/* 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/config.h>#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/lockhelp.h>#include <linux/netfilter_ipv4/ip_conntrack_helper.h>#include <linux/netfilter_ipv4/ip_conntrack_ftp.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[65536];DECLARE_LOCK(ip_ftp_lock);struct module *ip_conntrack_ftp = THIS_MODULE;#define MAX_PORTS 8static int ports[MAX_PORTS];static int ports_c;MODULE_PARM(ports, "1-" __MODULE_STRING(MAX_PORTS) "i");static int loose;MODULE_PARM(loose, "i");#if 0#define DEBUGP printk#else#define DEBUGP(format, args...)#endifstatic 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 struct ftp_search {	enum ip_conntrack_dir dir;	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_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_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;}static int help(struct sk_buff *skb,		struct ip_conntrack *ct,		enum ip_conntrack_info ctinfo){	unsigned int dataoff, datalen;	struct tcphdr tcph;	u_int32_t old_seq_aft_nl;	int old_seq_aft_nl_set, ret;	u_int32_t 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;	struct ip_ct_ftp_expect *exp_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	    && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {		DEBUGP("ftp: Conntrackinfo = %u\n", ctinfo);		return NF_ACCEPT;	}	if (skb_copy_bits(skb, skb->nh.iph->ihl*4, &tcph, sizeof(tcph)) != 0)		return NF_ACCEPT;	dataoff = skb->nh.iph->ihl*4 + tcph.doff*4;	/* No data? */	if (dataoff >= skb->len) {		DEBUGP("ftp: skblen = %u\n", skb->len);		return NF_ACCEPT;	}	datalen = skb->len - dataoff;	LOCK_BH(&ip_ftp_lock);	skb_copy_bits(skb, dataoff, ftp_buffer, skb->len - dataoff);	old_seq_aft_nl_set = ct_ftp_info->seq_aft_nl_set[dir];	old_seq_aft_nl = ct_ftp_info->seq_aft_nl[dir];	DEBUGP("conntrack_ftp: datalen %u\n", datalen);	if (ftp_buffer[datalen - 1] == '\n') {		DEBUGP("conntrack_ftp: datalen %u ends in \\n\n", datalen);		if (!old_seq_aft_nl_set		    || after(ntohl(tcph.seq) + datalen, old_seq_aft_nl)) {			DEBUGP("conntrack_ftp: updating nl to %u\n",			       ntohl(tcph.seq) + datalen);			ct_ftp_info->seq_aft_nl[dir] = 						ntohl(tcph.seq) + datalen;			ct_ftp_info->seq_aft_nl_set[dir] = 1;		}	}	if(!old_seq_aft_nl_set ||			(ntohl(tcph.seq) != old_seq_aft_nl)) {		DEBUGP("ip_conntrack_ftp_help: wrong seq pos %s(%u)\n",		       old_seq_aft_nl_set ? "":"(UNSET) ", old_seq_aft_nl);		ret = NF_ACCEPT;		goto out;	}	/* 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); i++) {		if (search[i].dir != dir) continue;		found = find_pattern(ftp_buffer, skb->len - dataoff,				     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 necessary for accurate tracking in		   this case. */		if (net_ratelimit())			printk("conntrack_ftp: partial %s %u+%u\n",			       search[i].pattern,			       ntohl(tcph.seq), datalen);		ret = NF_DROP;		goto out;	} else if (found == 0) { /* No match */		ret = NF_ACCEPT;		goto out;	}	DEBUGP("conntrack_ftp: match `%.*s' (%u bytes at %u)\n",	       (int)matchlen, data + matchoff,	       matchlen, ntohl(tcph.seq) + matchoff);	/* Allocate expectation which will be inserted */	exp = ip_conntrack_expect_alloc();	if (exp == NULL) {		ret = NF_ACCEPT;		goto out;	}	exp_ftp_info = &exp->help.exp_ftp_info;	/* Update the ftp info */	if (htonl((array[0] << 24) | (array[1] << 16) | (array[2] << 8) | array[3])	    == ct->tuplehash[dir].tuple.src.ip) {		exp->seq = ntohl(tcph.seq) + matchoff;		exp_ftp_info->len = matchlen;		exp_ftp_info->ftptype = search[i].ftptype;		exp_ftp_info->port = array[4] << 8 | array[5];	} else {		/* 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;		}	}	exp->tuple = ((struct ip_conntrack_tuple)		{ { ct->tuplehash[!dir].tuple.src.ip,		    { 0 } },		  { htonl((array[0] << 24) | (array[1] << 16)			  | (array[2] << 8) | array[3]),		    { .tcp = { htons(array[4] << 8 | array[5]) } },		    IPPROTO_TCP }});	exp->mask = ((struct ip_conntrack_tuple)		{ { 0xFFFFFFFF, { 0 } },		  { 0xFFFFFFFF, { .tcp = { 0xFFFF } }, 0xFFFF }});	exp->expectfn = NULL;	/* Ignore failure; should only happen with NAT */	ip_conntrack_expect_related(exp, ct);	ret = NF_ACCEPT; out:	UNLOCK_BH(&ip_ftp_lock);	return ret;}static struct ip_conntrack_helper ftp[MAX_PORTS];static char ftp_names[MAX_PORTS][10];/* Not __exit: called from init() */static void 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]);	}}static int __init init(void){	int i, ret;	char *tmpname;	if (ports[0] == 0)		ports[0] = FTP_PORT;	for (i = 0; (i < MAX_PORTS) && ports[i]; 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 = 0xFFFF;		ftp[i].mask.dst.protonum = 0xFFFF;		ftp[i].max_expected = 1;		ftp[i].timeout = 0;		ftp[i].flags = IP_CT_HELPER_F_REUSE_EXPECT;		ftp[i].me = ip_conntrack_ftp;		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) {			fini();			return ret;		}		ports_c++;	}	return 0;}PROVIDES_CONNTRACK(ftp);EXPORT_SYMBOL(ip_ftp_lock);module_init(init);module_exit(fini);