Annotation of src/usr.bin/write/write.c, Revision 1.3
1.1 deraadt 1: /* $NetBSD: write.c,v 1.5 1995/08/31 21:48:32 jtc Exp $ */
2:
3: /*
4: * Copyright (c) 1989, 1993
5: * The Regents of the University of California. All rights reserved.
6: *
7: * This code is derived from software contributed to Berkeley by
8: * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
9: *
10: * Redistribution and use in source and binary forms, with or without
11: * modification, are permitted provided that the following conditions
12: * are met:
13: * 1. Redistributions of source code must retain the above copyright
14: * notice, this list of conditions and the following disclaimer.
15: * 2. Redistributions in binary form must reproduce the above copyright
16: * notice, this list of conditions and the following disclaimer in the
17: * documentation and/or other materials provided with the distribution.
18: * 3. All advertising materials mentioning features or use of this software
19: * must display the following acknowledgement:
20: * This product includes software developed by the University of
21: * California, Berkeley and its contributors.
22: * 4. Neither the name of the University nor the names of its contributors
23: * may be used to endorse or promote products derived from this software
24: * without specific prior written permission.
25: *
26: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36: * SUCH DAMAGE.
37: */
38:
39: #ifndef lint
40: static char copyright[] =
41: "@(#) Copyright (c) 1989, 1993\n\
42: The Regents of the University of California. All rights reserved.\n";
43: #endif /* not lint */
44:
45: #ifndef lint
46: #if 0
47: static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95";
48: #endif
49: static char *rcsid = "$NetBSD: write.c,v 1.5 1995/08/31 21:48:32 jtc Exp $";
50: #endif /* not lint */
51:
52: #include <sys/types.h>
53: #include <sys/param.h>
54: #include <sys/stat.h>
55: #include <ctype.h>
56: #include <stdio.h>
57: #include <string.h>
58: #include <signal.h>
59: #include <time.h>
60: #include <fcntl.h>
61: #include <pwd.h>
62: #include <unistd.h>
63: #include <utmp.h>
64: #include <err.h>
65:
66: void done();
67: void do_write __P((char *, char *, uid_t));
68: void wr_fputs __P((char *));
69: void search_utmp __P((char *, char *, char *, uid_t));
70: int term_chk __P((char *, int *, time_t *, int));
71: int utmp_chk __P((char *, char *));
72:
73: int
74: main(argc, argv)
75: int argc;
76: char **argv;
77: {
78: register char *cp;
79: time_t atime;
80: uid_t myuid;
81: int msgsok, myttyfd;
82: char tty[MAXPATHLEN], *mytty;
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");
95: if (cp = strrchr(mytty, '/'))
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:
111: if (!strncmp(argv[2], "/dev/", 5))
112: argv[2] += 5;
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: }
127: done();
128: /* NOTREACHED */
129: }
130:
131: /*
132: * utmp_chk - checks that the given user is actually logged in on
133: * the given tty
134: */
135: int
136: utmp_chk(user, tty)
137: char *user, *tty;
138: {
139: struct utmp u;
140: int ufd;
141:
142: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
143: return(0); /* ignore error, shouldn't happen anyway */
144:
145: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
146: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
147: strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
148: (void)close(ufd);
149: return(0);
150: }
151:
152: (void)close(ufd);
153: return(1);
154: }
155:
156: /*
157: * search_utmp - search utmp for the "best" terminal to write to
158: *
159: * Ignores terminals with messages disabled, and of the rest, returns
160: * the one with the most recent access time. Returns as value the number
161: * of the user's terminals with messages enabled, or -1 if the user is
162: * not logged in at all.
163: *
164: * Special case for writing to yourself - ignore the terminal you're
165: * writing from, unless that's the only terminal with messages enabled.
