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 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #include <sys/cdefs.h> 38 39 __FBSDID("$FreeBSD$"); 40 41 #ifndef lint 42 static const char copyright[] = 43 "@(#) Copyright (c) 1989, 1993\n\ 44 The Regents of the University of California. All rights reserved.\n"; 45 #endif 46 47 #ifndef lint 48 static const char sccsid[] = "@(#)write.c 8.1 (Berkeley) 6/6/93"; 49 #endif 50 51 #include <sys/param.h> 52 #include <sys/signal.h> 53 #include <sys/stat.h> 54 #include <sys/file.h> 55 #include <sys/time.h> 56 #include <ctype.h> 57 #include <err.h> 58 #include <locale.h> 59 #include <paths.h> 60 #include <pwd.h> 61 #include <stdio.h> 62 #include <string.h> 63 #include <unistd.h> 64 #include <utmp.h> 65 66 void done __P((int)); 67 void do_write __P((char *, char *, uid_t)); 68 static void usage __P((void)); 69 int term_chk __P((char *, int *, time_t *, int)); 70 void wr_fputs __P((unsigned char *s)); 71 void search_utmp __P((char *, char *, char *, uid_t)); 72 int utmp_chk __P((char *, char *)); 73 74 int 75 main(argc, argv) 76 int argc; 77 char **argv; 78 { 79 register char *cp; 80 time_t atime; 81 uid_t myuid; 82 int msgsok, myttyfd; 83 char tty[MAXPATHLEN], *mytty; 84 85 (void)setlocale(LC_CTYPE, ""); 86 87 /* check that sender has write enabled */ 88 if (isatty(fileno(stdin))) 89 myttyfd = fileno(stdin); 90 else if (isatty(fileno(stdout))) 91 myttyfd = fileno(stdout); 92 else if (isatty(fileno(stderr))) 93 myttyfd = fileno(stderr); 94 else 95 errx(1, "can't find your tty"); 96 if (!(mytty = ttyname(myttyfd))) 97 errx(1, "can't find your tty's name"); 98 if ((cp = rindex(mytty, '/'))) 99 mytty = cp + 1; 100 if (term_chk(mytty, &msgsok, &atime, 1)) 101 exit(1); 102 if (!msgsok) 103 errx(1, "you have write permission turned off"); 104 105 myuid = getuid(); 106 107 /* check args */ 108 switch (argc) { 109 case 2: 110 search_utmp(argv[1], tty, mytty, myuid); 111 do_write(tty, mytty, myuid); 112 break; 113 case 3: 114 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV))) 115 argv[2] += strlen(_PATH_DEV); 116 if (utmp_chk(argv[1], argv[2])) 117 errx(1, "%s is not logged in on %s", argv[1], argv[2]); 118 if (term_chk(argv[2], &msgsok, &atime, 1)) 119 exit(1); 120 if (myuid && !msgsok) 121 errx(1, "%s has messages disabled on %s", argv[1], argv[2]); 122 do_write(argv[2], mytty, myuid); 123 break; 124 default: 125 usage(); 126 } 127 done(0); 128 return (0); 129 } 130 131 static void 132 usage() 133 { 134 (void)fprintf(stderr, "usage: write user [tty]\n"); 135 exit(1); 136 } 137 138 /* 139 * utmp_chk - checks that the given user is actually logged in on 140 * the given tty 141 */ 142 int 143 utmp_chk(user, tty) 144 char *user, *tty; 145 { 146 struct utmp u; 147 int ufd; 148 149 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 150 return(0); /* ignore error, shouldn't happen anyway */ 151 152 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 153 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 154 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 155 (void)close(ufd); 156 return(0); 157 } 158 159 (void)close(ufd); 160 return(1); 161 } 162 163 /* 164 * search_utmp - search utmp for the "best" terminal to write to 165 * 166 * Ignores terminals with messages disabled, and of the rest, returns 167 * the one with the most recent access time. Returns as value the number 168 * of the user's terminals with messages enabled, or -1 if the user is 169 * not logged in at all. 170 * 171 * Special case for writing to yourself - ignore the terminal you're 172 * writing from, unless that's the only terminal with messages enabled. 