Annotation of src/usr.bin/write/write.c, Revision 1.36
1.36 ! deraadt 1: /* $OpenBSD: write.c,v 1.35 2019/06/28 13:35:05 deraadt Exp $ */
1.1 deraadt 2: /* $NetBSD: write.c,v 1.5 1995/08/31 21:48:32 jtc Exp $ */
3:
4: /*
5: * Copyright (c) 1989, 1993
6: * The Regents of the University of California. All rights reserved.
7: *
8: * This code is derived from software contributed to Berkeley by
9: * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
10: *
11: * Redistribution and use in source and binary forms, with or without
12: * modification, are permitted provided that the following conditions
13: * are met:
14: * 1. Redistributions of source code must retain the above copyright
15: * notice, this list of conditions and the following disclaimer.
16: * 2. Redistributions in binary form must reproduce the above copyright
17: * notice, this list of conditions and the following disclaimer in the
18: * documentation and/or other materials provided with the distribution.
1.20 millert 19: * 3. Neither the name of the University nor the names of its contributors
1.1 deraadt 20: * may be used to endorse or promote products derived from this software
21: * without specific prior written permission.
22: *
23: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33: * SUCH DAMAGE.
34: */
35:
36: #include <sys/stat.h>
1.33 martijn 37:
1.1 deraadt 38: #include <ctype.h>
1.33 martijn 39: #include <err.h>
40: #include <fcntl.h>
41: #include <limits.h>
42: #include <paths.h>
43: #include <pwd.h>
44: #include <signal.h>
1.1 deraadt 45: #include <stdio.h>
1.22 david 46: #include <stdlib.h>
1.1 deraadt 47: #include <string.h>
48: #include <time.h>
49: #include <unistd.h>
50: #include <utmp.h>
51:
1.15 millert 52: void done(int sig);
53: void do_write(char *, char *, uid_t);
54: void wr_fputs(char *);
1.19 deraadt 55: void search_utmp(char *, char *, int, char *, uid_t);
1.15 millert 56: int term_chk(char *, int *, time_t *, int);
57: int utmp_chk(char *, char *);
1.33 martijn 58: static int isu8cont(unsigned char c);
1.1 deraadt 59:
60: int
1.21 deraadt 61: main(int argc, char *argv[])
1.1 deraadt 62: {
1.28 deraadt 63: char tty[PATH_MAX], *mytty, *cp;
1.17 deraadt 64: int msgsok, myttyfd;
1.1 deraadt 65: time_t atime;
66: uid_t myuid;
67:
68: /* check that sender has write enabled */
69: if (isatty(fileno(stdin)))
70: myttyfd = fileno(stdin);
71: else if (isatty(fileno(stdout)))
72: myttyfd = fileno(stdout);
73: else if (isatty(fileno(stderr)))
74: myttyfd = fileno(stderr);
75: else
76: errx(1, "can't find your tty");
77: if (!(mytty = ttyname(myttyfd)))
78: errx(1, "can't find your tty's name");
1.12 jasoni 79: if ((cp = strrchr(mytty, '/')))
1.1 deraadt 80: mytty = cp + 1;
81: if (term_chk(mytty, &msgsok, &atime, 1))
82: exit(1);
83: if (!msgsok)
1.2 deraadt 84: warnx("you have write permission turned off");
1.1 deraadt 85:
86: myuid = getuid();
87:
88: /* check args */
89: switch (argc) {
90: case 2:
1.19 deraadt 91: search_utmp(argv[1], tty, sizeof tty, mytty, myuid);
1.1 deraadt 92: do_write(tty, mytty, myuid);
93: break;
94: case 3:
1.16 fgsch 95: if (!strncmp(argv[2], _PATH_DEV, sizeof(_PATH_DEV) - 1))
96: argv[2] += sizeof(_PATH_DEV) - 1;
1.1 deraadt 97: if (utmp_chk(argv[1], argv[2]))
98: errx(1, "%s is not logged in on %s",
99: argv[1], argv[2]);
