漏洞扫描 -- 编写Nmap脚本

漏洞扫描 --
编写Nmap脚本

2006年12月份，Nmap4.21 ALPHA1版加入脚本引擎，并将其作为主线代码的一部分。NSE脚本库如今已经有400多个脚本，覆盖了各种不同的网络机制(从SMB漏洞检测到Stuxnet探测，及中间的一些内容)。NSE的强大，依赖它强大的功能库，这些库可以非常容易的与主流的网络服务和协议，进行交互。

挑战

我们经常会扫描网络环境中的主机是否存在某种新漏洞，而扫描器引擎中没有新漏洞的检测方法，这时候我们可能需要自己开发扫描工具。

你可能已经熟悉了某种脚本(例如:Python，Perl，etc.)，并可以快速写出检测漏洞的程序。但是，如果面临许多主机时，
针对两三个主机的检测方法，可能并不奏效。

Nmap 解救你 !使用内嵌的Lua语言和强大的集合库，你可以结合nmap高效的主机和端口扫描引擎，开发出针对多数主机的检测方法。

实现

Nmap 引擎脚本，由Lua编程语言、NmapAPI、系列强大的NSE库实现。为了达到本文的目的，现假设某个应用中存在一个叫ArcticFission漏洞。与许多其他的web应用程序类似，可以通过探测特定的文件，假设这个文件就是/arcticfission.html，用正则表达式提取文件内容中的版本号，与有漏洞的值进行对比.
听起来好像很简单，让我们开始吧 !

框架代码

基于传统的语言标准，我们写一个脚本，作用:遇到开放的HTTP端口，就返回”Hello World”。

-- The Head Section --

-- The Rule Section --

portrule = function(host, port)

return port.protocol == "tcp" and port.number == 80 and port.state == "open"

end

-- The Action Section --

action = function(host, port)

return "Hello world !"

end

注意:以--起始的行表示注释。

NSE脚本主要由三部分组成:

The Head Section

该部分包含一些元数据，主要描述脚本的功能，作者，影响力，类别及其他。

The Rule Section

该部分定义脚本执行的必要条件。至少包含下面列表中的一个函数:

portrule

hostrule

prerule

postrule

此案例中，重点介绍portrule。portrule能够在执行操作前，检查host和port属性。portrule会利用nmap的API检查TCP80端口。

The Action Section

该部分定义脚本逻辑。此处案例中，检测到开放80端口，则打印“HelloWorld”。脚本的输出内容，会在nmap执行期间显示出来。

[email protected]:/home/offensive/nmap_nse# nmap -sS -p 22,80,443 --script /home/offensive/nmap_nse/http-vuln-check.nse www.exploit-db.com

Starting Nmap 6.47 ( http://nmap.org ) at 2014-09-29 10:39 EDT

Nmap scan report for www.exploit-db.com (192.99.12.218)

Host is up (0.47s latency).

Other addresses for www.exploit-db.com (not scanned): 198.58.102.135

rDNS record for 192.99.12.218: cloudproxy71.sucuri.net

PORT STATE SERVICE

22/tcp filtered ssh

80/tcp open http

|_http-vuln-check: Hello world !

443/tcp open https

调用脚本库

优秀的库集合，促使其变的强大。例如，可调用现有库中的函数，针对http端口创建portrule。此处用到了shortport.

local shortport = require "shortport"

-- The Rule Section --

portrule = shortport.http

-- The Action Section --

action = function(host, port)

return "Hello world!"

end

同样的扫描，产生了不同的结果

[email protected]:/home/offensive/nmap_nse# nmap -sS -p 22,80,443 --script /home/offensive/nmap_nse/http-vuln-check_shortport.nse www.exploit-db.com

Starting Nmap 6.47 ( http://nmap.org ) at 2014-09-29 10:36 EDT

Nmap scan report for www.exploit-db.com (192.99.12.218)

Host is up (0.46s latency).

