kafka自定义sasl验证插件

我们需要实现的类有以下几个：

LoginModule
Provider（client和server）
SaslClientFactory
SaslClient
SaslServerFactory
SaslServer

LoginModule

要先实现LoginModule。这个LoginModule中在客户端需要初始化SaslClientProvider，服务端需要初始化SaslServerProvider，为了方便，这里直接初始化两个Provider。如果客户端是给外部用户使用的话，为了安全，只需要初始化SaslClientProvider即可。

import javax.security.auth.Subject;
import javax.security.auth.callback.CallbackHandler;
import javax.security.auth.login.LoginException;
import javax.security.auth.spi.LoginModule;
import java.util.Map;

public class ABCLoginModule implements LoginModule {

    private static final String USERNAME = "username";
    private static final String PASSWORD = "password";

    static {
        ABCSaslClientProvider.initialize();
        ABCSaslServerProvider.initialize();
    }

    @Override
    public void initialize(Subject subject, CallbackHandler callbackHandler, Map<String, ?> sharedState, Map<String, ?> optiABC) {
        String accessKey = (String) optiABC.get(USERNAME);
        if (accessKey != null)
            subject.getPublicCredentials().add(accessKey);
        String secretKey = (String) optiABC.get(PASSWORD);
        if (secretKey != null)
            subject.getPrivateCredentials().add(secretKey);
    }

    @Override
    public boolean login() throws LoginException {
        return true;
    }

    @Override
    public boolean logout() throws LoginException {
        return true;
    }

    @Override
    public boolean commit() throws LoginException {
        return true;
    }

    @Override
    public boolean abort() throws LoginException {
        return false;
    }
}

Provider

而后我们分别实现两个Provider，Client和Server，代码太简单了就不多赘述了。

public class ABCSaslClientProvider extends Provider {

    private static final long serialVersionUID = 1L;


    protected ABCSaslClientProvider() {
        super("Simple SASL/ABC Client Provider", 1.0, "Simple SASL/ABC Client Provider for Kafka");
        super.put("SaslClientFactory." + ABCSaslClient.ABC_MECHANISM, ABCSaslClientFactory.class.getName());
    }

    public static void initialize() {
        Security.addProvider(new ABCSaslClientProvider());
    }
}

public class ABCSaslServerProvider extends Provider {

    private static final long serialVersionUID = 1L;

    protected ABCSaslServerProvider() {
        super("Simple SASL/ABC Server Provider", 1.0, "Simple SASL/ABC Server Provider for Kafka");
        super.put("SaslServerFactory." + ABCSaslServer.ABC_MECHANISM, ABCSaslServerFactory.class.getName());
    }

    public static void initialize() {
        Security.addProvider(new ABCSaslServerProvider());
    }
}

SaslClientFactory

SaslClientFactory中需要做的事有以下几个：

判断客户端的安全机制是否是ABC，只支持ABC的安全机制
从callbackHandler对象中取出用户密码
使用用户密码来构造出SaslClient

public class ABCSaslClientFactory implements SaslClientFactory{
    private static final String[] myMechs = new String[]{ABCSaslClient.ABC_MECHANISM};

    @Override
    public SaslClient createSaslClient(String[] mechanisms, String authorizationId, String protocol, String serverName,
            Map<String, ?> props, CallbackHandler cbh) throws SaslException {
        if (mechanisms.length != 1 || !mechanisms[0].equals(ABCSaslClient.ABC_MECHANISM)) {
            throw new SaslException("Mechanism ERROR, only support mechanism:" + ABCSaslClient.ABC_MECHANISM);
        }
        String mech = ABCSaslClient.ABC_MECHANISM;
        String username = null;
        String password = null;
        if(cbh == null) {
            throw new SaslException("Callback handler to get username/password required");
        } else {
            try {
                String namePrompt = mech + " authentication id: ";
                String passwordPrompt = mech + " password: ";
                NameCallback nameCallBack = new NameCallback(namePrompt);
                PasswordCallback passwdCallBack = new PasswordCallback(passwordPrompt, false);
                cbh.handle(new Callback[]{nameCallBack, passwdCallBack});
                char[] pwdBytes = passwdCallBack.getPassword();

                password = null;
                if(pwdBytes != null) {
                    password = new String(pwdBytes);
                    passwdCallBack.clearPassword();
                }

                username = nameCallBack.getName();
            } catch (IOException var11) {
                throw new SaslException("Cannot get password", var11);
            } catch (UnsupportedCallbackException var12) {
                throw new SaslException("Cannot get userid/password", var12);
            }
        }
        return new SaslClient(username,password);
    }