100: if (term_chk(argv[2], &msgsok, &atime, 1))
101: exit(1);
102: if (myuid && !msgsok)
103: errx(1, "%s has messages disabled on %s",
104: argv[1], argv[2]);
105: do_write(argv[2], mytty, myuid);
106: break;
107: default:
1.25 sobrado 108: (void)fprintf(stderr, "usage: write user [ttyname]\n");
1.1 deraadt 109: exit(1);
110: }
1.11 deraadt 111: done(0);
1.12 jasoni 112:
1.1 deraadt 113: /* NOTREACHED */
1.12 jasoni 114: return (0);
1.1 deraadt 115: }
116:
117: /*
118: * utmp_chk - checks that the given user is actually logged in on
119: * the given tty
120: */
121: int
1.17 deraadt 122: utmp_chk(char *user, char *tty)
1.1 deraadt 123: {
124: struct utmp u;
125: int ufd;
126:
1.35 deraadt 127: if ((ufd = open(_PATH_UTMP, O_RDONLY)) == -1)
1.24 deraadt 128: return(1); /* no utmp, cannot talk to users */
1.1 deraadt 129:
130: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
131: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
132: strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
133: (void)close(ufd);
134: return(0);
135: }
136:
137: (void)close(ufd);
138: return(1);
139: }
140:
141: /*
142: * search_utmp - search utmp for the "best" terminal to write to
143: *
144: * Ignores terminals with messages disabled, and of the rest, returns
145: * the one with the most recent access time. Returns as value the number
146: * of the user's terminals with messages enabled, or -1 if the user is
147: * not logged in at all.
148: *
149: * Special case for writing to yourself - ignore the terminal you're
150: * writing from, unless that's the only terminal with messages enabled.
151: */
152: void
1.19 deraadt 153: search_utmp(char *user, char *tty, int ttyl, char *mytty, uid_t myuid)
1.1 deraadt 154: {
155: struct utmp u;
156: time_t bestatime, atime;
157: int ufd, nloggedttys, nttys, msgsok, user_is_me;
158: char atty[UT_LINESIZE + 1];
159:
1.35 deraadt 160: if ((ufd = open(_PATH_UTMP, O_RDONLY)) == -1)
1.1 deraadt 161: err(1, "%s", _PATH_UTMP);
162:
163: nloggedttys = nttys = 0;
164: bestatime = 0;
165: user_is_me = 0;
166: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
167: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
168: ++nloggedttys;
169: (void)strncpy(atty, u.ut_line, UT_LINESIZE);
170: atty[UT_LINESIZE] = '\0';
171: if (term_chk(atty, &msgsok, &atime, 0))
172: continue; /* bad term? skip */
173: if (myuid && !msgsok)
174: continue; /* skip ttys with msgs off */
175: if (strcmp(atty, mytty) == 0) {
176: user_is_me = 1;
177: continue; /* don't write to yourself */
178: }
179: ++nttys;
180: if (atime > bestatime) {
181: bestatime = atime;
1.19 deraadt 182: (void)strlcpy(tty, atty, ttyl);
1.1 deraadt 183: }
184: }
185:
186: (void)close(ufd);
187: if (nloggedttys == 0)
188: errx(1, "%s is not logged in", user);
189: if (nttys == 0) {
190: if (user_is_me) { /* ok, so write to yourself! */
1.19 deraadt 191: (void)strlcpy(tty, mytty, ttyl);
1.1 deraadt 192: return;
193: }
194: errx(1, "%s has messages disabled", user);
195: } else if (nttys > 1)
196: warnx("%s is logged in more than once; writing to %s",
197: user, tty);
198: }
199:
200: /*
201: * term_chk - check that a terminal exists, and get the message bit
202: * and the access time
203: */
204: int
1.17 deraadt 205: term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
1.1 deraadt 206: {
