ResponseProtocolCompliance.java

/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */
package com.apigee.sdk.apm.http.impl.client.cache;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import org.apache.http.Header;
import org.apache.http.HeaderElement;
import org.apache.http.HttpEntityEnclosingRequest;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.HttpVersion;
import org.apache.http.ProtocolVersion;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.impl.client.RequestWrapper;
import org.apache.http.impl.cookie.DateParseException;
import org.apache.http.impl.cookie.DateUtils;
import org.apache.http.message.BasicHeader;
import org.apache.http.protocol.HTTP;

import com.apigee.sdk.apm.http.annotation.Immutable;
import com.apigee.sdk.apm.http.client.cache.HeaderConstants;

/**
 * @since 4.1
 */
@Immutable
class ResponseProtocolCompliance {

	/**
	 * When we get a response from a down stream server (Origin Server) we
	 * attempt to see if it is HTTP 1.1 Compliant and if not, attempt to make it
	 * so.
	 * 
	 * @param request
	 *            The {@link HttpRequest} that generated an origin hit and
	 *            response
	 * @param response
	 *            The {@link HttpResponse} from the origin server
	 * @throws ClientProtocolException
	 *             when we are unable to 'convert' the response to a compliant
	 *             one
	 */
	public void ensureProtocolCompliance(HttpRequest request,
			HttpResponse response) throws ClientProtocolException {
		if (backendResponseMustNotHaveBody(request, response)) {
			response.setEntity(null);
		}

		authenticationRequiredDidNotHaveAProxyAuthenticationHeader(request,
				response);

		notAllowedResponseDidNotHaveAnAllowHeader(request, response);

		unauthorizedResponseDidNotHaveAWWWAuthenticateHeader(request, response);

		requestDidNotExpect100ContinueButResponseIsOne(request, response);

		transferEncodingIsNotReturnedTo1_0Client(request, response);

		ensurePartialContentIsNotSentToAClientThatDidNotRequestIt(request,
				response);

		ensure200ForOPTIONSRequestWithNoBodyHasContentLengthZero(request,
				response);

		ensure206ContainsDateHeader(response);

		identityIsNotUsedInContentEncoding(response);

		warningsWithNonMatchingWarnDatesAreRemoved(response);
	}

	private void warningsWithNonMatchingWarnDatesAreRemoved(
			HttpResponse response) {
		Date responseDate = null;
		try {
			responseDate = DateUtils.parseDate(response.getFirstHeader("Date")
					.getValue());
		} catch (DateParseException e) {
		}
		if (responseDate == null)
			return;
		Header[] warningHeaders = response.getHeaders("Warning");
		if (warningHeaders == null || warningHeaders.length == 0)
			return;
		List<Header> newWarningHeaders = new ArrayList<Header>();
		boolean modified = false;
		for (Header h : warningHeaders) {
			for (WarningValue wv : WarningValue.getWarningValues(h)) {
				Date warnDate = wv.getWarnDate();
				if (warnDate == null || warnDate.equals(responseDate)) {
					newWarningHeaders.add(new BasicHeader("Warning", wv
							.toString()));
				} else {
					modified = true;
				}
			}
		}
		if (modified) {
			response.removeHeaders("Warning");
			for (Header h : newWarningHeaders) {
				response.addHeader(h);
			}
		}
	}

	private void identityIsNotUsedInContentEncoding(HttpResponse response) {
		Header[] hdrs = response.getHeaders("Content-Encoding");
		if (hdrs == null || hdrs.length == 0)
			return;
		List<Header> newHeaders = new ArrayList<Header>();
		boolean modified = false;
		for (Header h : hdrs) {
			StringBuilder buf = new StringBuilder();
			boolean first = true;
			for (HeaderElement elt : h.getElements()) {
				if ("identity".equalsIgnoreCase(elt.getName())) {
					modified = true;
				} else {
					if (!first)
						buf.append(",");
					buf.append(elt.toString());
					first = false;
				}
			}
			String newHeaderValue = buf.toString();
			if (!"".equals(newHeaderValue)) {
				newHeaders.add(new BasicHeader("Content-Encoding",
						newHeaderValue));
			}
		}
		if (!modified)
			return;
		response.removeHeaders("Content-Encoding");
		for (Header h : newHeaders) {
			response.addHeader(h);
		}
	}

	private void authenticationRequiredDidNotHaveAProxyAuthenticationHeader(
			HttpRequest request, HttpResponse response)
			throws ClientProtocolException {
		if (response.getStatusLine().getStatusCode() != HttpStatus.SC_PROXY_AUTHENTICATION_REQUIRED)
			return;

		if (response.getFirstHeader(HeaderConstants.PROXY_AUTHENTICATE) == null)
			throw new ClientProtocolException(
					"407 Response did not contain a Proxy-Authentication header");
	}

