linux 安全审计以及加固工具 lynis 使用介绍

清疚 2021-08-26 12:27 536阅读 0赞

# 0x00 概述 #

Lynis是一款Unix系统的安全审计以及加固工具，能够进行深层次的安全扫描，其目的是检测潜在的时间并对未来的系统加固提供建议。这款软件会扫描一般系统信息，脆弱软件包以及潜在的错误配置。

该软件面向系统admin，审计人员，安全官，安全专家。

特征：

1.  漏洞扫描
2.  系统加固
3.  入侵检测
4.  中心管理
5.  自定义行为规划
6.  报告
7.  安全面板
8.  持续监测
9.  技术支持

目标：

1.  自动安全审计
2.  符合性测试
3.  漏洞侦测

有助于：

1.  配置管理
2.  软件补丁管理
3.  系统加固
4.  渗透测试
5.  恶意软件扫描
6.  入侵检测

# 0x01 安装 #

详细查看其操作手册: [https://cisofy.com/documentation/lynis/get-started/][https_cisofy.com_documentation_lynis_get-started]

方式1 git下载使用

git clone https://github.com/CISOfy/lynis

方式2 直接下载tar包，解压使用

wget https://github.com/CISOfy/lynis/archive/2.7.5.tar.gz
    tar -zxvf 2.7.5.tar.gz

# 0x02 试用 #

进入lynis的目录，输入`./lynis`即可

我们一般试用`./lynis audit system`来进行对系统的全盘扫描，这种扫描方式会产生一系列人机交互，无法自动化扫描。

故我们在其后加上参数`-Q`即快速扫描，从而自动化扫描。

以下是常用的lynis的参数：

<table> 
 <thead> 
  <tr> 
   <th>Parameter</th> 
   <th>Abbreviated</th> 
   <th>Description</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>--auditor "Given name Surname"</td> 
   <td>&nbsp;</td> 
   <td>配发审计人员的名字</td> 
  </tr> 
  <tr> 
   <td>--checkall</td> 
   <td>-c</td> 
   <td>开始检查</td> 
  </tr> 
  <tr> 
   <td>--check-update</td> 
   <td>&nbsp;</td> 
   <td>更新</td> 
  </tr> 
  <tr> 
   <td>--cronjob</td> 
   <td>&nbsp;</td> 
   <td>计划任务 (includes -c -Q)</td> 
  </tr> 
  <tr> 
   <td>--help</td> 
   <td>-h</td> 
   <td>帮助</td> 
  </tr> 
  <tr> 
   <td>--manpage</td> 
   <td>&nbsp;</td> 
   <td>用户手册</td> 
  </tr> 
  <tr> 
   <td>--nocolors</td> 
   <td>&nbsp;</td> 
   <td>无配色</td> 
  </tr> 
  <tr> 
   <td>--pentest</td> 
   <td>&nbsp;</td> 
   <td>低权限渗透测试扫描</td> 
  </tr> 
  <tr> 
   <td>--quick</td> 
   <td>-Q</td> 
   <td>自动模式</td> 
  </tr> 
  <tr> 
   <td>--quiet</td> 
   <td>&nbsp;</td> 
   <td>静默且自动模式</td> 
  </tr> 
  <tr> 
   <td>--reverse-colors</td> 
   <td>&nbsp;</td> 
   <td>浅色背景配色模式</td> 
  </tr> 
  <tr> 
   <td>--version</td> 
   <td>-V</td> 
   <td>版本号</td> 
  </tr> 
 </tbody> 
</table>

如果要进行深层次的检查的话，可能需要让lynis处于root权限运行，那么我们只要

sudo cp -R /path/to/lynis /usr/local/lynis

即可将lynis置于root权限中，如此一来就可以进行深层次的检查了。

# 0x03 审计报告&日志 #

lynis将会进行深层次的审计，并将报告呈现在标准输出、日志文件以及审计报告文件中。

## 标准输出 ##

我们执行lynis时将会在屏幕上打印出本次审计的结果，测试的结果包括\[OK or WARNING\] \[Found or Not Found\] \[Value\]。如下图：

![format_png][]

![format_png 1][]

