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. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved. 33 * @(#)write.c 8.1 (Berkeley) 6/6/93 34 * $FreeBSD: src/usr.bin/write/write.c,v 1.12 1999/08/28 01:07:48 peter Exp $ 35 * $DragonFly: src/usr.bin/write/write.c,v 1.7 2005/08/30 22:02:36 liamfoy Exp $ 36 */ 37 38 #include <sys/param.h> 39 #include <sys/stat.h> 40 #include <sys/file.h> 41 42 #include <ctype.h> 43 #include <err.h> 44 #include <locale.h> 45 #include <paths.h> 46 #include <pwd.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include <string.h> 50 #include <signal.h> 51 #include <time.h> 52 #include <unistd.h> 53 #include "utmpentry.h" 54 55 static void done(int); 56 static void do_write(const char *, const char *, uid_t, int *); 57 static void usage(void); 58 static int term_chk(const char *, int *, time_t *, int); 59 static void wr_fputs(unsigned char *s); 60 static void search_utmp(const char *, char *, size_t, const char *, uid_t); 61 static int utmp_chk(const char *, const char *); 62 63 int 64 main(int argc, char **argv) 65 { 66 time_t atime; 67 uid_t myuid; 68 int msgsok, mymsgok, myttyfd; 69 char tty[MAXPATHLEN], *mytty; 70 71 setlocale(LC_CTYPE, ""); 72 73 /* check that sender has write enabled */ 74 if (isatty(fileno(stdin))) 75 myttyfd = fileno(stdin); 76 else if (isatty(fileno(stdout))) 77 myttyfd = fileno(stdout); 78 else if (isatty(fileno(stderr))) 79 myttyfd = fileno(stderr); 80 else 81 errx(1, "can't find your tty"); 82 if (!(mytty = ttyname(myttyfd))) 83 errx(1, "can't find your tty's name"); 84 if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV))) 85 mytty += strlen(_PATH_DEV); 86 if (term_chk(mytty, &mymsgok, &atime, 1)) 87 exit(1); 88 if (!mymsgok) 89 warnx("you have write permission turned off (man mesg)"); 90 91 myuid = getuid(); 92 93 /* check args */ 94 switch (argc) { 95 case 2: 96 search_utmp(argv[1], tty, sizeof tty, mytty, myuid); 97 do_write(tty, mytty, myuid, &mymsgok); 98 break; 99 case 3: 100 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV))) 101 argv[2] += strlen(_PATH_DEV); 102 if (utmp_chk(argv[1], argv[2])) 103 errx(1, "%s is not logged in on %s", argv[1], argv[2]); 104 if (term_chk(argv[2], &msgsok, &atime, 1)) 105 exit(1); 106 if (myuid && !msgsok) 107 errx(1, "%s has messages disabled on %s", argv[1], argv[2]); 108 do_write(argv[2], mytty, myuid, &mymsgok); 109 break; 110 default: 111 usage(); 112 } 113 done(0); 114 return (0); 115 } 116 117 static void 118 usage(void) 119 { 120 fprintf(stderr, "usage: write user [tty]\n"); 121 exit(1); 122 } 123 124 /* 125 * utmp_chk - checks that the given user is actually logged in on 126 * the given tty 127 */ 128 static int 129 utmp_chk(const char *user, const char *tty) 130 { 131 struct utmpentry *ep; 132 133 getutentries(NULL, &ep); 134 135 for (; ep; ep = ep->next) { 136 if (strcmp(user, ep->name) == 0 && 137 strcmp(tty, ep->line) == 0) { 138 return(0); 139 } 140 } 141 142 return(1); 143 } 144 145 /* 146 * search_utmp - search utmp for the "best" terminal to write to 147 * 148 * Ignores terminals with messages disabled, and of the rest, returns 149 * the one with the most recent access time. Returns as value the number 150 * of the user's terminals with messages enabled, or -1 if the user is 151 * not logged in at all. 152 * 153 * Special case for writing to yourself - ignore the terminal you're 154 * writing from, unless that's the only terminal with messages enabled. 