[mirror_ubuntu-bionic-kernel.git] / net / netfilter / nf_conntrack_ftp.c

/* 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/module.h>
#include <linux/moduleparam.h>
#include <linux/netfilter.h>
#include <linux/ip.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");

/* 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, bool, 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 {
	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_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
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 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,
		    __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);
			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 = &nfct_help(ct)->help.ct_ftp_info;
	struct nf_conntrack_expect *exp;
	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+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[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. */
		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",
	       (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: " NIPQUAD_FMT " != " NIPQUAD_FMT "\n",
			       NIPQUAD(cmd.u3.ip),
			       NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
		} else {
			DEBUGP("conntrack_ftp: NOT RECORDING: " NIP6_FMT " != " NIP6_FMT "\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 = { __constant_htons(0xFFFF) }},
			     },
		    };
	if (cmd.l3num == PF_INET) {
		exp->mask.src.u3.ip = htonl(0xFFFFFFFF);
		exp->mask.dst.u3.ip = htonl(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->helper = NULL;
	exp->flags = 0;

	/* 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)
		ret = nf_nat_ftp(pskb, ctinfo, search[dir][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 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;

			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 nf_conntrack_ftp_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++) {
		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.l3num = 0xFFFF;
			ftp[i][j].mask.src.u.tcp.port = htons(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]);
				nf_conntrack_ftp_fini();
				return ret;
			}
		}
	}

	return 0;
}

module_init(nf_conntrack_ftp_init);
module_exit(nf_conntrack_ftp_fini);
Commit	Line	Data
9fb9cbb1 YK	1	/* FTP extension for connection tracking. */
	2
	3	/* (C) 1999-2001 Paul `Rusty' Russell
	4	* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
	5	* (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
	6	*
	7	* This program is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU General Public License version 2 as
	9	* published by the Free Software Foundation.
	10	*
	11	* 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
	12	* - enable working with Layer 3 protocol independent connection tracking.
	13	* - track EPRT and EPSV commands with IPv6 address.
	14	*
	15	* Derived from net/ipv4/netfilter/ip_conntrack_ftp.c
	16	*/
	17
9fb9cbb1 YK	18	#include <linux/module.h>
	19	#include <linux/moduleparam.h>
	20	#include <linux/netfilter.h>
	21	#include <linux/ip.h>
	22	#include <linux/ipv6.h>
	23	#include <linux/ctype.h>
6a28ec8c	24	#include <linux/inet.h>
9fb9cbb1 YK	25	#include <net/checksum.h>
	26	#include <net/tcp.h>
	27
	28	#include <net/netfilter/nf_conntrack.h>
77ab9cff	29	#include <net/netfilter/nf_conntrack_expect.h>
f6180121	30	#include <net/netfilter/nf_conntrack_ecache.h>
9fb9cbb1 YK	31	#include <net/netfilter/nf_conntrack_helper.h>
	32	#include <linux/netfilter/nf_conntrack_ftp.h>
	33
	34	MODULE_LICENSE("GPL");
	35	MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
	36	MODULE_DESCRIPTION("ftp connection tracking helper");
d2483dde	37	MODULE_ALIAS("ip_conntrack_ftp");
9fb9cbb1 YK	38
	39	/* This is slow, but it's simple. --RR */
	40	static char *ftp_buffer;
	41
	42	static DEFINE_SPINLOCK(nf_ftp_lock);
	43
	44	#define MAX_PORTS 8
	45	static u_int16_t ports[MAX_PORTS];
	46	static unsigned int ports_c;
	47	module_param_array(ports, ushort, &ports_c, 0400);
	48
	49	static int loose;
e7be6994	50	module_param(loose, bool, 0600);
9fb9cbb1 YK	51
	52	unsigned int (nf_nat_ftp_hook)(struct sk_buff *pskb,
	53	enum ip_conntrack_info ctinfo,
	54	enum ip_ct_ftp_type type,
	55	unsigned int matchoff,
	56	unsigned int matchlen,
	57	struct nf_conntrack_expect *exp,
	58	u32 *seq);
	59	EXPORT_SYMBOL_GPL(nf_nat_ftp_hook);
	60
	61	#if 0
	62	#define DEBUGP printk
	63	#else
	64	#define DEBUGP(format, args...)
