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 192.168.4.100Starting Nmap 5.51 ( http://nmap.org ) at 2015-05-17 17:55 CSTNmap scan report for 192.168.4.100Host is up (0.00028s latency).Not shown: 990 closed portsPORT STATE SERVICE21/tcp open ftp22/tcp open ssh25/tcp open smtp80/tcp open http110/tcp open pop3111/tcp open rpcbind143/tcp open imap443/tcp open https993/tcp open imaps995/tcp open pop3sMAC 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 21-22 192.168.4.0/24Starting Nmap 5.51 ( http://nmap.org ) at 2015-05-17 18:00 CSTNmap scan report for 192.168.4.1Host is up (0.000025s latency).PORT STATE SERVICE21/tcp open ftp22/tcp open sshNmap scan report for 192.168.4.5Host is up.PORT STATE SERVICE21/tcp filtered ftp22/tcp filtered sshNmap scan report for 192.168.4.120Host is up (0.00052s latency).PORT STATE SERVICE21/tcp open ftp22/tcp open sshMAC 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 SERVICE21/tcp closed ftp22/tcp closed sshMAC Address: 00:50:56:C0:00:01 (VMware)Nmap scan report for 192.168.4.120Host is up (0.00051s latency).PORT STATE SERVICE21/tcp closed ftp22/tcp closed sshMAC 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 192.168.4.0/24Starting Nmap 5.51 ( http://nmap.org ) at 2015-05-17 18:01 CSTNmap scan report for 192.168.4.1Host is up.Nmap scan report for 192.168.4.5Host is up.Nmap scan report for 192.168.4.120Host is up (0.00027s latency).MAC Address: 00:0C:29:74:BE:21 (VMware)Nmap scan report for 192.168.4.110Host is up (0.00016s latency).MAC Address: 00:50:56:C0:00:01 (VMware)Nmap scan report for 192.168.4.120Host 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 192.168.4.100,120Starting Nmap 5.51 ( http://nmap.org ) at 2015-05-17 18:03 CSTNmap 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 portsPORT STATE SERVICE VERSION21/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.sig22/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 smtpd80/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 rpcbind143/tcp open imap Dovecot imapd|_imap-capabilities: LOGIN-REFERRALS STARTTLS IMAP4rev1 ENABLE AUTH=PLAIN LITERAL+ IDLE SASL-IR ID443/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).993/tcp open ssl/imap Dovecot imapd|_imap-capabilities: IMAP4rev1 AUTH=PLAIN ENABLE ID LITERAL+ IDLE SASL-IR LOGIN-REFERRALS995/tcp open ssl/pop3 Dovecot pop3d|_pop3-capabilities: OK(K) CAPA RESP-CODES UIDL PIPELINING USER TOP SASL(PLAIN)MAC Address: 00:0C:29:74:BE:21 (VMware)No exact OS matches for host (If you know what OS is running on it, see http://nmap.org/submit/ ).TCP/IP fingerprint:OS:SCAN(V=5.51%D=8/19%OT=21%CT=1%CU=34804%PV=Y%DS=1%DC=D%G=Y%M=000C29%TM=52OS:11ED90%P=x86_64-redhat-linux-gnu)SEQ(SP=106%GCD=1%ISR=10B%TI=Z%CI=Z%II=IOS:%TS=A)OPS(O1=M5B4ST11NW6%O2=M5B4ST11NW6%O3=M5B4NNT11NW6%O4=M5B4ST11NW6%OOS:5=M5B4ST11NW6%O6=M5B4ST11)WIN(W1=3890%W2=3890%W3=3890%W4=3890%W5=3890%W6OS:=3890)ECN(R=Y%DF=Y%T=40%W=3908%O=M5B4NNSNW6%CC=Y%Q=)T1(R=Y%DF=Y%T=40%S=OOS:%A=S+%F=AS%RD=0%Q=)T2(R=N)T3(R=N)T4(R=Y%DF=Y%T=40%W=0%S=A%A=Z%F=R%O=%RD=OS:0%Q=)T5(R=Y%DF=Y%T=40%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=)T6(R=Y%DF=Y%T=40%W=0%OS:S=A%A=Z%F=R%O=%RD=0%Q=)T7(R=Y%DF=Y%T=40%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=)U1(OS:R=Y%DF=N%T=40%IPL=164%UN=0%RIPL=G%RID=G%RIPCK=G%RUCK=G%RUD=G)IE(R=Y%DFI=OS:N%T=40%CD=S)Network Distance: 1 hopService Info: Host: mail.tarena.com; OS: UnixTRACEROUTEHOP RTT ADDRESS1 1.55 ms 192.168.4.100Nmap 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 portsPORT STATE SERVICE VERSION135/tcp open msrpc Microsoft Windows RPC139/tcp open netbios-ssn445/tcp open microsoft-ds Microsoft Windows XP microsoft-dsMAC Address: 00:0C:29:DB:84:46 (VMware)Device type: general purposeRunning: Microsoft Windows XPOS details: Microsoft Windows XP SP2 - SP3Network Distance: 1 hopService Info: OS: WindowsHost script results:|_nbstat: NetBIOS name: PC-201307130328, NetBIOS user: 
       
