blob: 65080e269f27477430c9aa9a72ac6838f6164eca [file] [log] [blame]
/* FTP extension for connection tracking. */
/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
* (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
* - enable working with Layer 3 protocol independent connection tracking.
* - track EPRT and EPSV commands with IPv6 address.
*
* Derived from net/ipv4/netfilter/ip_conntrack_ftp.c
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/netfilter.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/ctype.h>
#include <net/checksum.h>
#include <net/tcp.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <linux/netfilter/nf_conntrack_ftp.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
MODULE_DESCRIPTION("ftp connection tracking helper");
/* This is slow, but it's simple. --RR */
static char *ftp_buffer;
static DEFINE_SPINLOCK(nf_ftp_lock);
#define MAX_PORTS 8
static u_int16_t ports[MAX_PORTS];
static unsigned int ports_c;
module_param_array(ports, ushort, &ports_c, 0400);
static int loose;
module_param(loose, int, 0600);
unsigned int (*nf_nat_ftp_hook)(struct sk_buff **pskb,
enum ip_conntrack_info ctinfo,
enum ip_ct_ftp_type type,
unsigned int matchoff,
unsigned int matchlen,
struct nf_conntrack_expect *exp,
u32 *seq);
EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif
static int try_rfc959(const char *, size_t, struct nf_conntrack_man *, char);
static int try_eprt(const char *, size_t, struct nf_conntrack_man *, char);
static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
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, struct nf_conntrack_man *, 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_epsv_response,
},
};
/* This code is based on inet_pton() in glibc-2.2.4 */
static int
get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
{
static const char xdigits[] = "0123456789abcdef";
u_int8_t tmp[16], *tp, *endp, *colonp;
int ch, saw_xdigit;
u_int32_t val;
size_t clen = 0;
tp = memset(tmp, '\0', sizeof(tmp));
endp = tp + sizeof(tmp);
colonp = NULL;
/* Leading :: requires some special handling. */
if (*src == ':'){
if (*++src != ':') {
DEBUGP("invalid \":\" at the head of addr\n");
return 0;
}
clen++;
}
saw_xdigit = 0;
val = 0;
while ((clen < dlen) && (*src != term)) {
const char *pch;
ch = tolower(*src++);
clen++;
pch = strchr(xdigits, ch);
if (pch != NULL) {
val <<= 4;
val |= (pch - xdigits);
if (val > 0xffff)
return 0;
saw_xdigit = 1;
continue;
}
if (ch != ':') {
DEBUGP("get_ipv6_addr: invalid char. \'%c\'\n", ch);
return 0;
}
if (!saw_xdigit) {
if (colonp) {
DEBUGP("invalid location of \"::\".\n");
return 0;
}
colonp = tp;
continue;
} else if (*src == term) {
DEBUGP("trancated IPv6 addr\n");
return 0;
}
if (tp + 2 > endp)
return 0;
*tp++ = (u_int8_t) (val >> 8) & 0xff;
*tp++ = (u_int8_t) val & 0xff;
saw_xdigit = 0;
val = 0;
continue;
}
if (saw_xdigit) {
if (tp + 2 > endp)
return 0;
*tp++ = (u_int8_t) (val >> 8) & 0xff;
*tp++ = (u_int8_t) val & 0xff;
}
if (colonp != NULL) {
/*
* Since some memmove()'s erroneously fail to handle
* overlapping regions, we'll do the shift by hand.
*/
const int n = tp - colonp;
int i;
if (tp == endp)
return 0;
for (i = 1; i <= n; i++) {
endp[- i] = colonp[n - i];
colonp[n - i] = 0;
}
tp = endp;
}
if (tp != endp || (*src != term))
return 0;
memcpy(dst->s6_addr, tmp, sizeof(dst->s6_addr));
return clen;
}
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,
struct nf_conntrack_man *cmd, char term)
{
int length;
u_int32_t array[6];
length = try_number(data, dlen, array, 6, ',', term);
if (length == 0)
return 0;
cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16) |
(array[2] << 8) | array[3]);
cmd->u.tcp.port = htons((array[4] << 8) | array[5]);
return length;
}
/* Grab port: number up to delimiter */
static int get_port(const char *data, int start, size_t dlen, char delim,
u_int16_t *port)
{
u_int16_t tmp_port = 0;
int i;
for (i = start; i < dlen; i++) {
/* Finished? */
if (data[i] == delim) {
if (tmp_port == 0)
break;
*port = htons(tmp_port);
DEBUGP("get_port: return %d\n", tmp_port);
return i + 1;
}
else if (data[i] >= '0' && data[i] <= '9')
tmp_port = tmp_port*10 + data[i] - '0';
else { /* Some other crap */
DEBUGP("get_port: invalid char.\n");
break;
}
}
return 0;
}
/* Returns 0, or length of numbers: |1|132.235.1.2|6275| or |2|3ffe::1|6275| */
static int try_eprt(const char *data, size_t dlen, struct nf_conntrack_man *cmd,
char term)
{
char delim;
int length;
/* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
then delimiter again. */
if (dlen <= 3) {
DEBUGP("EPRT: too short\n");
return 0;
}
delim = data[0];