207: struct stat s;
1.28 deraadt 208: char path[PATH_MAX];
1.1 deraadt 209:
1.7 downsj 210: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.35 deraadt 211: if (stat(path, &s) == -1) {
1.1 deraadt 212: if (showerror)
213: warn("%s", path);
214: return(1);
215: }
1.9 deraadt 216: *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */
1.1 deraadt 217: *atimeP = s.st_atime;
218: return(0);
219: }
220:
221: /*
222: * do_write - actually make the connection
223: */
224: void
1.17 deraadt 225: do_write(char *tty, char *mytty, uid_t myuid)
1.1 deraadt 226: {
1.34 millert 227: const char *login;
228: char *nows;
1.1 deraadt 229: time_t now;
1.28 deraadt 230: char path[PATH_MAX], host[HOST_NAME_MAX+1], line[512];
1.23 djm 231: gid_t gid;
1.32 bluhm 232: int fd;
1.1 deraadt 233:
234: /* Determine our login name before the we reopen() stdout */
1.34 millert 235: if ((login = getlogin()) == NULL)
236: login = user_from_uid(myuid, 0);
1.1 deraadt 237:
1.7 downsj 238: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.36 ! deraadt 239: fd = open(path, O_WRONLY);
1.32 bluhm 240: if (fd == -1)
241: err(1, "open %s", path);
242: fflush(stdout);
243: if (dup2(fd, STDOUT_FILENO) == -1)
244: err(1, "dup2 %s", path);
245: if (fd != STDOUT_FILENO)
246: close(fd);
1.1 deraadt 247:
1.17 deraadt 248: /* revoke privs, now that we have opened the tty */
1.23 djm 249: gid = getgid();
250: if (setresgid(gid, gid, gid) == -1)
251: err(1, "setresgid");
1.30 deraadt 252:
253: /*
254: * Unfortunately this is rather late - well after utmp
255: * parsing, then pinned by the tty open and setresgid
256: */
1.31 deraadt 257: if (pledge("stdio", NULL) == -1)
258: err(1, "pledge");
1.17 deraadt 259:
1.1 deraadt 260: (void)signal(SIGINT, done);
261: (void)signal(SIGHUP, done);
262:
263: /* print greeting */
1.35 deraadt 264: if (gethostname(host, sizeof(host)) == -1)
1.19 deraadt 265: (void)strlcpy(host, "???", sizeof host);
1.27 deraadt 266: now = time(NULL);
1.1 deraadt 267: nows = ctime(&now);
268: nows[16] = '\0';
269: (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
270: login, host, mytty, nows + 11);
271:
272: while (fgets(line, sizeof(line), stdin) != NULL)
273: wr_fputs(line);
274: }
275:
276: /*
277: * done - cleanup and exit
278: */
279: void
1.11 deraadt 280: done(int sig)
1.1 deraadt 281: {
1.13 deraadt 282: (void)write(STDOUT_FILENO, "EOF\r\n", 5);
1.11 deraadt 283: if (sig)
284: _exit(0);
285: else
286: exit(0);
1.1 deraadt 287: }
288:
289: /*
290: * wr_fputs - like fputs(), but makes control characters visible and
291: * turns \n into \r\n
292: */
293: void
1.17 deraadt 294: wr_fputs(char *s)
1.1 deraadt 295: {
296:
297: #define PUTC(c) if (putchar(c) == EOF) goto err;
298:
299: for (; *s != '\0'; ++s) {
1.33 martijn 300: if (*s == '\n') {
1.1 deraadt 301: PUTC('\r');
1.5 deraadt 302: PUTC('\n');
303: continue;
1.3 deraadt 304: }
1.33 martijn 305: if (isu8cont(*s))
306: continue;
307: if (isprint(*s) || isspace(*s) || *s == '\a') {
308: PUTC(*s);
309: } else {
310: PUTC('?');
311: }
312:
1.1 deraadt 313: }
314: return;
315:
316: err: err(1, NULL);
317: #undef PUTC
1.33 martijn 318: }
319:
320: static int
321: isu8cont(unsigned char c)
322: {
323: return (c & (0x80 | 0x40)) == 0x80;
1.1 deraadt 324: }
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