserInfo getAsOAuthUserInfo(AccessToken accessToken) {
+    return new OAuthUserInfo(accessToken.getExternalId(),
+        accessToken.getUserName(), accessToken.getEmailAddress(),
+        null, null);
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/HMACSHA256SignatureVerifier.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/HMACSHA256SignatureVerifier.java
new file mode 100644
index 0000000..898e782
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/HMACSHA256SignatureVerifier.java
@@ -0,0 +1,65 @@
+// 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.googlesource.gerrit.plugins.cfoauth;
+
+import static java.nio.charset.StandardCharsets.US_ASCII;
+import static org.apache.commons.codec.binary.Base64.encodeBase64URLSafe;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.text.MessageFormat;
+
+import javax.crypto.Mac;
+import javax.crypto.SecretKey;
+import javax.crypto.spec.SecretKeySpec;
+
+class HMACSHA256SignatureVerifier implements SignatureVerifier {
+
+  private static final String HS256 = "HS256";
+  private static final String HMAC_SHA256 = "HMACSHA256";
+
+  private final SecretKey secretKey;
+
+  public HMACSHA256SignatureVerifier(String secret) {
+    secretKey = new SecretKeySpec(secret.getBytes(US_ASCII), HMAC_SHA256);
+  }
+
+  @Override
+  public boolean verify(String content, String signature) {
+    Mac mac = null;
+    try {
+      mac = Mac.getInstance(HMAC_SHA256);
+    } catch (NoSuchAlgorithmException e) {
+      throw new IllegalStateException(
+          "Runtime does not support HMACSHA256 signatures", e);
+    }
+    try {
+      mac.init(secretKey);
+    } catch (InvalidKeyException e) {
+      throw new IllegalArgumentException(MessageFormat.format(
+          "Invalid HMACSHA256 secret: {0}", secretKey), e);
+    }
+    byte[] digest = mac.doFinal(content.getBytes(US_ASCII));
+    String actualSignature = new String(encodeBase64URLSafe(digest), US_ASCII);
+    return signature.equals(actualSignature);
+  }
+
+  @Override
+  public boolean supports(String algorithm) {
+    return HS256.equalsIgnoreCase(algorithm)
+        || HMAC_SHA256.equalsIgnoreCase(algorithm);
+  }
+
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/HttpModule.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/HttpModule.java
new file mode 100644
index 0000000..a8948dd
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/HttpModule.java
@@ -0,0 +1,46 @@
+// 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.googlesource.gerrit.plugins.cfoauth;
+
+import com.google.gerrit.extensions.annotations.Exports;
+import com.google.gerrit.extensions.annotations.PluginName;
+import com.google.gerrit.extensions.auth.oauth.OAuthServiceProvider;
+import com.google.gerrit.httpd.plugins.HttpPluginModule;
+import com.google.gerrit.server.config.PluginConfig;
+import com.google.gerrit.server.config.PluginConfigFactory;
+import com.google.inject.Inject;
+
+class HttpModule extends HttpPluginModule {
+
+  private final PluginConfigFactory cfgFactory;
+  private final String pluginName;
+
+  @Inject
+  HttpModule(PluginConfigFactory cfgFactory,
+      @PluginName String pluginName) {
+    this.cfgFactory = cfgFactory;
+    this.pluginName = pluginName;
+  }
+
+  @Override
+  protected void configureServlets() {
+    PluginConfig cfg = cfgFactory.getFromGerritConfig(pluginName);
+    if (cfg.getString(InitOAuthConfig.CLIENT_ID) != null) {
+      bind(OAuthServiceProvider.class)
+       .annotatedWith(Exports.named(pluginName))
+       .to(CFOAuthService.class);
+    }
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/InitOAuthConfig.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/InitOAuthConfig.java
new file mode 100644
index 0000000..f0b76fb
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/InitOAuthConfig.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.googlesource.gerrit.plugins.cfoauth;
+
+import com.google.gerrit.extensions.annotations.PluginName;
+import com.google.gerrit.pgm.init.api.ConsoleUI;
+import com.google.gerrit.pgm.init.api.InitStep;
+import com.google.gerrit.pgm.init.api.Section;
+import com.google.inject.Inject;
+
+class InitOAuthConfig implements InitStep {
