linux安全 Nmap扫描与Tcpdump抓包分析

扫描与抓包分析

3.1 问题

本案例要求熟悉Linux主机环境下的常用安全工具，完成以下任务操作：

1. 使用Nmap扫描来获取指定主机/网段的相关信息
2. 使用EtterCAP截获明文通信的密码、检测非加密通信的脆弱性
3. 使用Tcpdump分析FTP访问中的明文交换信息

3.2 方案

使用两台RHEL6虚拟机，其中svr5作为扫描、嗅探、抓包的操作用机，而mail作为测试用的靶机；另外准备一台Windows客户机pc120，也可以作为靶机

3.3 步骤

实现此案例需要按照如下步骤进行。

步骤一：使用Nmap扫描来获取指定主机/网段的相关信息

1）检查目标主机mail所开启的TCP服务

[root@svr5 ~]# nmap 192.168.4.100
Starting Nmap 5.51 ( http://nmap.org ) at 2015-05-17 17:55 CST
Nmap scan report for 192.168.4.100
Host is up (0.00028s latency).
Not shown: 990 closed ports
PORT STATE SERVICE
21/tcp open ftp
22/tcp open SSH
25/tcp open smtp
80/tcp open http
110/tcp open pop3
111/tcp open rpcbind
143/tcp open imap
443/tcp open https
993/tcp open imaps
995/tcp open pop3s
MAC Address: 00:0C:29:74:BE:21 (VMware)
Nmap done: 1 IP address (1 host up) scanned in 1.31 seconds

2）检查192.168.4.0/24网段内哪些主机开启了FTP、SSH服务

[root@svr5 ~]# nmap -p 21-22 192.168.4.0/24
Starting Nmap 5.51 ( http://nmap.org ) at 2015-05-17 18:00 CST
Nmap scan report for 192.168.4.1
Host is up (0.000025s latency).
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
Nmap scan report for 192.168.4.5
Host is up.
PORT STATE SERVICE
21/tcp filtered ftp
22/tcp filtered ssh
Nmap scan report for 192.168.4.120
Host is up (0.00052s latency).
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
MAC Address: 00:0C:29:74:BE:21 (VMware)
Nmap scan report for pc110.tarena.com (192.168.4.110)
Host is up (0.00038s latency).
PORT STATE SERVICE
21/tcp closed ftp
22/tcp closed ssh
MAC Address: 00:50:56:C0:00:01 (VMware)
Nmap scan report for 192.168.4.120
Host is up (0.00051s latency).
PORT STATE SERVICE
21/tcp closed ftp
22/tcp closed ssh
MAC Address: 00:0C:29:DB:84:46 (VMware)
Nmap done: 256 IP addresses (5 hosts up) scanned in 4.88 seconds

3）检查192.168.4.0/24网段内哪些主机可以ping通

[root@svr5 ~]# nmap -n -sP 192.168.4.0/24
Starting Nmap 5.51 ( http://nmap.org ) at 2015-05-17 18:01 CST
Nmap scan report for 192.168.4.1
Host is up.
Nmap scan report for 192.168.4.5
Host is up.
Nmap scan report for 192.168.4.120
Host is up (0.00027s latency).
MAC Address: 00:0C:29:74:BE:21 (VMware)
Nmap scan report for 192.168.4.110
Host is up (0.00016s latency).
MAC Address: 00:50:56:C0:00:01 (VMware)
Nmap scan report for 192.168.4.120
Host is up (0.00046s latency).
MAC Address: 00:0C:29:DB:84:46 (VMware)
Nmap done: 256 IP addresses (5 hosts up) scanned in 3.57 seconds

