Loading...
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 | /* FTP extension for IP connection tracking. */
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/ip.h>
#include <linux/ctype.h>
#include <net/checksum.h>
#include <net/tcp.h>
#include <linux/netfilter_ipv4/lockhelp.h>
#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
#include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
DECLARE_LOCK(ip_ftp_lock);
struct module *ip_conntrack_ftp = THIS_MODULE;
#define MAX_PORTS 8
static int ports[MAX_PORTS];
static int ports_c;
#ifdef MODULE_PARM
MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
#endif
static int loose = 0;
MODULE_PARM(loose, "i");
#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif
static int try_rfc959(const char *, size_t, u_int32_t [], char);
static int try_eprt(const char *, size_t, u_int32_t [], char);
static int try_espv_response(const char *, size_t, u_int32_t [], char);
static struct ftp_search {
enum ip_conntrack_dir dir;
const char *pattern;
size_t plen;
char skip;
char term;
enum ip_ct_ftp_type ftptype;
int (*getnum)(const char *, size_t, u_int32_t[], char);
} search[] = {
{
IP_CT_DIR_ORIGINAL,
"PORT", sizeof("PORT") - 1, ' ', '\r',
IP_CT_FTP_PORT,
try_rfc959,
},
{
IP_CT_DIR_REPLY,
"227 ", sizeof("227 ") - 1, '(', ')',
IP_CT_FTP_PASV,
try_rfc959,
},
{
IP_CT_DIR_ORIGINAL,
"EPRT", sizeof("EPRT") - 1, ' ', '\r',
IP_CT_FTP_EPRT,
try_eprt,
},
{
IP_CT_DIR_REPLY,
"229 ", sizeof("229 ") - 1, '(', ')',
IP_CT_FTP_EPSV,
try_espv_response,
},
};
static int try_number(const char *data, size_t dlen, u_int32_t array[],
int array_size, char sep, char term)
{
u_int32_t i, len;
memset(array, 0, sizeof(array[0])*array_size);
/* Keep data pointing at next char. */
for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
if (*data >= '0' && *data <= '9') {
array[i] = array[i]*10 + *data - '0';
}
else if (*data == sep)
i++;
else {
/* Unexpected character; true if it's the
terminator and we're finished. */
if (*data == term && i == array_size - 1)
return len;
DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
len, i, *data);
return 0;
}
}
DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
return 0;
}
/* Returns 0, or length of numbers: 192,168,1,1,5,6 */
static int try_rfc959(const char *data, size_t dlen, u_int32_t array[6],
char term)
{
return try_number(data, dlen, array, 6, ',', term);
}
/* Grab port: number up to delimiter */
static int get_port(const char *data, int start, size_t dlen, char delim,
u_int32_t array[2])
{
u_int16_t port = 0;
int i;
for (i = start; i < dlen; i++) {
/* Finished? */
if (data[i] == delim) {
if (port == 0)
break;
array[0] = port >> 8;
array[1] = port;
return i + 1;
}
else if (data[i] >= '0' && data[i] <= '9')
port = port*10 + data[i] - '0';
else /* Some other crap */
break;
}
return 0;
}
/* Returns 0, or length of numbers: |1|132.235.1.2|6275| */
static int try_eprt(const char *data, size_t dlen, u_int32_t array[6],
char term)
{
char delim;
int length;
/* First character is delimiter, then "1" for IPv4, then
delimiter again. */
if (dlen <= 3) return 0;
delim = data[0];
if (isdigit(delim) || delim < 33 || delim > 126
|| data[1] != '1' || data[2] != delim)
return 0;
DEBUGP("EPRT: Got |1|!\n");
/* Now we have IP address. */
length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
if (length == 0)
return 0;
DEBUGP("EPRT: Got IP address!\n");
/* Start offset includes initial "|1|", and trailing delimiter */
return get_port(data, 3 + length + 1, dlen, delim, array+4);
}
/* Returns 0, or length of numbers: |||6446| */
static int try_espv_response(const char *data, size_t dlen, u_int32_t array[6],
char term)
{
char delim;
/* Three delimiters. */
if (dlen <= 3) return 0;
delim = data[0];
if (isdigit(delim) || delim < 33 || delim > 126
|| data[1] != delim || data[2] != delim)
return 0;
return get_port(data, 3, dlen, delim, array+4);
}
/* Return 1 for match, 0 for accept, -1 for partial. */
