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[NETFILTER]: nf_conntrack_expect: support inactive expectations
[deliverable/linux.git] / net / ipv4 / netfilter / nf_nat_snmp_basic.c
CommitLineData
807467c2
PM		 1/*
2 * nf_nat_snmp_basic.c
3 *
4 * Basic SNMP Application Layer Gateway
5 *
6 * This IP NAT module is intended for use with SNMP network
7 * discovery and monitoring applications where target networks use
8 * conflicting private address realms.
9 *
10 * Static NAT is used to remap the networks from the view of the network
11 * management system at the IP layer, and this module remaps some application
12 * layer addresses to match.
13 *
14 * The simplest form of ALG is performed, where only tagged IP addresses
15 * are modified. The module does not need to be MIB aware and only scans
16 * messages at the ASN.1/BER level.
17 *
18 * Currently, only SNMPv1 and SNMPv2 are supported.
19 *
20 * More information on ALG and associated issues can be found in
21 * RFC 2962
22 *
23 * The ASB.1/BER parsing code is derived from the gxsnmp package by Gregory
24 * McLean & Jochen Friedrich, stripped down for use in the kernel.
25 *
26 * Copyright (c) 2000 RP Internet (www.rpi.net.au).
27 *
28 * This program is free software; you can redistribute it and/or modify
29 * it under the terms of the GNU General Public License as published by
30 * the Free Software Foundation; either version 2 of the License, or
31 * (at your option) any later version.
32 * This program is distributed in the hope that it will be useful,
33 * but WITHOUT ANY WARRANTY; without even the implied warranty of
34 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
35 * GNU General Public License for more details.
36 * You should have received a copy of the GNU General Public License
37 * along with this program; if not, write to the Free Software
38 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
39 *
40 * Author: James Morris <jmorris@intercode.com.au>
807467c2
PM		 41 */
42#include <linux/module.h>
43#include <linux/moduleparam.h>
44#include <linux/types.h>
45#include <linux/kernel.h>
46#include <linux/in.h>
47#include <linux/ip.h>
48#include <linux/udp.h>
49#include <net/checksum.h>
50#include <net/udp.h>
51
52#include <net/netfilter/nf_nat.h>
53#include <net/netfilter/nf_conntrack_helper.h>
54#include <net/netfilter/nf_nat_helper.h>
55
56MODULE_LICENSE("GPL");
57MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
58MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
59MODULE_ALIAS("ip_nat_snmp_basic");
60
61#define SNMP_PORT 161
62#define SNMP_TRAP_PORT 162
e79ec50b 63#define NOCT1(n) (*(u8 *)(n))
807467c2
PM		 64
65static int debug;
66static DEFINE_SPINLOCK(snmp_lock);
67
68/*
69 * Application layer address mapping mimics the NAT mapping, but
70 * only for the first octet in this case (a more flexible system
71 * can be implemented if needed).
72 */
73struct oct1_map
74{
75 u_int8_t from;
76 u_int8_t to;
77};
78
79
80/*****************************************************************************
81 *
82 * Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
83 *
84 *****************************************************************************/
85
86/* Class */
87#define ASN1_UNI 0 /* Universal */
88#define ASN1_APL 1 /* Application */
89#define ASN1_CTX 2 /* Context */
90#define ASN1_PRV 3 /* Private */
91
92/* Tag */
93#define ASN1_EOC 0 /* End Of Contents */
94#define ASN1_BOL 1 /* Boolean */
95#define ASN1_INT 2 /* Integer */
96#define ASN1_BTS 3 /* Bit String */
97#define ASN1_OTS 4 /* Octet String */
98#define ASN1_NUL 5 /* Null */
99#define ASN1_OJI 6 /* Object Identifier */
100#define ASN1_OJD 7 /* Object Description */
101#define ASN1_EXT 8 /* External */
102#define ASN1_SEQ 16 /* Sequence */
103#define ASN1_SET 17 /* Set */
104#define ASN1_NUMSTR 18 /* Numerical String */
105#define ASN1_PRNSTR 19 /* Printable String */
106#define ASN1_TEXSTR 20 /* Teletext String */
107#define ASN1_VIDSTR 21 /* Video String */
108#define ASN1_IA5STR 22 /* IA5 String */
109#define ASN1_UNITIM 23 /* Universal Time */
110#define ASN1_GENTIM 24 /* General Time */
111#define ASN1_GRASTR 25 /* Graphical String */
112#define ASN1_VISSTR 26 /* Visible String */
113#define ASN1_GENSTR 27 /* General String */
114
115/* Primitive / Constructed methods*/
116#define ASN1_PRI 0 /* Primitive */
117#define ASN1_CON 1 /* Constructed */
118
119/*
120 * Error codes.
121 */
122#define ASN1_ERR_NOERROR 0
123#define ASN1_ERR_DEC_EMPTY 2
124#define ASN1_ERR_DEC_EOC_MISMATCH 3
125#define ASN1_ERR_DEC_LENGTH_MISMATCH 4
126#define ASN1_ERR_DEC_BADVALUE 5
127
128/*
129 * ASN.1 context.