4）全面分析目标主机192.168.4.100、192.168.4.120的操作系统信息

[root@svr5 ~]# nmap -A 192.168.4.100,120
Starting Nmap 5.51 ( http://nmap.org ) at 2015-05-17 18:03 CST
Nmap scan report for 192.168.4.100                    //主机mail的扫描报告
Host is up (0.0016s latency).
Not shown: 990 closed ports
PORT STATE SERVICE VERSION
21/tcp open ftp vsftpd 2.2.2
| ftp-anon: Anonymous FTP login allowed (FTP code 230)
| -rw-r--r-- 1 0 0 1719 Aug 17 13:33 UserB.pub
| -rw-r--r-- 1 0 0 122 Aug 13 05:27 dl.txt
| drwxr-xr-x 2 14 0 4096 Aug 13 09:07 pub
| -rw-rw-r-- 1 505 505 170 Aug 17 13:18 tools-1.2.3.tar.gz
|_-rw-rw-r-- 1 505 505 287 Aug 17 13:22 tools-1.2.3.tar.gz.sig
22/tcp open ssh OpenSSH 5.3 (protocol 2.0)
| ssh-hostkey: 1024 86:be:d6:89:c1:2d:d9:1f:57:2f:66:d1:af:a8:d3:c6 (DSA)
|_2048 16:0a:15:01:fa:bb:91:1d:cc:ab:68:17:58:f9:49:4f (RSA)
25/tcp open smtp Postfix smtpd
80/tcp open http Apache httpd 2.2.15 ((Red Hat))
|_http-methods: No Allow or Public header in OPTIONS response (status code 302)
| http-title: 302 Found
|_Did not follow redirect to https://192.168.4.100//
110/tcp open pop3 Dovecot pop3d
|_pop3-capabilities: USER CAPA UIDL TOP OK(K) RESP-CODES PIPELINING STLS SASL(PLAIN)
111/tcp open rpcbind
143/tcp open imap Dovecot imapd
|_imap-capabilities: LOGIN-REFERRALS STARTTLS IMAP4rev1 ENABLE AUTH=PLAIN LITERAL+ IDLE SASL-IR ID
443/tcp open SSL/http Apache httpd 2.2.15 ((Red Hat))
| http-methods: Potentially risky methods: TRACE
|_See http://nmap.org/nsedoc/scripts/http-methods.html
|_http-title: Site doesn't have a title (text/html; charset=UTF-8).
...
Network Distance: 1 hop
Service Info: Host: mail.tarena.com; OS: Unix
TRACEROUTE
HOP RTT ADDRESS
1 1.55 ms 192.168.4.100
Nmap scan report for 192.168.4.120                    //主机pc120的扫描报告
Host is up (0.00047s latency).
Not shown: 997 closed ports
PORT STATE SERVICE VERSION
135/tcp open msrpc Microsoft Windows RPC
139/tcp open netbios-ssn
445/tcp open microsoft-ds Microsoft Windows XP microsoft-ds
MAC Address: 00:0C:29:DB:84:46 (VMware)
Device type: general purpose
Running: Microsoft Windows XP
OS deTails: Microsoft Windows XP SP2 - SP3
Network Distance: 1 hop
Service Info: OS: Windows
Host script results:
|_nbstat: NetBIOS name: PC-201307130328, NetBIOS user: <unknown>, NetBIOS MAC: 00:0c:29:db:84:46 (VMware)
|_smbv2-enabled: Server doesn't support SMBv2 protocol
| smb-os-discovery:
| OS: Windows XP (Windows 2000 LAN MANAger)
| Name: WORKGROUP\PC-201307130328
|_ System time: 2015-05-17 18:04:40 UTC+8
TRACEROUTE
HOP RTT ADDRESS
1 0.47 ms 192.168.4.120
OS and Service detection performed. Please report any incorrect results at http://nmap.org/submit/ .
Nmap done: 2 IP addresses (2 hosts up) scanned in 43.01 seconds

步骤二：使用EtterCAP截获明文通信的密码，检测非加密通信的脆弱性

1）安装EtterCAP嗅探工具

下载（或老师提供）软件包ettercap、依赖包libnet，执行rpm安装。

[root@svr5 ~]# cd /var/ftp/pub
[root@svr5 ~]# rpm -ivh libnet-1.1.5-1.el6.x86_64.rpm\
> ettercap-0.7.5-3.el6.1.20120906gitc796e5.x86_64.rpm
...

2）EtterCAP工具的命令行模式

执行ettercap命令，嗅探主机192.168.4.120与主机192.168.4.100的FTP服务（21端口）之间的数据通信，收集用户名、密码信息。

[root@svr5 ~]# ettercap -Tzq /192.168.4.100//21 /192.168.4.120//
ettercap 0.7.5 copyright 2001-2012 Ettercap Development Team
Listening on:
eth0 -> 00:0C:29:AA:77:15
192.168.4.5/255.255.255.0
fe80::20c:29ff:feaa:7715/64
SSL dissection needs a valid 'redir_command_on' script in the etter.conf file
Privileges dropped to UID 65534 GID 65534...
plugin ec_sslstrip.so cannot be loaded...
30 plugins
40 protocol dissecTors
55 ports monitored
13861 mac vendor fingerprint
1766 tcp OS fingerprint
2183 known services
Starting Unified sniffing...                    //进入标准监听状态
Text only Interface activated...
Hit 'h' for inline help

处于监听状态以后，从测试机pc120访问主机mail的vsftpd服务，如图-10所示。

图-10

然后查看执行中的ettercap命令行界面，将会发现收集到的用户名、密码信息。

.. ..
Text only Interface activated...
Hit 'h' for inline help
FTP : 192.168.4.120:21 -> USER: mickey PASS: pwd123

3）EtterCAP工具的图形模式

在GNOME桌面环境下， 执行ettercap -G即可打开窗口程序。选择菜单“Sniffer”-->“Unified Sniffer”监听，指定网卡eth0；然后添加两个主机192.168.4.100、192.168.4.120作为嗅探目标（Targets），选择“Start”-->“Sniffing“即可进入监听状态。

参考前面的测试操作，再次从客户机pc120访问主机mail的vsftpd服务。然后查看执行中的ettercap监听窗口程序，同样可以收集到用户名、密码信息，如图-11所示。

图-11

步骤三：使用Tcpdump分析FTP访问中的明文交换信息

1）启用tcpdump命令行抓包

执行tcpdump命令行，添加适当的过滤条件，只抓取访问主机192.168.4.100的21端口的数据通信 ，并转换为ASCII码格式的易读文本。

[root@svr5 ~]# tcpdump -A host 192.168.4.100 and tcp port 21
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
.. ..                                            //进入等待捕获数据包的状态

2）执行FTP访问，并观察tcpdump抓包结果

参考前面的测试操作，再次从客户机pc120访问主机mail的vsftpd服务。然后查看执行中tcpdump程序的输出，仔细分析FTP连接的建立过程、确认收集���的用户名和口令信息。

. ..
18:47:25.964110 IP 192.168.4.120.novation > 192.168.4.100.ftp: Flags [S], seq 1201822818, win 65535, options [mss 1460,nop,wscale 0,nop,nop,sackOK], length 0
E..4..@.@......x...d.*..G.\b........;...............

原文摘自linux公社 https://www.linuxidc.com/Linux/2019-09/160564.htm

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