+  static final String PLUGIN_SECTION = "plugin";
+  static final String SERVER_URL = "serverUrl";
+  static final String CLIENT_ID = "clientId";
+  static final String CLIENT_SECRET = "clientSecret";
+  static final String VERIFIY_SIGNATURES = "verifySignatures";
+
+  static final String DEFAULT_SERVER_URL = "http://localhost:8080/uaa";
+  static final String DEFAULT_CLIENT_ID = "gerrit";
+
+  private final ConsoleUI ui;
+  private final Section cfg;
+
+  @Inject
+  InitOAuthConfig(ConsoleUI ui,
+      Section.Factory sections,
+      @PluginName String pluginName) {
+    this.ui = ui;
+    this.cfg = sections.get(PLUGIN_SECTION, pluginName);
+  }
+
+  @Override
+  public void run() throws Exception {
+    ui.header("Cloud Foundry UAA OAuth 2.0 Authentication Provider");
+    cfg.string("UAA server URL", SERVER_URL, DEFAULT_SERVER_URL);
+    cfg.string("Client id", CLIENT_ID, DEFAULT_CLIENT_ID);
+    cfg.passwordForKey("Client secret", CLIENT_SECRET);
+    cfg.set(VERIFIY_SIGNATURES, Boolean.toString(
+        ui.yesno(true, "Verify token signatures", VERIFIY_SIGNATURES)));
+  }
+
+  @Override
+  public void postRun() throws Exception {
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/SHA265WithRSASignatureVerifier.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/SHA265WithRSASignatureVerifier.java
new file mode 100644
index 0000000..2d175a3
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/SHA265WithRSASignatureVerifier.java
@@ -0,0 +1,91 @@
+// 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.googlesource.gerrit.plugins.cfoauth;
+
+import static java.nio.charset.StandardCharsets.US_ASCII;
+import static org.apache.commons.codec.binary.Base64.decodeBase64;
+import static org.apache.commons.codec.binary.Base64.decodeInteger;
+
+import java.security.InvalidKeyException;
+import java.security.KeyFactory;
+import java.security.NoSuchAlgorithmException;
+import java.security.Signature;
+import java.security.SignatureException;
+import java.security.interfaces.RSAPublicKey;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.RSAPublicKeySpec;
+import java.text.MessageFormat;
+
+class SHA265WithRSASignatureVerifier implements SignatureVerifier {
+
+  private static final String RSA = "RSA";
+  private static final String RS256 = "RS256";
+  private static final String SHA265_WITH_RSA = "SHA256withRSA";
+
+  private final RSAPublicKey publicKey;
+
+  public SHA265WithRSASignatureVerifier(String modulus,
+      String publicExponent) {
+    RSAPublicKeySpec publicKeySpec = new RSAPublicKeySpec(
+        decodeInteger(modulus.getBytes(US_ASCII)),
+        decodeInteger(publicExponent.getBytes(US_ASCII)));
+    KeyFactory keyFactory = null;
+    try {
+      keyFactory = KeyFactory.getInstance(RSA);
+    } catch (NoSuchAlgorithmException e) {
+      throw new IllegalStateException(
+          "Runtime does not support SHA256withRSA signatures", e);
+    }
+    try {
+      this.publicKey = (RSAPublicKey)keyFactory.generatePublic(publicKeySpec);
+    } catch (InvalidKeySpecException e) {
+      throw new IllegalArgumentException(MessageFormat.format(
+          "Invalid RSA public key specification: mod={1}, exp={2}",
+          publicKeySpec.getModulus(),
+          publicKeySpec.getPublicExponent()), e);
+    }
+  }
+
+  @Override
+  public boolean verify(String content, String signature) {
+    Signature rsa = null;
+    try {
+      rsa = Signature.getInstance(SHA265_WITH_RSA);
+    } catch (NoSuchAlgorithmException e) {
+      throw new IllegalStateException(
+          "Runtime does not support SHA256withRSA signatures", e);
+    }
+    try {
+      rsa.initVerify(publicKey);
+    } catch (InvalidKeyException e) {
+      throw new IllegalArgumentException(MessageFormat.format(
+          "Invalid public key: {0}", publicKey), e);
+    }
+    try {
+      rsa.update(content.getBytes(US_ASCII));
+      return rsa.verify(decodeBase64(signature.getBytes(US_ASCII)));
+    } catch (SignatureException e) {
+      throw new IllegalArgumentException(MessageFormat.format(
+          "Invalid signature: {0}", signature), e);
+    }
+  }
+
+  @Override
+  public boolean supports(String algorithm) {