	65	#endif
	66
	67	static int try_rfc959(const char , size_t, struct nf_conntrack_man , char);
	68	static int try_eprt(const char , size_t, struct nf_conntrack_man , char);
	69	static int try_epsv_response(const char , size_t, struct nf_conntrack_man ,
	70	char);
	71
	72	static struct ftp_search {
9fb9cbb1 YK	73	const char *pattern;
	74	size_t plen;
	75	char skip;
	76	char term;
	77	enum ip_ct_ftp_type ftptype;
	78	int (getnum)(const char , size_t, struct nf_conntrack_man *, char);
7d8c5018 PM	79	} search[IP_CT_DIR_MAX][2] = {
	80	[IP_CT_DIR_ORIGINAL] = {
	81	{
	82	.pattern = "PORT",
	83	.plen = sizeof("PORT") - 1,
	84	.skip = ' ',
	85	.term = '\r',
	86	.ftptype = IP_CT_FTP_PORT,
	87	.getnum = try_rfc959,
	88	},
	89	{
	90	.pattern = "EPRT",
	91	.plen = sizeof("EPRT") - 1,
	92	.skip = ' ',
	93	.term = '\r',
	94	.ftptype = IP_CT_FTP_EPRT,
	95	.getnum = try_eprt,
	96	},
9fb9cbb1	97	},
7d8c5018 PM	98	[IP_CT_DIR_REPLY] = {
	99	{
	100	.pattern = "227 ",
	101	.plen = sizeof("227 ") - 1,
	102	.skip = '(',
	103	.term = ')',
	104	.ftptype = IP_CT_FTP_PASV,
	105	.getnum = try_rfc959,
	106	},
	107	{
	108	.pattern = "229 ",
	109	.plen = sizeof("229 ") - 1,
	110	.skip = '(',
	111	.term = ')',
	112	.ftptype = IP_CT_FTP_EPSV,
	113	.getnum = try_epsv_response,
	114	},
9fb9cbb1 YK	115	},
	116	};
	117
9fb9cbb1 YK	118	static int
	119	get_ipv6_addr(const char src, size_t dlen, struct in6_addr dst, u_int8_t term)
	120	{
6a28ec8c DM	121	const char *end;
6a28ec8c DM	122	int ret = in6_pton(src, min_t(size_t, dlen, 0xffff), (u8 *)dst, term, &end);
1884f78c YH	123	if (ret > 0)
	124	return (int)(end - src);
	125	return 0;
9fb9cbb1 YK	126	}
	127
	128	static int try_number(const char *data, size_t dlen, u_int32_t array[],
	129	int array_size, char sep, char term)
	130	{
	131	u_int32_t i, len;
	132
	133	memset(array, 0, sizeof(array[0])*array_size);
	134
	135	/* Keep data pointing at next char. */
	136	for (i = 0, len = 0; len < dlen && i < array_size; len++, data++) {
	137	if (data >= '0' && data <= '9') {
	138	array[i] = array[i]10 + data - '0';
	139	}
	140	else if (*data == sep)
	141	i++;
	142	else {
	143	/* Unexpected character; true if it's the
	144	terminator and we're finished. */
	145	if (*data == term && i == array_size - 1)
	146	return len;
	147
	148	DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
	149	len, i, *data);
	150	return 0;
	151	}
	152	}
	153	DEBUGP("Failed to fill %u numbers separated by %c\n", array_size, sep);
	154
	155	return 0;
	156	}
	157
	158	/* Returns 0, or length of numbers: 192,168,1,1,5,6 */
	159	static int try_rfc959(const char *data, size_t dlen,
	160	struct nf_conntrack_man *cmd, char term)
	161	{
	162	int length;
	163	u_int32_t array[6];
	164
	165	length = try_number(data, dlen, array, 6, ',', term);
	166	if (length == 0)
	167	return 0;
	168
	169	cmd->u3.ip = htonl((array[0] << 24) \| (array[1] << 16) \|
	170	(array[2] << 8) \| array[3]);