155 */ 156 static void 157 search_utmp(const char *user, char *tty, size_t ttyl, const char *mytty, uid_t myuid) 158 { 159 struct utmpentry *ep; 160 time_t bestatime, atime; 161 int nloggedttys, nttys, msgsok, user_is_me; 162 163 getutentries(NULL, &ep); 164 165 nloggedttys = nttys = 0; 166 bestatime = 0; 167 user_is_me = 0; 168 for (; ep; ep = ep->next) 169 if (strcmp(user, ep->name) == 0) { 170 ++nloggedttys; 171 if (term_chk(ep->line, &msgsok, &atime, 0)) 172 continue; /* bad term? skip */ 173 if (myuid && !msgsok) 174 continue; /* skip ttys with msgs off */ 175 if (strcmp(ep->line, mytty) == 0) { 176 user_is_me = 1; 177 continue; /* don't write to yourself */ 178 } 179 ++nttys; 180 if (atime > bestatime) { 181 bestatime = atime; 182 strlcpy(tty, ep->line, ttyl); 183 } 184 } 185 186 if (nloggedttys == 0) 187 errx(1, "%s is not logged in", user); 188 if (nttys == 0) { 189 if (user_is_me) { /* ok, so write to yourself! */ 190 strlcpy(tty, mytty, ttyl); 191 return; 192 } 193 errx(1, "%s has messages disabled", user); 194 } else if (nttys > 1) { 195 warnx("%s is logged in more than once; writing to %s", user, tty); 196 } 197 } 198 199 /* 200 * term_chk - check that a terminal exists, and get the message bit 201 * and the access time 202 */ 203 static int 204 term_chk(const char *tty, int *msgsokP, time_t *atimeP, int showerror) 205 { 206 struct stat s; 207 char path[MAXPATHLEN]; 208 209 snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 210 if (stat(path, &s) < 0) { 211 if (showerror) 212 warn("%s", path); 213 return(1); 214 } 215 *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */ 216 *atimeP = s.st_atime; 217 return(0); 218 } 219 220 /* 221 * do_write - actually make the connection 222 */ 223 static void 224 do_write(const char *tty, const char *mytty, uid_t myuid, int *mymsgok) 225 { 226 const char *login; 227 char *nows; 228 struct passwd *pwd; 229 time_t now; 230 char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 231 232 /* Determine our login name before we reopen() stdout */ 233 if ((login = getlogin()) == NULL) { 234 if ((pwd = getpwuid(myuid))) 235 login = pwd->pw_name; 236 else 237 login = "???"; 238 } 239 240 snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 241 if ((freopen(path, "w", stdout)) == NULL) 242 err(1, "%s", path); 243 244 signal(SIGINT, done); 245 signal(SIGHUP, done); 246 247 /* print greeting */ 248 if (gethostname(host, sizeof(host)) < 0) 249 strlcpy(host, "???", sizeof host); 250 now = time(NULL); 251 nows = ctime(&now); 252 nows[16] = '\0'; 253 printf("\r\n\007\007\007Message from %s@%s on %s at %s (%s %s replies)...\r\n", 254 login, host, mytty, nows + 11, login, *mymsgok == 0 ? "does not accept" : "accepts"); 255 256 while (fgets(line, sizeof(line), stdin) != NULL) 257 wr_fputs(line); 258 } 259 260 /* 261 * done - cleanup and exit 262 */ 263 static void 264 done(__unused int n) 265 { 266 printf("EOF\r\n"); 267 exit(0); 268 } 269 270 /* 271 * wr_fputs - like fputs(), but makes control characters visible and 272 * turns \n into \r\n 273 */ 274 static void 275 wr_fputs(unsigned char *s) 276 { 277 278 #define PUTC(c) if (putchar(c) == EOF) err(1, NULL); 279 280 for (; *s != '\0'; ++s) { 281 if (*s == '\n') { 282 PUTC('\r'); 283 } else if (((*s & 0x80) && *s < 0xA0) || 284 /* disable upper controls */ 285 (!isprint(*s) && !isspace(*s) && 286 *s != '\a' && *s != '\b') 287 ) { 288 if (*s & 0x80) { 289 *s &= ~0x80; 290 PUTC('M'); 291 PUTC('-'); 292 } 293 if (iscntrl(*s)) { 294 *s ^= 0x40; 295 PUTC('^'); 296 } 297 } 298 PUTC(*s); 299 } 300 return; 301 #undef PUTC 302 } 303