Other addresses for www.exploit-db.com (not scanned): 198.58.102.135

rDNS record for 192.99.12.218: cloudproxy71.sucuri.net

PORT STATE SERVICE

22/tcp filtered ssh

80/tcp open http

|_http-vuln-check_shortport: Hello world!

443/tcp open https

|_http-vuln-check_shortport: Hello world!

Nmap done: 1 IP address (1 host up) scanned in 6.32 seconds

该脚本对443执行了类似80端口的操作。主要是因为shortport.http表示类似HTTP的端口(80,443,631,7080,8080,8088,5800,3872,8180,8000)，也就是说，nmap会探测服务http、https、ipp、http-alt、vnc-http、oem-agent、soap、http-proxy非标准端口，如果想要获取更多的信息，请查阅shortport的文档.

服务探测

让我们把注意力放到action
部分的逻辑上。上述漏洞的检测，首先需要探测页面”/arcticfission.html”

local shortport = require "shortport"

local http = require "http"

-- The Rule Section --

portrule = shortport.http

-- The Action Section --

action = function(host, port)

local uri = "/arcticfission.html"

local response = http.get(host, port, uri)

return response.status

end

上述代码用到了库http处理web页面，

[email protected]:/home/offensive/nmap_nse# nmap -sS -p 22,80,443 --script /home/offensive/nmap_nse/http-vuln-check_shortport2.nse www.exploit-db.com

Starting Nmap 6.47 ( http://nmap.org ) at 2014-09-29 11:16 EDT

Nmap scan report for www.exploit-db.com (192.99.12.218)

Host is up (0.48s latency).

Other addresses for www.exploit-db.com (not scanned): 198.58.102.135

rDNS record for 192.99.12.218: cloudproxy71.sucuri.net

PORT STATE SERVICE

22/tcp filtered ssh

80/tcp open http

|_http-vuln-check_shortport2: 403

443/tcp open https

|_http-vuln-check_shortport2: 400

上述输出表明，两个服务器端口不存在对应页面”arcticfission.html”，注意‘http‘
库会自动在http与https端口切换，因此你不需要考虑去实现TLS/SSL。

如果只想输出存在该页面的web应用，可以如下操作:

local shortport = require "shortport"

local http = require "http"

-- The Rule Section --

portrule = shortport.http

-- The Action Section --

action = function(host, port)

local uri = "/arcticfission.html"

local response = http.get(host, port, uri)

if (response.status == 200) then

return response.body

end

上述代码，返回状态码为200的页面内容。

注意:如果没有数据返回或返回数据为空，将导致无输出显示.

漏洞探测

许多时候，可以通过一个简单的服务版本号，探测漏洞。这种情况，假象的服务器会返回一个包含版本号的标识。

local shortport = require "shortport"

local http = require "http"

local string = require "string"

-- The Rule Section --

portrule = shortport.http

-- The Action Section --

action = function(host, port)

local uri = "/arcticfission.html"

local response = http.get(host, port, uri)

if ( response.status == 200 ) then

local title = string.match(response.body, "<[Tt][Ii][Tt][Ll][Ee][^>]*>ArcticFission ([^<]*)</[Tt][Ii][Tt][Ll][Ee]>")

return title

end

上述代码，用到了
string库，以便获取页面头。

[email protected]:~/nmap_nse$ nmap -p 80,443 --script /home/offensive/nmap_nse/http-vuln-check_shortport4.nse 192.168.1.105

Starting Nmap 6.47 ( http://nmap.org ) at 2014-09-30 03:49 EDT

Nmap scan report for localhost (192.168.1.105)

Host is up (0.00053s latency).

