1 /* 2 * Copyright (c) 1989, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #ifndef lint 34 static const char copyright[] = 35 "@(#) Copyright (c) 1989, 1993\n\ 36 The Regents of the University of California. All rights reserved.\n"; 37 #endif 38 39 #if 0 40 #ifndef lint 41 static char sccsid[] = "@(#)write.c 8.1 (Berkeley) 6/6/93"; 42 #endif 43 #endif 44 45 #include <sys/cdefs.h> 46 __FBSDID("$FreeBSD$"); 47 48 #include <sys/param.h> 49 #include <sys/capsicum.h> 50 #include <sys/filio.h> 51 #include <sys/signal.h> 52 #include <sys/stat.h> 53 #include <sys/time.h> 54 55 #include <capsicum_helpers.h> 56 #include <ctype.h> 57 #include <err.h> 58 #include <errno.h> 59 #include <locale.h> 60 #include <paths.h> 61 #include <pwd.h> 62 #include <stdio.h> 63 #include <stdlib.h> 64 #include <string.h> 65 #include <unistd.h> 66 #include <utmpx.h> 67 #include <wchar.h> 68 #include <wctype.h> 69 70 void done(int); 71 void do_write(int, char *, char *, const char *); 72 static void usage(void); 73 int term_chk(int, char *, int *, time_t *, int); 74 void wr_fputs(wchar_t *s); 75 void search_utmp(int, char *, char *, char *, uid_t); 76 int utmp_chk(char *, char *); 77 78 int 79 main(int argc, char **argv) 80 { 81 unsigned long cmds[] = { TIOCGETA, TIOCGWINSZ, FIODGNAME }; 82 cap_rights_t rights; 83 struct passwd *pwd; 84 time_t atime; 85 uid_t myuid; 86 int msgsok, myttyfd; 87 char tty[MAXPATHLEN], *mytty; 88 const char *login; 89 int devfd; 90 91 (void)setlocale(LC_CTYPE, ""); 92 93 devfd = open(_PATH_DEV, O_RDONLY); 94 if (devfd < 0) 95 err(1, "open(/dev)"); 96 cap_rights_init(&rights, CAP_FCNTL, CAP_FSTAT, CAP_IOCTL, CAP_LOOKUP, 97 CAP_PWRITE); 98 if (cap_rights_limit(devfd, &rights) < 0 && errno != ENOSYS) 99 err(1, "can't limit devfd rights"); 100 101 /* 102 * Can't use capsicum helpers here because we need the additional 103 * FIODGNAME ioctl. 104 */ 105 cap_rights_init(&rights, CAP_FCNTL, CAP_FSTAT, CAP_IOCTL, CAP_READ, 106 CAP_WRITE); 107 if ((cap_rights_limit(STDIN_FILENO, &rights) < 0 && errno != ENOSYS) || 108 (cap_rights_limit(STDOUT_FILENO, &rights) < 0 && errno != ENOSYS) || 109 (cap_rights_limit(STDERR_FILENO, &rights) < 0 && errno != ENOSYS) || 110 (cap_ioctls_limit(STDIN_FILENO, cmds, nitems(cmds)) < 0 && errno != ENOSYS) || 111 (cap_ioctls_limit(STDOUT_FILENO, cmds, nitems(cmds)) < 0 && errno != ENOSYS) || 112 (cap_ioctls_limit(STDERR_FILENO, cmds, nitems(cmds)) < 0 && errno != ENOSYS) || 113 (cap_fcntls_limit(STDIN_FILENO, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS) || 114 (cap_fcntls_limit(STDOUT_FILENO, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS) || 115 (cap_fcntls_limit(STDERR_FILENO, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS)) 116 err(1, "can't limit stdio rights"); 117 118 caph_cache_catpages(); 119 caph_cache_tzdata(); 120 121 /* 122 * Cache UTX database fds. 123 */ 124 setutxent(); 125 126 /* 127 * Determine our login name before we reopen() stdout 128 * and before entering capability sandbox. 129 */ 130 myuid = getuid(); 131 if ((login = getlogin()) == NULL) { 132 if ((pwd = getpwuid(myuid))) 133 login = pwd->pw_name; 134 else 135 login = "???"; 136 } 137 138 if (cap_enter() < 0 && errno != ENOSYS) 139 err(1, "cap_enter"); 140 141 while (getopt(argc, argv, "") != -1) 142 usage(); 143 argc -= optind; 144 argv += optind; 145 146 /* check that sender has write enabled */ 147 if (isatty(fileno(stdin))) 148 myttyfd = fileno(stdin); 149 else if (isatty(fileno(stdout))) 150 myttyfd = fileno(stdout); 151 else if (isatty(fileno(stderr))) 152 myttyfd = fileno(stderr); 153 else 154 errx(1, "can't find your tty"); 155 if (!(mytty = ttyname(myttyfd))) 156 errx(1, "can't find your tty's name"); 157 if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV))) 158 mytty += strlen(_PATH_DEV); 159 if (term_chk(devfd, mytty, &msgsok, &atime, 1)) 160 exit(1); 161 if (!msgsok) 162 errx(1, "you have write permission turned off"); 163 164 /* check args */ 165 switch (argc) { 166 case 1: 167 search_utmp(devfd, argv[0], tty, mytty, myuid); 168 do_write(devfd, tty, mytty, login); 169 break; 170 case 2: 171 if (!strncmp(argv[1], _PATH_DEV, strlen(_PATH_DEV))) 172 argv[1] += strlen(_PATH_DEV); 173 if (utmp_chk(argv[0], argv[1])) 174 errx(1, "%s is not logged in on %s", argv[0], argv[1]); 175 if (term_chk(devfd, argv[1], &msgsok, &atime, 1)) 176 exit(1); 177 if (myuid && !msgsok) 178 