+    return RS256.equalsIgnoreCase(algorithm)
+        || SHA265_WITH_RSA.equalsIgnoreCase(algorithm);
+  }
+
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/SignatureVerifier.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/SignatureVerifier.java
new file mode 100644
index 0000000..0a49775
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/SignatureVerifier.java
@@ -0,0 +1,22 @@
+// 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.googlesource.gerrit.plugins.cfoauth;
+
+interface SignatureVerifier {
+
+  boolean supports(String algorithm);
+
+  boolean verify(String content, String signature);
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UAAClient.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UAAClient.java
new file mode 100644
index 0000000..cb9153b
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UAAClient.java
@@ -0,0 +1,281 @@
+// 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.googlesource.gerrit.plugins.cfoauth;
+
+import static java.net.HttpURLConnection.HTTP_OK;
+import static java.nio.charset.StandardCharsets.US_ASCII;
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.scribe.model.OAuthConstants.CODE;
+import static org.scribe.model.OAuthConstants.REDIRECT_URI;
+import static org.scribe.model.Verb.GET;
+import static org.scribe.model.Verb.POST;
+import static org.scribe.utils.OAuthEncoder.encode;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Strings;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.google.gson.JsonPrimitive;
+
+import org.apache.commons.codec.binary.Base64;
+import org.scribe.model.OAuthRequest;
+import org.scribe.model.Response;
+
+import java.text.MessageFormat;
+
+class UAAClient {
+
+  private static final String OAUTH_ENDPOINT = "%s/oauth/";
+
+  private static final String AUTHORIZE_ENDPOINT = OAUTH_ENDPOINT
+      + "authorize?response_type=code&client_id=%s&redirect_uri=%s";
+  private static final String TOKEN_ENDPOINT = OAUTH_ENDPOINT + "token";
+  private static final String TOKEN_KEY_ENDPOINT = "%s/token_key";
+
+  private static final String GRANT_TYPE = "grant_type";
+  private static final String BY_AUTHORIZATION_CODE = "authorization_code";
+
+  private static final String ALG_ATTRIBUTE = "alg";
+  private static final String VALUE_ATTRIBUTE = "value";
+  private static final String PUBLIC_EXPONENT_ATTRIBUTE = "e";
+  private static final String MODULUS_ATTRIBUTE = "n";
+  private static final String ACCESS_TOKEN_ATTRIBUTE = "access_token";
+  private static final String EXP_ATTRIBUTE = "exp";
+  private static final String USER_NAME_ATTRIBUTE = "user_name";
+  private static final String EMAIL_ATTRIBUTE = "email";
+
+  private static final String AUTHORIZATION_HEADER = "Authorization";
+  private static final String BASIC_AUTHENTICATION = "Basic";
+
+  private final String clientCredentials;
+  private final String redirectUrl;
+
+  private final String authorizationEndpoint;
+  private final String accessTokenEndpoint;
+  private final String tokenKeyEndpoint;
+
+  private final boolean verifySignatures;
+
+  /**
+   * Lazily initialized and may be updated from time to time
+   * when token key is changed in UAA
+   */
+  private SignatureVerifier signatureVerifier;
+
+  public UAAClient(String uaaServerUrl,
+      String clientId,
+      String clientSecret,
+      boolean verifySignatures,
+      String redirectUrl) {
+    this.clientCredentials = BASIC_AUTHENTICATION + " "
+      + encodeBase64(clientId + ":" + clientSecret);
+    this.verifySignatures = verifySignatures;
+    this.redirectUrl = redirectUrl;
+    this.authorizationEndpoint = String.format(AUTHORIZE_ENDPOINT,
+        uaaServerUrl, encode(clientId), encode(redirectUrl));
+    this.accessTokenEndpoint = String.format(TOKEN_ENDPOINT, uaaServerUrl);
+    this.tokenKeyEndpoint = String.format(TOKEN_KEY_ENDPOINT, uaaServerUrl);
+  }
+
+  /**
+   * Returns the authorization grant endpoint of the UAA server.
+   */
+  public String getAuthorizationUrl() {
+    return authorizationEndpoint;
+  }
+
+  /**
+   * Retrieves an access token from the UAA server providing an
+   * authorization code following the "Authorization Code Grant"
+   * scheme of RFC6749 section 4.1.