130 */
131struct asn1_ctx
132{
133 int error; /* Error condition */
134 unsigned char *pointer; /* Octet just to be decoded */
135 unsigned char *begin; /* First octet */
136 unsigned char *end; /* Octet after last octet */
137};
138
139/*
140 * Octet string (not null terminated)
141 */
142struct asn1_octstr
143{
144 unsigned char *data;
145 unsigned int len;
146};
147
148static void asn1_open(struct asn1_ctx *ctx,
e905a9ed
YH		 149 unsigned char *buf,
150 unsigned int len)
807467c2
PM		 151{
152 ctx->begin = buf;
153 ctx->end = buf + len;
154 ctx->pointer = buf;
155 ctx->error = ASN1_ERR_NOERROR;
156}
157
158static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
159{
160 if (ctx->pointer >= ctx->end) {
161 ctx->error = ASN1_ERR_DEC_EMPTY;
162 return 0;
163 }
164 *ch = *(ctx->pointer)++;
165 return 1;
166}
167
168static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
169{
170 unsigned char ch;
171
172 *tag = 0;
173
174 do
175 {
176 if (!asn1_octet_decode(ctx, &ch))
177 return 0;
178 *tag <<= 7;
179 *tag |= ch & 0x7F;
180 } while ((ch & 0x80) == 0x80);
181 return 1;
182}
183
184static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
e905a9ed
YH		 185 unsigned int *cls,
186 unsigned int *con,
187 unsigned int *tag)
807467c2
PM		 188{
189 unsigned char ch;
190
191 if (!asn1_octet_decode(ctx, &ch))
192 return 0;
193
194 *cls = (ch & 0xC0) >> 6;
195 *con = (ch & 0x20) >> 5;
196 *tag = (ch & 0x1F);
197
198 if (*tag == 0x1F) {
199 if (!asn1_tag_decode(ctx, tag))
200 return 0;
201 }
202 return 1;
203}
204
205static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
e905a9ed
YH		 206 unsigned int *def,
207 unsigned int *len)
807467c2
PM		 208{
209 unsigned char ch, cnt;
210
211 if (!asn1_octet_decode(ctx, &ch))
212 return 0;
213
214 if (ch == 0x80)
215 *def = 0;
216 else {
217 *def = 1;
218
219 if (ch < 0x80)
220 *len = ch;
221 else {
222 cnt = (unsigned char) (ch & 0x7F);
223 *len = 0;
224
225 while (cnt > 0) {
226 if (!asn1_octet_decode(ctx, &ch))
227 return 0;
228 *len <<= 8;
229 *len |= ch;
230 cnt--;
231 }
232 }
233 }
234 return 1;
235}
236
237static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
e905a9ed
YH		 238 unsigned char **eoc,
239 unsigned int *cls,
240 unsigned int *con,
241 unsigned int *tag)
807467c2
PM		 242{
243 unsigned int def, len;
244
245 if (!asn1_id_decode(ctx, cls, con, tag))
246 return 0;
247
248 def = len = 0;
249 if (!asn1_length_decode(ctx, &def, &len))
250 return 0;
251
252 if (def)
253 *eoc = ctx->pointer + len;
254 else
255 *eoc = NULL;
256 return 1;
257}
258
259static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
260{
261 unsigned char ch;
262
06aa1072 263 if (eoc == NULL) {
807467c2
PM		 264 if (!asn1_octet_decode(ctx, &ch))
265 return 0;
266
267 if (ch != 0x00) {
268 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
269 return 0;
270 }
271
272 if (!asn1_octet_decode(ctx, &ch))
273 return 0;
274
275 if (ch != 0x00) {
276 ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
277 return 0;
278 }
279 return 1;
280 } else {
281 if (ctx->pointer != eoc) {
282 ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
283 return 0;
284 }
285 return 1;
286 }
287}
288
289static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
290{
291 ctx->pointer = eoc;
292 return 1;
293}
294
295static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
e905a9ed
YH		 296 unsigned char *eoc,
297 long *integer)
807467c2
PM		 298{
299 unsigned char ch;
300 unsigned int len;
301
302 if (!asn1_octet_decode(ctx, &ch))
303 return 0;
304
305 *integer = (signed char) ch;
306 len = 1;
307
308 while (ctx->pointer < eoc) {
309 if (++len > sizeof (long)) {
310 ctx->error = ASN1_ERR_DEC_BADVALUE;
311 return 0;
312 }
313
314 if (!asn1_octet_decode(ctx, &ch))
315 return 0;
316
317 *integer <<= 8;
318 *integer |= ch;
319 }
320 return 1;
321}
322
323static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
e905a9ed
YH		 324 unsigned char *eoc,
325 unsigned int *integer)
807467c2
PM		 326{
327 unsigned char ch;
328 unsigned int len;
329
330 if (!asn1_octet_decode(ctx, &ch))
331 return 0;
332
333 *integer = ch;
334 if (ch == 0) len = 0;
335 else len = 1;
336
