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- /*
- * nf_nat_pptp.c
- *
- * NAT support for PPTP (Point to Point Tunneling Protocol).
- * PPTP is a a protocol for creating virtual private networks.
- * It is a specification defined by Microsoft and some vendors
- * working with Microsoft. PPTP is built on top of a modified
- * version of the Internet Generic Routing Encapsulation Protocol.
- * GRE is defined in RFC 1701 and RFC 1702. Documentation of
- * PPTP can be found in RFC 2637
- *
- * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
- *
- * Development of this code funded by Astaro AG (http://www.astaro.com/)
- *
- * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
- *
- * TODO: - NAT to a unique tuple, not to TCP source port
- * (needs netfilter tuple reservation)
- */
- #include <linux/module.h>
- #include <linux/tcp.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 <net/netfilter/nf_conntrack_zones.h>
- #include <linux/netfilter/nf_conntrack_proto_gre.h>
- #include <linux/netfilter/nf_conntrack_pptp.h>
- #define NF_NAT_PPTP_VERSION "3.0"
- #define REQ_CID(req, off) (*(__be16 *)((char *)(req) + (off)))
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
- MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP");
- MODULE_ALIAS("ip_nat_pptp");
- static void pptp_nat_expected(struct nf_conn *ct,
- struct nf_conntrack_expect *exp)
- {
- struct net *net = nf_ct_net(ct);
- const struct nf_conn *master = ct->master;
- struct nf_conntrack_expect *other_exp;
- struct nf_conntrack_tuple t = {};
- const struct nf_ct_pptp_master *ct_pptp_info;
- const struct nf_nat_pptp *nat_pptp_info;
- struct nf_nat_range range;
- ct_pptp_info = nfct_help_data(master);
- nat_pptp_info = &nfct_nat(master)->help.nat_pptp_info;
- /* And here goes the grand finale of corrosion... */
- if (exp->dir == IP_CT_DIR_ORIGINAL) {
- pr_debug("we are PNS->PAC\n");
- /* therefore, build tuple for PAC->PNS */
- t.src.l3num = AF_INET;
- t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip;
- t.src.u.gre.key = ct_pptp_info->pac_call_id;
- t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip;
- t.dst.u.gre.key = ct_pptp_info->pns_call_id;
- t.dst.protonum = IPPROTO_GRE;
- } else {
- pr_debug("we are PAC->PNS\n");
- /* build tuple for PNS->PAC */
- t.src.l3num = AF_INET;
- t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip;
- t.src.u.gre.key = nat_pptp_info->pns_call_id;
- t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip;
- t.dst.u.gre.key = nat_pptp_info->pac_call_id;
- t.dst.protonum = IPPROTO_GRE;
- }
- pr_debug("trying to unexpect other dir: ");
- nf_ct_dump_tuple_ip(&t);
- other_exp = nf_ct_expect_find_get(net, nf_ct_zone(ct), &t);
- if (other_exp) {
- nf_ct_unexpect_related(other_exp);
- nf_ct_expect_put(other_exp);
- pr_debug("success\n");
- } else {
- pr_debug("not found!\n");
- }
- /* This must be a fresh one. */
- BUG_ON(ct->status & IPS_NAT_DONE_MASK);
- /* Change src to where master sends to */
- range.flags = NF_NAT_RANGE_MAP_IPS;
- range.min_addr = range.max_addr
- = ct->master->tuplehash[!exp->dir].tuple.dst.u3;
- if (exp->dir == IP_CT_DIR_ORIGINAL) {
- range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
- range.min_proto = range.max_proto = exp->saved_proto;
- }
- nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC);
- /* For DST manip, map port here to where it's expected. */