+   *
+   * @param authorizationCode a previously obtained authorization code.
+   * @return an access token.
+   *
+   * @throws UAAClientException if the UAA request failed.
+   */
+  public AccessToken getAccessToken(String authorizationCode)
+      throws UAAClientException {
+    OAuthRequest request = new OAuthRequest(POST, accessTokenEndpoint);
+    request.addHeader(AUTHORIZATION_HEADER, clientCredentials);
+    request.addBodyParameter(GRANT_TYPE, BY_AUTHORIZATION_CODE);
+    request.addBodyParameter(CODE, authorizationCode);
+    request.addBodyParameter(REDIRECT_URI, redirectUrl);
+    Response response = request.send();
+    if (response.getCode() != HTTP_OK) {
+      throw new UAAClientException(MessageFormat.format(
+          "POST /oauth/token failed with status {0}", response.getCode()));
+    }
+    return parseAccessTokenResponse(response.getBody());
+  }
+
+  /**
+   * Converts an access token given as string represenation
+   * into an {@link AccessToken}.
+   *
+   * @param accessToken the access token to convert.
+   * @return the <code>AccessToken</code> corressponding to the
+   * given access token.
+   *
+   * @throws UAAClientException if the given access token is not
+   * valid or could not be converted into an <code>AccessToken</code>.
+   */
+  public AccessToken toAccessToken(String accessToken)
+      throws UAAClientException {
+    JsonObject jsonWebToken = toJsonWebToken(accessToken);
+    long expiresAt = getLongAttribute(jsonWebToken, EXP_ATTRIBUTE, 0);
+    String username = getAttribute(jsonWebToken, USER_NAME_ATTRIBUTE);
+    if (username == null) {
+      throw new UAAClientException(
+          "Invalid token: missing or invalid 'user_name' attribute");
+    }
+    String emailAddress = getAttribute(jsonWebToken, EMAIL_ATTRIBUTE);
+    if (emailAddress == null) {
+      throw new UAAClientException(
+          "Invalid token: missing or invalid 'email' attribute");
+    }
+    return new AccessToken(accessToken, username, emailAddress, expiresAt);
+  }
+
+  @VisibleForTesting
+  AccessToken parseAccessTokenResponse(String tokenResponse)
+      throws UAAClientException {
+    if (Strings.isNullOrEmpty(tokenResponse)) {
+      throw new UAAClientException(
+          "Can't extract a token from an empty string");
+    }
+    JsonObject json = getAsJsonObject(tokenResponse);
+    String accessToken = getAttribute(json, ACCESS_TOKEN_ATTRIBUTE);
+    if (accessToken == null) {
+      throw new UAAClientException(
+          "Can't extract a token: missing or invalid 'access_token' attribute");
+    }
+    return toAccessToken(accessToken);
+  }
+
+  @VisibleForTesting
+  JsonObject toJsonWebToken(String accessToken)
+      throws UAAClientException {
+    String[] segments = accessToken.split("\\.");
+    if (segments.length != 3) {
+      throw new UAAClientException(
+          "Invalid token: must be of the form 'header.token.signature'");
+    }
+    String claims = decodeBase64(segments[1]);
+    if (verifySignatures) {
+      String header = decodeBase64(segments[0]);
+      String alg = getAttribute(getAsJsonObject(header), ALG_ATTRIBUTE);
+      if (Strings.isNullOrEmpty(alg)) {
+        throw new UAAClientException("Invalid token: missing \"alg\" attribute");
+      }
+      String signature = segments[2];
+      String signedContent = segments[0] + "." + segments[1];
+      verifySignature(signedContent, signature, alg);
+    }
+    return getAsJsonObject(claims);
+  }
+
+  @VisibleForTesting
+  void verifySignature(String signedContent, String signature,
+      String alg) throws UAAClientException {
+    SignatureVerifier verifier = getSignatureVerifier(alg, false);
+    if (!verifier.verify(signedContent, signature)) {
+      // If the signature is invalid, maybe the secret has changed
+      // in the UAA? Obtain a fresh signature verifier and try again
+      verifier = getSignatureVerifier(alg, true);
+      if (!verifier.verify(signedContent, signature)) {
+        throw new UAAClientException(MessageFormat.format(
+            "Invalid token signature ''{0}''", signature));
+      }
+    }
+  }
+