static int find_pattern(const char *data, size_t dlen,
const char *pattern, size_t plen,
char skip, char term,
unsigned int *numoff,
unsigned int *numlen,
u_int32_t array[6],
int (*getnum)(const char *, size_t, u_int32_t[], char))
{
size_t i;
DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
if (dlen == 0)
return 0;
if (dlen <= plen) {
/* Short packet: try for partial? */
if (strnicmp(data, pattern, dlen) == 0)
return -1;
else return 0;
}
if (strnicmp(data, pattern, plen) != 0) {
#if 0
size_t i;
DEBUGP("ftp: string mismatch\n");
for (i = 0; i < plen; i++) {
DEBUGFTP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
i, data[i], data[i],
pattern[i], pattern[i]);
}
#endif
return 0;
}
DEBUGP("Pattern matches!\n");
/* Now we've found the constant string, try to skip
to the 'skip' character */
for (i = plen; data[i] != skip; i++)
if (i == dlen - 1) return -1;
/* Skip over the last character */
i++;
DEBUGP("Skipped up to `%c'!\n", skip);
*numoff = i;
*numlen = getnum(data + i, dlen - i, array, term);
if (!*numlen)
return -1;
DEBUGP("Match succeeded!\n");
return 1;
}
/* FIXME: This should be in userspace. Later. */
static int help(const struct iphdr *iph, size_t len,
struct ip_conntrack *ct,
enum ip_conntrack_info ctinfo)
{
/* tcplen not negative guaranteed by ip_conntrack_tcp.c */
struct tcphdr *tcph = (void *)iph + iph->ihl * 4;
const char *data = (const char *)tcph + tcph->doff * 4;
unsigned int tcplen = len - iph->ihl * 4;
unsigned int datalen = tcplen - tcph->doff * 4;
u_int32_t old_seq_aft_nl;
int old_seq_aft_nl_set;
u_int32_t array[6] = { 0 };
int dir = CTINFO2DIR(ctinfo);
unsigned int matchlen, matchoff;
struct ip_conntrack_tuple t, mask;
struct ip_ct_ftp *info = &ct->help.ct_ftp_info;
unsigned int i;
int found = 0;
/* Until there's been traffic both ways, don't look in packets. */
if (ctinfo != IP_CT_ESTABLISHED
&& ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
return NF_ACCEPT;
}
/* Not whole TCP header? */
if (tcplen < sizeof(struct tcphdr) || tcplen < tcph->doff*4) {
DEBUGP("ftp: tcplen = %u\n", (unsigned)tcplen);
return NF_ACCEPT;
}
/* Checksum invalid? Ignore. */
/* FIXME: Source route IP option packets --RR */
if (tcp_v4_check(tcph, tcplen, iph->saddr, iph->daddr,
csum_partial((char *)tcph, tcplen, 0))) {
DEBUGP("ftp_help: bad csum: %p %u %u.%u.%u.%u %u.%u.%u.%u\n",
tcph, tcplen, NIPQUAD(iph->saddr),
NIPQUAD(iph->daddr));
return NF_ACCEPT;
}
LOCK_BH(&ip_ftp_lock);
old_seq_aft_nl_set = info->seq_aft_nl_set[dir];
old_seq_aft_nl = info->seq_aft_nl[dir];
DEBUGP("conntrack_ftp: datalen %u\n", datalen);
if ((datalen > 0) && (data[datalen-1] == '\n')) {
DEBUGP("conntrack_ftp: datalen %u ends in \\n\n", datalen);
if (!old_seq_aft_nl_set
|| after(ntohl(tcph->seq) + datalen, old_seq_aft_nl)) {
DEBUGP("conntrack_ftp: updating nl to %u\n",
ntohl(tcph->seq) + datalen);
info->seq_aft_nl[dir] = ntohl(tcph->seq) + datalen;
info->seq_aft_nl_set[dir] = 1;
}
}
UNLOCK_BH(&ip_ftp_lock);
if(!old_seq_aft_nl_set ||
(ntohl(tcph->seq) != old_seq_aft_nl)) {
DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u)\n",
old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl);
return NF_ACCEPT;
}
/* Initialize IP array to expected address (it's not mentioned
in EPSV responses) */
array[0] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 24) & 0xFF;
array[1] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 16) & 0xFF;
array[2] = (ntohl(ct->tuplehash[dir].tuple.src.ip) >> 8) & 0xFF;
array[3] = ntohl(ct->tuplehash[dir].tuple.src.ip) & 0xFF;
for (i = 0; i < sizeof(search) / sizeof(search[0]); i++) {
if (search[i].dir != dir) continue;
found = find_pattern(data, datalen,
search[i].pattern,
search[i].plen,
search[i].skip,
search[i].term,
&matchoff, &matchlen,
array,
search[i].getnum);
if (found) break;
}
if (found == -1) {
/* We don't usually drop packets. After all, this is
connection tracking, not packet filtering.
