/* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */ /* All Rights Reserved */ /* THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T */ /* The copyright notice above does not evidence any */ /* actual or intended publication of such source code. */ /* Portions Copyright (c) 1988, Sun Microsystems, Inc. */ /* All Rights Reserved. */ #ident "@(#)write.c 1.16 94/10/03 SMI" /* SVr4.0 1.19 */ /* Program to communicate with other users of the system. */ /* Usage: write user_name [terminal] */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define TRUE 1 #define FALSE 0 #define FAILURE -1 #define DATE_FMT "%a %b %e %H:%M:%S" #define UTMP_HACK /* Enable work around until utmp is world writable */ /* * DATE-TIME format * %a abbreviated weekday name * %b abbreviated month name * %e day of month * %H hour - 24 hour clock * %M minute * %S second * */ static int permit1(int); static int permit(char *); static int readeuc(int, char *, int); static void setsignals(); static void shellcmd(char *); static void openfail(); static void eof(); static struct utsname utsn; static FILE *fp; /* File pointer for receipient's terminal */ static char *rterm, *receipient; /* Pointer to receipient's terminal & name */ static char *thissys; void main(argc, argv) int argc; char **argv; { register int i; register struct utmp *ubuf; static struct utmp self; char ownname[sizeof (self.ut_user) + 1]; static char rterminal[] = "/dev/\0 2345678901"; extern char *rterm, *receipient; char *terminal, *ownterminal, *oterminal; short count; extern FILE *fp; char input[134+MB_LEN_MAX]; register char *ptr; long tod; char time_buf[40]; struct passwd *passptr; char badterm[20][20]; register int bad = 0; uid_t myuid; register char *bp; unsigned int ibp; int n; wchar_t wc; register c; (void) setlocale(LC_ALL, ""); #if !defined(TEXT_DOMAIN) #define TEXT_DOMAIN "SYS_TEST" #endif (void) textdomain(TEXT_DOMAIN); while ((c = getopt(argc, argv, "")) != EOF) switch (c) { case '?': (void) fprintf(stderr, "Usage: write %s\n", gettext("user_name [terminal]")); exit(2); } myuid = geteuid(); uname(&utsn); thissys = utsn.nodename; /* Set "rterm" to location where receipient's terminal will go. */ rterm = &rterminal[sizeof ("/dev/") - 1]; terminal = NULL; if (--argc <= 0) { (void) fprintf(stderr, "Usage: write %s\n", gettext("user_name [terminal]")); exit(1); } else { receipient = *++argv; } /* Was a terminal name supplied? If so, save it. */ if (--argc > 1) { (void) fprintf(stderr, "Usage: write %s\n", gettext("user_name [terminal]")); exit(1); } else terminal = *++argv; /* One of the standard file descriptors must be attached to a */ /* terminal in "/dev". */ if ((ownterminal = ttyname(fileno(stdin))) == NULL && (ownterminal = ttyname(fileno(stdout))) == NULL && (ownterminal = ttyname(fileno(stderr))) == NULL) { (void) fprintf(stderr, gettext("I cannot determine your terminal name." " No reply possible.\n")); ownterminal = "/dev/???"; } /* Set "ownterminal" past the "/dev/" at the beginning of */ /* the device name. */ oterminal = ownterminal + sizeof ("/dev/")-1; /* Scan through the "utmp" file for your own entry and the */ /* entry for the person we want to send to. */ for (self.ut_pid = 0, count = 0; (ubuf = getutent()) != NULL; ) { /* Is this a USER_PROCESS entry? */ if (ubuf->ut_type == USER_PROCESS) { /* Is it our entry? (ie. The line matches ours?) */ if (strncmp(&ubuf->ut_line[0], oterminal, sizeof (ubuf->ut_line)) == 0) self = *ubuf; /* Is this the person we want to send to? */ if (strncmp(receipient, &ubuf->ut_user[0], sizeof (ubuf->ut_user)) == 0) { /* If a terminal name was supplied, is this login at the correct */ /* terminal? If not, ignore. If it is right place, copy over the */ /* name. */ if (terminal != NULL) { if (strncmp(terminal, &ubuf->ut_line[0], sizeof (ubuf->ut_line)) == 0) { strncpy(rterm, &ubuf->ut_line[0], sizeof (ubuf->ut_line)+1); if (myuid && !permit(rterminal)) { bad++; rterm[0] = '\0'; } } } /* If no terminal was supplied, then take this terminal if no */ /* other terminal has been encountered already. */ else { /* If this is the first encounter, copy the string into */ /* "rterminal". */ if (*rterm == '\0') { strncpy(rterm, &ubuf->ut_line[0], sizeof (ubuf->ut_line)+1); if (myuid && !permit(rterminal)) { strcpy(badterm[bad++], rterm); rterm[0] = '\0'; } else if (bad > 0) { (void) fprintf(stderr, gettext( "%s is logged on more than one place.