// SPDX-License-Identifier: GPL-2.0-or-later
/*
* ip_vs_ftp.c: IPVS ftp application module
*
* Authors: Wensong Zhang <[email protected]>
*
* Changes:
*
* Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
* is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
*
* IP_MASQ_FTP ftp masquerading module
*
* Version: @(#)ip_masq_ftp.c 0.04 02/05/96
*
* Author: Wouter Gadeyne
*/
#define KMSG_COMPONENT "IPVS"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/ctype.h>
#include <linux/inet.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_helper.h>
#include <linux/gfp.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <linux/unaligned.h>
#include <net/ip_vs.h>
#define SERVER_STRING_PASV "227 "
#define CLIENT_STRING_PORT "PORT"
#define SERVER_STRING_EPSV "229 "
#define CLIENT_STRING_EPRT "EPRT"
enum {
IP_VS_FTP_ACTIVE = 0,
IP_VS_FTP_PORT = 0,
IP_VS_FTP_PASV,
IP_VS_FTP_EPRT,
IP_VS_FTP_EPSV,
};
/*
* List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
* First port is set to the default port.
*/
static unsigned int ports_count = 1;
static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
module_param_array(ports, ushort, &ports_count, 0444);
MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
static char *ip_vs_ftp_data_ptr(struct sk_buff *skb, struct ip_vs_iphdr *ipvsh)
{
struct tcphdr *th = (struct tcphdr *)((char *)skb->data + ipvsh->len);
if ((th->doff << 2) < sizeof(struct tcphdr))
return NULL;
return (char *)th + (th->doff << 2);
}
static int
ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
{
/* We use connection tracking for the command connection */
cp->flags |= IP_VS_CONN_F_NFCT;
return 0;
}
static int
ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
{
return 0;
}
/* Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
* with the "pattern". <addr,port> is in network order.
* Parse extended format depending on ext. In this case addr can be pre-set.
*/
static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
const char *pattern, size_t plen,
char skip, bool ext, int mode,
union nf_inet_addr *addr, __be16 *port,
__u16 af, char **start, char **end)
{
char *s, c;
unsigned char p[6];
char edelim;
__u16 hport;
int i = 0;
if (data_limit - data < plen) {
/* check if there is partial match */
if (strncasecmp(data, pattern, data_limit - data) == 0)
return -1;
else
return 0;
}
if (strncasecmp(data, pattern, plen) != 0) {
return 0;
}
s = data + plen;
if (skip) {
bool found = false;
for (;; s++) {
if (s == data_limit)
return -1;
if (!found) {
/* "(" is optional for non-extended format,
* so catch the start of IPv4 address
*/
if (!ext && isdigit(*s))
break;
if (*s == skip)
found = true;
} else if (*s != skip) {
break;
}
}
}
/* Old IPv4-only format? */
if (!ext) {
p[0] = 0;
for (data = s; ; data++) {
if (data == data_limit)
return -1;
c = *data;
if (isdigit(c)) {
p[i] = p[i]*10 + c - '0';
} else if (c == ',' && i < 5) {
i++;
p[i] = 0;
} else {
/* unexpected character or terminator */
break;
}
}
if (i != 5)
return -1;
*start = s;
*end = data;
addr->ip = get_unaligned((__be32 *) p);
*port = get_unaligned((__be16 *) (p + 4));
return 1;
}
if (s == data_limit)
return -1;
*start = s;
edelim = *s++;
if (edelim < 33 || edelim > 126)
return -1;
if (s == data_limit)
return -1;
if (*s == edelim) {
/* Address family is usually missing for EPSV response */
if (mode != IP_VS_FTP_EPSV)
return -1;
s++;
if (s == data_limit)
return -1;
/* Then address should be missing too */
if (*s != edelim)
return -1;
/* Caller can pre-set addr, if needed */
s++;
} else {
const char *ep;
/* We allow address only from same family */
if (af == AF_INET6 && *s != '2')
return -1;
if (af == AF_INET && *s != '1')
return -1;
s++;
if (s == data_limit)
return -1;
if (*s != edelim)
return -1;
s++;
if (s == data_limit)
return -1;
if (af == AF_INET6) {
if (in6_pton(s, data_limit - s, (u8 *)addr, edelim,
&ep) <= 0)
return -1;
} else {
if (in4_pton(s, data_limit - s, (u8 *)addr, edelim,
&ep) <= 0)
return -1;
}
s = (char *) ep;
if (s == data_limit)
return -1;
if (*s != edelim)
return -1;
s++;
}
for (hport = 0; ; s++)
{
if (s == data_limit)
return -1;
if (!isdigit(*s))
break;
hport = hport * 10 + *s - '0';
}
if (s == data_limit || !hport || *s != edelim)
return -1;
s++;
*end = s;
*port = htons(hport);
return 1;
}
/* Look at outgoing ftp packets to catch the response to a PASV/EPSV command
* from the server (inside-to-outside).
