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24	<p></p>
25	<p class="Style2"><span class="Style3">README : Scapysec v1.0 (IPsec
26	for Scapy)</span><br />
27	<br />
28	</p>
29	<p class="Style4"> Author: Frederic ROUDAUT <br />
30	(frederic.roudaut@free.fr)</p>
31	<p class="Style4"> Date : 2006</p>
32	<p class="Style2"> </p>
33	<p class="Style8"><a href="#chap1">1 - INTRODUCTION : Scapy & Scapysec</a><br />
34	<a href="#chap2">2 - OVERVIEW</a><br />
35	<a href="#chap3">3 - NEEDS AND INSTALLATION</a><br />
36	<a href="#chap4">4 - THE ESP CLASS</a><br />
37	<a href="#chap5">5 - SECURITY ASSOCIATIONS DATABASE (SAD)</a><br />
38	<a href="#chap5_1">5.1 - PACKET MATCHING WITH SA</a><br />
39	<a href="#chap5_2">5.2 - ENCRYPTION ALGORITHMS</a><br />
40	<a href="#chap5_3">5.3 - AUTHENTICATION ALGORITHM</a><br />
41	<a href="#chap5_4">5.4 - SETTING THE SAD</a><br />
42	<a href="#chap5_4_1">5.4.1 - ADDING A SA</a><br />
43	<a href="#chap5_4_2">5.4.2 - DELETING A SA</a><br />
44	<a href="#chap5_4_3">5.4.3 - CLEARING THE DATABASE</a><br />
45	<a href="#chap6">6 - ENCRYPTION ON THE FLIGHT : IPsec Class</a><br />
46	<a href="#chap7">7 - WHAT'S MORE</a><br />
47	<a href="#chap8">8 - UPDATE</a><br />
48	<a href="#chap9">9 - POSSIBLE EXTENSIONS</a><br />
49	<a href="#chap10">10 - CREDITS AND LICENCE</a><br />
50	<a href="#chap11">11 - BUGS</a></p>
51	<p class="Style8"><a href="#chapA">ANNEX A - IPSEC ALGORITHMS AND KEYS</a><br />
52	<a href="#chapA.1">A.1 - ESP ALGORITHMS</a><br />
53	<a href="#chapA.1.1">A.1.1 - REQUIREMENTS</a><br />
54	<a href="#chapA.1.2">A.1.2 : TripleDES-CBC [RFC2451]</a><br />
55	<a href="#chapA.1.3">A.1.3 : AES-CBC with 128-bit keys [RFC3602]</a><br />
56	<a href="#chapA.1.4">A.1.4 : AES-CTR [RFC3686]</a><br />
57	<a href="#chapA.1.5">A.1.5 : DES-CBC [RFC2405]</a><br />
58	<a href="#chapA.1.6">A.1.6 : BLOWFISH-CBC [RFC2451]</a><br />
59	<a href="#chapA.1.7">A.1.7 : HMAC-MD5-96 [RFC2403]</a><br />
60	<a href="#chapA.1.8">A.1.8 : HMAC-SHA1-96 [RFC2404]</a><br />
61	<a href="#chapA.1.9">A.1.9 : HMAC-SHA256</a></p>
62	<p class="Style7"> </p>
63	<p class="Style2"> </p>
64	<h2 class="Style2"><span class="Style6">1 - INTRODUCTION : Scapy & Scapysec</span><a name="chap1" id="chap1"></a><br />
65	</h2>
66	<p class="Style2">"Scapy (<a href="http://www.secdev.org/projects/scapy/">http://www.secdev.org/projects/scapy/</a>) is a powerful<br />
67	interactive packet manipulation program. It is able to forge or decode<br />
68	packets of a wide number of protocols, send them on the wire, capture<br />
69	them, match requests and replies, and much more. It can easily handle<br />
70	most classical tasks like scanning, tracerouting, probing, unit tests,<br />
71	attacks or network discovery (it can replace hping, 85% of nmap,<br />
72	arpspoof, arp-sk, arping, tcpdump, tethereal, p0f, etc.). It also<br />
73	performs very well at a lot of other specific tasks that most other<br />
74	tools can't handle, like sending invalid frames, injecting your own<br />
75	802.11 frames, combining technics (VLAN hopping+ARP cache poisoning,<br />
76	VOIP decoding on WEP encrypted channel, ...), etc"</p>
77
78	<p> Scapy6 (<a
79	href="http://namabiiru.hongo.wide.ad.jp/scapy6/">http://namabiiru.hongo.wide.ad.jp/scapy6/</a>)
80	is an extension to handle IPv6 Packets.