\n" "You are connected to \"%s\".\nOther locations are:\n"), receipient, rterm); for (i = 0; i < bad; i++) (void) fprintf(stderr, "%s\n", badterm[i]); } } /* If this is the second terminal, print out the first. In all */ /* cases of multiple terminals, list out all the other terminals */ /* so the user can restart knowing what her/his choices are. */ else if (terminal == NULL) { if (count == 1 && bad == 0) { (void) fprintf(stderr, gettext( "%s is logged on more than one place.\n" "You are connected to \"%s\".\nOther locations are:\n"), receipient, rterm); } fwrite(&ubuf->ut_line[0], sizeof (ubuf->ut_line), 1, stderr); (void) fprintf(stderr, "\n"); } count++; } /* End of "else" */ } /* End of "else if (strncmp" */ } /* End of "if (USER_PROCESS" */ } /* End of "for(count=0" */ /* Did we find a place to talk to? If we were looking for a */ /* specific spot and didn't find it, complain and quit. */ if (terminal != NULL && *rterm == '\0') { if (bad > 0) { (void) fprintf(stderr, gettext("Permission denied.\n")); exit(1); } else { #ifdef UTMP_HACK strcat(rterminal, terminal); strcpy(rterm, terminal); if (self.ut_pid == 0) { if ((passptr = getpwuid(getuid())) == (struct passwd *)NULL) { (void) fprintf(stderr, gettext("Cannot determine who you are.\n")); exit(1); } strncpy(&ownname[0], &passptr->pw_name[0], sizeof (ownname)); } if (!permit(rterminal)) { (void) fprintf(stderr, gettext("%s permission denied\n"), terminal); exit(1); } #else (void) fprintf(stderr, gettext("%s is not at \"%s\".\n"), receipient, terminal); exit(1); #endif /* UTMP_HACK */ } } /* If we were just looking for anyplace to talk and didn't find */ /* one, complain and quit. */ /* If permissions prevent us from sending to this person - exit */ else if (*rterm == '\0') { if (bad > 0) (void) fprintf(stderr, gettext("Permission denied.\n")); else (void) fprintf(stderr, gettext("%s is not logged on.\n"), receipient); exit(1); } /* Did we find our own entry? */ else if (self.ut_pid == 0) { /* Use the user id instead of utmp name if the entry in the */ /* utmp file couldn't be found. */ if ((passptr = getpwuid(getuid())) == (struct passwd *)NULL) { (void) fprintf(stderr, gettext("Cannot determine who you are.\n")); exit(1); } strncpy(&ownname[0], &passptr->pw_name[0], sizeof (ownname)); } else { strncpy(&ownname[0], self.ut_user, sizeof (self.ut_user)); } ownname[sizeof (ownname)-1] = '\0'; if (!permit1(1)) (void) fprintf(stderr, gettext("Warning: You have your terminal set to \"mesg -n\"." " No reply possible.\n")); /* Try to open up the line to the receipient's terminal. */ signal(SIGALRM, openfail); alarm(5); fp = fopen(&rterminal[0], "w"); alarm(0); /* Catch signals SIGHUP, SIGINT, SIGQUIT, and SIGTERM, and send */ /* message to receipient before dying away. */ setsignals(eof); /* Get the time of day, convert it to a string and throw away the */ /* year information at the end of the string. */ time(&tod); cftime(time_buf, dcgettext(NULL, DATE_FMT, LC_TIME), &tod); (void) fprintf(fp, gettext("\n\007\007\007\tMessage from %s on %s (%s) [ %s ] ...\n"), &ownname[0], thissys, oterminal, time_buf); fflush(fp); (void) fprintf(stderr, "\007\007"); /* Get input from user and send to receipient unless it begins */ /* with a !, when it is to be a shell command. */ while ((i = readeuc(0, &input[0], sizeof (input))) > 0) { ptr = &input[0]; /* Is this a shell command? */ if (*ptr == '!') shellcmd(++ptr); /* Send line to the receipient. */ else { if (myuid && !permit1(fileno(fp))) { (void) fprintf(stderr, gettext("Can no longer write to %s\n"), rterminal); break; } /* * All non-printable characters are displayed using a special notation: * Control characters shall be displayed using the two character * sequence of ^ (carat) and the ASCII character - decimal 64 greater * that the character being encoded - eg., a \003 is displayed ^C. * Characters with the eighth bit set shall