However, it is neccessary for accurate tracking in
this case. */
if (net_ratelimit())
printk("conntrack_ftp: partial %s %u+%u\n",
search[i].pattern,
ntohl(tcph->seq), datalen);
return NF_DROP;
} else if (found == 0) /* No match */
return NF_ACCEPT;
DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
(int)matchlen, data + matchoff,
matchlen, ntohl(tcph->seq) + matchoff);
/* Update the ftp info */
LOCK_BH(&ip_ftp_lock);
if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3])
== ct->tuplehash[dir].tuple.src.ip) {
info->is_ftp = 1;
info->seq = ntohl(tcph->seq) + matchoff;
info->len = matchlen;
info->ftptype = search[i].ftptype;
info->port = array[4] << 8 | array[5];
} else {
/* Enrico Scholz's passive FTP to partially RNAT'd ftp
server: it really wants us to connect to a
different IP address. Simply don't record it for
NAT. */
DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
array[0], array[1], array[2], array[3],
NIPQUAD(ct->tuplehash[dir].tuple.src.ip));
/* Thanks to Cristiano Lincoln Mattos
<lincoln@cesar.org.br> for reporting this potential
problem (DMZ machines opening holes to internal
networks, or the packet filter itself). */
if (!loose) goto out;
}
t = ((struct ip_conntrack_tuple)
{ { ct->tuplehash[!dir].tuple.src.ip,
{ 0 } },
{ htonl((array[0] << 24) | (array[1] << 16)
| (array[2] << 8) | array[3]),
{ htons(array[4] << 8 | array[5]) },
IPPROTO_TCP }});
mask = ((struct ip_conntrack_tuple)
{ { 0xFFFFFFFF, { 0 } },
{ 0xFFFFFFFF, { 0xFFFF }, 0xFFFF }});
/* Ignore failure; should only happen with NAT */
ip_conntrack_expect_related(ct, &t, &mask, NULL);
out:
UNLOCK_BH(&ip_ftp_lock);
return NF_ACCEPT;
}
static struct ip_conntrack_helper ftp[MAX_PORTS];
/* Not __exit: called from init() */
static void fini(void)
{
int i;
for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
ports[i]);
ip_conntrack_helper_unregister(&ftp[i]);
}
}
static int __init init(void)
{
int i, ret;
if (ports[0] == 0)
ports[0] = 21;
for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
memset(&ftp[i], 0, sizeof(struct ip_conntrack_helper));
ftp[i].tuple.src.u.tcp.port = htons(ports[i]);
ftp[i].tuple.dst.protonum = IPPROTO_TCP;
ftp[i].mask.src.u.tcp.port = 0xFFFF;
ftp[i].mask.dst.protonum = 0xFFFF;
ftp[i].help = help;
DEBUGP("ip_ct_ftp: registering helper for port %d\n",
ports[i]);
ret = ip_conntrack_helper_register(&ftp[i]);
if (ret) {
fini();
return ret;
}
ports_c++;
}
return 0;
}
EXPORT_SYMBOL(ip_ftp_lock);
EXPORT_SYMBOL(ip_conntrack_ftp);
module_init(init);
module_exit(fini);
|