TCPDUMP - The Easy Tutorial

Networking TCPdump
最近更新: Apr 22 2010


Chinese translation by YukiAlex.


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TCPdump是一款功能强大的网络包窃听工具。

由于这套软件会将网络卡运行在promiscuous mode，所以只有root或者拥有superuser权利的用户才能执行该软件。

Wireshark（前身是ethereal）可以被视为拥有图形界面的TCPdump。Wireshark也可以读取TCPdump产生的logs。

1. 下载TCPDUMP 2. 使用TCPDUMP


1. 下载TCPDUMP

要下载TCPdump

#apt-get install tcpdump
要查看TCPdump的依赖关系

#apt-cache depends tcpdump
tcpdump
   Depends: libc6
   Depends: libpcap0.8
   Depends: libssl0.9.8

要查看TCPdump的版本

#apt-cache policy tcpdump
tcpdump:
   Installed: 3.9.4-2ubuntu0.1
   Candidate: 3.9.4-2ubuntu0.1
   Version table:
  *** 3.9.4-2ubuntu0.1 0
            500 http://security.ubuntu.com dapper-security/main Packages
            100 /var/lib/dpkg/status
         3.9.4-2 0
            500 http://ch.archive.ubuntu.com dapper/main Packages


2. 使用TCPDUMP

显示标准TCPdump输出

#tcpdump
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

21:57:29.004426 IP 192.168.1.2.1034 > valve-68-142-64-164.phx3.llnw.net.27014: UDP, length 53
21:57:31.228013 arp who-has 192.168.1.2 tell 192.168.1.1
21:57:31.228020 arp reply 192.168.1.2 is-at 00:04:75:22:22:22 (oui Unknown)
21:57:38.035382 IP 192.168.1.2.1034 > valve-68-142-64-164.phx3.llnw.net.27014: UDP, length 53
21:57:38.613206 IP valve-68-142-64-164.phx3.llnw.net.27014 > 192.168.1.2.1034: UDP, length 36

显示详细输出

#tcpdump -v
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

22:00:11.625995 IP (tos 0x0, ttl 128, id 30917, offset 0, flags [none], proto: UDP (17), length: 81) 192.168.1.2.1034 > valve-68-142-64-164.phx3.llnw.net.27014: UDP, length 53
22:00:20.691903 IP (tos 0x0, ttl 128, id 31026, offset 0, flags [none], proto: UDP (17), length: 81) 192.168.1.2.1034 > valve-68-142-64-164.phx3.llnw.net.27014: UDP, length 53
22:00:21.230970 IP (tos 0x0, ttl 114, id 4373, offset 0, flags [none], proto: UDP (17), length: 64) valve-68-142-64-164.phx3.llnw.net.27014 > 192.168.1.2.1034: UDP, length 36
22:00:26.201715 arp who-has 192.168.1.2 tell 192.168.1.1
22:00:26.201726 arp reply 192.168.1.2 is-at 00:04:11:11:11:11 (oui Unknown)
22:00:29.706020 IP (tos 0x0, ttl 128, id 31133, offset 0, flags [none], proto: UDP (17), length: 81) 192.168.1.2.1034 > valve-68-142-64-164.phx3.llnw.net.27014: UDP, length 53
22:00:38.751355 IP (tos 0x0, ttl 128, id 31256, offset 0, flags [none], proto: UDP (17), length: 81) 192.168.1.2.1034 > valve-68-142-64-164.phx3.llnw.net.27014: UDP, length 53

可以用来抓包的网络界面

#tcpdump -D
1.eth0
2.any (Pseudo-device that captures on all interfaces)
3.lo

显示IP地址，不显示DNS名称

#tcpdump -n
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

22:02:36.111595 IP 192.168.1.2.1034 > 68.142.64.164.27014: UDP, length 53
22:02:36.669853 IP 68.142.64.164.27014 > 192.168.1.2.1034: UDP, length 36
22:02:41.702977 arp who-has 192.168.1.2 tell 192.168.1.1
22:02:41.702984 arp reply 192.168.1.2 is-at 00:04:11:11:11:11
22:02:45.106515 IP 192.168.1.2.1034 > 68.142.64.164.27014: UDP, length 53
22:02:50.392139 IP 192.168.1.2.138 > 192.168.1.255.138: NBT UDP PACKET(138)
22:02:54.139658 IP 192.168.1.2.1034 > 68.142.64.164.27014: UDP, length 53
22:02:57.866958 IP 125.175.131.58.3608 > 192.168.1.2.9501: S 3275472679:3275472679(0) win 65535