* When we see one, we build a connection entry with the client address,
* client port 0 (unknown at the moment), the server address and the
* server port. Mark the current connection entry as a control channel
* of the new entry. All this work is just to make the data connection
* can be scheduled to the right server later.
*
* The outgoing 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.
* The extended format for EPSV response provides usually only port:
* "229 Entering Extended Passive Mode (|||ppp|)"
*/
static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
struct sk_buff *skb, int *diff,
struct ip_vs_iphdr *ipvsh)
{
char *data, *data_limit;
char *start, *end;
union nf_inet_addr from;
__be16 port;
struct ip_vs_conn *n_cp;
char buf[24]; /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
unsigned int buf_len;
int ret = 0;
enum ip_conntrack_info ctinfo;
struct nf_conn *ct;
*diff = 0;
/* Only useful for established sessions */
if (cp->state != IP_VS_TCP_S_ESTABLISHED)
return 1;
/* Linear packets are much easier to deal with. */
if (skb_ensure_writable(skb, skb->len))
return 0;
if (cp->app_data == (void *) IP_VS_FTP_PASV) {
data = ip_vs_ftp_data_ptr(skb, ipvsh);
data_limit = skb_tail_pointer(skb);
if (!data || data >= data_limit)
return 1;
if (ip_vs_ftp_get_addrport(data, data_limit,
SERVER_STRING_PASV,
sizeof(SERVER_STRING_PASV)-1,
'(', false, IP_VS_FTP_PASV,
&from, &port, cp->af,
&start, &end) != 1)
return 1;
IP_VS_DBG(7, "PASV response (%pI4:%u) -> %pI4:%u detected\n",
&from.ip, ntohs(port), &cp->caddr.ip, 0);
} else if (cp->app_data == (void *) IP_VS_FTP_EPSV) {
data = ip_vs_ftp_data_ptr(skb, ipvsh);
data_limit = skb_tail_pointer(skb);
if (!data || data >= data_limit)
return 1;
/* Usually, data address is not specified but
* we support different address, so pre-set it.
*/
from = cp->daddr;
if (ip_vs_ftp_get_addrport(data, data_limit,
SERVER_STRING_EPSV,
sizeof(SERVER_STRING_EPSV)-1,
'(', true, IP_VS_FTP_EPSV,
&from, &port, cp->af,
&start, &end) != 1)
return 1;
IP_VS_DBG_BUF(7, "EPSV response (%s:%u) -> %s:%u detected\n",
IP_VS_DBG_ADDR(cp->af, &from), ntohs(port),
IP_VS_DBG_ADDR(cp->af, &cp->caddr), 0);
} else {
return 1;
}
/* Now update or create a connection entry for it */
{
struct ip_vs_conn_param p;
ip_vs_conn_fill_param(cp->ipvs, cp->af,
ipvsh->protocol, &from, port,
&cp->caddr, 0, &p);
n_cp = ip_vs_conn_out_get(&p);
}
if (!n_cp) {
struct ip_vs_conn_param p;
ip_vs_conn_fill_param(cp->ipvs,
cp->af, ipvsh->protocol, &cp->caddr,
0, &cp->vaddr, port, &p);
n_cp = ip_vs_conn_new(&p, cp->af, &from, port,
IP_VS_CONN_F_NO_CPORT |
IP_VS_CONN_F_NFCT,
cp->dest, skb->mark);
if (!n_cp)
return 0;
/* add its controller */
ip_vs_control_add(n_cp, cp);
}
/* Replace the old passive address with the new one */
if (cp->app_data == (void *) IP_VS_FTP_PASV) {
from.ip = n_cp->vaddr.ip;
port = n_cp->vport;
snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
((unsigned char *)&from.ip)[0],
((unsigned char *)&from.ip)[1],
((unsigned char *)&from.ip)[2],
((unsigned char *)&from.ip)[3],
ntohs(port) >> 8,
ntohs(port) & 0xFF);
} else if (cp->app_data == (void *) IP_VS_FTP_EPSV) {
from = n_cp->vaddr;
port = n_cp->vport;
/* Only port, client will use VIP for the data connection */
snprintf(buf, sizeof(buf), "|||%u|",
ntohs(port));
} else {
*buf = 0;
}
buf_len = strlen(buf);
ct = nf_ct_get(skb, &ctinfo);
if (ct) {
bool mangled;
/* If mangling fails this function will return 0
* which will cause the packet to be dropped.
