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 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved. 37 * @(#)write.c 8.1 (Berkeley) 6/6/93 38 * $FreeBSD: src/usr.bin/write/write.c,v 1.12 1999/08/28 01:07:48 peter Exp $ 39 * $DragonFly: src/usr.bin/write/write.c,v 1.7 2005/08/30 22:02:36 liamfoy Exp $ 40 */ 41 42 #include <sys/param.h> 43 #include <sys/stat.h> 44 #include <sys/file.h> 45 46 #include <ctype.h> 47 #include <err.h> 48 #include <locale.h> 49 #include <paths.h> 50 #include <pwd.h> 51 #include <stdio.h> 52 #include <stdlib.h> 53 #include <string.h> 54 #include <signal.h> 55 #include <time.h> 56 #include <unistd.h> 57 #include <utmp.h> 58 59 static void done(int); 60 static void do_write(const char *, const char *, uid_t, int *); 61 static void usage(void); 62 static int term_chk(const char *, int *, time_t *, int); 63 static void wr_fputs(unsigned char *s); 64 static void search_utmp(const char *, char *, size_t, const char *, uid_t); 65 static int utmp_chk(const char *, const char *); 66 67 int 68 main(int argc, char **argv) 69 { 70 char *cp; 71 time_t atime; 72 uid_t myuid; 73 int msgsok, mymsgok, myttyfd; 74 char tty[MAXPATHLEN], *mytty; 75 76 setlocale(LC_CTYPE, ""); 77 78 /* check that sender has write enabled */ 79 if (isatty(fileno(stdin))) 80 myttyfd = fileno(stdin); 81 else if (isatty(fileno(stdout))) 82 myttyfd = fileno(stdout); 83 else if (isatty(fileno(stderr))) 84 myttyfd = fileno(stderr); 85 else 86 errx(1, "can't find your tty"); 87 if (!(mytty = ttyname(myttyfd))) 88 errx(1, "can't find your tty's name"); 89 if ((cp = strrchr(mytty, '/'))) 90 mytty = cp + 1; 91 if (term_chk(mytty, &mymsgok, &atime, 1)) 92 exit(1); 93 if (!mymsgok) 94 warnx("you have write permission turned off (man mesg)"); 95 96 myuid = getuid(); 97 98 /* check args */ 99 switch (argc) { 100 case 2: 101 search_utmp(argv[1], tty, sizeof tty, mytty, myuid); 102 do_write(tty, mytty, myuid, &mymsgok); 103 break; 104 case 3: 105 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV))) 106 argv[2] += strlen(_PATH_DEV); 107 if (utmp_chk(argv[1], argv[2])) 108 errx(1, "%s is not logged in on %s", argv[1], argv[2]); 109 if (term_chk(argv[2], &msgsok, &atime, 1)) 110 exit(1); 111 if (myuid && !msgsok) 112 errx(1, "%s has messages disabled on %s", argv[1], argv[2]); 113 do_write(argv[2], mytty, myuid, &mymsgok); 114 break; 115 default: 116 usage(); 117 } 118 done(0); 119 return (0); 120 } 121 122 static void 123 usage(void) 124 { 125 fprintf(stderr, "usage: write user [tty]\n"); 126 exit(1); 127 } 128 129 /* 130 * utmp_chk - checks that the given user is actually logged in on 131 * the given tty 132 */ 133 static int 134 utmp_chk(const char *user, const char *tty) 135 { 136 struct utmp u; 137 int ufd; 138 139 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 140 err(1, "open failed: %s\n", _PATH_UTMP); 141 142 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) { 143 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 144 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 145 close(ufd); 146 return(0); 147 } 148 } 149 150 close(ufd); 151 return(1); 152 } 153 154 /* 155 * search_utmp - search utmp for the "best" terminal to write to 156 * 157 * Ignores terminals with messages disabled, and of the rest, returns 158 * the one with the most recent access time. Returns as value the number 159 * of the user's terminals with messages enabled, or -1 if the user is 160 * not logged in at all. 161 * 162 * Special case for writing to yourself - ignore the terminal you're 163 * writing from, unless that's the only terminal with messages enabled. 