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Emulate closefrom() on macOS using proc_pidinfo().

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This avoids relying on /dev/fd which may not exist in a chroot jail.
Adapted from a change in OpenSSH by likan_999.student AT sina.com
This commit is contained in:
Todd C. Miller
2021-09-27 13:44:41 -06:00
parent 73e9256f9d
commit 476f00b82f
4 changed files with 77 additions and 16 deletions
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66
lib/util/closefrom.c
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@@ -1,7 +1,7 @@
/*
* SPDX-License-Identifier: ISC
*
* Copyright (c) 2004-2005, 2007, 2010, 2012-2015, 2017-2018
* Copyright (c) 2004-2005, 2007, 2010, 2012-2015, 2017-2021
* Todd C. Miller <Todd.Miller@sudo.ws>
*
* Permission to use, copy, modify, and distribute this software for any
@@ -29,12 +29,16 @@
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdlib.h>
#include <unistd.h>
#ifdef HAVE_PSTAT_GETPROC
# include <sys/pstat.h>
#else
# include <dirent.h>
#endif
#ifdef HAVE_LIBPROC_H
# include <libproc.h>
#endif
#include "sudo_compat.h"
#include "sudo_util.h"
@@ -44,6 +48,13 @@
# define OPEN_MAX 256
#endif
/* Avoid potential libdispatch crash on macOS when we close its fds. */
#ifdef __APPLE__
# define closefrom_close(x) fcntl((x), F_SETFD, FD_CLOEXEC)
#else
# define closefrom_close(x) close(x)
#endif
/*
* Close all file descriptors greater than or equal to lowfd.
* This is the expensive (fallback) method.
@@ -69,12 +80,7 @@ closefrom_fallback(int lowfd)
maxfd = INT_MAX;
for (fd = lowfd; fd < maxfd; fd++) {
#ifdef __APPLE__
/* Avoid potential libdispatch crash when we close its fds. */
(void) fcntl((int) fd, F_SETFD, FD_CLOEXEC);
#else
(void) close((int) fd);
#endif
(void)closefrom_close((int)fd);
}
}
@@ -91,12 +97,45 @@ sudo_closefrom(int lowfd)
const char *path;
DIR *dirp;
#endif
#if defined(HAVE_PROC_PIDINFO)
struct proc_fdinfo *buf = NULL;
const pid_t pid = getpid();
int i, n, len;
#endif
/* Try the fast method first, if possible. */
#if defined(HAVE_FCNTL_CLOSEM)
if (fcntl(lowfd, F_CLOSEM, 0) != -1)
return;
#endif
#elif defined(HAVE_PROC_PIDINFO)
len = proc_pidinfo(pid, PROC_PIDLISTFDS, 0, NULL, 0);
switch (len) {
case 0:
/* No open files. */
return;
case -1:
/* Fall back on other methods. */
break;
default:
/* Allocate space for 4 extra fds to leave some wiggle room. */
buf = malloc(len + (PROC_PIDLISTFD_SIZE * 4));
if (buf == NULL)
break;
n = proc_pidinfo(pid, PROC_PIDLISTFDS, 0, buf, len);
if (n == -1 || n > len) {
free(buf);
break;
}
n /= PROC_PIDLISTFD_SIZE;
for (i = 0; i < n; i++) {
if (buf[i].proc_fd >= lowfd) {
(void)closefrom_close(buf[i].proc_fd);
}
}
free(buf);
return;
}
#endif /* HAVE_PROC_PIDINFO */
#if defined(HAVE_PSTAT_GETPROC)
/*
* EOVERFLOW is not a fatal error for the fields we use.
@@ -107,7 +146,7 @@ sudo_closefrom(int lowfd)
int fd;
for (fd = lowfd; fd <= pst.pst_highestfd; fd++)
(void) close(fd);
(void)closefrom_close(fd);
return;
}
#elif defined(HAVE_DIRFD)
@@ -123,15 +162,10 @@ sudo_closefrom(int lowfd)
const char *errstr;
int fd = sudo_strtonum(dent->d_name, lowfd, INT_MAX, &errstr);
if (errstr == NULL && fd != dirfd(dirp)) {
# ifdef __APPLE__
/* Avoid potential libdispatch crash when we close its fds. */
(void) fcntl(fd, F_SETFD, FD_CLOEXEC);
# else
(void) close(fd);
# endif
(void)closefrom_close(fd);
}
}
(void) closedir(dirp);
(void)closedir(dirp);
return;
}
#endif /* HAVE_DIRFD */