        , 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+8TRACEROUTEHOP RTT ADDRESS1 0.47 ms 192.168.4.120OS 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.rpmwarning: libnet-1.1.5-1.el6.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 0608b895: NOKEYPreparing... ########################################### [100%]1:libnet ########################################### [ 50%]2:ettercap ########################################### [100%]

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 TeamListening on:eth0 -> 00:0C:29:AA:77:15192.168.4.5/255.255.255.0fe80::20c:29ff:feaa:7715/64SSL dissection needs a valid 'redir_command_on' script in the etter.conf filePrivileges dropped to UID 65534 GID 65534...plugin ec_sslstrip.so cannot be loaded...30 plugins40 protocol dissectors55 ports monitored13861 mac vendor fingerprint1766 tcp OS fingerprint2183 known servicesStarting 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 helpFTP : 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 21tcpdump: verbose output suppressed, use -v or -vv for full protocol decodelistening 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、确认收集到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 0E..4..@.@......x...d.*..G.\b........;...............18:47:25.964268 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [S.], seq 2284929633, ack 1201822819, win 14600, options [mss 1460,nop,nop,sackOK,nop,wscale 6], length 0E..4..@.@......d...x...*.1BaG.\c..9.7...............18:47:25.964436 IP 192.168.4.120.novation > 192.168.4.100.ftp: Flags [.], ack 1, win 65535, length 0E..(..@.@.. ...x...d.*..G.\c.1BbP.............18:47:25.967592 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [P.], seq 1:21, ack 1, win 229, length 20E..
       
         192.168.4.100.ftp: Flags [.], ack 21, win 65515, length 0E..(..@.@......x...d.*..G.\c.1BvP.............18:47:27.960530 IP 192.168.4.120.novation > 192.168.4.100.ftp: Flags [P.], seq 1:14, ack 21, win 65515, length 13E..5..@.@......x...d.*..G.\c.1BvP.......USER mickey18:47:27.960544 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [.], ack 14, win 229, length 0E..(FK@.@.jX...d...x...*.1BvG.\pP.............18:47:27.960783 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [P.], seq 21:55, ack 14, win 229, length 34E..JFL@.@.j5...d...x...*.1BvG.\pP...i~..331 Please specify the password.18:47:28.085168 IP 192.168.4.120.novation > 192.168.4.100.ftp: Flags [.], ack 55, win 65481, length 0E..(..@.@......x...d.*..G.\p.1B.P.............18:47:29.657364 IP 192.168.4.120.novation > 192.168.4.100.ftp: Flags [P.], seq 14:27, ack 55, win 65481, length 13E..5..@.@......x...d.*..G.\p.1B.P.......PASS pwd12318:47:29.696968 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [.], ack 27, win 229, length 0E..(FM@.@.jV...d...x...*.1B.G.\}P.............18:47:29.702671 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [P.], seq 55:78, ack 27, win 229, length 23E..?FN@.@.j>...d...x...*.1B.G.\}P.......230 Login successful.18:47:29.835258 IP 192.168.4.120.novation > 192.168.4.100.ftp: Flags [.], ack 78, win 65458, length 0E..(..@.@......x...d.*..G.\}.1B.P.............18:47:31.716375 IP 192.168.4.120.novation > 192.168.4.100.ftp: Flags [P.], seq 27:33, ack 78, win 65458, length 6E.....@.@......x...d.*..G.\}.1B.P... ...QUIT18:47:31.716532 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [.], ack 33, win 229, length 0E..(FO@.@.jT...d...x...*.1B.G.\.P....}........18:47:31.716634 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [P.], seq 78:92, ack 33, win 229, length 14E..6FP@.@.jE...d...x...*.1B.G.\.P.......221 Goodbye.18:47:31.716677 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [F.], seq 92, ack 33, win 229, length 0E..(FQ@.@.jR...d...x...*.1B.G.\.P....n........18:47:31.717053 IP 192.168.4.120.novation > 192.168.4.100.ftp: Flags [.], ack 93, win 65444, length 0E..(..@.@......x...d.*..G.\..1B.P.............18:47:31.718796 IP 192.168.4.120.novation > 192.168.4.100.ftp: Flags [F.], seq 33, ack 93, win 65444, length 0E..(..@.@......x...d.*..G.\..1B.P.............18:47:31.719097 IP 192.168.4.100.ftp > 192.168.4.120.novation: Flags [.], ack 34, win 229, length 0E..(..@.@......d...x...*.1B.G.\.P....m........