81	</p>
82	<p class="Style2">Scapysec aims is to extend Scapy to handle IPsec packets with IPv4 or IPv6.<br />
83	Ie to encode/decode IPsec packets, generate any valid/invalid IPsec<br />
84	Packet using different encryption and authentication algorithms. <br />
85	On this basis, some more complex applications could be build up. </p>
86	<p class="Style2">Currently, Scapysec supports ESP with :</p>
87	<p class="Style2"><strong>Encryption Algorithm</strong> (Key Lengths in bits) <block lenght in bytes><br />
88	--------------------<br />
89	<strong>NULL</strong> : (Any)<br />
90	<strong>TripleDES-CBC</strong> [RFC2451] : (192) <8><br />
91	<strong>AES-CBC</strong> [RFC3602] : (128/192/256) <16><br />
92	<strong>AES-CTR </strong>[RFC3686] : (160/224/288) The remaining 32 bits will be used as nonce. <16><br />
93	<strong>DES-CBC</strong> [RFC2405] : (64) <8><br />
94	<strong>BLOWFISH-CBC</strong> : (128) <8><br />
95	<strong>CAST-CBC</strong> : (Any) <8></p>
96	<p class="Style2"><strong>Authentication Algorithm</strong> (Key Lengths in bits)<br />
97	------------------------<br />
98	<strong>NULL</strong><br />
99	<strong>HMAC-SHA1-96</strong> [RFC2404] : (Any)<br />
100	<strong>HMAC-MD5-96</strong> [RFC2403] : (Any)<br />
101	<strong>HMAC-SHA256</strong> : (Any)</p>
102	<p> </p>
103	<h2 class="Style2"><span class="Style6">2 - OVERVIEW</span><a name="chap2" id="chap2"></a><br />
104	</h2>
105	<p class="Style2">The example will be explained later but shows how it is simple to<br />
106	generate encrypted IPsec packets. </p>
107	<p><span class="Style1">>>></span> q = IP(dst="192.168.0.6")/ESP(spi=5)/TCP()<br />
108	<span class="Style1">>>></span> q.show2()</p>
109	<p>== IPv4 IPsec SA Used for: <Src: 192.168.0.2> <Dst: 192.168.0.6> <Spi: 5> ==<br />
110	<Src: *> <Dst: 192.168.0.6> <Spi: *><br />
111	Crypt Algo: AES-CTR<br />
112	Crypt Key: 00001234abc12ffffbc1<br />
113	Auth Algo: HMAC-MD5<br />
114	Auth Key: 5632abc1azefvc</p>
115	<p><span class="Style1">###[ IP ]###</span><br />
116	version= 4L<br />
117	ihl= 5L<br />
118	tos= 0x0<br />
119	len= 80<br />
120	id= 1<br />
121	flags=<br />
122	frag= 0L<br />
123	ttl= 64<br />
124	proto= IPv6-Crypt<br />
125	chksum= 0xf922<br />
126	src= 192.168.0.2<br />
127	dst= 192.168.0.6<br />
128	options= ''<br />
129	<span class="Style1">###[ ESP ]###</span><br />
130	spi= 0x5L<br />
131	seq= 0L<br />
132	data= 0<br />
133	iv= '\xc7\xaem\xba<\x08i\x93'<br />
134	pad= 'XyYkQx8RDl'<br />
135	padlen= 10<br />
136	nh= TCP<br />
137	authentication= '\n\xf8[\x1a\xe0\xaf\xc1\xab4f\x0f\xda'<br />
138	<span class="Style1">###[ TCP ]###</span><br />
139	sport= ftp-data<br />
140	dport= http<br />
141	seq= 0L<br />
142	ack= 0L<br />
143	dataofs= 5L<br />
144	reserved= 0L<br />
145	flags= S<br />
146	window= 8192<br />
147	chksum= 0xe26<br />
148	urgptr= 0<br />
149	options= {}<br />
150	<span class="Style1">>>></span> q.show2()</p>
151	<p><span class="Style2">In this example we have several things. Indeed the packet matchs what<br />
152	we will call a Security Association:</span><br />
153	<Src: *> <Dst: 192.168.0.6> <Spi: *><br />
154	<span class="Style2">Then the packet is created. All the fields are filled, the packet is<br />
155	encrypted and the authentication is computed and appended according to<br />
156	the Algorithm specified in the Security Association</span></p>
