write.c revision 1.21
1 /* $NetBSD: write.c,v 1.21 2002/08/16 20:21:49 itojun 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 #include <sys/cdefs.h> 40 #ifndef lint 41 __COPYRIGHT("@(#) 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 #else 49 __RCSID("$NetBSD: write.c,v 1.21 2002/08/16 20:21:49 itojun Exp $"); 50 #endif 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 <stdlib.h> 59 #include <string.h> 60 #include <signal.h> 61 #include <time.h> 62 #include <fcntl.h> 63 #include <paths.h> 64 #include <pwd.h> 65 #include <unistd.h> 66 #include <err.h> 67 #include <errno.h> 68 69 #include "utmpentry.h" 70 71 void done(int); 72 void do_write(int, const char *, const uid_t); 73 void wr_fputs(char *); 74 int search_utmp(char *, char *, uid_t); 75 int term_chk(uid_t, const char *, int *, time_t *, int); 76 int utmp_chk(const char *, const char *); 77 int main(int, char **); 78 79 static gid_t saved_egid; 80 81 int 82 main(int argc, char **argv) 83 { 84 char *cp; 85 time_t atime; 86 uid_t myuid, uid; 87 int msgsok, myttyfd, ttyfd; 88 char *mytty; 89 90 saved_egid = getegid(); 91 if (setegid(getgid()) == -1) 92 err(1, "setegid"); 93 myuid = getuid(); 94 ttyfd = -1; 95 96 /* check that sender has write enabled */ 97 if (isatty(fileno(stdin))) 98 myttyfd = fileno(stdin); 99 else if (isatty(fileno(stdout))) 100 myttyfd = fileno(stdout); 101 else if (isatty(fileno(stderr))) 102 myttyfd = fileno(stderr); 103 else 104 errx(1, "can't find your tty"); 105 if (!(mytty = ttyname(myttyfd))) 106 errx(1, "can't find your tty's name"); 107 if ((cp = strrchr(mytty, '/')) != NULL) 108 mytty = cp + 1; 109 if (term_chk(myuid, mytty, &msgsok, &atime, 1) == -1) 110 err(1, "%s%s", _PATH_DEV, mytty); 111 if (!msgsok) { 112 (void)fprintf(stderr, 113 "warning: you have write permission turned off; " 114 "no reply possible\n"); 115 } 116 117 /* check args */ 118 switch (argc) { 119 case 2: 120 ttyfd = search_utmp(argv[1], mytty, myuid); 121 break; 122 case 3: 123 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV))) 124 argv[2] += strlen(_PATH_DEV); 125 if (uid_from_user(argv[1], &uid) == -1) 126 errx(1, "%s: unknown user", argv[1]); 127 if (utmp_chk(argv[1], argv[2])) 128 errx(1, "%s is not logged in on %s", 129 argv[1], argv[2]); 130 ttyfd = term_chk(uid, argv[2], &msgsok, &atime, 0); 131 if (ttyfd == -1) 132 err(1, "%s%s", _PATH_DEV, argv[2]); 133 if (myuid && !msgsok) 134 errx(1, "%s has messages disabled on %s", 135 argv[1], argv[2]); 136 break; 137 default: 138 (void)fprintf(stderr, "usage: write user [tty]\n"); 139 exit(1); 140 } 141 if (setgid(getgid()) == -1) 142 err(1, "setgid"); 143 do_write(ttyfd, mytty, myuid); 144 done(0); 145 /* NOTREACHED */ 146 #ifdef __GNUC__ 147 return (0); 148 #endif 149 } 150 151 /* 152 * utmp_chk - checks that the given user is actually logged in on 153 * the given tty 154 */ 155 int 156 utmp_chk(const char *user, const char *tty) 157 { 158 struct utmpentry *ep; 159 160 (void)getutentries(NULL, &ep); 161 162 for (; ep; ep = ep->next) 163 if (strcmp(user, ep->name) == 0 && strcmp(tty, ep->line) == 0) 164 return(0); 165 return(1); 166 } 167 168 /* 169 * search_utmp - search utmp for the "best" terminal to write to 170 * 171 * Ignores terminals with messages disabled, and of the rest, returns 172 * the one with the most recent access time. Returns as value the number 173 * of the user's terminals with messages enabled, or -1 if the user is 174 * not logged in at all. 175 * 176 * Special case for writing to yourself - ignore the terminal you're 177 * writing from, unless that's the only terminal with messages enabled. 