write.c revision 1.20
1 /* $NetBSD: write.c,v 1.20 2002/08/02 01:59:44 christos Exp $ */ 2 3 /* 4 * Copyright (c) 1989, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #ifndef lint 41 __COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\ 42 The Regents of the University of California. All rights reserved.\n"); 43 #endif /* not lint */ 44 45 #ifndef lint 46 #if 0 47 static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95"; 48 #else 49 __RCSID("$NetBSD: write.c,v 1.20 2002/08/02 01:59:44 christos Exp $"); 50 #endif 51 #endif /* not lint */ 52 53 #include <sys/types.h> 54 #include <sys/param.h> 55 #include <sys/stat.h> 56 #include <ctype.h> 57 #include <stdio.h> 58 #include <stdlib.h> 59 #include <string.h> 60 #include <signal.h> 61 #include <time.h> 62 #include <fcntl.h> 63 #include <paths.h> 64 #include <pwd.h> 65 #include <unistd.h> 66 #include <err.h> 67 68 #include "utmpentry.h" 69 70 void done(int); 71 void do_write(const char *, const char *, const uid_t); 72 void wr_fputs(char *); 73 void search_utmp(char *, char *, char *, uid_t, int); 74 int term_chk(const char *, int *, time_t *, int); 75 int utmp_chk(const char *, const char *); 76 int main(int, char **); 77 78 int 79 main(int argc, char **argv) 80 { 81 char *cp; 82 time_t atime; 83 uid_t myuid; 84 int msgsok, myttyfd; 85 char tty[MAXPATHLEN], *mytty; 86 87 /* check that sender has write enabled */ 88 if (isatty(fileno(stdin))) 89 myttyfd = fileno(stdin); 90 else if (isatty(fileno(stdout))) 91 myttyfd = fileno(stdout); 92 else if (isatty(fileno(stderr))) 93 myttyfd = fileno(stderr); 94 else 95 errx(1, "can't find your tty"); 96 if (!(mytty = ttyname(myttyfd))) 97 errx(1, "can't find your tty's name"); 98 if ((cp = strrchr(mytty, '/')) != NULL) 99 mytty = cp + 1; 100 if (term_chk(mytty, &msgsok, &atime, 1)) 101 exit(1); 102 if (!msgsok) { 103 (void)fprintf(stderr, 104 "warning: you have write permission turned off; " 105 "no reply possible\n"); 106 } 107 108 myuid = getuid(); 109 110 /* check args */ 111 switch (argc) { 112 case 2: 113 search_utmp(argv[1], tty, mytty, myuid, sizeof tty); 114 do_write(tty, mytty, myuid); 115 break; 116 case 3: 117 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV))) 118 argv[2] += strlen(_PATH_DEV); 119 if (utmp_chk(argv[1], argv[2])) 120 errx(1, "%s is not logged in on %s", 121 argv[1], argv[2]); 122 if (term_chk(argv[2], &msgsok, &atime, 1)) 123 exit(1); 124 if (myuid && !msgsok) 125 errx(1, "%s has messages disabled on %s", 126 argv[1], argv[2]); 127 do_write(argv[2], mytty, myuid); 128 break; 129 default: 130 (void)fprintf(stderr, "usage: write user [tty]\n"); 131 exit(1); 132 } 133 done(0); 134 /* NOTREACHED */ 135 #ifdef __GNUC__ 136 return (0); 137 #endif 138 } 139 140 /* 141 * utmp_chk - checks that the given user is actually logged in on 142 * the given tty 143 */ 144 int 145 utmp_chk(const char *user, const char *tty) 146 { 147 struct utmpentry *ep; 148 149 (void)getutentries(NULL, &ep); 150 151 for (; ep; ep = ep->next) 152 if (strcmp(user, ep->name) == 0 && strcmp(tty, ep->line) == 0) 153 return(0); 154 return(1); 155 } 156 157 /* 158 * search_utmp - search utmp for the "best" terminal to write to 159 * 160 * Ignores terminals with messages disabled, and of the rest, returns 161 * the one with the most recent access time. Returns as value the number 162 * of the user's terminals with messages enabled, or -1 if the user is 163 * not logged in at all. 164 * 165 * Special case for writing to yourself - ignore the terminal you're 166 * writing from, unless that's the only terminal with messages enabled. 