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 37 #ifndef lint 38 static const char copyright[] = 39 "@(#) Copyright (c) 1989, 1993\n\ 40 The Regents of the University of California. All rights reserved.\n"; 41 #endif 42 43 #if 0 44 #ifndef lint 45 static char sccsid[] = "@(#)write.c 8.1 (Berkeley) 6/6/93"; 46 #endif 47 #endif 48 49 #include <sys/cdefs.h> 50 __FBSDID("$FreeBSD$"); 51 52 #include <sys/param.h> 53 #include <sys/signal.h> 54 #include <sys/stat.h> 55 #include <sys/file.h> 56 #include <sys/time.h> 57 #include <ctype.h> 58 #include <err.h> 59 #include <locale.h> 60 #include <paths.h> 61 #include <pwd.h> 62 #include <stdio.h> 63 #include <stdlib.h> 64 #include <string.h> 65 #include <unistd.h> 66 #include <utmpx.h> 67 68 void done(int); 69 void do_write(char *, char *, uid_t); 70 static void usage(void); 71 int term_chk(char *, int *, time_t *, int); 72 void wr_fputs(unsigned char *s); 73 void search_utmp(char *, char *, char *, uid_t); 74 int utmp_chk(char *, char *); 75 76 int 77 main(int argc, char **argv) 78 { 79 time_t atime; 80 uid_t myuid; 81 int msgsok, myttyfd; 82 char tty[MAXPATHLEN], *mytty; 83 84 (void)setlocale(LC_CTYPE, ""); 85 86 while (getopt(argc, argv, "") != -1) 87 usage(); 88 argc -= optind; 89 argv += optind; 90 91 /* check that sender has write enabled */ 92 if (isatty(fileno(stdin))) 93 myttyfd = fileno(stdin); 94 else if (isatty(fileno(stdout))) 95 myttyfd = fileno(stdout); 96 else if (isatty(fileno(stderr))) 97 myttyfd = fileno(stderr); 98 else 99 errx(1, "can't find your tty"); 100 if (!(mytty = ttyname(myttyfd))) 101 errx(1, "can't find your tty's name"); 102 if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV))) 103 mytty += strlen(_PATH_DEV); 104 if (term_chk(mytty, &msgsok, &atime, 1)) 105 exit(1); 106 if (!msgsok) 107 errx(1, "you have write permission turned off"); 108 109 myuid = getuid(); 110 111 /* check args */ 112 switch (argc) { 113 case 1: 114 search_utmp(argv[0], tty, mytty, myuid); 115 do_write(tty, mytty, myuid); 116 break; 117 case 2: 118 if (!strncmp(argv[1], _PATH_DEV, strlen(_PATH_DEV))) 119 argv[1] += strlen(_PATH_DEV); 120 if (utmp_chk(argv[0], argv[1])) 121 errx(1, "%s is not logged in on %s", argv[0], argv[1]); 122 if (term_chk(argv[1], &msgsok, &atime, 1)) 123 exit(1); 124 if (myuid && !msgsok) 125 errx(1, "%s has messages disabled on %s", argv[0], argv[1]); 126 do_write(argv[1], mytty, myuid); 127 break; 128 default: 129 usage(); 130 } 131 done(0); 132 return (0); 133 } 134 135 static void 136 usage(void) 137 { 138 (void)fprintf(stderr, "usage: write user [tty]\n"); 139 exit(1); 140 } 141 142 /* 143 * utmp_chk - checks that the given user is actually logged in on 144 * the given tty 145 */ 146 int 147 utmp_chk(char *user, char *tty) 148 { 149 struct utmpx lu, *u; 150 151 strncpy(lu.ut_line, tty, sizeof lu.ut_line); 152 setutxent(); 153 while ((u = getutxline(&lu)) != NULL) 154 if (u->ut_type == USER_PROCESS && 155 strcmp(user, u->ut_user) == 0) { 156 endutxent(); 157 return(0); 158 } 159 endutxent(); 160 return(1); 161 } 162 163 /* 164 * search_utmp - search utmp for the "best" terminal to write to 165 * 166 * Ignores terminals with messages disabled, and of the rest, returns 167 * the one with the most recent access time. Returns as value the number 168 * of the user's terminals with messages enabled, or -1 if the user is 169 * not logged in at all. 170 * 171 * Special case for writing to yourself - ignore the terminal you're 172 * writing from, unless that's the only terminal with messages enabled. 