1 /**
2  * @file
3  * SNMPv1 traps implementation.
4  */
5 
6 /*
7  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
8  * All rights reserved.
9  *
10  * Redistribution and use in source and binary forms, with or without modification,
11  * are permitted provided that the following conditions are met:
12  *
13  * 1. Redistributions of source code must retain the above copyright notice,
14  *    this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright notice,
16  *    this list of conditions and the following disclaimer in the documentation
17  *    and/or other materials provided with the distribution.
18  * 3. The name of the author may not be used to endorse or promote products
19  *    derived from this software without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
22  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
23  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
24  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
25  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
26  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
29  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
30  * OF SUCH DAMAGE.
31  *
32  * This file is part of the lwIP TCP/IP stack.
33  *
34  * Author: Martin Hentschel
35  *         Christiaan Simons <christiaan.simons@axon.tv>
36  *
37  */
38 
39 #include "lwip/apps/snmp_opts.h"
40 
41 #if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
42 
43 #include <string.h>
44 
45 #include "lwip/snmp.h"
46 #include "lwip/sys.h"
47 #include "lwip/apps/snmp.h"
48 #include "lwip/apps/snmp_core.h"
49 #include "snmp_msg.h"
50 #include "snmp_asn1.h"
51 #include "snmp_core_priv.h"
52 
53 struct snmp_msg_trap
54 {
55   /* source enterprise ID (sysObjectID) */
56   const struct snmp_obj_id *enterprise;
57   /* source IP address, raw network order format */
58   ip_addr_t sip;
59   /* generic trap code */
60   u32_t gen_trap;
61   /* specific trap code */
62   u32_t spc_trap;
63   /* timestamp */
64   u32_t ts;
65   /* snmp_version */
66   u32_t snmp_version;
67 
68   /* output trap lengths used in ASN encoding */
69   /* encoding pdu length */
70   u16_t pdulen;
71   /* encoding community length */
72   u16_t comlen;
73   /* encoding sequence length */
74   u16_t seqlen;
75   /* encoding varbinds sequence length */
76   u16_t vbseqlen;
77 };
78 
79 static u16_t snmp_trap_varbind_sum(struct snmp_msg_trap *trap, struct snmp_varbind *varbinds);
80 static u16_t snmp_trap_header_sum(struct snmp_msg_trap *trap, u16_t vb_len);
81 static void snmp_trap_header_enc(struct snmp_msg_trap *trap, struct snmp_pbuf_stream *pbuf_stream);
82 static void snmp_trap_varbind_enc(struct snmp_msg_trap *trap, struct snmp_pbuf_stream *pbuf_stream, struct snmp_varbind *varbinds);
83 
84 /** Agent community string for sending traps */
85 extern const char *snmp_community_trap;
86 
87 void* snmp_traps_handle;
88 
89 struct snmp_trap_dst
90 {
91   /* destination IP address in network order */
92   ip_addr_t dip;
93   /* set to 0 when disabled, >0 when enabled */
94   u8_t enable;
95 };
96 static struct snmp_trap_dst trap_dst[SNMP_TRAP_DESTINATIONS];
97 
98 static u8_t snmp_auth_traps_enabled = 0;
99 
100 /**
101  * @ingroup snmp_traps
102  * Sets enable switch for this trap destination.
103  * @param dst_idx index in 0 .. SNMP_TRAP_DESTINATIONS-1
104  * @param enable switch if 0 destination is disabled >0 enabled.
105  */
106 void
107 snmp_trap_dst_enable(u8_t dst_idx, u8_t enable)
108 {
109   if (dst_idx < SNMP_TRAP_DESTINATIONS) {
110     trap_dst[dst_idx].enable = enable;
111   }
112 }
113 
114 /**
115  * @ingroup snmp_traps
116  * Sets IPv4 address for this trap destination.
117  * @param dst_idx index in 0 .. SNMP_TRAP_DESTINATIONS-1
118  * @param dst IPv4 address in host order.
119  */
120 void
121 snmp_trap_dst_ip_set(u8_t dst_idx, const ip_addr_t *dst)
122 {
123   if (dst_idx < SNMP_TRAP_DESTINATIONS) {
124     ip_addr_set(&trap_dst[dst_idx].dip, dst);
125   }
126 }
127 
128 /**
129  * @ingroup snmp_traps
130  * Enable/disable authentication traps
131  */
132 void
133 snmp_set_auth_traps_enabled(u8_t enable)
134 {
135   snmp_auth_traps_enabled = enable;
136 }
137 
138 /**
139  * @ingroup snmp_traps
140  * Get authentication traps enabled state
141  */
142 u8_t
143 snmp_get_auth_traps_enabled(void)
144 {
145   return snmp_auth_traps_enabled;
146 }
147 
148 
149 /**
150  * @ingroup snmp_traps
151  * Sends a generic or enterprise specific trap message.