157	<p class="Style2">When q.show2() is called, the reverse is done. The security<br />
158	Association matching the packet is found and the packet is decrypted<br />
159	before the printing as it has been sent by another host on the<br />
160	network.</p>
161	<p> </p>
162	<h2 class="Style2"><span class="Style6">3 - NEEDS AND INSTALLATION</span><a name="chap3" id="chap3"></a><br />
163	</h2>
164	<p class="Style2">Scapysec uses the Python language 2.3 or upcomming versions. There is<br />
165	no paticular need. You just need to have scapy.py and scapy6.py if you<br />
166	want to be able to generate IPsec packets with IPv6.<br />
167	You also need pycrypto since all the encryption/decryption is done<br />
168	using this library.</p>
169	<p><span class="Style2">just do : </span>python ./scapysec.py</p>
170	<p class="Style2">Oups, you also need a few adaptions to Scapy. <br />
171	Normaly it should be included with this file. If not you may
172	download it to <a href="http://roudaut.frederic.free.fr/data/scapysec/scapy.py"> http://roudaut.frederic.free.fr/data/scapysec/scapy.py</a>.
173	</p>
174	<p class="Style2">
175	Scapy6 may be downloaded to <a href="http://namabiiru.hongo.wide.ad.jp/scapy6/"> http://namabiiru.hongo.wide.ad.jp/scapy6/ </a>.
176	</p>
177
178	</p>
179
180	<p> </p>
181	<h2 class="Style2"><span class="Style6">4 - The ESP CLASS</span><a name="chap4" id="chap4"></a><br />
182	</h2>
183	<p class="Style2">The different fields of the ESP layer may be seen using ls()<br />
184	If you do not know about Scapy, this command gives the field name,<br />
185	the type, the value and the default value for this field</p>
186	<p><span class="Style1">>>></span> ls(ESP())<br />
187	spi : XIntField = 0 (0)<br />
188	seq : IntField = 0 (0)<br />
189	data : StrField = None (None)<br />
190	iv : StrField = None (None)<br />
191	pad : StrField = None (None)<br />
192	padlen : ByteField = None (None)<br />
193	nh : ByteEnumField = None (None)<br />
194	authentication : StrField = None (None)<br />
195	</p>
196	<p>The fields are the following : <br />
197	- spi : Security Parameters Index<br />
198	- seq : Sequence Number<br />
199	- data : data field is used to give directly encrypted data for iv + pad + padlen + nh<br />
200	- iv : Initialization Vector. Computed if not set. The size is<br />
201	precised by the Encryption Algorithm<br />
202	- pad : Filled if not set and depending from the Encryption Algorithm<br />
203	- padlen : Pad length. Computed if not set<br />
204	- nh : Next Header. Set if not set<br />
205	- authentication : Computed if available<br />
206	</p>
207	<p class="Style2">pad, padlen and iv lengths are depending from the Encryption<br />
208	Algorithms. As you may create packets that will fail with Encryption,<br />
209	they will be corrected if inadequate.</p>
210	<p class="Style2">The data field will be used to directly give encrypted data<br />
211	for iv + pad + padlen + nh</p>
212	<p class="Style2">As you may see, you now have to find a way to indicate:<br />
213	- the Encryption Algorithm<br />
214	- the Encryption Key<br />
215	- the Authentication Algorithm<br />
216	- the Authentication Key</p>
217	<p class="Style2">These elements will be indicated in the Security Associations Database</p>
218	<p class="Style2"> </p>
219	<h2 class="Style2"><span class="Style6">5 - SECURITY ASSOCIATIONS DATABASE (SAD)</span><a name="chap5" id="chap5"></a><br />