- range.flags = NF_NAT_RANGE_MAP_IPS;
- range.min_addr = range.max_addr
- = ct->master->tuplehash[!exp->dir].tuple.src.u3;
- if (exp->dir == IP_CT_DIR_REPLY) {
- range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
- range.min_proto = range.max_proto = exp->saved_proto;
- }
- nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST);
- }
- /* outbound packets == from PNS to PAC */
- static int
- pptp_outbound_pkt(struct sk_buff *skb,
- struct nf_conn *ct,
- enum ip_conntrack_info ctinfo,
- unsigned int protoff,
- struct PptpControlHeader *ctlh,
- union pptp_ctrl_union *pptpReq)
- {
- struct nf_ct_pptp_master *ct_pptp_info;
- struct nf_nat_pptp *nat_pptp_info;
- u_int16_t msg;
- __be16 new_callid;
- unsigned int cid_off;
- ct_pptp_info = nfct_help_data(ct);
- nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
- new_callid = ct_pptp_info->pns_call_id;
- switch (msg = ntohs(ctlh->messageType)) {
- case PPTP_OUT_CALL_REQUEST:
- cid_off = offsetof(union pptp_ctrl_union, ocreq.callID);
- /* FIXME: ideally we would want to reserve a call ID
- * here. current netfilter NAT core is not able to do
- * this :( For now we use TCP source port. This breaks
- * multiple calls within one control session */
- /* save original call ID in nat_info */
- nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id;
- /* don't use tcph->source since we are at a DSTmanip
- * hook (e.g. PREROUTING) and pkt is not mangled yet */
- new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port;
- /* save new call ID in ct info */
- ct_pptp_info->pns_call_id = new_callid;
- break;
- case PPTP_IN_CALL_REPLY:
- cid_off = offsetof(union pptp_ctrl_union, icack.callID);
- break;
- case PPTP_CALL_CLEAR_REQUEST:
- cid_off = offsetof(union pptp_ctrl_union, clrreq.callID);
- break;
- default:
- pr_debug("unknown outbound packet 0x%04x:%s\n", msg,
- msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] :
- pptp_msg_name[0]);
- /* fall through */
- case PPTP_SET_LINK_INFO:
- /* only need to NAT in case PAC is behind NAT box */
- case PPTP_START_SESSION_REQUEST:
- case PPTP_START_SESSION_REPLY:
- case PPTP_STOP_SESSION_REQUEST:
- case PPTP_STOP_SESSION_REPLY:
- case PPTP_ECHO_REQUEST:
- case PPTP_ECHO_REPLY:
- /* no need to alter packet */
- return NF_ACCEPT;
- }
- /* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass
- * down to here */
- pr_debug("altering call id from 0x%04x to 0x%04x\n",
- ntohs(REQ_CID(pptpReq, cid_off)), ntohs(new_callid));
- /* mangle packet */
- if (nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff,
- cid_off + sizeof(struct pptp_pkt_hdr) +
- sizeof(struct PptpControlHeader),
- sizeof(new_callid), (char *)&new_callid,
- sizeof(new_callid)) == 0)
- return NF_DROP;
- return NF_ACCEPT;
- }
- static void
- pptp_exp_gre(struct nf_conntrack_expect *expect_orig,
- struct nf_conntrack_expect *expect_reply)
- {
- const struct nf_conn *ct = expect_orig->master;
- struct nf_ct_pptp_master *ct_pptp_info;
- struct nf_nat_pptp *nat_pptp_info;
- ct_pptp_info = nfct_help_data(ct);
- nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
- /* save original PAC call ID in nat_info */
- nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
- /* alter expectation for PNS->PAC direction */
- expect_orig->saved_proto.gre.key = ct_pptp_info->pns_call_id;
- expect_orig->tuple.src.u.gre.key = nat_pptp_info->pns_call_id;
