浙林龙哥

   :: 首页  :: 新随笔  :: 联系 :: 订阅 订阅  :: 管理
如何使用HttpClient认证机制
本文介绍HttpClient的认证机制,并给出示例代码。
author: ZJ 07-11-21

本文出自 “子 孑” 博客,请务必保留此出处http://zhangjunhd.blog.51cto.com/113473/51919

英文版(无代码示例): http://hc.apache.org/httpclient-3.x/authentication.html


<!--[if !vml]--><!--[endif]-->
     HttpClient三种不同的认证方案: Basic, Digest and NTLM. 这些方案可用于服务器或代理对客户端的认证简称服务器认证或代理认证。
1.服务器认证(Server Authentication)
HttpClient处理服务器认证几乎是透明的,仅需要开发人员提供登录信息(login credentials)。登录信息保存在HttpState类的实例中,可以通过 setCredentials(String realm, Credentials cred)getCredentials(String realm)来获取或设置。
HttpClient内建的自动认证,可以通过HttpMethod类的setDoAuthentication(boolean doAuthentication)方法关闭,而且这次关闭只影响HttpMethod当前的实例。
 
1.1抢先认证(Preemptive Authentication)
在这种模式时,HttpClient会主动将basic认证应答信息传给服务器,即使在某种情况下服务器可能返回认证失败的应答,这样做主要是为了减少连接的建立。使用该机制如下所示:
client.getParams().setAuthenticationPreemptive(true);
抢先认证模式也提供对于特定目标或代理的缺省认证。如果没有提供缺省的认证信息,则该模式会失效。
Credentials defaultcreds = new UsernamePasswordCredentials("username", "password");
client.getState().setCredentials(new AuthScope("myhost", 80, AuthScope.ANY_REALM), defaultcreds);
Httpclient实现的抢先认证遵循rfc2617.
A client SHOULD assume that all paths at or deeper than the depth of the last symbolic element in the path field of the Request-URI also are within the protection space specified by the Basic realm value of the current challenge. A client MAY preemptively send the corresponding Authorization header with requests for resources in that space without receipt of another challenge from the server. Similarly, when a client sends a request to a proxy, it may reuse a userid and password in the Proxy-Authorization header field without receiving another challenge from the proxy server.
 
1.2服务器认证的安全方面考虑
当需要与不被信任的站点或web应用通信时,应该谨慎使用缺省的认证机制。当启动(activate)抢先认证模式,或者认证中没有明确给出认证域,主机的HttpClient将使用缺省的认证机制去试图获得目标站点的授权。
如果你提供的认证信息是敏感的,你应该指定认证域。不推荐将认证域指定为AuthScope.ANY。(只有在debugging情况下,才使用)
// To be avoided unless in debug mode
Credentials defaultcreds = new UsernamePasswordCredentials("username", "password");
client.getState().setCredentials(AuthScope.ANY, defaultcreds);
2.代理认证(proxy authentication)
  除了登录信息需单独存放以外,代理认证与服务器认证几乎一致。用 setProxyCredentials(String realm, Credentials cred) getProxyCredentials(String realm)设、取登录信息。
3.认证方案(authentication schemes)
3.1Basic
HTTP中规定最早的也是最兼容的方案,遗憾的是也是最不安全的一个方案,因为它以明码传送用户名和密码。它要求一个UsernamePasswordCredentials实例,可以指定服务器端的访问空间或采用默认的登录信息。
 
3.2 Digest
是在HTTP1.1 中增加的一个方案,虽然不如Basic得到的软件支持多,但还是有广泛的使用。Digest方案比Basic方案安全得多,因它根本就不通过网络传送实际的密码,传送的是利用这个密码对从服务器传来的一个随机数(nonce)的加密串。
它要求一个UsernamePasswordCredentials实例,可以指定服务器端的访问空间或采用默认的登录信息。
 
