How buggy this little piece of code could be? Repair strnvis() buffersize
[dragonfly.git] / lib / libalias / alias_pptp.c
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1/*
2 * alias_pptp.c
3 *
4 * Copyright (c) 2000 Whistle Communications, Inc.
5 * All rights reserved.
6 *
7 * Subject to the following obligations and disclaimer of warranty, use and
8 * redistribution of this software, in source or object code forms, with or
9 * without modifications are expressly permitted by Whistle Communications;
10 * provided, however, that:
11 * 1. Any and all reproductions of the source or object code must include the
12 * copyright notice above and the following disclaimer of warranties; and
13 * 2. No rights are granted, in any manner or form, to use Whistle
14 * Communications, Inc. trademarks, including the mark "WHISTLE
15 * COMMUNICATIONS" on advertising, endorsements, or otherwise except as
16 * such appears in the above copyright notice or in the software.
17 *
18 * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
19 * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
20 * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
21 * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
22 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
23 * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
24 * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
25 * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
26 * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
27 * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
28 * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
29 * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
30 * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
31 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
32 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
33 * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
34 * OF SUCH DAMAGE.
35 *
36 * Author: Erik Salander <erik@whistle.com>
37 *
38 * $FreeBSD: src/lib/libalias/alias_pptp.c,v 1.1.2.4 2001/08/01 09:52:27 obrien Exp $
9d509a69 39 * $DragonFly: src/lib/libalias/alias_pptp.c,v 1.3 2004/08/20 00:08:17 joerg Exp $
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40 */
41
42/*
43 Alias_pptp.c performs special processing for PPTP sessions under TCP.
44 Specifically, watch PPTP control messages and alias the Call ID or the
45 Peer's Call ID in the appropriate messages. Note, PPTP requires
46 "de-aliasing" of incoming packets, this is different than any other
47 TCP applications that are currently (ie. FTP, IRC and RTSP) aliased.
48
49 For Call IDs encountered for the first time, a PPTP alias link is created.
50 The PPTP alias link uses the Call ID in place of the original port number.
51 An alias Call ID is created.
52
53 For this routine to work, the PPTP control messages must fit entirely
54 into a single TCP packet. This is typically the case, but is not
55 required by the spec.
56
57 Unlike some of the other TCP applications that are aliased (ie. FTP,
58 IRC and RTSP), the PPTP control messages that need to be aliased are
59 guaranteed to remain the same length. The aliased Call ID is a fixed
60 length field.
61
62 Reference: RFC 2637
63
64 Initial version: May, 2000 (eds)
65
66*/
67
68/* Includes */
9d509a69 69#include <sys/param.h>
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70#include <netinet/in_systm.h>
71#include <netinet/in.h>
72#include <netinet/ip.h>
73#include <netinet/tcp.h>
74
75#include <stdio.h>
76
77#include "alias_local.h"
78
79/*
80 * PPTP definitions
81 */
82
83struct grehdr /* Enhanced GRE header. */
84{
85 u_int16_t gh_flags; /* Flags. */
86 u_int16_t gh_protocol; /* Protocol type. */
87 u_int16_t gh_length; /* Payload length. */
88 u_int16_t gh_call_id; /* Call ID. */
89 u_int32_t gh_seq_no; /* Sequence number (optional). */
