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- /* FTP extension for IP connection tracking. */
- /* (C) 1999-2001 Paul `Rusty' Russell
- * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.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.
- */
- #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/ip_conntrack_helper.h>
- #include <linux/netfilter_ipv4/ip_conntrack_ftp.h>
- #include <linux/moduleparam.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(ip_ftp_lock);
- #define MAX_PORTS 8
- static unsigned short ports[MAX_PORTS];
- static int ports_c;
- module_param_array(ports, ushort, &ports_c, 0400);
- static int loose;
- module_param(loose, bool, 0600);
- unsigned int (*ip_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 ip_conntrack_expect *exp,
- u32 *seq);
- EXPORT_SYMBOL_GPL(ip_nat_ftp_hook);
- #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_epsv_response(const char *, size_t, u_int32_t [], char);
- static const struct ftp_search {
- 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_MAX][2] = {
- [IP_CT_DIR_ORIGINAL] = {
- {
- .pattern = "PORT",
- .plen = sizeof("PORT") - 1,
- .skip = ' ',
- .term = '\r',
- .ftptype = IP_CT_FTP_PORT,
- .getnum = try_rfc959,
- },
- {
- .pattern = "EPRT",
- .plen = sizeof("EPRT") - 1,
- .skip = ' ',
- .term = '\r',
- .ftptype = IP_CT_FTP_EPRT,
- .getnum = try_eprt,
- },
- },
- [IP_CT_DIR_REPLY] = {
- {
- .pattern = "227 ",
- .plen = sizeof("227 ") - 1,
- .skip = '(',
- .term = ')',
- .ftptype = IP_CT_FTP_PASV,
- .getnum = try_rfc959,
- },
- {
- .pattern = "229 ",
- .plen = sizeof("229 ") - 1,
- .skip = '(',
- .term = ')',
- .ftptype = IP_CT_FTP_EPSV,
- .getnum = try_epsv_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_epsv_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++) {
- 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, array, 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;
- ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
- } else if (oldest != NUM_SEQ_TO_REMEMBER) {
- info->seq_aft_nl[dir][oldest] = nl_seq;
- ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
- }
- }
- static int help(struct sk_buff **pskb,
- struct ip_conntrack *ct,
- enum ip_conntrack_info ctinfo)
- {
- unsigned int dataoff, datalen;
- struct tcphdr _tcph, *th;
- char *fb_ptr;
- int ret;
- u32 seq, array[6] = { 0 };
- int dir = CTINFO2DIR(ctinfo);
- unsigned int matchlen, matchoff;
- struct ip_ct_ftp_master *ct_ftp_info = &ct->help.ct_ftp_info;
- struct ip_conntrack_expect *exp;
- unsigned int i;
- int found = 0, ends_in_nl;
- typeof(ip_nat_ftp_hook) ip_nat_ftp;
- /* 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, (*pskb)->nh.iph->ihl*4,
- sizeof(_tcph), &_tcph);
- if (th == NULL)
- return NF_ACCEPT;
- dataoff = (*pskb)->nh.iph->ihl*4 + th->doff*4;
- /* No data? */
- if (dataoff >= (*pskb)->len) {
- DEBUGP("ftp: pskblen = %u\n", (*pskb)->len);
- return NF_ACCEPT;
- }
- datalen = (*pskb)->len - dataoff;
- spin_lock_bh(&ip_ftp_lock);
- fb_ptr = skb_header_pointer(*pskb, dataoff,
- (*pskb)->len - dataoff, 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("ip_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
- ct_ftp_info->seq_aft_nl[0][dir]
- old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl);