	171	cmd->u.tcp.port = htons((array[4] << 8) \| array[5]);
	172	return length;
	173	}
	174
	175	/* Grab port: number up to delimiter */
	176	static int get_port(const char *data, int start, size_t dlen, char delim,
bff9a89b	177	__be16 *port)
9fb9cbb1 YK	178	{
	179	u_int16_t tmp_port = 0;
	180	int i;
	181
	182	for (i = start; i < dlen; i++) {
	183	/* Finished? */
	184	if (data[i] == delim) {
	185	if (tmp_port == 0)
	186	break;
	187	*port = htons(tmp_port);
	188	DEBUGP("get_port: return %d\n", tmp_port);
	189	return i + 1;
	190	}
	191	else if (data[i] >= '0' && data[i] <= '9')
	192	tmp_port = tmp_port*10 + data[i] - '0';
	193	else { /* Some other crap */
	194	DEBUGP("get_port: invalid char.\n");
	195	break;
	196	}
	197	}
	198	return 0;
	199	}
	200
	201	/* Returns 0, or length of numbers: \|1\|132.235.1.2\|6275\| or \|2\|3ffe::1\|6275\| */
	202	static int try_eprt(const char data, size_t dlen, struct nf_conntrack_man cmd,
	203	char term)
	204	{
	205	char delim;
	206	int length;
	207
	208	/* First character is delimiter, then "1" for IPv4 or "2" for IPv6,
	209	then delimiter again. */
	210	if (dlen <= 3) {
	211	DEBUGP("EPRT: too short\n");
	212	return 0;
	213	}
	214	delim = data[0];
	215	if (isdigit(delim) \|\| delim < 33 \|\| delim > 126 \|\| data[2] != delim) {
	216	DEBUGP("try_eprt: invalid delimitter.\n");
	217	return 0;
	218	}
	219
	220	if ((cmd->l3num == PF_INET && data[1] != '1') \|\|
	221	(cmd->l3num == PF_INET6 && data[1] != '2')) {
	222	DEBUGP("EPRT: invalid protocol number.\n");
	223	return 0;
	224	}
	225
	226	DEBUGP("EPRT: Got %c%c%c\n", delim, data[1], delim);
	227
	228	if (data[1] == '1') {
	229	u_int32_t array[4];
	230
	231	/* Now we have IP address. */
	232	length = try_number(data + 3, dlen - 3, array, 4, '.', delim);
	233	if (length != 0)
	234	cmd->u3.ip = htonl((array[0] << 24) \| (array[1] << 16)
	235	\| (array[2] << 8) \| array[3]);
	236	} else {
	237	/* Now we have IPv6 address. */
	238	length = get_ipv6_addr(data + 3, dlen - 3,
	239	(struct in6_addr *)cmd->u3.ip6, delim);
	240	}
	241
242	if (length == 0)
243	return 0;
244	DEBUGP("EPRT: Got IP address!\n");
245	/* Start offset includes initial "\|1\|", and trailing delimiter */
246	return get_port(data, 3 + length + 1, dlen, delim, &cmd->u.tcp.port);
247	}
248
249	/* Returns 0, or length of numbers: \|\|\|6446\| */
250	static int try_epsv_response(const char *data, size_t dlen,
251	struct nf_conntrack_man *cmd, char term)
252	{
253	char delim;
254
255	/* Three delimiters. */
256	if (dlen <= 3) return 0;
257	delim = data[0];
258	if (isdigit(delim) \|\| delim < 33 \|\| delim > 126
259	\|\| data[1] != delim \|\| data[2] != delim)
260	return 0;
261
262	return get_port(data, 3, dlen, delim, &cmd->u.tcp.port);
263	}
264
265	/* Return 1 for match, 0 for accept, -1 for partial. */
266	static int find_pattern(const char *data, size_t dlen,
267	const char *pattern, size_t plen,
268	char skip, char term,
