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[] = "@(#)write.c 8.1 (Berkeley) 6/6/93"; 45 #endif /* not lint */ 46 47 #include <sys/param.h> 48 #include <sys/signal.h> 49 #include <sys/stat.h> 50 #include <sys/file.h> 51 #include <sys/time.h> 52 #include <utmp.h> 53 #include <ctype.h> 54 #include <pwd.h> 55 #include <stdio.h> 56 #include <string.h> 57 58 extern int errno; 59 60 main(argc, argv) 61 int argc; 62 char **argv; 63 { 64 register char *cp; 65 time_t atime; 66 uid_t myuid; 67 int msgsok, myttyfd; 68 char tty[MAXPATHLEN], *mytty, *ttyname(); 69 void done(); 70 71 /* check that sender has write enabled */ 72 if (isatty(fileno(stdin))) 73 myttyfd = fileno(stdin); 74 else if (isatty(fileno(stdout))) 75 myttyfd = fileno(stdout); 76 else if (isatty(fileno(stderr))) 77 myttyfd = fileno(stderr); 78 else { 79 (void)fprintf(stderr, "write: can't find your tty\n"); 80 exit(1); 81 } 82 if (!(mytty = ttyname(myttyfd))) { 83 (void)fprintf(stderr, "write: can't find your tty's name\n"); 84 exit(1); 85 } 86 if (cp = rindex(mytty, '/')) 87 mytty = cp + 1; 88 if (term_chk(mytty, &msgsok, &atime, 1)) 89 exit(1); 90 if (!msgsok) { 91 (void)fprintf(stderr, 92 "write: you have write permission turned off.\n"); 93 exit(1); 94 } 95 96 myuid = getuid(); 97 98 /* check args */ 99 switch (argc) { 100 case 2: 101 search_utmp(argv[1], tty, mytty, myuid); 102 do_write(tty, mytty, myuid); 103 break; 104 case 3: 105 if (!strncmp(argv[2], "/dev/", 5)) 106 argv[2] += 5; 107 if (utmp_chk(argv[1], argv[2])) { 108 (void)fprintf(stderr, 109 "write: %s is not logged in on %s.\n", 110 argv[1], argv[2]); 111 exit(1); 112 } 113 if (term_chk(argv[2], &msgsok, &atime, 1)) 114 exit(1); 115 if (myuid && !msgsok) { 116 (void)fprintf(stderr, 117 "write: %s has messages disabled on %s\n", 118 argv[1], argv[2]); 119 exit(1); 120 } 121 do_write(argv[2], mytty, myuid); 122 break; 123 default: 124 (void)fprintf(stderr, "usage: write user [tty]\n"); 125 exit(1); 126 } 127 done(); 128 /* NOTREACHED */ 129 } 130 131 /* 132 * utmp_chk - checks that the given user is actually logged in on 133 * the given tty 134 */ 135 utmp_chk(user, tty) 136 char *user, *tty; 137 { 138 struct utmp u; 139 int ufd; 140 141 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 142 return(0); /* ignore error, shouldn't happen anyway */ 143 144 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 145 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 146 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 147 (void)close(ufd); 148 return(0); 149 } 150 151 (void)close(ufd); 152 return(1); 153 } 154 155 /* 156 * search_utmp - search utmp for the "best" terminal to write to 157 * 158 * Ignores terminals with messages disabled, and of the rest, returns 159 * the one with the most recent access time. Returns as value the number 160 * of the user's terminals with messages enabled, or -1 if the user is 161 * not logged in at all. 162 * 163 * Special case for writing to yourself - ignore the terminal you're 164 * writing from, unless that's the only terminal with messages enabled. 