## 日志文件 ##

扫描完毕后我们会生成一个日志文件以及一个扫描报告。日志文件中对比标准输出，会有更多的信息，这些信息适用于更深层次的检查。

日志里会有事件操作的执行时间，测试失败或跳过的原因，内部测试的输出，对于配置选项不恰当该如何修改的建议，威胁指数。

我们对该文件进行输出，查看其中的告警（WARNING）以及建议（SUGGESTION）

# grep Warning /var/log/lynis.log
    [11:12:37] Warning: apt-get check returned a non successful exit code. [test:PKGS-7390] [details:M] [solution:-]
    [11:13:41] Warning: Couldn't find 2 responsive nameservers [test:NETW-2705] [details:L] [solution:-]
    [11:13:43] Warning: PHP option expose_php is possibly turned on, which can reveal useful information for attackers. [test:PHP-2372] [details:M] [solution:-]

# grep Suggestion /var/log/lynis.log
    [11:12:26] Suggestion: Set a password on GRUB bootloader to prevent altering boot configuration (e.g. boot in single user mode without password) [test:BOOT-5122] [details:-] [solution:-]
    [11:12:27] Suggestion: Install a PAM module for password strength testing like pam_cracklib or pam_passwdqc [test:AUTH-9262] [details:-] [solution:-]
    [11:12:27] Suggestion: Configure minimum password age in /etc/login.defs [test:AUTH-9286] [details:-] [solution:-]
    [11:12:27] Suggestion: Configure maximum password age in /etc/login.defs [test:AUTH-9286] [details:-] [solution:-]
    [11:12:28] Suggestion: Default umask in /etc/login.defs could be more strict like 027 [test:AUTH-9328] [details:-] [solution:-]
    [11:12:28] Suggestion: Default umask in /etc/init.d/rc could be more strict like 027 [test:AUTH-9328] [details:-] [solution:-]
    [11:12:28] Suggestion: To decrease the impact of a full /home file system, place /home on a separated partition [test:FILE-6310] [details:-] [solution:-]
    [11:12:28] Suggestion: To decrease the impact of a full /tmp file system, place /tmp on a separated partition [test:FILE-6310] [details:-] [solution:-]
    [11:12:28] Suggestion: To decrease the impact of a full /var file system, place /var on a separated partition [test:FILE-6310] [details:-] [solution:-]
    [11:12:28] Suggestion: Disable drivers like USB storage when not used, to prevent unauthorized storage or data theft [test:STRG-1840] [details:-] [solution:-]
    [11:12:28] Suggestion: Disable USB devices authorization, to prevent unauthorized storage or data theft [test:STRG-1840] [details:-] [solution:-]
    [11:12:36] Suggestion: Purge old/removed packages (5 found) with aptitude purge or dpkg --purge command. This will cleanup old configuration files, cron jobs and startup scripts. [test:PKGS-7346] [details:-] [solution:-]
    [11:12:36] Suggestion: Install debsums utility for the verification of packages with known good database. [test:PKGS-7370] [details:-] [solution:-]
    [11:12:37] Suggestion: Run apt-get to perform a manual package database consistency check. [test:PKGS-7390] [details:-] [solution:-]
    [11:13:40] Suggestion: Check if system is up-to-date, security updates test (apt-check) gives an unexpected result [test:PKGS-7392] [details:-] [solution:-]
    [11:13:40] Suggestion: Install package apt-show-versions for patch management purposes [test:PKGS-7394] [details:-] [solution:-]
    [11:13:41] Suggestion: Check your resolv.conf file and fill in a backup nameserver if possible [test:NETW-2705] [details:-] [solution:-]
    [11:13:41] Suggestion: Install ARP monitoring software like arpwatch [test:NETW-3032] [details:-] [solution:-]
    [11:13:41] Suggestion: Access to CUPS configuration could be more strict. [test:PRNT-2307] [details:-] [solution:-]
    [11:13:41] Suggestion: Configure a firewall/packet filter to filter incoming and outgoing traffic [test:FIRE-4590] [details:-] [solution:-]
    [11:13:42] Suggestion: Install Apache mod_evasive to guard webserver against DoS/brute force attempts [test:HTTP-6640] [details:-] [solution:-]
    [11:13:42] Suggestion: Install Apache mod_qos to guard webserver against Slowloris attacks [test:HTTP-6641] [details:-] [solution:-]
    [11:13:42] Suggestion: Install Apache mod_spamhaus to guard webserver against spammers [test:HTTP-6642] [details:-] [solution:-]
    [11:13:42] Suggestion: Install Apache modsecurity to guard webserver against web application attacks [test:HTTP-6643] [details:-] [solution:-]
    [11:13:43] Suggestion: Change the expose_php line to: expose_php = Off [test:PHP-2372] [details:-] [solution:-]
    [11:13:43] Suggestion: Change the allow_url_fopen line to: allow_url_fopen = Off, to disable downloads via PHP [test:PHP-2376] [details:-] [solution:-]
    [11:13:44] Suggestion: Check what deleted files are still in use and why. [test:LOGG-2190] [details:-] [solution:-]
    [11:13:44] Suggestion: Although inetd is not running, make sure no services are enabled in /etc/inetd.conf [test:INSE-8006] [details:-] [solution:-]
    [11:13:44] Suggestion: Add a legal banner to /etc/issue, to warn unauthorized users [test:BANN-7126] [details:-] [solution:-]
    [11:13:44] Suggestion: Add legal banner to /etc/issue.net, to warn unauthorized users [test:BANN-7130] [details:-] [solution:-]
    [11:13:44] Suggestion: Enable process accounting [test:ACCT-9622] [details:-] [solution:-]
    [11:13:44] Suggestion: Enable sysstat to collect accounting (no results) [test:ACCT-9626] [details:-] [solution:-]
    [11:13:44] Suggestion: Enable auditd to collect audit information [test:ACCT-9628] [details:-] [solution:-]
    [11:13:45] Suggestion: Determine if automation tools are present for system management [test:TOOL-5002] [details:-] [solution:-]
    [11:13:45] Suggestion: One or more sysctl values differ from the scan profile and could be tweaked [test:KRNL-6000] [details:-] [solution:-]
    [11:13:45] Suggestion: Harden compilers like restricting access to root user only [test:HRDN-7222] [details:-] [solution:-]