220	</h2>
221	<p class="Style2">Here is an example of the SAD<br />
222	</p>
223	<p>ipsec_sad_example = {'IPV4' : [['192.168.0.2','192.168.0.1','5','ESP','BLOWFISH-CBC','azdregrnytnytftg','HMAC-SHA1','ecuheznbevnbevabgj'],\<br />
224	['192.168..2','192.168.0.5','5','ESP','DES-CBC','5632abc1','HMAC-SHA1','5632abc1azefvc'],\<br />*
225	['192.168.0.2','192.168.0.3','0x0005','ESP','AES-CBC','1234abc12ffffbc1','HMAC-SHA1','5632abc1azefvc'],\<br />
226	['192.168.0.2','192.168.0.7','','ESP','AES-CBC','1234abc12ffffbc1','HMAC-SHA256','5llll632abc1azefvc'],\<br />*
227	['','192.168.0.6','','ESP','AES-CTR','1234abc12ffffbc1','HMAC-MD5','5632abc1azefvc'],\<br />
228	['192.168..2','192.168.0.8','','ESP','DES-CBC','5632abcuyfyuf1','HMAC-SHA1','5632abc1azefvc'],\<br />
229	['192.168..2','192.168.0.12','','ESP','DES-CBC','5632abcuyfyuf1','HMAC-MD5','5632abc1azefvc'],\<br />
230	['192.168.0.2','192..0.4','','ESP','NULL','','NULL','']],\<br />
231	'IPV6' : [['','fe80::240:96ff:fea7:c5d1','5','ESP','DES-CBC','5632abc1','HMAC-SHA1','5632abc1azefvc'],\<br />*
232	['','3ffe::3','0x0005','ESP','AES-CBC','1234abc12ffffbc1','HMAC-SHA1','5632abc1azefvc'],\<br />*
233	['','3fe::4','','ESP','AES-CBC','1234abc12ffffbc1','HMAC-SHA256','5llll632abc1azefvc']]}<br />
234	</p>
235	<p class="Style2">The SAD is a dictionnary {'IPV4':[],'IPV6':[]}<br />
236	One entry is for IPv4, the other one is for IPv6. <br />
237	Each one contains a list of Security Associations (SAs).<br />
238	The SA described hereafter gives:<br />
239	- the source address filter: '192.168.0.2'<br />
240	- the destination address filter: '192.168.0.1'<br />
241	- the SPI filter: '5'<br />
242	- the protocol: 'AH' or 'ESP' : <br />
243	- the Encryption Algorithm : 'BLOWFISH-CBC'<br />
244	- the Encryption Key : 'azdregrnytnytftg'<br />
245	- the Authentication Algorithm : 'HMAC-SHA1'<br />
246	- the Authentication Key : 'ecuheznbevnbevabgj'</p>
247	<p>['192.168.0.2','192.168.0.1','5','ESP','BLOWFISH-CBC','azdregrnytnytftg','HMAC-SHA1','ecuheznbevnbevabgj']<br />
248	</p>
249	<p class="Style2">When an IPsec Packet is sent or received, the corresponding SAD entry<br />
250	(IPv4 or IPv6) is checked. If the packet is catched by one security<br />
251	association, it will be encrypted or decrypted using the associated<br />
252	algorithms and keys. </p>
253	<p> </p>
254	<h2 class="Style2"><span class="Style6">5.1 - PACKET MATCHING WITH SA</span><a name="chap5_1" id="chap5_1"></a><br />
255	</h2>
256	<p class="Style2">An IPsec packet is catched by a security association if its source,<br />
257	destination address and SPI match a corresponding entry in the SAD.<br />
258	The matching uses the wildcard '*'.</p>
259	<p><span class="Style2">Address are string. It may be IPv4 (</span>'192.168.0.2'<span class="Style2">) or any IPv6 address</span><br />
260	('3FFE::1'<span class="Style2"> or </span>'fe80::240:96ff:fea7:c5d0'<span class="Style2">)</span><br />
261	<span class="Style2">You may use</span> ''<span class="Style2"> to indicate any address or</span> '' <span class="Style2">in the address string.<br />
262	For IPv4, we then may have </span>'192.168..2'<span class="Style2">. Each</span> '' <span class="Style2">means 1 byte. <br />
263	For IPv6, each</span> '' <span class="Style2">means 4 bits. (</span>'3FF::1', 'fe80::240:96ff:fea7:c5d0'<span class="Style2">)</span></p>