PORT STATE SERVICE

80/tcp open http

|_http-vuln-check_shortport4: 1.0

443/tcp closed https

Nmap done: 1 IP address (1 host up) scanned in 0.07 seconds

正如上面描述的那样，现在需要将获取的值与漏洞值比较，确认是否存在漏洞。

local shortport = require "shortport"

local http = require "http"

local string = require "string"

-- The Rule Section --

portrule = shortport.http

-- The Action Section --

action = function(host, port)

local uri = "/arcticfission.html"

local response = http.get(host, port, uri)

if ( response.status == 200 ) then

local title = string.match(response.body, "<[Tt][Ii][Tt][Ll][Ee][^>]*>ArcticFission ([^<]*)</[Tt][Ii][Tt][Ll][Ee]>")

if ( title == "1.0" ) then

return "Vnlnerable"

else

return "Not Vulnerable"

end

测试结果如下:

[email protected]:~/nmap_nse$ nmap -p 80,443 --script /home/offensive/nmap_nse/http-vuln-check_shortport5.nse 192.168.1.105

Starting Nmap 6.47 ( http://nmap.org ) at 2014-09-30 04:05 EDT

Nmap scan report for localhost (192.168.1.105)

Host is up (0.00045s latency).

PORT STATE SERVICE

80/tcp open http

|_http-vuln-check_shortport5: Vnlnerable

443/tcp closed https

版本检测的另一种方法，生成Hash与有漏洞的页面对比。为了实现此效果，此处调用了openssl库。

local shortport = require "shortport"

local http = require "http"

local stdnse = require "stdnse"

local openssl = require "openssl"

-- The Rule Section --

portrule = shortport.http

-- The Action Section --

action = function(host, port)

local uri = "/arcticfission.html"

local response = http.get(host, port, uri)

if (response.status == 200) then

local vulnsha1 = "398ffad678f17a4f16ccd00b1914ca986d0b9258"

local sha1 = string.lower(stdnse.tohex(openssl.sha1(response.body)))

if ( sha1 == vulnsha1 ) then

return "Vulnerable"

else

return "Not Vulnerable"

end

添加隐藏属性

使用第三方的库时，测试脚本的执行流程很重要。

[email protected]:~/nmap_nse$ nmap -p 80,443 --script /home/offensive/nmap_nse/http-vuln-check_openssl.nse --script-trace 192.168.1.105

Starting Nmap 6.47 ( http://nmap.org ) at 2014-09-30 05:38 EDT

NSOCK INFO [0.0600s] nsi_new2(): nsi_new (IOD #1)

NSOCK INFO [0.0610s] nsock_connect_tcp(): TCP connection requested to 192.168.1.105:80 (IOD #1) EID 8

NSOCK INFO [0.0610s] nsock_trace_handler_callback(): Callback: CONNECT SUCCESS for EID 8 [192.168.1.105:80]

NSE: TCP 192.168.1.106:59791 > 192.168.1.105:80 | CONNECT

NSE: TCP 192.168.1.106:59791 > 192.168.1.105:80 | 00000000: 47 45 54 20 2f 61 72 63 74 69 63 66 69 73 73 69 GET /arcticfissi

00000010: 6f 6e 2e 68 74 6d 6c 20 48 54 54 50 2f 31 2e 31 on.html HTTP/1.1

00000020: 0d 0a 48 6f 73 74 3a 20 6c 6f 63 61 6c 68 6f 73 Host: localhos

00000030: 74 0d 0a 43 6f 6e 6e 65 63 74 69 6f 6e 3a 20 63 t Connection: c

00000040: 6c 6f 73 65 0d 0a 55 73 65 72 2d 41 67 65 6e 74 lose User-Agent

00000050: 3a 20 4d 6f 7a 69 6c 6c 61 2f 35 2e 30 20 28 63 : Mozilla/5.0 (c

00000060: 6f 6d 70 61 74 69 62 6c 65 3b 20 4e 6d 61 70 20 ompatible; Nmap

00000070: 53 63 72 69 70 74 69 6e 67 20 45 6e 67 69 6e 65 Scripting Engine

00000080: 3b 20 68 74 74 70 3a 2f 2f 6e 6d 61 70 2e 6f 72 ; http://nmap.or

00000090: 67 2f 62 6f 6f 6b 2f 6e 73 65 2e 68 74 6d 6c 29 g/book/nse.html)

