1: /*
2: *
3: * libnet 1.1
4: * Build a GRE packet
5: * To view: tcpdump -s 0 -n -X -vvv proto gre
6: *
7: * Copyright (c) 2003 Frédéric Raynal <pappy@security-labs.org>
8: * All rights reserved.
9: *
10: *
11: * KNOWN BUG
12: * the encapsulated headers have wrong checksums. I guess this is due to
13: * the one pass libnet_pblock_coalesce() which is really to complicated :(
14: *
15: *
16: * Default packet:
17: * # ./gre -d 1.2.3.4
18: * libnet 1.1 packet shaping: GRE 1701 [link]
19: * Wrote 78 byte GRE packet; check the wire.
20: *
21: * 18:58:12.112157 192.168.1.2 > 1.2.3.4: gre 198.35.123.50.1234 > 103.69.139.107.53: S [bad tcp cksum 698a!] 16843009:16843009(0) win 32767 (ttl 64, id 242, len 40, bad cksum 0!) (ttl 255, id 255, len 64)
22: * 0x0000 4500 0040 00ff 0000 ff2f f4df c0a8 0102 E..@...../......
23: * 0x0010 0102 0304 0000 0800 4500 0028 00f2 0000 ........E..(....
24: * 0x0020 4006 0000 c623 7b32 6745 8b6b 04d2 0035 @....#{2gE.k...5
25: * 0x0030 0101 0101 0202 0202 5002 7fff 6666 0000 ........P...ff..
26: *
27: * Packet with a computed checksum
28: * # ./gre -d 1.2.3.4 -c 0
29: * libnet 1.1 packet shaping: GRE 1701 [link]
30: * Wrote 82 byte GRE packet; check the wire.
31: *
32: * 18:58:22.587513 192.168.1.2 > 1.2.3.4: gre [Cv0] C:7c62 198.35.123.50.1234 > 103.69.139.107.53: S [bad tcp cksum 698a!] 16843009:16843009(0) win 32767 (ttl 64, id 242, len 40, bad cksum 0!) (ttl 255, id 255, len 68)
33: * 0x0000 4500 0044 00ff 0000 ff2f f4db c0a8 0102 E..D...../......
34: * 0x0010 0102 0304 8000 0800 7c62 0000 4500 0028 ........|b..E..(
35: * 0x0020 00f2 0000 4006 0000 c623 7b32 6745 8b6b ....@....#{2gE.k
36: * 0x0030 04d2 0035 0101 0101 0202 0202 5002 7fff ...5........P...
37: * 0x0040 6666 0000 ff..
38: *
39: *
40: * Packet with a forced checksum
41: * # ./gre -d 1.2.3.4 -c 6666
42: * libnet 1.1 packet shaping: GRE 1701 [link]
43: * Wrote 68 byte GRE packet; check the wire.
44: *
45: * 19:04:12.108080 192.168.1.2 > 1.2.3.4: gre [Cv0] C:1a0a 198.35.123.50.1234 > 103.69.139.107.53: S [bad tcp cksum 698a!] 16843009:16843009(0) win 32767 (ttl 64, id 242, len 40, bad cksum 0!) (ttl 255, id 255, len 68)
46: * 0x0000 4500 0044 00ff 0000 ff2f f4db c0a8 0102 E..D...../......
47: * 0x0010 0102 0304 8000 0800 1a0a 0000 4500 0028 ............E..(
48: * 0x0020 00f2 0000 4006 0000 c623 7b32 6745 8b6b ....@....#{2gE.k
49: * 0x0030 04d2 0035 0101 0101 0202 0202 5002 7fff ...5........P...
50: * 0x0040 6666 0000 ff..
51: *
52: *
53: *
54: *
55: * Redistribution and use in source and binary forms, with or without
56: * modification, are permitted provided that the following conditions
57: * are met:
58: * 1. Redistributions of source code must retain the above copyright
59: * notice, this list of conditions and the following disclaimer.
60: * 2. Redistributions in binary form must reproduce the above copyright
61: * notice, this list of conditions and the following disclaimer in the
62: * documentation and/or other materials provided with the distribution.
63: *
64: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
65: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
66: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
67: * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
68: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
69: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
70: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
71: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
72: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
73: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
74: * SUCH DAMAGE.