264	<p><span class="Style2">The SPI is a string but it may represent an integer value (</span>'8') <span class="Style2">or an<br />
265	hexadecimal value (</span>'0x23'<span class="Style2">).</span> <br />
266	<span class="Style2">You also may use</span> ''<span class="Style2"> to indicate any SPI or even</span> '' <span class="Style2">in the<br />
267	hexadecimal SPI string as</span> '0x346'.<span class="Style2"*> In this case we do not mind about<br />
268	the hexadecimal value between the</span> '4' <span class="Style2">and the </span>'6' </p>
269	<p> </p>
270	<h2 class="Style2"><span class="Style6">5.2 - ENCRYPTION ALGORITHMS</span><a name="chap5_2" id="chap5_2"></a><br />
271	</h2>
272	<p class="Style2">The Encryption Algorithms available are the following:<br />
273	Between () we give the key length available in bits.<br />
274	Between <> we indicate the block size in bytes</p>
275	<p>NULL : (Any)<br />
276	3DES-CBC [RFC2451] : (192) <8><br />
277	AES-CBC : (128/192/256) <16><br />
278	AES-CTR : (160/224/288) The remaining 32 bits will be used as nonce. <16><br />
279	DES-CBC [RFC2405] : (64) <8><br />
280	BLOWFISH-CBC : (128) <8><br />
281	CAST-CBC : (Any) <8><br />
282	</p>
283	<p class="Style2">A key with an incorrect length will not be used. Instead it may be<br />
284	truncated or enhanced.</p>
285	<p class="Style2"> </p>
286	<h2 class="Style2"><span class="Style6">5.3 - AUTHENTICATION ALGORITHM</span><a name="chap5_3" id="chap5_3"></a><br />
287	</h2>
288	<p class="Style2">The Authentication Algorithms available are the following:<br />
289	Between () we give the key lenght available.</p>
290	<p>NULL : (Any)<br />
291	HMAC-SHA1-96 [RFC2404] : (Any)<br />
292	HMAC-MD5-96 [RFC2403] : (Any)<br />
293	HMAC-SHA256 : (Any)<br />
294	</p>
295	<p class="Style2">A key with an incorrect length will not be used. Instead it may be<br />
296	truncated or enhanced.</p>
297	<p> </p>
298	<h2 class="Style2"><span class="Style6">5.4 - SETTING THE SAD</span><a name="chap5_4" id="chap5_4"></a><br />
299	</h2>
300	<p><span class="Style2">The conf Instance has been enhanced with a setkey variable that uses<br />
301	the</span> _IPSEC_SAD <span class="Style2">Python Class.</span></p>
302	<p class="Style2">Then if you do conf.setkey you get the current SAD</p>
303	<p><span class="Style1">>>></span> conf.setkey<br />
304	== IPv4 Security Associations ==<br />
305	<Src : 192.168.0.2> <Dst : 192.168.0.1> <SPI : 5><br />
306	Mode ESP<br />
307	Crypt Algo : BLOWFISH-CBC Crypt Key : azdregrnytnytftg<br />
308	Auth Algo : HMAC-SHA1 Auth Key : ecuheznbevnbevabgj</p>
309	<p><Src : 192.168..2> <Dst : 192.168.0.5> <SPI : 5><br />*
310	Mode ESP<br />
311	Crypt Algo : DES-CBC Crypt Key : 5632abc1<br />
312	Auth Algo : HMAC-SHA1 Auth Key : 5632abc1azefvc</p>
313	<p><Src : 192.168.0.2> <Dst : 192.168.0.3> <SPI : 0x0005><br />
314	Mode ESP<br />
315	Crypt Algo : AES-CBC Crypt Key : 1234abc12ffffbc1<br />
316	Auth Algo : HMAC-SHA1 Auth Key : 5632abc1azefvc</p>
317	<p><Src : 192.168.0.2> <Dst : 192.168.0.7> <SPI : *><br />
318	Mode ESP<br />
319	Crypt Algo : AES-CBC Crypt Key : 1234abc12ffffbc1<br />
320	Auth Algo : HMAC-SHA256 Auth Key : 5llll632abc1azefvc</p>
321	<p><Src : *> <Dst : 192.168.0.6> <SPI : *><br />
322	Mode ESP<br />
323	Crypt Algo : AES-CTR Crypt Key : 1234abc12ffffbc1<br />
324	Auth Algo : HMAC-MD5 Auth Key : 5632abc1azefvc</p>
