1 files changed, 594 insertions, 0 deletions

diff --git a/net/netfilter/nf_conntrack_ftp.c b/net/netfilter/nf_conntrack_ftp.c
new file mode 100644
index 0000000..4f71071
--- /dev/null
+++ b/net/netfilter/nf_conntrack_ftp.c
@@ -0,0 +1,594 @@
+/* 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.
+ */
+
+#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 *skb,
+				enum ip_conntrack_info ctinfo,
+				enum nf_ct_ftp_type type,
+				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);
+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 nf_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	= 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,
+			.skip		= '(',
+			.term		= ')',
+			.ftptype	= NF_CT_FTP_PASV,
+			.getnum		= try_rfc959,
+		},
+		{
+			.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 and we're finished. */
+			if (*data == 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)
+{
+	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);
+			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)
+{
+	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)
+{
+	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;
+
+	pr_debug("find_pattern `%s': dlen = %Zu\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;
+
+		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 */
+	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);
+	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 = 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],
+			   info->seq_aft_nl[dir][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, ct);
+	} else if (oldest != NUM_SEQ_TO_REMEMBER &&
+		   after(nl_seq, info->seq_aft_nl[dir][oldest])) {
+		info->seq_aft_nl[dir][oldest] = nl_seq;
+		nf_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, ct);
+	}
+}
+
+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 matchlen, matchoff;
+	struct nf_ct_ftp_master *ct_ftp_info = &nfct_help(ct)->help.ct_ftp_info;
+	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+IP_CT_IS_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)) {
+		/* 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;
+	}
+
+	/* 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. */
+		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;
+	}
+
+	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) {
+		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: " NIPQUAD_FMT
+				 " != " NIPQUAD_FMT "\n",
+				 NIPQUAD(cmd.u3.ip),
+				 NIPQUAD(ct->tuplehash[dir].tuple.src.u3.ip));
+		} else {
+			pr_debug("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;
+		}
+		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,
+				 matchoff, matchlen, exp);
+	else {
+		/* Can't expect this?  Best to drop packet now. */
+		if (nf_ct_expect_related(exp) != 0)
+			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 struct nf_conntrack_helper ftp[MAX_PORTS][2] __read_mostly;
+static char ftp_names[MAX_PORTS][2][sizeof("ftp-65535")] __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;
+	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].expect_policy = &ftp_exp_policy;
+			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;
+
+			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("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);