write.c revision 1.14
1 /* $NetBSD: write.c,v 1.14 1998/08/25 20:59:43 ross Exp $ */ 2 3 /* 4 * Copyright (c) 1989, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #ifndef lint 41 __COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\ 42 The Regents of the University of California. All rights reserved.\n"); 43 #endif /* not lint */ 44 45 #ifndef lint 46 #if 0 47 static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95"; 48 #else 49 __RCSID("$NetBSD: write.c,v 1.14 1998/08/25 20:59:43 ross Exp $"); 50 #endif 51 #endif /* not lint */ 52 53 #include <sys/types.h> 54 #include <sys/param.h> 55 #include <sys/stat.h> 56 #include <ctype.h> 57 #include <stdio.h> 58 #include <string.h> 59 #include <signal.h> 60 #include <time.h> 61 #include <fcntl.h> 62 #include <pwd.h> 63 #include <unistd.h> 64 #include <utmp.h> 65 #include <err.h> 66 67 void done __P((int)); 68 void do_write __P((char *, char *, uid_t)); 69 void wr_fputs __P((char *)); 70 void search_utmp __P((char *, char *, char *, uid_t, int)); 71 int term_chk __P((char *, int *, time_t *, int)); 72 int utmp_chk __P((char *, char *)); 73 int main __P((int, char **)); 74 75 int 76 main(argc, argv) 77 int argc; 78 char **argv; 79 { 80 char *cp; 81 time_t atime; 82 uid_t myuid; 83 int msgsok, myttyfd; 84 char tty[MAXPATHLEN], *mytty; 85 86 /* check that sender has write enabled */ 87 if (isatty(fileno(stdin))) 88 myttyfd = fileno(stdin); 89 else if (isatty(fileno(stdout))) 90 myttyfd = fileno(stdout); 91 else if (isatty(fileno(stderr))) 92 myttyfd = fileno(stderr); 93 else 94 errx(1, "can't find your tty"); 95 if (!(mytty = ttyname(myttyfd))) 96 errx(1, "can't find your tty's name"); 97 if ((cp = strrchr(mytty, '/')) != NULL) 98 mytty = cp + 1; 99 if (term_chk(mytty, &msgsok, &atime, 1)) 100 exit(1); 101 if (!msgsok) { 102 (void)fprintf(stderr, 103 "warning: you have write permission turned off; " 104 "no reply possible\n"); 105 } 106 107 myuid = getuid(); 108 109 /* check args */ 110 switch (argc) { 111 case 2: 112 search_utmp(argv[1], tty, mytty, myuid, sizeof tty); 113 do_write(tty, mytty, myuid); 114 break; 115 case 3: 116 if (!strncmp(argv[2], "/dev/", 5)) 117 argv[2] += 5; 118 if (utmp_chk(argv[1], argv[2])) 119 errx(1, "%s is not logged in on %s", 120 argv[1], argv[2]); 121 if (term_chk(argv[2], &msgsok, &atime, 1)) 122 exit(1); 123 if (myuid && !msgsok) 124 errx(1, "%s has messages disabled on %s", 125 argv[1], argv[2]); 126 do_write(argv[2], mytty, myuid); 127 break; 128 default: 129 (void)fprintf(stderr, "usage: write user [tty]\n"); 130 exit(1); 131 } 132 done(0); 133 /* NOTREACHED */ 134 #ifdef __GNUC__ 135 return (0); 136 #endif 137 } 138 139 /* 140 * utmp_chk - checks that the given user is actually logged in on 141 * the given tty 142 */ 143 int 144 utmp_chk(user, tty) 145 char *user, *tty; 146 { 147 struct utmp u; 148 int ufd; 149 150 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 151 return(0); /* ignore error, shouldn't happen anyway */ 152 153 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 154 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 155 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 156 (void)close(ufd); 157 return(0); 158 } 159 160 (void)close(ufd); 161 return(1); 162 } 163 164 /* 165 * search_utmp - search utmp for the "best" terminal to write to 166 * 167 * Ignores terminals with messages disabled, and of the rest, returns 168 * the one with the most recent access time. Returns as value the number 169 * of the user's terminals with messages enabled, or -1 if the user is 170 * not logged in at all. 171 * 172 * Special case for writing to yourself - ignore the terminal you're 173 * writing from, unless that's the only terminal with messages enabled. 