/*
* IP_MASQ_FTP ftp masquerading module
*
*
* Version: @(#)ip_masq_ftp.c 0.01 02/05/96
*
* Author: Wouter Gadeyne
*
*
* Fixes:
* Wouter Gadeyne : Fixed masquerading support of ftp PORT commands
* Juan Jose Ciarlante : Code moved and adapted from ip_fw.c
* Keith Owens : Add keep alive for ftp control channel
* Nigel Metheringham : Added multiple port support
*
*
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Multiple Port Support
* The helper can be made to handle up to MAX_MASQ_APP_PORTS (normally 12)
* with the port numbers being defined at module load time. The module
* uses the symbol "ports" to define a list of monitored ports, which can
* be specified on the insmod command line as
* ports=x1,x2,x3...
* where x[n] are integer port numbers. This option can be put into
* /etc/conf.modules (or /etc/modules.conf depending on your config)
* where modload will pick it up should you use modload to load your
* modules.
*
*/
#include <linux/module.h>
#include <asm/system.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <net/ip_masq.h>
#ifndef DEBUG_CONFIG_IP_MASQ_FTP
#define DEBUG_CONFIG_IP_MASQ_FTP 0
#endif
/*
* List of ports (up to MAX_MASQ_APP_PORTS) to be handled by helper
* First port is set to the default port.
*/
int ports[MAX_MASQ_APP_PORTS] = {21}; /* I rely on the trailing items being set to zero */
struct ip_masq_app *masq_incarnations[MAX_MASQ_APP_PORTS];
static int
masq_ftp_init_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
{
MOD_INC_USE_COUNT;
return 0;
}
static int
masq_ftp_done_1 (struct ip_masq_app *mapp, struct ip_masq *ms)
{
MOD_DEC_USE_COUNT;
return 0;
}
int
masq_ftp_out (struct ip_masq_app *mapp, struct ip_masq *ms, struct sk_buff **skb_p, struct device *dev)
{
struct sk_buff *skb;
struct iphdr *iph;
struct tcphdr *th;
char *p, *data, *data_limit;
unsigned char p1,p2,p3,p4,p5,p6;
__u32 from;
__u16 port;
struct ip_masq *n_ms;
char buf[24]; /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
unsigned buf_len;
int diff;
skb = *skb_p;
iph = skb->h.iph;
th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
data = (char *)&th[1];
data_limit = skb->h.raw + skb->len - 18;
if (skb->len >= 6 && (memcmp(data, "PASV\r\n", 6) == 0 || memcmp(data, "pasv\r\n", 6) == 0))
ms->flags |= IP_MASQ_F_FTP_PASV;
while (data < data_limit)
{
if (memcmp(data,"PORT ",5) && memcmp(data,"port ",5))
{
data ++;
continue;
}
p = data+5;
p1 = simple_strtoul(data+5,&data,10);
if (*data!=',')
continue;
p2 = simple_strtoul(data+1,&data,10);
if (*data!=',')
continue;
p3 = simple_strtoul(data+1,&data,10);
if (*data!=',')
continue;
p4 = simple_strtoul(data+1,&data,10);
if (*data!=',')
continue;
p5 = simple_strtoul(data+1,&data,10);
if (*data!=',')
continue;
p6 = simple_strtoul(data+1,&data,10);
if (*data!='\r' && *data!='\n')
continue;
from = (p1<<24) | (p2<<16) | (p3<<8) | p4;
port = (p5<<8) | p6;
#if DEBUG_CONFIG_IP_MASQ_FTP
printk("PORT %X:%X detected\n",from,port);
#endif
/*
* Now update or create an masquerade entry for it
*/
#if DEBUG_CONFIG_IP_MASQ_FTP
printk("protocol %d %lX:%X %X:%X\n", iph->protocol, htonl(from), htons(port), iph->daddr, 0);
#endif
n_ms = ip_masq_out_get_2(iph->protocol,
htonl(from), htons(port),
iph->daddr, 0);
if (n_ms) {
/* existing masquerade, clear timer */
ip_masq_set_expire(n_ms,0);
}
else {
n_ms = ip_masq_new(dev, IPPROTO_TCP,
htonl(from), htons(port),
iph->daddr, 0,
IP_MASQ_F_NO_DPORT);
if (n_ms==NULL)
return 0;
n_ms->control = ms; /* keepalive from data to the control channel */
ms->flags |= IP_MASQ_F_CONTROL; /* this is a control channel */
}
/*
* keep for a bit longer than tcp_fin, caller may not reissue
* PORT before tcp_fin_timeout.
*/
ip_masq_set_expire(n_ms, ip_masq_expire->tcp_fin_timeout*3);
/*
* Replace the old PORT with the new one
*/
from = ntohl(n_ms->maddr);
port = ntohs(n_ms->mport);
sprintf(buf,"%d,%d,%d,%d,%d,%d",
from>>24&255,from>>16&255,from>>8&255,from&255,
port>>8&255,port&255);
buf_len = strlen(buf);
#if DEBUG_CONFIG_IP_MASQ_FTP
printk("new PORT %X:%X\n",from,port);
#endif
/*
* Calculate required delta-offset to keep TCP happy
*/
diff = buf_len - (data-p);
/*
* No shift.
*/
if (diff==0)
{
/*
* simple case, just replace the old PORT cmd
*/
memcpy(p,buf,buf_len);
return 0;
}
*skb_p = ip_masq_skb_replace(skb, GFP_ATOMIC, p, data-p, buf, buf_len);
return diff;
}
return 0;
}
/*
* Look at incoming ftp packets to catch the response to a PASV command. When
* we see one we build a masquerading entry for the client address, client port
* 0 (unknown at the moment), the server address and the server port. Mark the
* current masquerade entry as a control channel and point the new entry at the
* control entry. All this work just for ftp keepalive across masquerading.
