freebsd-dev/usr.bin/write/write.c
Mark Johnston 27ed53c311 Remove extraneous setutxent() calls in write(1).
We already call setutxent() once during initialization.  Furthermore,
the subsequent calls occur after the process has entered capability
mode, so they fail, and attempts to fetch database entries fail as
a result.

PR:		235096
Submitted by:	fullermd@over-yonder.net
MFC after:	3 days
2019-01-23 20:02:17 +00:00

360 lines
9.2 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1989, 1993\n\
The Regents of the University of California. All rights reserved.\n";
#endif
#if 0
#ifndef lint
static char sccsid[] = "@(#)write.c 8.1 (Berkeley) 6/6/93";
#endif
#endif
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/capsicum.h>
#include <sys/filio.h>
#include <sys/signal.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <capsicum_helpers.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <locale.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <utmpx.h>
#include <wchar.h>
#include <wctype.h>
void done(int);
void do_write(int, char *, char *, const char *);
static void usage(void);
int term_chk(int, char *, int *, time_t *, int);
void wr_fputs(wchar_t *s);
void search_utmp(int, char *, char *, char *, uid_t);
int utmp_chk(char *, char *);
int
main(int argc, char **argv)
{
unsigned long cmds[] = { TIOCGETA, TIOCGWINSZ, FIODGNAME };
cap_rights_t rights;
struct passwd *pwd;
time_t atime;
uid_t myuid;
int msgsok, myttyfd;
char tty[MAXPATHLEN], *mytty;
const char *login;
int devfd;
(void)setlocale(LC_CTYPE, "");
devfd = open(_PATH_DEV, O_RDONLY);
if (devfd < 0)
err(1, "open(/dev)");
cap_rights_init(&rights, CAP_FCNTL, CAP_FSTAT, CAP_IOCTL, CAP_LOOKUP,
CAP_PWRITE);
if (caph_rights_limit(devfd, &rights) < 0)
err(1, "can't limit devfd rights");
/*
* Can't use capsicum helpers here because we need the additional
* FIODGNAME ioctl.
*/
cap_rights_init(&rights, CAP_FCNTL, CAP_FSTAT, CAP_IOCTL, CAP_READ,
CAP_WRITE);
if (caph_rights_limit(STDIN_FILENO, &rights) < 0 ||
caph_rights_limit(STDOUT_FILENO, &rights) < 0 ||
caph_rights_limit(STDERR_FILENO, &rights) < 0 ||
caph_ioctls_limit(STDIN_FILENO, cmds, nitems(cmds)) < 0 ||
caph_ioctls_limit(STDOUT_FILENO, cmds, nitems(cmds)) < 0 ||
caph_ioctls_limit(STDERR_FILENO, cmds, nitems(cmds)) < 0 ||
caph_fcntls_limit(STDIN_FILENO, CAP_FCNTL_GETFL) < 0 ||
caph_fcntls_limit(STDOUT_FILENO, CAP_FCNTL_GETFL) < 0 ||
caph_fcntls_limit(STDERR_FILENO, CAP_FCNTL_GETFL) < 0)
err(1, "can't limit stdio rights");
caph_cache_catpages();
caph_cache_tzdata();
/*
* Cache UTX database fds.
*/
setutxent();
/*
* Determine our login name before we reopen() stdout
* and before entering capability sandbox.
*/
myuid = getuid();
if ((login = getlogin()) == NULL) {
if ((pwd = getpwuid(myuid)))
login = pwd->pw_name;
else
login = "???";
}
if (caph_enter() < 0)
err(1, "cap_enter");
while (getopt(argc, argv, "") != -1)
usage();
argc -= optind;
argv += optind;
/* check that sender has write enabled */
if (isatty(fileno(stdin)))
myttyfd = fileno(stdin);
else if (isatty(fileno(stdout)))
myttyfd = fileno(stdout);
else if (isatty(fileno(stderr)))
myttyfd = fileno(stderr);
else
errx(1, "can't find your tty");
if (!(mytty = ttyname(myttyfd)))
errx(1, "can't find your tty's name");
if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV)))
mytty += strlen(_PATH_DEV);
if (term_chk(devfd, mytty, &msgsok, &atime, 1))
exit(1);
if (!msgsok)
errx(1, "you have write permission turned off");
/* check args */
switch (argc) {
case 1:
search_utmp(devfd, argv[0], tty, mytty, myuid);
do_write(devfd, tty, mytty, login);
break;
case 2:
if (!strncmp(argv[1], _PATH_DEV, strlen(_PATH_DEV)))
argv[1] += strlen(_PATH_DEV);
if (utmp_chk(argv[0], argv[1]))
errx(1, "%s is not logged in on %s", argv[0], argv[1]);
if (term_chk(devfd, argv[1], &msgsok, &atime, 1))
exit(1);
if (myuid && !msgsok)
errx(1, "%s has messages disabled on %s", argv[0], argv[1]);
do_write(devfd, argv[1], mytty, login);
break;
default:
usage();
}
done(0);
return (0);
}
static void
usage(void)
{
(void)fprintf(stderr, "usage: write user [tty]\n");
exit(1);
}
/*
* utmp_chk - checks that the given user is actually logged in on
* the given tty
*/
int
utmp_chk(char *user, char *tty)
{
struct utmpx lu, *u;
strncpy(lu.ut_line, tty, sizeof lu.ut_line);
while ((u = getutxline(&lu)) != NULL)
if (u->ut_type == USER_PROCESS &&
strcmp(user, u->ut_user) == 0) {
endutxent();
return(0);
}
endutxent();
return(1);
}
/*
* search_utmp - search utmp for the "best" terminal to write to
*
* Ignores terminals with messages disabled, and of the rest, returns
* the one with the most recent access time. Returns as value the number
* of the user's terminals with messages enabled, or -1 if the user is
* not logged in at all.