337 while (ctx->pointer < eoc) {
338 if (++len > sizeof (unsigned int)) {
339 ctx->error = ASN1_ERR_DEC_BADVALUE;
340 return 0;
341 }
342
343 if (!asn1_octet_decode(ctx, &ch))
344 return 0;
345
346 *integer <<= 8;
347 *integer |= ch;
348 }
349 return 1;
350}
351
352static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
e905a9ed
YH		 353 unsigned char *eoc,
354 unsigned long *integer)
807467c2
PM		 355{
356 unsigned char ch;
357 unsigned int len;
358
359 if (!asn1_octet_decode(ctx, &ch))
360 return 0;
361
362 *integer = ch;
363 if (ch == 0) len = 0;
364 else len = 1;
365
366 while (ctx->pointer < eoc) {
367 if (++len > sizeof (unsigned long)) {
368 ctx->error = ASN1_ERR_DEC_BADVALUE;
369 return 0;
370 }
371
372 if (!asn1_octet_decode(ctx, &ch))
373 return 0;
374
375 *integer <<= 8;
376 *integer |= ch;
377 }
378 return 1;
379}
380
381static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
e905a9ed
YH		 382 unsigned char *eoc,
383 unsigned char **octets,
384 unsigned int *len)
807467c2
PM		 385{
386 unsigned char *ptr;
387
388 *len = 0;
389
390 *octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
391 if (*octets == NULL) {
392 if (net_ratelimit())
393 printk("OOM in bsalg (%d)\n", __LINE__);
394 return 0;
395 }
396
397 ptr = *octets;
398 while (ctx->pointer < eoc) {
399 if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
400 kfree(*octets);
401 *octets = NULL;
402 return 0;
403 }
404 (*len)++;
405 }
406 return 1;
407}
408
409static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
e905a9ed 410 unsigned long *subid)
807467c2
PM		 411{
412 unsigned char ch;
413
414 *subid = 0;
415
416 do {
417 if (!asn1_octet_decode(ctx, &ch))
418 return 0;
419
420 *subid <<= 7;
421 *subid |= ch & 0x7F;
422 } while ((ch & 0x80) == 0x80);
423 return 1;
424}
425
426static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
e905a9ed
YH		 427 unsigned char *eoc,
428 unsigned long **oid,
429 unsigned int *len)
807467c2
PM		 430{
431 unsigned long subid;
432 unsigned int size;
433 unsigned long *optr;
434
435 size = eoc - ctx->pointer + 1;
436 *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
437 if (*oid == NULL) {
438 if (net_ratelimit())
439 printk("OOM in bsalg (%d)\n", __LINE__);
440 return 0;
441 }
442
443 optr = *oid;
444
445 if (!asn1_subid_decode(ctx, &subid)) {
446 kfree(*oid);
447 *oid = NULL;
448 return 0;
449 }
450
451 if (subid < 40) {
452 optr [0] = 0;
453 optr [1] = subid;
454 } else if (subid < 80) {
455 optr [0] = 1;
456 optr [1] = subid - 40;
457 } else {
458 optr [0] = 2;
459 optr [1] = subid - 80;
460 }
461
462 *len = 2;
463 optr += 2;
464
465 while (ctx->pointer < eoc) {
466 if (++(*len) > size) {
467 ctx->error = ASN1_ERR_DEC_BADVALUE;
468 kfree(*oid);
469 *oid = NULL;
470 return 0;
471 }
472
473 if (!asn1_subid_decode(ctx, optr++)) {
474 kfree(*oid);
475 *oid = NULL;
476 return 0;
477 }
478 }
479 return 1;
480}
481
482/*****************************************************************************
483 *
484 * SNMP decoding routines (gxsnmp author Dirk Wisse)
485 *
486 *****************************************************************************/
487
488/* SNMP Versions */
489#define SNMP_V1 0
490#define SNMP_V2C 1
491#define SNMP_V2 2
492#define SNMP_V3 3
493
494/* Default Sizes */
495#define SNMP_SIZE_COMM 256
496#define SNMP_SIZE_OBJECTID 128
497#define SNMP_SIZE_BUFCHR 256
498#define SNMP_SIZE_BUFINT 128
499#define SNMP_SIZE_SMALLOBJECTID 16
500
501/* Requests */
502#define SNMP_PDU_GET 0
503#define SNMP_PDU_NEXT 1
504#define SNMP_PDU_RESPONSE 2
505#define SNMP_PDU_SET 3
506#define SNMP_PDU_TRAP1 4
507#define SNMP_PDU_BULK 5
508#define SNMP_PDU_INFORM 6
509#define SNMP_PDU_TRAP2 7
510
511/* Errors */
512#define SNMP_NOERROR 0
513#define SNMP_TOOBIG 1
514#define SNMP_NOSUCHNAME 2
515#define SNMP_BADVALUE 3
516#define SNMP_READONLY 4
517#define SNMP_GENERROR 5
518#define SNMP_NOACCESS 6
519#define SNMP_WRONGTYPE 7
520#define SNMP_WRONGLENGTH 8
521#define SNMP_WRONGENCODING 9
522#define SNMP_WRONGVALUE 10
523#define SNMP_NOCREATION 11
524#define SNMP_INCONSISTENTVALUE 12
525#define SNMP_RESOURCEUNAVAILABLE 13
526#define SNMP_COMMITFAILED 14
527#define SNMP_UNDOFAILED 15
