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 #ifndef lint 38 static char copyright[] = 39 "@(#) Copyright (c) 1989, 1993\n\ 40 The Regents of the University of California. All rights reserved.\n"; 41 #endif /* not lint */ 42 43 #ifndef lint 44 /*static char sccsid[] = "from: @(#)write.c 8.1 (Berkeley) 6/6/93";*/ 45 static char *rcsid = "$Id: write.c,v 1.3 1994/09/19 08:18:24 mycroft Exp $"; 46 #endif /* not lint */ 47 48 #include <sys/param.h> 49 #include <sys/signal.h> 50 #include <sys/stat.h> 51 #include <sys/file.h> 52 #include <sys/time.h> 53 54 #include <err.h> 55 #include <utmp.h> 56 #include <ctype.h> 57 #include <pwd.h> 58 #include <stdio.h> 59 #include <string.h> 60 61 extern int errno; 62 63 main(argc, argv) 64 int argc; 65 char **argv; 66 { 67 register char *cp; 68 time_t atime; 69 uid_t myuid; 70 int msgsok, myttyfd; 71 char tty[MAXPATHLEN], *mytty, *ttyname(); 72 void done(); 73 74 /* check that sender has write enabled */ 75 if (isatty(fileno(stdin))) 76 myttyfd = fileno(stdin); 77 else if (isatty(fileno(stdout))) 78 myttyfd = fileno(stdout); 79 else if (isatty(fileno(stderr))) 80 myttyfd = fileno(stderr); 81 else 82 errx(1, "can't find your tty"); 83 if (!(mytty = ttyname(myttyfd))) 84 errx(1, "can't find your tty's name"); 85 if (cp = strrchr(mytty, '/')) 86 mytty = cp + 1; 87 if (term_chk(mytty, &msgsok, &atime, 1)) 88 exit(1); 89 if (!msgsok) 90 errx(1, "you have write permission turned off"); 91 92 myuid = getuid(); 93 94 /* check args */ 95 switch (argc) { 96 case 2: 97 search_utmp(argv[1], tty, mytty, myuid); 98 do_write(tty, mytty, myuid); 99 break; 100 case 3: 101 if (!strncmp(argv[2], "/dev/", 5)) 102 argv[2] += 5; 103 if (utmp_chk(argv[1], argv[2])) 104 errx(1, "%s is not logged in on %s", 105 argv[1], argv[2]); 106 if (term_chk(argv[2], &msgsok, &atime, 1)) 107 exit(1); 108 if (myuid && !msgsok) 109 errx(1, "%s has messages disabled on %s", 110 argv[1], argv[2]); 111 do_write(argv[2], mytty, myuid); 112 break; 113 default: 114 (void)fprintf(stderr, "usage: write user [tty]\n"); 115 exit(1); 116 } 117 done(); 118 /* NOTREACHED */ 119 } 120 121 /* 122 * utmp_chk - checks that the given user is actually logged in on 123 * the given tty 124 */ 125 utmp_chk(user, tty) 126 char *user, *tty; 127 { 128 struct utmp u; 129 int ufd; 130 131 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 132 return(0); /* ignore error, shouldn't happen anyway */ 133 134 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 135 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 136 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 137 (void)close(ufd); 138 return(0); 139 } 140 141 (void)close(ufd); 142 return(1); 143 } 144 145 /* 146 * search_utmp - search utmp for the "best" terminal to write to 147 * 148 * Ignores terminals with messages disabled, and of the rest, returns 149 * the one with the most recent access time. Returns as value the number 150 * of the user's terminals with messages enabled, or -1 if the user is 151 * not logged in at all. 152 * 153 * Special case for writing to yourself - ignore the terminal you're 154 * writing from, unless that's the only terminal with messages enabled. 