325	<p><Src : 192.168..2> <Dst : 192.168.0.8> <SPI : ><br />
326	Mode ESP<br />
327	Crypt Algo : DES-CBC Crypt Key : 5632abcuyfyuf1<br />
328	Auth Algo : HMAC-SHA1 Auth Key : 5632abc1azefvc</p>
329	<p><Src : 192.168..2> <Dst : 192.168.0.12> <SPI : ><br />
330	Mode ESP<br />
331	Crypt Algo : DES-CBC Crypt Key : 5632abcuyfyuf1<br />
332	Auth Algo : HMAC-MD5 Auth Key : 5632abc1azefvc<br />
333	</p>
334	<p><span class="Style2">Then you may create a static configuration by doing : </span><br />
335	conf.setkey = _IPSEC_SAD(ipsec_sad_example) # Security Association Database for IPsec</p>
336	<p> </p>
337	<h2 class="Style2"><span class="Style6">5.4.1 - ADDING A SA</span><a name="chap5_4_1" id="chap5_4_1"></a><br />
338	</h2>
339	<p class="Style2">The simplest way to do this is to use the add command.</p>
340	<p>def add(self,proto,src,dst,spi,mode,algo_crypt,algo_key_crypt,algo_auth,algo_key_auth)</p>
341	<p class="Style2">All Parameters types are strings:</p>
342	<p>proto : <span class="Style2">either </span>'IPV4' <span class="Style2">or</span> 'IPV6'<br />
343	src : <span class="Style2">source address filter </span><br />
344	dst : <span class="Style2">destination address filter</span><br />
345	spi :<span class="Style2"> spi filter</span><br />
346	mode : <span class="Style2">either</span> 'ESP' <span class="Style2">or</span> 'AH'<br />
347	algo_crypt : <span class="Style2">Ecncryption Algorithm</span><br />
348	algo_key_crypt : <span class="Style2">Encryption Key</span><br />
349	algo_auth : <span class="Style2">Authentication Algorithm</span><br />
350	algo_key_auth : <span class="Style2">Authentication</span><br />
351	</p>
352	<p><span class="Style1">>>></span> conf.setkey.add('IPV4','','192.168..42','6','ESP','AES-CBC', '1234abc12ffffbc1', 'HMAC-SHA256' ,'5llll632abc1azefvc')</p>
353	<p> </p>
354	<h2 class="Style2"><span class="Style6">5.4.2 - DELETING A SA</span><a name="chap5_4_2" id="chap5_4_2"></a><br />
355	</h2>
356	<p class="Style2">The simplest way to do this is to use the delete command.</p>
357	<p>def delete(self,proto,src,dst,spi)</p>
358	<p class="Style2">All Parameters types are strings:</p>
359	<p>proto : <span class="Style2">either </span>'IPV4' <span class="Style2">or</span> 'IPV6'<br />
360	src : <span class="Style2">source address filter </span><br />
361	dst : <span class="Style2">destination address filter</span><br />
362	spi :<span class="Style2"> spi filter</span></p>
363	<p><span class="Style2">if proto, src, dst and spi are </span>''<span class="Style2">, the SAD is clear. </span><br />*
364	<span class="Style2">If proto is not</span> '' <span class="Style2">only the corresponding one is clear. <br />*
365	Otherwise all the entries that exactly match the parameters are<br />
366	removed. The character</span> '' <span class="Style2"*>used as parameter in the function means<br />
367	that we do not care about this field. </span></p>
368	<p><span class="Style2">Thus the following example remove all entries in the IPv4 SAD that<br />
369	have</span> '192.168..42' <span class="Style2">as destination.</span></p>*
370	<p><span class="Style1">>>></span> conf.setkey.delete('IPV4','','192.168..42','')</p>*
371	<p> </p>
372	<h2 class="Style2"><span class="Style6">5.4.3 - CLEARING THE DATABASE</span><a name="chap5_4_3" id="chap5_4_3"></a><br />
373	</h2>
