Annotation of src/usr.bin/write/write.c, Revision 1.17
1.17 ! deraadt 1: /* $OpenBSD: write.c,v 1.16 2002/02/21 07:32:55 fgsch 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.
19: * 3. All advertising materials mentioning features or use of this software
20: * must display the following acknowledgement:
21: * This product includes software developed by the University of
22: * California, Berkeley and its contributors.
23: * 4. Neither the name of the University nor the names of its contributors
24: * may be used to endorse or promote products derived from this software
25: * without specific prior written permission.
26: *
27: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
28: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
29: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
31: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
35: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
36: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37: * SUCH DAMAGE.
38: */
39:
40: #ifndef lint
41: static char copyright[] =
42: "@(#) Copyright (c) 1989, 1993\n\
43: The Regents of the University of California. All rights reserved.\n";
44: #endif /* not lint */
45:
46: #ifndef lint
47: #if 0
48: static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95";
49: #endif
1.17 ! deraadt 50: static char *rcsid = "$OpenBSD: write.c,v 1.16 2002/02/21 07:32:55 fgsch Exp $";
1.1 deraadt 51: #endif /* not lint */
52:
53: #include <sys/types.h>
54: #include <sys/param.h>
55: #include <sys/stat.h>
56: #include <ctype.h>
57: #include <stdio.h>
58: #include <string.h>
59: #include <signal.h>
60: #include <time.h>
61: #include <fcntl.h>
1.7 downsj 62: #include <paths.h>
1.1 deraadt 63: #include <pwd.h>
64: #include <unistd.h>
65: #include <utmp.h>
66: #include <err.h>
1.5 deraadt 67: #include <vis.h>
1.1 deraadt 68:
1.15 millert 69: void done(int sig);
70: void do_write(char *, char *, uid_t);
71: void wr_fputs(char *);
72: void search_utmp(char *, char *, char *, uid_t);
73: int term_chk(char *, int *, time_t *, int);
74: int utmp_chk(char *, char *);
1.1 deraadt 75:
76: int
1.17 ! deraadt 77: main(int argc, char **argv)
1.1 deraadt 78: {
1.17 ! deraadt 79: char tty[MAXPATHLEN], *mytty, *cp;
! 80: int msgsok, myttyfd;
1.1 deraadt 81: time_t atime;
82: uid_t myuid;
83:
84: /* check that sender has write enabled */
85: if (isatty(fileno(stdin)))
86: myttyfd = fileno(stdin);
87: else if (isatty(fileno(stdout)))
88: myttyfd = fileno(stdout);
89: else if (isatty(fileno(stderr)))
90: myttyfd = fileno(stderr);
91: else
92: errx(1, "can't find your tty");
93: if (!(mytty = ttyname(myttyfd)))
94: errx(1, "can't find your tty's name");
1.12 jasoni 95: if ((cp = strrchr(mytty, '/')))
1.1 deraadt 96: mytty = cp + 1;
97: if (term_chk(mytty, &msgsok, &atime, 1))
98: exit(1);
99: if (!msgsok)
1.2 deraadt 100: warnx("you have write permission turned off");
1.1 deraadt 101:
102: myuid = getuid();
103:
104: /* check args */
105: switch (argc) {
106: case 2:
107: search_utmp(argv[1], tty, mytty, myuid);
108: do_write(tty, mytty, myuid);
109: break;
110: case 3:
1.16 fgsch 111: if (!strncmp(argv[2], _PATH_DEV, sizeof(_PATH_DEV) - 1))
112: argv[2] += sizeof(_PATH_DEV) - 1;
1.1 deraadt 113: if (utmp_chk(argv[1], argv[2]))
114: errx(1, "%s is not logged in on %s",
115: argv[1], argv[2]);
116: if (term_chk(argv[2], &msgsok, &atime, 1))
117: exit(1);
118: if (myuid && !msgsok)
119: errx(1, "%s has messages disabled on %s",
120: argv[1], argv[2]);
121: do_write(argv[2], mytty, myuid);
122: break;
123: default:
124: (void)fprintf(stderr, "usage: write user [tty]\n");
125: exit(1);
126: }
1.11 deraadt 127: done(0);
1.12 jasoni 128:
1.1 deraadt 129: /* NOTREACHED */
1.12 jasoni 130: return (0);
1.1 deraadt 131: }
132:
133: /*
134: * utmp_chk - checks that the given user is actually logged in on
135: * the given tty
136: */
137: int
1.17 ! deraadt 138: utmp_chk(char *user, char *tty)
1.1 deraadt 139: {
140: struct utmp u;
141: int ufd;
142:
143: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
144: return(0); /* ignore error, shouldn't happen anyway */
145:
146: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
147: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
148: strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
149: (void)close(ufd);
150: return(0);
151: }
152:
153: (void)close(ufd);
154: return(1);
155: }
156:
157: /*
158: * search_utmp - search utmp for the "best" terminal to write to
159: *
160: * Ignores terminals with messages disabled, and of the rest, returns
161: * the one with the most recent access time. Returns as value the number
162: * of the user's terminals with messages enabled, or -1 if the user is
163: * not logged in at all.
