1 /* $OpenBSD: comsat.c,v 1.50 2021/07/12 15:09:18 beck Exp $ */ 2 3 /* 4 * Copyright (c) 1980, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 #include <sys/limits.h> 33 #include <sys/socket.h> 34 #include <sys/stat.h> 35 #include <sys/wait.h> 36 37 #include <netinet/in.h> 38 39 #include <ctype.h> 40 #include <errno.h> 41 #include <fcntl.h> 42 #include <netdb.h> 43 #include <limits.h> 44 #include <paths.h> 45 #include <pwd.h> 46 #include <signal.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include <string.h> 50 #include <syslog.h> 51 #include <termios.h> 52 #include <unistd.h> 53 #include <utmp.h> 54 #include <vis.h> 55 #include <err.h> 56 57 int debug = 0; 58 #define dsyslog if (debug) syslog 59 60 #define MAXIDLE 120 61 62 char hostname[HOST_NAME_MAX+1]; 63 struct utmp *utmp = NULL; 64 time_t lastmsgtime; 65 int nutmp, uf; 66 67 void jkfprintf(FILE *, char[], off_t); 68 void mailfor(char *); 69 void notify(struct utmp *, off_t); 70 void readutmp(int); 71 void doreadutmp(void); 72 void reapchildren(int); 73 74 volatile sig_atomic_t wantreadutmp; 75 76 int 77 main(int argc, char *argv[]) 78 { 79 struct sockaddr_storage from; 80 struct sigaction sa; 81 ssize_t cc; 82 socklen_t fromlen; 83 char msgbuf[100]; 84 sigset_t sigset; 85 86 /* verify proper invocation */ 87 fromlen = sizeof(from); 88 if (getsockname(0, (struct sockaddr *)&from, &fromlen) == -1) { 89 (void)fprintf(stderr, 90 "comsat: getsockname: %s.\n", strerror(errno)); 91 exit(1); 92 } 93 94 if (unveil(_PATH_MAILDIR, "r") == -1) 95 err(1, "unveil %s", _PATH_MAILDIR); 96 if (unveil(_PATH_UTMP, "r") == -1) 97 err(1, "unveil %s", _PATH_UTMP); 98 if (unveil("/tmp", "w") == -1) 99 err(1, "unveil /tmp"); 100 if (unveil(_PATH_DEV, "rw") == -1) 101 err(1, "unveil %s", _PATH_DEV); 102 if (pledge("stdio rpath wpath proc tty", NULL) == -1) 103 err(1, "pledge"); 104 105 openlog("comsat", LOG_PID, LOG_DAEMON); 106 if (chdir(_PATH_MAILDIR)) { 107 syslog(LOG_ERR, "chdir: %s: %m", _PATH_MAILDIR); 108 (void) recv(0, msgbuf, sizeof(msgbuf) - 1, 0); 109 exit(1); 110 } 111 if ((uf = open(_PATH_UTMP, O_RDONLY)) == -1) { 112 syslog(LOG_ERR, "open: %s: %m", _PATH_UTMP); 113 (void) recv(0, msgbuf, sizeof(msgbuf) - 1, 0); 114 exit(1); 115 } 116 (void)time(&lastmsgtime); 117 (void)gethostname(hostname, sizeof(hostname)); 118 doreadutmp(); 119 120 (void)signal(SIGTTOU, SIG_IGN); 121 122 bzero(&sa, sizeof sa); 123 sigemptyset(&sa.sa_mask); 124 sa.sa_handler = readutmp; 125 sa.sa_flags = 0; /* no SA_RESTART */ 126 (void)sigaction(SIGALRM, &sa, NULL); 127 128 sa.sa_handler = reapchildren; 129 sa.sa_flags = SA_RESTART; 130 (void)sigaction(SIGCHLD, &sa, NULL); 131 132 for (;;) { 133 if (wantreadutmp) { 134 wantreadutmp = 0; 135 doreadutmp(); 136 } 137 138 cc = recv(0, msgbuf, sizeof(msgbuf) - 1, 0); 139 if (cc <= 0) { 140 if (errno != EINTR) 141 sleep(1); 142 continue; 143 } 144 if (!nutmp) /* no one has logged in yet */ 145 continue; 146 sigemptyset(&sigset); 147 sigaddset(&sigset, SIGALRM); 148 sigprocmask(SIG_SETMASK, &sigset, NULL); 149 msgbuf[cc] = '\0'; 150 (void)time(&lastmsgtime); 151 mailfor(msgbuf); 152 sigemptyset(&sigset); 153 sigprocmask(SIG_SETMASK, &sigset, NULL); 154 } 155 } 156 157 /* ARGSUSED */ 158 void 159 reapchildren(int signo) 160 { 161 int save_errno = errno; 162 163 while (wait3(NULL, WNOHANG, NULL) > 0) 164 ; 165 errno = save_errno; 166 } 167 168 /* ARGSUSED */ 169 void 170 readutmp(int signo) 171 { 172 wantreadutmp = 1; 173 } 174 175 void 176 doreadutmp(void) 177 { 178 static u_int utmpsize; /* last malloced size for utmp */ 179 static time_t utmpmtime; /* last modification time for utmp */ 180 struct stat statbf; 181 int n; 182 183 if (time(NULL) - lastmsgtime >= MAXIDLE) 184 exit(0); 185 (void)fstat(uf, &statbf); 186 if (statbf.st_mtime > utmpmtime) { 187 utmpmtime = statbf.st_mtime; 188 /* avoid int overflow */ 189 if (statbf.st_size > INT_MAX - 10 * sizeof(struct utmp)) { 190 syslog(LOG_ALERT, "utmp file excessively