178 */ 179 int 180 search_utmp(char *user, char *mytty, uid_t myuid) 181 { 182 char tty[MAXPATHLEN]; 183 time_t bestatime, atime; 184 int nloggedttys, nttys, msgsok, user_is_me; 185 struct utmpentry *ep; 186 int fd, nfd; 187 uid_t uid; 188 189 if (uid_from_user(user, &uid) == -1) 190 errx(1, "%s: unknown user", user); 191 192 (void)getutentries(NULL, &ep); 193 194 nloggedttys = nttys = 0; 195 bestatime = 0; 196 user_is_me = 0; 197 fd = -1; 198 for (; ep; ep = ep->next) 199 if (strcmp(user, ep->name) == 0) { 200 ++nloggedttys; 201 nfd = term_chk(uid, ep->line, &msgsok, &atime, 0); 202 if (nfd == -1) 203 continue; /* bad term? skip */ 204 if (myuid && !msgsok) { 205 close(nfd); 206 continue; /* skip ttys with msgs off */ 207 } 208 if (strcmp(ep->line, mytty) == 0) { 209 user_is_me = 1; 210 if (fd == -1) 211 fd = nfd; 212 else 213 close(nfd); 214 continue; /* don't write to yourself */ 215 } 216 ++nttys; 217 if (atime > bestatime) { 218 bestatime = atime; 219 (void)strlcpy(tty, ep->line, sizeof(tty)); 220 close(fd); 221 fd = nfd; 222 } else 223 close(nfd); 224 } 225 226 if (nloggedttys == 0) 227 errx(1, "%s is not logged in", user); 228 if (nttys == 0) { 229 if (user_is_me) /* ok, so write to yourself! */ 230 return fd; 231 errx(1, "%s has messages disabled", user); 232 } else if (nttys > 1) 233 warnx("%s is logged in more than once; writing to %s", 234 user, tty); 235 return fd; 236 } 237 238 /* 239 * term_chk - check that a terminal exists, and get the message bit 240 * and the access time 241 */ 242 int 243 term_chk(uid_t uid, const char *tty, int *msgsokP, time_t *atimeP, int ismytty) 244 { 245 char path[MAXPATHLEN]; 246 struct stat s; 247 int i, fd, serrno; 248 249 if (strcspn(tty, "./") != strlen(tty)) { 250 errno = EINVAL; return(-1); 251 } 252 i = snprintf(path, sizeof path, _PATH_DEV "%s", tty); 253 if (i < 0 || i >= sizeof(path)) { 254 errno = ENOMEM; return(-1); 255 } 256 257 (void)setegid(saved_egid); 258 fd = open(path, O_WRONLY, 0); 259 serrno = errno; 260 (void)setegid(getgid()); 261 errno = serrno; 262 263 if (fd == -1) 264 return(-1); 265 if (fstat(fd, &s) == -1) 266 goto error; 267 if (!isatty(fd) || s.st_uid != uid) 268 goto error; 269 *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */ 270 *atimeP = s.st_atime; 271 if (ismytty) 272 (void) close(fd); 273 return(ismytty? 0: fd); 274 error: 275 if (fd != -1) { 276 serrno = errno; 277 close(fd); 278 errno = serrno; 279 } 280 return(-1); 281 } 282 283 /* 284 * do_write - actually make the connection 285 */ 286 void 287 do_write(int ttyfd, const char *mytty, const uid_t myuid) 288 { 289 const char *login; 290 char *nows; 291 struct passwd *pwd; 292 time_t now; 293 char host[MAXHOSTNAMELEN + 1], line[512]; 294 295 /* Determine our login name before we re-open stdout */ 296 if ((login = getlogin()) == NULL) { 297 if ((pwd = getpwuid(myuid)) != NULL) 298 login = pwd->pw_name; 299 else login = "???"; 300 } 301 302 if (dup2(ttyfd, STDOUT_FILENO) == -1) 303 err(1, "dup2"); 304 305 (void)signal(SIGINT, done); 306 (void)signal(SIGHUP, done); 307 (void)close(ttyfd); 308 309 /* print greeting */ 310 if (gethostname(host, sizeof(host)) < 0) 311 (void)strncpy(host, "???", sizeof(host) - 1); 312 else 313 host[sizeof(host) - 1] = '\0'; 314 now = time((time_t *)NULL); 315 nows = ctime(&now); 316 nows[16] = '\0'; 317 (void)printf("\r\n\a\a\aMessage from %s@%s on %s at %s ...\r\n", 318 login, host, mytty, nows + 11); 319 320 while (fgets(line, sizeof(line), stdin) != NULL) 321 wr_fputs(line); 322 } 323 324 /* 325 * done - cleanup and exit 326 */ 327 void 328 done(int signo) 329 { 330 331 (void)write(STDOUT_FILENO, "EOF\r\n", sizeof("EOF\r\n") - 1); 332 if (signo == 0) 333 exit(0); 334 else 335 _exit(0); 336 } 337 338 /* 339 * wr_fputs - like fputs(), but makes control characters visible and 340 * turns \n into \r\n 341 */ 342 void 343 wr_fputs(char *s) 344 { 345 unsigned char c; 346 347 #define PUTC(c) if (putchar(c) == EOF) goto err; 348 349 for (; *s != '\0'; ++s) { 350 c = toascii(*s); 351 if (c == '\n') { 352 PUTC('\r'); 353 } else if (!isprint(c) && !isspace(c) && c != '\a') { 354 PUTC('^'); 355 c ^= 0x40; /* DEL to ?, others to alpha */ 356 } 357 PUTC(c); 358 } 359 return; 360 361 err: err(1, NULL); 362 #undef PUTC 363 } 364
Indexes created Wed Sep 24 15:09:51 GMT 2025