    @Override
    public String[] getMechanismNames(Map<String, ?> props) {
        return myMechs;
    }

}

SaslClient

SaslClient中需要实现以下几个功能：

保存username和password
保存Sasl客户端的校验状态（complete）
判断服务端的报文，是需要发送校验数据还是校验通过
构造加密报文

本例中的加密报文构造方法是

先构造出一个byte数组：格式为[0,username.getBytes(),0,password.getBytes()]
将构造出的byte数组加密（方法略），可以直接使用SHA-256不可逆加密，得到一个新的byte数组encrypt。
将用户名放在encrypt前面变成最终发送给服务端的报文，格式为[0, username.getBytes(), 0, encrypt]

public class ABCSaslClient implements SaslClient{
    public static final String ABC_MECHANISM="ABC";
    private String username;
    private String password;
    private boolean complete=false;
    private byte SEP=0;
    
    public ABCSaslClient(String username, String password) throws SaslException {
        if (username == null || password == null) {
            throw new SaslException("username/password must be specified");
        }

        this.username=username;
        this.password=password;
    }

    @Override
    public String getMechanismName() {
        return ABC_MECHANISM;
    }

    // hasInitialResponse()返回false表示INITIAL发送一个空包给服务端，返回true则表示会发送一个自定义的包，详见SaslClientAuthenticator.createSaslToken
    @Override
    public boolean hasInitialResponse() {
        return false;
    }

    @Override
    public byte[] evaluateChallenge(byte[] challenge) throws SaslException {
        if(this.complete) {
            throw new IllegalStateException("Authentication already completed");
        } else {
            //收到服务端返回的空包，表示通过校验，complete置为true并退出
            if (challenge.length == 0) {
                this.complete = true;
                return null;
            }
            /**
             * 如果收到的不是空包，表示可以构造校验报文了，这里有个小trick，可以在服务端生成随机数或时间戳，作为server token发送到客户端
             * 客户端可以将server token中的数据放到加密串中，增强报文的安全性。
             */

            byte[] data = ABCUtil.join(SEP, username.getBytes("UTF-8"),password.getBytes("UTF-8"));
            byte[] encrypt = ABCUtil.encrypt(data);

            byte[] response = ABCUtil.join(SEP, username.getBytes("UTF-8"), encrypt);
            return response;
        }
    }

    @Override
    public boolean isComplete() {
        return this.complete;
    }

    @Override
    public byte[] unwrap(byte[] incoming, int offset, int len) throws SaslException {
        if(this.complete) {
            throw new SaslException("PLAIN supports neither integrity nor privacy");
        } else {
            throw new IllegalStateException("PLAIN authentication not completed");
        }
    }

    @Override
    public byte[] wrap(byte[] outgoing, int offset, int len) throws SaslException {
        if(this.complete) {
            throw new SaslException("PLAIN supports neither integrity nor privacy");
        } else {
            throw new IllegalStateException("PLAIN authentication not completed");
        }
    }

    @Override
    public Object getNegotiatedProperty(String propName) {
        if(this.complete) {
            return propName.equals("javax.security.sasl.qop")?"auth":null;
        } else {
            throw new IllegalStateException("PLAIN authentication not completed");
        }
    }

    @Override
    public void dispose() throws SaslException {
        password=null;
    }

}

至此，完成客户端的部分。下面构造服务端的SaslServer。

SaslServerFactory

SaslServerFactory和Client很类似，需要实现的功能有：

判断client的安全机制是否是ABC
构造出SaslServer

代码比SaslClientFactory更简单一些

public class ABCSaslServerFactory implements SaslServerFactory{
    private static final String[] myMechs = new String[]{ABCSaslServer.ABC_MECHANISM};

    @Override
    public SaslServer createSaslServer(String mechanism, String protocol, String serverName, Map<String, ?> props,
            CallbackHandler cbh) throws SaslException {
        if (!mechanism.equals(ABCSaslClient.ABC_MECHANISM)) {
            throw new SaslException("Mechanism ERROR, only support mechanism:" + ABCSaslServer.ABC_MECHANISM);
        }       
        return new ABCSaslServer(cbh);
    }

