Annotation of src/usr.bin/write/write.c, Revision 1.16
1.16 ! fgsch 1: /* $OpenBSD: write.c,v 1.15 2002/02/16 21:27:59 millert 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
1.16 ! fgsch 50: static char *rcsid = "$OpenBSD: write.c,v 1.15 2002/02/16 21:27:59 millert 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
77: main(argc, argv)
78: int argc;
79: char **argv;
80: {
1.14 mpech 81: char *cp;
1.1 deraadt 82: time_t atime;
83: uid_t myuid;
84: int msgsok, myttyfd;
85: char tty[MAXPATHLEN], *mytty;
86:
87: /* check that sender has write enabled */
88: if (isatty(fileno(stdin)))
89: myttyfd = fileno(stdin);
90: else if (isatty(fileno(stdout)))
91: myttyfd = fileno(stdout);
92: else if (isatty(fileno(stderr)))
93: myttyfd = fileno(stderr);
94: else
95: errx(1, "can't find your tty");
96: if (!(mytty = ttyname(myttyfd)))
97: errx(1, "can't find your tty's name");
1.12 jasoni 98: if ((cp = strrchr(mytty, '/')))
1.1 deraadt 99: mytty = cp + 1;
100: if (term_chk(mytty, &msgsok, &atime, 1))
101: exit(1);
102: if (!msgsok)
1.2 deraadt 103: warnx("you have write permission turned off");
1.1 deraadt 104:
105: myuid = getuid();
106:
107: /* check args */
108: switch (argc) {
109: case 2:
110: search_utmp(argv[1], tty, mytty, myuid);
111: do_write(tty, mytty, myuid);
112: break;
113: case 3:
1.16 ! fgsch 114: if (!strncmp(argv[2], _PATH_DEV, sizeof(_PATH_DEV) - 1))
! 115: argv[2] += sizeof(_PATH_DEV) - 1;
1.1 deraadt 116: if (utmp_chk(argv[1], argv[2]))
117: errx(1, "%s is not logged in on %s",
118: argv[1], argv[2]);
119: if (term_chk(argv[2], &msgsok, &atime, 1))
120: exit(1);
121: if (myuid && !msgsok)
122: errx(1, "%s has messages disabled on %s",
123: argv[1], argv[2]);
124: do_write(argv[2], mytty, myuid);
125: break;
126: default:
127: (void)fprintf(stderr, "usage: write user [tty]\n");
128: exit(1);
129: }
1.11 deraadt 130: done(0);
1.12 jasoni 131:
1.1 deraadt 132: /* NOTREACHED */
1.12 jasoni 133: return (0);
1.1 deraadt 134: }
135:
136: /*
137: * utmp_chk - checks that the given user is actually logged in on
138: * the given tty
139: */
140: int
141: utmp_chk(user, tty)
142: char *user, *tty;
143: {
144: struct utmp u;
145: int ufd;
146:
147: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
148: return(0); /* ignore error, shouldn't happen anyway */
149:
150: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
151: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
152: strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
153: (void)close(ufd);
154: return(0);
155: }
156:
157: (void)close(ufd);
158: return(1);
159: }
160:
161: /*
162: * search_utmp - search utmp for the "best" terminal to write to
163: *
164: * Ignores terminals with messages disabled, and of the rest, returns
165: * the one with the most recent access time. Returns as value the number
166: * of the user's terminals with messages enabled, or -1 if the user is
167: * not logged in at all.
168: *
169: * Special case for writing to yourself - ignore the terminal you're
170: * writing from, unless that's the only terminal with messages enabled.
