| // 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; |
| |
| /* Try to get same port: if not, try to change it. */ |
| for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { |
| int ret; |
| |
| exp->tuple.dst.u.tcp.port = htons(port); |
| ret = nf_ct_expect_related(exp, 0); |
| if (ret == 0) |
| break; |
| else if (ret != -EBUSY) { |
| port = 0; |
| break; |
| } |
| } |
| |
| if (port == 0) { |
| nf_ct_helper_log(skb, ct, "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); |