]>
Commit | Line | Data |
---|---|---|
f09943fe PM |
1 | /* |
2 | * nf_nat_pptp.c | |
3 | * | |
4 | * NAT support for PPTP (Point to Point Tunneling Protocol). | |
5 | * PPTP is a a protocol for creating virtual private networks. | |
6 | * It is a specification defined by Microsoft and some vendors | |
7 | * working with Microsoft. PPTP is built on top of a modified | |
8 | * version of the Internet Generic Routing Encapsulation Protocol. | |
9 | * GRE is defined in RFC 1701 and RFC 1702. Documentation of | |
10 | * PPTP can be found in RFC 2637 | |
11 | * | |
12 | * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org> | |
13 | * | |
14 | * Development of this code funded by Astaro AG (http://www.astaro.com/) | |
15 | * | |
16 | * TODO: - NAT to a unique tuple, not to TCP source port | |
17 | * (needs netfilter tuple reservation) | |
18 | */ | |
19 | ||
20 | #include <linux/module.h> | |
21 | #include <linux/tcp.h> | |
22 | ||
23 | #include <net/netfilter/nf_nat.h> | |
24 | #include <net/netfilter/nf_nat_helper.h> | |
25 | #include <net/netfilter/nf_nat_rule.h> | |
26 | #include <net/netfilter/nf_conntrack_helper.h> | |
27 | #include <net/netfilter/nf_conntrack_expect.h> | |
28 | #include <linux/netfilter/nf_conntrack_proto_gre.h> | |
29 | #include <linux/netfilter/nf_conntrack_pptp.h> | |
30 | ||
31 | #define NF_NAT_PPTP_VERSION "3.0" | |
32 | ||
33 | #define REQ_CID(req, off) (*(__be16 *)((char *)(req) + (off))) | |
34 | ||
35 | MODULE_LICENSE("GPL"); | |
36 | MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>"); | |
37 | MODULE_DESCRIPTION("Netfilter NAT helper module for PPTP"); | |
38 | MODULE_ALIAS("ip_nat_pptp"); | |
39 | ||
40 | #if 0 | |
41 | extern const char *pptp_msg_name[]; | |
42 | #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, \ | |
43 | __FUNCTION__, ## args) | |
44 | #else | |
45 | #define DEBUGP(format, args...) | |
46 | #endif | |
47 | ||
48 | static void pptp_nat_expected(struct nf_conn *ct, | |
49 | struct nf_conntrack_expect *exp) | |
50 | { | |
51 | struct nf_conn *master = ct->master; | |
52 | struct nf_conntrack_expect *other_exp; | |
53 | struct nf_conntrack_tuple t; | |
54 | struct nf_ct_pptp_master *ct_pptp_info; | |
55 | struct nf_nat_pptp *nat_pptp_info; | |
587aa641 | 56 | struct nf_nat_range range; |
f09943fe PM |
57 | |
58 | ct_pptp_info = &nfct_help(master)->help.ct_pptp_info; | |
59 | nat_pptp_info = &nfct_nat(master)->help.nat_pptp_info; | |
60 | ||
61 | /* And here goes the grand finale of corrosion... */ | |
62 | if (exp->dir == IP_CT_DIR_ORIGINAL) { | |
63 | DEBUGP("we are PNS->PAC\n"); | |
64 | /* therefore, build tuple for PAC->PNS */ | |
65 | t.src.l3num = AF_INET; | |
66 | t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip; | |
67 | t.src.u.gre.key = ct_pptp_info->pac_call_id; | |
68 | t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip; | |
69 | t.dst.u.gre.key = ct_pptp_info->pns_call_id; | |
70 | t.dst.protonum = IPPROTO_GRE; | |
71 | } else { | |
72 | DEBUGP("we are PAC->PNS\n"); | |
73 | /* build tuple for PNS->PAC */ | |
74 | t.src.l3num = AF_INET; | |
a46bf7d5 | 75 | t.src.u3.ip = master->tuplehash[!exp->dir].tuple.src.u3.ip; |
f09943fe | 76 | t.src.u.gre.key = nat_pptp_info->pns_call_id; |