165 */ 166 search_utmp(user, tty, mytty, myuid) 167 char *user, *tty, *mytty; 168 uid_t myuid; 169 { 170 struct utmp u; 171 time_t bestatime, atime; 172 int ufd, nloggedttys, nttys, msgsok, user_is_me; 173 char atty[UT_LINESIZE + 1]; 174 175 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) { 176 perror("utmp"); 177 exit(1); 178 } 179 180 nloggedttys = nttys = 0; 181 bestatime = 0; 182 user_is_me = 0; 183 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 184 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 185 ++nloggedttys; 186 (void)strncpy(atty, u.ut_line, UT_LINESIZE); 187 atty[UT_LINESIZE] = '\0'; 188 if (term_chk(atty, &msgsok, &atime, 0)) 189 continue; /* bad term? skip */ 190 if (myuid && !msgsok) 191 continue; /* skip ttys with msgs off */ 192 if (strcmp(atty, mytty) == 0) { 193 user_is_me = 1; 194 continue; /* don't write to yourself */ 195 } 196 ++nttys; 197 if (atime > bestatime) { 198 bestatime = atime; 199 (void)strcpy(tty, atty); 200 } 201 } 202 203 (void)close(ufd); 204 if (nloggedttys == 0) { 205 (void)fprintf(stderr, "write: %s is not logged in\n", user); 206 exit(1); 207 } 208 if (nttys == 0) { 209 if (user_is_me) { /* ok, so write to yourself! */ 210 (void)strcpy(tty, mytty); 211 return; 212 } 213 (void)fprintf(stderr, 214 "write: %s has messages disabled\n", user); 215 exit(1); 216 } else if (nttys > 1) { 217 (void)fprintf(stderr, 218 "write: %s is logged in more than once; writing to %s\n", 219 user, tty); 220 } 221 } 222 223 /* 224 * term_chk - check that a terminal exists, and get the message bit 225 * and the access time 226 */ 227 term_chk(tty, msgsokP, atimeP, showerror) 228 char *tty; 229 int *msgsokP, showerror; 230 time_t *atimeP; 231 { 232 struct stat s; 233 char path[MAXPATHLEN]; 234 235 (void)sprintf(path, "/dev/%s", tty); 236 if (stat(path, &s) < 0) { 237 if (showerror) 238 (void)fprintf(stderr, 239 "write: %s: %s\n", path, strerror(errno)); 240 return(1); 241 } 242 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 243 *atimeP = s.st_atime; 244 return(0); 245 } 246 247 /* 248 * do_write - actually make the connection 249 */ 250 do_write(tty, mytty, myuid) 251 char *tty, *mytty; 252 uid_t myuid; 253 { 254 register char *login, *nows; 255 register struct passwd *pwd; 256 time_t now, time(); 257 char *getlogin(), path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 258 void done(); 259 260 /* Determine our login name before the we reopen() stdout */ 261 if ((login = getlogin()) == NULL) 262 if (pwd = getpwuid(myuid)) 263 login = pwd->pw_name; 264 else 265 login = "???"; 266 267 (void)sprintf(path, "/dev/%s", tty); 268 if ((freopen(path, "w", stdout)) == NULL) { 269 (void)fprintf(stderr, "write: %s: %s\n", path, strerror(errno)); 270 exit(1); 271 } 272 273 (void)signal(SIGINT, done); 274 (void)signal(SIGHUP, done); 275 276 /* print greeting */ 277 if (gethostname(host, sizeof(host)) < 0) 278 (void)strcpy(host, "???"); 279 now = time((time_t *)NULL); 280 nows = ctime(&now); 281 nows[16] = '\0'; 282 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 283 login, host, mytty, nows + 11); 284 285 while (fgets(line, sizeof(line), stdin) != NULL) 286 wr_fputs(line); 287 } 288 289 /* 290 * done - cleanup and exit 291 */ 292 void 293 done() 294 { 295 (void)printf("EOF\r\n"); 296 exit(0); 297 } 298 299 /* 300 * wr_fputs - like fputs(), but makes control characters visible and 301 * turns \n into \r\n 302 */ 303 wr_fputs(s) 304 register char *s; 305 { 306 register char c; 307 308 #define PUTC(c) if (putchar(c) == EOF) goto err; 309 310 for (; *s != '\0'; ++s) { 311 c = toascii(*s); 312 if (c == '\n') { 313 PUTC('\r'); 314 PUTC('\n'); 315 } else if (!isprint(c) && !isspace(c) && c != '\007') { 316 PUTC('^'); 317 PUTC(c^0x40); /* DEL to ?, others to alpha */ 318 } else 319 PUTC(c); 320 } 321 return; 322 323 err: (void)fprintf(stderr, "write: %s\n", strerror(errno)); 324 exit(1); 325 #undef PUTC 326 } 327