528#define SNMP_AUTHORIZATIONERROR 16
529#define SNMP_NOTWRITABLE 17
530#define SNMP_INCONSISTENTNAME 18
531
532/* General SNMP V1 Traps */
533#define SNMP_TRAP_COLDSTART 0
534#define SNMP_TRAP_WARMSTART 1
535#define SNMP_TRAP_LINKDOWN 2
536#define SNMP_TRAP_LINKUP 3
537#define SNMP_TRAP_AUTFAILURE 4
538#define SNMP_TRAP_EQPNEIGHBORLOSS 5
539#define SNMP_TRAP_ENTSPECIFIC 6
540
541/* SNMPv1 Types */
542#define SNMP_NULL 0
543#define SNMP_INTEGER 1 /* l */
544#define SNMP_OCTETSTR 2 /* c */
545#define SNMP_DISPLAYSTR 2 /* c */
546#define SNMP_OBJECTID 3 /* ul */
547#define SNMP_IPADDR 4 /* uc */
548#define SNMP_COUNTER 5 /* ul */
549#define SNMP_GAUGE 6 /* ul */
550#define SNMP_TIMETICKS 7 /* ul */
551#define SNMP_OPAQUE 8 /* c */
552
553/* Additional SNMPv2 Types */
554#define SNMP_UINTEGER 5 /* ul */
555#define SNMP_BITSTR 9 /* uc */
556#define SNMP_NSAP 10 /* uc */
557#define SNMP_COUNTER64 11 /* ul */
558#define SNMP_NOSUCHOBJECT 12
559#define SNMP_NOSUCHINSTANCE 13
560#define SNMP_ENDOFMIBVIEW 14
561
562union snmp_syntax
563{
564 unsigned char uc[0]; /* 8 bit unsigned */
565 char c[0]; /* 8 bit signed */
566 unsigned long ul[0]; /* 32 bit unsigned */
567 long l[0]; /* 32 bit signed */
568};
569
570struct snmp_object
571{
572 unsigned long *id;
573 unsigned int id_len;
574 unsigned short type;
575 unsigned int syntax_len;
576 union snmp_syntax syntax;
577};
578
579struct snmp_request
580{
581 unsigned long id;
582 unsigned int error_status;
583 unsigned int error_index;
584};
585
586struct snmp_v1_trap
587{
588 unsigned long *id;
589 unsigned int id_len;
590 unsigned long ip_address; /* pointer */
591 unsigned int general;
592 unsigned int specific;
593 unsigned long time;
594};
595
596/* SNMP types */
597#define SNMP_IPA 0
598#define SNMP_CNT 1
599#define SNMP_GGE 2
600#define SNMP_TIT 3
601#define SNMP_OPQ 4
602#define SNMP_C64 6
603
604/* SNMP errors */
605#define SERR_NSO 0
606#define SERR_NSI 1
607#define SERR_EOM 2
608
609static inline void mangle_address(unsigned char *begin,
e905a9ed
YH		 610 unsigned char *addr,
611 const struct oct1_map *map,
612 __sum16 *check);
807467c2
PM		 613struct snmp_cnv
614{
615 unsigned int class;
616 unsigned int tag;
617 int syntax;
618};
619
620static struct snmp_cnv snmp_conv [] =
621{
622 {ASN1_UNI, ASN1_NUL, SNMP_NULL},
623 {ASN1_UNI, ASN1_INT, SNMP_INTEGER},
624 {ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
625 {ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
626 {ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
627 {ASN1_APL, SNMP_IPA, SNMP_IPADDR},
628 {ASN1_APL, SNMP_CNT, SNMP_COUNTER}, /* Counter32 */
629 {ASN1_APL, SNMP_GGE, SNMP_GAUGE}, /* Gauge32 == Unsigned32 */
630 {ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
631 {ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
632
633 /* SNMPv2 data types and errors */
634 {ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
635 {ASN1_APL, SNMP_C64, SNMP_COUNTER64},
636 {ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
637 {ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
638 {ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
639 {0, 0, -1}
640};
641
642static unsigned char snmp_tag_cls2syntax(unsigned int tag,
e905a9ed
YH		 643 unsigned int cls,
644 unsigned short *syntax)
807467c2
PM		 645{
646 struct snmp_cnv *cnv;
647
648 cnv = snmp_conv;
649
650 while (cnv->syntax != -1) {
651 if (cnv->tag == tag && cnv->class == cls) {
652 *syntax = cnv->syntax;
653 return 1;
654 }
655 cnv++;
656 }
657 return 0;
658}
659
660static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
e905a9ed 661 struct snmp_object **obj)
807467c2
PM		 662{
663 unsigned int cls, con, tag, len, idlen;
664 unsigned short type;
665 unsigned char *eoc, *end, *p;
666 unsigned long *lp, *id;
667 unsigned long ul;
668 long l;
669
670 *obj = NULL;
671 id = NULL;
672
673 if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
674 return 0;
675
676 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
677 return 0;
678
679 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
680 return 0;
681
682 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
683 return 0;
684