* Mangling can only fail under memory pressure,
* hopefully it will succeed on the retransmitted
* packet.
*/
mangled = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
ipvsh->len,
start - data,
end - start,
buf, buf_len);
if (mangled) {
ip_vs_nfct_expect_related(skb, ct, n_cp,
ipvsh->protocol, 0, 0);
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->ip_summed = CHECKSUM_UNNECESSARY;
/* csum is updated */
ret = 1;
}
}
/* Not setting 'diff' is intentional, otherwise the sequence
* would be adjusted twice.
*/
cp->app_data = (void *) IP_VS_FTP_ACTIVE;
ip_vs_tcp_conn_listen(n_cp);
ip_vs_conn_put(n_cp);
return ret;
}
/* Look at incoming ftp packets to catch the PASV/PORT/EPRT/EPSV command
* (outside-to-inside).
*
* The incoming packet having the PORT command should be something like
* "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
* xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
* In this case, we create a connection entry using the client address and
* port, so that the active ftp data connection from the server can reach
* the client.
* Extended format:
* "EPSV\r\n" when client requests server address from same family
* "EPSV 1\r\n" when client requests IPv4 server address
* "EPSV 2\r\n" when client requests IPv6 server address
* "EPSV ALL\r\n" - not supported
* EPRT with specified delimiter (ASCII 33..126), "|" by default:
* "EPRT |1|IPv4ADDR|PORT|\r\n" when client provides IPv4 addrport
* "EPRT |2|IPv6ADDR|PORT|\r\n" when client provides IPv6 addrport
*/
static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
struct sk_buff *skb, int *diff,
struct ip_vs_iphdr *ipvsh)
{
char *data, *data_start, *data_limit;
char *start, *end;
union nf_inet_addr to;
__be16 port;
struct ip_vs_conn *n_cp;
/* no diff required for incoming packets */
*diff = 0;
/* Only useful for established sessions */
if (cp->state != IP_VS_TCP_S_ESTABLISHED)
return 1;
/* Linear packets are much easier to deal with. */
if (skb_ensure_writable(skb, skb->len))
return 0;
data = data_start = ip_vs_ftp_data_ptr(skb, ipvsh);
data_limit = skb_tail_pointer(skb);
if (!data || data >= data_limit)
return 1;
while (data <= data_limit - 6) {
if (cp->af == AF_INET &&
strncasecmp(data, "PASV\r\n", 6) == 0) {
/* Passive mode on */
IP_VS_DBG(7, "got PASV at %td of %td\n",
data - data_start,
data_limit - data_start);
cp->app_data = (void *) IP_VS_FTP_PASV;
return 1;
}
/* EPSV or EPSV<space><net-prt> */
if (strncasecmp(data, "EPSV", 4) == 0 &&
(data[4] == ' ' || data[4] == '\r')) {
if (data[4] == ' ') {
char proto = data[5];
if (data > data_limit - 7 || data[6] != '\r')
return 1;
#ifdef CONFIG_IP_VS_IPV6
if (cp->af == AF_INET6 && proto == '2') {
} else
#endif
if (cp->af == AF_INET && proto == '1') {
} else {
return 1;
}
}
/* Extended Passive mode on */
IP_VS_DBG(7, "got EPSV at %td of %td\n",
data - data_start,
data_limit - data_start);
cp->app_data = (void *) IP_VS_FTP_EPSV;
return 1;
}
data++;
}
/*
* To support virtual FTP server, the scenerio is as follows:
* FTP client ----> Load Balancer ----> FTP server
* First detect the port number in the application data,
* then create a new connection entry for the coming data
* connection.