- ret = NF_ACCEPT;
- goto out_update_nl;
- }
- /* 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 < ARRAY_SIZE(search[dir]); i++) {
- found = find_pattern(fb_ptr, (*pskb)->len - dataoff,
- search[dir][i].pattern,
- search[dir][i].plen,
- search[dir][i].skip,
- search[dir][i].term,
- &matchoff, &matchlen,
- array,
- search[dir][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[dir][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",
- fb_ptr + matchoff, matchlen, ntohl(th->seq) + matchoff);
- /* Allocate expectation which will be inserted */
- exp = ip_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.ip = ct->tuplehash[!dir].tuple.dst.ip;
- if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3])
- != ct->tuplehash[dir].tuple.src.ip) {
- /* 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) {
- ret = NF_ACCEPT;
- goto out_put_expect;
- }
- exp->tuple.dst.ip = htonl((array[0] << 24) | (array[1] << 16)
- | (array[2] << 8) | array[3]);
- }
- exp->tuple.src.ip = ct->tuplehash[!dir].tuple.src.ip;
- exp->tuple.dst.u.tcp.port = htons(array[4] << 8 | array[5]);
- exp->tuple.src.u.tcp.port = 0; /* Don't care. */
- exp->tuple.dst.protonum = IPPROTO_TCP;
- exp->mask = ((struct ip_conntrack_tuple)
- { { htonl(0xFFFFFFFF), { 0 } },
- { htonl(0xFFFFFFFF), { .tcp = { htons(0xFFFF) } }, 0xFF }});
- exp->expectfn = NULL;
- exp->flags = 0;
- /* Now, NAT might want to mangle the packet, and register the
- * (possibly changed) expectation itself. */
- ip_nat_ftp = rcu_dereference(ip_nat_ftp_hook);
- if (ip_nat_ftp)
- ret = ip_nat_ftp(pskb, ctinfo, search[dir][i].ftptype,
- matchoff, matchlen, exp, &seq);
- else {
- /* Can't expect this? Best to drop packet now. */
- if (ip_conntrack_expect_related(exp) != 0)
- ret = NF_DROP;
- else
- ret = NF_ACCEPT;
- }
- out_put_expect:
- ip_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(&ip_ftp_lock);
- return ret;
- }
- static struct ip_conntrack_helper ftp[MAX_PORTS];
- static char ftp_names[MAX_PORTS][sizeof("ftp-65535")];
- /* Not __exit: called from init() */
- static void ip_conntrack_ftp_fini(void)
- {
- int i;
- for (i = 0; i < ports_c; i++) {
- DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
- ports[i]);
- ip_conntrack_helper_unregister(&ftp[i]);
- }
- kfree(ftp_buffer);
- }
- static int __init ip_conntrack_ftp_init(void)
- {
- int i, ret;
- char *tmpname;
- ftp_buffer = kmalloc(65536, GFP_KERNEL);
- if (!ftp_buffer)
- return -ENOMEM;
- if (ports_c == 0)
- ports[ports_c++] = FTP_PORT;
- for (i = 0; i < ports_c; i++) {
- ftp[i].tuple.src.u.tcp.port = htons(ports[i]);
- ftp[i].tuple.dst.protonum = IPPROTO_TCP;
- ftp[i].mask.src.u.tcp.port = htons(0xFFFF);
- ftp[i].mask.dst.protonum = 0xFF;
- ftp[i].max_expected = 1;
- ftp[i].timeout = 5 * 60; /* 5 minutes */
- ftp[i].me = THIS_MODULE;
- ftp[i].help = help;
- tmpname = &ftp_names[i][0];
- if (ports[i] == FTP_PORT)
- sprintf(tmpname, "ftp");
- else
- sprintf(tmpname, "ftp-%d", ports[i]);
- ftp[i].name = tmpname;
- DEBUGP("ip_ct_ftp: registering helper for port %d\n",
- ports[i]);
- ret = ip_conntrack_helper_register(&ftp[i]);
- if (ret) {
- ip_conntrack_ftp_fini();
- return ret;
- }
- }
- return 0;
- }
- module_init(ip_conntrack_ftp_init);
- module_exit(ip_conntrack_ftp_fini);
|