152  *
153  * @param eoid points to enterprise object identifier
154  * @param generic_trap is the trap code
155  * @param specific_trap used for enterprise traps when generic_trap == 6
156  * @param varbinds linked list of varbinds to be sent
157  * @return ERR_OK when success, ERR_MEM if we're out of memory
158  *
159  * @note the use of the enterprise identifier field
160  * is per RFC1215.
161  * Use .iso.org.dod.internet.mgmt.mib-2.snmp for generic traps
162  * and .iso.org.dod.internet.private.enterprises.yourenterprise
163  * (sysObjectID) for specific traps.
164  */
165 err_t
166 snmp_send_trap(const struct snmp_obj_id* eoid, s32_t generic_trap, s32_t specific_trap, struct snmp_varbind *varbinds)
167 {
168   struct snmp_msg_trap trap_msg;
169   struct snmp_trap_dst *td;
170   struct pbuf *p;
171   u16_t i, tot_len;
172   err_t err = ERR_OK;
173 
174   trap_msg.snmp_version = 0;
175 
176   for (i = 0, td = &trap_dst[0]; i < SNMP_TRAP_DESTINATIONS; i++, td++) {
177     if ((td->enable != 0) && !ip_addr_isany(&td->dip)) {
178       /* lookup current source address for this dst */
179       if (snmp_get_local_ip_for_dst(snmp_traps_handle, &td->dip, &trap_msg.sip)) {
180         if (eoid == NULL) {
181           trap_msg.enterprise = snmp_get_device_enterprise_oid();
182         } else {
183           trap_msg.enterprise = eoid;
184         }
185 
186         trap_msg.gen_trap = generic_trap;
187         if (generic_trap == SNMP_GENTRAP_ENTERPRISE_SPECIFIC) {
188           trap_msg.spc_trap = specific_trap;
189         } else {
190           trap_msg.spc_trap = 0;
191         }
192 
193         MIB2_COPY_SYSUPTIME_TO(&trap_msg.ts);
194 
195         /* pass 0, calculate length fields */
196         tot_len = snmp_trap_varbind_sum(&trap_msg, varbinds);
197         tot_len = snmp_trap_header_sum(&trap_msg, tot_len);
198 
199         /* allocate pbuf(s) */
200         p = pbuf_alloc(PBUF_TRANSPORT, tot_len, PBUF_RAM);
201         if (p != NULL) {
202           struct snmp_pbuf_stream pbuf_stream;
203           snmp_pbuf_stream_init(&pbuf_stream, p, 0, tot_len);
204 
205           /* pass 1, encode packet ino the pbuf(s) */
206           snmp_trap_header_enc(&trap_msg, &pbuf_stream);
207           snmp_trap_varbind_enc(&trap_msg, &pbuf_stream, varbinds);
208 
209           snmp_stats.outtraps++;
210           snmp_stats.outpkts++;
211 
212           /** send to the TRAP destination */
213           snmp_sendto(snmp_traps_handle, p, &td->dip, SNMP_TRAP_PORT);
214           pbuf_free(p);
215         } else {
216           err = ERR_MEM;
217         }
218       } else {
219         /* routing error */
220         err = ERR_RTE;
221       }
222     }
223   }
224   return err;
225 }
226 
227 /**
228  * @ingroup snmp_traps
229  * Send generic SNMP trap
230  */
231 err_t
232 snmp_send_trap_generic(s32_t generic_trap)
233 {
234   static const struct snmp_obj_id oid = { 7, { 1, 3, 6, 1, 2, 1, 11 } };
235   return snmp_send_trap(&oid, generic_trap, 0, NULL);
236 }
237 
238 /**
239  * @ingroup snmp_traps
240  * Send specific SNMP trap with variable bindings
241  */
242 err_t
243 snmp_send_trap_specific(s32_t specific_trap, struct snmp_varbind *varbinds)
244 {
245   return snmp_send_trap(NULL, SNMP_GENTRAP_ENTERPRISE_SPECIFIC, specific_trap, varbinds);
246 }
247 
248 /**
249  * @ingroup snmp_traps
250  * Send coldstart trap
251  */
252 void
253 snmp_coldstart_trap(void)
254 {
255   snmp_send_trap_generic(SNMP_GENTRAP_COLDSTART);