- expect_orig->tuple.dst.u.gre.key = ct_pptp_info->pac_call_id;
- expect_orig->dir = IP_CT_DIR_ORIGINAL;
- /* alter expectation for PAC->PNS direction */
- expect_reply->saved_proto.gre.key = nat_pptp_info->pns_call_id;
- expect_reply->tuple.src.u.gre.key = nat_pptp_info->pac_call_id;
- expect_reply->tuple.dst.u.gre.key = ct_pptp_info->pns_call_id;
- expect_reply->dir = IP_CT_DIR_REPLY;
- }
- /* inbound packets == from PAC to PNS */
- static int
- pptp_inbound_pkt(struct sk_buff *skb,
- struct nf_conn *ct,
- enum ip_conntrack_info ctinfo,
- unsigned int protoff,
- struct PptpControlHeader *ctlh,
- union pptp_ctrl_union *pptpReq)
- {
- const struct nf_nat_pptp *nat_pptp_info;
- u_int16_t msg;
- __be16 new_pcid;
- unsigned int pcid_off;
- nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
- new_pcid = nat_pptp_info->pns_call_id;
- switch (msg = ntohs(ctlh->messageType)) {
- case PPTP_OUT_CALL_REPLY:
- pcid_off = offsetof(union pptp_ctrl_union, ocack.peersCallID);
- break;
- case PPTP_IN_CALL_CONNECT:
- pcid_off = offsetof(union pptp_ctrl_union, iccon.peersCallID);
- break;
- case PPTP_IN_CALL_REQUEST:
- /* only need to nat in case PAC is behind NAT box */
- return NF_ACCEPT;
- case PPTP_WAN_ERROR_NOTIFY:
- pcid_off = offsetof(union pptp_ctrl_union, wanerr.peersCallID);
- break;
- case PPTP_CALL_DISCONNECT_NOTIFY:
- pcid_off = offsetof(union pptp_ctrl_union, disc.callID);
- break;
- case PPTP_SET_LINK_INFO:
- pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID);
- break;
- default:
- pr_debug("unknown inbound packet %s\n",
- msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] :
- pptp_msg_name[0]);
- /* fall through */
- case PPTP_START_SESSION_REQUEST:
- case PPTP_START_SESSION_REPLY:
- case PPTP_STOP_SESSION_REQUEST:
- case PPTP_STOP_SESSION_REPLY:
- case PPTP_ECHO_REQUEST:
- case PPTP_ECHO_REPLY:
- /* no need to alter packet */
- return NF_ACCEPT;
- }
- /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST,
- * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */
- /* mangle packet */
- pr_debug("altering peer call id from 0x%04x to 0x%04x\n",
- ntohs(REQ_CID(pptpReq, pcid_off)), ntohs(new_pcid));
- if (nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff,
- pcid_off + sizeof(struct pptp_pkt_hdr) +
- sizeof(struct PptpControlHeader),
- sizeof(new_pcid), (char *)&new_pcid,
- sizeof(new_pcid)) == 0)
- return NF_DROP;
- return NF_ACCEPT;
- }
- static int __init nf_nat_helper_pptp_init(void)
- {
- nf_nat_need_gre();
- BUG_ON(nf_nat_pptp_hook_outbound != NULL);
- RCU_INIT_POINTER(nf_nat_pptp_hook_outbound, pptp_outbound_pkt);
- BUG_ON(nf_nat_pptp_hook_inbound != NULL);
- RCU_INIT_POINTER(nf_nat_pptp_hook_inbound, pptp_inbound_pkt);
- BUG_ON(nf_nat_pptp_hook_exp_gre != NULL);
- RCU_INIT_POINTER(nf_nat_pptp_hook_exp_gre, pptp_exp_gre);
- BUG_ON(nf_nat_pptp_hook_expectfn != NULL);
- RCU_INIT_POINTER(nf_nat_pptp_hook_expectfn, pptp_nat_expected);
- return 0;
- }
- static void __exit nf_nat_helper_pptp_fini(void)
- {
- RCU_INIT_POINTER(nf_nat_pptp_hook_expectfn, NULL);
- RCU_INIT_POINTER(nf_nat_pptp_hook_exp_gre, NULL);
- RCU_INIT_POINTER(nf_nat_pptp_hook_inbound, NULL);
- RCU_INIT_POINTER(nf_nat_pptp_hook_outbound, NULL);
- synchronize_rcu();
- }
- module_init(nf_nat_helper_pptp_init);
- module_exit(nf_nat_helper_pptp_fini);
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