large"); 191 exit(1); 192 } 193 if (statbf.st_size > utmpsize) { 194 u_int nutmpsize = statbf.st_size + 10 * 195 sizeof(struct utmp); 196 struct utmp *u; 197 198 if ((u = recallocarray(utmp, utmpsize, 199 nutmpsize, 1)) == NULL) { 200 free(utmp); 201 syslog(LOG_ERR, "%s", strerror(errno)); 202 exit(1); 203 } 204 utmp = u; 205 utmpsize = nutmpsize; 206 } 207 n = pread(uf, utmp, statbf.st_size, 0); 208 if (n == -1) 209 n = 0; 210 nutmp = n / sizeof(struct utmp); 211 dsyslog(LOG_DEBUG, "read %d utmp entries", nutmp); 212 } 213 (void)alarm(15); 214 } 215 216 void 217 mailfor(char *name) 218 { 219 struct utmp *utp = &utmp[nutmp]; 220 char utname[UT_NAMESIZE+1]; 221 const char *errstr; 222 char *cp; 223 off_t offset; 224 225 dsyslog(LOG_DEBUG, "mail for '%s'", name); 226 if (!(cp = strchr(name, '@'))) 227 return; 228 *cp++ = '\0'; 229 cp[strcspn(cp, " \t\n")] = '\0'; 230 offset = strtonum(cp, 0, LLONG_MAX, &errstr); 231 if (errstr) { 232 syslog(LOG_ERR, "'%s' is %s", cp + 1, errstr); 233 return; 234 } 235 while (--utp >= utmp) { 236 memcpy(utname, utp->ut_name, UT_NAMESIZE); 237 utname[UT_NAMESIZE] = '\0'; 238 dsyslog(LOG_DEBUG, "check %s against %s", name, utname); 239 if (!strncmp(utname, name, UT_NAMESIZE)) 240 notify(utp, offset); 241 } 242 } 243 244 static char *cr; 245 246 void 247 notify(struct utmp *utp, off_t offset) 248 { 249 int fd; 250 FILE *tp; 251 struct stat stb; 252 struct termios ttybuf; 253 char tty[PATH_MAX], name[UT_NAMESIZE + 1]; 254 255 (void)snprintf(tty, sizeof(tty), "%s%.*s", 256 _PATH_DEV, (int)sizeof(utp->ut_line), utp->ut_line); 257 if (strchr(tty + sizeof(_PATH_DEV) - 1, '/')) { 258 /* A slash is an attempt to break security... */ 259 syslog(LOG_AUTH | LOG_NOTICE, "'/' in \"%s\"", tty); 260 return; 261 } 262 if (stat(tty, &stb) || !(stb.st_mode & S_IEXEC)) { 263 dsyslog(LOG_DEBUG, "%.*s: wrong mode on %s", 264 (int)sizeof(utp->ut_name), utp->ut_name, tty); 265 return; 266 } 267 dsyslog(LOG_DEBUG, "notify %.*s on %s", (int)sizeof(utp->ut_name), 268 utp->ut_name, tty); 269 if (fork()) 270 return; 271 (void)signal(SIGALRM, SIG_DFL); 272 (void)alarm(30); 273 fd = open(tty, O_WRONLY); 274 if (fd == -1 || (tp = fdopen(fd, "w")) == NULL) { 275 dsyslog(LOG_ERR, "%s: %s", tty, strerror(errno)); 276 _exit(1); 277 } 278 (void)tcgetattr(fileno(tp), &ttybuf); 279 cr = (ttybuf.c_oflag & ONLCR) && (ttybuf.c_oflag & OPOST) ? 280 "\n" : "\n\r"; 281 memcpy(name, utp->ut_name, UT_NAMESIZE); 282 name[UT_NAMESIZE] = '\0'; 283 (void)fprintf(tp, "%s\007New mail for %s@%.*s\007 has arrived:%s----%s", 284 cr, name, (int)sizeof(hostname), hostname, cr, cr); 285 jkfprintf(tp, name, offset); 286 (void)fclose(tp); 287 _exit(0); 288 } 289 290 void 291 jkfprintf(FILE *tp, char name[], off_t offset) 292 { 293 char *cp, ch; 294 char visout[5], *s2; 295 FILE *fi; 296 int linecnt, charcnt, inheader; 297 char line[BUFSIZ]; 298 299 if ((fi = fopen(name, "r")) == NULL) 300 return; 301 302 (void)fseeko(fi, offset, SEEK_SET); 303 /* 304 * Print the first 7 lines or 560 characters of the new mail 305 * (whichever comes first). Skip header crap other than 306 * From, Subject, To, and Date. 307 */ 308 linecnt = 7; 309 charcnt = 560; 310 inheader = 1; 311 while (fgets(line, sizeof(line), fi) != NULL) { 312 if (inheader) { 313 if (line[0] == '\n') { 314 inheader = 0; 315 continue; 316 } 317 if (line[0] == ' ' || line[0] == '\t' || 318 (strncmp(line, "From:", 5) && 319 strncmp(line, "Subject:", 8))) 320 continue; 321 } 322 if (linecnt <= 0 || charcnt <= 0) { 323 (void)fprintf(tp, "...more...%s", cr); 324 (void)fclose(fi); 325 return; 326 } 327 /* strip weird stuff so can't trojan horse stupid terminals */ 328 for (cp = line; (ch = *cp) && ch != '\n'; ++cp, --charcnt) { 329 ch = toascii(ch); 330 vis(visout, ch, VIS_SAFE|VIS_NOSLASH, cp[1]); 331 for (s2 = visout; *s2; s2++) 332 (void)fputc(*s2, tp); 333 } 334 (void)fputs(cr, tp); 335 --linecnt; 336 } 337 (void)fprintf(tp, "----%s\n", cr); 338 (void)fclose(fi); 339 } 340