IABSD.fr/src/usr.bin/wall/ttymsg.c

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• Author : deraadt
  Date : 2019-06-28 13:34:58
  Hash : 3aaa63eb
  Message : When system calls indicate an error they return -1, not some arbitrary value < 0. errno is only updated in this case. Change all (most?) callers of syscalls to follow this better, and let's see if this strictness helps us in the future.

• usr.bin/wall/ttymsg.c

• /*	$OpenBSD: ttymsg.c,v 1.19 2019/06/28 13:35:05 deraadt Exp $	*/
  /*	$NetBSD: ttymsg.c,v 1.3 1994/11/17 07:17:55 jtc Exp $	*/
  
  /*
   * Copyright (c) 1989, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * 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.
   */
  
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <sys/uio.h>
  #include <signal.h>
  #include <fcntl.h>
  #include <dirent.h>
  #include <errno.h>
  #include <paths.h>
  #include <unistd.h>
  #include <stdio.h>
  #include <string.h>
  #include <stdlib.h>
  #include <err.h>
  
  char *ttymsg(struct iovec *, int, char *, int);
  
  /*
   * Display the contents of a uio structure on a terminal.  Used by wall(1)
   * and talkd(8).  Forks and finishes in child if write would block,
   * waiting up to tmout seconds.  Returns pointer to error string on unexpected
   * error; string is not newline-terminated.  Various "normal" errors are
   * ignored (exclusive-use, lack of permission, etc.).
   */
  char *
  ttymsg(iov, iovcnt, line, tmout)
  	struct iovec *iov;
  	int iovcnt;
  	char *line;
  	int tmout;
  {
  	static char device[MAXNAMLEN] = _PATH_DEV;
  	static char errbuf[1024];
  	int cnt, fd, left, wret;
  	struct iovec localiov[6];
  	int forked = 0;
  	struct stat st;
  	sigset_t mask;
  
  	if (iovcnt > sizeof(localiov) / sizeof(localiov[0]))
  		return ("too many iov's (change code in wall/ttymsg.c)");
  
  	/*
  	 * Ignore lines that start with "ftp" or "uucp".
  	 */
  	if ((strncmp(line, "ftp", 3) == 0) ||
  	    (strncmp(line, "uucp", 4) == 0))
  		return (NULL);
  
  	(void) strlcpy(device + sizeof(_PATH_DEV) - 1, line,
  	    sizeof(device) - (sizeof(_PATH_DEV) - 1));
  	if (strchr(device + sizeof(_PATH_DEV) - 1, '/')) {
  		/* A slash is an attempt to break security... */
  		(void) snprintf(errbuf, sizeof(errbuf), "'/' in \"%s\"",
  		    device);
  		return (errbuf);
  	}
  
  	/*
  	 * open will fail on slip lines or exclusive-use lines
  	 * if not running as root; not an error.
  	 */
  	if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) == -1) {
  		if (errno == EBUSY || errno == EACCES)
  			return (NULL);
  		(void) snprintf(errbuf, sizeof(errbuf),
  		    "%s: %s", device, strerror(errno));
  		return (errbuf);
  	}
  
  	if (getuid()) {
  		if (fstat(fd, &st) == -1 ||
  		    (st.st_mode & S_IWGRP) == 0) {
  			close(fd);
  			return (NULL);
  		}
  	}
  
  	for (cnt = left = 0; cnt < iovcnt; ++cnt)
  		left += iov[cnt].iov_len;
  
  	for (;;) {
  		wret = writev(fd, iov, iovcnt);
  		if (wret >= left)
  			break;
  		if (wret >= 0) {
  			left -= wret;
  			if (iov != localiov) {
  				bcopy(iov, localiov,
  				    iovcnt * sizeof(struct iovec));
  				iov = localiov;
  			}
  			for (cnt = 0; wret >= iov->iov_len; ++cnt) {
  				wret -= iov->iov_len;
  				++iov;
  				--iovcnt;
  			}
  			if (wret) {
  				char *base = iov->iov_base;
  
  				iov->iov_base = base + wret;
  				iov->iov_len -= wret;
  			}
  			continue;
  		}
  		if (errno == EWOULDBLOCK) {
  			int off = 0;
  			pid_t cpid;
  
  			if (forked) {
  				(void) close(fd);
  				_exit(1);
  			}
  			cpid = fork();
  			if (cpid == -1) {
  				(void) snprintf(errbuf, sizeof(errbuf),
  				    "fork: %s", strerror(errno));
  				(void) close(fd);
  				return (errbuf);
  			}
  			if (cpid) {	/* parent */
  				(void) close(fd);
  				return (NULL);
  			}
  
  			if (pledge("stdio", NULL) == -1)
  				err(1, "pledge");
  
  			forked++;
  			/* wait at most tmout seconds */
  			(void) signal(SIGALRM, SIG_DFL);
  			(void) signal(SIGTERM, SIG_DFL); /* XXX */
  			(void) sigemptyset(&mask);
  			(void) sigprocmask(SIG_SETMASK, &mask, NULL);
  			(void) alarm((u_int)tmout);
  			(void) fcntl(fd, O_NONBLOCK, &off);
  			continue;
  		}
  		/*
  		 * We get ENODEV on a slip line if we're running as root,
  		 * and EIO if the line just went away.
  		 */
  		if (errno == ENODEV || errno == EIO)
  			break;
  		(void) close(fd);
  		if (forked)
  			_exit(1);
  		(void) snprintf(errbuf, sizeof(errbuf),
  		    "%s: %s", device, strerror(errno));
  		return (errbuf);
  	}
  
  	(void) close(fd);
  	if (forked)
  		_exit(0);
  	return (NULL);
  }