write.c revision 1.18
1 /* $NetBSD: write.c,v 1.18 2001/01/03 13:14:26 mjl 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 1.18 2001/01/03 13:14:26 mjl 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 <stdlib.h> 59 #include <string.h> 60 #include <signal.h> 61 #include <time.h> 62 #include <fcntl.h> 63 #include <paths.h> 64 #include <pwd.h> 65 #include <unistd.h> 66 #include <utmp.h> 67 #include <err.h> 68 69 void done __P((int)); 70 void do_write __P((char *, char *, uid_t)); 71 void wr_fputs __P((char *)); 72 void search_utmp __P((char *, char *, char *, uid_t, int)); 73 int term_chk __P((char *, int *, time_t *, int)); 74 int utmp_chk __P((char *, char *)); 75 int main __P((int, char **)); 76 77 int 78 main(argc, argv) 79 int argc; 80 char **argv; 81 { 82 char *cp; 83 time_t atime; 84 uid_t myuid; 85 int msgsok, myttyfd; 86 char tty[MAXPATHLEN], *mytty; 87 88 /* check that sender has write enabled */ 89 if (isatty(fileno(stdin))) 90 myttyfd = fileno(stdin); 91 else if (isatty(fileno(stdout))) 92 myttyfd = fileno(stdout); 93 else if (isatty(fileno(stderr))) 94 myttyfd = fileno(stderr); 95 else 96 errx(1, "can't find your tty"); 97 if (!(mytty = ttyname(myttyfd))) 98 errx(1, "can't find your tty's name"); 99 if ((cp = strrchr(mytty, '/')) != NULL) 100 mytty = cp + 1; 101 if (term_chk(mytty, &msgsok, &atime, 1)) 102 exit(1); 103 if (!msgsok) { 104 (void)fprintf(stderr, 105 "warning: you have write permission turned off; " 106 "no reply possible\n"); 107 } 108 109 myuid = getuid(); 110 111 /* check args */ 112 switch (argc) { 113 case 2: 114 search_utmp(argv[1], tty, mytty, myuid, sizeof tty); 115 do_write(tty, mytty, myuid); 116 break; 117 case 3: 118 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV))) 119 argv[2] += strlen(_PATH_DEV); 120 if (utmp_chk(argv[1], argv[2])) 121 errx(1, "%s is not logged in on %s", 122 argv[1], argv[2]); 123 if (term_chk(argv[2], &msgsok, &atime, 1)) 124 exit(1); 125 if (myuid && !msgsok) 126 errx(1, "%s has messages disabled on %s", 127 argv[1], argv[2]); 128 do_write(argv[2], mytty, myuid); 129 break; 130 default: 131 (void)fprintf(stderr, "usage: write user [tty]\n"); 132 exit(1); 133 } 134 done(0); 135 /* NOTREACHED */ 136 #ifdef __GNUC__ 137 return (0); 138 #endif 139 } 140 141 /* 142 * utmp_chk - checks that the given user is actually logged in on 143 * the given tty 144 */ 145 int 146 utmp_chk(user, tty) 147 char *user, *tty; 148 { 149 struct utmp u; 150 int ufd; 151 152 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 153 return(0); /* ignore error, shouldn't happen anyway */ 154 155 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 156 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 157 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 158 (void)close(ufd); 159 return(0); 160 } 161 162 (void)close(ufd); 163 return(1); 164 } 165 166 /* 167 * search_utmp - search utmp for the "best" terminal to write to 168 * 169 * Ignores terminals with messages disabled, and of the rest, returns 170 * the one with the most recent access time. Returns as value the number 171 * of the user's terminals with messages enabled, or -1 if the user is 172 * not logged in at all. 173 * 174 * Special case for writing to yourself - ignore the terminal you're 175 * writing from, unless that's the only terminal with messages enabled. 