+  @VisibleForTesting
+  synchronized SignatureVerifier getSignatureVerifier(String alg,
+      boolean refresh) throws UAAClientException {
+    if (signatureVerifier == null || refresh) {
+      signatureVerifier = createSignatureVerifier();
+    }
+    if (!signatureVerifier.supports(alg)) {
+      throw new UAAClientException(MessageFormat.format(
+          "Invalid token: unexpected signature algorithm ''{0}''", alg));
+    }
+    return signatureVerifier;
+  }
+
+  private SignatureVerifier createSignatureVerifier()
+      throws UAAClientException {
+    OAuthRequest request = new OAuthRequest(GET, tokenKeyEndpoint);
+    request.addHeader(AUTHORIZATION_HEADER, clientCredentials);
+    Response response = request.send();
+    if (response.getCode() != HTTP_OK) {
+      throw new UAAClientException(MessageFormat.format(
+          "GET /token_key failed with status {0}", response.getCode()));
+    }
+    JsonObject content = getAsJsonObject(response.getBody());
+    String alg = getAttribute(content, ALG_ATTRIBUTE);
+    if (Strings.isNullOrEmpty(alg)) {
+      throw new UAAClientException(
+          "GET /uaa/token_key failed: missing \"alg\" attribute");
+    }
+    if ("HMACSHA256".equals(alg)) {
+      return new HMACSHA256SignatureVerifier(
+          getAttribute(content, VALUE_ATTRIBUTE));
+    } else if ("SHA256withRSA".equals(alg)) {
+      return new SHA265WithRSASignatureVerifier(
+          getAttribute(content, MODULUS_ATTRIBUTE),
+          getAttribute(content, PUBLIC_EXPONENT_ATTRIBUTE));
+    }
+    throw new UAAClientException(MessageFormat.format(
+        "Unsupported signature algorithm ''{0}''", alg));
+  }
+
+  @VisibleForTesting
+  String getAttribute(JsonObject json, String name) {
+    JsonPrimitive prim = getAsJsonPrimitive(json, name);
+    return prim != null && prim.isString() ? prim.getAsString() : null;
+  }
+
+  @VisibleForTesting
+  long getLongAttribute(JsonObject json, String name, long defaultValue) {
+    JsonPrimitive prim = getAsJsonPrimitive(json, name);
+    return prim != null && prim.isNumber() ? prim.getAsLong() : defaultValue;
+  }
+
+  private JsonPrimitive getAsJsonPrimitive(JsonObject json, String name) {
+    JsonElement attr = json.get(name);
+    if (attr == null || !attr.isJsonPrimitive()) {
+      return null;
+    }
+    return attr.getAsJsonPrimitive();
+  }
+
+  private JsonObject getAsJsonObject(String s) {
+    JsonElement json = new JsonParser().parse(s);
+    if (!json.isJsonObject()) {
+      return new JsonObject();
+    }
+    return json.getAsJsonObject();
+  }
+
+  private String decodeBase64(String s) {
+    return new String(Base64.decodeBase64(s), UTF_8);
+  }
+
+  private String encodeBase64(String s) {
+    return new String(Base64.encodeBase64(s.getBytes(UTF_8)), US_ASCII);
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UAAClientException.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UAAClientException.java
new file mode 100644
index 0000000..e6f5304
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/UAAClientException.java
@@ -0,0 +1,28 @@
+// 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.googlesource.gerrit.plugins.cfoauth;
+
+class UAAClientException extends RuntimeException {
+
+  private static final long serialVersionUID = 1L;
+
+  public UAAClientException(String message) {
+    super(message);
+  }
+
+  public UAAClientException(String message, Throwable cause) {
+    super(message, cause);
+  }
+}
diff --git a/src/main/resources/Documentation/build.md b/src/main/resources/Documentation/build.md
new file mode 100644
index 0000000..dd62be3
--- /dev/null
+++ b/src/main/resources/Documentation/build.md
@@ -0,0 +1,69 @@
+Build
+=====
+This plugin can be built with Buck.
+
+Buck
+----
+Two build modes are supported: Standalone and in Gerrit tree.
+The standalone build mode is recommended, as this mode doesn't require
+the Gerrit tree to exist locally.
+
+### Build standalone
+
+Clone bucklets library:
+
+```
+  git clone https://gerrit.googlesource.com/bucklets
+```
+
+and link it to @PLUGIN@ plugin directory:
+
+```
+  cd @PLUGIN@ && ln -s ../bucklets .
