Annotation of src/usr.bin/write/write.c, Revision 1.32
1.32 ! bluhm 1: /* $OpenBSD: write.c,v 1.31 2015/10/09 01:37:09 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.
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: #include <sys/stat.h>
37: #include <ctype.h>
38: #include <stdio.h>
1.22 david 39: #include <stdlib.h>
1.1 deraadt 40: #include <string.h>
41: #include <signal.h>
42: #include <time.h>
43: #include <fcntl.h>
1.7 downsj 44: #include <paths.h>
1.1 deraadt 45: #include <pwd.h>
46: #include <unistd.h>
1.28 deraadt 47: #include <limits.h>
1.1 deraadt 48: #include <utmp.h>
49: #include <err.h>
1.5 deraadt 50: #include <vis.h>
1.1 deraadt 51:
1.15 millert 52: void done(int sig);
53: void do_write(char *, char *, uid_t);
54: void wr_fputs(char *);
1.19 deraadt 55: void search_utmp(char *, char *, int, char *, uid_t);
1.15 millert 56: int term_chk(char *, int *, time_t *, int);
57: int utmp_chk(char *, char *);
1.1 deraadt 58:
59: int
1.21 deraadt 60: main(int argc, char *argv[])
1.1 deraadt 61: {
1.28 deraadt 62: char tty[PATH_MAX], *mytty, *cp;
1.17 deraadt 63: int msgsok, myttyfd;
1.1 deraadt 64: time_t atime;
65: uid_t myuid;
66:
67: /* check that sender has write enabled */
68: if (isatty(fileno(stdin)))
69: myttyfd = fileno(stdin);
70: else if (isatty(fileno(stdout)))
71: myttyfd = fileno(stdout);
72: else if (isatty(fileno(stderr)))
73: myttyfd = fileno(stderr);
74: else
75: errx(1, "can't find your tty");
76: if (!(mytty = ttyname(myttyfd)))
77: errx(1, "can't find your tty's name");
1.12 jasoni 78: if ((cp = strrchr(mytty, '/')))
1.1 deraadt 79: mytty = cp + 1;
80: if (term_chk(mytty, &msgsok, &atime, 1))
81: exit(1);
82: if (!msgsok)
1.2 deraadt 83: warnx("you have write permission turned off");
1.1 deraadt 84:
85: myuid = getuid();
86:
87: /* check args */
88: switch (argc) {
89: case 2:
1.19 deraadt 90: search_utmp(argv[1], tty, sizeof tty, mytty, myuid);
1.1 deraadt 91: do_write(tty, mytty, myuid);
92: break;
93: case 3:
1.16 fgsch 94: if (!strncmp(argv[2], _PATH_DEV, sizeof(_PATH_DEV) - 1))
95: argv[2] += sizeof(_PATH_DEV) - 1;
1.1 deraadt 96: if (utmp_chk(argv[1], argv[2]))
97: errx(1, "%s is not logged in on %s",
98: argv[1], argv[2]);
99: if (term_chk(argv[2], &msgsok, &atime, 1))
100: exit(1);
101: if (myuid && !msgsok)
102: errx(1, "%s has messages disabled on %s",
103: argv[1], argv[2]);
104: do_write(argv[2], mytty, myuid);
105: break;
106: default:
1.25 sobrado 107: (void)fprintf(stderr, "usage: write user [ttyname]\n");
1.1 deraadt 108: exit(1);
109: }
1.11 deraadt 110: done(0);
1.12 jasoni 111:
1.1 deraadt 112: /* NOTREACHED */
1.12 jasoni 113: return (0);
1.1 deraadt 114: }
115:
116: /*
117: * utmp_chk - checks that the given user is actually logged in on
118: * the given tty
119: */
120: int
1.17 deraadt 121: utmp_chk(char *user, char *tty)
1.1 deraadt 122: {
123: struct utmp u;
124: int ufd;
125:
126: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
1.24 deraadt 127: return(1); /* no utmp, cannot talk to users */
1.1 deraadt 128:
129: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
130: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
131: strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
132: (void)close(ufd);
133: return(0);
134: }
135:
136: (void)close(ufd);
137: return(1);
138: }
139:
140: /*
141: * search_utmp - search utmp for the "best" terminal to write to
142: *
143: * Ignores terminals with messages disabled, and of the rest, returns
144: * the one with the most recent access time. Returns as value the number
145: * of the user's terminals with messages enabled, or -1 if the user is
146: * not logged in at all.