256 }
257 
258 /**
259  * @ingroup snmp_traps
260  * Send authentication failure trap (used internally by agent)
261  */
262 void
263 snmp_authfail_trap(void)
264 {
265   if (snmp_auth_traps_enabled != 0) {
266     snmp_send_trap_generic(SNMP_GENTRAP_AUTH_FAILURE);
267   }
268 }
269 
270 static u16_t
271 snmp_trap_varbind_sum(struct snmp_msg_trap *trap, struct snmp_varbind *varbinds)
272 {
273   struct snmp_varbind *varbind;
274   u16_t tot_len;
275   u8_t tot_len_len;
276 
277   tot_len = 0;
278   varbind = varbinds;
279   while (varbind != NULL) {
280     struct snmp_varbind_len len;
281 
282     if (snmp_varbind_length(varbind, &len) == ERR_OK) {
283       tot_len += 1 + len.vb_len_len + len.vb_value_len;
284     }
285 
286     varbind = varbind->next;
287   }
288 
289   trap->vbseqlen = tot_len;
290   snmp_asn1_enc_length_cnt(trap->vbseqlen, &tot_len_len);
291   tot_len += 1 + tot_len_len;
292 
293   return tot_len;
294 }
295 
296 /**
297  * Sums trap header field lengths from tail to head and
298  * returns trap_header_lengths for second encoding pass.
299  *
300  * @param trap Trap message
301  * @param vb_len varbind-list length
302  * @return the required length for encoding the trap header
303  */
304 static u16_t
305 snmp_trap_header_sum(struct snmp_msg_trap *trap, u16_t vb_len)
306 {
307   u16_t tot_len;
308   u16_t len;
309   u8_t lenlen;
310 
311   tot_len = vb_len;
312 
313   snmp_asn1_enc_u32t_cnt(trap->ts, &len);
314   snmp_asn1_enc_length_cnt(len, &lenlen);
315   tot_len += 1 + len + lenlen;
316 
317   snmp_asn1_enc_s32t_cnt(trap->spc_trap, &len);
318   snmp_asn1_enc_length_cnt(len, &lenlen);
319   tot_len += 1 + len + lenlen;
320 
321   snmp_asn1_enc_s32t_cnt(trap->gen_trap, &len);
322   snmp_asn1_enc_length_cnt(len, &lenlen);
323   tot_len += 1 + len + lenlen;
324 
325   if (IP_IS_V6_VAL(trap->sip)) {
326 #if LWIP_IPV6
327     len = sizeof(ip_2_ip6(&trap->sip)->addr);
328 #endif
329   } else {
330 #if LWIP_IPV4
331     len = sizeof(ip_2_ip4(&trap->sip)->addr);
332 #endif
333   }
334   snmp_asn1_enc_length_cnt(len, &lenlen);
335   tot_len += 1 + len + lenlen;
336 
337   snmp_asn1_enc_oid_cnt(trap->enterprise->id, trap->enterprise->len, &len);
338   snmp_asn1_enc_length_cnt(len, &lenlen);
339   tot_len += 1 + len + lenlen;
340 
341   trap->pdulen = tot_len;
342   snmp_asn1_enc_length_cnt(trap->pdulen, &lenlen);
343   tot_len += 1 + lenlen;
344 
345   trap->comlen = (u16_t)LWIP_MIN(strlen(snmp_community_trap), 0xFFFF);
346   snmp_asn1_enc_length_cnt(trap->comlen, &lenlen);
347   tot_len += 1 + lenlen + trap->comlen;
348 
349   snmp_asn1_enc_s32t_cnt(trap->snmp_version, &len);
350   snmp_asn1_enc_length_cnt(len, &lenlen);
351   tot_len += 1 + len + lenlen;
352 
353   trap->seqlen = tot_len;
354   snmp_asn1_enc_length_cnt(trap->seqlen, &lenlen);
355   tot_len += 1 + lenlen;
356 
357   return tot_len;
358 }
359 
360 static void
361 snmp_trap_varbind_enc(struct snmp_msg_trap *trap, struct snmp_pbuf_stream *pbuf_stream, struct snmp_varbind *varbinds)
362 {
363   struct snmp_asn1_tlv tlv;
364   struct snmp_varbind *varbind;
365 
366   varbind = varbinds;
367 
368   SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_SEQUENCE, 0, trap->vbseqlen);
369   snmp_ans1_enc_tlv(pbuf_stream, &tlv);
370 
371   while (varbind != NULL) {
372     snmp_append_outbound_varbind(pbuf_stream, varbind);
373 
374     varbind = varbind->next;
375   }
376 }
377 
378 /**
379  * Encodes trap header from head to tail.