167 */ 168 void 169 search_utmp(char *user, char *tty, char *mytty, uid_t myuid, int ttylen) 170 { 171 time_t bestatime, atime; 172 int nloggedttys, nttys, msgsok, user_is_me; 173 struct utmpentry *ep; 174 175 (void)getutentries(NULL, &ep); 176 177 nloggedttys = nttys = 0; 178 bestatime = 0; 179 user_is_me = 0; 180 for (; ep; ep = ep->next) 181 if (strcmp(user, ep->name) == 0) { 182 ++nloggedttys; 183 if (term_chk(ep->line, &msgsok, &atime, 0)) 184 continue; /* bad term? skip */ 185 if (myuid && !msgsok) 186 continue; /* skip ttys with msgs off */ 187 if (strcmp(ep->line, 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 (void)strncpy(tty, ep->line, ttylen - 1); 195 tty[ttylen - 1] = '\0'; 196 } 197 } 198 199 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 (void)strncpy(tty, mytty, ttylen - 1); 204 tty[ttylen - 1] = '\0'; 205 return; 206 } 207 errx(1, "%s has messages disabled", user); 208 } else if (nttys > 1) 209 warnx("%s is logged in more than once; writing to %s", 210 user, tty); 211 } 212 213 /* 214 * term_chk - check that a terminal exists, and get the message bit 215 * and the access time 216 */ 217 int 218 term_chk(const char *tty, int *msgsokP, time_t *atimeP, int showerror) 219 { 220 struct stat s; 221 char path[MAXPATHLEN]; 222 223 (void)snprintf(path, sizeof path, _PATH_DEV "%s", tty); 224 if (stat(path, &s) < 0) { 225 if (showerror) 226 warn("%s", path); 227 return(1); 228 } 229 *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */ 230 *atimeP = s.st_atime; 231 return(0); 232 } 233 234 /* 235 * do_write - actually make the connection 236 */ 237 void 238 do_write(const char *tty, const char *mytty, const uid_t myuid) 239 { 240 const char *login; 241 char *nows; 242 struct passwd *pwd; 243 time_t now; 244 char path[MAXPATHLEN], host[MAXHOSTNAMELEN + 1], line[512]; 245 246 /* Determine our login name before the we reopen() stdout */ 247 if ((login = getlogin()) == NULL) { 248 if ((pwd = getpwuid(myuid)) != NULL) 249 login = pwd->pw_name; 250 else login = "???"; 251 } 252 (void)snprintf(path, sizeof path, _PATH_DEV "%s", tty); 253 if ((freopen(path, "w", stdout)) == NULL) 254 err(1, "%s", path); 255 256 (void)signal(SIGINT, done); 257 (void)signal(SIGHUP, done); 258 259 /* print greeting */ 260 if (gethostname(host, sizeof(host)) < 0) 261 (void)strncpy(host, "???", sizeof(host) - 1); 262 else 263 host[sizeof(host) - 1] = '\0'; 264 now = time((time_t *)NULL); 265 nows = ctime(&now); 266 nows[16] = '\0'; 267 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n", 268 login, host, mytty, nows + 11); 269 270 while (fgets(line, sizeof(line), stdin) != NULL) 271 wr_fputs(line); 272 } 273 274 /* 275 * done - cleanup and exit 276 */ 277 void 278 done(int dummy) 279 { 280 281 (void)printf("EOF\r\n"); 282 exit(0); 283 } 284 285 /* 286 * wr_fputs - like fputs(), but makes control characters visible and 287 * turns \n into \r\n 288 */ 289 void 290 wr_fputs(char *s) 291 { 292 char c; 293 294 #define PUTC(c) if (putchar(c) == EOF) goto err; 295 296 for (; *s != '\0'; ++s) { 297 c = toascii(*s); 298 if (c == '\n') { 299 PUTC('\r'); 300 PUTC('\n'); 301 } else if (!isprint((unsigned char)c) && 302 !isspace((unsigned char)c) && c != '\007') { 303 PUTC('^'); 304 PUTC(c^0x40); /* DEL to ?, others to alpha */ 305 } else 306 PUTC(c); 307 } 308 return; 309 310 err: err(1, NULL); 311 #undef PUTC 312 } 313
Indexes created Mon Sep 22 05:09:51 GMT 2025