## 审计报告 ##

执行审计程序之后，lynis会对其发现进行收集并获得其他数据点，数据会被存储在报告文件中。不过这个文件读起来比较吃力，采用的是 数据名=值 的方式，要是一个数据有多个值，则在其后加个`[]`。如下图：

![format_png 2][]

若是使用lynis企业版，可以产生更多的报告格式。

# 0x04 配置文件 #

我们可以针对不同的操作系统、系统定位以及安全等级定制不同的配置文件。如果不通过`--profile`来指定配置文件的话，就会使用默认的配置文件`default.prf`。我们可以通过修改这个默认配置文件来满足我们的需求。

# 0x05 插件 #

正常lynis控制器进行独立测试并共享输出时，插件会获取信息。随后信息会被收集和处理，随后安全智能能够适用于数据收集并与中心节点相关联。

lynis能够使用插件模块化支持拓展其功能。

**阶段1**：

阶段1是插件初始化，该插件能hook进已有的测试，收集信息。

**阶段2**：

测试结束后，插件能够获取最后一次机会去完成其工作。插件也能独立使用，仅仅在阶段1执行。

**启用插件**

在profile里启用插件，`plugin=<plugin_name>`

# 0x06 Lynis企业版 #

需要购买Key。用了企业版之后可以拥有其他功能了，如插件功能，中心系统功能，定制报告功能以及安全面板功能。其用户界面是基于web的。

# 0x07 优劣 #

## 优势 ##

1.  开源
2.  多平台
3.  能够产生告警和建议
4.  整合大量审计模块，对操作系统进行多样化审计
5.  支持模块，可以进行自定义扫描
6.  企业版有web界面

## 劣势 ##

1.  每个审计项都不深入，需要具体的扩展
2.  许多功能需要使用企业版，收费暂时无法体验

[https_cisofy.com_documentation_lynis_get-started]: https://cisofy.com/documentation/lynis/get-started/
[format_png]: /images/20210728/05e28c16039248c6bef5fd29df4e67e6.png
[format_png 1]: /images/20210728/2297795c020a4c118af979ebff5df59b.png
[format_png 2]: /images/20210728/bdb3e64bdde14d108d1e928b19d84f57.png