xref: /freebsd/contrib/bsnmp/snmpd/trans_udp.c (revision ab00ac327a66a53edaac95b536b209db3ae2cd9f) 
1 /*
2  * Copyright (c) 2003
3  *	Fraunhofer Institute for Open Communication Systems (FhG Fokus).
4  *	All rights reserved.
5  *
6  * Author: Harti Brandt <harti@freebsd.org>
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * $Begemot: bsnmp/snmpd/trans_udp.c,v 1.5 2005/10/04 08:46:56 brandt_h Exp $
30  *
31  * UDP transport
32  */
33 #include <sys/types.h>
34 #include <sys/queue.h>
35 #include <sys/ucred.h>
36 
37 #include <stdbool.h>
38 #include <stdlib.h>
39 #include <syslog.h>
40 #include <string.h>
41 #include <errno.h>
42 #include <unistd.h>
43 
44 #include <netinet/in.h>
45 #include <arpa/inet.h>
46 
47 #include "snmpmod.h"
48 #include "snmpd.h"
49 #include "trans_udp.h"
50 #include "tree.h"
51 #include "oid.h"
52 
53 static int udp_start(void);
54 static int udp_stop(int);
55 static void udp_close_port(struct tport *);
56 static int udp_init_port(struct tport *);
57 static ssize_t udp_send(struct tport *, const u_char *, size_t,
58     const struct sockaddr *, size_t);
59 static ssize_t udp_recv(struct tport *, struct port_input *);
60 
61 /* exported */
62 const struct transport_def udp_trans = {
63 	"udp",
64 	OIDX_begemotSnmpdTransUdp,
65 	udp_start,
66 	udp_stop,
67 	udp_close_port,
68 	udp_init_port,
69 	udp_send,
70 	udp_recv
71 };
72 static struct transport *my_trans;
73 
74 static int
75 udp_start(void)
76 {
77 	return (trans_register(&udp_trans, &my_trans));
78 }
79 
80 static int
81 udp_stop(int force __unused)
82 {
83 	if (my_trans != NULL)
84 		if (trans_unregister(my_trans) != 0)
85 			return (SNMP_ERR_GENERR);
86 	return (SNMP_ERR_NOERROR);
87 }
88 
89 /*
90  * A UDP port is ready
91  */
92 static void
93 udp_input(int fd __unused, void *udata)
94 {
95 	struct udp_port *p = udata;
96 
97 	p->input.peerlen = sizeof(p->ret);
98 	snmpd_input(&p->input, &p->tport);
99 }
100 
101 /*
102  * Create a UDP socket and bind it to the given port
103  */
104 static int
105 udp_init_port(struct tport *tp)
106 {
107 	struct udp_port *p = (struct udp_port *)tp;
108 	struct sockaddr_in addr;
109 	u_int32_t ip;
110 	const int on = 1;
111 
112 	if ((p->input.fd = socket(PF_INET, SOCK_DGRAM, 0)) < 0) {
113 		syslog(LOG_ERR, "creating UDP socket: %m");
114 		return (SNMP_ERR_RES_UNAVAIL);
115 	}
116 	ip = (p->addr[0] << 24) | (p->addr[1] << 16) | (p->addr[2] << 8) |
117 	    p->addr[3];
118 	memset(&addr, 0, sizeof(addr));
119 	addr.sin_addr.s_addr = htonl(ip);
120 	addr.sin_port = htons(p->port);
121 	addr.sin_family = AF_INET;
122 	addr.sin_len = sizeof(addr);
123 	if (addr.sin_addr.s_addr == INADDR_ANY) {
124 		if (setsockopt(p->input.fd, IPPROTO_IP, IP_RECVDSTADDR, &on,
125 		    sizeof(on)) == -1) {
126 			syslog(LOG_ERR, "setsockopt(IP_RECVDSTADDR): %m");
127 			close(p->input.fd);
128 			p->input.fd = -1;
129 			return (SNMP_ERR_GENERR);
130 		}
131 		p->recvdstaddr = true;
132 	}
133 	if (bind(p->input.fd, (struct sockaddr *)&addr, sizeof(addr))) {
134 		if (errno == EADDRNOTAVAIL) {
135 			close(p->input.fd);
136 			p->input.fd = -1;
137 			return (SNMP_ERR_INCONS_NAME);
138 		}
139 		syslog(LOG_ERR, "bind: %s:%u %m", inet_ntoa(addr.sin_addr),
140 		    p->port);
141 		close(p->input.fd);
142 		p->input.fd = -1;
143 		return (SNMP_ERR_GENERR);
144 	}
145 	if ((p->input.id = fd_select(p->input.fd, udp_input,
146 	    p, NULL)) == NULL) {
147 		close(p->input.fd);
148 		p->input.fd = -1;
149 		return (SNMP_ERR_GENERR);
150 	}
151 	return (SNMP_ERR_NOERROR);
152 }
153 
154 /*
155  * Create a new SNMP Port object and start it, if we are not
156  * in initialization mode. The arguments are in host byte order.