685 if (!asn1_oid_decode(ctx, end, &id, &idlen))
686 return 0;
687
688 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
689 kfree(id);
690 return 0;
691 }
692
693 if (con != ASN1_PRI) {
694 kfree(id);
695 return 0;
696 }
697
698 type = 0;
699 if (!snmp_tag_cls2syntax(tag, cls, &type)) {
700 kfree(id);
701 return 0;
702 }
703
704 l = 0;
705 switch (type) {
706 case SNMP_INTEGER:
707 len = sizeof(long);
708 if (!asn1_long_decode(ctx, end, &l)) {
709 kfree(id);
710 return 0;
711 }
712 *obj = kmalloc(sizeof(struct snmp_object) + len,
e905a9ed 713 GFP_ATOMIC);
807467c2
PM		 714 if (*obj == NULL) {
715 kfree(id);
716 if (net_ratelimit())
717 printk("OOM in bsalg (%d)\n", __LINE__);
718 return 0;
719 }
720 (*obj)->syntax.l[0] = l;
721 break;
722 case SNMP_OCTETSTR:
723 case SNMP_OPAQUE:
724 if (!asn1_octets_decode(ctx, end, &p, &len)) {
725 kfree(id);
726 return 0;
727 }
728 *obj = kmalloc(sizeof(struct snmp_object) + len,
e905a9ed 729 GFP_ATOMIC);
807467c2
PM		 730 if (*obj == NULL) {
731 kfree(id);
732 if (net_ratelimit())
733 printk("OOM in bsalg (%d)\n", __LINE__);
734 return 0;
735 }
736 memcpy((*obj)->syntax.c, p, len);
737 kfree(p);
738 break;
739 case SNMP_NULL:
740 case SNMP_NOSUCHOBJECT:
741 case SNMP_NOSUCHINSTANCE:
742 case SNMP_ENDOFMIBVIEW:
743 len = 0;
744 *obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
745 if (*obj == NULL) {
746 kfree(id);
747 if (net_ratelimit())
748 printk("OOM in bsalg (%d)\n", __LINE__);
749 return 0;
750 }
751 if (!asn1_null_decode(ctx, end)) {
752 kfree(id);
753 kfree(*obj);
754 *obj = NULL;
755 return 0;
756 }
757 break;
758 case SNMP_OBJECTID:
759 if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
760 kfree(id);
761 return 0;
762 }
763 len *= sizeof(unsigned long);
764 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
765 if (*obj == NULL) {
766 kfree(lp);
767 kfree(id);
768 if (net_ratelimit())
769 printk("OOM in bsalg (%d)\n", __LINE__);
770 return 0;
771 }
772 memcpy((*obj)->syntax.ul, lp, len);
773 kfree(lp);
774 break;
775 case SNMP_IPADDR:
776 if (!asn1_octets_decode(ctx, end, &p, &len)) {
777 kfree(id);
778 return 0;
779 }
780 if (len != 4) {
781 kfree(p);
782 kfree(id);
783 return 0;
784 }
785 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
786 if (*obj == NULL) {
787 kfree(p);
788 kfree(id);
789 if (net_ratelimit())
790 printk("OOM in bsalg (%d)\n", __LINE__);
791 return 0;
792 }
793 memcpy((*obj)->syntax.uc, p, len);
794 kfree(p);
795 break;
796 case SNMP_COUNTER:
797 case SNMP_GAUGE:
798 case SNMP_TIMETICKS:
799 len = sizeof(unsigned long);
800 if (!asn1_ulong_decode(ctx, end, &ul)) {
801 kfree(id);
802 return 0;
803 }
804 *obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
805 if (*obj == NULL) {
806 kfree(id);
807 if (net_ratelimit())
808 printk("OOM in bsalg (%d)\n", __LINE__);
809 return 0;
810 }
811 (*obj)->syntax.ul[0] = ul;
812 break;
813 default:
814 kfree(id);
815 return 0;
816 }
817
818 (*obj)->syntax_len = len;
819 (*obj)->type = type;
820 (*obj)->id = id;
821 (*obj)->id_len = idlen;
822
823 if (!asn1_eoc_decode(ctx, eoc)) {
824 kfree(id);
825 kfree(*obj);
826 *obj = NULL;
827 return 0;
828 }
829 return 1;
830}
831
832static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
e905a9ed 833 struct snmp_request *request)
807467c2
PM		 834{
835 unsigned int cls, con, tag;
836 unsigned char *end;
837
838 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
839 return 0;
840
841 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
842 return 0;
843
844 if (!asn1_ulong_decode(ctx, end, &request->id))
845 return 0;
846
847 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
848 return 0;
849
850 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
851 return 0;
852
853 if (!asn1_uint_decode(ctx, end, &request->error_status))
854 return 0;
855
856 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
857 return 0;
858
859 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
860 return 0;
861
862 if (!asn1_uint_decode(ctx, end, &request->error_index))
863 return 0;
864
865 return 1;
866}
867
868/*
869 * Fast checksum update for possibly oddly-aligned UDP byte, from the
870 * code example in the draft.