164: *
165: * Special case for writing to yourself - ignore the terminal you're
166: * writing from, unless that's the only terminal with messages enabled.
167: */
168: void
1.17 ! deraadt 169: search_utmp(char *user, char *tty, char *mytty, uid_t myuid)
1.1 deraadt 170: {
171: struct utmp u;
172: time_t bestatime, atime;
173: int ufd, nloggedttys, nttys, msgsok, user_is_me;
174: char atty[UT_LINESIZE + 1];
175:
176: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
177: err(1, "%s", _PATH_UTMP);
178:
179: nloggedttys = nttys = 0;
180: bestatime = 0;
181: user_is_me = 0;
182: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
183: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
184: ++nloggedttys;
185: (void)strncpy(atty, u.ut_line, UT_LINESIZE);
186: atty[UT_LINESIZE] = '\0';
187: if (term_chk(atty, &msgsok, &atime, 0))
188: continue; /* bad term? skip */
189: if (myuid && !msgsok)
190: continue; /* skip ttys with msgs off */
191: if (strcmp(atty, mytty) == 0) {
192: user_is_me = 1;
193: continue; /* don't write to yourself */
194: }
195: ++nttys;
196: if (atime > bestatime) {
197: bestatime = atime;
198: (void)strcpy(tty, atty);
199: }
200: }
201:
202: (void)close(ufd);
203: if (nloggedttys == 0)
204: errx(1, "%s is not logged in", user);
205: if (nttys == 0) {
206: if (user_is_me) { /* ok, so write to yourself! */
207: (void)strcpy(tty, mytty);
208: return;
209: }
210: errx(1, "%s has messages disabled", user);
211: } else if (nttys > 1)
212: warnx("%s is logged in more than once; writing to %s",
213: user, tty);
214: }
215:
216: /*
217: * term_chk - check that a terminal exists, and get the message bit
218: * and the access time
219: */
220: int
1.17 ! deraadt 221: term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
1.1 deraadt 222: {
223: struct stat s;
224: char path[MAXPATHLEN];
225:
1.7 downsj 226: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.1 deraadt 227: if (stat(path, &s) < 0) {
228: if (showerror)
229: warn("%s", path);
230: return(1);
231: }
1.9 deraadt 232: *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */
1.1 deraadt 233: *atimeP = s.st_atime;
234: return(0);
235: }
236:
237: /*
238: * do_write - actually make the connection
239: */
240: void
1.17 ! deraadt 241: do_write(char *tty, char *mytty, uid_t myuid)
1.1 deraadt 242: {
1.14 mpech 243: char *login, *nows;
244: struct passwd *pwd;
1.1 deraadt 245: time_t now;
246: char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
247:
248: /* Determine our login name before the we reopen() stdout */
1.12 jasoni 249: if ((login = getlogin()) == NULL) {
250: if ((pwd = getpwuid(myuid)))
1.1 deraadt 251: login = pwd->pw_name;
252: else
253: login = "???";
1.12 jasoni 254: }
1.1 deraadt 255:
1.7 downsj 256: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.1 deraadt 257: if ((freopen(path, "w", stdout)) == NULL)
258: err(1, "%s", path);
259:
1.17 ! deraadt 260: /* revoke privs, now that we have opened the tty */
! 261: setegid(getgid());
! 262: setgid(getgid());
! 263:
1.1 deraadt 264: (void)signal(SIGINT, done);
265: (void)signal(SIGHUP, done);
266:
267: /* print greeting */
268: if (gethostname(host, sizeof(host)) < 0)
269: (void)strcpy(host, "???");
270: now = time((time_t *)NULL);
271: nows = ctime(&now);
272: nows[16] = '\0';
273: (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
274: login, host, mytty, nows + 11);
275:
276: while (fgets(line, sizeof(line), stdin) != NULL)
277: wr_fputs(line);
278: }
279:
280: /*
281: * done - cleanup and exit
282: */
283: void
1.11 deraadt 284: done(int sig)
1.1 deraadt 285: {
1.13 deraadt 286: (void)write(STDOUT_FILENO, "EOF\r\n", 5);
1.11 deraadt 287: if (sig)
288: _exit(0);
289: else
290: exit(0);
1.1 deraadt 291: }
292:
293: /*
294: * wr_fputs - like fputs(), but makes control characters visible and
295: * turns \n into \r\n
296: */
297: void
1.17 ! deraadt 298: wr_fputs(char *s)
1.1 deraadt 299: {
1.14 mpech 300: u_char c;
1.10 deraadt 301: char visout[5], *s2;
1.1 deraadt 302:
303: #define PUTC(c) if (putchar(c) == EOF) goto err;
304:
305: for (; *s != '\0'; ++s) {
306: c = toascii(*s);
307: if (c == '\n') {
308: PUTC('\r');
1.5 deraadt 309: PUTC('\n');
310: continue;
1.3 deraadt 311: }
1.6 deraadt 312: vis(visout, c, VIS_SAFE|VIS_NOSLASH, s[1]);
1.5 deraadt 313: for (s2 = visout; *s2; s2++)
314: PUTC(*s2);
1.1 deraadt 315: }
316: return;
317:
318: err: err(1, NULL);
319: #undef PUTC
320: }
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