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cp: by popular demand, make it POSIX compliant (but less safe)

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2009-07-05 12:49:29 +02:00
parent 09e63bb81f
commit 2d7b5bfa9b
2 changed files with 19 additions and 9 deletions
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10
libbb/Config.in
View File

@ -114,6 +114,16 @@ config FEATURE_EDITING_ASK_TERMINAL
correctly, or want to save on code size (about 300 bytes),
then do not turn this option on.
config FEATURE_NON_POSIX_CP
bool "Non-POSIX, but safer, copying to special nodes"
default y
help
With this option, "cp file symlink" will delete symlink
and create a regular file. This does not conform to POSIX,
but prevents a symlink attack.
Similarly, "cp file device" will not send file's data
to the device.
config FEATURE_VERBOSE_CP_MESSAGE
bool "Give more precise messages when copy fails (cp, mv etc)"
default n

18
libbb/copy_file.c
View File

@ -8,9 +8,10 @@
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
*
*/
#include "libbb.h"
// FEATURE_NON_POSIX_CP:
//
// POSIX: if exists and -i, ask (w/o -i assume yes).
// Then open w/o EXCL (yes, not unlink!).
// If open still fails and -f, try unlink, then try open again.
@ -23,22 +24,21 @@
// NB: we have special code which still allows for "cp file /dev/node"
// to work POSIX-ly (the only realistic case where it makes sense)
#define DO_POSIX_CP 0 /* 1 - POSIX behavior, 0 - safe behavior */
// errno must be set to relevant value ("why we cannot create dest?")
// for POSIX mode to give reasonable error message
static int ask_and_unlink(const char *dest, int flags)
{
int e = errno;
#if DO_POSIX_CP
#if !ENABLE_FEATURE_NON_POSIX_CP
if (!(flags & (FILEUTILS_FORCE|FILEUTILS_INTERACTIVE))) {
// Either it exists, or the *path* doesnt exist
bb_perror_msg("cannot create '%s'", dest);
return -1;
}
#endif
// If !DO_POSIX_CP, act as if -f is always in effect - we don't want
// "cannot create" msg, we want unlink to be done (silently unless -i).
// If ENABLE_FEATURE_NON_POSIX_CP, act as if -f is always in effect
// - we don't want "cannot create" msg, we want unlink to be done
// (silently unless -i).
// TODO: maybe we should do it only if ctty is present?
if (flags & FILEUTILS_INTERACTIVE) {
@ -279,10 +279,10 @@ int FAST_FUNC copy_file(const char *source, const char *dest, int flags)
* non-interactive cp. NB: it is still racy
* for "cp file /home/bad_user/file" case
* (user can rm file and create a link to /etc/passwd) */
if (DO_POSIX_CP
if (!ENABLE_FEATURE_NON_POSIX_CP
|| (dest_exists
&& !(flags & (FILEUTILS_RECUR|FILEUTILS_INTERACTIVE))
&& !S_ISLNK(dest_stat.st_mode))
&& !(flags & (FILEUTILS_RECUR|FILEUTILS_INTERACTIVE))
&& !S_ISLNK(dest_stat.st_mode))
) {
dst_fd = open(dest, O_WRONLY|O_CREAT|O_TRUNC, new_mode);
} else /* safe way: */