174 */ 175 void 176 search_utmp(user, tty, mytty, myuid, ttylen) 177 char *user, *tty, *mytty; 178 uid_t myuid; 179 int ttylen; 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, "%s", _PATH_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)strncpy(tty, atty, ttylen - 1); 209 tty[ttylen - 1] = '\0'; 210 } 211 } 212 213 (void)close(ufd); 214 if (nloggedttys == 0) 215 errx(1, "%s is not logged in", user); 216 if (nttys == 0) { 217 if (user_is_me) { /* ok, so write to yourself! */ 218 (void)strncpy(tty, mytty, ttylen - 1); 219 tty[ttylen - 1] = '\0'; 220 return; 221 } 222 errx(1, "%s has messages disabled", user); 223 } else if (nttys > 1) 224 warnx("%s is logged in more than once; writing to %s", 225 user, tty); 226 } 227 228 /* 229 * term_chk - check that a terminal exists, and get the message bit 230 * and the access time 231 */ 232 int 233 term_chk(tty, msgsokP, atimeP, showerror) 234 char *tty; 235 int *msgsokP, showerror; 236 time_t *atimeP; 237 { 238 struct stat s; 239 char path[MAXPATHLEN]; 240 241 (void)snprintf(path, sizeof path, "/dev/%s", tty); 242 if (stat(path, &s) < 0) { 243 if (showerror) 244 warn("%s", path); 245 return(1); 246 } 247 *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */ 248 *atimeP = s.st_atime; 249 return(0); 250 } 251 252 /* 253 * do_write - actually make the connection 254 */ 255 void 256 do_write(tty, mytty, myuid) 257 char *tty, *mytty; 258 uid_t myuid; 259 { 260 const char *login; 261 char *nows; 262 struct passwd *pwd; 263 time_t now; 264 char path[MAXPATHLEN], host[MAXHOSTNAMELEN + 1], line[512]; 265 266 /* Determine our login name before the we reopen() stdout */ 267 if ((login = getlogin()) == NULL) { 268 if ((pwd = getpwuid(myuid)) != NULL) 269 login = pwd->pw_name; 270 else login = "???"; 271 } 272 (void)snprintf(path, sizeof path, "/dev/%s", 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)strncpy(host, "???", sizeof(host) - 1); 282 else 283 host[sizeof(host) - 1] = '\0'; 284 now = time((time_t *)NULL); 285 nows = ctime(&now); 286 nows[16] = '\0'; 287 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 288 login, host, mytty, nows + 11); 289 290 while (fgets(line, sizeof(line), stdin) != NULL) 291 wr_fputs(line); 292 } 293 294 /* 295 * done - cleanup and exit 296 */ 297 void 298 done(dummy) 299 int dummy; 300 { 301 302 (void)printf("EOF\r\n"); 303 exit(0); 304 } 305 306 /* 307 * wr_fputs - like fputs(), but makes control characters visible and 308 * turns \n into \r\n 309 */ 310 void 311 wr_fputs(s) 312 char *s; 313 { 314 char c; 315 316 #define PUTC(c) if (putchar(c) == EOF) goto err; 317 318 for (; *s != '\0'; ++s) { 319 c = toascii(*s); 320 if (c == '\n') { 321 PUTC('\r'); 322 PUTC('\n'); 323 } else if (!isprint(c) && !isspace(c) && c != '\007') { 324 PUTC('^'); 325 PUTC(c^0x40); /* DEL to ?, others to alpha */ 326 } else 327 PUTC(c); 328 } 329 return; 330 331 err: err(1, "%s", ""); 332 #undef PUTC 333 } 334
Indexes created Sun Sep 21 20:09:37 GMT 2025