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- /* 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>
- * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
- *
- * 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/moduleparam.h>
- #include <linux/netfilter.h>
- #include <linux/ip.h>
- #include <linux/slab.h>
- #include <linux/ipv6.h>
- #include <linux/ctype.h>
- #include <linux/inet.h>
- #include <net/checksum.h>
- #include <net/tcp.h>
- #include <net/netfilter/nf_conntrack.h>
- #include <net/netfilter/nf_conntrack_expect.h>
- #include <net/netfilter/nf_conntrack_ecache.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");
- MODULE_ALIAS("ip_conntrack_ftp");
- MODULE_ALIAS_NFCT_HELPER("ftp");
- /* 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 bool loose;
- module_param(loose, bool, 0600);
- unsigned int (*nf_nat_ftp_hook)(struct sk_buff *skb,
- enum ip_conntrack_info ctinfo,
- enum nf_ct_ftp_type type,
- unsigned int protoff,
- unsigned int matchoff,
- unsigned int matchlen,
- struct nf_conntrack_expect *exp);
- EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
- static int try_rfc959(const char *, size_t, struct nf_conntrack_man *,
- char, unsigned int *);
- static int try_rfc1123(const char *, size_t, struct nf_conntrack_man *,
- char, unsigned int *);
- static int try_eprt(const char *, size_t, struct nf_conntrack_man *,
- char, unsigned int *);
- static int try_epsv_response(const char *, size_t, struct nf_conntrack_man *,
- char, unsigned int *);
- static struct ftp_search {
- const char *pattern;
- size_t plen;
- char skip;
- char term;
- enum nf_ct_ftp_type ftptype;
- int (*getnum)(const char *, size_t, struct nf_conntrack_man *, char, unsigned int *);
- } search[IP_CT_DIR_MAX][2] = {
- [IP_CT_DIR_ORIGINAL] = {
- {
- .pattern = "PORT",
- .plen = sizeof("PORT") - 1,
- .skip = ' ',
- .term = '\r',
- .ftptype = NF_CT_FTP_PORT,
- .getnum = try_rfc959,
- },
- {
- .pattern = "EPRT",
- .plen = sizeof("EPRT") - 1,
- .skip = ' ',
- .term = '\r',
- .ftptype = NF_CT_FTP_EPRT,
- .getnum = try_eprt,
- },
- },
- [IP_CT_DIR_REPLY] = {
- {
- .pattern = "227 ",
- .plen = sizeof("227 ") - 1,
- .ftptype = NF_CT_FTP_PASV,
- .getnum = try_rfc1123,
- },
- {
- .pattern = "229 ",
- .plen = sizeof("229 ") - 1,
- .skip = '(',
- .term = ')',
- .ftptype = NF_CT_FTP_EPSV,
- .getnum = try_epsv_response,
- },
- },
- };
- static int
- get_ipv6_addr(const char *src, size_t dlen, struct in6_addr *dst, u_int8_t term)
- {
- const char *end;
- int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
- if (ret > 0)
- return (int)(end - src);
- return 0;
- }
- 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 (or we don't care about one)
- and we're finished. */
- if ((*data == term || !term) && i == array_size - 1)
- return len;
- pr_debug("Char %u (got %u nums) `%u' unexpected\n",
- len, i, *data);
- return 0;
- }
- }
- pr_debug("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,
- unsigned int *offset)
- {
- 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;
- }
- /*
- * From RFC 1123:
- * The format of the 227 reply to a PASV command is not
- * well standardized. In particular, an FTP client cannot
- * assume that the parentheses shown on page 40 of RFC-959
- * will be present (and in fact, Figure 3 on page 43 omits
- * them). Therefore, a User-FTP program that interprets
- * the PASV reply must scan the reply for the first digit
- * of the host and port numbers.
