如何保护 MySQL 用户名和密码不被反编译? [英] How can I protect MySQL username and password from decompiling?

问题描述

Java .class 文件可以很容易地反编译.如果必须使用代码中的登录数据，如何保护我的数据库?

Java .class files can be decompiled fairly easily. How can I protect my database if I have to use the login data in the code?

推荐答案

切勿将密码硬编码到您的代码中.这是最近在 Top 25 最危险的编程错误:

Never hard-code passwords into your code. This was brought up recently in the Top 25 Most Dangerous Programming Mistakes:

硬编码一个秘密账户和进入您的软件的密码是极其方便——对于熟练的逆向工程师.如果密码是你所有的软件都一样，然后每个客户都变得脆弱当那个密码不可避免地变成已知.因为它是硬编码的，修复起来非常痛苦.

Hard-coding a secret account and password into your software is extremely convenient -- for skilled reverse engineers. If the password is the same across all your software, then every customer becomes vulnerable when that password inevitably becomes known. And because it's hard-coded, it's a huge pain to fix.

您应该将配置信息(包括密码)存储在应用程序启动时读取的单独文件中.这是防止密码因反编译而泄露的唯一真正方法(一开始永远不要将其编译为二进制文件).

You should store configuration information, including passwords, in a separate file that the application reads when it starts. That is the only real way to prevent the password from leaking as a result of decompilation (never compile it into the binary to begin with).

有关此常见错误的更多信息，您可以阅读 CWE-259 文章.这篇文章包含更详尽的定义、示例以及有关该问题的许多其他信息.

For more information about this common mistake, you can read the CWE-259 article. The article contains a more thorough definition, examples, and lots of other information about the problem.

在 Java 中，最简单的方法之一是使用 Preferences 类.它旨在存储各种程序设置，其中一些可能包括用户名和密码.

In Java, one of the easiest ways to do this is to use the Preferences class. It is designed to store all sorts of program settings, some of which could include a username and password.

import java.util.prefs.Preferences;

public class DemoApplication {
  Preferences preferences = 
      Preferences.userNodeForPackage(DemoApplication.class);

  public void setCredentials(String username, String password) {
    preferences.put("db_username", username);
    preferences.put("db_password", password);
  }

  public String getUsername() {
    return preferences.get("db_username", null);
  }

  public String getPassword() {
    return preferences.get("db_password", null);
  }

  // your code here
}

在上面的代码中，您可以在显示用户名和密码的对话框询问后调用 setCredentials 方法.当您需要连接到数据库时，您只需使用 getUsername 和 getPassword 方法来检索存储的值.登录凭据不会硬编码到您的二进制文件中，因此反编译不会带来安全风险.

In the above code, you could call the setCredentials method after showing a dialog askign for the username and password. When you need to connect to the database, you can just use the getUsername and getPassword methods to retrieve the stored values. The login credentials will not be hard-coded into your binaries, so decompilation will not pose a security risk.

重要说明: 首选项文件只是纯文本 XML 文件.确保采取适当的步骤来防止未经授权的用户查看原始文件(UNIX 权限、Windows 权限等).至少在 Linux 中，这不是问题，因为调用 Preferences.userNodeForPackage 将在当前用户的主目录中创建 XML 文件，无论如何其他用户都无法读取该文件.在 Windows 中，情况可能有所不同.

Important Note: The preference files are just plain text XML files. Make sure you take appropriate steps to prevent unauthorized users from viewing the raw files (UNIX permissions, Windows permissions, et cetera). In Linux, at least, this isn't a problem, because calling Preferences.userNodeForPackage will create the XML file in the current user's home directory, which is non-readable by other users anyway. In Windows, the situation might be different.

更重要的注意事项:在这个答案和其他人的评论中已经有很多关于这种情况的正确架构的讨论.最初的问题并没有真正提到应用程序的使用上下文，所以我将谈谈我能想到的两种情况.第一种情况是使用程序的人已经知道(并被授权知道)数据库凭据.第二种情况是，您(开发人员)试图对使用该程序的人保密数据库凭据.