a46bf7d5 | 77 | t.dst.u3.ip = master->tuplehash[!exp->dir].tuple.dst.u3.ip; |
f09943fe PM |
78 | t.dst.u.gre.key = nat_pptp_info->pac_call_id; |
79 | t.dst.protonum = IPPROTO_GRE; | |
80 | } | |
81 | ||
82 | DEBUGP("trying to unexpect other dir: "); | |
83 | NF_CT_DUMP_TUPLE(&t); | |
6823645d | 84 | other_exp = nf_ct_expect_find_get(&t); |
f09943fe | 85 | if (other_exp) { |
6823645d PM |
86 | nf_ct_unexpect_related(other_exp); |
87 | nf_ct_expect_put(other_exp); | |
f09943fe PM |
88 | DEBUGP("success\n"); |
89 | } else { | |
90 | DEBUGP("not found!\n"); | |
91 | } | |
92 | ||
93 | /* This must be a fresh one. */ | |
94 | BUG_ON(ct->status & IPS_NAT_DONE_MASK); | |
95 | ||
96 | /* Change src to where master sends to */ | |
97 | range.flags = IP_NAT_RANGE_MAP_IPS; | |
98 | range.min_ip = range.max_ip | |
99 | = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip; | |
100 | if (exp->dir == IP_CT_DIR_ORIGINAL) { | |
101 | range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED; | |
102 | range.min = range.max = exp->saved_proto; | |
103 | } | |
104 | /* hook doesn't matter, but it has to do source manip */ | |
105 | nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING); | |
106 | ||
107 | /* For DST manip, map port here to where it's expected. */ | |
108 | range.flags = IP_NAT_RANGE_MAP_IPS; | |
109 | range.min_ip = range.max_ip | |
110 | = ct->master->tuplehash[!exp->dir].tuple.src.u3.ip; | |
111 | if (exp->dir == IP_CT_DIR_REPLY) { | |
112 | range.flags |= IP_NAT_RANGE_PROTO_SPECIFIED; | |
113 | range.min = range.max = exp->saved_proto; | |
114 | } | |
115 | /* hook doesn't matter, but it has to do destination manip */ | |
116 | nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING); | |
117 | } | |
118 | ||
119 | /* outbound packets == from PNS to PAC */ | |
120 | static int | |
121 | pptp_outbound_pkt(struct sk_buff **pskb, | |
122 | struct nf_conn *ct, | |
123 | enum ip_conntrack_info ctinfo, | |
124 | struct PptpControlHeader *ctlh, | |
125 | union pptp_ctrl_union *pptpReq) | |
126 | ||
127 | { | |
128 | struct nf_ct_pptp_master *ct_pptp_info; | |
129 | struct nf_nat_pptp *nat_pptp_info; | |
130 | u_int16_t msg; | |
131 | __be16 new_callid; | |
132 | unsigned int cid_off; | |
133 | ||
134 | ct_pptp_info = &nfct_help(ct)->help.ct_pptp_info; | |
135 | nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info; | |
136 | ||
137 | new_callid = ct_pptp_info->pns_call_id; | |
138 | ||
139 | switch (msg = ntohs(ctlh->messageType)) { | |
140 | case PPTP_OUT_CALL_REQUEST: | |
141 | cid_off = offsetof(union pptp_ctrl_union, ocreq.callID); | |
142 | /* FIXME: ideally we would want to reserve a call ID | |
143 | * here. current netfilter NAT core is not able to do | |
144 | * this :( For now we use TCP source port. This breaks | |
145 | * multiple calls within one control session */ | |
146 | ||
147 | /* save original call ID in nat_info */ | |
148 | nat_pptp_info->pns_call_id = ct_pptp_info->pns_call_id; | |
149 | ||
150 | /* don't use tcph->source since we are at a DSTmanip | |
151 | * hook (e.g. PREROUTING) and pkt is not mangled yet */ | |
152 | new_callid = ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.tcp.port; | |
153 | ||
154 | /* save new call ID in ct info */ | |