173 */ 174 void 175 search_utmp(user, tty, mytty, myuid) 176 char *user, *tty, *mytty; 177 uid_t myuid; 178 { 179 struct utmp u; 180 time_t bestatime, atime; 181 int ufd, nloggedttys, nttys, msgsok, user_is_me; 182 char atty[UT_LINESIZE + 1]; 183 184 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 185 err(1, "utmp"); 186 187 nloggedttys = nttys = 0; 188 bestatime = 0; 189 user_is_me = 0; 190 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 191 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 192 ++nloggedttys; 193 (void)strncpy(atty, u.ut_line, UT_LINESIZE); 194 atty[UT_LINESIZE] = '\0'; 195 if (term_chk(atty, &msgsok, &atime, 0)) 196 continue; /* bad term? skip */ 197 if (myuid && !msgsok) 198 continue; /* skip ttys with msgs off */ 199 if (strcmp(atty, mytty) == 0) { 200 user_is_me = 1; 201 continue; /* don't write to yourself */ 202 } 203 ++nttys; 204 if (atime > bestatime) { 205 bestatime = atime; 206 (void)strcpy(tty, atty); 207 } 208 } 209 210 (void)close(ufd); 211 if (nloggedttys == 0) 212 errx(1, "%s is not logged in", user); 213 if (nttys == 0) { 214 if (user_is_me) { /* ok, so write to yourself! */ 215 (void)strcpy(tty, mytty); 216 return; 217 } 218 errx(1, "%s has messages disabled", user); 219 } else if (nttys > 1) { 220 warnx("%s is logged in more than once; writing to %s", user, tty); 221 } 222 } 223 224 /* 225 * term_chk - check that a terminal exists, and get the message bit 226 * and the access time 227 */ 228 int 229 term_chk(tty, msgsokP, atimeP, showerror) 230 char *tty; 231 int *msgsokP, showerror; 232 time_t *atimeP; 233 { 234 struct stat s; 235 char path[MAXPATHLEN]; 236 237 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 238 if (stat(path, &s) < 0) { 239 if (showerror) 240 warn("%s", path); 241 return(1); 242 } 243 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 244 *atimeP = s.st_atime; 245 return(0); 246 } 247 248 /* 249 * do_write - actually make the connection 250 */ 251 void 252 do_write(tty, mytty, myuid) 253 char *tty, *mytty; 254 uid_t myuid; 255 { 256 const char *login; 257 char *nows; 258 struct passwd *pwd; 259 time_t now; 260 char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 261 262 /* Determine our login name before the we reopen() stdout */ 263 if ((login = getlogin()) == NULL) { 264 if ((pwd = getpwuid(myuid))) 265 login = pwd->pw_name; 266 else 267 login = "???"; 268 } 269 270 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 271 if ((freopen(path, "w", stdout)) == NULL) 272 err(1, "%s", path); 273 274 (void)signal(SIGINT, done); 275 (void)signal(SIGHUP, done); 276 277 /* print greeting */ 278 if (gethostname(host, sizeof(host)) < 0) 279 (void)strcpy(host, "???"); 280 now = time((time_t *)NULL); 281 nows = ctime(&now); 282 nows[16] = '\0'; 283 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 284 login, host, mytty, nows + 11); 285 286 while (fgets(line, sizeof(line), stdin) != NULL) 287 wr_fputs(line); 288 } 289 290 /* 291 * done - cleanup and exit 292 */ 293 void 294 done(n) 295 int n __unused; 296 { 297 (void)printf("EOF\r\n"); 298 exit(0); 299 } 300 301 /* 302 * wr_fputs - like fputs(), but makes control characters visible and 303 * turns \n into \r\n 304 */ 305 void 306 wr_fputs(s) 307 unsigned char *s; 308 { 309 310 #define PUTC(c) if (putchar(c) == EOF) err(1, NULL); 311 312 for (; *s != '\0'; ++s) { 313 if (*s == '\n') { 314 PUTC('\r'); 315 } else if (((*s & 0x80) && *s < 0xA0) || 316 /* disable upper controls */ 317 (!isprint(*s) && !isspace(*s) && 318 *s != '\a' && *s != '\b') 319 ) { 320 if (*s & 0x80) { 321 *s &= ~0x80; 322 PUTC('M'); 323 PUTC('-'); 324 } 325 if (iscntrl(*s)) { 326 *s ^= 0x40; 327 PUTC('^'); 328 } 329 } 330 PUTC(*s); 331 } 332 return; 333 #undef PUTC 334 } 335