90 u_int32_t gh_ack_no; /* Acknowledgment number (optional). */
91};
92typedef struct grehdr GreHdr;
93
94/* The PPTP protocol ID used in the GRE 'proto' field. */
95#define PPTP_GRE_PROTO 0x880b
96
97/* Bits that must be set a certain way in all PPTP/GRE packets. */
98#define PPTP_INIT_VALUE ((0x2001 << 16) | PPTP_GRE_PROTO)
99#define PPTP_INIT_MASK 0xef7fffff
100
101#define PPTP_MAGIC 0x1a2b3c4d
102#define PPTP_CTRL_MSG_TYPE 1
103
104enum {
105 PPTP_StartCtrlConnRequest = 1,
106 PPTP_StartCtrlConnReply = 2,
107 PPTP_StopCtrlConnRequest = 3,
108 PPTP_StopCtrlConnReply = 4,
109 PPTP_EchoRequest = 5,
110 PPTP_EchoReply = 6,
111 PPTP_OutCallRequest = 7,
112 PPTP_OutCallReply = 8,
113 PPTP_InCallRequest = 9,
114 PPTP_InCallReply = 10,
115 PPTP_InCallConn = 11,
116 PPTP_CallClearRequest = 12,
117 PPTP_CallDiscNotify = 13,
118 PPTP_WanErrorNotify = 14,
119 PPTP_SetLinkInfo = 15
120};
121
122 /* Message structures */
123 struct pptpMsgHead {
124 u_int16_t length; /* total length */
125 u_int16_t msgType; /* PPTP message type */
126 u_int32_t magic; /* magic cookie */
127 u_int16_t type; /* control message type */
128 u_int16_t resv0; /* reserved */
129 };
130 typedef struct pptpMsgHead *PptpMsgHead;
131
132 struct pptpCodes {
133 u_int8_t resCode; /* Result Code */
134 u_int8_t errCode; /* Error Code */
135 };
136 typedef struct pptpCodes *PptpCode;
137
138 struct pptpCallIds {
139 u_int16_t cid1; /* Call ID field #1 */
140 u_int16_t cid2; /* Call ID field #2 */
141 };
142 typedef struct pptpCallIds *PptpCallId;
143
144static PptpCallId AliasVerifyPptp(struct ip *, u_int16_t *);
145
146
147void
148AliasHandlePptpOut(struct ip *pip, /* IP packet to examine/patch */
149 struct alias_link *link) /* The PPTP control link */
150{
151 struct alias_link *pptp_link;
152 PptpCallId cptr;
153 PptpCode codes;
154 u_int16_t ctl_type; /* control message type */
155 struct tcphdr *tc;
156
157 /* Verify valid PPTP control message */
158 if ((cptr = AliasVerifyPptp(pip, &ctl_type)) == NULL)
159 return;
160
161 /* Modify certain PPTP messages */
162 switch (ctl_type) {
163 case PPTP_OutCallRequest:
164 case PPTP_OutCallReply:
165 case PPTP_InCallRequest:
166 case PPTP_InCallReply:
167 /* Establish PPTP link for address and Call ID found in control message. */
168 pptp_link = AddPptp(GetOriginalAddress(link), GetDestAddress(link),
169 GetAliasAddress(link), cptr->cid1);
170 break;
171 case PPTP_CallClearRequest:
172 case PPTP_CallDiscNotify:
173 /* Find PPTP link for address and Call ID found in control message. */
174 pptp_link = FindPptpOutByCallId(GetOriginalAddress(link),
175 GetDestAddress(link),
176 cptr->cid1);
177 break;
178 default:
179 return;
180 }
181
182 if (pptp_link != NULL) {
183 int accumulate = cptr->cid1;
184
185 /* alias the Call Id */
186 cptr->cid1 = GetAliasPort(pptp_link);
187
188 /* Compute TCP checksum for revised packet */
189 tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
190 accumulate -= cptr->cid1;
191 ADJUST_CHECKSUM(accumulate, tc->th_sum);
192
193 switch (ctl_type) {
194 case PPTP_OutCallReply:
195 case PPTP_InCallReply:
196 codes = (PptpCode)(cptr + 1);
197 if (codes->resCode == 1) /* Connection established, */
198 SetDestCallId(pptp_link, /* note the Peer's Call ID. */
199 cptr->cid2);
200 else
201 SetExpire(pptp_link, 0); /* Connection refused. */
202 break;
203 case PPTP_CallDiscNotify: /* Connection closed. */
204 SetExpire(pptp_link, 0);
205 break;
206 }
207 }
208}
209
210void
211AliasHandlePptpIn(struct ip *pip, /* IP packet to examine/patch */
212 struct alias_link *link) /* The PPTP control link */
213{
214 struct alias_link *pptp_link;
215 PptpCallId cptr;
216 u_int16_t *pcall_id;
217 u_int16_t ctl_type; /* control message type */
218 struct tcphdr *tc;
219
220 /* Verify valid PPTP control message */
221 if ((cptr = AliasVerifyPptp(pip, &ctl_type)) == NULL)
222 return;
223
224 /* Modify certain PPTP messages */
