diff options
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/generic/check_fds.c | 62 | ||||
| -rw-r--r-- | sysdeps/generic/libc-start.c | 43 |
2 files changed, 69 insertions, 36 deletions
diff --git a/sysdeps/generic/check_fds.c b/sysdeps/generic/check_fds.c new file mode 100644 index 0000000000..4eea168794 --- /dev/null +++ b/sysdeps/generic/check_fds.c @@ -0,0 +1,62 @@ +/* Copyright (C) 2000 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 + modify it under the terms of the GNU Library General Public License as + published by the Free Software Foundation; either version 2 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + 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 <unistd.h> + +/* Try to get a machine dependent instruction which will make the + program crash. This is used in case everything else fails. */ +#include <abort-instr.h> +#ifndef ABORT_INSTRUCTION +/* No such instruction is available. */ +# define ABORT_INSTRUCTION +#endif + + +/* 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 (__builtin_expect (__libc_fcntl (fd, F_GETFD), 0) == -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 = __libc_open (_PATH_DEVNULL, mode); + if (__builtin_expect (nullfd, 0) == -1) + /* We cannot even give an error message here since it would + run into the same problems. */ + while (1) + /* Try for ever and ever. */ + ABORT_INSTRUCTION; + } +} + + +void +__libc_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); +} diff --git a/sysdeps/generic/libc-start.c b/sysdeps/generic/libc-start.c index fe4966cd46..f5486f91e1 100644 --- a/sysdeps/generic/libc-start.c +++ b/sysdeps/generic/libc-start.c @@ -16,12 +16,8 @@ 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 <ldsodefs.h> extern void __libc_init_first (int argc, char **argv, char **envp); @@ -32,7 +28,7 @@ extern int __libc_multiple_libcs; extern void *__libc_stack_end; /* Prototype for local function. */ -static void check_standard_fds (void); +extern void __libc_check_standard_fds (void); int __libc_start_main (int (*main) (int, char **, char **), int argc, @@ -54,10 +50,14 @@ __libc_start_main (int (*main) (int, char **, char **), int argc, /* Set the global _environ variable correctly. */ __environ = &argv[argc + 1]; +#ifndef SHARED /* Some security at this point. Prevent starting a SUID binary where - the standard file descriptors are not opened. */ + the standard file descriptors are not opened. We have to do this + only for statically linked applications since otherwise the dynamic + loader did the work already. */ if (__builtin_expect (__libc_enable_secure, 0)) - check_standard_fds (); + __libc_check_standard_fds (); +#endif /* Register the destructor of the dynamic linker if there is any. */ if (__builtin_expect (rtld_fini != NULL, 1)) @@ -89,32 +89,3 @@ __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 (__libc_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 = __libc_open (_PATH_DEVNULL, mode); - if (nullfd == -1) - /* We cannot even give 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); -} |