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 const char copyright[] = 39 "@(#) Copyright (c) 1989, 1993\n\ 40 The Regents of the University of California. All rights reserved.\n"; 41 #endif 42 43 #if 0 44 #ifndef lint 45 static char sccsid[] = "@(#)write.c 8.1 (Berkeley) 6/6/93"; 46 #endif 47 #endif 48 49 #include <sys/cdefs.h> 50 __FBSDID("$FreeBSD$"); 51 52 #include <sys/param.h> 53 #include <sys/signal.h> 54 #include <sys/stat.h> 55 #include <sys/file.h> 56 #include <sys/time.h> 57 #include <ctype.h> 58 #include <err.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 <utmp.h> 67 68 void done(int); 69 void do_write(char *, char *, uid_t); 70 static void usage(void); 71 int term_chk(char *, int *, time_t *, int); 72 void wr_fputs(unsigned char *s); 73 void search_utmp(char *, char *, char *, uid_t); 74 int utmp_chk(char *, char *); 75 76 int 77 main(argc, argv) 78 int argc; 79 char **argv; 80 { 81 register char *cp; 82 time_t atime; 83 uid_t myuid; 84 int msgsok, myttyfd; 85 char tty[MAXPATHLEN], *mytty; 86 87 (void)setlocale(LC_CTYPE, ""); 88 89 /* check that sender has write enabled */ 90 if (isatty(fileno(stdin))) 91 myttyfd = fileno(stdin); 92 else if (isatty(fileno(stdout))) 93 myttyfd = fileno(stdout); 94 else if (isatty(fileno(stderr))) 95 myttyfd = fileno(stderr); 96 else 97 errx(1, "can't find your tty"); 98 if (!(mytty = ttyname(myttyfd))) 99 errx(1, "can't find your tty's name"); 100 if ((cp = rindex(mytty, '/'))) 101 mytty = cp + 1; 102 if (term_chk(mytty, &msgsok, &atime, 1)) 103 exit(1); 104 if (!msgsok) 105 errx(1, "you have write permission turned off"); 106 107 myuid = getuid(); 108 109 /* check args */ 110 switch (argc) { 111 case 2: 112 search_utmp(argv[1], tty, mytty, myuid); 113 do_write(tty, mytty, myuid); 114 break; 115 case 3: 116 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV))) 117 argv[2] += strlen(_PATH_DEV); 118 if (utmp_chk(argv[1], argv[2])) 119 errx(1, "%s is not logged in on %s", argv[1], argv[2]); 120 if (term_chk(argv[2], &msgsok, &atime, 1)) 121 exit(1); 122 if (myuid && !msgsok) 123 errx(1, "%s has messages disabled on %s", argv[1], argv[2]); 124 do_write(argv[2], mytty, myuid); 125 break; 126 default: 127 usage(); 128 } 129 done(0); 130 return (0); 131 } 132 133 static void 134 usage() 135 { 136 (void)fprintf(stderr, "usage: write user [tty]\n"); 137 exit(1); 138 } 139 140 /* 141 * utmp_chk - checks that the given user is actually logged in on 142 * the given tty 143 */ 144 int 145 utmp_chk(user, tty) 146 char *user, *tty; 147 { 148 struct utmp u; 149 int ufd; 150 151 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 152 return(0); /* ignore error, shouldn't happen anyway */ 153 154 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 155 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 156 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 157 (void)close(ufd); 158 return(0); 159 } 160 161 (void)close(ufd); 162 return(1); 163 } 164 165 /* 166 * search_utmp - search utmp for the "best" terminal to write to 167 * 168 * Ignores terminals with messages disabled, and of the rest, returns 169 * the one with the most recent access time. Returns as value the number 170 * of the user's terminals with messages enabled, or -1 if the user is 171 * not logged in at all. 172 * 173 * Special case for writing to yourself - ignore the terminal you're 174 * writing from, unless that's the only terminal with messages enabled. 