Annotation of src/usr.bin/write/write.c, Revision 1.18
1.18 ! deraadt 1: /* $OpenBSD: write.c,v 1.17 2002/08/04 01:26:40 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.
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
1.18 ! deraadt 50: static char *rcsid = "$OpenBSD: write.c,v 1.17 2002/08/04 01:26:40 deraadt Exp $";
1.1 deraadt 51: #endif /* not lint */
52:
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>
1.7 downsj 61: #include <paths.h>
1.1 deraadt 62: #include <pwd.h>
63: #include <unistd.h>
64: #include <utmp.h>
65: #include <err.h>
1.5 deraadt 66: #include <vis.h>
1.1 deraadt 67:
1.15 millert 68: void done(int sig);
69: void do_write(char *, char *, uid_t);
70: void wr_fputs(char *);
71: void search_utmp(char *, char *, char *, uid_t);
72: int term_chk(char *, int *, time_t *, int);
73: int utmp_chk(char *, char *);
1.1 deraadt 74:
75: int
1.17 deraadt 76: main(int argc, char **argv)
1.1 deraadt 77: {
1.17 deraadt 78: char tty[MAXPATHLEN], *mytty, *cp;
79: int msgsok, myttyfd;
1.1 deraadt 80: time_t atime;
81: uid_t myuid;
82:
83: /* check that sender has write enabled */
84: if (isatty(fileno(stdin)))
85: myttyfd = fileno(stdin);
86: else if (isatty(fileno(stdout)))
87: myttyfd = fileno(stdout);
88: else if (isatty(fileno(stderr)))
89: myttyfd = fileno(stderr);
90: else
91: errx(1, "can't find your tty");
92: if (!(mytty = ttyname(myttyfd)))
93: errx(1, "can't find your tty's name");
1.12 jasoni 94: if ((cp = strrchr(mytty, '/')))
1.1 deraadt 95: mytty = cp + 1;
96: if (term_chk(mytty, &msgsok, &atime, 1))
97: exit(1);
98: if (!msgsok)
1.2 deraadt 99: warnx("you have write permission turned off");
1.1 deraadt 100:
101: myuid = getuid();
102:
103: /* check args */
104: switch (argc) {
105: case 2:
106: search_utmp(argv[1], tty, mytty, myuid);
107: do_write(tty, mytty, myuid);
108: break;
109: case 3:
1.16 fgsch 110: if (!strncmp(argv[2], _PATH_DEV, sizeof(_PATH_DEV) - 1))
111: argv[2] += sizeof(_PATH_DEV) - 1;
1.1 deraadt 112: if (utmp_chk(argv[1], argv[2]))
113: errx(1, "%s is not logged in on %s",
114: argv[1], argv[2]);
115: if (term_chk(argv[2], &msgsok, &atime, 1))
116: exit(1);
117: if (myuid && !msgsok)
118: errx(1, "%s has messages disabled on %s",
119: argv[1], argv[2]);
120: do_write(argv[2], mytty, myuid);
121: break;
122: default:
123: (void)fprintf(stderr, "usage: write user [tty]\n");
124: exit(1);
125: }
1.11 deraadt 126: done(0);
1.12 jasoni 127:
1.1 deraadt 128: /* NOTREACHED */
1.12 jasoni 129: return (0);
1.1 deraadt 130: }
131:
132: /*
133: * utmp_chk - checks that the given user is actually logged in on
134: * the given tty
135: */
136: int
1.17 deraadt 137: utmp_chk(char *user, char *tty)
1.1 deraadt 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
1.17 deraadt 168: search_utmp(char *user, char *tty, char *mytty, uid_t myuid)
1.1 deraadt 169: {
170: struct utmp u;
171: time_t bestatime, atime;
172: int ufd, nloggedttys, nttys, msgsok, user_is_me;
173: char atty[UT_LINESIZE + 1];
174:
175: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
176: err(1, "%s", _PATH_UTMP);
177:
178: nloggedttys = nttys = 0;
179: bestatime = 0;
180: user_is_me = 0;
181: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
182: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
183: ++nloggedttys;
184: (void)strncpy(atty, u.ut_line, UT_LINESIZE);
185: atty[UT_LINESIZE] = '\0';
186: if (term_chk(atty, &msgsok, &atime, 0))
187: continue; /* bad term? skip */
188: if (myuid && !msgsok)
189: continue; /* skip ttys with msgs off */
190: if (strcmp(atty, mytty) == 0) {