000000a0: 0d 0a 0d 0a

NSOCK INFO [0.0620s] nsock_trace_handler_callback(): Callback: WRITE SUCCESS for EID 19 [192.168.1.105:80]

NSE: TCP 192.168.1.106:59791 > 192.168.1.105:80 | SEND

NSOCK INFO [0.0620s] nsock_read(): Read request from IOD #1 [192.168.1.105:80] (timeout: 8000ms) EID 26

NSOCK INFO [0.0640s] nsock_trace_handler_callback(): Callback: READ SUCCESS for EID 26 [192.168.1.105:80] (392 bytes)

NSE: TCP 192.168.1.106:59791 < 192.168.1.105:80 | 00000000: 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d HTTP/1.1 200 OK

00000010: 0a 44 61 74 65 3a 20 54 75 65 2c 20 33 30 20 53 Date: Tue, 30 S

00000020: 65 70 20 32 30 31 34 20 30 39 3a 33 38 3a 34 39 ep 2014 09:38:49

00000030: 20 47 4d 54 0d 0a 53 65 72 76 65 72 3a 20 41 70 GMT Server: Ap

00000040: 61 63 68 65 2f 32 2e 32 2e 32 32 20 28 44 65 62 ache/2.2.22 (Deb

00000050: 69 61 6e 29 0d 0a 4c 61 73 74 2d 4d 6f 64 69 66 ian) Last-Modif

00000060: 69 65 64 3a 20 54 75 65 2c 20 33 30 20 53 65 70 ied: Tue, 30 Sep

00000070: 20 32 30 31 34 20 30 37 3a 33 30 3a 33 33 20 47 2014 07:30:33 G

00000080: 4d 54 0d 0a 45 54 61 67 3a 20 22 65 31 31 38 31 MT ETag: "e1181

00000090: 2d 37 34 2d 35 30 34 34 33 35 62 64 38 36 62 30 -74-504435bd86b0

000000a0: 32 22 0d 0a 41 63 63 65 70 74 2d 52 61 6e 67 65 2" Accept-Range

000000b0: 73 3a 20 62 79 74 65 73 0d 0a 43 6f 6e 74 65 6e s: bytes Conten

000000c0: 74 2d 4c 65 6e 67 74 68 3a 20 31 31 36 0d 0a 56 t-Length: 116 V

000000d0: 61 72 79 3a 20 41 63 63 65 70 74 2d 45 6e 63 6f ary: Accept-Enco

000000e0: 64 69 6e 67 0d 0a 43 6f 6e 6e 65 63 74 69 6f 6e ding Connection

000000f0: 3a 20 63 6c 6f 73 65 0d 0a 43 6f 6e 74 65 6e 74 : close Content

00000100: 2d 54 79 70 65 3a 20 74 65 78 74 2f 68 74 6d 6c -Type: text/html

00000110: 0d 0a 0d 0a 3c 68 74 6d 6c 3e 0a 3c 68 65 61 64 <html> <head

00000120: 3e 0a 3c 74 69 74 6c 65 3e 41 72 63 74 69 63 46 > <title>ArcticF

00000130: 69 73 73 69 6f 6e 20 31 2e 30 3c 2f 74 69 74 6c ission 1.0</titl

00000140: 65 3e 0a 3c 2f 68 65 61 64 3e 0a 3c 62 6f 64 79 e> </head> <body

00000150: 3e 0a 3c 68 31 3e 57 65 6c 63 6f 6d 65 20 74 6f > <h1>Welcome to

00000160: 20 41 72 63 74 69 63 46 69 73 73 69 6f 6e 20 31 ArcticFission 1

00000170: 2e 30 3c 2f 68 31 3e 0a 3c 2f 62 6f 64 79 3e 0a .0</h1> </body>

00000180: 3c 2f 68 74 6d 6c 3e 0a </html>

NSE: TCP 192.168.1.106:59791 > 192.168.1.105:80 | CLOSE

NSOCK INFO [0.0640s] nsi_delete(): nsi_delete (IOD #1)

Nmap scan report for localhost (192.168.1.105)

Host is up (0.00064s latency).