errx(1, "%s has messages disabled on %s", argv[0], argv[1]); 179 do_write(devfd, argv[1], mytty, login); 180 break; 181 default: 182 usage(); 183 } 184 done(0); 185 return (0); 186 } 187 188 static void 189 usage(void) 190 { 191 (void)fprintf(stderr, "usage: write user [tty]\n"); 192 exit(1); 193 } 194 195 /* 196 * utmp_chk - checks that the given user is actually logged in on 197 * the given tty 198 */ 199 int 200 utmp_chk(char *user, char *tty) 201 { 202 struct utmpx lu, *u; 203 204 strncpy(lu.ut_line, tty, sizeof lu.ut_line); 205 setutxent(); 206 while ((u = getutxline(&lu)) != NULL) 207 if (u->ut_type == USER_PROCESS && 208 strcmp(user, u->ut_user) == 0) { 209 endutxent(); 210 return(0); 211 } 212 endutxent(); 213 return(1); 214 } 215 216 /* 217 * search_utmp - search utmp for the "best" terminal to write to 218 * 219 * Ignores terminals with messages disabled, and of the rest, returns 220 * the one with the most recent access time. Returns as value the number 221 * of the user's terminals with messages enabled, or -1 if the user is 222 * not logged in at all. 223 * 224 * Special case for writing to yourself - ignore the terminal you're 225 * writing from, unless that's the only terminal with messages enabled. 226 */ 227 void 228 search_utmp(int devfd, char *user, char *tty, char *mytty, uid_t myuid) 229 { 230 struct utmpx *u; 231 time_t bestatime, atime; 232 int nloggedttys, nttys, msgsok, user_is_me; 233 234 nloggedttys = nttys = 0; 235 bestatime = 0; 236 user_is_me = 0; 237 238 setutxent(); 239 while ((u = getutxent()) != NULL) 240 if (u->ut_type == USER_PROCESS && 241 strcmp(user, u->ut_user) == 0) { 242 ++nloggedttys; 243 if (term_chk(devfd, u->ut_line, &msgsok, &atime, 0)) 244 continue; /* bad term? skip */ 245 if (myuid && !msgsok) 246 continue; /* skip ttys with msgs off */ 247 if (strcmp(u->ut_line, mytty) == 0) { 248 user_is_me = 1; 249 continue; /* don't write to yourself */ 250 } 251 ++nttys; 252 if (atime > bestatime) { 253 bestatime = atime; 254 (void)strlcpy(tty, u->ut_line, MAXPATHLEN); 255 } 256 } 257 endutxent(); 258 259 if (nloggedttys == 0) 260 errx(1, "%s is not logged in", user); 261 if (nttys == 0) { 262 if (user_is_me) { /* ok, so write to yourself! */ 263 (void)strlcpy(tty, mytty, MAXPATHLEN); 264 return; 265 } 266 errx(1, "%s has messages disabled", user); 267 } else if (nttys > 1) { 268 warnx("%s is logged in more than once; writing to %s", user, tty); 269 } 270 } 271 272 /* 273 * term_chk - check that a terminal exists, and get the message bit 274 * and the access time 275 */ 276 int 277 term_chk(int devfd, char *tty, int *msgsokP, time_t *atimeP, int showerror) 278 { 279 struct stat s; 280 281 if (fstatat(devfd, tty, &s, 0) < 0) { 282 if (showerror) 283 warn("%s%s", _PATH_DEV, tty); 284 return(1); 285 } 286 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 287 *atimeP = s.st_atime; 288 return(0); 289 } 290 291 /* 292 * do_write - actually make the connection 293 */ 294 void 295 do_write(int devfd, char *tty, char *mytty, const char *login) 296 { 297 char *nows; 298 time_t now; 299 char host[MAXHOSTNAMELEN]; 300 wchar_t line[512]; 301 int fd; 302 303 fd = openat(devfd, tty, O_WRONLY); 304 if (fd < 0) 305 err(1, "openat(%s%s)", _PATH_DEV, tty); 306 fclose(stdout); 307 stdout = fdopen(fd, "w"); 308 if (stdout == NULL) 309 err(1, "%s%s", _PATH_DEV, tty); 310 311 (void)signal(SIGINT, done); 312 (void)signal(SIGHUP, done); 313 314 /* print greeting */ 315 if (gethostname(host, sizeof(host)) < 0) 316 (void)strcpy(host, "???"); 317 now = time((time_t *)NULL); 318 nows = ctime(&now); 319 nows[16] = '\0'; 320 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 321 login, host, mytty, nows + 11); 322 323 while (fgetws(line, sizeof(line)/sizeof(wchar_t), stdin) != NULL) 324 wr_fputs(line); 325 } 326 327 /* 328 * done - cleanup and exit 329 */ 330 void 331 done(int n __unused) 332 { 333 (void)printf("EOF\r\n"); 334 exit(0); 335 } 336 337 /* 338 * wr_fputs - like fputs(), but makes control characters visible and 339 * turns \n into \r\n 340 */ 341 void 342 wr_fputs(wchar_t *s) 343 { 344 345 #define PUTC(c) if (putwchar(c) == WEOF) err(1, NULL); 346 347 for (; *s != L'\0'; ++s) { 348 if (*s == L'\n') { 349 PUTC(L'\r'); 350 PUTC(L'\n'); 351 } else if (iswprint(*s) || iswspace(*s)) { 352 PUTC(*s); 353 } else { 354 wprintf(L"<0x%X>", *s); 355 } 356 } 357 return; 358 #undef PUTC 359 } 360