diff options
Diffstat (limited to 'net/netfilter/nf_nat_ftp.c')
-rw-r--r-- | net/netfilter/nf_nat_ftp.c | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/net/netfilter/nf_nat_ftp.c b/net/netfilter/nf_nat_ftp.c new file mode 100644 index 0000000000..c92a436d9c --- /dev/null +++ b/net/netfilter/nf_nat_ftp.c @@ -0,0 +1,138 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* FTP extension for TCP NAT alteration. */ + +/* (C) 1999-2001 Paul `Rusty' Russell + * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org> + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/moduleparam.h> +#include <linux/inet.h> +#include <linux/tcp.h> +#include <linux/netfilter_ipv4.h> +#include <net/netfilter/nf_nat.h> +#include <net/netfilter/nf_nat_helper.h> +#include <net/netfilter/nf_conntrack_helper.h> +#include <net/netfilter/nf_conntrack_expect.h> +#include <linux/netfilter/nf_conntrack_ftp.h> + +#define NAT_HELPER_NAME "ftp" + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); +MODULE_DESCRIPTION("ftp NAT helper"); +MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME); + +/* FIXME: Time out? --RR */ + +static struct nf_conntrack_nat_helper nat_helper_ftp = + NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME); + +static int nf_nat_ftp_fmt_cmd(struct nf_conn *ct, enum nf_ct_ftp_type type, + char *buffer, size_t buflen, + union nf_inet_addr *addr, u16 port) +{ + switch (type) { + case NF_CT_FTP_PORT: + case NF_CT_FTP_PASV: + return snprintf(buffer, buflen, "%u,%u,%u,%u,%u,%u", + ((unsigned char *)&addr->ip)[0], + ((unsigned char *)&addr->ip)[1], + ((unsigned char *)&addr->ip)[2], + ((unsigned char *)&addr->ip)[3], + port >> 8, + port & 0xFF); + case NF_CT_FTP_EPRT: + if (nf_ct_l3num(ct) == NFPROTO_IPV4) + return snprintf(buffer, buflen, "|1|%pI4|%u|", + &addr->ip, port); + else + return snprintf(buffer, buflen, "|2|%pI6|%u|", + &addr->ip6, port); + case NF_CT_FTP_EPSV: + return snprintf(buffer, buflen, "|||%u|", port); + } + + return 0; +} + +/* So, this packet has hit the connection tracking matching code. + Mangle it, and change the expectation to match the new version. */ +static unsigned int nf_nat_ftp(struct sk_buff *skb, + enum ip_conntrack_info ctinfo, + enum nf_ct_ftp_type type, + unsigned int protoff, + unsigned int matchoff, + unsigned int matchlen, + struct nf_conntrack_expect *exp) +{ + union nf_inet_addr newaddr; + u_int16_t port; + int dir = CTINFO2DIR(ctinfo); + struct nf_conn *ct = exp->master; + char buffer[sizeof("|1||65535|") + INET6_ADDRSTRLEN]; + unsigned int buflen; + + pr_debug("type %i, off %u len %u\n", type, matchoff, matchlen); + + /* Connection will come from wherever this packet goes, hence !dir */ + newaddr = ct->tuplehash[!dir].tuple.dst.u3; + exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port; + exp->dir = !dir; + + /* When you see the packet, we need to NAT it the same as the + * this one. */ + exp->expectfn = nf_nat_follow_master; + + port = nf_nat_exp_find_port(exp, ntohs(exp->saved_proto.tcp.port)); + if (port == 0) { + nf_ct_helper_log(skb, exp->master, "all ports in use"); + return NF_DROP; + } + + buflen = nf_nat_ftp_fmt_cmd(ct, type, buffer, sizeof(buffer), + &newaddr, port); + if (!buflen) + goto out; + + pr_debug("calling nf_nat_mangle_tcp_packet\n"); + + if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff, + matchlen, buffer, buflen)) + goto out; + + return NF_ACCEPT; + +out: + nf_ct_helper_log(skb, ct, "cannot mangle packet"); + nf_ct_unexpect_related(exp); + return NF_DROP; +} + +static void __exit nf_nat_ftp_fini(void) +{ + nf_nat_helper_unregister(&nat_helper_ftp); + RCU_INIT_POINTER(nf_nat_ftp_hook, NULL); + synchronize_rcu(); +} + +static int __init nf_nat_ftp_init(void) +{ + BUG_ON(nf_nat_ftp_hook != NULL); + nf_nat_helper_register(&nat_helper_ftp); + RCU_INIT_POINTER(nf_nat_ftp_hook, nf_nat_ftp); + return 0; +} + +/* Prior to 2.6.11, we had a ports param. No longer, but don't break users. */ +static int warn_set(const char *val, const struct kernel_param *kp) +{ + pr_info("kernel >= 2.6.10 only uses 'ports' for conntrack modules\n"); + return 0; +} +module_param_call(ports, warn_set, NULL, NULL, 0); + +module_init(nf_nat_ftp_init); +module_exit(nf_nat_ftp_fini); |