175 */ 176 void 177 search_utmp(user, tty, mytty, myuid) 178 char *user, *tty, *mytty; 179 uid_t myuid; 180 { 181 struct utmp u; 182 time_t bestatime, atime; 183 int ufd, nloggedttys, nttys, msgsok, user_is_me; 184 char atty[UT_LINESIZE + 1]; 185 186 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 187 err(1, "utmp"); 188 189 nloggedttys = nttys = 0; 190 bestatime = 0; 191 user_is_me = 0; 192 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 193 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 194 ++nloggedttys; 195 (void)strncpy(atty, u.ut_line, UT_LINESIZE); 196 atty[UT_LINESIZE] = '\0'; 197 if (term_chk(atty, &msgsok, &atime, 0)) 198 continue; /* bad term? skip */ 199 if (myuid && !msgsok) 200 continue; /* skip ttys with msgs off */ 201 if (strcmp(atty, mytty) == 0) { 202 user_is_me = 1; 203 continue; /* don't write to yourself */ 204 } 205 ++nttys; 206 if (atime > bestatime) { 207 bestatime = atime; 208 (void)strcpy(tty, atty); 209 } 210 } 211 212 (void)close(ufd); 213 if (nloggedttys == 0) 214 errx(1, "%s is not logged in", user); 215 if (nttys == 0) { 216 if (user_is_me) { /* ok, so write to yourself! */ 217 (void)strcpy(tty, mytty); 218 return; 219 } 220 errx(1, "%s has messages disabled", user); 221 } else if (nttys > 1) { 222 warnx("%s is logged in more than once; writing to %s", user, tty); 223 } 224 } 225 226 /* 227 * term_chk - check that a terminal exists, and get the message bit 228 * and the access time 229 */ 230 int 231 term_chk(tty, msgsokP, atimeP, showerror) 232 char *tty; 233 int *msgsokP, showerror; 234 time_t *atimeP; 235 { 236 struct stat s; 237 char path[MAXPATHLEN]; 238 239 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 240 if (stat(path, &s) < 0) { 241 if (showerror) 242 warn("%s", path); 243 return(1); 244 } 245 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 246 *atimeP = s.st_atime; 247 return(0); 248 } 249 250 /* 251 * do_write - actually make the connection 252 */ 253 void 254 do_write(tty, mytty, myuid) 255 char *tty, *mytty; 256 uid_t myuid; 257 { 258 const char *login; 259 char *nows; 260 struct passwd *pwd; 261 time_t now; 262 char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 263 264 /* Determine our login name before the we reopen() stdout */ 265 if ((login = getlogin()) == NULL) { 266 if ((pwd = getpwuid(myuid))) 267 login = pwd->pw_name; 268 else 269 login = "???"; 270 } 271 272 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 273 if ((freopen(path, "w", stdout)) == NULL) 274 err(1, "%s", path); 275 276 (void)signal(SIGINT, done); 277 (void)signal(SIGHUP, done); 278 279 /* print greeting */ 280 if (gethostname(host, sizeof(host)) < 0) 281 (void)strcpy(host, "???"); 282 now = time((time_t *)NULL); 283 nows = ctime(&now); 284 nows[16] = '\0'; 285 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 286 login, host, mytty, nows + 11); 287 288 while (fgets(line, sizeof(line), stdin) != NULL) 289 wr_fputs(line); 290 } 291 292 /* 293 * done - cleanup and exit 294 */ 295 void 296 done(n) 297 int n __unused; 298 { 299 (void)printf("EOF\r\n"); 300 exit(0); 301 } 302 303 /* 304 * wr_fputs - like fputs(), but makes control characters visible and 305 * turns \n into \r\n 306 */ 307 void 308 wr_fputs(s) 309 unsigned char *s; 310 { 311 312 #define PUTC(c) if (putchar(c) == EOF) err(1, NULL); 313 314 for (; *s != '\0'; ++s) { 315 if (*s == '\n') { 316 PUTC('\r'); 317 } else if (((*s & 0x80) && *s < 0xA0) || 318 /* disable upper controls */ 319 (!isprint(*s) && !isspace(*s) && 320 *s != '\a' && *s != '\b') 321 ) { 322 if (*s & 0x80) { 323 *s &= ~0x80; 324 PUTC('M'); 325 PUTC('-'); 326 } 327 if (iscntrl(*s)) { 328 *s ^= 0x40; 329 PUTC('^'); 330 } 331 } 332 PUTC(*s); 333 } 334 return; 335 #undef PUTC 336 } 337