patch-2.4.4 linux/net/ipv4/netfilter/ip_conntrack_ftp.c

• Lines: 374
• Date: Wed Apr 25 15:02:09 2001
• Orig file: v2.4.3/linux/net/ipv4/netfilter/ip_conntrack_ftp.c
• Orig date: Thu Aug 10 12:35:15 2000

diff -u --recursive --new-file v2.4.3/linux/net/ipv4/netfilter/ip_conntrack_ftp.c linux/net/ipv4/netfilter/ip_conntrack_ftp.c
@@ -2,6 +2,7 @@
 #include <linux/module.h>
 #include <linux/netfilter.h>
 #include <linux/ip.h>
+#include <linux/ctype.h>
 #include <net/checksum.h>
 #include <net/tcp.h>
 
@@ -12,8 +13,15 @@
 DECLARE_LOCK(ip_ftp_lock);
 struct module *ip_conntrack_ftp = THIS_MODULE;
 
-#define SERVER_STRING "227 Entering Passive Mode ("
-#define CLIENT_STRING "PORT "
+#define MAX_PORTS 8
+static int ports[MAX_PORTS];
+static int ports_c;
+#ifdef MODULE_PARM
+MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");
+#endif
+
+static int loose = 0;
+MODULE_PARM(loose, "i");
 
 #if 0
 #define DEBUGP printk
@@ -21,32 +29,63 @@
 #define DEBUGP(format, args...)
 #endif
 
-static struct {
+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_espv_response(const char *, size_t, u_int32_t [], char);
+
+static struct ftp_search {
+	enum ip_conntrack_dir dir;
 	const char *pattern;
 	size_t plen;
+	char skip;
 	char term;
-} search[2] = {
-	[IP_CT_FTP_PORT] { CLIENT_STRING, sizeof(CLIENT_STRING) - 1, '\r' },
-	[IP_CT_FTP_PASV] { SERVER_STRING, sizeof(SERVER_STRING) - 1, ')' }
+	enum ip_ct_ftp_type ftptype;
+	int (*getnum)(const char *, size_t, u_int32_t[], 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_espv_response,
+	},
 };
 
-/* Returns 0, or length of numbers */
-static int try_number(const char *data, size_t dlen, u_int32_t array[6],
-		      char term)
+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; len++, data++) {
+	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 == ',')
+		else if (*data == sep)
 			i++;
 		else {
 			/* Unexpected character; true if it's the
 			   terminator and we're finished. */
-			if (*data == term && i == 5)
+			if (*data == term && i == array_size - 1)
 				return len;
 
 			DEBUGP("Char %u (got %u nums) `%u' unexpected\n",
@@ -54,22 +93,100 @@
 			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_espv_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 term,
+			char skip, char term,
 			unsigned int *numoff,
 			unsigned int *numlen,
-			u_int32_t array[6])
+			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) {
+	if (dlen <= plen) {
 		/* Short packet: try for partial? */
 		if (strnicmp(data, pattern, dlen) == 0)
 			return -1;
@@ -90,11 +207,23 @@
 		return 0;
 	}
 
-	*numoff = plen;
-	*numlen = try_number(data + plen, dlen - plen, array, term);
+	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;
 }
 
@@ -115,6 +244,8 @@
 	unsigned int matchlen, matchoff;
 	struct ip_conntrack_tuple t, mask;
 	struct ip_ct_ftp *info = &ct->help.ct_ftp_info;
+	unsigned int i;
+	int found = 0;
 
 	/* Until there's been traffic both ways, don't look in packets. */
 	if (ctinfo != IP_CT_ESTABLISHED
@@ -163,25 +294,38 @@
 		return NF_ACCEPT;
 	}
 
-	switch (find_pattern(data, datalen,
-			     search[dir].pattern,
-			     search[dir].plen, search[dir].term,
-			     &matchoff, &matchlen,
-			     array)) {
-	case -1: /* partial */
+	/* 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 < sizeof(search) / sizeof(search[0]); i++) {
+		if (search[i].dir != dir) continue;
+
+		found = find_pattern(data, datalen,
+				     search[i].pattern,
+				     search[i].plen,
+				     search[i].skip,
+				     search[i].term,
+				     &matchoff, &matchlen,
+				     array,
+				     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 neccessary for accurate tracking in
 		   this case. */
 		if (net_ratelimit())
-			printk("conntrack_ftp: partial %u+%u\n",
+			printk("conntrack_ftp: partial %s %u+%u\n",
+			       search[i].pattern,
 			       ntohl(tcph->seq), datalen);
 		return NF_DROP;
-
-	case 0: /* no match */
-		DEBUGP("ip_conntrack_ftp_help: no match\n");
+	} else if (found == 0) /* No match */
 		return NF_ACCEPT;
-	}
 
 	DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",
 	       (int)matchlen, data + matchoff,
@@ -194,7 +338,7 @@
 		info->is_ftp = 1;
 		info->seq = ntohl(tcph->seq) + matchoff;
 		info->len = matchlen;
-		info->ftptype = dir;
+		info->ftptype = search[i].ftptype;
 		info->port = array[4] << 8 | array[5];
 	} else {
 		/* Enrico Scholz's passive FTP to partially RNAT'd ftp
@@ -204,6 +348,12 @@
 		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) goto out;
 	}
 
 	t = ((struct ip_conntrack_tuple)
@@ -218,27 +368,52 @@
 		  { 0xFFFFFFFF, { 0xFFFF }, 0xFFFF }});
 	/* Ignore failure; should only happen with NAT */
 	ip_conntrack_expect_related(ct, &t, &mask, NULL);
+ out:
 	UNLOCK_BH(&ip_ftp_lock);
 
 	return NF_ACCEPT;
 }
 
-static struct ip_conntrack_helper ftp = { { NULL, NULL },
-					  { { 0, { __constant_htons(21) } },
-					    { 0, { 0 }, IPPROTO_TCP } },
-					  { { 0, { 0xFFFF } },
-					    { 0, { 0 }, 0xFFFF } },
-					  help };
+static struct ip_conntrack_helper ftp[MAX_PORTS];
 
-static int __init init(void)
+/* Not __exit: called from init() */
+static void fini(void)
 {
-	return ip_conntrack_helper_register(&ftp);
+	int i;
+	for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
+		DEBUGP("ip_ct_ftp: unregistering helper for port %d\n",
+				ports[i]);
+		ip_conntrack_helper_unregister(&ftp[i]);
+	}
 }
 
-static void __exit fini(void)
+static int __init init(void)
 {
-	ip_conntrack_helper_unregister(&ftp);
+	int i, ret;
+
+	if (ports[0] == 0)
+		ports[0] = 21;
+
+	for (i = 0; (i < MAX_PORTS) && ports[i]; i++) {
+		memset(&ftp[i], 0, sizeof(struct ip_conntrack_helper));
+		ftp[i].tuple.src.u.tcp.port = htons(ports[i]);
+		ftp[i].tuple.dst.protonum = IPPROTO_TCP;
+		ftp[i].mask.src.u.tcp.port = 0xFFFF;
+		ftp[i].mask.dst.protonum = 0xFFFF;
+		ftp[i].help = help;
+		DEBUGP("ip_ct_ftp: registering helper for port %d\n", 
+				ports[i]);
+		ret = ip_conntrack_helper_register(&ftp[i]);
+
+		if (ret) {
+			fini();
+			return ret;
+		}
+		ports_c++;
+	}
+	return 0;
 }
+
 
 EXPORT_SYMBOL(ip_ftp_lock);
 EXPORT_SYMBOL(ip_conntrack_ftp);