be displayed using * the three or four character meta notation - e.g., \372 is * displayed M-z and \203 is displayed M-^C. */ for (bp = &input[0]; --i >= 0; bp++) { ibp = (unsigned int) *bp; if (*bp == '\n') putc('\r', fp); if (*bp == ' ' || *bp == '\t' || *bp == '\n' || *bp == '\r' || *bp == '\013' || *bp == '\007') { putc(*bp, fp); } else if (((n = mbtowc(&wc, bp, MB_LEN_MAX)) > 0) && iswprint(wc)) { for (; n > 0; --n, --i, ++bp) putc(*bp, fp); bp--, ++i; } else { if (!isascii(*bp)) { fputs("M-", fp); *bp = toascii(*bp); } if (iscntrl(*bp)) { putc('^', fp); /* add decimal 64 to the control character */ putc(*bp + 0100, fp); } else putc(*bp, fp); } if (*bp == '\n') fflush(fp); if (ferror(fp) || feof(fp)) { printf(gettext( "\n\007Write failed (%s logged out?)\n"), receipient); exit(1); } } /* for */ fflush(fp); } /* else */ } /* while */ /* Since "end of file" received, send message to receipient. */ eof(); } static void setsignals(catch) void (*catch)(); { signal(SIGHUP, catch); signal(SIGINT, catch); signal(SIGQUIT, catch); signal(SIGTERM, catch); } static void shellcmd(command) char *command; { register pid_t child; extern void eof(); if ((child = fork()) == (pid_t)FAILURE) { (void) fprintf(stderr, gettext("Unable to fork. Try again later.\n")); return; } else if (child == (pid_t)0) { /* Reset the signals to the default actions and exec a shell. */ if (setgid(getgid()) < 0) exit(1); execl("/usr/bin/sh", "sh", "-c", command, 0); exit(0); } else { /* Allow user to type and without dying during */ /* commands. */ signal(SIGINT, SIG_IGN); signal(SIGQUIT, SIG_IGN); /* As parent wait around for user to finish spunoff command. */ while (wait(NULL) != child); /* Reset the signals to their normal state. */ setsignals(eof); } (void) fprintf(stdout, "!\n"); } static void openfail() { extern char *rterm, *receipient; (void) fprintf(stderr, gettext("Timeout trying to open %s's line(%s).\n"), receipient, rterm); exit(1); } static void eof() { extern FILE *fp; (void) fprintf(fp, "%s\n", gettext("")); exit(0); } /* * permit: check mode of terminal - if not writable by all disallow writing to * (even the user him/herself cannot therefore write to their own tty) */ static int permit(term) char *term; { struct stat buf; int fildes; if ((fildes = open(term, O_WRONLY|O_NOCTTY)) < 0) return (0); /* check if the device really is a tty */ if (!isatty(fildes)) { (void) fprintf(stderr, gettext("%s in utmp is not a tty\n"), term); openlog("write", 0, LOG_AUTH); syslog(LOG_CRIT, "%s in utmp is not a tty\n", term); closelog(); close(fildes); return (0); } fstat(fildes, &buf); close(fildes); return (buf.st_mode & (S_IWGRP|S_IWOTH)); } /* * permit1: check mode of terminal - if not writable by all disallow writing * to (even the user him/herself cannot therefore write to their own tty) */ /* this is used with fstat (which is faster than stat) where possible */ static int permit1(fildes) int fildes; { struct stat buf; fstat(fildes, &buf); return (buf.st_mode & (S_IWGRP|S_IWOTH)); } /* Read a string of EUC characters from specified file. * The requested # of bytes are attempted to read. * readeuc() tries to complete the last multibyte character * by calling read() again, when the first read() call * left the last char imcomplete. The caller must reserve * nbytereq+MB_LEN_MAX bytes for the buffer. When the attempt * is failed, it truncate the last char. * Returns the number of bytes that constitutes the valid EUC characters. */ static int readeuc(d, buf, nbytereq) int d; char *buf; int nbytereq; { char *cp, *nextp, *lastp; int n; int delta; n = read(d, buf, nbytereq); if (n <= 0) return (n); /* Scan the result to test the completeness of each EUC characters. */ nextp = buf; lastp = buf + n; /* Lastp points to the first junk byte. */ while (nextp < lastp) { cp = nextp; nextp += euclen((const unsigned char *)cp); } /* How many bytes needed to complete the last char? */ delta = nextp - lastp; if (delta > 0) { n = read(d, lastp, delta); /* Try reading that many bytes. */ if (n != delta) { /* Failed! Pretend we dindn't read the garbage bytes. */ nextp = cp; } } return (nextp-buf); /* Return # of bytes. */ }