374	<p class="Style2">The following command will clear the database associated to IPv4 or<br />
375	IPv6</p>
376	<p class="Style2">def erase(self,proto)</p>
377	<p><span class="Style2">where proto is either</span> 'IPV4' <span class="Style2">or</span> 'IPV6'<br />
378	</p>
379	<p> </p>
380	<h2 class="Style2"><span class="Style6">6 - ENCRYPTION ON THE FLIGHT : IPsec Class</span><a name="chap6" id="chap6"></a><br />
381	</h2>
382	<p class="Style2">Sometimes it is not convenient to set the database prior to send<br />
383	packets. In this case you may use the IPsec class</p>
384	<p><span class="Style1">>>></span> ls(IPsec())<br />
385	crypt : StrField = 'NULL' ('NULL')<br />
386	crypt_key : StrField = '' ('')<br />
387	auth : StrField = 'NULL' ('NULL')<br />
388	auth_key : StrField = '' ('')<br />
389	</p>
390	<p><span class="Style1">>>></span> q = IP(dst="192.168.0.6")/IPsec(crypt='AES-CTR', crypt_key='00001234abc12ffffbc1', auth='HMAC-MD5', auth_key ='5632abc1azefvc')/<br />
391	ESP(spi=5)/TCP()<br />
392	<span class="Style1">>>></span> q.show()</p>
393	<p><span class="Style1">###[ IP ]###</span><br />
394	version= 4<br />
395	ihl= 0<br />
396	tos= 0x0<br />
397	len= 0<br />
398	id= 1<br />
399	flags=<br />
400	frag= 0<br />
401	ttl= 64<br />
402	proto= IPv6-Crypt<br />
403	chksum= 0x0<br />
404	src= 192.168.0.2<br />
405	dst= 192.168.0.6<br />
406	options= ''<br />
407	<span class="Style1">###[ IPsec ]###</span><br />
408	crypt= 'AES-CTR'<br />
409	crypt_key= '00001234abc12ffffbc1'<br />
410	auth= 'HMAC-MD5'<br />
411	auth_key= '5632abc1azefvc'<br />
412	<span class="Style1">###[ ESP ]###</span><br />
413	spi= 0x5<br />
414	seq= 0<br />
415	data= 0<br />
416	iv= 0<br />
417	pad= 0<br />
418	padlen= 0<br />
419	nh= TCP<br />
420	authentication= 0<br />
421	<span class="Style1">###[ TCP ]###</span><br />
422	sport= ftp-data<br />
423	dport= http<br />
424	seq= 0<br />
425	ack= 0<br />
426	dataofs= 0<br />
427	reserved= 0<br />
428	flags= S<br />
429	window= 8192<br />
430	chksum= 0x0<br />
431	urgptr= 0<br />
432	options= {}<br />
433	</p>
434	<p><span class="Style2">In this case we have no SAD for the packet then we cannot decrypt it. <br />
435	Thus we have to print it using</span> show()<span class="Style2">. If we use</span> show2()<span class="Style2">, the<br />
436	decryption will be tried and will certainly be uncorrect. <br />
437	</span></p>
438	<h2 class="Style2"><span class="Style6">7 - WHAT'S MORE </span><a name="chap7" id="chap7"></a><br />
439	</h2>
440	<p class="Style2">All the previous examples were using transport mode and you have<br />
441	certainly notice that there is no such indication in the SAD. <br />
442	In fact you have to do it by yourself ;-) :</p>
443	<p>q = IP(dst="192.168.0.6")/IPsec(crypt='AES-CTR', crypt_key='00001234abc11', auth='HMAC-MD5', auth_key ='5632abc1azefvc')/ESP(spi=5)/IP(dst="10.0.0.1")/TCP()<br />
444	<span class="Style1">>>></span> q.show() </p>
445	<p><span class="Style1">###[ IP ]###</span><br />
446	version= 4<br />
447	ihl= 0<br />
448	tos= 0x0<br />
449	len= 0<br />
450	id= 1<br />
451	flags=<br />
452	frag= 0<br />
453	ttl= 64<br />
454	proto= IPv6-Crypt<br />
455	chksum= 0x0<br />
456	src= 192.168.0.2<br />
457	dst= 192.168.0.6<br />
458	options= ''<br />
459	<span class="Style1">###[ IPsec ]###</span><br />
460	crypt= 'AES-CTR'<br />
461	crypt_key= '00001234abc11'<br />
