1 /*	$OpenBSD: imsg.c,v 1.16 2017/12/14 09:27:44 kettenis Exp $	*/
2 
3 /*
4  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
5  *
6  * Permission to use, copy, modify, and distribute this software for any
7  * purpose with or without fee is hereby granted, provided that the above
8  * copyright notice and this permission notice appear in all copies.
9  *
10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17  */
18 
19 #include "compat.h"
20 
21 #include <sys/types.h>
22 #include <sys/socket.h>
23 #include <sys/uio.h>
24 
25 #include <errno.h>
26 #include <stdlib.h>
27 #include <string.h>
28 #include <unistd.h>
29 
30 #include "imsg.h"
31 
32 int	 imsg_fd_overhead = 0;
33 
34 static int	 imsg_get_fd(struct imsgbuf *);
35 
36 void
37 imsg_init(struct imsgbuf *ibuf, int fd)
38 {
39 	msgbuf_init(&ibuf->w);
40 	memset(&ibuf->r, 0, sizeof(ibuf->r));
41 	ibuf->fd = fd;
42 	ibuf->w.fd = fd;
43 	ibuf->pid = getpid();
44 	TAILQ_INIT(&ibuf->fds);
45 }
46 
47 ssize_t
48 imsg_read(struct imsgbuf *ibuf)
49 {
50 	struct msghdr		 msg;
51 	struct cmsghdr		*cmsg;
52 	union {
53 		struct cmsghdr hdr;
54 		char	buf[CMSG_SPACE(sizeof(int) * 1)];
55 	} cmsgbuf;
56 	struct iovec		 iov;
57 	ssize_t			 n = -1;
58 	int			 fd;
59 	struct imsg_fd		*ifd;
60 
61 	memset(&msg, 0, sizeof(msg));
62 	memset(&cmsgbuf, 0, sizeof(cmsgbuf));
63 
64 	iov.iov_base = ibuf->r.buf + ibuf->r.wpos;
65 	iov.iov_len = sizeof(ibuf->r.buf) - ibuf->r.wpos;
66 	msg.msg_iov = &iov;
67 	msg.msg_iovlen = 1;
68 	msg.msg_control = &cmsgbuf.buf;
69 	msg.msg_controllen = sizeof(cmsgbuf.buf);
70 
71 	if ((ifd = calloc(1, sizeof(struct imsg_fd))) == NULL)
72 		return (-1);
73 
74 again:
75 	if (getdtablecount() + imsg_fd_overhead +
76 	    (int)((CMSG_SPACE(sizeof(int))-CMSG_SPACE(0))/sizeof(int))
77 	    >= getdtablesize()) {
78 		errno = EAGAIN;
79 		free(ifd);
80 		return (-1);
81 	}
82 
83 	if ((n = recvmsg(ibuf->fd, &msg, 0)) == -1) {
84 		if (errno == EINTR)
85 			goto again;
86 		goto fail;
87 	}
88 
89 	ibuf->r.wpos += n;
90 
91 	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
92 	    cmsg = CMSG_NXTHDR(&msg, cmsg)) {
93 		if (cmsg->cmsg_level == SOL_SOCKET &&
94 		    cmsg->cmsg_type == SCM_RIGHTS) {
95 			int i;
96 			int j;
97 
98 			/*
99 			 * We only accept one file descriptor.  Due to C
100 			 * padding rules, our control buffer might contain
101 			 * more than one fd, and we must close them.
102 			 */
103 			j = ((char *)cmsg + cmsg->cmsg_len -
104 			    (char *)CMSG_DATA(cmsg)) / sizeof(int);
105 			for (i = 0; i < j; i++) {
106 				fd = ((int *)CMSG_DATA(cmsg))[i];
107 				if (ifd != NULL) {
108 					ifd->fd = fd;
109 					TAILQ_INSERT_TAIL(&ibuf->fds, ifd,
110 					    entry);
111 					ifd = NULL;
112 				} else
113 					close(fd);
114 			}
115 		}
116 		/* we do not handle other ctl data level */
117 	}
118 
119 fail:
120 	free(ifd);
121 	return (n);
122 }
123 
124 ssize_t
125 imsg_get(struct imsgbuf *ibuf, struct imsg *imsg)
126 {
127 	size_t			 av, left, datalen;
128 
129 	av = ibuf->r.wpos;
130 
131 	if (IMSG_HEADER_SIZE > av)
132 		return (0);
133 
134 	memcpy(&imsg->hdr, ibuf->r.buf, sizeof(imsg->hdr));
135 	if (imsg->hdr.len < IMSG_HEADER_SIZE ||
136 	    imsg->hdr.len > MAX_IMSGSIZE) {
137 		errno = ERANGE;
138 		return (-1);
139 	}
140 	if (imsg->hdr.len > av)
141 		return (0);
142 	datalen = imsg->hdr.len - IMSG_HEADER_SIZE;
143 	ibuf->r.rptr = ibuf->r.buf + IMSG_HEADER_SIZE;
144 	if (datalen == 0)
145 		imsg->data = NULL;