More Important Notes: There has been a lot of discussion in the comments of this answer and others about what the correct architecture is for this situation. The original question doesn't really mention the context in which the application is being used, so I will talk about the two situations I can think of. The first is the case in which the person using the program already knows (and is authorized to know) the database credentials. The second is the case in which you, the developer, are trying to keep the database credentials secret from the person using the program.

第一种情况:用户被授权知道数据库登录凭据

在这种情况下，我上面提到的解决方案将起作用.Java Preference 类将以纯文本形式存储用户名和密码，但首选项文件只能由授权用户读取.用户可以简单地打开首选项 XML 文件并读取登录凭据，但这不会带来安全风险，因为用户一开始就知道凭据.

In this case, the solution I mentioned above will work. The Java Preference class will stored the username and password in plain text, but the preferences file will only be readable by the authorized user. The user can simply open the preferences XML file and read the login credentials, but that is not a security risk because the user knew the credentials to begin with.

第二种情况:试图对用户隐藏登录凭据

这是更复杂的情况:用户不应该知道登录凭据，但仍需要访问数据库.在这种情况下，运行应用程序的用户可以直接访问数据库，这意味着程序需要提前知道登录凭据.我上面提到的解决方案不适用于这种情况.您可以将数据库登录凭据存储在首选项文件中，但用户将能够读取该文件，因为他们将是所有者.其实这个case真的没有什么好办法安全使用.

This is the more complicated case: the user should not know the login credentials but still needs access to the database. In this case, the user running the application has direct access to the database, which means the program needs to know the login credentials ahead of time. The solution I mentioned above is not appropriate for this case. You can store the database login credentials in a preferences file, but he user will be able to read that file, since they will be the owner. In fact, there is really no good way to use this case in a secure way.

正确案例:使用多层架构

正确的做法是在您的数据库服务器和客户端应用程序之间设置一个中间层，用于验证单个用户并允许执行一组有限的操作.每个用户都有自己的登录凭据，但不是数据库服务器的登录凭据.凭据将允许访问中间层(业务逻辑层)，并且每个用户都不同.

The correct way to do it is to have a middle layer, in between your database server and your client application, that authenticates individual users and allows a limited set of operations to be performed. Each user would have their own login credentials, but not for the database server. The credentials would allow access to the middle layer (the business logic tier) and would be different for each user.

每个用户都有自己的用户名和密码，它们可以本地存储在首选项文件中，没有任何安全风险.这称为三层架构(层是您的数据库服务器，业务逻辑服务器和客户端应用程序).它更复杂，但确实是做这种事情的最安全的方式.

Every user would have their own username and password, which could be stored locally in a preferences file without any security risk. This is called a three-tier architecture (the tiers being your database server, business logic server, and client application). It is more complex, but it really is the most secure way to do this sort of thing.

基本的操作顺序是:

1. 客户端使用用户的个人用户名/密码向业务逻辑层进行身份验证.用户名和密码为用户所知，与数据库登录凭据没有任何关系.
2. 如果身份验证成功，客户端会向业务逻辑层发出请求，要求从数据库获取一些信息.例如，产品库存.注意客户端的请求不是SQL查询；它是一个远程过程调用，例如 getInventoryList.
3. 业务逻辑层连接到数据库并检索请求的信息.业务逻辑层负责根据用户的请求形成安全的SQL查询.应清理 SQL 查询的任何参数，以防止 SQL 注入攻击.
4. 业务逻辑层将清单列表发送回客户端应用程序.
5. 客户端向用户显示库存清单.

请注意，在整个过程中，客户端应用程序从不直接连接到数据库.业务逻辑层接收来自经过身份验证的用户的请求，处理客户对库存清单的请求，然后才执行 SQL 查询.

Note that in the entire process, the client application never connects directly to the database. The business logic tier receives a request from an authenticated user, processes the client's request for an inventory list, and only then executes a SQL query.

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