write.c revision 1.22
1 /* $NetBSD: write.c,v 1.22 2003/04/20 23:53:05 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 1.22 2003/04/20 23:53:05 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 #include <errno.h> 68 69 #include "utmpentry.h" 70 #include "term_chk.h" 71 72 void done(int); 73 void do_write(int, const char *, const uid_t); 74 void wr_fputs(char *); 75 int search_utmp(char *, char *, uid_t, gid_t); 76 int utmp_chk(const char *, const char *); 77 int main(int, char **); 78 79 80 int 81 main(int argc, char **argv) 82 { 83 time_t atime; 84 uid_t myuid, uid; 85 int msgsok, ttyfd; 86 char *mytty; 87 gid_t saved_egid = getegid(); 88 89 if (setegid(getgid()) == -1) 90 err(1, "setegid"); 91 myuid = getuid(); 92 ttyfd = -1; 93 94 mytty = check_sender(&atime, myuid, saved_egid); 95 96 /* check args */ 97 switch (argc) { 98 case 2: 99 ttyfd = search_utmp(argv[1], mytty, myuid, saved_egid); 100 break; 101 case 3: 102 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV))) 103 argv[2] += strlen(_PATH_DEV); 104 if (uid_from_user(argv[1], &uid) == -1) 105 errx(1, "%s: unknown user", argv[1]); 106 if (utmp_chk(argv[1], argv[2])) 107 errx(1, "%s is not logged in on %s", 108 argv[1], argv[2]); 109 ttyfd = term_chk(uid, argv[2], &msgsok, &atime, 0, saved_egid); 110 if (ttyfd == -1) 111 err(1, "%s%s", _PATH_DEV, argv[2]); 112 if (myuid && !msgsok) 113 errx(1, "%s has messages disabled on %s", 114 argv[1], argv[2]); 115 break; 116 default: 117 (void)fprintf(stderr, "usage: write user [tty]\n"); 118 exit(1); 119 } 120 if (setgid(getgid()) == -1) 121 err(1, "setgid"); 122 do_write(ttyfd, mytty, myuid); 123 done(0); 124 /* NOTREACHED */ 125 #ifdef __GNUC__ 126 return (0); 127 #endif 128 } 129 130 /* 131 * utmp_chk - checks that the given user is actually logged in on 132 * the given tty 133 */ 134 int 135 utmp_chk(const char *user, const char *tty) 136 { 137 struct utmpentry *ep; 138 139 (void)getutentries(NULL, &ep); 140 141 for (; ep; ep = ep->next) 142 if (strcmp(user, ep->name) == 0 && strcmp(tty, ep->line) == 0) 143 return(0); 144 return(1); 145 } 146 147 /* 148 * search_utmp - search utmp for the "best" terminal to write to 149 * 150 * Ignores terminals with messages disabled, and of the rest, returns 151 * the one with the most recent access time. Returns as value the number 152 * of the user's terminals with messages enabled, or -1 if the user is 153 * not logged in at all. 154 * 155 * Special case for writing to yourself - ignore the terminal you're 156 * writing from, unless that's the only terminal with messages enabled. 157 */ 158 int 159 search_utmp(char *user, char *mytty, uid_t myuid, gid_t saved_egid) 160 { 161 char tty[MAXPATHLEN]; 162 time_t bestatime, atime; 163 int nloggedttys, nttys, msgsok, user_is_me; 164 struct utmpentry *ep; 165 int fd, nfd; 166 uid_t uid; 167 168 if (uid_from_user(user, &uid) == -1) 169 errx(1, "%s: unknown user", user); 170 171 (void)getutentries(NULL, &ep); 172 173 nloggedttys = nttys = 0; 174 bestatime = 0; 175 user_is_me = 0; 176 fd = -1; 177 for (; ep; ep = ep->next) 178 if (strcmp(user, ep->name) == 0) { 179 ++nloggedttys; 180 nfd = term_chk(uid, ep->line, &msgsok, &atime, 0, 181 saved_egid); 182 if (nfd == -1) 183 continue; /* bad term? skip */ 184 if (myuid && !msgsok) { 185 close(nfd); 186 continue; /* skip ttys with msgs off */ 187 } 188 if (strcmp(ep->line, mytty) == 0) { 189 user_is_me = 1; 190 if (fd == -1) 191 fd = nfd; 192 else 193 close(nfd); 194 continue; /* don't write to yourself */ 195 } 196 ++nttys; 197 if (atime > bestatime) { 198 bestatime = atime; 199 (void)strlcpy(tty, ep->line, sizeof(tty)); 200 close(fd); 201 fd = nfd; 202 } else 203 close(nfd); 204 } 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 return fd; 211 errx(1, "%s has messages disabled", user); 212 } else if (nttys > 1) 213 warnx("%s is logged in more than once; writing to %s", 214 user, tty); 215 return fd; 216 } 217 218 /* 219 * do_write - actually make the connection 220 */ 221 void 222 do_write(int ttyfd, const char *mytty, const uid_t myuid) 223 { 224 const char *login; 225 char *nows; 226 struct passwd *pwd; 227 time_t now; 228 char host[MAXHOSTNAMELEN + 1], line[512]; 229 230 /* Determine our login name before we re-open stdout */ 231 if ((login = getlogin()) == NULL) { 232 if ((pwd = getpwuid(myuid)) != NULL) 233 login = pwd->pw_name; 234 else login = "???"; 235 } 236 237 if (dup2(ttyfd, STDOUT_FILENO) == -1) 238 err(1, "dup2"); 239 240 (void)signal(SIGINT, done); 241 (void)signal(SIGHUP, done); 242 (void)close(ttyfd); 243 244 /* print greeting */ 245 if (gethostname(host, sizeof(host)) < 0) 246 (void)strncpy(host, "???", sizeof(host) - 1); 247 else 248 host[sizeof(host) - 1] = '\0'; 249 now = time((time_t *)NULL); 250 nows = ctime(&now); 251 nows[16] = '\0'; 252 (void)printf("\r\n\a\a\aMessage from %s@%s on %s at %s ...\r\n", 253 login, host, mytty, nows + 11); 254 255 while (fgets(line, sizeof(line), stdin) != NULL) 256 wr_fputs(line); 257 } 258 259 /* 260 * done - cleanup and exit 261 */ 262 void 263 done(int signo) 264 { 265 266 (void)write(STDOUT_FILENO, "EOF\r\n", sizeof("EOF\r\n") - 1); 267 if (signo == 0) 268 exit(0); 269 else 270 _exit(0); 271 } 272 273 /* 274 * wr_fputs - like fputs(), but makes control characters visible and 275 * turns \n into \r\n 276 */ 277 void 278 wr_fputs(char *s) 279 { 280 unsigned char c; 281 282 #define PUTC(c) if (putchar(c) == EOF) goto err; 283 284 for (; *s != '\0'; ++s) { 285 c = toascii(*s); 286 if (c == '\n') { 287 PUTC('\r'); 288 } else if (!isprint(c) && !isspace(c) && c != '\a') { 289 PUTC('^'); 290 c ^= 0x40; /* DEL to ?, others to alpha */ 291 } 292 PUTC(c); 293 } 294 return; 295 296 err: err(1, NULL); 297 #undef PUTC 298 } 299
Indexes created Wed Sep 24 15:09:51 GMT 2025