269	unsigned int *numoff,
270	unsigned int *numlen,
271	struct nf_conntrack_man *cmd,
272	int (getnum)(const char , size_t,
273	struct nf_conntrack_man *, char))
274	{
275	size_t i;
276
277	DEBUGP("find_pattern `%s': dlen = %u\n", pattern, dlen);
278	if (dlen == 0)
279	return 0;
280
281	if (dlen <= plen) {
282	/* Short packet: try for partial? */
283	if (strnicmp(data, pattern, dlen) == 0)
284	return -1;
285	else return 0;
286	}
287
288	if (strnicmp(data, pattern, plen) != 0) {
289	#if 0
290	size_t i;
291
292	DEBUGP("ftp: string mismatch\n");
293	for (i = 0; i < plen; i++) {
294	DEBUGP("ftp:char %u `%c'(%u) vs `%c'(%u)\n",
295	i, data[i], data[i],
296	pattern[i], pattern[i]);
297	}
298	#endif
299	return 0;
300	}
301
302	DEBUGP("Pattern matches!\n");
303	/* Now we've found the constant string, try to skip
304	to the 'skip' character */
305	for (i = plen; data[i] != skip; i++)
306	if (i == dlen - 1) return -1;
307
308	/* Skip over the last character */
309	i++;
310
311	DEBUGP("Skipped up to `%c'!\n", skip);
312
313	*numoff = i;
314	*numlen = getnum(data + i, dlen - i, cmd, term);
315	if (!*numlen)
316	return -1;
317
318	DEBUGP("Match succeeded!\n");
319	return 1;
320	}
321
322	/* Look up to see if we're just after a \n. */
323	static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
324	{
325	unsigned int i;
326
327	for (i = 0; i < info->seq_aft_nl_num[dir]; i++)
328	if (info->seq_aft_nl[dir][i] == seq)
329	return 1;
330	return 0;
331	}
332
333	/* We don't update if it's older than what we have. */
334	static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
335	struct sk_buff *skb)
336	{
337	unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
338
339	/* Look for oldest: if we find exact match, we're done. */
340	for (i = 0; i < info->seq_aft_nl_num[dir]; i++) {
341	if (info->seq_aft_nl[dir][i] == nl_seq)
342	return;
343
344	if (oldest == info->seq_aft_nl_num[dir]
345	\|\| before(info->seq_aft_nl[dir][i], oldest))
346	oldest = i;
347	}
348
349	if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
350	info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
351	nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
352	} else if (oldest != NUM_SEQ_TO_REMEMBER) {
353	info->seq_aft_nl[dir][oldest] = nl_seq;
354	nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
355	}
356	}
357
358	static int help(struct sk_buff **pskb,
359	unsigned int protoff,
360	struct nf_conn *ct,
361	enum ip_conntrack_info ctinfo)
362	{
363	unsigned int dataoff, datalen;
364	struct tcphdr _tcph, *th;
365	char *fb_ptr;
366	int ret;
367	u32 seq;
368	int dir = CTINFO2DIR(ctinfo);
369	unsigned int matchlen, matchoff;
dc808fe2	370	struct ip_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
9fb9cbb1 YK	371	struct nf_conntrack_expect *exp;
9fb9cbb1 YK	372	struct nf_conntrack_man cmd = {};
9fb9cbb1 YK	373	unsigned int i;
9fb9cbb1 YK	374	int found = 0, ends_in_nl;
