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 1.3 2003/10/04 20:36:55 hmp Exp $ 40 */ 41 42 #include <sys/param.h> 43 #include <sys/signal.h> 44 #include <sys/stat.h> 45 #include <sys/file.h> 46 #include <sys/time.h> 47 #include <ctype.h> 48 #include <err.h> 49 #include <locale.h> 50 #include <paths.h> 51 #include <pwd.h> 52 #include <stdio.h> 53 #include <string.h> 54 #include <unistd.h> 55 #include <utmp.h> 56 57 void done(int); 58 void do_write(char *, char *, uid_t); 59 static void usage(void); 60 int term_chk(char *, int *, time_t *, int); 61 void wr_fputs(unsigned char *s); 62 void search_utmp(char *, char *, char *, uid_t); 63 int utmp_chk(char *, char *); 64 65 int 66 main(int argc, char **argv) 67 { 68 register char *cp; 69 time_t atime; 70 uid_t myuid; 71 int msgsok, myttyfd; 72 char tty[MAXPATHLEN], *mytty; 73 74 (void)setlocale(LC_CTYPE, ""); 75 76 /* check that sender has write enabled */ 77 if (isatty(fileno(stdin))) 78 myttyfd = fileno(stdin); 79 else if (isatty(fileno(stdout))) 80 myttyfd = fileno(stdout); 81 else if (isatty(fileno(stderr))) 82 myttyfd = fileno(stderr); 83 else 84 errx(1, "can't find your tty"); 85 if (!(mytty = ttyname(myttyfd))) 86 errx(1, "can't find your tty's name"); 87 if ((cp = rindex(mytty, '/'))) 88 mytty = cp + 1; 89 if (term_chk(mytty, &msgsok, &atime, 1)) 90 exit(1); 91 if (!msgsok) 92 errx(1, "you have write permission turned off"); 93 94 myuid = getuid(); 95 96 /* check args */ 97 switch (argc) { 98 case 2: 99 search_utmp(argv[1], tty, mytty, myuid); 100 do_write(tty, mytty, myuid); 101 break; 102 case 3: 103 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV))) 104 argv[2] += strlen(_PATH_DEV); 105 if (utmp_chk(argv[1], argv[2])) 106 errx(1, "%s is not logged in on %s", argv[1], argv[2]); 107 if (term_chk(argv[2], &msgsok, &atime, 1)) 108 exit(1); 109 if (myuid && !msgsok) 110 errx(1, "%s has messages disabled on %s", argv[1], argv[2]); 111 do_write(argv[2], mytty, myuid); 112 break; 113 default: 114 usage(); 115 } 116 done(0); 117 return (0); 118 } 119 120 static void 121 usage(void) 122 { 123 (void)fprintf(stderr, "usage: write user [tty]\n"); 124 exit(1); 125 } 126 127 /* 128 * utmp_chk - checks that the given user is actually logged in on 129 * the given tty 130 */ 131 int 132 utmp_chk(char *user, char *tty) 133 { 134 struct utmp u; 135 int ufd; 136 137 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 138 return(0); /* ignore error, shouldn't happen anyway */ 139 140 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 141 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 && 142 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) { 143 (void)close(ufd); 144 return(0); 145 } 146 147 (void)close(ufd); 148 return(1); 149 } 150 151 /* 152 * search_utmp - search utmp for the "best" terminal to write to 153 * 154 * Ignores terminals with messages disabled, and of the rest, returns 155 * the one with the most recent access time. Returns as value the number 156 * of the user's terminals with messages enabled, or -1 if the user is 157 * not logged in at all. 158 * 159 * Special case for writing to yourself - ignore the terminal you're 160 * writing from, unless that's the only terminal with messages enabled. 