871 */
872static void fast_csum(__sum16 *csum,
e905a9ed
YH		 873 const unsigned char *optr,
874 const unsigned char *nptr,
875 int offset)
807467c2
PM		 876{
877 unsigned char s[4];
878
879 if (offset & 1) {
880 s[0] = s[2] = 0;
881 s[1] = ~*optr;
882 s[3] = *nptr;
883 } else {
884 s[1] = s[3] = 0;
885 s[0] = ~*optr;
886 s[2] = *nptr;
887 }
888
889 *csum = csum_fold(csum_partial(s, 4, ~csum_unfold(*csum)));
890}
891
892/*
893 * Mangle IP address.
894 * - begin points to the start of the snmp messgae
895 * - addr points to the start of the address
896 */
897static inline void mangle_address(unsigned char *begin,
e905a9ed
YH		 898 unsigned char *addr,
899 const struct oct1_map *map,
900 __sum16 *check)
807467c2
PM		 901{
902 if (map->from == NOCT1(addr)) {
903 u_int32_t old;
904
905 if (debug)
906 memcpy(&old, (unsigned char *)addr, sizeof(old));
907
908 *addr = map->to;
909
910 /* Update UDP checksum if being used */
911 if (*check) {
912 fast_csum(check,
e905a9ed 913 &map->from, &map->to, addr - begin);
807467c2
PM		 914
915 }
916
917 if (debug)
918 printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
919 "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
920 }
921}
922
923static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
e905a9ed
YH		 924 struct snmp_v1_trap *trap,
925 const struct oct1_map *map,
926 __sum16 *check)
807467c2
PM		 927{
928 unsigned int cls, con, tag, len;
929 unsigned char *end;
930
931 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
932 return 0;
933
934 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
935 return 0;
936
937 if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
938 return 0;
939
940 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
941 goto err_id_free;
942
943 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
944 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
945 goto err_id_free;
946
947 if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
948 goto err_id_free;
949
950 /* IPv4 only */
951 if (len != 4)
952 goto err_addr_free;
953
954 mangle_address(ctx->begin, ctx->pointer - 4, map, check);
955
956 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
957 goto err_addr_free;
958
959 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
960 goto err_addr_free;
961
962 if (!asn1_uint_decode(ctx, end, &trap->general))
963 goto err_addr_free;
964
965 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
966 goto err_addr_free;
967
968 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
969 goto err_addr_free;
970
971 if (!asn1_uint_decode(ctx, end, &trap->specific))
972 goto err_addr_free;
973
974 if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
975 goto err_addr_free;
976
977 if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
978 (cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
979 goto err_addr_free;
980
981 if (!asn1_ulong_decode(ctx, end, &trap->time))
982 goto err_addr_free;
983
984 return 1;
985
986err_addr_free:
987 kfree((unsigned long *)trap->ip_address);
988
989err_id_free:
990 kfree(trap->id);
991
992 return 0;
993}
994
995/*****************************************************************************
996 *
997 * Misc. routines
998 *
999 *****************************************************************************/
1000
1001static void hex_dump(unsigned char *buf, size_t len)
1002{
1003 size_t i;
1004
1005 for (i = 0; i < len; i++) {
1006 if (i && !(i % 16))
1007 printk("\n");
1008 printk("%02x ", *(buf + i));
1009 }
1010 printk("\n");
1011}
1012
1013/*
1014 * Parse and mangle SNMP message according to mapping.
1015 * (And this is the fucking 'basic' method).
1016 */
1017static int snmp_parse_mangle(unsigned char *msg,
e905a9ed
YH		 1018 u_int16_t len,
1019 const struct oct1_map *map,
1020 __sum16 *check)
807467c2
PM		 1021{
1022 unsigned char *eoc, *end;
1023 unsigned int cls, con, tag, vers, pdutype;
1024 struct asn1_ctx ctx;
1025 struct asn1_octstr comm;
1026 struct snmp_object **obj;
1027
1028 if (debug > 1)
1029 hex_dump(msg, len);
1030
1031 asn1_open(&ctx, msg, len);
1032
1033 /*
1034 * Start of SNMP message.