*
* The incoming packet should be something like
* "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
* xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
* ncftp 2.3.0 cheats by skipping the leading number then going 22 bytes into
* the data so we do the same. If it's good enough for ncftp then it's good
* enough for me.
*
* In this case, the client is the source machine being masqueraded, the server
* is the destination for ftp requests. It all depends on your point of view ...
*/
int
masq_ftp_in (struct ip_masq_app *mapp, struct ip_masq *ms, struct sk_buff **skb_p, struct device *dev)
{
struct sk_buff *skb;
struct iphdr *iph;
struct tcphdr *th;
char *data, *data_limit;
unsigned char p1,p2,p3,p4,p5,p6;
__u32 to;
__u16 port;
struct ip_masq *n_ms;
if (! ms->flags & IP_MASQ_F_FTP_PASV)
return 0; /* quick exit if no outstanding PASV */
skb = *skb_p;
iph = skb->h.iph;
th = (struct tcphdr *)&(((char *)iph)[iph->ihl*4]);
data = (char *)&th[1];
data_limit = skb->h.raw + skb->len;
while (data < data_limit && *data != ' ')
++data;
while (data < data_limit && *data == ' ')
++data;
data += 22;
if (data >= data_limit || *data != '(')
return 0;
p1 = simple_strtoul(data+1, &data, 10);
if (data >= data_limit || *data != ',')
return 0;
p2 = simple_strtoul(data+1, &data, 10);
if (data >= data_limit || *data != ',')
return 0;
p3 = simple_strtoul(data+1, &data, 10);
if (data >= data_limit || *data != ',')
return 0;
p4 = simple_strtoul(data+1, &data, 10);
if (data >= data_limit || *data != ',')
return 0;
p5 = simple_strtoul(data+1, &data, 10);
if (data >= data_limit || *data != ',')
return 0;
p6 = simple_strtoul(data+1, &data, 10);
if (data >= data_limit || *data != ')')
return 0;
to = (p1<<24) | (p2<<16) | (p3<<8) | p4;
port = (p5<<8) | p6;
/*
* Now update or create an masquerade entry for it
*/
#if DEBUG_CONFIG_IP_MASQ_FTP
printk("PASV response %lX:%X %X:%X detected\n", ntohl(ms->saddr), 0, to, port);
#endif
n_ms = ip_masq_out_get_2(iph->protocol,
ms->saddr, 0,
htonl(to), htons(port));
if (n_ms) {
/* existing masquerade, clear timer */
ip_masq_set_expire(n_ms,0);
}
else {
n_ms = ip_masq_new(dev, IPPROTO_TCP,
ms->saddr, 0,
htonl(to), htons(port),
IP_MASQ_F_NO_SPORT);
if (n_ms==NULL)
return 0;
n_ms->control = ms; /* keepalive from data to the control channel */
ms->flags |= IP_MASQ_F_CONTROL; /* this is a control channel */
}
/*
* keep for a bit longer than tcp_fin, client may not issue open
* to server port before tcp_fin_timeout.
*/
ip_masq_set_expire(n_ms, ip_masq_expire->tcp_fin_timeout*3);
ms->flags &= ~IP_MASQ_F_FTP_PASV;
return 0; /* no diff required for incoming packets, thank goodness */
}
struct ip_masq_app ip_masq_ftp = {
NULL, /* next */
"ftp", /* name */
0, /* type */
0, /* n_attach */
masq_ftp_init_1, /* ip_masq_init_1 */
masq_ftp_done_1, /* ip_masq_done_1 */
masq_ftp_out, /* pkt_out */
masq_ftp_in, /* pkt_in */
};
/*
* ip_masq_ftp initialization
*/
int ip_masq_ftp_init(void)
{
int i, j;
for (i=0; (i<MAX_MASQ_APP_PORTS); i++) {
if (ports[i]) {
if ((masq_incarnations[i] = kmalloc(sizeof(struct ip_masq_app),
GFP_KERNEL)) == NULL)
return -ENOMEM;
memcpy(masq_incarnations[i], &ip_masq_ftp, sizeof(struct ip_masq_app));
if ((j = register_ip_masq_app(masq_incarnations[i],
IPPROTO_TCP,
ports[i]))) {
return j;
}
#if DEBUG_CONFIG_IP_MASQ_FTP
printk("Ftp: loaded support on port[%d] = %d\n",
i, ports[i]);
#endif
} else {
/* To be safe, force the incarnation table entry to NULL */
masq_incarnations[i] = NULL;
}
}
return 0;
}
/*
* ip_masq_ftp fin.
*/
int ip_masq_ftp_done(void)
{
int i, j, k;
k=0;
for (i=0; (i<MAX_MASQ_APP_PORTS); i++) {
if (masq_incarnations[i]) {
if ((j = unregister_ip_masq_app(masq_incarnations[i]))) {
k = j;
} else {
kfree(masq_incarnations[i]);
masq_incarnations[i] = NULL;
#if DEBUG_CONFIG_IP_MASQ_FTP
printk("Ftp: unloaded support on port[%d] = %d\n",
i, ports[i]);
#endif
}
}
}
return k;
}
#ifdef MODULE
int init_module(void)
{
if (ip_masq_ftp_init() != 0)
return -EIO;
register_symtab(0);
return 0;
}
void cleanup_module(void)
{
if (ip_masq_ftp_done() != 0)
printk("ip_masq_ftp: can't remove module");
}
#endif /* MODULE */