147: *
148: * Special case for writing to yourself - ignore the terminal you're
149: * writing from, unless that's the only terminal with messages enabled.
150: */
151: void
1.19 deraadt 152: search_utmp(char *user, char *tty, int ttyl, char *mytty, uid_t myuid)
1.1 deraadt 153: {
154: struct utmp u;
155: time_t bestatime, atime;
156: int ufd, nloggedttys, nttys, msgsok, user_is_me;
157: char atty[UT_LINESIZE + 1];
158:
159: if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
160: err(1, "%s", _PATH_UTMP);
161:
162: nloggedttys = nttys = 0;
163: bestatime = 0;
164: user_is_me = 0;
165: while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
166: if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
167: ++nloggedttys;
168: (void)strncpy(atty, u.ut_line, UT_LINESIZE);
169: atty[UT_LINESIZE] = '\0';
170: if (term_chk(atty, &msgsok, &atime, 0))
171: continue; /* bad term? skip */
172: if (myuid && !msgsok)
173: continue; /* skip ttys with msgs off */
174: if (strcmp(atty, mytty) == 0) {
175: user_is_me = 1;
176: continue; /* don't write to yourself */
177: }
178: ++nttys;
179: if (atime > bestatime) {
180: bestatime = atime;
1.19 deraadt 181: (void)strlcpy(tty, atty, ttyl);
1.1 deraadt 182: }
183: }
184:
185: (void)close(ufd);
186: if (nloggedttys == 0)
187: errx(1, "%s is not logged in", user);
188: if (nttys == 0) {
189: if (user_is_me) { /* ok, so write to yourself! */
1.19 deraadt 190: (void)strlcpy(tty, mytty, ttyl);
1.1 deraadt 191: return;
192: }
193: errx(1, "%s has messages disabled", user);
194: } else if (nttys > 1)
195: warnx("%s is logged in more than once; writing to %s",
196: user, tty);
197: }
198:
199: /*
200: * term_chk - check that a terminal exists, and get the message bit
201: * and the access time
202: */
203: int
1.17 deraadt 204: term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
1.1 deraadt 205: {
206: struct stat s;
1.28 deraadt 207: char path[PATH_MAX];
1.1 deraadt 208:
1.7 downsj 209: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.1 deraadt 210: if (stat(path, &s) < 0) {
211: if (showerror)
212: warn("%s", path);
213: return(1);
214: }
1.9 deraadt 215: *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */
1.1 deraadt 216: *atimeP = s.st_atime;
217: return(0);
218: }
219:
220: /*
221: * do_write - actually make the connection
222: */
223: void
1.17 deraadt 224: do_write(char *tty, char *mytty, uid_t myuid)
1.1 deraadt 225: {
1.14 mpech 226: char *login, *nows;
227: struct passwd *pwd;
1.1 deraadt 228: time_t now;
1.28 deraadt 229: char path[PATH_MAX], host[HOST_NAME_MAX+1], line[512];
1.23 djm 230: gid_t gid;
1.32 ! bluhm 231: int fd;
1.1 deraadt 232:
233: /* Determine our login name before the we reopen() stdout */
1.12 jasoni 234: if ((login = getlogin()) == NULL) {
235: if ((pwd = getpwuid(myuid)))
1.1 deraadt 236: login = pwd->pw_name;
237: else
238: login = "???";
1.12 jasoni 239: }
1.1 deraadt 240:
1.7 downsj 241: (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
1.32 ! bluhm 242: fd = open(path, O_WRONLY, 0666);
! 243: if (fd == -1)
! 244: err(1, "open %s", path);
! 245: fflush(stdout);
! 246: if (dup2(fd, STDOUT_FILENO) == -1)
! 247: err(1, "dup2 %s", path);
! 248: if (fd != STDOUT_FILENO)
! 249: close(fd);
1.1 deraadt 250:
1.17 deraadt 251: /* revoke privs, now that we have opened the tty */
1.23 djm 252: gid = getgid();
253: if (setresgid(gid, gid, gid) == -1)
254: err(1, "setresgid");
1.30 deraadt 255:
256: /*
257: * Unfortunately this is rather late - well after utmp
258: * parsing, then pinned by the tty open and setresgid
259: */
1.31 deraadt 260: if (pledge("stdio", NULL) == -1)
261: err(1, "pledge");
1.17 deraadt 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)
1.19 deraadt 268: (void)strlcpy(host, "???", sizeof host);
1.27 deraadt 269: now = time(NULL);
1.1 deraadt 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