155 | ct_pptp_info->pns_call_id = new_callid; | |
156 | break; | |
157 | case PPTP_IN_CALL_REPLY: | |
158 | cid_off = offsetof(union pptp_ctrl_union, icack.callID); | |
159 | break; | |
160 | case PPTP_CALL_CLEAR_REQUEST: | |
161 | cid_off = offsetof(union pptp_ctrl_union, clrreq.callID); | |
162 | break; | |
163 | default: | |
164 | DEBUGP("unknown outbound packet 0x%04x:%s\n", msg, | |
165 | (msg <= PPTP_MSG_MAX)? | |
166 | pptp_msg_name[msg]:pptp_msg_name[0]); | |
167 | /* fall through */ | |
168 | case PPTP_SET_LINK_INFO: | |
169 | /* only need to NAT in case PAC is behind NAT box */ | |
170 | case PPTP_START_SESSION_REQUEST: | |
171 | case PPTP_START_SESSION_REPLY: | |
172 | case PPTP_STOP_SESSION_REQUEST: | |
173 | case PPTP_STOP_SESSION_REPLY: | |
174 | case PPTP_ECHO_REQUEST: | |
175 | case PPTP_ECHO_REPLY: | |
176 | /* no need to alter packet */ | |
177 | return NF_ACCEPT; | |
178 | } | |
179 | ||
180 | /* only OUT_CALL_REQUEST, IN_CALL_REPLY, CALL_CLEAR_REQUEST pass | |
181 | * down to here */ | |
182 | DEBUGP("altering call id from 0x%04x to 0x%04x\n", | |
183 | ntohs(REQ_CID(pptpReq, cid_off)), ntohs(new_callid)); | |
184 | ||
185 | /* mangle packet */ | |
186 | if (nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, | |
e905a9ed YH |
187 | cid_off + sizeof(struct pptp_pkt_hdr) + |
188 | sizeof(struct PptpControlHeader), | |
189 | sizeof(new_callid), (char *)&new_callid, | |
190 | sizeof(new_callid)) == 0) | |
f09943fe PM |
191 | return NF_DROP; |
192 | return NF_ACCEPT; | |
193 | } | |
194 | ||
195 | static void | |
196 | pptp_exp_gre(struct nf_conntrack_expect *expect_orig, | |
197 | struct nf_conntrack_expect *expect_reply) | |
198 | { | |
199 | struct nf_conn *ct = expect_orig->master; | |
200 | struct nf_ct_pptp_master *ct_pptp_info; | |
201 | struct nf_nat_pptp *nat_pptp_info; | |
202 | ||
203 | ct_pptp_info = &nfct_help(ct)->help.ct_pptp_info; | |
204 | nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info; | |
205 | ||
206 | /* save original PAC call ID in nat_info */ | |
207 | nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id; | |
208 | ||
209 | /* alter expectation for PNS->PAC direction */ | |
210 | expect_orig->saved_proto.gre.key = ct_pptp_info->pns_call_id; | |
211 | expect_orig->tuple.src.u.gre.key = nat_pptp_info->pns_call_id; | |
212 | expect_orig->tuple.dst.u.gre.key = ct_pptp_info->pac_call_id; | |
213 | expect_orig->dir = IP_CT_DIR_ORIGINAL; | |
214 | ||
215 | /* alter expectation for PAC->PNS direction */ | |
216 | expect_reply->saved_proto.gre.key = nat_pptp_info->pns_call_id; | |
217 | expect_reply->tuple.src.u.gre.key = nat_pptp_info->pac_call_id; | |
218 | expect_reply->tuple.dst.u.gre.key = ct_pptp_info->pns_call_id; | |
219 | expect_reply->dir = IP_CT_DIR_REPLY; | |
220 | } | |
221 | ||
222 | /* inbound packets == from PAC to PNS */ | |
223 | static int | |
224 | pptp_inbound_pkt(struct sk_buff **pskb, | |
225 | struct nf_conn *ct, | |
226 | enum ip_conntrack_info ctinfo, | |
227 | struct PptpControlHeader *ctlh, | |
228 | union pptp_ctrl_union *pptpReq) | |
229 | { | |
230 | struct nf_nat_pptp *nat_pptp_info; | |
231 | u_int16_t msg; | |
232 | __be16 new_pcid; | |
233 | unsigned int pcid_off; | |
234 | ||