1035 */
1036 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1037 return 0;
1038 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1039 return 0;
1040
1041 /*
1042 * Version 1 or 2 handled.
1043 */
1044 if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
1045 return 0;
1046 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
1047 return 0;
1048 if (!asn1_uint_decode (&ctx, end, &vers))
1049 return 0;
1050 if (debug > 1)
1051 printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
1052 if (vers > 1)
1053 return 1;
1054
1055 /*
1056 * Community.
1057 */
1058 if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
1059 return 0;
1060 if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
1061 return 0;
1062 if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
1063 return 0;
1064 if (debug > 1) {
1065 unsigned int i;
1066
1067 printk(KERN_DEBUG "bsalg: community: ");
1068 for (i = 0; i < comm.len; i++)
1069 printk("%c", comm.data[i]);
1070 printk("\n");
1071 }
1072 kfree(comm.data);
1073
1074 /*
1075 * PDU type
1076 */
1077 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
1078 return 0;
1079 if (cls != ASN1_CTX || con != ASN1_CON)
1080 return 0;
1081 if (debug > 1) {
1082 unsigned char *pdus[] = {
1083 [SNMP_PDU_GET] = "get",
1084 [SNMP_PDU_NEXT] = "get-next",
1085 [SNMP_PDU_RESPONSE] = "response",
1086 [SNMP_PDU_SET] = "set",
1087 [SNMP_PDU_TRAP1] = "trapv1",
1088 [SNMP_PDU_BULK] = "bulk",
1089 [SNMP_PDU_INFORM] = "inform",
1090 [SNMP_PDU_TRAP2] = "trapv2"
1091 };
1092
1093 if (pdutype > SNMP_PDU_TRAP2)
1094 printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
1095 else
1096 printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
1097 }
1098 if (pdutype != SNMP_PDU_RESPONSE &&
1099 pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
1100 return 1;
1101
1102 /*
1103 * Request header or v1 trap
1104 */
1105 if (pdutype == SNMP_PDU_TRAP1) {
1106 struct snmp_v1_trap trap;
1107 unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
1108
1109 if (ret) {
1110 kfree(trap.id);
1111 kfree((unsigned long *)trap.ip_address);
1112 } else
1113 return ret;
1114
1115 } else {
1116 struct snmp_request req;
1117
1118 if (!snmp_request_decode(&ctx, &req))
1119 return 0;
1120
1121 if (debug > 1)
1122 printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
1123 "error_index=%u\n", req.id, req.error_status,
1124 req.error_index);
1125 }
1126
1127 /*
1128 * Loop through objects, look for IP addresses to mangle.
1129 */
1130 if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
1131 return 0;
1132
1133 if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
1134 return 0;
1135
1136 obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
1137 if (obj == NULL) {
1138 if (net_ratelimit())
1139 printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
1140 return 0;
1141 }
1142
1143 while (!asn1_eoc_decode(&ctx, eoc)) {
1144 unsigned int i;
1145
1146 if (!snmp_object_decode(&ctx, obj)) {
1147 if (*obj) {
1148 kfree((*obj)->id);
1149 kfree(*obj);
1150 }
1151 kfree(obj);
1152 return 0;
1153 }
1154
1155 if (debug > 1) {
1156 printk(KERN_DEBUG "bsalg: object: ");
1157 for (i = 0; i < (*obj)->id_len; i++) {
1158 if (i > 0)
1159 printk(".");
1160 printk("%lu", (*obj)->id[i]);
1161 }
1162 printk(": type=%u\n", (*obj)->type);
1163
1164 }
1165
1166 if ((*obj)->type == SNMP_IPADDR)
1167 mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
1168
1169 kfree((*obj)->id);
1170 kfree(*obj);
1171 }
1172 kfree(obj);
1173
1174 if (!asn1_eoc_decode(&ctx, eoc))
1175 return 0;
1176
1177 return 1;
1178}
1179
1180/*****************************************************************************
1181 *
1182 * NAT routines.
1183 *
1184 *****************************************************************************/
1185
1186/*
1187 * SNMP translation routine.
1188 */
1189static int snmp_translate(struct nf_conn *ct,
e905a9ed 1190 enum ip_conntrack_info ctinfo,
3db05fea 1191 struct sk_buff *skb)
807467c2 1192{
3db05fea 1193 struct iphdr *iph = ip_hdr(skb);
807467c2
PM		 1194 struct udphdr *udph = (struct udphdr *)((__be32 *)iph + iph->ihl);
1195 u_int16_t udplen = ntohs(udph->len);
1196 u_int16_t paylen = udplen - sizeof(struct udphdr);
1197 int dir = CTINFO2DIR(ctinfo);
1198 struct oct1_map map;
1199
1200 /*
1201 * Determine mappping for application layer addresses based
1202 * on NAT manipulations for the packet.