380  */
381 static void
382 snmp_trap_header_enc(struct snmp_msg_trap *trap, struct snmp_pbuf_stream *pbuf_stream)
383 {
384   struct snmp_asn1_tlv tlv;
385 
386   /* 'Message' sequence */
387   SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_SEQUENCE, 0, trap->seqlen);
388   snmp_ans1_enc_tlv(pbuf_stream, &tlv);
389 
390   /* version */
391   SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_INTEGER, 0, 0);
392   snmp_asn1_enc_s32t_cnt(trap->snmp_version, &tlv.value_len);
393   snmp_ans1_enc_tlv(pbuf_stream, &tlv);
394   snmp_asn1_enc_s32t(pbuf_stream, tlv.value_len, trap->snmp_version);
395 
396   /* community */
397   SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_OCTET_STRING, 0, trap->comlen);
398   snmp_ans1_enc_tlv(pbuf_stream, &tlv);
399   snmp_asn1_enc_raw(pbuf_stream,  (const u8_t *)snmp_community_trap, trap->comlen);
400 
401   /* 'PDU' sequence */
402   SNMP_ASN1_SET_TLV_PARAMS(tlv, (SNMP_ASN1_CLASS_CONTEXT | SNMP_ASN1_CONTENTTYPE_CONSTRUCTED | SNMP_ASN1_CONTEXT_PDU_TRAP), 0, trap->pdulen);
403   snmp_ans1_enc_tlv(pbuf_stream, &tlv);
404 
405   /* object ID */
406   SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_OBJECT_ID, 0, 0);
407   snmp_asn1_enc_oid_cnt(trap->enterprise->id, trap->enterprise->len, &tlv.value_len);
408   snmp_ans1_enc_tlv(pbuf_stream, &tlv);
409   snmp_asn1_enc_oid(pbuf_stream, trap->enterprise->id, trap->enterprise->len);
410 
411   /* IP addr */
412   if (IP_IS_V6_VAL(trap->sip)) {
413 #if LWIP_IPV6
414     SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_IPADDR, 0, sizeof(ip_2_ip6(&trap->sip)->addr));
415     snmp_ans1_enc_tlv(pbuf_stream, &tlv);
416     snmp_asn1_enc_raw(pbuf_stream, (const u8_t *)&ip_2_ip6(&trap->sip)->addr, sizeof(ip_2_ip6(&trap->sip)->addr));
417 #endif
418   } else {
419 #if LWIP_IPV4
420     SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_IPADDR, 0, sizeof(ip_2_ip4(&trap->sip)->addr));
421     snmp_ans1_enc_tlv(pbuf_stream, &tlv);
422     snmp_asn1_enc_raw(pbuf_stream, (const u8_t *)&ip_2_ip4(&trap->sip)->addr, sizeof(ip_2_ip4(&trap->sip)->addr));
423 #endif
424   }
425 
426   /* trap length */
427   SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_INTEGER, 0, 0);
428   snmp_asn1_enc_s32t_cnt(trap->gen_trap, &tlv.value_len);
429   snmp_ans1_enc_tlv(pbuf_stream, &tlv);
430   snmp_asn1_enc_s32t(pbuf_stream, tlv.value_len, trap->gen_trap);
431 
432   /* specific trap */
433   SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_INTEGER, 0, 0);
434   snmp_asn1_enc_s32t_cnt(trap->spc_trap, &tlv.value_len);
435   snmp_ans1_enc_tlv(pbuf_stream, &tlv);
436   snmp_asn1_enc_s32t(pbuf_stream, tlv.value_len, trap->spc_trap);
437 
438   /* timestamp */
439   SNMP_ASN1_SET_TLV_PARAMS(tlv, SNMP_ASN1_TYPE_TIMETICKS, 0, 0);
440   snmp_asn1_enc_s32t_cnt(trap->ts, &tlv.value_len);
441   snmp_ans1_enc_tlv(pbuf_stream, &tlv);
442   snmp_asn1_enc_s32t(pbuf_stream, tlv.value_len, trap->ts);
443 }
444 
445 #endif /* LWIP_SNMP */
446