171: */
172: void
173: search_utmp(user, tty, mytty, myuid)
174: char *user, *tty, *mytty;
175: uid_t myuid;
176: {
177: struct utmp u;
178: time_t bestatime, atime;
179: int ufd, nloggedttys, nttys, msgsok, user_is_me;
180: char atty[UT_LINESIZE + 1];
181:
182: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
183: err(1, "%s", _PATH_UTMP);
184:
185: nloggedttys = nttys = 0;
186: bestatime = 0;
187: user_is_me = 0;
188: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
189: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
190: ++nloggedttys;
191: (void)strncpy(atty, u.ut_line, UT_LINESIZE);
192: atty[UT_LINESIZE] = '\0';
193: if (term_chk(atty, &msgsok, &atime, 0))
194: continue; /* bad term? skip */
195: if (myuid && !msgsok)
196: continue; /* skip ttys with msgs off */
197: if (strcmp(atty, mytty) == 0) {
198: user_is_me = 1;
199: continue; /* don't write to yourself */
200: }
201: ++nttys;
202: if (atime > bestatime) {
203: bestatime = atime;
204: (void)strcpy(tty, atty);
205: }
206: }
207:
208: (void)close(ufd);
209: if (nloggedttys == 0)
210: errx(1, "%s is not logged in", user);
211: if (nttys == 0) {
212: if (user_is_me) { /* ok, so write to yourself! */
213: (void)strcpy(tty, mytty);
214: return;
215: }
216: errx(1, "%s has messages disabled", user);
217: } else if (nttys > 1)
218: warnx("%s is logged in more than once; writing to %s",
219: user, tty);
220: }
221:
222: /*
223: * term_chk - check that a terminal exists, and get the message bit
224: * and the access time
225: */
226: int
227: term_chk(tty, msgsokP, atimeP, showerror)
228: char *tty;
229: int *msgsokP, showerror;
230: time_t *atimeP;
231: {
232: struct stat s;
233: char path[MAXPATHLEN];
234:
1.7 downsj 235: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.1 deraadt 236: if (stat(path, &s) < 0) {
237: if (showerror)
238: warn("%s", path);
239: return(1);
240: }
1.9 deraadt 241: *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */
1.1 deraadt 242: *atimeP = s.st_atime;
243: return(0);
244: }
245:
246: /*
247: * do_write - actually make the connection
248: */
249: void
250: do_write(tty, mytty, myuid)
251: char *tty, *mytty;
252: uid_t myuid;
253: {
1.14 mpech 254: char *login, *nows;
255: struct passwd *pwd;
1.1 deraadt 256: time_t now;
257: char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
258:
259: /* Determine our login name before the we reopen() stdout */
1.12 jasoni 260: if ((login = getlogin()) == NULL) {
261: if ((pwd = getpwuid(myuid)))
1.1 deraadt 262: login = pwd->pw_name;
263: else
264: login = "???";
1.12 jasoni 265: }
1.1 deraadt 266:
1.7 downsj 267: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.1 deraadt 268: if ((freopen(path, "w", stdout)) == NULL)
269: err(1, "%s", path);
270:
271: (void)signal(SIGINT, done);
272: (void)signal(SIGHUP, done);
273:
274: /* print greeting */
275: if (gethostname(host, sizeof(host)) < 0)
276: (void)strcpy(host, "???");
277: now = time((time_t *)NULL);
278: nows = ctime(&now);
279: nows[16] = '\0';
280: (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
281: login, host, mytty, nows + 11);
282:
283: while (fgets(line, sizeof(line), stdin) != NULL)
284: wr_fputs(line);
285: }
286:
287: /*
288: * done - cleanup and exit
289: */
290: void
1.11 deraadt 291: done(int sig)
1.1 deraadt 292: {
1.13 deraadt 293: (void)write(STDOUT_FILENO, "EOF\r\n", 5);
1.11 deraadt 294: if (sig)
295: _exit(0);
296: else
297: exit(0);
1.1 deraadt 298: }
299:
300: /*
301: * wr_fputs - like fputs(), but makes control characters visible and
302: * turns \n into \r\n
303: */
304: void
305: wr_fputs(s)
1.14 mpech 306: char *s;
1.1 deraadt 307: {
1.14 mpech 308: u_char c;
1.10 deraadt 309: char visout[5], *s2;
1.1 deraadt 310:
311: #define PUTC(c) if (putchar(c) == EOF) goto err;
312:
313: for (; *s != '\0'; ++s) {
314: c = toascii(*s);
315: if (c == '\n') {
316: PUTC('\r');
1.5 deraadt 317: PUTC('\n');
318: continue;
1.3 deraadt 319: }
1.6 deraadt 320: vis(visout, c, VIS_SAFE|VIS_NOSLASH, s[1]);
1.5 deraadt 321: for (s2 = visout; *s2; s2++)
322: PUTC(*s2);
1.1 deraadt 323: }
324: return;
325:
326: err: err(1, NULL);
327: #undef PUTC
328: }