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