+```
+
+Add link to the .buckversion file:
+
+```
+  cd @PLUGIN@ && ln -s bucklets/buckversion .buckversion
+```
+
+Add link to the .watchmanconfig file:
+
+```
+  cd @PLUGIN@ && ln -s bucklets/watchmanconfig .watchmanconfig
+```
+
+To build the plugin, issue the following command:
+
+```
+  buck build plugin
+```
+
+The output is created in
+
+```
+  buck-out/gen/@PLUGIN@.jar
+```
+
+### Build in Gerrit tree
+
+Clone or link this plugin to the plugins directory of Gerrit's source
+tree, and issue the command:
+
+```
+  buck build plugins/@PLUGIN@
+```
+
+The output is created in
+
+```
+  buck-out/gen/plugins/@PLUGIN@/@PLUGIN@.jar
+```
+
+This project can be imported into the Eclipse IDE:
+
+```
+  ./tools/eclipse/project.py
+```
+
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
new file mode 100644
index 0000000..75fc683
--- /dev/null
+++ b/src/main/resources/Documentation/config.md
@@ -0,0 +1,75 @@
+Configuration
+=============
+
+## Registering a Client for Gerrit
+
+Gerrit must be registered as client with the [CloudFoundry User Account and
+Authentication (UAA) Server](https://github.com/cloudfoundry/uaa) that acts
+as OAuth2 authentication and authorization backend.
+
+The following sequence assumes that the UAA client application (`uaac`) is
+installed. It will create a client with name `gerrit`.
+
+```
+  uaac target <URL of the UAA server>
+
+  uaac token client get admin
+
+  uaac client add gerrit
+    --authorities uaa.resource
+    --authorized_grant_type authorization_code,refresh_token,password
+    --scope openid
+    --autoapprove openid
+    --access_token_validity <time in seconds>
+    --redirect_uri <URL of the Gerrit server>/oauth
+    --secret <client secret>
+```
+
+Make sure to choose a strong password for `secret`. Gerrit uses
+this password to obtain access tokens on behalf of its users.
+
+## Configuring the @PLUGIN@ Plugin
+
+The configuration of the @PLUGIN@ plugin is done in the `gerrit.config`
+file. Note that `auth.type` must be set to `OAUTH`.
+
+```
+[auth]
+  type = OAUTH
+
+[plugin "@PLUGIN@"]
+  serverUrl = <URL of the UAA server>
+  clientId = "<client id>"
+  clientSecret = "<client secret>"
+  verifySignatures = true
+```
+
+The parameters `clientId` and `clientSecret` must match the name and
+password of the Gerrit client as registered with the UAA server above.
+The `serverUrl` must point to the UAA server and include the context path,
+e.g `http(s)://example.org/uaa`.
+
+Alternatively, re-run `init` to configure the @PLUGIN@ plugin:
+
+```
+  java -jar gerrit.war init -d <site>
+  [...]
+
+  *** Cloud Foundry UAA OAuth 2.0 Authentication Provider
+  ***
+
+  UAA server URL    [http://localhost:8080/uaa]: <URL of the UAA server>
+  Client id         [gerrit]: <client id>
+  Client secret             : <client secret>
+           confirm password : <client secret>
+  Verify token signatures [Y/n]?
+```
+
+UAA issues so-called [JSON Web Tokens](http://tools.ietf.org/html/rfc7519]),
+which include a signature. By default, the @PLUGIN@ plugin will verify
+signatures of access tokens it received from UAA. Both HMACSHA256 and
+SHA256withRSA signatures are supported given that the underlying Java runtime
+provides the necessary ciphers. If that is not the case you might switch off
+the verification by setting the parameter `verifySignatures` to `false`.
+Note that this is strongly discouraged for security reasons.