3.3 NTLM
这是HttpClient支持的最复杂的认证协议。它Microsoft设计的一个私有协议,没有公开的规范说明。一开始由于设计的缺陷,NTLM的安全性比 Digest差,后来经过一个ServicePack补丁后,安全性则比较Digest高。
NTLM需要一个NTCredentials实例。 注意,由于NTLM不使用访问空间(realms)的概念,HttpClient利用服务器的域名作访问空间的名字。还需要注意,提供给 NTCredentials的用户名,不要用域名的前缀 - : "adrian" 是正确的,而 "DOMAIN\adrian" 则是错的。
NTLM认证的工作机制与basicdigest有很大的差别。这些差别一般由HttpClient处理,但理解这些差别有助避免在使用NTLM认证时出现错误。
[1] HttpClientAPI的角度来看,NTLM与其它认证方式一样的工作,差别是需要提供'NTCredentials'实例而不是'UsernamePasswordCredentials'(其实,前者只是扩展了后者)
[2] NTLM认证,访问空间是连接到的机器的域名,这对多域名主机会有一些麻烦。只有HttpClient连接中指定的域名才是认证用的域名。建议将realm设为null以使用默认的设置。
[3] NTLM只是认证了一个连接而不是一请求,所以每当一个新的连接建立就要进行一次认证,且在认证的过程中保持连接是非常重要的。 因此,NTLM不能同时用于代理认证和服务器认证,也不能用于HTTP1.0连接或服务器不支持持久连接(keep-alives)的情况。
关于NTLM认证机制更详细的研究,可参考http://davenport.sourceforge.net/ntlm.html
 
3.4选择认证
一些服务器支持多种认证方案。假设一次只能使用一种认证方案,HttpClient必须选择使用哪种。HttpClient选择是基于NTLM, Digest, Basic顺序的。
在具体情况下,可以更改该顺序。可通过参数'http.auth.scheme-priority'来实现,该参数值应该被存放在一个String类型的List中。选择优先级是按插入顺序确定的。
HttpClient client = new HttpClient();
List authPrefs = new ArrayList(2);
authPrefs.add(AuthPolicy.DIGEST);
authPrefs.add(AuthPolicy.BASIC);
// This will exclude the NTLM authentication scheme
client.getParams().setParameter(AuthPolicy.AUTH_SCHEME_PRIORITY, authPrefs);
 
3.5定制认证方案
HttpClient本身支持basic, digest, and NTLM这三种认证方案。同时,它也提供了加载额外定制的认证方案的功能(通过AuthScheme接口实现)。需要使用定制的认证方案,必须实现下面的步骤:
[1]实现AuthScheme接口。
[2]通过AuthPolicy.registerAuthScheme() 注册定制的AuthScheme
[3]将定制的AuthScheme加入到AuthPolicy.AUTH_SCHEME_PRIORITY中。
4.示例
4.1Basic authentication
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.UsernamePasswordCredentials;
import org.apache.commons.httpclient.auth.AuthScope;
import org.apache.commons.httpclient.methods.GetMethod;
 
/**
 * A simple example that uses HttpClient to perform a GET using Basic
 * Authentication. Can be run standalone without parameters.
 *
 * You need to have JSSE on your classpath for JDK prior to 1.4
 *
 * @author Michael Becke
 */
public class BasicAuthenticationExample {
 
    /**
     * Constructor for BasicAuthenticatonExample.
     */
    public BasicAuthenticationExample() {
        super();
    }
 
    public static void main(String[] args) throws Exception {
        HttpClient client = new HttpClient();
 
        // pass our credentials to HttpClient, they will only be used for
        // authenticating to servers with realm "realm" on the host
        // "www.verisign.com", to authenticate against
        // an arbitrary realm or host change the appropriate argument to null.
        client.getState().setCredentials(
            new AuthScope("www.verisign.com", 443, "realm"),
            new UsernamePasswordCredentials("username", "password")
        );
 
        // create a GET method that reads a file over HTTPS, we're assuming
        // that this file requires basic authentication using the realm above.
        GetMethod get = new GetMethod("https://www.verisign.com/products/index.html");
 
        // Tell the GET method to automatically handle authentication. The
        // method will use any appropriate credentials to handle basic
        // authentication requests.  Setting this value to false will cause
        // any request for authentication to return with a status of 401.
        // It will then be up to the client to handle the authentication.
        get.setDoAuthentication( true );
 
        try {         
            // execute the GET
            int status = client.executeMethod( get );
 
            // print the status and response
            System.out.println(status + "\n" + get.getResponseBodyAsString());
 
        } finally {
            // release any connection resources used by the method
            get.releaseConnection();
        }
    }
}
 