337fbc41	375	typeof(nf_nat_ftp_hook) nf_nat_ftp;
9fb9cbb1 YK	376
	377	/* Until there's been traffic both ways, don't look in packets. */
	378	if (ctinfo != IP_CT_ESTABLISHED
	379	&& ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
	380	DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);
	381	return NF_ACCEPT;
	382	}
	383
	384	th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
	385	if (th == NULL)
	386	return NF_ACCEPT;
	387
	388	dataoff = protoff + th->doff * 4;
	389	/* No data? */
	390	if (dataoff >= (*pskb)->len) {
	391	DEBUGP("ftp: dataoff(%u) >= skblen(%u)\n", dataoff,
	392	(*pskb)->len);
	393	return NF_ACCEPT;
	394	}
	395	datalen = (*pskb)->len - dataoff;
	396
	397	spin_lock_bh(&nf_ftp_lock);
	398	fb_ptr = skb_header_pointer(*pskb, dataoff, datalen, ftp_buffer);
	399	BUG_ON(fb_ptr == NULL);
	400
	401	ends_in_nl = (fb_ptr[datalen - 1] == '\n');
	402	seq = ntohl(th->seq) + datalen;
	403
	404	/* Look up to see if we're just after a \n. */
	405	if (!find_nl_seq(ntohl(th->seq), ct_ftp_info, dir)) {
	406	/* Now if this ends in \n, update ftp info. */
	407	DEBUGP("nf_conntrack_ftp_help: wrong seq pos %s(%u) or %s(%u)\n",
	408	ct_ftp_info->seq_aft_nl_num[dir] > 0 ? "" : "(UNSET)",
	409	ct_ftp_info->seq_aft_nl[dir][0],
	410	ct_ftp_info->seq_aft_nl_num[dir] > 1 ? "" : "(UNSET)",
	411	ct_ftp_info->seq_aft_nl[dir][1]);
	412	ret = NF_ACCEPT;
	413	goto out_update_nl;
	414	}
	415
	416	/* Initialize IP/IPv6 addr to expected address (it's not mentioned
	417	in EPSV responses) */
	418	cmd.l3num = ct->tuplehash[dir].tuple.src.l3num;
	419	memcpy(cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
	420	sizeof(cmd.u3.all));
	421
7d8c5018	422	for (i = 0; i < ARRAY_SIZE(search[dir]); i++) {
9fb9cbb1	423	found = find_pattern(fb_ptr, datalen,
7d8c5018 PM	424	search[dir][i].pattern,
	425	search[dir][i].plen,
	426	search[dir][i].skip,
	427	search[dir][i].term,
9fb9cbb1 YK	428	&matchoff, &matchlen,
9fb9cbb1 YK	429	&cmd,
7d8c5018	430	search[dir][i].getnum);
9fb9cbb1 YK	431	if (found) break;
	432	}
	433	if (found == -1) {
	434	/* We don't usually drop packets. After all, this is
	435	connection tracking, not packet filtering.
	436	However, it is necessary for accurate tracking in
	437	this case. */
	438	if (net_ratelimit())
	439	printk("conntrack_ftp: partial %s %u+%u\n",
7d8c5018	440	search[dir][i].pattern,
9fb9cbb1 YK	441	ntohl(th->seq), datalen);
	442	ret = NF_DROP;
	443	goto out;
	444	} else if (found == 0) { /* No match */
	445	ret = NF_ACCEPT;
	446	goto out_update_nl;
	447	}
	448
	449	DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
	450	(int)matchlen, fb_ptr + matchoff,
	451	matchlen, ntohl(th->seq) + matchoff);
	452
	453	exp = nf_conntrack_expect_alloc(ct);
	454	if (exp == NULL) {
	455	ret = NF_DROP;
	456	goto out;
	457	}
	458
	459	/* We refer to the reverse direction ("!dir") tuples here,
	460	* because we're expecting something in the other direction.
