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+/**
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+ * Licensed under the Apache License, Version 2.0 (the "License");
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+ * you may not use this file except in compliance with the License.
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+ * You may obtain a copy of the License at
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+ *
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+ * http://www.apache.org/licenses/LICENSE-2.0
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+ *
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+ * Unless required by applicable law or agreed to in writing, software
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+ * distributed under the License is distributed on an "AS IS" BASIS,
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+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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+ * See the License for the specific language governing permissions and
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+ * limitations under the License. See accompanying LICENSE file.
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+ */
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+package org.apache.hadoop.security.authentication.server;
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+
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+import java.io.IOException;
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+import java.util.Properties;
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+import javax.servlet.ServletException;
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+import javax.servlet.http.HttpServletRequest;
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+import javax.servlet.http.HttpServletResponse;
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+import org.apache.hadoop.security.authentication.client.AuthenticationException;
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+
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+ /**
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+ * The {@link AltKerberosAuthenticationHandler} behaves exactly the same way as
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+ * the {@link KerberosAuthenticationHandler}, except that it allows for an
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+ * alternative form of authentication for browsers while still using Kerberos
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+ * for Java access. This is an abstract class that should be subclassed
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+ * to allow a developer to implement their own custom authentication for browser
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+ * access. The alternateAuthenticate method will be called whenever a request
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+ * comes from a browser.
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+ * <p/>
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+ */
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+public abstract class AltKerberosAuthenticationHandler
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+ extends KerberosAuthenticationHandler {
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+
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+ /**
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+ * Constant that identifies the authentication mechanism.
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+ */
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+ public static final String TYPE = "alt-kerberos";
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+
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+ /**
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+ * Constant for the configuration property that indicates which user agents
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+ * are not considered browsers (comma separated)
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+ */
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+ public static final String NON_BROWSER_USER_AGENTS =
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+ TYPE + ".non-browser.user-agents";
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+ private static final String NON_BROWSER_USER_AGENTS_DEFAULT =
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+ "java,curl,wget,perl";
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+
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+ private String[] nonBrowserUserAgents;
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+
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+ /**
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+ * Returns the authentication type of the authentication handler,
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+ * 'alt-kerberos'.
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+ * <p/>
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+ *
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+ * @return the authentication type of the authentication handler,
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+ * 'alt-kerberos'.
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+ */
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+ @Override
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+ public String getType() {
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+ return TYPE;
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+ }
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+
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+ @Override
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+ public void init(Properties config) throws ServletException {
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+ super.init(config);
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+
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+ nonBrowserUserAgents = config.getProperty(
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+ NON_BROWSER_USER_AGENTS, NON_BROWSER_USER_AGENTS_DEFAULT)
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+ .split("\\W*,\\W*");
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+ for (int i = 0; i < nonBrowserUserAgents.length; i++) {
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+ nonBrowserUserAgents[i] = nonBrowserUserAgents[i].toLowerCase();
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+ }
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+ }
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+
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+ /**
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+ * It enforces the the Kerberos SPNEGO authentication sequence returning an
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+ * {@link AuthenticationToken} only after the Kerberos SPNEGO sequence has
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+ * completed successfully (in the case of Java access) and only after the
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+ * custom authentication implemented by the subclass in alternateAuthenticate
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+ * has completed successfully (in the case of browser access).
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+ * <p/>
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+ *
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+ * @param request the HTTP client request.
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+ * @param response the HTTP client response.
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+ *
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+ * @return an authentication token if the request is authorized or null
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+ *
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+ * @throws IOException thrown if an IO error occurred
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+ * @throws AuthenticationException thrown if an authentication error occurred
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+ */
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+ @Override
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+ public AuthenticationToken authenticate(HttpServletRequest request,
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+ HttpServletResponse response)
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+ throws IOException, AuthenticationException {
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+ AuthenticationToken token;
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+ if (isBrowser(request.getHeader("User-Agent"))) {
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+ token = alternateAuthenticate(request, response);
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+ }
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+ else {
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+ token = super.authenticate(request, response);
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+ }
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+ return token;
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+ }
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+
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+ /**
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+ * This method parses the User-Agent String and returns whether or not it
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+ * refers to a browser. If its not a browser, then Kerberos authentication
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+ * will be used; if it is a browser, alternateAuthenticate from the subclass
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+ * will be used.
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+ * <p/>
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+ * A User-Agent String is considered to be a browser if it does not contain
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+ * any of the values from alt-kerberos.non-browser.user-agents; the default
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+ * behavior is to consider everything a browser unless it contains one of:
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+ * "java", "curl", "wget", or "perl". Subclasses can optionally override
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+ * this method to use different behavior.
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+ *
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+ * @param userAgent The User-Agent String, or null if there isn't one
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+ * @return true if the User-Agent String refers to a browser, false if not
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+ */
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+ protected boolean isBrowser(String userAgent) {
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+ if (userAgent == null) {
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+ return false;
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+ }
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+ userAgent = userAgent.toLowerCase();
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+ boolean isBrowser = true;
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+ for (String nonBrowserUserAgent : nonBrowserUserAgents) {
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+ if (userAgent.contains(nonBrowserUserAgent)) {
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+ isBrowser = false;
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+ break;
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+ }
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+ }
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+ return isBrowser;
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+ }
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+
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+ /**
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+ * Subclasses should implement this method to provide the custom
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+ * authentication to be used for browsers.
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+ *
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+ * @param request the HTTP client request.
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+ * @param response the HTTP client response.
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+ * @return an authentication token if the request is authorized, or null
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+ * @throws IOException thrown if an IO error occurs
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+ * @throws AuthenticationException thrown if an authentication error occurs
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+ */
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+ public abstract AuthenticationToken alternateAuthenticate(
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+ HttpServletRequest request, HttpServletResponse response)
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+ throws IOException, AuthenticationException;
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+}
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