462	auth= 'HMAC-MD5'<br />
463	auth_key= '5632abc1azefvc'<br />
464	<span class="Style1">###[ ESP ]###</span><br />
465	spi= 0x5<br />
466	seq= 0<br />
467	data= 0<br />
468	iv= 0<br />
469	pad= 0<br />
470	padlen= 0<br />
471	nh= IP-ENCAP<br />
472	authentication= 0<br />
473	<span class="Style1">###[ IP ]###</span><br />
474	version= 4<br />
475	ihl= 0<br />
476	tos= 0x0<br />
477	len= 0<br />
478	id= 1<br />
479	flags=<br />
480	frag= 0<br />
481	ttl= 64<br />
482	proto= TCP<br />
483	chksum= 0x0<br />
484	src= 192.168.0.2<br />
485	dst= 10.0.0.1<br />
486	options= ''<br />
487	<span class="Style1">###[ TCP ]###</span><br />
488	sport= ftp-data<br />
489	dport= http<br />
490	seq= 0<br />
491	ack= 0<br />
492	dataofs= 0<br />
493	reserved= 0<br />
494	flags= S<br />
495	window= 8192<br />
496	chksum= 0x0<br />
497	urgptr= 0<br />
498	options= {}<br />
499	</p>
500	<p class="Style2">And using the same principles you may have a lot of different IPv4,<br />
501	IPv6, ESP encapsulations with some different algorithms.</p>
502	<p class="Style2">Some checks may be done using Wireshark (<a href="http://www.wireshark.org">www.wireshark.org</a>). Have a look to <a href="http://wiki.wireshark.org/ESP_Preferences"> the Wireshark wiki </a> for more information. <br />
503	I currently found a bug in AES-CTR I will try to solve later since I am the author of this plugin ;-(.</p>
504	<p class="Style2">The algorithms handled with Wireshark are the following:</p>
505	<p class="Style4">Encryption Algorithms : <br />
506	<br />
507	- NULL<br />
508	- TripleDES-CBC [RFC2451] : keylen 192 bits.<br />
509	- AES-CBC with 128-bit keys [RFC3602] : keylen 128 and 192/256 bits.<br />
510	- AES-CTR [RFC3686] : keylen 160/224/288 bits. The remaining 32 bits will be used as nonce.<br />
511	- DES-CBC [RFC2405] : keylen 64 bits<br />
512	- BLOWFISH-CBC : keylen 128 bits.<br />
513	- TWOFISH-CBC : keylen 128/256 bits.</p>
514	<p class="Style4">Authentication Algorithms:<br />
515	<br />
516	- NULL<br />
517	- HMAC-SHA1-96 [RFC2404] : any keylen<br />
518	- HMAC-MD5-96 [RFC2403] : any keylen<br />
519	- HMAC-SHA256 : any keylen</p>
520	<p> </p>
521	<h2 class="Style2"><span class="Style6">8 - UPDATE</span><a name="chap8" id="chap8"></a><br />
522	</h2>
523	<p class="Style2"> </p>
524	<h2 class="Style2"><span class="Style6">9 - POSSIBLE EXTENSIONS</span><a name="chap9" id="chap9"></a><br />
525	</h2>
526	<p class="Style2">For sure, you may use some others ESP Encryption algorithms. I only<br />
527	have done the work for Algorithms specified in RFC4305. <br />
528	Nevertheless, it should not be very difficult to add some other ones. <br />
529	Have a look to the code ;-(</p>
530	<p class="Style2">Moreover, you may also add some other Authentication Algorithms. <br />
531	AES-XCBC-MAC-96 has not been added because i had trouble to get a<br />
532	working implementation.</p>
533	<p class="Style2">For the moment it works only for ESP but why not adding AH.<br />
534	On this basis it could be possible to have a better look to IKE. </p>
535	<p class="Style2">An interesting point with this tool is that if your kernel does not<br />
536	handle IPsec or a particular algorithm it could be quite easy as<br />
537	Wifitap (http://sid.rstack.org/index.php/Wifitap) does to have an<br />
538	interface to generate such encrypted packets

Scapy

Ticket #26: scapysec.html