针对本地 SASL 的 Java 身份验证

Question

我正在尝试制作一个 java 类，以便根据本地 SASL 对用户进行身份验证。我的 saslauthd 配置是这样的:

$ cat /etc/sysconfig/saslauthd
# Directory in which to place saslauthd's listening socket, pid file, and so
# on.  This directory must already exist.
SOCKETDIR=/run/saslauthd

# Mechanism to use when checking passwords.  Run "saslauthd -v" to get a list
# of which mechanism your installation was compiled with the ablity to use.
MECH=pam

# Additional flags to pass to saslauthd on the command line.  See saslauthd(8)
# for the list of accepted flags.
FLAGS="-t 1"

基本上，它会重定向针对 PAM 的身份验证。所以，如果我正在做这样的测试。

testsaslauthd -s login -u <user> -p <password>
0: OK "Success."

一切正常。

我现在想通过 Java 来管理这个机制，所以我编译了这样的东西:

import java.util.Arrays;
import java.util.List;
import java.io.*;

public class PamAuthenticator {

    public static void main(String args[]) {

        String s = null;

        try {

            Process p = Runtime.getRuntime().exec("testsaslauthd -s "+args[2]+" -u "+args[0]+" -p "+args[1]);

            BufferedReader stdInput = new BufferedReader(new
                InputStreamReader(p.getInputStream()));

            BufferedReader stdError = new BufferedReader(new
                InputStreamReader(p.getErrorStream()));

            while ((s = stdInput.readLine()) != null) {
                System.out.println(s);
            }

            while ((s = stdError.readLine()) != null) {
                System.out.println(s);
            }

            System.exit(0);
        }
        catch (IOException e) {
            System.out.println("Exception: ");
            e.printStackTrace();
            System.exit(-1);
        }
    }

}

这是正常工作的:

$ java -cp .:* PamAuthenticator <user> <password> login
0: OK "Success."

我的问题是我不想执行 testsaslauthd 命令，因为这只是一个测试命令。为了使用 Java 再次尝试 SASL 身份验证，我可以做一些更好更聪明的事情吗？

Answer 1

你是在正确的轨道上，不要使用上面的代码。除了作为测试解决方案外，它还会引入严重的安全问题:command injection .

从 Java 1.6 开始，有一个名为 SaslClient 的接口(interface).这正是您所需要的。一个example在 JDK8 上它的版本:

import javax.security.auth.callback.Callback;
import javax.security.auth.callback.NameCallback;
import javax.security.auth.callback.PasswordCallback;
import javax.security.auth.callback.UnsupportedCallbackException;
import javax.security.sasl.Sasl;
import javax.security.sasl.SaslClient;
import javax.security.sasl.SaslException;
import java.util.HashMap;

public class Test {
    public static void main(String[] args) throws SaslException {
        String userName = "username";
        String password = "password";
        SaslClient saslClient = Sasl.createSaslClient(new String[]{"PLAIN"},
                null, null, null, new HashMap<>(), callbacks -> {
                    for (final Callback callback : callbacks) {
                        if (callback instanceof NameCallback) {
                            NameCallback.class.cast(callback).setName(userName);
                            continue;
                        }
                        if (callback instanceof PasswordCallback) {
                            PasswordCallback.class.cast(callback).setPassword(password.toCharArray());
                            continue;
                        }
                        throw new UnsupportedCallbackException(callback);
                    }
                });
    }
}

当然你应该改变用户名和密码的来源。