+
diff --git a/src/test/java/com/googlesource/gerrit/plugins/cfoauth/UAAClientTest.java b/src/test/java/com/googlesource/gerrit/plugins/cfoauth/UAAClientTest.java
new file mode 100644
index 0000000..160b8ea
--- /dev/null
+++ b/src/test/java/com/googlesource/gerrit/plugins/cfoauth/UAAClientTest.java
@@ -0,0 +1,181 @@
+// 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.googlesource.gerrit.plugins.cfoauth;
+
+import static org.junit.Assert.*;
+
+import com.google.gson.JsonObject;
+
+import com.googlesource.gerrit.plugins.cfoauth.AccessToken;
+import com.googlesource.gerrit.plugins.cfoauth.HMACSHA256SignatureVerifier;
+import com.googlesource.gerrit.plugins.cfoauth.SignatureVerifier;
+import com.googlesource.gerrit.plugins.cfoauth.UAAClient;
+import com.googlesource.gerrit.plugins.cfoauth.UAAClientException;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class UAAClientTest {
+
+  private static final String HS256_TEST_TOKEN =
+      "eyJhbGciOiJIUzI1NiJ9.eyJqdGkiOiI4MWI4M2RhNy0yZmI2LTQ4OTUtYTM5ZS0zZ"
+      + "TFjZWEzNzQ2ZDkiLCJzdWIiOiJmNmM1YTgxMi0yNWM2LTQ5ZjItOTJiMS0yYjQ5N"
+      + "mRjOTAyNTUiLCJzY29wZSI6WyJvcGVuaWQiXSwiY2xpZW50X2lkIjoiZ2Vycml0L"
+      + "WlkIiwiY2lkIjoiZ2Vycml0LWlkIiwiYXpwIjoiZ2Vycml0LWlkIiwiZ3JhbnRfd"
+      + "HlwZSI6ImF1dGhvcml6YXRpb25fY29kZSIsInVzZXJfaWQiOiJmNmM1YTgxMi0yN"
+      + "WM2LTQ5ZjItOTJiMS0yYjQ5NmRjOTAyNTUiLCJ1c2VyX25hbWUiOiJtYXJpc3NhI"
+      + "iwiZW1haWwiOiJtYXJpc3NhQHRlc3Qub3JnIiwicmV2X3NpZyI6IjkwZGQzNTNlI"
+      + "iwiaWF0IjoxNDM2MTg5NzMyLCJleHAiOjE0MzYyMzI5MzIsImlzcyI6Imh0dHA6L"
+      + "y9sb2NhbGhvc3Q6ODA4MC91YWEvb2F1dGgvdG9rZW4iLCJ6aWQiOiJ1YWEiLCJhd"
+      + "WQiOlsiZ2Vycml0LWlkIiwib3BlbmlkIl19.ynnx6J9CO-jnKETDn4DSEdvWMZkC"
+      + "2mTynnhgYL-TyaU";
+
+  private static final String[] HS256_TOKEN_PARTS =
+      HS256_TEST_TOKEN.split("\\.");
+
+  private static final String HS256_SIGNED_CONTENT =
+      HS256_TOKEN_PARTS[0] + "." + HS256_TOKEN_PARTS[1];
+  private static final String HS256_SIGNATURE =
+      HS256_TOKEN_PARTS[2];
+  private static final String HS256_INVALID_SIGNATURE =
+      ".dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk";
+
+
+  private static final String HS256_TOKEN_INVALID_HEADER = ""
+      + "foo" + HS256_TOKEN_PARTS[1] + "." + HS256_TOKEN_PARTS[2];
+  private static final String HS256_TOKEN_INVLID_CLAIMS =
+      HS256_TOKEN_PARTS[0] + ".foo." + HS256_TOKEN_PARTS[2];
+  private static final String HS256_TOKEN_INVALID_SIGNATURE =
+      HS256_TOKEN_PARTS[0] + "." + HS256_TOKEN_PARTS[1]
+          + HS256_INVALID_SIGNATURE;
+
+  private static final String HS256_ACCESS_TOKEN_RESPONSE = "{"
+      + "\"access_token\":\"" + HS256_TEST_TOKEN + "\","
+      + "\"token_type\":\"bearer\","
+      + "\"expires_in\":3600}";
+
+  private static final String MISSING_ACCESS_TOKEN_ATTRIBUTE= "{"
+      + "\"access_token1\":\"" + HS256_TEST_TOKEN + "\"}";
+
+  private static final String INVALID_TOKEN_ATTRIBUTE= "{"
+      + "\"access_token\":\"" + HS256_TOKEN_INVALID_SIGNATURE + "\"}";
+
+  private static final String UAA_SERVER_URL = "http://uaa.example.org/uaa";
+  private static final String CLIENT_ID = "gerrit";
+  private static final String CLIENT_SECRET = "gerritsecret";
+  private static final String REDIRECT_URL = "http://gerrit.example.org/oauth";
+
+  private static final String TOKEN_KEY = "tokenkey";
+
+  private static class UAATestClient extends UAAClient {
+
+    public UAATestClient() {
+      super(UAA_SERVER_URL, CLIENT_ID, CLIENT_SECRET, true, REDIRECT_URL);
+    }
+
+    @Override
+    SignatureVerifier getSignatureVerifier(String alg, boolean refresh)
+        throws UAAClientException {
+      return new HMACSHA256SignatureVerifier(TOKEN_KEY);
+    }
+  }
+
+  private UAAClient client;
+
+  @Before
+  public void setup() throws Exception {
+    client = new UAATestClient();
+  }
+
+  @Test
+  public void testGetAuthorizationUrl() throws Exception {
+    assertEquals("http://uaa.example.org/uaa/oauth/authorize?"