164 */ 165 static void 166 search_utmp(const char *user, char *tty, size_t ttyl, const char *mytty, uid_t myuid) 167 { 168 struct utmp u; 169 time_t bestatime, atime; 170 int ufd, nloggedttys, nttys, msgsok, user_is_me; 171 char atty[UT_LINESIZE + 1]; 172 173 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 174 err(1, "open failed: %s", _PATH_UTMP); 175 176 nloggedttys = nttys = 0; 177 bestatime = 0; 178 user_is_me = 0; 179 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 180 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 181 ++nloggedttys; 182 strlcpy(atty, u.ut_line, ttyl); 183 if (term_chk(atty, &msgsok, &atime, 0)) 184 continue; /* bad term? skip */ 185 if (myuid && !msgsok) 186 continue; /* skip ttys with msgs off */ 187 if (strcmp(atty, mytty) == 0) { 188 user_is_me = 1; 189 continue; /* don't write to yourself */ 190 } 191 ++nttys; 192 if (atime > bestatime) { 193 bestatime = atime; 194 strlcpy(tty, atty, ttyl); 195 } 196 } 197 198 close(ufd); 199 if (nloggedttys == 0) 200 errx(1, "%s is not logged in", user); 201 if (nttys == 0) { 202 if (user_is_me) { /* ok, so write to yourself! */ 203 strlcpy(tty, mytty, ttyl); 204 return; 205 } 206 errx(1, "%s has messages disabled", user); 207 } else if (nttys > 1) { 208 warnx("%s is logged in more than once; writing to %s", user, tty); 209 } 210 } 211 212 /* 213 * term_chk - check that a terminal exists, and get the message bit 214 * and the access time 215 */ 216 static int 217 term_chk(const char *tty, int *msgsokP, time_t *atimeP, int showerror) 218 { 219 struct stat s; 220 char path[MAXPATHLEN]; 221 222 snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 223 if (stat(path, &s) < 0) { 224 if (showerror) 225 warn("%s", path); 226 return(1); 227 } 228 *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */ 229 *atimeP = s.st_atime; 230 return(0); 231 } 232 233 /* 234 * do_write - actually make the connection 235 */ 236 static void 237 do_write(const char *tty, const char *mytty, uid_t myuid, int *mymsgok) 238 { 239 const char *login; 240 char *nows; 241 struct passwd *pwd; 242 time_t now; 243 char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 244 245 /* Determine our login name before we reopen() stdout */ 246 if ((login = getlogin()) == NULL) { 247 if ((pwd = getpwuid(myuid))) 248 login = pwd->pw_name; 249 else 250 login = "???"; 251 } 252 253 snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 254 if ((freopen(path, "w", stdout)) == NULL) 255 err(1, "%s", path); 256 257 signal(SIGINT, done); 258 signal(SIGHUP, done); 259 260 /* print greeting */ 261 if (gethostname(host, sizeof(host)) < 0) 262 strlcpy(host, "???", sizeof host); 263 now = time((time_t *)NULL); 264 nows = ctime(&now); 265 nows[16] = '\0'; 266 printf("\r\n\007\007\007Message from %s@%s on %s at %s (%s %s replies)...\r\n", 267 login, host, mytty, nows + 11, login, *mymsgok == 0 ? "does not accept" : "accepts"); 268 269 while (fgets(line, sizeof(line), stdin) != NULL) 270 wr_fputs(line); 271 } 272 273 /* 274 * done - cleanup and exit 275 */ 276 static void 277 done(__unused int n) 278 { 279 printf("EOF\r\n"); 280 exit(0); 281 } 282 283 /* 284 * wr_fputs - like fputs(), but makes control characters visible and 285 * turns \n into \r\n 286 */ 287 static void 288 wr_fputs(unsigned char *s) 289 { 290 291 #define PUTC(c) if (putchar(c) == EOF) err(1, NULL); 292 293 for (; *s != '\0'; ++s) { 294 if (*s == '\n') { 295 PUTC('\r'); 296 } else if (((*s & 0x80) && *s < 0xA0) || 297 /* disable upper controls */ 298 (!isprint(*s) && !isspace(*s) && 299 *s != '\a' && *s != '\b') 300 ) { 301 if (*s & 0x80) { 302 *s &= ~0x80; 303 PUTC('M'); 304 PUTC('-'); 305 } 306 if (iscntrl(*s)) { 307 *s ^= 0x40; 308 PUTC('^'); 309 } 310 } 311 PUTC(*s); 312 } 313 return; 314 #undef PUTC 315 } 316