75: *
76: */
77:
78: #if (HAVE_CONFIG_H)
79: #include "../include/config.h"
80: #endif
81: #include "./libnet_test.h"
82:
83:
84: void
85: usage(char *prog)
86: {
87: fprintf(stderr, "Usage: %s\n", prog);
88: fprintf(stderr, "\t IP options: -d <dst ip> [-s src ip]\n");
89: fprintf(stderr, "\t GRE options: [-v] set RFC 2637 mode (PPP in GRE) (default is RFC 1701 for IP in GRE)\n");
90: fprintf(stderr, "\t\t RFC 1701 options (IP in GRE):\n");
91: fprintf(stderr, "\t\t [-c sum] [-r routing] [-k key] [-n seqnum]\n");
92: fprintf(stderr, "\t\t IP in GRE options: [-S src ip] [-D dst ip]\n");
93: fprintf(stderr, "\t\t RFC 2637 options (PPP in GRE):\n");
94: fprintf(stderr, "\t\t [-a ack]\n");
95:
96: exit(1);
97: }
98:
99: /*
100: * ---------------------------------
101: * | Delivery Header |
102: * ---------------------------------
103: * | GRE Header |
104: * ---------------------------------
105: * | Payload packet |
106: * ---------------------------------
107: */
108: int
109: main(int argc, char *argv[])
110: {
111: char c;
112: libnet_t *l;
113: char errbuf[LIBNET_ERRBUF_SIZE];
114: u_long src_ip = 0, dst_ip = 0, gre_src_ip = 0, gre_dst_ip = 0;
115: u_short checksum = 0, offset = 0;
116: u_char *routing = NULL;
117: u_long key = 0, seq = 0;
118: u_short gre_flags = 0;
119: u_long len;
120: u_long size = 0;
121: libnet_ptag_t t;
122:
123: printf("libnet 1.1 packet shaping: GRE [link]\n");
124:
125: /*
126: * Initialize the library. Root priviledges are required.
127: */
128: l = libnet_init(
129: LIBNET_LINK, /* injection type */
130: NULL, /* network interface */
131: errbuf); /* error buffer */
132:
133: if (!l)
134: {
135: fprintf(stderr, "libnet_init: %s", errbuf);
136: exit(EXIT_FAILURE);
137: }
138:
139: /*
140: * parse options
141: */
142: while ((c = getopt(argc, argv, "d:s:D:S:c:r:k:n:va:")) != EOF)
143: {
144: switch (c)
145: {
146:
147: case 'd':
148: if ((dst_ip = libnet_name2addr4(l, optarg, LIBNET_RESOLVE)) == -1)
149: {
150: fprintf(stderr, "Bad destination IP address: %s\n", optarg);
151: exit(EXIT_FAILURE);
152: }
153: break;
154: case 's':
155: if ((src_ip = libnet_name2addr4(l, optarg, LIBNET_RESOLVE)) == -1)
156: {
157: fprintf(stderr, "Bad source IP address: %s\n", optarg);
158: exit(EXIT_FAILURE);
159: }
160: break;
161: case 'D':
162: if ((gre_dst_ip = libnet_name2addr4(l, optarg, LIBNET_RESOLVE)) == -1)
163: {
164: fprintf(stderr, "Bad destination IP address (GRE): %s\n", optarg);
165: exit(EXIT_FAILURE);
166: }
167: break;
168: case 'S':
169: if ((gre_src_ip = libnet_name2addr4(l, optarg, LIBNET_RESOLVE)) == -1)
170: {
171: fprintf(stderr, "Bad source IP address (GRE): %s\n", optarg);
172: exit(EXIT_FAILURE);
173: }
174: break;
175: case 'c':
176: checksum = atoi(optarg);
177: gre_flags|=GRE_CSUM;
178: break;
179: case 'r':
180: routing = (u_char *)optarg;
181: gre_flags|=GRE_ROUTING;
182: break;
183: case 'k':
184: key = atoi(optarg);
185: gre_flags|=GRE_KEY;
186: break;
187: case 'n':
188: seq = atoi(optarg);
189: gre_flags|=GRE_SEQ;
190: break;
191: case 'v':
192: gre_flags|=(GRE_VERSION_1|GRE_KEY);
193: break;
194: case 'a':
195: if (! (gre_flags & GRE_VERSION_1))
196: usage(argv[0]);
197: seq = atoi(optarg); /* seq in v0 is ack in v1 */
198: gre_flags|=GRE_ACK;
199: break;
200: default:
201: exit(EXIT_FAILURE);
202: }
203: }
204:
205: /*
206: * check options
207: */
208: if (!dst_ip)
209: {
210: usage(argv[0]);
211: }
212:
213: if (!src_ip)
214: {
215: src_ip = libnet_get_ipaddr4(l);
216: }
217:
218: if (!gre_dst_ip)
219: {
220: gre_dst_ip = libnet_get_prand(LIBNET_PRu32);
221: }
222:
223: if (!gre_src_ip)
224: {
225: gre_src_ip = libnet_get_prand(LIBNET_PRu32);
226: }
227:
228:
229: if ( (gre_flags & GRE_VERSION_MASK) == 0)
230: {
231: /*
232: * Build a TCP/IP packet embedded in GRE message
233: */
234: size = LIBNET_TCP_H;
235: t = libnet_build_tcp(
236: 1234, /* source port */
237: 53, /* destination port */
238: 0x01010101, /* sequence number */
239: 0x02020202, /* acknowledgement num */
240: TH_SYN, /* control flags */
241: 32767, /* window size */
242: 0, /* checksum */
243: 0, /* urgent pointer */
244: size, /* TCP packet size */
245: NULL, /* payload */