166: */
167: void
168: search_utmp(user, tty, mytty, myuid)
169: char *user, *tty, *mytty;
170: uid_t myuid;
171: {
172: struct utmp u;
173: time_t bestatime, atime;
174: int ufd, nloggedttys, nttys, msgsok, user_is_me;
175: char atty[UT_LINESIZE + 1];
176:
177: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
178: err(1, "%s", _PATH_UTMP);
179:
180: nloggedttys = nttys = 0;
181: bestatime = 0;
182: user_is_me = 0;
183: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
184: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
185: ++nloggedttys;
186: (void)strncpy(atty, u.ut_line, UT_LINESIZE);
187: atty[UT_LINESIZE] = '\0';
188: if (term_chk(atty, &msgsok, &atime, 0))
189: continue; /* bad term? skip */
190: if (myuid && !msgsok)
191: continue; /* skip ttys with msgs off */
192: if (strcmp(atty, mytty) == 0) {
193: user_is_me = 1;
194: continue; /* don't write to yourself */
195: }
196: ++nttys;
197: if (atime > bestatime) {
198: bestatime = atime;
199: (void)strcpy(tty, atty);
200: }
201: }
202:
203: (void)close(ufd);
204: if (nloggedttys == 0)
205: errx(1, "%s is not logged in", user);
206: if (nttys == 0) {
207: if (user_is_me) { /* ok, so write to yourself! */
208: (void)strcpy(tty, mytty);
209: return;
210: }
211: errx(1, "%s has messages disabled", user);
212: } else if (nttys > 1)
213: warnx("%s is logged in more than once; writing to %s",
214: user, tty);
215: }
216:
217: /*
218: * term_chk - check that a terminal exists, and get the message bit
219: * and the access time
220: */
221: int
222: term_chk(tty, msgsokP, atimeP, showerror)
223: char *tty;
224: int *msgsokP, showerror;
225: time_t *atimeP;
226: {
227: struct stat s;
228: char path[MAXPATHLEN];
229:
230: (void)sprintf(path, "/dev/%s", tty);
231: if (stat(path, &s) < 0) {
232: if (showerror)
233: warn("%s", path);
234: return(1);
235: }
236: *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */
237: *atimeP = s.st_atime;
238: return(0);
239: }
240:
241: /*
242: * do_write - actually make the connection
243: */
244: void
245: do_write(tty, mytty, myuid)
246: char *tty, *mytty;
247: uid_t myuid;
248: {
249: register char *login, *nows;
250: register struct passwd *pwd;
251: time_t now;
252: char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
253:
254: /* Determine our login name before the we reopen() stdout */
255: if ((login = getlogin()) == NULL)
256: if (pwd = getpwuid(myuid))
257: login = pwd->pw_name;
258: else
259: login = "???";
260:
261: (void)sprintf(path, "/dev/%s", tty);
262: if ((freopen(path, "w", stdout)) == NULL)
263: err(1, "%s", path);
264:
265: (void)signal(SIGINT, done);
266: (void)signal(SIGHUP, done);
267:
268: /* print greeting */
269: if (gethostname(host, sizeof(host)) < 0)
270: (void)strcpy(host, "???");
271: now = time((time_t *)NULL);
272: nows = ctime(&now);
273: nows[16] = '\0';
274: (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
275: login, host, mytty, nows + 11);
276:
277: while (fgets(line, sizeof(line), stdin) != NULL)
278: wr_fputs(line);
279: }
280:
281: /*
282: * done - cleanup and exit
283: */
284: void
285: done()
286: {
287: (void)printf("EOF\r\n");
288: exit(0);
289: }
290:
291: /*
292: * wr_fputs - like fputs(), but makes control characters visible and
293: * turns \n into \r\n
294: */
295: void
296: wr_fputs(s)
297: register char *s;
298: {
299: register char c;
300:
301: #define PUTC(c) if (putchar(c) == EOF) goto err;
302:
303: for (; *s != '\0'; ++s) {
304: c = toascii(*s);
305: if (c == '\n') {
306: PUTC('\r');
307: } else if (!isprint(c) && !isspace(c) && c != '\007') {
1.3 ! deraadt 308: if (c & 0x80) {
! 309: PUTC('M');
! 310: PUTC('-');
! 311: c &= ~0x80;
! 312: } else {
! 313: PUTC('^');
! 314: c &= ~0x40;
! 315: }
! 316: }
! 317: PUTC(c);
1.1 deraadt 318: }
319: return;
320:
321: err: err(1, NULL);
322: #undef PUTC
323: }
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