1203 */
1204 if (dir == IP_CT_DIR_ORIGINAL) {
1205 /* SNAT traps */
1206 map.from = NOCT1(&ct->tuplehash[dir].tuple.src.u3.ip);
1207 map.to = NOCT1(&ct->tuplehash[!dir].tuple.dst.u3.ip);
1208 } else {
1209 /* DNAT replies */
1210 map.from = NOCT1(&ct->tuplehash[dir].tuple.src.u3.ip);
1211 map.to = NOCT1(&ct->tuplehash[!dir].tuple.dst.u3.ip);
1212 }
1213
1214 if (map.from == map.to)
1215 return NF_ACCEPT;
1216
1217 if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
e905a9ed 1218 paylen, &map, &udph->check)) {
807467c2
PM		 1219 if (net_ratelimit())
1220 printk(KERN_WARNING "bsalg: parser failed\n");
1221 return NF_DROP;
1222 }
1223 return NF_ACCEPT;
1224}
1225
1226/* We don't actually set up expectations, just adjust internal IP
1227 * addresses if this is being NATted */
3db05fea 1228static int help(struct sk_buff *skb, unsigned int protoff,
807467c2
PM		 1229 struct nf_conn *ct,
1230 enum ip_conntrack_info ctinfo)
1231{
1232 int dir = CTINFO2DIR(ctinfo);
1233 unsigned int ret;
3db05fea 1234 struct iphdr *iph = ip_hdr(skb);
807467c2
PM		 1235 struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
1236
1237 /* SNMP replies and originating SNMP traps get mangled */
1238 if (udph->source == htons(SNMP_PORT) && dir != IP_CT_DIR_REPLY)
1239 return NF_ACCEPT;
1240 if (udph->dest == htons(SNMP_TRAP_PORT) && dir != IP_CT_DIR_ORIGINAL)
1241 return NF_ACCEPT;
1242
1243 /* No NAT? */
1244 if (!(ct->status & IPS_NAT_MASK))
1245 return NF_ACCEPT;
1246
1247 /*
1248 * Make sure the packet length is ok. So far, we were only guaranteed
1249 * to have a valid length IP header plus 8 bytes, which means we have
1250 * enough room for a UDP header. Just verify the UDP length field so we
1251 * can mess around with the payload.
1252 */
3db05fea 1253 if (ntohs(udph->len) != skb->len - (iph->ihl << 2)) {
807467c2
PM		 1254 if (net_ratelimit())
1255 printk(KERN_WARNING "SNMP: dropping malformed packet "
1256 "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
1257 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
1258 return NF_DROP;
1259 }
1260
3db05fea 1261 if (!skb_make_writable(skb, skb->len))
807467c2
PM		 1262 return NF_DROP;
1263
1264 spin_lock_bh(&snmp_lock);
3db05fea 1265 ret = snmp_translate(ct, ctinfo, skb);
807467c2
PM		 1266 spin_unlock_bh(&snmp_lock);
1267 return ret;
1268}
1269
1270static struct nf_conntrack_helper snmp_helper __read_mostly = {
1271 .max_expected = 0,
1272 .timeout = 180,
1273 .me = THIS_MODULE,
1274 .help = help,
1275 .name = "snmp",
1276 .tuple.src.l3num = AF_INET,
1277 .tuple.src.u.udp.port = __constant_htons(SNMP_PORT),
1278 .tuple.dst.protonum = IPPROTO_UDP,
807467c2
PM		 1279};
1280
1281static struct nf_conntrack_helper snmp_trap_helper __read_mostly = {
1282 .max_expected = 0,
1283 .timeout = 180,
1284 .me = THIS_MODULE,
1285 .help = help,
1286 .name = "snmp_trap",
1287 .tuple.src.l3num = AF_INET,
1288 .tuple.src.u.udp.port = __constant_htons(SNMP_TRAP_PORT),
1289 .tuple.dst.protonum = IPPROTO_UDP,
807467c2
PM		 1290};
1291
1292/*****************************************************************************
1293 *
1294 * Module stuff.
1295 *
1296 *****************************************************************************/
1297
1298static int __init nf_nat_snmp_basic_init(void)
1299{
1300 int ret = 0;
1301
1302 ret = nf_conntrack_helper_register(&snmp_helper);
1303 if (ret < 0)
1304 return ret;
1305 ret = nf_conntrack_helper_register(&snmp_trap_helper);
1306 if (ret < 0) {
1307 nf_conntrack_helper_unregister(&snmp_helper);
1308 return ret;
1309 }
1310 return ret;
1311}
1312
1313static void __exit nf_nat_snmp_basic_fini(void)
1314{
1315 nf_conntrack_helper_unregister(&snmp_helper);
1316 nf_conntrack_helper_unregister(&snmp_trap_helper);
1317}
1318
1319module_init(nf_nat_snmp_basic_init);
1320module_exit(nf_nat_snmp_basic_fini);
1321
1322module_param(debug, int, 0600);
Linux kernel - Deliverables
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