	private void notAllowedResponseDidNotHaveAnAllowHeader(HttpRequest request,
			HttpResponse response) throws ClientProtocolException {
		if (response.getStatusLine().getStatusCode() != HttpStatus.SC_METHOD_NOT_ALLOWED)
			return;

		if (response.getFirstHeader(HeaderConstants.ALLOW) == null)
			throw new ClientProtocolException(
					"405 Response did not contain an Allow header.");
	}

	private void unauthorizedResponseDidNotHaveAWWWAuthenticateHeader(
			HttpRequest request, HttpResponse response)
			throws ClientProtocolException {
		if (response.getStatusLine().getStatusCode() != HttpStatus.SC_UNAUTHORIZED)
			return;

		if (response.getFirstHeader(HeaderConstants.WWW_AUTHENTICATE) == null) {
			throw new ClientProtocolException(
					"401 Response did not contain required WWW-Authenticate challenge header");
		}
	}

	private void ensure206ContainsDateHeader(HttpResponse response) {
		if (response.getFirstHeader(HTTP.DATE_HEADER) == null) {
			response.addHeader(HTTP.DATE_HEADER,
					DateUtils.formatDate(new Date()));
		}

	}

	private void ensurePartialContentIsNotSentToAClientThatDidNotRequestIt(
			HttpRequest request, HttpResponse response)
			throws ClientProtocolException {
		if (request.getFirstHeader(HeaderConstants.RANGE) != null)
			return;

		if (response.getFirstHeader(HeaderConstants.CONTENT_RANGE) != null) {
			throw new ClientProtocolException(
					"Content-Range was returned for a request that did not ask for a Content-Range.");
		}

	}

	private void ensure200ForOPTIONSRequestWithNoBodyHasContentLengthZero(
			HttpRequest request, HttpResponse response) {
		if (!request.getRequestLine().getMethod()
				.equalsIgnoreCase(HeaderConstants.OPTIONS_METHOD)) {
			return;
		}

		if (response.getStatusLine().getStatusCode() != HttpStatus.SC_OK) {
			return;
		}

		if (response.getFirstHeader(HTTP.CONTENT_LEN) == null) {
			response.addHeader(HTTP.CONTENT_LEN, "0");
		}
	}

	private boolean backendResponseMustNotHaveBody(HttpRequest request,
			HttpResponse backendResponse) {
		return HeaderConstants.HEAD_METHOD.equals(request.getRequestLine()
				.getMethod())
				|| backendResponse.getStatusLine().getStatusCode() == HttpStatus.SC_NO_CONTENT
				|| backendResponse.getStatusLine().getStatusCode() == HttpStatus.SC_RESET_CONTENT
				|| backendResponse.getStatusLine().getStatusCode() == HttpStatus.SC_NOT_MODIFIED;
	}

	private void requestDidNotExpect100ContinueButResponseIsOne(
			HttpRequest request, HttpResponse response)
			throws ClientProtocolException {
		if (response.getStatusLine().getStatusCode() != HttpStatus.SC_CONTINUE) {
			return;
		}

		if (!requestWasWrapped(request)) {
			return;
		}

		ProtocolVersion originalProtocol = getOriginalRequestProtocol((RequestWrapper) request);

		if (originalProtocol.compareToVersion(HttpVersion.HTTP_1_1) >= 0) {
			return;
		}

		if (originalRequestDidNotExpectContinue((RequestWrapper) request)) {
			throw new ClientProtocolException(
					"The incoming request did not contain a "
							+ "100-continue header, but the response was a Status 100, continue.");

		}
	}

	private void transferEncodingIsNotReturnedTo1_0Client(HttpRequest request,
			HttpResponse response) {
		if (!requestWasWrapped(request)) {
			return;
		}

		ProtocolVersion originalProtocol = getOriginalRequestProtocol((RequestWrapper) request);

		if (originalProtocol.compareToVersion(HttpVersion.HTTP_1_1) >= 0) {
			return;
		}

		removeResponseTransferEncoding(response);
	}

	private void removeResponseTransferEncoding(HttpResponse response) {
		response.removeHeaders("TE");
		response.removeHeaders(HTTP.TRANSFER_ENCODING);
	}

	private boolean originalRequestDidNotExpectContinue(RequestWrapper request) {

		try {
			HttpEntityEnclosingRequest original = (HttpEntityEnclosingRequest) request
					.getOriginal();

			return !original.expectContinue();
		} catch (ClassCastException ex) {
			return false;
		}
	}

	private ProtocolVersion getOriginalRequestProtocol(RequestWrapper request) {
		return request.getOriginal().getProtocolVersion();
	}

	private boolean requestWasWrapped(HttpRequest request) {
		return request instanceof RequestWrapper;
	}

}