4.2 Alternate authentication
import java.util.ArrayList;
import java.util.List;
 
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.UsernamePasswordCredentials;
import org.apache.commons.httpclient.auth.AuthPolicy;
import org.apache.commons.httpclient.auth.AuthScope;
import org.apache.commons.httpclient.methods.GetMethod;
 
/**
 * <p>A simple example that uses alternate authentication scheme selection
 * if several authentication challenges are returned.
 * </p>
 *
 * <p>Per default HttpClient picks the authentication challenge in the following
 *  order of preference: NTLM, Digest, Basic. In certain cases it may be desirable to
 *  force the use of a weaker authentication scheme.
 * </p>
 *
 * @author Oleg Kalnichevski
 */
public class AlternateAuthenticationExample {
 
    /**
     * Constructor for BasicAuthenticatonExample.
     */
    public AlternateAuthenticationExample() {
        super();
    }
 
    public static void main(String[] args) throws Exception {
        HttpClient client = new HttpClient();
        client.getState().setCredentials(
            new AuthScope("myhost", 80, "myrealm"),
            new UsernamePasswordCredentials("username", "password"));
        // Suppose the site supports several authetication schemes: NTLM and Basic
        // Basic authetication is considered inherently insecure. Hence, NTLM authentication
        // is used per default
 
        // This is to make HttpClient pick the Basic authentication scheme over NTLM & Digest
        List<String> authPrefs = new ArrayList<String>(3);
        authPrefs.add(AuthPolicy.BASIC);
        authPrefs.add(AuthPolicy.NTLM);
        authPrefs.add(AuthPolicy.DIGEST);
        client.getParams().setParameter(AuthPolicy.AUTH_SCHEME_PRIORITY, authPrefs);
 
        GetMethod httpget = new GetMethod("http://myhost/protected/auth-required.html");
 
        try {
            int status = client.executeMethod(httpget);
            // print the status and response
            System.out.println(status);
            System.out.println(httpget.getStatusLine());
            System.out.println(httpget.getResponseBodyAsString());
        } finally {
            // release any connection resources used by the method
            httpget.releaseConnection();
        }           
    }
}
 
4.3 Custom authentication
import java.util.ArrayList;
import java.util.Collection;
 
import org.apache.commons.httpclient.Credentials;
import org.apache.commons.httpclient.HttpMethod;
import org.apache.commons.httpclient.auth.AuthPolicy;
import org.apache.commons.httpclient.auth.AuthScheme;
import org.apache.commons.httpclient.auth.AuthenticationException;
import org.apache.commons.httpclient.auth.MalformedChallengeException;
import org.apache.commons.httpclient.params.DefaultHttpParams;
import org.apache.commons.httpclient.params.HttpParams;
 
/**
 * A simple custom AuthScheme example.  The included auth scheme is meant
 * for demonstration purposes only.  It does not actually implement a usable
 * authentication method.
 */
public class CustomAuthenticationExample {
 
    @SuppressWarnings("unchecked")
    public static void main(String[] args) {
       
        // register the auth scheme
        AuthPolicy.registerAuthScheme(SecretAuthScheme.NAME, SecretAuthScheme.class);
 
        // include the scheme in the AuthPolicy.AUTH_SCHEME_PRIORITY preference,
        // this can be done on a per-client or per-method basis but we'll do it
        // globally for this example
        HttpParams params = DefaultHttpParams.getDefaultParams();       
        ArrayList<String> schemes = new ArrayList<String>();
        schemes.add(SecretAuthScheme.NAME);
        schemes.addAll( (Collection) params.getParameter(AuthPolicy.AUTH_SCHEME_PRIORITY));
        params.setParameter(AuthPolicy.AUTH_SCHEME_PRIORITY, schemes);
       
        // now that our scheme has been registered we can execute methods against
        // servers that require "Secret" authentication...
    }
   