if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
DEBUGP("try_eprt: invalid delimitter.\n");
return 0;
}
if ((cmd->l3num == PF_INET && data[1] != '1') ||
(cmd->l3num == PF_INET6 && data[1] != '2')) {
DEBUGP("EPRT: invalid protocol number.\n");
return 0;
}
DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
if (data[1] == '1') {
u_int32_t array[4];
/* Now we have IP address. */
length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
if (length != 0)
cmd->u3.ip = htonl((array[0] << 24) | (array[1] << 16)
| (array[2] << 8) | array[3]);
} else {
/* Now we have IPv6 address. */
length = get_ipv6_addr(data + 3, dlen - 3,
(struct in6_addr *)cmd->u3.ip6, 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, &cmd->u.tcp.port);
}
/* Returns 0, or length of numbers: |||6446| */
static int try_epsv_response(const char *data, size_t dlen,
struct nf_conntrack_man *cmd, 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, &cmd->u.tcp.port);
}
/* 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,
struct nf_conntrack_man *cmd,
int (*getnum)(const char *, size_t,
struct nf_conntrack_man *, 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++) {
DEBUGP("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, cmd, term);
if (!*numlen)
return -1;
DEBUGP("Match succeeded!\n");
return 1;
}
/* Look up to see if we're just after a \n. */
static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
{
unsigned int i;
for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
if (info->seq_aft_nl[dir][i] == seq)
return 1;
return 0;
}
/* We don't update if it's older than what we have. */
static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
struct sk_buff *skb)
{
unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
/* Look for oldest: if we find exact match, we're done. */
for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
if (info->seq_aft_nl[dir][i] == nl_seq)
return;
if (oldest == info->seq_aft_nl_num[dir]
|| before(info->seq_aft_nl[dir][i], oldest))
oldest = i;
}
if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
} else if (oldest != NUM_SEQ_TO_REMEMBER) {
info->seq_aft_nl[dir][oldest] = nl_seq;
nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
}
}
static int help(struct sk_buff **pskb,
unsigned int protoff,
struct nf_conn *ct,
enum ip_conntrack_info ctinfo)
{
unsigned int dataoff, datalen;
struct tcphdr _tcph, *th;
char *fb_ptr;
int ret;
u32 seq;
int dir = CTINFO2DIR(ctinfo);
unsigned int matchlen, matchoff;
struct ip_ct_ftp_master *ct_ftp_info = &ct->help->ct_ftp_info;
struct nf_conntrack_expect *exp;
struct nf_conntrack_man cmd = {};
unsigned int i;
int found = 0, ends_in_nl;
/* 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;
}
th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
if (th == NULL)
return NF_ACCEPT;
dataoff = protoff + th->doff * 4;
/* No data? */
if (dataoff >= (*pskb)->len) {
DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
(*pskb)->len);
return NF_ACCEPT;
}
datalen = (*pskb)->len - dataoff;
spin_lock_bh(&nf_ftp_lock);
fb_ptr = skb_header_pointer(*pskb, dataoff, datalen, ftp_buffer);
BUG_ON(fb_ptr == NULL);
ends_in_nl = (fb_ptr[datalen - 1] == '\n');
seq = ntohl(th->seq) + datalen;
/* Look up to see if we're just after a \n. */
if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
/* Now if this ends in \n, update ftp info. */
DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
ct_ftp_info->seq_aft_nl[dir][0],
ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
ct_ftp_info->seq_aft_nl[dir][1]);
ret = NF_ACCEPT;
goto out_update_nl;
}
/* Initialize IP/IPv6 addr to expected address (it's not mentioned
in EPSV responses) */
cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
sizeof(cmd.u3.all));
for (i = 0; i < ARRAY_SIZE(search); i++) {
if (search[i].dir != dir) continue;
found = find_pattern(fb_ptr, datalen,
search[i].pattern,
search[i].plen,
search[i].skip,
search[i].term,
&matchoff, &matchlen,
&cmd,
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 necessary for accurate tracking in
this case. */
if (net_ratelimit())
printk("conntrack_ftp: partial %s %u+%u\n",
search[i].pattern,
ntohl(th->seq), datalen);
ret = NF_DROP;
goto out;
} else if (found == 0) { /* No match */
ret = NF_ACCEPT;
goto out_update_nl;
}
DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
(int)matchlen, fb_ptr + matchoff,
matchlen, ntohl(th->seq) + matchoff);
exp = nf_conntrack_expect_alloc(ct);
if (exp == NULL) {
ret = NF_DROP;
goto out;
}
/* We refer to the reverse direction ("!dir") tuples here,
* because we're expecting something in the other direction.
