| /* |
| * 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/) |
| * |
| * 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_nat_rule.h> |
| #include <net/netfilter/nf_conntrack_helper.h> |
| #include <net/netfilter/nf_conntrack_expect.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 nf_conn *master = ct->master; |
| struct nf_conntrack_expect *other_exp; |
| struct nf_conntrack_tuple t; |
| struct nf_ct_pptp_master *ct_pptp_info; |
| struct nf_nat_pptp *nat_pptp_info; |
| struct nf_nat_range range; |
| |
| ct_pptp_info = &nfct_help(master)->help.ct_pptp_info; |
| 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(&t); |
| other_exp = nf_ct_expect_find_get(&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 = IP_NAT_RANGE_MAP_IPS; |
| range.min_ip = range.max_ip |
| = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip; |
| if (exp->dir == IP_CT_DIR_ORIGINAL) { |
| range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED; |
| range.min = range.max = exp->saved_proto; |
| } |
| nf_nat_setup_info(ct, &range, IP_NAT_MANIP_SRC); |
| |
| /* For DST manip, map port here to where it's expected. */ |
| range.flags = IP_NAT_RANGE_MAP_IPS; |
| range.min_ip = range.max_ip |
| = ct->master->tuplehash[!exp->dir].tuple.src.u3.ip; |
| if (exp->dir == IP_CT_DIR_REPLY) { |
| range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED; |
| range.min = range.max = exp->saved_proto; |
| } |
| nf_nat_setup_info(ct, &range, IP_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, |
| 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(ct)->help.ct_pptp_info; |
| 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, |
| 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) |
| { |
| 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(ct)->help.ct_pptp_info; |
| 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, |
| struct PptpControlHeader *ctlh, |
| union pptp_ctrl_union *pptpReq) |
| { |
| 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, |
| 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_assign_pointer(nf_nat_pptp_hook_outbound, pptp_outbound_pkt); |
| |
| BUG_ON(nf_nat_pptp_hook_inbound != NULL); |
| rcu_assign_pointer(nf_nat_pptp_hook_inbound, pptp_inbound_pkt); |
| |
| BUG_ON(nf_nat_pptp_hook_exp_gre != NULL); |
| rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, pptp_exp_gre); |
| |
| BUG_ON(nf_nat_pptp_hook_expectfn != NULL); |
| rcu_assign_pointer(nf_nat_pptp_hook_expectfn, pptp_nat_expected); |
| return 0; |
| } |
| |
| static void __exit nf_nat_helper_pptp_fini(void) |
| { |
| rcu_assign_pointer(nf_nat_pptp_hook_expectfn, NULL); |
| rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, NULL); |
| rcu_assign_pointer(nf_nat_pptp_hook_inbound, NULL); |
| rcu_assign_pointer(nf_nat_pptp_hook_outbound, NULL); |
| synchronize_rcu(); |
| } |
| |
| module_init(nf_nat_helper_pptp_init); |
| module_exit(nf_nat_helper_pptp_fini); |