    @Override
    public String[] getMechanismNames(Map<String, ?> props) {
        return myMechs;
    }
}

SaslServer

SaslServer需要处理两种报文，需要实现的功能和SaslClient类似：

记录校验状态（complete）
收到client端INITIAL阶段送的报文，处理并返回server token
收到client端的校验数据，校验信息
校验通过返回空包

这里有两个点需要注意，一个是complete一定要有，还有就是authorizationID一定要有，因为都是在Kafka中会被调用的方法。

public class ABCSaslServer implements SaslServer {
    public static final String ABC_MECHANISM = "ABC";
    private boolean complete = false;
    private String authID;

    public ABCSaslServer(CallbackHandler cbh) throws SaslException {

    }

    @Override
    public String getMechanismName() {
        return ABC_MECHANISM;
    }

    @Override
    public boolean isComplete() {
        return this.complete;
    }

    @Override
    public Object getNegotiatedProperty(String propName) {
        if (!complete)
            throw new IllegalStateException("Authentication exchange has not completed");
        return null;
    }

    @Override
    public byte[] unwrap(byte[] incoming, int offset, int len) throws SaslException {
        if (!complete)
            throw new IllegalStateException("Authentication exchange has not completed");
        return Arrays.copyOfRange(incoming, offset, offset + len);
    }

    @Override
    public byte[] wrap(byte[] outgoing, int offset, int len) throws SaslException {
        if (!complete)
            throw new IllegalStateException("Authentication exchange has not completed");
        return Arrays.copyOfRange(outgoing, offset, offset + len);
    }

    @Override
    public void dispose() throws SaslException {
    }

    @Override
    public byte[] evaluateResponse(byte[] response) throws SaslException {
        //收到客户端INITIAL阶段发送的空包，返回一个server token
        if (response.length == 0) {
            return "ABC by MisterCH".getBytes("UTF-8");
        } 
        String[] tokens;
        try {
            tokens = new String(response, "UTF-8").split("\u0000");
        } catch (UnsupportedEncodingException e) {
            throw new SaslException("UTF-8 encoding not supported", e);
        }
        if (tokens.length != 3)
            throw new SaslException("Invalid SASL/ABC response: expected 3 tokens, got " + tokens.length);
        // 从包中提取出用户名和加密串
        authID = tokens[0];
        String username = tokens[1];
        String encrypt = tokens[2];

        if (username.isEmpty()) {
            throw new SaslException("Authentication failed: username not specified");
        }
        if (authID.isEmpty())
            authID = username;
        // 在服务端拿到用户对应的密码
        String password = ABCUtil.getPassword(username);

        byte[] data = ABCUtil.join(SEP, username.getBytes("UTF-8"),password.getBytes("UTF-8"));
        byte[] expectedToken = ABCUtil.encrypt(data);
        
        // 比对服务端加密的串和客户端加密的串是否一致（对称加密），一致则通过校验
        if (!ABCUtils.isEqual(encrypt, expectedToken);) {
            throw new SaslException("Authentication failed: Invalid username or password");
        }
        complete = true;
        return new byte[0];
    }

    @Override
    public String getAuthorizationID() {
        return this.authID;
    }
}

配置修改

写完这些代码，打包成jar文件，而后放在kafka的libs目录下。服务端需要配置jaas文件作为jaas的入口，并修改server.properties。

KafkaServer{
  com.company.MisterCH.ABCLoginModule required
  username="test"
  password="test"
  user_ch="chsss";
};

修改Kafka的启动脚本不赘述，server.properties中需要修改几个地方

#broker内部通信使用PLAIN机制9092端口，外部通信使用SASL_PLAINTEXT的9093端口
listeners=PLAINTEXT://hostname:9093,SASL_PALINTEXT://hostname:9092
sasl.mechanism=ABC
security.protocol=SASL_PLAINTEXT

客户端可以不用配置jaas文件，直接在producer.properties或consumer.properties中修改如下配置

security.protocol=SASL_PLAINTEXT
sasl.mechanism=ABC
sasl.jaas.config=com.company.MisterCH.ABCLoginModule required \
   ch \
   chsss \;

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