+        + "response_type=code&client_id=gerrit&redirect_uri="
+        + "http%3A%2F%2Fgerrit.example.org%2Foauth",
+        client.getAuthorizationUrl());
+  }
+
+  @Test
+  public void testToJsonWebToken() throws Exception {
+    JsonObject jsonWebToken = client.toJsonWebToken(HS256_TEST_TOKEN);
+    assertEquals("marissa", client.getAttribute(jsonWebToken, "user_name"));
+    assertEquals("marissa@test.org", client.getAttribute(jsonWebToken, "email"));
+    assertEquals(1436232932L, client.getLongAttribute(jsonWebToken, "exp", 0));
+  }
+
+  @Test(expected = UAAClientException.class)
+  public void testToJsonWebTokenInvalidToken() throws Exception {
+    client.toJsonWebToken("foobar");
+  }
+
+  @Test(expected = UAAClientException.class)
+  public void testToJsonWebTokenInvalidPrefix() throws Exception {
+    client.toJsonWebToken(HS256_TOKEN_INVALID_HEADER);
+  }
+
+  @Test(expected = UAAClientException.class)
+  public void testToJsonWebTokenInvalidClaims() throws Exception {
+    client.toJsonWebToken(HS256_TOKEN_INVLID_CLAIMS);
+  }
+
+  @Test(expected = UAAClientException.class)
+  public void testToJsonWebTokenInvalidSignature() throws Exception {
+    client.toJsonWebToken(HS256_TOKEN_INVALID_SIGNATURE);
+  }
+
+  @Test
+  public void testGetAsAccessToken() throws Exception {
+    AccessToken accessToken = client.toAccessToken(HS256_TEST_TOKEN);
+    assertHS266AccessToken(accessToken);
+  }
+
+  @Test
+  public void testVerifySignature() throws Exception {
+    client.verifySignature(HS256_SIGNED_CONTENT, HS256_SIGNATURE, "HS256");
+  }
+
+  @Test(expected = UAAClientException.class)
+  public void testVerifyInvalidSignature() throws Exception {
+    client.verifySignature(HS256_SIGNED_CONTENT, HS256_INVALID_SIGNATURE,
+        "HS256");
+  }
+
+  @Test
+  public void testParseAccessTokenResponse() throws Exception {
+    AccessToken accessToken = client.parseAccessTokenResponse(
+        HS256_ACCESS_TOKEN_RESPONSE);
+    assertHS266AccessToken(accessToken);
+  }
+
+  @Test(expected = UAAClientException.class)
+  public void testParseAccessTokenResponseMissingAccessTokenAttribute()
+      throws Exception {
+    client.parseAccessTokenResponse(MISSING_ACCESS_TOKEN_ATTRIBUTE);
+  }
+
+  @Test(expected = UAAClientException.class)
+  public void testParseAccessTokenResponseInvalidTokenAttribute()
+      throws Exception {
+    client.parseAccessTokenResponse(INVALID_TOKEN_ATTRIBUTE);
+  }
+
+  private void assertHS266AccessToken(AccessToken accessToken) {
+    assertEquals(HS256_TEST_TOKEN, accessToken.getValue());
+    assertEquals(1436232932L, accessToken.getExpiresAt());
+    assertEquals("external:marissa", accessToken.getExternalId());
+    assertEquals("marissa", accessToken.getUserName());
+    assertEquals("marissa@test.org", accessToken.getEmailAddress());
+  }
+}