1 /*	$OpenBSD: imsg.c,v 1.17 2022/01/28 10:41:44 claudio 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 <sys/types.h>
20 #include <sys/queue.h>
21 #include <sys/socket.h>
22 #include <sys/uio.h>
23 
24 #include <errno.h>
25 #include <stdlib.h>
26 #include <string.h>
27 #include <unistd.h>
28 
29 #include "imsg.h"
30 
31 int	 imsg_fd_overhead = 0;
32 
33 static int	 imsg_get_fd(struct imsgbuf *);
34 
35 void
36 imsg_init(struct imsgbuf *ibuf, int fd)
37 {
38 	msgbuf_init(&ibuf->w);
39 	memset(&ibuf->r, 0, sizeof(ibuf->r));
40 	ibuf->fd = fd;
41 	ibuf->w.fd = fd;
42 	ibuf->pid = getpid();
43 	TAILQ_INIT(&ibuf->fds);
44 }
45 
46 ssize_t
47 imsg_read(struct imsgbuf *ibuf)
48 {
49 	struct msghdr		 msg;
50 	struct cmsghdr		*cmsg;
51 	union {
52 		struct cmsghdr hdr;
53 		char	buf[CMSG_SPACE(sizeof(int) * 1)];
54 	} cmsgbuf;
55 	struct iovec		 iov;
56 	ssize_t			 n = -1;
57 	int			 fd;
58 	struct imsg_fd		*ifd;
59 
60 	memset(&msg, 0, sizeof(msg));
61 	memset(&cmsgbuf, 0, sizeof(cmsgbuf));
62 
63 	iov.iov_base = ibuf->r.buf + ibuf->r.wpos;
64 	iov.iov_len = sizeof(ibuf->r.buf) - ibuf->r.wpos;
65 	msg.msg_iov = &iov;
66 	msg.msg_iovlen = 1;
67 	msg.msg_control = &cmsgbuf.buf;
68 	msg.msg_controllen = sizeof(cmsgbuf.buf);
69 
70 	if ((ifd = calloc(1, sizeof(struct imsg_fd))) == NULL)
71 		return (-1);
72 
73 again:
74 	if (getdtablecount() + imsg_fd_overhead +
75 	    (int)((CMSG_SPACE(sizeof(int))-CMSG_SPACE(0))/sizeof(int))
76 	    >= getdtablesize()) {
77 		errno = EAGAIN;
78 		free(ifd);
79 		return (-1);
80 	}
81 
82 	if ((n = recvmsg(ibuf->fd, &msg, 0)) == -1) {
83 		if (errno == EINTR)
84 			goto again;
85 		goto fail;
86 	}
87 
88 	ibuf->r.wpos += n;
89 
90 	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
91 	    cmsg = CMSG_NXTHDR(&msg, cmsg)) {
92 		if (cmsg->cmsg_level == SOL_SOCKET &&
93 		    cmsg->cmsg_type == SCM_RIGHTS) {
94 			int i;
95 			int j;
96 
97 			/*
98 			 * We only accept one file descriptor.  Due to C
99 			 * padding rules, our control buffer might contain
100 			 * more than one fd, and we must close them.
101 			 */
102 			j = ((char *)cmsg + cmsg->cmsg_len -
103 			    (char *)CMSG_DATA(cmsg)) / sizeof(int);
104 			for (i = 0; i < j; i++) {
105 				fd = ((int *)CMSG_DATA(cmsg))[i];
106 				if (ifd != NULL) {
107 					ifd->fd = fd;
108 					TAILQ_INSERT_TAIL(&ibuf->fds, ifd,
109 					    entry);
110 					ifd = NULL;
111 				} else
112 					close(fd);
113 			}
114 		}
115 		/* we do not handle other ctl data level */
116 	}
117 
118 fail:
119 	free(ifd);
120 	return (n);
121 }
122 
123 ssize_t
124 imsg_get(struct imsgbuf *ibuf, struct imsg *imsg)
125 {
126 	size_t			 av, left, datalen;
127 
128 	av = ibuf->r.wpos;
129 
130 	if (IMSG_HEADER_SIZE > av)
131 		return (0);
132 
133 	memcpy(&imsg->hdr, ibuf->r.buf, sizeof(imsg->hdr));
134 	if (imsg->hdr.len < IMSG_HEADER_SIZE ||
135 	    imsg->hdr.len > MAX_IMSGSIZE) {
136 		errno = ERANGE;
137 		return (-1);
138 	}
139 	if (imsg->hdr.len > av)
140 		return (0);
141 	datalen = imsg->hdr.len - IMSG_HEADER_SIZE;
142 	ibuf->r.rptr = ibuf->r.buf + IMSG_HEADER_SIZE;
143 	if (datalen == 0)
144 		imsg->data = NULL;
145 	else if ((imsg->data = malloc(datalen)) == NULL)
146 		return (-1);
147 
148 	if (imsg->hdr.flags & IMSGF_HASFD)
149 		imsg->fd = imsg_get_fd(ibuf);
150 	else
151 		imsg->fd = -1;
152 
153 	if (datalen != 0)
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 }