155 */ 156 search_utmp(user, tty, mytty, myuid) 157 char *user, *tty, *mytty; 158 uid_t myuid; 159 { 160 struct utmp u; 161 time_t bestatime, atime; 162 int ufd, nloggedttys, nttys, msgsok, user_is_me; 163 char atty[UT_LINESIZE + 1]; 164 165 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 166 err(1, "%s", _PATH_UTMP); 167 168 nloggedttys = nttys = 0; 169 bestatime = 0; 170 user_is_me = 0; 171 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 172 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 173 ++nloggedttys; 174 (void)strncpy(atty, u.ut_line, UT_LINESIZE); 175 atty[UT_LINESIZE] = '\0'; 176 if (term_chk(atty, &msgsok, &atime, 0)) 177 continue; /* bad term? skip */ 178 if (myuid && !msgsok) 179 continue; /* skip ttys with msgs off */ 180 if (strcmp(atty, mytty) == 0) { 181 user_is_me = 1; 182 continue; /* don't write to yourself */ 183 } 184 ++nttys; 185 if (atime > bestatime) { 186 bestatime = atime; 187 (void)strcpy(tty, atty); 188 } 189 } 190 191 (void)close(ufd); 192 if (nloggedttys == 0) 193 errx(1, "%s is not logged in", user); 194 if (nttys == 0) { 195 if (user_is_me) { /* ok, so write to yourself! */ 196 (void)strcpy(tty, mytty); 197 return; 198 } 199 errx(1, "%s has messages disabled", user); 200 } else if (nttys > 1) 201 warnx("%s is logged in more than once; writing to %s", 202 user, tty); 203 } 204 205 /* 206 * term_chk - check that a terminal exists, and get the message bit 207 * and the access time 208 */ 209 term_chk(tty, msgsokP, atimeP, showerror) 210 char *tty; 211 int *msgsokP, showerror; 212 time_t *atimeP; 213 { 214 struct stat s; 215 char path[MAXPATHLEN]; 216 217 (void)sprintf(path, "/dev/%s", tty); 218 if (stat(path, &s) < 0) { 219 if (showerror) 220 warn("%s", path); 221 return(1); 222 } 223 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 224 *atimeP = s.st_atime; 225 return(0); 226 } 227 228 /* 229 * do_write - actually make the connection 230 */ 231 do_write(tty, mytty, myuid) 232 char *tty, *mytty; 233 uid_t myuid; 234 { 235 register char *login, *nows; 236 register struct passwd *pwd; 237 time_t now, time(); 238 char *getlogin(), path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 239 void done(); 240 241 /* Determine our login name before the we reopen() stdout */ 242 if ((login = getlogin()) == NULL) 243 if (pwd = getpwuid(myuid)) 244 login = pwd->pw_name; 245 else 246 login = "???"; 247 248 (void)sprintf(path, "/dev/%s", tty); 249 if ((freopen(path, "w", stdout)) == NULL) 250 err(1, "%s", path); 251 252 (void)signal(SIGINT, done); 253 (void)signal(SIGHUP, done); 254 255 /* print greeting */ 256 if (gethostname(host, sizeof(host)) < 0) 257 (void)strcpy(host, "???"); 258 now = time((time_t *)NULL); 259 nows = ctime(&now); 260 nows[16] = '\0'; 261 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 262 login, host, mytty, nows + 11); 263 264 while (fgets(line, sizeof(line), stdin) != NULL) 265 wr_fputs(line); 266 } 267 268 /* 269 * done - cleanup and exit 270 */ 271 void 272 done() 273 { 274 (void)printf("EOF\r\n"); 275 exit(0); 276 } 277 278 /* 279 * wr_fputs - like fputs(), but makes control characters visible and 280 * turns \n into \r\n 281 */ 282 wr_fputs(s) 283 register char *s; 284 { 285 register char c; 286 287 #define PUTC(c) if (putchar(c) == EOF) goto err; 288 289 for (; *s != '\0'; ++s) { 290 c = toascii(*s); 291 if (c == '\n') { 292 PUTC('\r'); 293 PUTC('\n'); 294 } else if (!isprint(c) && !isspace(c) && c != '\007') { 295 PUTC('^'); 296 PUTC(c^0x40); /* DEL to ?, others to alpha */ 297 } else 298 PUTC(c); 299 } 300 return; 301 302 err: err(1, NULL); 303 #undef PUTC 304 } 305