- */
- static int try_rfc1123(const char *data, size_t dlen,
- struct nf_conntrack_man *cmd, char term,
- unsigned int *offset)
- {
- int i;
- for (i = 0; i < dlen; i++)
- if (isdigit(data[i]))
- break;
- if (i == dlen)
- return 0;
- *offset += i;
- return try_rfc959(data + i, dlen - i, cmd, 0, offset);
- }
- /* Grab port: number up to delimiter */
- static int get_port(const char *data, int start, size_t dlen, char delim,
- __be16 *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);
- pr_debug("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 */
- pr_debug("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, unsigned int *offset)
- {
- char delim;
- int length;
- /* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
- then delimiter again. */
- if (dlen <= 3) {
- pr_debug("EPRT: too short\n");
- return 0;
- }
- delim = data[0];
- if (isdigit(delim) || delim < 33 || delim > 126 || data[2] != delim) {
- pr_debug("try_eprt: invalid delimitter.\n");
- return 0;
- }
- if ((cmd->l3num == PF_INET && data[1] != '1') ||
- (cmd->l3num == PF_INET6 && data[1] != '2')) {
- pr_debug("EPRT: invalid protocol number.\n");
- return 0;
- }
- pr_debug("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;
- pr_debug("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,
- unsigned int *offset)
- {
- 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,
- unsigned int *))
- {
- size_t i = plen;
- pr_debug("find_pattern `%s': dlen = %Zu\n", pattern, dlen);
- if (dlen == 0)
- return 0;
- if (dlen <= plen) {
- /* Short packet: try for partial? */
- if (strncasecmp(data, pattern, dlen) == 0)
- return -1;
- else return 0;
- }
- if (strncasecmp(data, pattern, plen) != 0) {
- #if 0
- size_t i;
- pr_debug("ftp: string mismatch\n");
- for (i = 0; i < plen; i++) {
- pr_debug("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
- i, data[i], data[i],
- pattern[i], pattern[i]);
- }
- #endif
- return 0;
- }
- pr_debug("Pattern matches!\n");
- /* Now we've found the constant string, try to skip
- to the 'skip' character */
- if (skip) {
- for (i = plen; data[i] != skip; i++)
- if (i == dlen - 1) return -1;
- /* Skip over the last character */
- i++;
- }
- pr_debug("Skipped up to `%c'!\n", skip);
- *numoff = i;
- *numlen = getnum(data + i, dlen - i, cmd, term, numoff);
- if (!*numlen)
- return -1;
- pr_debug("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 nf_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(struct nf_conn *ct, u32 nl_seq,
- struct nf_ct_ftp_master *info, int dir,
- struct sk_buff *skb)
- {
- unsigned int i, oldest;
- /* 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 (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
- info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
- } else {
- if (before(info->seq_aft_nl[dir][0], info->seq_aft_nl[dir][1]))
- oldest = 0;
- else
- oldest = 1;
- if (after(nl_seq, info->seq_aft_nl[dir][oldest]))
- info->seq_aft_nl[dir][oldest] = nl_seq;
- }
- }
- static int help(struct sk_buff *skb,
- unsigned int protoff,
- struct nf_conn *ct,
- enum ip_conntrack_info ctinfo)
- {
- unsigned int dataoff, datalen;
- const struct tcphdr *th;
- struct tcphdr _tcph;
- const char *fb_ptr;
- int ret;
- u32 seq;
- int dir = CTINFO2DIR(ctinfo);
- unsigned int uninitialized_var(matchlen), uninitialized_var(matchoff);
- struct nf_ct_ftp_master *ct_ftp_info = nfct_help_data(ct);
- struct nf_conntrack_expect *exp;
- union nf_inet_addr *daddr;
- struct nf_conntrack_man cmd = {};
- unsigned int i;
- int found = 0, ends_in_nl;
- typeof(nf_nat_ftp_hook) nf_nat_ftp;
- /* Until there's been traffic both ways, don't look in packets. */
- if (ctinfo != IP_CT_ESTABLISHED &&
- ctinfo != IP_CT_ESTABLISHED_REPLY) {
- pr_debug("ftp: Conntrackinfo = %u\n", ctinfo);
- return NF_ACCEPT;
- }
- th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
- if (th == NULL)
- return NF_ACCEPT;
- dataoff = protoff + th->doff * 4;
- /* No data? */
- if (dataoff >= skb->len) {
- pr_debug("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
- skb->len);
- return NF_ACCEPT;
- }
- datalen = skb->len - dataoff;
- spin_lock_bh(&nf_ftp_lock);
- fb_ptr = skb_header_pointer(skb, 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)) {
- /* We're picking up this, clear flags and let it continue */
- if (unlikely(ct_ftp_info->flags[dir] & NF_CT_FTP_SEQ_PICKUP)) {