	461	* Doesn't matter unless NAT is happening. */
	462	exp->tuple.dst.u3 = ct->tuplehash[!dir].tuple.dst.u3;
	463
	464	/* Update the ftp info */
	465	if ((cmd.l3num == ct->tuplehash[dir].tuple.src.l3num) &&
	466	memcmp(&cmd.u3.all, &ct->tuplehash[dir].tuple.src.u3.all,
	467	sizeof(cmd.u3.all))) {
	468	/* Enrico Scholz's passive FTP to partially RNAT'd ftp
	469	server: it really wants us to connect to a
	470	different IP address. Simply don't record it for
	471	NAT. */
	472	if (cmd.l3num == PF_INET) {
46b86a2d	473	DEBUGP("conntrack_ftp: NOT RECORDING: " NIPQUAD_FMT " != " NIPQUAD_FMT "\n",
9fb9cbb1 YK	474	NIPQUAD(cmd.u3.ip),
	475	NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
	476	} else {
46b86a2d	477	DEBUGP("conntrack_ftp: NOT RECORDING: " NIP6_FMT " != " NIP6_FMT "\n",
9fb9cbb1 YK	478	NIP6(((struct in6_addr )cmd.u3.ip6)),
	479	NIP6(((struct in6_addr )ct->tuplehash[dir]
	480	.tuple.src.u3.ip6)));
	481	}
	482
	483	/* Thanks to Cristiano Lincoln Mattos
	484	<lincoln@cesar.org.br> for reporting this potential
	485	problem (DMZ machines opening holes to internal
	486	networks, or the packet filter itself). */
	487	if (!loose) {
	488	ret = NF_ACCEPT;
	489	goto out_put_expect;
	490	}
	491	memcpy(&exp->tuple.dst.u3, &cmd.u3.all,
	492	sizeof(exp->tuple.dst.u3));
	493	}
	494
	495	exp->tuple.src.u3 = ct->tuplehash[!dir].tuple.src.u3;
	496	exp->tuple.src.l3num = cmd.l3num;
	497	exp->tuple.src.u.tcp.port = 0;
	498	exp->tuple.dst.u.tcp.port = cmd.u.tcp.port;
	499	exp->tuple.dst.protonum = IPPROTO_TCP;
	500
	501	exp->mask = (struct nf_conntrack_tuple)
	502	{ .src = { .l3num = 0xFFFF,
	503	.u = { .tcp = { 0 }},
	504	},
	505	.dst = { .protonum = 0xFF,
bff9a89b	506	.u = { .tcp = { __constant_htons(0xFFFF) }},
9fb9cbb1 YK	507	},
	508	};
	509	if (cmd.l3num == PF_INET) {
bff9a89b PM	510	exp->mask.src.u3.ip = htonl(0xFFFFFFFF);
bff9a89b PM	511	exp->mask.dst.u3.ip = htonl(0xFFFFFFFF);
9fb9cbb1 YK	512	} else {
	513	memset(exp->mask.src.u3.ip6, 0xFF,
	514	sizeof(exp->mask.src.u3.ip6));
	515	memset(exp->mask.dst.u3.ip6, 0xFF,
	516	sizeof(exp->mask.src.u3.ip6));
	517	}
	518
	519	exp->expectfn = NULL;
9457d851	520	exp->helper = NULL;
9fb9cbb1 YK	521	exp->flags = 0;
	522
	523	/* Now, NAT might want to mangle the packet, and register the
	524	* (possibly changed) expectation itself. */
337fbc41 PM	525	nf_nat_ftp = rcu_dereference(nf_nat_ftp_hook);
	526	if (nf_nat_ftp)
	527	ret = nf_nat_ftp(pskb, ctinfo, search[dir][i].ftptype,
	528	matchoff, matchlen, exp, &seq);
9fb9cbb1 YK	529	else {
	530	/* Can't expect this? Best to drop packet now. */
	531	if (nf_conntrack_expect_related(exp) != 0)
	532	ret = NF_DROP;
	533	else
	534	ret = NF_ACCEPT;