173 */ 174 void 175 search_utmp(char *user, char *tty, char *mytty, uid_t myuid) 176 { 177 struct utmpx *u; 178 time_t bestatime, atime; 179 int nloggedttys, nttys, msgsok, user_is_me; 180 181 nloggedttys = nttys = 0; 182 bestatime = 0; 183 user_is_me = 0; 184 185 setutxent(); 186 while ((u = getutxent()) != NULL) 187 if (u->ut_type == USER_PROCESS && 188 strcmp(user, u->ut_user) == 0) { 189 ++nloggedttys; 190 if (term_chk(u->ut_line, &msgsok, &atime, 0)) 191 continue; /* bad term? skip */ 192 if (myuid && !msgsok) 193 continue; /* skip ttys with msgs off */ 194 if (strcmp(u->ut_line, mytty) == 0) { 195 user_is_me = 1; 196 continue; /* don't write to yourself */ 197 } 198 ++nttys; 199 if (atime > bestatime) { 200 bestatime = atime; 201 (void)strlcpy(tty, u->ut_line, MAXPATHLEN); 202 } 203 } 204 endutxent(); 205 206 if (nloggedttys == 0) 207 errx(1, "%s is not logged in", user); 208 if (nttys == 0) { 209 if (user_is_me) { /* ok, so write to yourself! */ 210 (void)strlcpy(tty, mytty, MAXPATHLEN); 211 return; 212 } 213 errx(1, "%s has messages disabled", user); 214 } else if (nttys > 1) { 215 warnx("%s is logged in more than once; writing to %s", user, tty); 216 } 217 } 218 219 /* 220 * term_chk - check that a terminal exists, and get the message bit 221 * and the access time 222 */ 223 int 224 term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror) 225 { 226 struct stat s; 227 char path[MAXPATHLEN]; 228 229 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 230 if (stat(path, &s) < 0) { 231 if (showerror) 232 warn("%s", path); 233 return(1); 234 } 235 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 236 *atimeP = s.st_atime; 237 return(0); 238 } 239 240 /* 241 * do_write - actually make the connection 242 */ 243 void 244 do_write(char *tty, char *mytty, uid_t myuid) 245 { 246 const char *login; 247 char *nows; 248 struct passwd *pwd; 249 time_t now; 250 char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 251 252 /* Determine our login name before we reopen() stdout */ 253 if ((login = getlogin()) == NULL) { 254 if ((pwd = getpwuid(myuid))) 255 login = pwd->pw_name; 256 else 257 login = "???"; 258 } 259 260 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 261 if ((freopen(path, "w", stdout)) == NULL) 262 err(1, "%s", path); 263 264 (void)signal(SIGINT, done); 265 (void)signal(SIGHUP, done); 266 267 /* print greeting */ 268 if (gethostname(host, sizeof(host)) < 0) 269 (void)strcpy(host, "???"); 270 now = time((time_t *)NULL); 271 nows = ctime(&now); 272 nows[16] = '\0'; 273 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 274 login, host, mytty, nows + 11); 275 276 while (fgets(line, sizeof(line), stdin) != NULL) 277 wr_fputs(line); 278 } 279 280 /* 281 * done - cleanup and exit 282 */ 283 void 284 done(int n __unused) 285 { 286 (void)printf("EOF\r\n"); 287 exit(0); 288 } 289 290 /* 291 * wr_fputs - like fputs(), but makes control characters visible and 292 * turns \n into \r\n 293 */ 294 void 295 wr_fputs(unsigned char *s) 296 { 297 298 #define PUTC(c) if (putchar(c) == EOF) err(1, NULL); 299 300 for (; *s != '\0'; ++s) { 301 if (*s == '\n') { 302 PUTC('\r'); 303 } else if (((*s & 0x80) && *s < 0xA0) || 304 /* disable upper controls */ 305 (!isprint(*s) && !isspace(*s) && 306 *s != '\a' && *s != '\b') 307 ) { 308 if (*s & 0x80) { 309 *s &= ~0x80; 310 PUTC('M'); 311 PUTC('-'); 312 } 313 if (iscntrl(*s)) { 314 *s ^= 0x40; 315 PUTC('^'); 316 } 317 } 318 PUTC(*s); 319 } 320 return; 321 #undef PUTC 322 } 323