- ct_ftp_info->flags[dir] ^= NF_CT_FTP_SEQ_PICKUP;
- goto skip_nl_seq;
- }
- /* Now if this ends in \n, update ftp info. */
- pr_debug("nf_conntrack_ftp: 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;
- }
- skip_nl_seq:
- /* Initialize IP/IPv6 addr to expected address (it's not mentioned
- in EPSV responses) */
- cmd.l3num = nf_ct_l3num(ct);
- memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
- sizeof(cmd.u3.all));
- for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
- found = find_pattern(fb_ptr, datalen,
- search[dir][i].pattern,
- search[dir][i].plen,
- search[dir][i].skip,
- search[dir][i].term,
- &matchoff, &matchlen,
- &cmd,
- 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. */
- nf_ct_helper_log(skb, ct, "partial matching of `%s'",
- search[dir][i].pattern);
- ret = NF_DROP;
- goto out;
- } else if (found == 0) { /* No match */
- ret = NF_ACCEPT;
- goto out_update_nl;
- }
- pr_debug("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
- matchlen, fb_ptr + matchoff,
- matchlen, ntohl(th->seq) + matchoff);
- exp = nf_ct_expect_alloc(ct);
- if (exp == NULL) {
- nf_ct_helper_log(skb, ct, "cannot alloc expectation");
- 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. */
- daddr = &ct->tuplehash[!dir].tuple.dst.u3;
- /* Update the ftp info */
- if ((cmd.l3num == nf_ct_l3num(ct)) &&
- 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) {
- pr_debug("conntrack_ftp: NOT RECORDING: %pI4 != %pI4\n",
- &cmd.u3.ip,
- &ct->tuplehash[dir].tuple.src.u3.ip);
- } else {
- pr_debug("conntrack_ftp: NOT RECORDING: %pI6 != %pI6\n",
- cmd.u3.ip6,
- 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;
- }
- daddr = &cmd.u3;
- }
- nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, cmd.l3num,
- &ct->tuplehash[!dir].tuple.src.u3, daddr,
- IPPROTO_TCP, NULL, &cmd.u.tcp.port);
- /* Now, NAT might want to mangle the packet, and register the
- * (possibly changed) expectation itself. */
- nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
- if (nf_nat_ftp && ct->status & IPS_NAT_MASK)
- ret = nf_nat_ftp(skb, ctinfo, search[dir][i].ftptype,
- protoff, matchoff, matchlen, exp);
- else {
- /* Can't expect this? Best to drop packet now. */
- if (nf_ct_expect_related(exp) != 0) {
- nf_ct_helper_log(skb, ct, "cannot add expectation");
- ret = NF_DROP;
- } else
- ret = NF_ACCEPT;
- }
- out_put_expect:
- nf_ct_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(ct, seq, ct_ftp_info, dir, skb);
- out:
- spin_unlock_bh(&nf_ftp_lock);
- return ret;
- }
- static int nf_ct_ftp_from_nlattr(struct nlattr *attr, struct nf_conn *ct)
- {
- struct nf_ct_ftp_master *ftp = nfct_help_data(ct);
- /* This conntrack has been injected from user-space, always pick up
- * sequence tracking. Otherwise, the first FTP command after the
- * failover breaks.
- */
- ftp->flags[IP_CT_DIR_ORIGINAL] |= NF_CT_FTP_SEQ_PICKUP;
- ftp->flags[IP_CT_DIR_REPLY] |= NF_CT_FTP_SEQ_PICKUP;
- return 0;
- }
- static struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
- static const struct nf_conntrack_expect_policy ftp_exp_policy = {
- .max_expected = 1,
- .timeout = 5 * 60,
- };
- /* don't make this __exit, since it's called from __init ! */
- static void nf_conntrack_ftp_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;
- pr_debug("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 nf_conntrack_ftp_init(void)
- {
- int i, j = -1, ret = 0;
- 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++) {
- 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].data_len = sizeof(struct nf_ct_ftp_master);
- ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
- ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
- ftp[i][j].expect_policy = &ftp_exp_policy;
- ftp[i][j].me = THIS_MODULE;
- ftp[i][j].help = help;
- ftp[i][j].from_nlattr = nf_ct_ftp_from_nlattr;
- if (ports[i] == FTP_PORT)
- sprintf(ftp[i][j].name, "ftp");
- else
- sprintf(ftp[i][j].name, "ftp-%d", ports[i]);
- pr_debug("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(KERN_ERR "nf_ct_ftp: failed to register"
- " helper for pf: %d port: %d\n",
- ftp[i][j].tuple.src.l3num, ports[i]);
- nf_conntrack_ftp_fini();
- return ret;
- }
- }
- }
- return 0;
- }
- module_init(nf_conntrack_ftp_init);
- module_exit(nf_conntrack_ftp_fini);
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