PORT STATE SERVICE

80/tcp open http

|_http-vuln-check_openssl: Vulnerable

443/tcp closed https

Nmap done: 1 IP address (1 host up) scanned in 0.07 seconds

从上面的跟踪看，NSE的‘http‘库使用的默认User-Agent是“Mozilla/5.0(compatible;
Nmap Scripting Engine;http://nmap.org/book/nse.html)”. 可能由于某些安全原因，你需要更改user-agent，可使用下面方法.

[email protected]:~/nmap_nse$ nmap -p 80,443 --script /home/offensive/nmap_nse/http-vuln-check_openssl.nse --script-args="http.useragent=‘Mozilla/5.0 (compatible [[email protected]])‘" --script-trace 192.168.1.105

Starting Nmap 6.47 ( http://nmap.org ) at 2014-09-30 06:08 EDT

NSOCK INFO [0.2590s] nsi_new2(): nsi_new (IOD #1)

NSOCK INFO [0.2600s] nsock_connect_tcp(): TCP connection requested to 192.168.1.105:80 (IOD #1) EID 8

NSOCK INFO [0.2610s] nsock_trace_handler_callback(): Callback: CONNECT SUCCESS for EID 8 [192.168.1.105:80]

NSE: TCP 192.168.1.106:59923 > 192.168.1.105:80 | CONNECT

NSE: TCP 192.168.1.106:59923 > 192.168.1.105:80 | 00000000: 47 45 54 20 2f 61 72 63 74 69 63 66 69 73 73 69 GET /arcticfissi

00000010: 6f 6e 2e 68 74 6d 6c 20 48 54 54 50 2f 31 2e 31 on.html HTTP/1.1

00000020: 0d 0a 48 6f 73 74 3a 20 31 39 32 2e 31 36 38 2e Host: 192.168.

00000030: 31 2e 31 30 35 0d 0a 55 73 65 72 2d 41 67 65 6e 1.105 User-Agen

00000040: 74 3a 20 4d 6f 7a 69 6c 6c 61 2f 35 2e 30 20 28 t: Mozilla/5.0 (

00000050: 63 6f 6d 70 61 74 69 62 6c 65 20 5b 6f 66 66 65 compatible [offe

00000060: 6e 73 69 76 65 40 73 65 63 75 72 69 74 79 5d 29 [email protected]])

00000070: 0d 0a 43 6f 6e 6e 65 63 74 69 6f 6e 3a 20 63 6c Connection: cl

00000080: 6f 73 65 0d 0a 0d 0a ose

NSOCK INFO [0.2610s] nsock_trace_handler_callback(): Callback: WRITE SUCCESS for EID 19 [192.168.1.105:80]

NSE: TCP 192.168.1.106:59923 > 192.168.1.105:80 | SEND

NSOCK INFO [0.2610s] nsock_read(): Read request from IOD #1 [192.168.1.105:80] (timeout: 8000ms) EID 26

NSOCK INFO [0.2640s] nsock_trace_handler_callback(): Callback: READ SUCCESS for EID 26 [192.168.1.105:80] (392 bytes)

NSE: TCP 192.168.1.106:59923 < 192.168.1.105:80 | 00000000: 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f 4b 0d HTTP/1.1 200 OK

00000010: 0a 44 61 74 65 3a 20 54 75 65 2c 20 33 30 20 53 Date: Tue, 30 S

00000020: 65 70 20 32 30 31 34 20 31 30 3a 30 38 3a 32 34 ep 2014 10:08:24