146 	else if ((imsg->data = malloc(datalen)) == NULL)
147 		return (-1);
148 
149 	if (imsg->hdr.flags & IMSGF_HASFD)
150 		imsg->fd = imsg_get_fd(ibuf);
151 	else
152 		imsg->fd = -1;
153 
154 	memcpy(imsg->data, ibuf->r.rptr, datalen);
155 
156 	if (imsg->hdr.len < av) {
157 		left = av - imsg->hdr.len;
158 		memmove(&ibuf->r.buf, ibuf->r.buf + imsg->hdr.len, left);
159 		ibuf->r.wpos = left;
160 	} else
161 		ibuf->r.wpos = 0;
162 
163 	return (datalen + IMSG_HEADER_SIZE);
164 }
165 
166 int
167 imsg_compose(struct imsgbuf *ibuf, uint32_t type, uint32_t peerid, pid_t pid,
168     int fd, const void *data, uint16_t datalen)
169 {
170 	struct ibuf	*wbuf;
171 
172 	if ((wbuf = imsg_create(ibuf, type, peerid, pid, datalen)) == NULL)
173 		return (-1);
174 
175 	if (imsg_add(wbuf, data, datalen) == -1)
176 		return (-1);
177 
178 	wbuf->fd = fd;
179 
180 	imsg_close(ibuf, wbuf);
181 
182 	return (1);
183 }
184 
185 int
186 imsg_composev(struct imsgbuf *ibuf, uint32_t type, uint32_t peerid, pid_t pid,
187     int fd, const struct iovec *iov, int iovcnt)
188 {
189 	struct ibuf	*wbuf;
190 	int		 i, datalen = 0;
191 
192 	for (i = 0; i < iovcnt; i++)
193 		datalen += iov[i].iov_len;
194 
195 	if ((wbuf = imsg_create(ibuf, type, peerid, pid, datalen)) == NULL)
196 		return (-1);
197 
198 	for (i = 0; i < iovcnt; i++)
199 		if (imsg_add(wbuf, iov[i].iov_base, iov[i].iov_len) == -1)
200 			return (-1);
201 
202 	wbuf->fd = fd;
203 
204 	imsg_close(ibuf, wbuf);
205 
206 	return (1);
207 }
208 
209 /* ARGSUSED */
210 struct ibuf *
211 imsg_create(struct imsgbuf *ibuf, uint32_t type, uint32_t peerid, pid_t pid,
212     uint16_t datalen)
213 {
214 	struct ibuf	*wbuf;
215 	struct imsg_hdr	 hdr;
216 
217 	datalen += IMSG_HEADER_SIZE;
218 	if (datalen > MAX_IMSGSIZE) {
219 		errno = ERANGE;
220 		return (NULL);
221 	}
222 
223 	hdr.type = type;
224 	hdr.flags = 0;
225 	hdr.peerid = peerid;
226 	if ((hdr.pid = pid) == 0)
227 		hdr.pid = ibuf->pid;
228 	if ((wbuf = ibuf_dynamic(datalen, MAX_IMSGSIZE)) == NULL) {
229 		return (NULL);
230 	}
231 	if (imsg_add(wbuf, &hdr, sizeof(hdr)) == -1)
232 		return (NULL);
233 
234 	return (wbuf);
235 }
236 
237 int
238 imsg_add(struct ibuf *msg, const void *data, uint16_t datalen)
239 {
240 	if (datalen)
241 		if (ibuf_add(msg, data, datalen) == -1) {
242 			ibuf_free(msg);
243 			return (-1);
244 		}
245 	return (datalen);
246 }
247 
248 void
249 imsg_close(struct imsgbuf *ibuf, struct ibuf *msg)
250 {
251 	struct imsg_hdr	*hdr;
252 
253 	hdr = (struct imsg_hdr *)msg->buf;
254 
255 	hdr->flags &= ~IMSGF_HASFD;
256 	if (msg->fd != -1)
257 		hdr->flags |= IMSGF_HASFD;
258 
259 	hdr->len = (uint16_t)msg->wpos;
260 
261 	ibuf_close(&ibuf->w, msg);
262 }
263 
264 void
265 imsg_free(struct imsg *imsg)
266 {
267 	freezero(imsg->data, imsg->hdr.len - IMSG_HEADER_SIZE);
268 }
269 
270 static int
271 imsg_get_fd(struct imsgbuf *ibuf)
272 {
273 	int		 fd;
274 	struct imsg_fd	*ifd;
275 
276 	if ((ifd = TAILQ_FIRST(&ibuf->fds)) == NULL)
277 		return (-1);
278 
279 	fd = ifd->fd;
280 	TAILQ_REMOVE(&ibuf->fds, ifd, entry);
281 	free(ifd);
282 
283 	return (fd);
284 }
285 
286 int
287 imsg_flush(struct imsgbuf *ibuf)
288 {
289 	while (ibuf->w.queued)
290 		if (msgbuf_write(&ibuf->w) <= 0)
291 			return (-1);
292 	return (0);
293 }
294 
295 void
296 imsg_clear(struct imsgbuf *ibuf)
297 {
298 	int	fd;
299 
300 	msgbuf_clear(&ibuf->w);
301 	while ((fd = imsg_get_fd(ibuf)) != -1)
302 		close(fd);
303 }