*
* Special case for writing to yourself - ignore the terminal you're
* writing from, unless that's the only terminal with messages enabled.
*/
void
search_utmp(int devfd, char *user, char *tty, char *mytty, uid_t myuid)
{
struct utmpx *u;
time_t bestatime, atime;
int nloggedttys, nttys, msgsok, user_is_me;
nloggedttys = nttys = 0;
bestatime = 0;
user_is_me = 0;
while ((u = getutxent()) != NULL)
if (u->ut_type == USER_PROCESS &&
strcmp(user, u->ut_user) == 0) {
++nloggedttys;
if (term_chk(devfd, u->ut_line, &msgsok, &atime, 0))
continue; /* bad term? skip */
if (myuid && !msgsok)
continue; /* skip ttys with msgs off */
if (strcmp(u->ut_line, mytty) == 0) {
user_is_me = 1;
continue; /* don't write to yourself */
}
++nttys;
if (atime > bestatime) {
bestatime = atime;
(void)strlcpy(tty, u->ut_line, MAXPATHLEN);
}
}
endutxent();
if (nloggedttys == 0)
errx(1, "%s is not logged in", user);
if (nttys == 0) {
if (user_is_me) { /* ok, so write to yourself! */
(void)strlcpy(tty, mytty, MAXPATHLEN);
return;
}
errx(1, "%s has messages disabled", user);
} else if (nttys > 1) {
warnx("%s is logged in more than once; writing to %s", user, tty);
}
}
/*
* term_chk - check that a terminal exists, and get the message bit
* and the access time
*/
int
term_chk(int devfd, char *tty, int *msgsokP, time_t *atimeP, int showerror)
{
struct stat s;
if (fstatat(devfd, tty, &s, 0) < 0) {
if (showerror)
warn("%s%s", _PATH_DEV, tty);
return(1);
}
*msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */
*atimeP = s.st_atime;
return(0);
}
/*
* do_write - actually make the connection
*/
void
do_write(int devfd, char *tty, char *mytty, const char *login)
{
char *nows;
time_t now;
char host[MAXHOSTNAMELEN];
wchar_t line[512];
int fd;
fd = openat(devfd, tty, O_WRONLY);
if (fd < 0)
err(1, "openat(%s%s)", _PATH_DEV, tty);
fclose(stdout);
stdout = fdopen(fd, "w");
if (stdout == NULL)
err(1, "%s%s", _PATH_DEV, tty);
(void)signal(SIGINT, done);
(void)signal(SIGHUP, done);
/* print greeting */
if (gethostname(host, sizeof(host)) < 0)
(void)strcpy(host, "???");
now = time((time_t *)NULL);
nows = ctime(&now);
nows[16] = '\0';
(void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
login, host, mytty, nows + 11);
while (fgetws(line, sizeof(line)/sizeof(wchar_t), stdin) != NULL)
wr_fputs(line);
}
/*
* done - cleanup and exit
*/
void
done(int n __unused)
{
(void)printf("EOF\r\n");
exit(0);
}
/*
* wr_fputs - like fputs(), but makes control characters visible and
* turns \n into \r\n
*/
void
wr_fputs(wchar_t *s)
{
#define PUTC(c) if (putwchar(c) == WEOF) err(1, NULL);
for (; *s != L'\0'; ++s) {
if (*s == L'\n') {
PUTC(L'\r');
PUTC(L'\n');
} else if (iswprint(*s) || iswspace(*s)) {
PUTC(*s);
} else {
wprintf(L"<0x%X>", *s);
}
}
return;
#undef PUTC
}