225 switch (ctl_type)
226 {
227 case PPTP_InCallConn:
228 case PPTP_WanErrorNotify:
229 case PPTP_SetLinkInfo:
230 pcall_id = &cptr->cid1;
231 break;
232 case PPTP_OutCallReply:
233 case PPTP_InCallReply:
234 pcall_id = &cptr->cid2;
235 break;
236 case PPTP_CallDiscNotify: /* Connection closed. */
237 pptp_link = FindPptpInByCallId(GetDestAddress(link),
238 GetAliasAddress(link),
239 cptr->cid1);
240 if (pptp_link != NULL)
241 SetExpire(pptp_link, 0);
242 return;
243 default:
244 return;
245 }
246
247 /* Find PPTP link for address and Call ID found in PPTP Control Msg */
248 pptp_link = FindPptpInByPeerCallId(GetDestAddress(link),
249 GetAliasAddress(link),
250 *pcall_id);
251
252 if (pptp_link != NULL) {
253 int accumulate = *pcall_id;
254
255 /* De-alias the Peer's Call Id. */
256 *pcall_id = GetOriginalPort(pptp_link);
257
258 /* Compute TCP checksum for modified packet */
259 tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
260 accumulate -= *pcall_id;
261 ADJUST_CHECKSUM(accumulate, tc->th_sum);
262
263 if (ctl_type == PPTP_OutCallReply || ctl_type == PPTP_InCallReply) {
264 PptpCode codes = (PptpCode)(cptr + 1);
265
266 if (codes->resCode == 1) /* Connection established, */
267 SetDestCallId(pptp_link, /* note the Call ID. */
268 cptr->cid1);
269 else
270 SetExpire(pptp_link, 0); /* Connection refused. */
271 }
272 }
273}
274
275static PptpCallId
276AliasVerifyPptp(struct ip *pip, u_int16_t *ptype) /* IP packet to examine/patch */
277{
278 int hlen, tlen, dlen;
279 PptpMsgHead hptr;
280 struct tcphdr *tc;
281
282 /* Calculate some lengths */
283 tc = (struct tcphdr *) ((char *) pip + (pip->ip_hl << 2));
284 hlen = (pip->ip_hl + tc->th_off) << 2;
285 tlen = ntohs(pip->ip_len);
286 dlen = tlen - hlen;
287
288 /* Verify data length */
289 if (dlen < (sizeof(struct pptpMsgHead) + sizeof(struct pptpCallIds)))
290 return(NULL);
291
292 /* Move up to PPTP message header */
293 hptr = (PptpMsgHead)(((char *) pip) + hlen);
294
295 /* Return the control message type */
296 *ptype = ntohs(hptr->type);
297
298 /* Verify PPTP Control Message */
299 if ((ntohs(hptr->msgType) != PPTP_CTRL_MSG_TYPE) ||
300 (ntohl(hptr->magic) != PPTP_MAGIC))
301 return(NULL);
302
303 /* Verify data length. */
304 if ((*ptype == PPTP_OutCallReply || *ptype == PPTP_InCallReply) &&
305 (dlen < sizeof(struct pptpMsgHead) + sizeof(struct pptpCallIds) +
306 sizeof(struct pptpCodes)))
307 return (NULL);
308 else
309 return (PptpCallId)(hptr + 1);
310}
311
312
313int
314AliasHandlePptpGreOut(struct ip *pip)
315{
316 GreHdr *gr;
317 struct alias_link *link;
318
319 gr = (GreHdr *)((char *)pip + (pip->ip_hl << 2));
320
321 /* Check GRE header bits. */
322 if ((ntohl(*((u_int32_t *)gr)) & PPTP_INIT_MASK) != PPTP_INIT_VALUE)
323 return (-1);
324
325 link = FindPptpOutByPeerCallId(pip->ip_src, pip->ip_dst, gr->gh_call_id);
326 if (link != NULL) {
327 struct in_addr alias_addr = GetAliasAddress(link);
328
329 /* Change source IP address. */
330 DifferentialChecksum(&pip->ip_sum,
331 (u_short *)&alias_addr,
332 (u_short *)&pip->ip_src,
333 2);
334 pip->ip_src = alias_addr;
335 }
336
337 return (0);
338}
339
340
341int
342AliasHandlePptpGreIn(struct ip *pip)
343{
344 GreHdr *gr;
345 struct alias_link *link;
346
347 gr = (GreHdr *)((char *)pip + (pip->ip_hl << 2));
348
349 /* Check GRE header bits. */
350 if ((ntohl(*((u_int32_t *)gr)) & PPTP_INIT_MASK) != PPTP_INIT_VALUE)
351 return (-1);
352
353 link = FindPptpInByPeerCallId(pip->ip_src, pip->ip_dst, gr->gh_call_id);
354 if (link != NULL) {
355 struct in_addr src_addr = GetOriginalAddress(link);
356
357 /* De-alias the Peer's Call Id. */
358 gr->gh_call_id = GetOriginalPort(link);
359
360 /* Restore original IP address. */
361 DifferentialChecksum(&pip->ip_sum,
362 (u_short *)&src_addr,
363 (u_short *)&pip->ip_dst,
364 2);
365 pip->ip_dst = src_addr;
366 }
367
368 return (0);
369}