    /**
     * A custom auth scheme that just uses "Open Sesame" as the authentication
     * string.
     */
    private class SecretAuthScheme implements AuthScheme {
 
        public static final String NAME = "Secret";
 
        public SecretAuthScheme() {
            // All auth schemes must have a no arg constructor.
        }
        public String authenticate(Credentials credentials, HttpMethod method)
            throws AuthenticationException {
            return "Open Sesame";
        }
        public String authenticate(Credentials credentials, String method,
                String uri) throws AuthenticationException {
            return "Open Sesame";
        }
        public String getID() {
            return NAME;
        }
        public String getParameter(String name) {
            // this scheme does not use parameters, see RFC2617Scheme for an example
            return null;
        }
        public String getRealm() {
            // this scheme does not use realms
            return null;
        }
        public String getSchemeName() {
            return NAME;
        }
        public boolean isConnectionBased() {
            return false;
        }
        public void processChallenge(String challenge)
                throws MalformedChallengeException {
            // Nothing to do here, this is not a challenge based
            // auth scheme.  See NTLMScheme for a good example.
        }
        public boolean isComplete() {
            // again we're not a challenge based scheme so this is always true
            return true;
        }
    }
}
 
4.4 Interactive authentication
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
import org.apache.commons.httpclient.Credentials;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.NTCredentials;
import org.apache.commons.httpclient.UsernamePasswordCredentials;
import org.apache.commons.httpclient.auth.AuthScheme;
import org.apache.commons.httpclient.auth.CredentialsNotAvailableException;
import org.apache.commons.httpclient.auth.CredentialsProvider;
import org.apache.commons.httpclient.auth.NTLMScheme;
import org.apache.commons.httpclient.auth.RFC2617Scheme;
import org.apache.commons.httpclient.methods.GetMethod;
 
/**
 * A simple example that uses HttpClient to perform interactive
 * authentication.
 *
 * @author Oleg Kalnichevski
 */
public class InteractiveAuthenticationExample {
 
    /**
     * Constructor for InteractiveAuthenticationExample.
     */
    public InteractiveAuthenticationExample() {
        super();
    }
 
    public static void main(String[] args) throws Exception {
 
        InteractiveAuthenticationExample demo = new InteractiveAuthenticationExample();
        demo.doDemo();
    }
   
    private void doDemo() throws IOException {
 
        HttpClient client = new HttpClient();
        client.getParams().setParameter(
            CredentialsProvider.PROVIDER, new ConsoleAuthPrompter());
        GetMethod httpget = new GetMethod("http://target-host/requires-auth.html");
        httpget.setDoAuthentication(true);
        try {
            // execute the GET
            int status = client.executeMethod(httpget);
            // print the status and response
            System.out.println(status);
            System.out.println(httpget.getStatusLine().toString());
            System.out.println(httpget.getResponseBodyAsString());
        } finally {
            // release any connection resources used by the method
            httpget.releaseConnection();
        }
    }
 
    public class ConsoleAuthPrompter implements CredentialsProvider {
 
        private BufferedReader in = null;
        public ConsoleAuthPrompter() {
            super();
            this.in = new BufferedReader(new InputStreamReader(System.in));
        }
       
        private String readConsole() throws IOException {
            return this.in.readLine();
        }
       
        public Credentials getCredentials(
            final AuthScheme authscheme,
            final String host,
            int port,
            boolean proxy)
            throws CredentialsNotAvailableException
        {
            if (authscheme == null) {
                return null;
            }
            try{
                if (authscheme instanceof NTLMScheme) {
                    System.out.println(host + ":" + port + " requires Windows authentication");
                    System.out.print("Enter domain: ");
                    String domain = readConsole();  
                    System.out.print("Enter username: ");
                    String user = readConsole();  
                    System.out.print("Enter password: ");
                    String password = readConsole();
                    return new NTCredentials(user, password, host, domain);   
                } else
                if (authscheme instanceof RFC2617Scheme) {
                    System.out.println(host + ":" + port + " requires authentication with the realm '"
                        + authscheme.getRealm() + "'");
                    System.out.print("Enter username: ");
                    String user = readConsole();  
                    System.out.print("Enter password: ");
                    String password = readConsole();
                    return new UsernamePasswordCredentials(user, password);   
                } else {
                    throw new CredentialsNotAvailableException("Unsupported authentication scheme: " +
                        authscheme.getSchemeName());
                }
            } catch (IOException e) {
                throw new CredentialsNotAvailableException(e.getMessage(), e);
            }
        }
    }
}
posted on 2008-02-17 23:14  浙林龙哥  阅读(11395)  评论(1编辑  收藏  举报