157  */
158 static int
159 udp_open_port(u_int8_t *addr, u_int32_t udp_port, struct udp_port **pp)
160 {
161 	struct udp_port *port;
162 	int err;
163 
164 	if (udp_port > 0xffff)
165 		return (SNMP_ERR_NO_CREATION);
166 	if ((port = malloc(sizeof(*port))) == NULL)
167 		return (SNMP_ERR_GENERR);
168 	memset(port, 0, sizeof(*port));
169 
170 	/* initialize common part */
171 	port->tport.index.len = 5;
172 	port->tport.index.subs[0] = addr[0];
173 	port->tport.index.subs[1] = addr[1];
174 	port->tport.index.subs[2] = addr[2];
175 	port->tport.index.subs[3] = addr[3];
176 	port->tport.index.subs[4] = udp_port;
177 
178 	port->addr[0] = addr[0];
179 	port->addr[1] = addr[1];
180 	port->addr[2] = addr[2];
181 	port->addr[3] = addr[3];
182 	port->port = udp_port;
183 
184 	port->input.fd = -1;
185 	port->input.id = NULL;
186 	port->input.stream = 0;
187 	port->input.cred = 0;
188 	port->input.peer = (struct sockaddr *)&port->ret;
189 	port->input.peerlen = sizeof(port->ret);
190 
191 	trans_insert_port(my_trans, &port->tport);
192 
193 	if (community != COMM_INITIALIZE &&
194 	    (err = udp_init_port(&port->tport)) != SNMP_ERR_NOERROR) {
195 		udp_close_port(&port->tport);
196 		return (err);
197 	}
198 	*pp = port;
199 	return (SNMP_ERR_NOERROR);
200 }
201 
202 /*
203  * Close an SNMP port
204  */
205 static void
206 udp_close_port(struct tport *tp)
207 {
208 	struct udp_port *port = (struct udp_port *)tp;
209 
210 	snmpd_input_close(&port->input);
211 	trans_remove_port(tp);
212 	free(port);
213 }
214 
215 /*
216  * Send something
217  */
218 static ssize_t
219 udp_send(struct tport *tp, const u_char *buf, size_t len,
220     const struct sockaddr *addr, size_t addrlen)
221 {
222 	struct udp_port *p = (struct udp_port *)tp;
223 	struct cmsghdr *cmsg;
224 	struct msghdr msg;
225 	char cbuf[CMSG_SPACE(sizeof(struct in_addr))];
226 	struct iovec iov;
227 
228 	iov.iov_base = __DECONST(void*, buf);
229 	iov.iov_len = len;
230 
231 	msg.msg_flags = 0;
232 	msg.msg_iov = &iov;
233 	msg.msg_iovlen = 1;
234 	msg.msg_name = __DECONST(void *, addr);
235 	msg.msg_namelen = addrlen;
236 
237 	if (p->recvdstaddr) {
238 		msg.msg_control = cbuf;
239 		msg.msg_controllen = sizeof(cbuf);
240 
241 		cmsg = CMSG_FIRSTHDR(&msg);
242 		cmsg->cmsg_level = IPPROTO_IP;
243 		cmsg->cmsg_type = IP_SENDSRCADDR;
244 		cmsg->cmsg_len = CMSG_LEN(sizeof(struct in_addr));
245 		memcpy(CMSG_DATA(cmsg), &p->dstaddr, sizeof(struct in_addr));
246 	} else {
247 		msg.msg_control = NULL;
248 		msg.msg_controllen = 0;
249 	}
250 
251 	return (sendmsg(p->input.fd, &msg, 0));
252 }
253 
254 static void
255 check_priv_dgram(struct port_input *pi, struct sockcred *cred)
256 {
257 
258 	/* process explicitly sends credentials */
259 	if (cred)
260 		pi->priv = (cred->sc_euid == 0);
261 	else
262 		pi->priv = 0;
263 }
264 
265 /*
266  * Input from a datagram socket.
267  * Each receive should return one datagram.
