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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
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@ -114,6 +114,16 @@ config FEATURE_EDITING_ASK_TERMINAL
correctly, or want to save on code size (about 300 bytes), correctly, or want to save on code size (about 300 bytes),
then do not turn this option on. 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 config FEATURE_VERBOSE_CP_MESSAGE
bool "Give more precise messages when copy fails (cp, mv etc)" bool "Give more precise messages when copy fails (cp, mv etc)"
default n default n

14
libbb/copy_file.c
View File

@ -8,9 +8,10 @@
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details. * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
* *
*/ */
#include "libbb.h" #include "libbb.h"
// FEATURE_NON_POSIX_CP:
//
// POSIX: if exists and -i, ask (w/o -i assume yes). // POSIX: if exists and -i, ask (w/o -i assume yes).
// Then open w/o EXCL (yes, not unlink!). // Then open w/o EXCL (yes, not unlink!).
// If open still fails and -f, try unlink, then try open again. // 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" // 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) // 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?") // errno must be set to relevant value ("why we cannot create dest?")
// for POSIX mode to give reasonable error message // for POSIX mode to give reasonable error message
static int ask_and_unlink(const char *dest, int flags) static int ask_and_unlink(const char *dest, int flags)
{ {
int e = errno; int e = errno;
#if DO_POSIX_CP #if !ENABLE_FEATURE_NON_POSIX_CP
if (!(flags & (FILEUTILS_FORCE|FILEUTILS_INTERACTIVE))) { if (!(flags & (FILEUTILS_FORCE|FILEUTILS_INTERACTIVE))) {
// Either it exists, or the *path* doesnt exist // Either it exists, or the *path* doesnt exist
bb_perror_msg("cannot create '%s'", dest); bb_perror_msg("cannot create '%s'", dest);
return -1; return -1;
} }
#endif #endif
// If !DO_POSIX_CP, act as if -f is always in effect - we don't want // If ENABLE_FEATURE_NON_POSIX_CP, act as if -f is always in effect
// "cannot create" msg, we want unlink to be done (silently unless -i). // - 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? // TODO: maybe we should do it only if ctty is present?
if (flags & FILEUTILS_INTERACTIVE) { if (flags & FILEUTILS_INTERACTIVE) {
@ -279,7 +279,7 @@ int FAST_FUNC copy_file(const char *source, const char *dest, int flags)
* non-interactive cp. NB: it is still racy * non-interactive cp. NB: it is still racy
* for "cp file /home/bad_user/file" case * for "cp file /home/bad_user/file" case
* (user can rm file and create a link to /etc/passwd) */ * (user can rm file and create a link to /etc/passwd) */
if (DO_POSIX_CP if (!ENABLE_FEATURE_NON_POSIX_CP
|| (dest_exists || (dest_exists
&& !(flags & (FILEUTILS_RECUR|FILEUTILS_INTERACTIVE)) && !(flags & (FILEUTILS_RECUR|FILEUTILS_INTERACTIVE))
&& !S_ISLNK(dest_stat.st_mode)) && !S_ISLNK(dest_stat.st_mode))