235 | nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info; | |
236 | new_pcid = nat_pptp_info->pns_call_id; | |
237 | ||
238 | switch (msg = ntohs(ctlh->messageType)) { | |
239 | case PPTP_OUT_CALL_REPLY: | |
240 | pcid_off = offsetof(union pptp_ctrl_union, ocack.peersCallID); | |
241 | break; | |
242 | case PPTP_IN_CALL_CONNECT: | |
243 | pcid_off = offsetof(union pptp_ctrl_union, iccon.peersCallID); | |
244 | break; | |
245 | case PPTP_IN_CALL_REQUEST: | |
246 | /* only need to nat in case PAC is behind NAT box */ | |
247 | return NF_ACCEPT; | |
248 | case PPTP_WAN_ERROR_NOTIFY: | |
249 | pcid_off = offsetof(union pptp_ctrl_union, wanerr.peersCallID); | |
250 | break; | |
251 | case PPTP_CALL_DISCONNECT_NOTIFY: | |
252 | pcid_off = offsetof(union pptp_ctrl_union, disc.callID); | |
253 | break; | |
254 | case PPTP_SET_LINK_INFO: | |
255 | pcid_off = offsetof(union pptp_ctrl_union, setlink.peersCallID); | |
256 | break; | |
257 | default: | |
258 | DEBUGP("unknown inbound packet %s\n", (msg <= PPTP_MSG_MAX)? | |
259 | pptp_msg_name[msg]:pptp_msg_name[0]); | |
260 | /* fall through */ | |
261 | case PPTP_START_SESSION_REQUEST: | |
262 | case PPTP_START_SESSION_REPLY: | |
263 | case PPTP_STOP_SESSION_REQUEST: | |
264 | case PPTP_STOP_SESSION_REPLY: | |
265 | case PPTP_ECHO_REQUEST: | |
266 | case PPTP_ECHO_REPLY: | |
267 | /* no need to alter packet */ | |
268 | return NF_ACCEPT; | |
269 | } | |
270 | ||
271 | /* only OUT_CALL_REPLY, IN_CALL_CONNECT, IN_CALL_REQUEST, | |
272 | * WAN_ERROR_NOTIFY, CALL_DISCONNECT_NOTIFY pass down here */ | |
273 | ||
274 | /* mangle packet */ | |
275 | DEBUGP("altering peer call id from 0x%04x to 0x%04x\n", | |
276 | ntohs(REQ_CID(pptpReq, pcid_off)), ntohs(new_pcid)); | |
277 | ||
278 | if (nf_nat_mangle_tcp_packet(pskb, ct, ctinfo, | |
e905a9ed | 279 | pcid_off + sizeof(struct pptp_pkt_hdr) + |
f09943fe PM |
280 | sizeof(struct PptpControlHeader), |
281 | sizeof(new_pcid), (char *)&new_pcid, | |
282 | sizeof(new_pcid)) == 0) | |
283 | return NF_DROP; | |
284 | return NF_ACCEPT; | |
285 | } | |
286 | ||
287 | static int __init nf_nat_helper_pptp_init(void) | |
288 | { | |
289 | nf_nat_need_gre(); | |
290 | ||
291 | BUG_ON(rcu_dereference(nf_nat_pptp_hook_outbound)); | |
292 | rcu_assign_pointer(nf_nat_pptp_hook_outbound, pptp_outbound_pkt); | |
293 | ||
294 | BUG_ON(rcu_dereference(nf_nat_pptp_hook_inbound)); | |
295 | rcu_assign_pointer(nf_nat_pptp_hook_inbound, pptp_inbound_pkt); | |
296 | ||
297 | BUG_ON(rcu_dereference(nf_nat_pptp_hook_exp_gre)); | |
298 | rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, pptp_exp_gre); | |
299 | ||
300 | BUG_ON(rcu_dereference(nf_nat_pptp_hook_expectfn)); | |
301 | rcu_assign_pointer(nf_nat_pptp_hook_expectfn, pptp_nat_expected); | |
302 | return 0; | |
303 | } | |
304 | ||
305 | static void __exit nf_nat_helper_pptp_fini(void) | |
306 | { | |
307 | rcu_assign_pointer(nf_nat_pptp_hook_expectfn, NULL); | |
308 | rcu_assign_pointer(nf_nat_pptp_hook_exp_gre, NULL); | |
309 | rcu_assign_pointer(nf_nat_pptp_hook_inbound, NULL); | |
310 | rcu_assign_pointer(nf_nat_pptp_hook_outbound, NULL); | |
311 | synchronize_rcu(); | |
312 | } | |
313 | ||
314 | module_init(nf_nat_helper_pptp_init); | |
315 | module_exit(nf_nat_helper_pptp_fini); |