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* sysdeps/generic/libc-start.c: For SUID binaries check whether
	the standard file descriptors are open.
	Reported by Chris Evans <chris@ferret.lmh.ox.ac.uk>.
This commit is contained in:
Ulrich Drepper 1999-07-09 16:18:17 +00:00
parent 3eb515a631
commit a828c2f533
2 changed files with 46 additions and 1 deletions
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4
ChangeLog
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@ -1,5 +1,9 @@
1999-07-09 Ulrich Drepper <drepper@cygnus.com>
* sysdeps/generic/libc-start.c: For SUID binaries check whether
the standard file descriptors are open.
Reported by Chris Evans <chris@ferret.lmh.ox.ac.uk>.
* sysdeps/unix/sysv/linux/syscalls.list: Remove mmap64 alias for mmap.
* sysdeps/unix/sysv/linux/mmap64.c: Test whether mapped area is in
range of mmap. If not fail.

43
sysdeps/generic/libc-start.c
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@ -1,4 +1,4 @@
/* Copyright (C) 1998 Free Software Foundation, Inc.
/* Copyright (C) 1998, 1999 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@ -16,8 +16,12 @@
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <elf/ldsodefs.h>
extern void __libc_init_first (int argc, char **argv, char **envp);
@ -27,6 +31,9 @@ weak_extern (_dl_starting_up)
extern int __libc_multiple_libcs;
extern void *__libc_stack_end;
/* Prototype for local function. */
static void check_standard_fds (void);
int
__libc_start_main (int (*main) (int, char **, char **), int argc,
char **argv, void (*init) (void), void (*fini) (void),
@ -47,6 +54,11 @@ __libc_start_main (int (*main) (int, char **, char **), int argc,
/* Set the global _environ variable correctly. */
__environ = &argv[argc + 1];
/* Some security at this point. Prevent starting a SUID binary where
the standard file descriptors are not opened. */
if (__libc_enable_secure)
check_standard_fds ();
/* Register the destructor of the dynamic linker if there is any. */
if (rtld_fini != NULL)
atexit (rtld_fini);
@ -77,3 +89,32 @@ __libc_start_main (int (*main) (int, char **, char **), int argc,
exit ((*main) (argc, argv, __environ));
}
/* Should other OSes (e.g., Hurd) have different versions which can
be written in a better way? */
static void
check_one_fd (int fd, int mode)
{
if (__fcntl (fd, F_GETFD) == -1 && errno == EBADF)
{
/* Something is wrong with this descriptor, it's probably not
opened. Open /dev/null so that the SUID program we are
about to start does not accidently use this descriptor. */
int nullfd = __open (_PATH_DEVNULL, mode);
if (nullfd == -1)
/* We cannot even given an error message here since it would
run into the same problems. */
abort ();
}
}
static void
check_standard_fds (void)
{
/* Check all three standard file descriptors. */
check_one_fd (STDIN_FILENO, O_RDONLY);
check_one_fd (STDOUT_FILENO, O_RDWR);
check_one_fd (STDERR_FILENO, O_RDWR);
}