176 */ 177 void 178 search_utmp(user, tty, mytty, myuid, ttylen) 179 char *user, *tty, *mytty; 180 uid_t myuid; 181 int ttylen; 182 { 183 struct utmp u; 184 time_t bestatime, atime; 185 int ufd, nloggedttys, nttys, msgsok, user_is_me; 186 char atty[UT_LINESIZE + 1]; 187 188 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 189 err(1, "%s", _PATH_UTMP); 190 191 nloggedttys = nttys = 0; 192 bestatime = 0; 193 user_is_me = 0; 194 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 195 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 196 ++nloggedttys; 197 (void)strncpy(atty, u.ut_line, UT_LINESIZE); 198 atty[UT_LINESIZE] = '\0'; 199 if (term_chk(atty, &msgsok, &atime, 0)) 200 continue; /* bad term? skip */ 201 if (myuid && !msgsok) 202 continue; /* skip ttys with msgs off */ 203 if (strcmp(atty, mytty) == 0) { 204 user_is_me = 1; 205 continue; /* don't write to yourself */ 206 } 207 ++nttys; 208 if (atime > bestatime) { 209 bestatime = atime; 210 (void)strncpy(tty, atty, ttylen - 1); 211 tty[ttylen - 1] = '\0'; 212 } 213 } 214 215 (void)close(ufd); 216 if (nloggedttys == 0) 217 errx(1, "%s is not logged in", user); 218 if (nttys == 0) { 219 if (user_is_me) { /* ok, so write to yourself! */ 220 (void)strncpy(tty, mytty, ttylen - 1); 221 tty[ttylen - 1] = '\0'; 222 return; 223 } 224 errx(1, "%s has messages disabled", user); 225 } else if (nttys > 1) 226 warnx("%s is logged in more than once; writing to %s", 227 user, tty); 228 } 229 230 /* 231 * term_chk - check that a terminal exists, and get the message bit 232 * and the access time 233 */ 234 int 235 term_chk(tty, msgsokP, atimeP, showerror) 236 char *tty; 237 int *msgsokP, showerror; 238 time_t *atimeP; 239 { 240 struct stat s; 241 char path[MAXPATHLEN]; 242 243 (void)snprintf(path, sizeof path, _PATH_DEV "%s", tty); 244 if (stat(path, &s) < 0) { 245 if (showerror) 246 warn("%s", path); 247 return(1); 248 } 249 *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */ 250 *atimeP = s.st_atime; 251 return(0); 252 } 253 254 /* 255 * do_write - actually make the connection 256 */ 257 void 258 do_write(tty, mytty, myuid) 259 char *tty, *mytty; 260 uid_t myuid; 261 { 262 const char *login; 263 char *nows; 264 struct passwd *pwd; 265 time_t now; 266 char path[MAXPATHLEN], host[MAXHOSTNAMELEN + 1], line[512]; 267 268 /* Determine our login name before the we reopen() stdout */ 269 if ((login = getlogin()) == NULL) { 270 if ((pwd = getpwuid(myuid)) != NULL) 271 login = pwd->pw_name; 272 else login = "???"; 273 } 274 (void)snprintf(path, sizeof path, _PATH_DEV "%s", tty); 275 if ((freopen(path, "w", stdout)) == NULL) 276 err(1, "%s", path); 277 278 (void)signal(SIGINT, done); 279 (void)signal(SIGHUP, done); 280 281 /* print greeting */ 282 if (gethostname(host, sizeof(host)) < 0) 283 (void)strncpy(host, "???", sizeof(host) - 1); 284 else 285 host[sizeof(host) - 1] = '\0'; 286 now = time((time_t *)NULL); 287 nows = ctime(&now); 288 nows[16] = '\0'; 289 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 290 login, host, mytty, nows + 11); 291 292 while (fgets(line, sizeof(line), stdin) != NULL) 293 wr_fputs(line); 294 } 295 296 /* 297 * done - cleanup and exit 298 */ 299 void 300 done(dummy) 301 int dummy; 302 { 303 304 (void)printf("EOF\r\n"); 305 exit(0); 306 } 307 308 /* 309 * wr_fputs - like fputs(), but makes control characters visible and 310 * turns \n into \r\n 311 */ 312 void 313 wr_fputs(s) 314 char *s; 315 { 316 char c; 317 318 #define PUTC(c) if (putchar(c) == EOF) goto err; 319 320 for (; *s != '\0'; ++s) { 321 c = toascii(*s); 322 if (c == '\n') { 323 PUTC('\r'); 324 PUTC('\n'); 325 } else if (!isprint((unsigned char)c) && 326 !isspace((unsigned char)c) && c != '\007') { 327 PUTC('^'); 328 PUTC(c^0x40); /* DEL to ?, others to alpha */ 329 } else 330 PUTC(c); 331 } 332 return; 333 334 err: err(1, NULL); 335 #undef PUTC 336 } 337
Indexes created Thu Sep 25 16:09:42 GMT 2025