191: user_is_me = 1;
192: continue; /* don't write to yourself */
193: }
194: ++nttys;
195: if (atime > bestatime) {
196: bestatime = atime;
197: (void)strcpy(tty, atty);
198: }
199: }
200:
201: (void)close(ufd);
202: if (nloggedttys == 0)
203: errx(1, "%s is not logged in", user);
204: if (nttys == 0) {
205: if (user_is_me) { /* ok, so write to yourself! */
206: (void)strcpy(tty, mytty);
207: return;
208: }
209: errx(1, "%s has messages disabled", user);
210: } else if (nttys > 1)
211: warnx("%s is logged in more than once; writing to %s",
212: user, tty);
213: }
214:
215: /*
216: * term_chk - check that a terminal exists, and get the message bit
217: * and the access time
218: */
219: int
1.17 deraadt 220: term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
1.1 deraadt 221: {
222: struct stat s;
223: char path[MAXPATHLEN];
224:
1.7 downsj 225: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.1 deraadt 226: if (stat(path, &s) < 0) {
227: if (showerror)
228: warn("%s", path);
229: return(1);
230: }
1.9 deraadt 231: *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */
1.1 deraadt 232: *atimeP = s.st_atime;
233: return(0);
234: }
235:
236: /*
237: * do_write - actually make the connection
238: */
239: void
1.17 deraadt 240: do_write(char *tty, char *mytty, uid_t myuid)
1.1 deraadt 241: {
1.14 mpech 242: char *login, *nows;
243: struct passwd *pwd;
1.1 deraadt 244: time_t now;
245: char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
246:
247: /* Determine our login name before the we reopen() stdout */
1.12 jasoni 248: if ((login = getlogin()) == NULL) {
249: if ((pwd = getpwuid(myuid)))
1.1 deraadt 250: login = pwd->pw_name;
251: else
252: login = "???";
1.12 jasoni 253: }
1.1 deraadt 254:
1.7 downsj 255: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.1 deraadt 256: if ((freopen(path, "w", stdout)) == NULL)
257: err(1, "%s", path);
258:
1.17 deraadt 259: /* revoke privs, now that we have opened the tty */
260: setegid(getgid());
261: setgid(getgid());
262:
1.1 deraadt 263: (void)signal(SIGINT, done);
264: (void)signal(SIGHUP, done);
265:
266: /* print greeting */
267: if (gethostname(host, sizeof(host)) < 0)
268: (void)strcpy(host, "???");
269: now = time((time_t *)NULL);
270: nows = ctime(&now);
271: nows[16] = '\0';
272: (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
273: login, host, mytty, nows + 11);
274:
275: while (fgets(line, sizeof(line), stdin) != NULL)
276: wr_fputs(line);
277: }
278:
279: /*
280: * done - cleanup and exit
281: */
282: void
1.11 deraadt 283: done(int sig)
1.1 deraadt 284: {
1.13 deraadt 285: (void)write(STDOUT_FILENO, "EOF\r\n", 5);
1.11 deraadt 286: if (sig)
287: _exit(0);
288: else
289: exit(0);
1.1 deraadt 290: }
291:
292: /*
293: * wr_fputs - like fputs(), but makes control characters visible and
294: * turns \n into \r\n
295: */
296: void
1.17 deraadt 297: wr_fputs(char *s)
1.1 deraadt 298: {
1.14 mpech 299: u_char c;
1.10 deraadt 300: char visout[5], *s2;
1.1 deraadt 301:
302: #define PUTC(c) if (putchar(c) == EOF) goto err;
303:
304: for (; *s != '\0'; ++s) {
305: c = toascii(*s);
306: if (c == '\n') {
307: PUTC('\r');
1.5 deraadt 308: PUTC('\n');
309: continue;
1.3 deraadt 310: }
1.6 deraadt 311: vis(visout, c, VIS_SAFE|VIS_NOSLASH, s[1]);
1.5 deraadt 312: for (s2 = visout; *s2; s2++)
313: PUTC(*s2);
1.1 deraadt 314: }
315: return;
316:
317: err: err(1, NULL);
318: #undef PUTC
319: }
![[BACK]](/icons/back.gif){kind=icon}
Return to write.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / write