Annotation of src/usr.bin/write/write.c, Revision 1.23
1.23 ! djm 1: /* $OpenBSD: write.c,v 1.22 2003/07/10 00:06:52 david 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: #ifndef lint
37: static char copyright[] =
38: "@(#) Copyright (c) 1989, 1993\n\
39: The Regents of the University of California. All rights reserved.\n";
40: #endif /* not lint */
41:
42: #ifndef lint
43: #if 0
44: static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95";
45: #endif
1.23 ! djm 46: static char *rcsid = "$OpenBSD: write.c,v 1.22 2003/07/10 00:06:52 david Exp $";
1.1 deraadt 47: #endif /* not lint */
48:
49: #include <sys/param.h>
50: #include <sys/stat.h>
51: #include <ctype.h>
52: #include <stdio.h>
1.22 david 53: #include <stdlib.h>
1.1 deraadt 54: #include <string.h>
55: #include <signal.h>
56: #include <time.h>
57: #include <fcntl.h>
1.7 downsj 58: #include <paths.h>
1.1 deraadt 59: #include <pwd.h>
60: #include <unistd.h>
61: #include <utmp.h>
62: #include <err.h>
1.5 deraadt 63: #include <vis.h>
1.1 deraadt 64:
1.15 millert 65: void done(int sig);
66: void do_write(char *, char *, uid_t);
67: void wr_fputs(char *);
1.19 deraadt 68: void search_utmp(char *, char *, int, char *, uid_t);
1.15 millert 69: int term_chk(char *, int *, time_t *, int);
70: int utmp_chk(char *, char *);
1.1 deraadt 71:
72: int
1.21 deraadt 73: main(int argc, char *argv[])
1.1 deraadt 74: {
1.17 deraadt 75: char tty[MAXPATHLEN], *mytty, *cp;
76: int msgsok, myttyfd;
1.1 deraadt 77: time_t atime;
78: uid_t myuid;
79:
80: /* check that sender has write enabled */
81: if (isatty(fileno(stdin)))
82: myttyfd = fileno(stdin);
83: else if (isatty(fileno(stdout)))
84: myttyfd = fileno(stdout);
85: else if (isatty(fileno(stderr)))
86: myttyfd = fileno(stderr);
87: else
88: errx(1, "can't find your tty");
89: if (!(mytty = ttyname(myttyfd)))
90: errx(1, "can't find your tty's name");
1.12 jasoni 91: if ((cp = strrchr(mytty, '/')))
1.1 deraadt 92: mytty = cp + 1;
93: if (term_chk(mytty, &msgsok, &atime, 1))
94: exit(1);
95: if (!msgsok)
1.2 deraadt 96: warnx("you have write permission turned off");
1.1 deraadt 97:
98: myuid = getuid();
99:
100: /* check args */
101: switch (argc) {
102: case 2:
1.19 deraadt 103: search_utmp(argv[1], tty, sizeof tty, mytty, myuid);
1.1 deraadt 104: do_write(tty, mytty, myuid);
105: break;
106: case 3:
1.16 fgsch 107: if (!strncmp(argv[2], _PATH_DEV, sizeof(_PATH_DEV) - 1))
108: argv[2] += sizeof(_PATH_DEV) - 1;
1.1 deraadt 109: if (utmp_chk(argv[1], argv[2]))
110: errx(1, "%s is not logged in on %s",
111: argv[1], argv[2]);
112: if (term_chk(argv[2], &msgsok, &atime, 1))
113: exit(1);
114: if (myuid && !msgsok)
115: errx(1, "%s has messages disabled on %s",
116: argv[1], argv[2]);
117: do_write(argv[2], mytty, myuid);
118: break;
119: default:
120: (void)fprintf(stderr, "usage: write user [tty]\n");
121: exit(1);
122: }
1.11 deraadt 123: done(0);
1.12 jasoni 124:
1.1 deraadt 125: /* NOTREACHED */
1.12 jasoni 126: return (0);
1.1 deraadt 127: }
128:
129: /*
130: * utmp_chk - checks that the given user is actually logged in on
131: * the given tty
132: */
133: int
1.17 deraadt 134: utmp_chk(char *user, char *tty)
1.1 deraadt 135: {
136: struct utmp u;
137: int ufd;
138:
139: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
140: return(0); /* ignore error, shouldn't happen anyway */
141:
142: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
143: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
144: strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
145: (void)close(ufd);
146: return(0);
147: }
148:
149: (void)close(ufd);
150: return(1);
151: }
152:
153: /*
154: * search_utmp - search utmp for the "best" terminal to write to
155: *
156: * Ignores terminals with messages disabled, and of the rest, returns
157: * the one with the most recent access time. Returns as value the number
158: * of the user's terminals with messages enabled, or -1 if the user is
159: * not logged in at all.
160: *
161: * Special case for writing to yourself - ignore the terminal you're
162: * writing from, unless that's the only terminal with messages enabled.
163: */
164: void
1.19 deraadt 165: search_utmp(char *user, char *tty, int ttyl, char *mytty, uid_t myuid)
1.1 deraadt 166: {
167: struct utmp u;
168: time_t bestatime, atime;
169: int ufd, nloggedttys, nttys, msgsok, user_is_me;
170: char atty[UT_LINESIZE + 1];
171:
172: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
173: err(1, "%s", _PATH_UTMP);
174:
175: nloggedttys = nttys = 0;
176: bestatime = 0;
177: user_is_me = 0;
178: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
179: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
180: ++nloggedttys;
181: (void)strncpy(atty, u.ut_line, UT_LINESIZE);
182: atty[UT_LINESIZE] = '\0';
183: if (term_chk(atty, &msgsok, &atime, 0))
184: continue; /* bad term? skip */
185: if (myuid && !msgsok)
186: continue; /* skip ttys with msgs off */
187: if (strcmp(atty, mytty) == 0) {
188: user_is_me = 1;
189: continue; /* don't write to yourself */
190: }
191: ++nttys;
192: if (atime > bestatime) {
193: bestatime = atime;
1.19 deraadt 194: (void)strlcpy(tty, atty, ttyl);
1.1 deraadt 195: }
196: }
197:
198: (void)close(ufd);
199: if (nloggedttys == 0)
200: errx(1, "%s is not logged in", user);
201: if (nttys == 0) {
202: if (user_is_me) { /* ok, so write to yourself! */
1.19 deraadt 203: (void)strlcpy(tty, mytty, ttyl);
1.1 deraadt 204: return;
205: }
206: errx(1, "%s has messages disabled", user);
207: } else if (nttys > 1)
208: warnx("%s is logged in more than once; writing to %s",
209: user, tty);
210: }
211:
212: /*
213: * term_chk - check that a terminal exists, and get the message bit
214: * and the access time
215: */
216: int
1.17 deraadt 217: term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
1.1 deraadt 218: {
219: struct stat s;
220: char path[MAXPATHLEN];
221:
1.7 downsj 222: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.1 deraadt 223: if (stat(path, &s) < 0) {
224: if (showerror)
225: warn("%s", path);
226: return(1);
227: }
1.9 deraadt 228: *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */
1.1 deraadt 229: *atimeP = s.st_atime;
230: return(0);
231: }
232:
233: /*
234: * do_write - actually make the connection
235: */
236: void
1.17 deraadt 237: do_write(char *tty, char *mytty, uid_t myuid)
1.1 deraadt 238: {
1.14 mpech 239: char *login, *nows;
240: struct passwd *pwd;
1.1 deraadt 241: time_t now;
242: char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
1.23 ! djm 243: gid_t gid;
1.1 deraadt 244:
245: /* Determine our login name before the we reopen() stdout */
1.12 jasoni 246: if ((login = getlogin()) == NULL) {
247: if ((pwd = getpwuid(myuid)))
1.1 deraadt 248: login = pwd->pw_name;
249: else
250: login = "???";
1.12 jasoni 251: }
1.1 deraadt 252:
1.7 downsj 253: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.1 deraadt 254: if ((freopen(path, "w", stdout)) == NULL)
255: err(1, "%s", path);
256:
1.17 deraadt 257: /* revoke privs, now that we have opened the tty */
1.23 ! djm 258: gid = getgid();
! 259: if (setresgid(gid, gid, gid) == -1)
! 260: err(1, "setresgid");
1.17 deraadt 261:
1.1 deraadt 262: (void)signal(SIGINT, done);
263: (void)signal(SIGHUP, done);
264:
265: /* print greeting */
266: if (gethostname(host, sizeof(host)) < 0)
1.19 deraadt 267: (void)strlcpy(host, "???", sizeof host);
1.1 deraadt 268: now = time((time_t *)NULL);
269: nows = ctime(&now);
270: nows[16] = '\0';
271: (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
272: login, host, mytty, nows + 11);
273:
274: while (fgets(line, sizeof(line), stdin) != NULL)
275: wr_fputs(line);
276: }
277:
278: /*
279: * done - cleanup and exit
280: */
281: void
1.11 deraadt 282: done(int sig)
1.1 deraadt 283: {
1.13 deraadt 284: (void)write(STDOUT_FILENO, "EOF\r\n", 5);
1.11 deraadt 285: if (sig)
286: _exit(0);
287: else
288: exit(0);
1.1 deraadt 289: }
290:
291: /*
292: * wr_fputs - like fputs(), but makes control characters visible and
293: * turns \n into \r\n
294: */
295: void
1.17 deraadt 296: wr_fputs(char *s)
1.1 deraadt 297: {
1.14 mpech 298: u_char c;
1.10 deraadt 299: char visout[5], *s2;
1.1 deraadt 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');
1.5 deraadt 307: PUTC('\n');
308: continue;
1.3 deraadt 309: }
1.6 deraadt 310: vis(visout, c, VIS_SAFE|VIS_NOSLASH, s[1]);
1.5 deraadt 311: for (s2 = visout; *s2; s2++)
312: PUTC(*s2);
1.1 deraadt 313: }
314: return;
315:
316: err: err(1, NULL);
317: #undef PUTC
318: }
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