161 */ 162 void 163 search_utmp(char *user, char *tty, char *mytty, uid_t myuid) 164 { 165 struct utmp u; 166 time_t bestatime, atime; 167 int ufd, nloggedttys, nttys, msgsok, user_is_me; 168 char atty[UT_LINESIZE + 1]; 169 170 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) 171 err(1, "utmp"); 172 173 nloggedttys = nttys = 0; 174 bestatime = 0; 175 user_is_me = 0; 176 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u)) 177 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) { 178 ++nloggedttys; 179 (void)strncpy(atty, u.ut_line, UT_LINESIZE); 180 atty[UT_LINESIZE] = '\0'; 181 if (term_chk(atty, &msgsok, &atime, 0)) 182 continue; /* bad term? skip */ 183 if (myuid && !msgsok) 184 continue; /* skip ttys with msgs off */ 185 if (strcmp(atty, mytty) == 0) { 186 user_is_me = 1; 187 continue; /* don't write to yourself */ 188 } 189 ++nttys; 190 if (atime > bestatime) { 191 bestatime = atime; 192 (void)strcpy(tty, atty); 193 } 194 } 195 196 (void)close(ufd); 197 if (nloggedttys == 0) 198 errx(1, "%s is not logged in", user); 199 if (nttys == 0) { 200 if (user_is_me) { /* ok, so write to yourself! */ 201 (void)strcpy(tty, mytty); 202 return; 203 } 204 errx(1, "%s has messages disabled", user); 205 } else if (nttys > 1) { 206 warnx("%s is logged in more than once; writing to %s", user, tty); 207 } 208 } 209 210 /* 211 * term_chk - check that a terminal exists, and get the message bit 212 * and the access time 213 */ 214 int 215 term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror) 216 { 217 struct stat s; 218 char path[MAXPATHLEN]; 219 220 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 221 if (stat(path, &s) < 0) { 222 if (showerror) 223 warn("%s", path); 224 return(1); 225 } 226 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ 227 *atimeP = s.st_atime; 228 return(0); 229 } 230 231 /* 232 * do_write - actually make the connection 233 */ 234 void 235 do_write(char *tty, char *mytty, uid_t myuid) 236 { 237 register char *login, *nows; 238 register struct passwd *pwd; 239 time_t now; 240 char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512]; 241 242 /* Determine our login name before the we reopen() stdout */ 243 if ((login = getlogin()) == NULL) { 244 if ((pwd = getpwuid(myuid))) 245 login = pwd->pw_name; 246 else 247 login = "???"; 248 } 249 250 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); 251 if ((freopen(path, "w", stdout)) == NULL) 252 err(1, "%s", path); 253 254 (void)signal(SIGINT, done); 255 (void)signal(SIGHUP, done); 256 257 /* print greeting */ 258 if (gethostname(host, sizeof(host)) < 0) 259 (void)strcpy(host, "???"); 260 now = time((time_t *)NULL); 261 nows = ctime(&now); 262 nows[16] = '\0'; 263 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 264 login, host, mytty, nows + 11); 265 266 while (fgets(line, sizeof(line), stdin) != NULL) 267 wr_fputs(line); 268 } 269 270 /* 271 * done - cleanup and exit 272 */ 273 void 274 done(int n) 275 { 276 (void)printf("EOF\r\n"); 277 exit(0); 278 } 279 280 /* 281 * wr_fputs - like fputs(), but makes control characters visible and 282 * turns \n into \r\n 283 */ 284 void 285 wr_fputs(register unsigned char *s) 286 { 287 288 #define PUTC(c) if (putchar(c) == EOF) err(1, NULL); 289 290 for (; *s != '\0'; ++s) { 291 if (*s == '\n') { 292 PUTC('\r'); 293 } else if (((*s & 0x80) && *s < 0xA0) || 294 /* disable upper controls */ 295 (!isprint(*s) && !isspace(*s) && 296 *s != '\a' && *s != '\b') 297 ) { 298 if (*s & 0x80) { 299 *s &= ~0x80; 300 PUTC('M'); 301 PUTC('-'); 302 } 303 if (iscntrl(*s)) { 304 *s ^= 0x40; 305 PUTC('^'); 306 } 307 } 308 PUTC(*s); 309 } 310 return; 311 #undef PUTC 312 } 313