*/
if (cp->af == AF_INET &&
ip_vs_ftp_get_addrport(data_start, data_limit,
CLIENT_STRING_PORT,
sizeof(CLIENT_STRING_PORT)-1,
' ', false, IP_VS_FTP_PORT,
&to, &port, cp->af,
&start, &end) == 1) {
IP_VS_DBG(7, "PORT %pI4:%u detected\n", &to.ip, ntohs(port));
/* Now update or create a connection entry for it */
IP_VS_DBG(7, "protocol %s %pI4:%u %pI4:%u\n",
ip_vs_proto_name(ipvsh->protocol),
&to.ip, ntohs(port), &cp->vaddr.ip,
ntohs(cp->vport)-1);
} else if (ip_vs_ftp_get_addrport(data_start, data_limit,
CLIENT_STRING_EPRT,
sizeof(CLIENT_STRING_EPRT)-1,
' ', true, IP_VS_FTP_EPRT,
&to, &port, cp->af,
&start, &end) == 1) {
IP_VS_DBG_BUF(7, "EPRT %s:%u detected\n",
IP_VS_DBG_ADDR(cp->af, &to), ntohs(port));
/* Now update or create a connection entry for it */
IP_VS_DBG_BUF(7, "protocol %s %s:%u %s:%u\n",
ip_vs_proto_name(ipvsh->protocol),
IP_VS_DBG_ADDR(cp->af, &to), ntohs(port),
IP_VS_DBG_ADDR(cp->af, &cp->vaddr),
ntohs(cp->vport)-1);
} else {
return 1;
}
/* Passive mode off */
cp->app_data = (void *) IP_VS_FTP_ACTIVE;
{
struct ip_vs_conn_param p;
ip_vs_conn_fill_param(cp->ipvs, cp->af,
ipvsh->protocol, &to, port, &cp->vaddr,
htons(ntohs(cp->vport)-1), &p);
n_cp = ip_vs_conn_in_get(&p);
if (!n_cp) {
n_cp = ip_vs_conn_new(&p, cp->af, &cp->daddr,
htons(ntohs(cp->dport)-1),
IP_VS_CONN_F_NFCT, cp->dest,
skb->mark);
if (!n_cp)
return 0;
/* add its controller */
ip_vs_control_add(n_cp, cp);
}
}
/*
* Move tunnel to listen state
*/
ip_vs_tcp_conn_listen(n_cp);
ip_vs_conn_put(n_cp);
return 1;
}
static struct ip_vs_app ip_vs_ftp = {
.name = "ftp",
.type = IP_VS_APP_TYPE_FTP,
.protocol = IPPROTO_TCP,
.module = THIS_MODULE,
.incs_list = LIST_HEAD_INIT(ip_vs_ftp.incs_list),
.init_conn = ip_vs_ftp_init_conn,
.done_conn = ip_vs_ftp_done_conn,
.bind_conn = NULL,
.unbind_conn = NULL,
.pkt_out = ip_vs_ftp_out,
.pkt_in = ip_vs_ftp_in,
};
/*
* per netns ip_vs_ftp initialization
*/
static int __net_init __ip_vs_ftp_init(struct net *net)
{
int i, ret;
struct ip_vs_app *app;
struct netns_ipvs *ipvs = net_ipvs(net);
if (!ipvs)
return -ENOENT;
app = register_ip_vs_app(ipvs, &ip_vs_ftp);
if (IS_ERR(app))
return PTR_ERR(app);
for (i = 0; i < ports_count; i++) {
if (!ports[i])
continue;
ret = register_ip_vs_app_inc(ipvs, app, app->protocol, ports[i]);
if (ret)
goto err_unreg;
}
return 0;
err_unreg:
unregister_ip_vs_app(ipvs, &ip_vs_ftp);
return ret;
}
/*
* netns exit
*/
static void __ip_vs_ftp_exit(struct net *net)
{
struct netns_ipvs *ipvs = net_ipvs(net);
if (!ipvs)
return;
unregister_ip_vs_app(ipvs, &ip_vs_ftp);
}
static struct pernet_operations ip_vs_ftp_ops = {
.init = __ip_vs_ftp_init,
.exit = __ip_vs_ftp_exit,
};
static int __init ip_vs_ftp_init(void)
{
/* rcu_barrier() is called by netns on error */
return register_pernet_subsys(&ip_vs_ftp_ops);
}
/*
* ip_vs_ftp finish.
*/
static void __exit ip_vs_ftp_exit(void)
{
unregister_pernet_subsys(&ip_vs_ftp_ops);
/* rcu_barrier() is called by netns */
}
module_init(ip_vs_ftp_init);
module_exit(ip_vs_ftp_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ipvs ftp helper");
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