246: 0, /* payload size */
247: l, /* libnet handle */
248: 0); /* libnet id */
249: if (t == -1)
250: {
251: fprintf(stderr, "Can't build TCP header (GRE): %s\n", libnet_geterror(l));
252: goto bad;
253: }
254:
255: size += LIBNET_IPV4_H;
256: t = libnet_build_ipv4(
257: size, /* length */
258: 0, /* TOS */
259: 242, /* IP ID */
260: 0, /* IP Frag */
261: 64, /* TTL */
262: IPPROTO_TCP, /* protocol */
263: 0, /* checksum */
264: gre_src_ip, /* source IP */
265: gre_dst_ip, /* destination IP */
266: NULL, /* payload */
267: 0, /* payload size */
268: l, /* libnet handle */
269: 0); /* libnet id */
270: if (t == -1)
271: {
272: fprintf(stderr, "Can't build IP header (GRE): %s\n", libnet_geterror(l));
273: goto bad;
274: }
275: }
276:
277: if ( (gre_flags & GRE_VERSION_MASK) == 1)
278: {
279: offset = libnet_get_prand(LIBNET_PRu16);
280: if (~gre_flags & GRE_ACK)
281: {
282: u_char ppp[4] = "\x00\x01"; /* PPP padding */
283: checksum = 2; /* checksum is in fact payload_s in PPP/GRE (v1) */
284: size = 2;
285: gre_flags|=GRE_SEQ;
286: key = libnet_get_prand(LIBNET_PRu32);
287:
288: /*
289: * Build a PPP packet embedded in GRE message
290: */
291: t = libnet_build_data(
292: ppp,
293: checksum,
294: l,
295: 0
296: );
297: if (t == -1)
298: {
299: fprintf(stderr, "Can't build PPP header (GRE): %s\n", libnet_geterror(l));
300: goto bad;
301: }
302: }
303: gre_flags&=~(GRE_CSUM|GRE_ROUTING);
304: }
305:
306: /*
307: * Build the GRE message
308: */
309: if (gre_flags & GRE_ROUTING)
310: {
311: /* as packet are stacked, start by the last one, ie null sre */
312: size += LIBNET_GRE_SRE_H;
313: t = libnet_build_gre_last_sre(l, 0);
314: if (t == -1)
315: {
316: fprintf(stderr, "Can't build GRE last SRE header: %s\n", libnet_geterror(l));
317: goto bad;
318: }
319: size += LIBNET_GRE_SRE_H + strlen((char *)routing);
320: t = libnet_build_gre_sre(
321: GRE_IP, /* address family */
322: 0, /* offset */
323: strlen((char *)routing), /* routing length */
324: routing, /* routing info */
325: NULL, /* payload */
326: 0, /* payload size */
327: l, /* libnet handle */
328: 0); /* libnet id */
329: if (t == -1)
330: {
331: fprintf(stderr, "Can't build GRE last SRE header: %s\n", libnet_geterror(l));
332: goto bad;
333: }
334: }
335:
336: len = libnet_getgre_length(gre_flags);
337: size += len;
338: t = libnet_build_gre(
339: gre_flags, /* flags & version */
340: (gre_flags & GRE_VERSION_1 ? GRE_PPP : GRE_IP), /* type */
341: checksum, /* v0: checksum / v1: payload_s */
342: offset, /* v0: offset / v1: callID */
343: key, /* v0: key / v1: seq bum */
344: seq, /* v0: seq num / v1: ack */
345: size, /* length */
346: NULL, /* payload */
347: 0, /* payload size */
348: l, /* libnet handle */
349: 0); /* libnet id */
350: if (t == -1)
351: {
352: fprintf(stderr, "Can't build GRE header: %s\n", libnet_geterror(l));
353: goto bad;
354: }
355:
356:
357: /*
358: * Build the "real" IP header
359: */
360: size+=LIBNET_IPV4_H;
361: t = libnet_build_ipv4(
362: size, /* length */
363: 0, /* TOS */
364: 255, /* IP ID */
365: 0, /* IP Frag */
366: 255, /* TTL */
367: IPPROTO_GRE, /* protocol */
368: 0, /* checksum */
369: src_ip, /* source IP */
370: dst_ip, /* destination IP */
371: NULL, /* payload */
372: 0, /* payload size */
373: l, /* libnet handle */
374: 0); /* libnet id */
375: if (t == -1)
376: {
377: fprintf(stderr, "Can't build IP header (GRE): %s\n", libnet_geterror(l));
378: goto bad;
379: }
380:
381: t = libnet_autobuild_ethernet(
382: (uint8_t *)"11:11:11:11:11:11", /* ethernet destination */
383: ETHERTYPE_IP, /* protocol type */
384: l); /* libnet handle */
385: if (t == -1)
386: {
387: fprintf(stderr, "Can't build ethernet header: %s\n",
388: libnet_geterror(l));
389: goto bad;
390: }
391: /*
392: * Write it to the wire.
393: */
394:
395: c = libnet_write(l);
396: if (c == -1)
397: {
398: fprintf(stderr, "Write error: %s\n", libnet_geterror(l));
399: goto bad;
400: }
401: else
402: {
403: fprintf(stderr, "Wrote %d byte GRE packet; check the wire.\n", c);
404: }
405: libnet_destroy(l);
406: return (EXIT_SUCCESS);
407: bad:
408: libnet_destroy(l);
409: return (EXIT_FAILURE);
410: }
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