	535	}
	536
	537	out_put_expect:
	538	nf_conntrack_expect_put(exp);
	539
	540	out_update_nl:
	541	/* Now if this ends in \n, update ftp info. Seq may have been
	542	* adjusted by NAT code. */
	543	if (ends_in_nl)
	544	update_nl_seq(seq, ct_ftp_info, dir, *pskb);
	545	out:
	546	spin_unlock_bh(&nf_ftp_lock);
	547	return ret;
	548	}
	549
	550	static struct nf_conntrack_helper ftp[MAX_PORTS][2];
	551	static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")];
	552
	553	/* don't make this __exit, since it's called from __init ! */
65b4b4e8	554	static void nf_conntrack_ftp_fini(void)
9fb9cbb1 YK	555	{
	556	int i, j;
	557	for (i = 0; i < ports_c; i++) {
	558	for (j = 0; j < 2; j++) {
	559	if (ftp[i][j].me == NULL)
	560	continue;
	561
	562	DEBUGP("nf_ct_ftp: unregistering helper for pf: %d "
	563	"port: %d\n",
	564	ftp[i][j].tuple.src.l3num, ports[i]);
	565	nf_conntrack_helper_unregister(&ftp[i][j]);
	566	}
	567	}
	568
	569	kfree(ftp_buffer);
	570	}
	571
65b4b4e8	572	static int __init nf_conntrack_ftp_init(void)
9fb9cbb1 YK	573	{
	574	int i, j = -1, ret = 0;
	575	char *tmpname;
	576
	577	ftp_buffer = kmalloc(65536, GFP_KERNEL);
	578	if (!ftp_buffer)
	579	return -ENOMEM;
	580
	581	if (ports_c == 0)
	582	ports[ports_c++] = FTP_PORT;
	583
	584	/* FIXME should be configurable whether IPv4 and IPv6 FTP connections
	585	are tracked or not - YK */
	586	for (i = 0; i < ports_c; i++) {
9fb9cbb1 YK	587	ftp[i][0].tuple.src.l3num = PF_INET;
	588	ftp[i][1].tuple.src.l3num = PF_INET6;
	589	for (j = 0; j < 2; j++) {
	590	ftp[i][j].tuple.src.u.tcp.port = htons(ports[i]);
	591	ftp[i][j].tuple.dst.protonum = IPPROTO_TCP;
d7346853	592	ftp[i][j].mask.src.l3num = 0xFFFF;
bff9a89b	593	ftp[i][j].mask.src.u.tcp.port = htons(0xFFFF);
9fb9cbb1 YK	594	ftp[i][j].mask.dst.protonum = 0xFF;
	595	ftp[i][j].max_expected = 1;
	596	ftp[i][j].timeout = 5 * 60; /* 5 Minutes */
	597	ftp[i][j].me = THIS_MODULE;
	598	ftp[i][j].help = help;
	599	tmpname = &ftp_names[i][j][0];
	600	if (ports[i] == FTP_PORT)
	601	sprintf(tmpname, "ftp");
	602	else
	603	sprintf(tmpname, "ftp-%d", ports[i]);
	604	ftp[i][j].name = tmpname;
	605
	606	DEBUGP("nf_ct_ftp: registering helper for pf: %d "
	607	"port: %d\n",
	608	ftp[i][j].tuple.src.l3num, ports[i]);
	609	ret = nf_conntrack_helper_register(&ftp[i][j]);
	610	if (ret) {
	611	printk("nf_ct_ftp: failed to register helper "
	612	" for pf: %d port: %d\n",
	613	ftp[i][j].tuple.src.l3num, ports[i]);
65b4b4e8	614	nf_conntrack_ftp_fini();
9fb9cbb1 YK	615	return ret;
	616	}
	617	}
	618	}
	619
	620	return 0;
	621	}
	622
65b4b4e8 AM	623	module_init(nf_conntrack_ftp_init);
65b4b4e8 AM	624	module_exit(nf_conntrack_ftp_fini);