显示快速输出

#tcpdump -q
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes

22:03:55.594839 IP a213-22-130-46.cpe.netcabo.pt.3546 > 192.168.1.2.9501: tcp 0
22:03:55.698827 IP 192.168.1.2.9501 > a213-22-130-46.cpe.netcabo.pt.3546: tcp 0
22:03:56.068088 IP a213-22-130-46.cpe.netcabo.pt.3546 > 192.168.1.2.9501: tcp 0
22:03:56.068096 IP 192.168.1.2.9501 > a213-22-130-46.cpe.netcabo.pt.3546: tcp 0
22:03:57.362863 IP 192.168.1.2.1034 > valve-68-142-64-164.phx3.llnw.net.27014: UDP, length 53
22:03:57.964397 IP valve-68-142-64-164.phx3.llnw.net.27014 > 192.168.1.2.1034: UDP, length 36
22:04:06.406521 IP 192.168.1.2.1034 > valve-68-142-64-164.phx3.llnw.net.27014: UDP, length 53
22:04:15.393757 IP 192.168.1.2.1034 > valve-68-142-64-164.phx3.llnw.net.27014: UDP, length 53

抓取指定网络界面的数据包

tcpdump -i eth0
抓取UDP数据包

#tcpdump udp
抓取端口80的TCP数据包

#tcpdump port http
抓取储存在文件中的filter的数据包

#tcpdump -F file_name
在已经设置好的filter中新增文件（这里是TCP端口80）

#vim file_name
port 80
在抓取20个数据包之后停止

#tcpdump -c 20
将结果输出到文件中而不显示在屏幕上

#tcpdump -w capture.log
读取文件

#tcpdump -r capture.log
reading from file capture.log, link-type EN10MB (Ethernet)

09:33:51.977522 IP 192.168.1.36.40332 > rr.knams.wikimedia.org.www: P 1548302662:1548303275(613) ack 148796145 win 16527
09:33:52.031729 IP rr.knams.wikimedia.org.www > 192.168.1.36.40332: . ack 613 win 86
09:33:52.034414 IP rr.knams.wikimedia.org.www > 192.168.1.36.40332: P 1:511(510) ack 613 win86
09:33:52.034786 IP 192.168.1.36.40332 > rr.knams.wikimedia.org.www: . ack 511 win 16527

抓取的数据并不是储存成文本格式，因此不能用文本编辑器阅读。必须用特别的软件，比如TCP dump（见上文）或者提供图形界面的Wireshark（前身是Ethereal）。

用Wireshark打开抓取的日志


显示来源或目的地为"www.openmaniak.com" 的数据包

#tcpdump host www.openmaniak.com
显示从192.168.1.100 发送到 192.168.1.2的FTP数据包

#tcpdump src 192.168.1.100 and dst 192.168.1.2 and port ftp
显示数据包的内容

#tcpdump -A
在ftp连接中抓取数据包。由于FTP密码是用明文传送，所以能够被轻易截获。

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on ath0, link-type EN10MB (Ethernet), capture size 96 bytes
20:53:24.872785 IP ubuntu.local.40205 > 192.168.1.2.ftp: S 4155598838:4155598838(0) win 5840
....g....................
............
20:53:24.879473 IP ubuntu.local.40205 > 192.168.1.2.ftp: . ack 1228937421 win 183
....g.I@.............
........
20:53:24.881654 IP ubuntu.local.40205 > 192.168.1.2.ftp: . ack 43 win 183
....g.I@.......8.....
......EN
20:53:26.402046 IP ubuntu.local.40205 > 192.168.1.2.ftp: P 0:10(10) ack 43 win 183
....g.I@......`$.....
...=..ENUSER teddybear

20:53:26.403802 IP ubuntu.local.40205 > 192.168.1.2.ftp: . ack 76 win 183
....h.I@.............
...>..E^
20:53:29.169036 IP ubuntu.local.40205 > 192.168.1.2.ftp: P 10:25(15) ack 76 win 183
....h.I@......#c.....
......E^PASS wakeup

20:53:29.171553 IP ubuntu.local.40205 > 192.168.1.2.ftp: . ack 96 win 183
....h.I@.,...........
......Ez
20:53:29.171649 IP ubuntu.local.40205 > 192.168.1.2.ftp: P 25:31(6) ack 96 win 183
....h.I@.,...........
......EzSYST

20:53:29.211607 IP ubuntu.local.40205 > 192.168.1.2.ftp: . ack 115 win 183
....h.I@.?.....j.....
......Ez
20:53:31.367619 IP ubuntu.local.40205 > 192.168.1.2.ftp: P 31:37(6) ack 115 win 183
....h.I@.?...........
......EzQUIT

20:53:31.369316 IP ubuntu.local.40205 > 192.168.1.2.ftp: . ack 155 win 183
....h.I@.g...........
......E.
20:53:31.369759 IP ubuntu.local.40205 > 192.168.1.2.ftp: F 37:37(0) ack 156 win 183
....h.I@.h.....e.....
......E.

We see in this capture the FTP username (teddybear) and password (wakeup).

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