* Doesn't matter unless NAT is happening. */
exp->tuple.dst.u3 = ct->tuplehash[!dir].tuple.dst.u3;
/* Update the ftp info */
if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
sizeof(cmd.u3.all))) {
/* 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. */
if (cmd.l3num == PF_INET) {
DEBUGP("conntrack_ftp: NOT RECORDING: %u,%u,%u,%u != %u.%u.%u.%u\n",
NIPQUAD(cmd.u3.ip),
NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
} else {
DEBUGP("conntrack_ftp: NOT RECORDING: %x:%x:%x:%x:%x:%x:%x:%x != %x:%x:%x:%x:%x:%x:%x:%x\n",
NIP6(*((struct in6_addr *)cmd.u3.ip6)),
NIP6(*((struct in6_addr *)ct->tuplehash[dir]
.tuple.src.u3.ip6)));
}
/* 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) {
ret = NF_ACCEPT;
goto out_put_expect;
}
memcpy(&exp->tuple.dst.u3, &cmd.u3.all,
sizeof(exp->tuple.dst.u3));
}
exp->tuple.src.u3 = ct->tuplehash[!dir].tuple.src.u3;
exp->tuple.src.l3num = cmd.l3num;
exp->tuple.src.u.tcp.port = 0;
exp->tuple.dst.u.tcp.port = cmd.u.tcp.port;
exp->tuple.dst.protonum = IPPROTO_TCP;
exp->mask = (struct nf_conntrack_tuple)
{ .src = { .l3num = 0xFFFF,
.u = { .tcp = { 0 }},
},
.dst = { .protonum = 0xFF,
.u = { .tcp = { 0xFFFF }},
},
};
if (cmd.l3num == PF_INET) {
exp->mask.src.u3.ip = 0xFFFFFFFF;
exp->mask.dst.u3.ip = 0xFFFFFFFF;
} else {
memset(exp->mask.src.u3.ip6, 0xFF,
sizeof(exp->mask.src.u3.ip6));
memset(exp->mask.dst.u3.ip6, 0xFF,
sizeof(exp->mask.src.u3.ip6));
}
exp->expectfn = NULL;
exp->flags = 0;
/* Now, NAT might want to mangle the packet, and register the
* (possibly changed) expectation itself. */
if (nf_nat_ftp_hook)
ret = nf_nat_ftp_hook(pskb, ctinfo, search[i].ftptype,
matchoff, matchlen, exp, &seq);
else {
/* Can't expect this? Best to drop packet now. */
if (nf_conntrack_expect_related(exp) != 0)
ret = NF_DROP;
else
ret = NF_ACCEPT;
}
out_put_expect:
nf_conntrack_expect_put(exp);
out_update_nl:
/* Now if this ends in \n, update ftp info. Seq may have been
* adjusted by NAT code. */
if (ends_in_nl)
update_nl_seq(seq, ct_ftp_info, dir, *pskb);
out:
spin_unlock_bh(&nf_ftp_lock);
return ret;
}
static struct nf_conntrack_helper ftp[MAX_PORTS][2];
static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")];
/* don't make this __exit, since it's called from __init ! */
static void fini(void)
{
int i, j;
for (i = 0; i < ports_c; i++) {
for (j = 0; j < 2; j++) {
if (ftp[i][j].me == NULL)
continue;
DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
"port: %d\n",
ftp[i][j].tuple.src.l3num, ports[i]);
nf_conntrack_helper_unregister(&ftp[i][j]);
}
}
kfree(ftp_buffer);
}
static int __init init(void)
{
int i, j = -1, ret = 0;
char *tmpname;
ftp_buffer = kmalloc(65536, GFP_KERNEL);
if (!ftp_buffer)
return -ENOMEM;
if (ports_c == 0)
ports[ports_c++] = FTP_PORT;
/* FIXME should be configurable whether IPv4 and IPv6 FTP connections
are tracked or not - YK */
for (i = 0; i < ports_c; i++) {
memset(&ftp[i], 0, sizeof(struct nf_conntrack_helper));
ftp[i][0].tuple.src.l3num = PF_INET;
ftp[i][1].tuple.src.l3num = PF_INET6;
for (j = 0; j < 2; j++) {
ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
ftp[i][j].mask.src.u.tcp.port = 0xFFFF;
ftp[i][j].mask.dst.protonum = 0xFF;
ftp[i][j].max_expected = 1;
ftp[i][j].timeout = 5 * 60; /* 5 Minutes */
ftp[i][j].me = THIS_MODULE;
ftp[i][j].help = help;
tmpname = &ftp_names[i][j][0];
if (ports[i] == FTP_PORT)
sprintf(tmpname, "ftp");
else
sprintf(tmpname, "ftp-%d", ports[i]);
ftp[i][j].name = tmpname;
DEBUGP("nf_ct_ftp: registering helper for pf: %d "
"port: %d\n",
ftp[i][j].tuple.src.l3num, ports[i]);
ret = nf_conntrack_helper_register(&ftp[i][j]);
if (ret) {
printk("nf_ct_ftp: failed to register helper "
" for pf: %d port: %d\n",
ftp[i][j].tuple.src.l3num, ports[i]);
fini();
return ret;
}
}
}
return 0;
}
module_init(init);
module_exit(fini);