268  */
269 static ssize_t
270 udp_recv(struct tport *tp, struct port_input *pi)
271 {
272 	u_char embuf[1000];
273 	char cbuf[CMSG_SPACE(SOCKCREDSIZE(CMGROUP_MAX)) +
274 	    CMSG_SPACE(sizeof(struct in_addr))];
275 	struct udp_port *p = (struct udp_port *)tp;
276 	struct msghdr msg;
277 	struct iovec iov[1];
278 	ssize_t len;
279 	struct cmsghdr *cmsg;
280 	struct sockcred *cred = NULL;
281 
282 	if (pi->buf == NULL) {
283 		/* no buffer yet - allocate one */
284 		if ((pi->buf = buf_alloc(0)) == NULL) {
285 			/* ups - could not get buffer. Read away input
286 			 * and drop it */
287 			(void)recvfrom(pi->fd, embuf, sizeof(embuf),
288 			    0, NULL, NULL);
289 			/* return error */
290 			return (-1);
291 		}
292 		pi->buflen = buf_size(0);
293 	}
294 
295 	/* try to get a message */
296 	msg.msg_name = pi->peer;
297 	msg.msg_namelen = pi->peerlen;
298 	msg.msg_iov = iov;
299 	msg.msg_iovlen = 1;
300 	memset(cbuf, 0, sizeof(cbuf));
301 	msg.msg_control = cbuf;
302 	msg.msg_controllen = sizeof(cbuf);
303 	msg.msg_flags = 0;
304 
305 	iov[0].iov_base = pi->buf;
306 	iov[0].iov_len = pi->buflen;
307 
308 	len = recvmsg(pi->fd, &msg, 0);
309 
310 	if (len == -1 || len == 0)
311 		/* receive error */
312 		return (-1);
313 
314 	if (msg.msg_flags & MSG_TRUNC) {
315 		/* truncated - drop */
316 		snmpd_stats.silentDrops++;
317 		snmpd_stats.inTooLong++;
318 		return (-1);
319 	}
320 
321 	pi->length = (size_t)len;
322 
323 	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
324 	    cmsg = CMSG_NXTHDR(&msg, cmsg)) {
325 		if (cmsg->cmsg_level == IPPROTO_IP &&
326 		    cmsg->cmsg_type == IP_RECVDSTADDR)
327 			memcpy(&p->dstaddr, CMSG_DATA(cmsg),
328 			    sizeof(struct in_addr));
329 		if (cmsg->cmsg_level == SOL_SOCKET &&
330 		    cmsg->cmsg_type == SCM_CREDS)
331 			cred = (struct sockcred *)CMSG_DATA(cmsg);
332 	}
333 
334 	if (pi->cred)
335 		check_priv_dgram(pi, cred);
336 
337 	return (0);
338 }
339 
340 /*
341  * Port table
342  */
343 int
344 op_snmp_port(struct snmp_context *ctx, struct snmp_value *value,
345     u_int sub, u_int iidx, enum snmp_op op)
346 {
347 	asn_subid_t which = value->var.subs[sub-1];
348 	struct udp_port *p;
349 	u_int8_t addr[4];
350 	u_int32_t port;
351 
352 	switch (op) {
353 
354 	  case SNMP_OP_GETNEXT:
355 		if ((p = (struct udp_port *)trans_next_port(my_trans,
356 		    &value->var, sub)) == NULL)
357 			return (SNMP_ERR_NOSUCHNAME);
358 		index_append(&value->var, sub, &p->tport.index);
359 		break;
360 
361 	  case SNMP_OP_GET:
362 		if ((p = (struct udp_port *)trans_find_port(my_trans,
363 		    &value->var, sub)) == NULL)
364 			return (SNMP_ERR_NOSUCHNAME);
365 		break;
366 
367 	  case SNMP_OP_SET:
368 		p = (struct udp_port *)trans_find_port(my_trans,
369 		    &value->var, sub);
370 		ctx->scratch->int1 = (p != NULL);
371 
372 		if (which != LEAF_begemotSnmpdPortStatus)
373 			abort();
374 		if (!TRUTH_OK(value->v.integer))
375 			return (SNMP_ERR_WRONG_VALUE);
376 
377 		ctx->scratch->int2 = TRUTH_GET(value->v.integer);
378 
379 		if (ctx->scratch->int2) {
380 			/* open an SNMP port */
381 			if (p != NULL)
382 				/* already open - do nothing */
383 				return (SNMP_ERR_NOERROR);
384 
385 			if (index_decode(&value->var, sub, iidx, addr, &port))
386 				return (SNMP_ERR_NO_CREATION);
387 			return (udp_open_port(addr, port, &p));
388 
389 		} else {
390 			/* close SNMP port - do in commit */
391 		}
392 		return (SNMP_ERR_NOERROR);
393 
394 	  case SNMP_OP_ROLLBACK:
395 		p = (struct udp_port *)trans_find_port(my_trans,
396 		    &value->var, sub);
397 		if (ctx->scratch->int1 == 0) {
398 			/* did not exist */
399 			if (ctx->scratch->int2 == 1) {
400 				/* created */
401 				if (p != NULL)
402 					udp_close_port(&p->tport);
403 			}
404 		}
405 		return (SNMP_ERR_NOERROR);
406 
407 	  case SNMP_OP_COMMIT:
408 		p = (struct udp_port *)trans_find_port(my_trans,
409 		    &value->var, sub);
410 		if (ctx->scratch->int1 == 1) {
411 			/* did exist */
412 			if (ctx->scratch->int2 == 0) {
413 				/* delete */
414 				if (p != NULL)
415 					udp_close_port(&p->tport);
416 			}
417 		}
418 		return (SNMP_ERR_NOERROR);
419 
420 	  default:
421 		abort();
422 	}
423 
424 	/*
425 	 * Come here to fetch the value
426 	 */
427 	switch (which) {
428 
429 	  case LEAF_begemotSnmpdPortStatus:
430 		value->v.integer = 1;
431 		break;
432 
433 	  default:
434 		abort();
435 	}
436 
437 	return (SNMP_ERR_NOERROR);
438 }
439