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cp: make "non-POSIX" cp a bit more consistent

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2009-07-05 13:24:17 +02:00
parent 2d7b5bfa9b
commit 6f58be0748
1 changed files with 28 additions and 34 deletions
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62
libbb/copy_file.c
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@ -6,7 +6,6 @@
* SELinux support by Yuichi Nakamura <ynakam@hitachisoft.jp>
*
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
*
*/
#include "libbb.h"
@ -16,31 +15,33 @@
// Then open w/o EXCL (yes, not unlink!).
// If open still fails and -f, try unlink, then try open again.
// Result: a mess:
// If dest is a softlink, we overwrite softlink's destination!
// If dest is a (sym)link, we overwrite link destination!
// (or fail, if it points to dir/nonexistent location/etc).
// This is strange, but POSIX-correct.
// coreutils cp has --remove-destination to override this...
//
// 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)
// errno must be set to relevant value ("why we cannot create dest?")
// for POSIX mode to give reasonable error message
/* Called if open of destination, link creation etc fails.
* errno must be set to relevant value ("why we cannot create dest?")
* to give reasonable error message */
static int ask_and_unlink(const char *dest, int flags)
{
int e = errno;
#if !ENABLE_FEATURE_NON_POSIX_CP
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);
return -1;
}
#endif
// 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).
// else: act as if -f is always in effect.
// We don't want "cannot create" msg, we want unlink to be done
// (silently unless -i). Why? POSIX cp usually succeeds with
// O_TRUNC open of existing file, and user is left ignorantly happy.
// With above block unconditionally enabled, non-POSIX cp
// will complain a lot more than POSIX one.
// 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) {
// We would not do POSIX insanity. -i asks,
// then _unlinks_ the offender. Presto.
@ -48,7 +49,7 @@ static int ask_and_unlink(const char *dest, int flags)
// Or else we will end up having 3 open()s!
fprintf(stderr, "%s: overwrite '%s'? ", applet_name, dest);
if (!bb_ask_confirmation())
return 0; // not allowed to overwrite
return 0; /* not allowed to overwrite */
}
if (unlink(dest) < 0) {
#if ENABLE_FEATURE_VERBOSE_CP_MESSAGE
@ -56,14 +57,14 @@ static int ask_and_unlink(const char *dest, int flags)
/* e == ENOTDIR is similar: path has non-dir component,
* but in this case we don't even reach copy_file() */
bb_error_msg("cannot create '%s': Path does not exist", dest);
return -1; // error
return -1; /* error */
}
#endif
errno = e;
errno = e; /* do not use errno from unlink */
bb_perror_msg("cannot create '%s'", dest);
return -1; // error
return -1; /* error */
}
return 1; // ok (to try again)
return 1; /* ok (to try again) */
}
/* Return:
@ -85,8 +86,8 @@ int FAST_FUNC copy_file(const char *source, const char *dest, int flags)
#define FLAGS_DEREF (flags & FILEUTILS_DEREFERENCE)
if ((FLAGS_DEREF ? stat : lstat)(source, &source_stat) < 0) {
// This may be a dangling symlink.
// Making [sym]links to dangling symlinks works, so...
/* This may be a dangling symlink.
* Making [sym]links to dangling symlinks works, so... */
if (flags & (FILEUTILS_MAKE_SOFTLINK|FILEUTILS_MAKE_HARDLINK))
goto make_links;
bb_perror_msg("cannot stat '%s'", source);
@ -212,9 +213,9 @@ int FAST_FUNC copy_file(const char *source, const char *dest, int flags)
if (flags & (FILEUTILS_MAKE_SOFTLINK|FILEUTILS_MAKE_HARDLINK)) {
int (*lf)(const char *oldpath, const char *newpath);
make_links:
// Hmm... maybe
// if (DEREF && MAKE_SOFTLINK) source = realpath(source) ?
// (but realpath returns NULL on dangling symlinks...)
/* Hmm... maybe
* if (DEREF && MAKE_SOFTLINK) source = realpath(source) ?
* (but realpath returns NULL on dangling symlinks...) */
lf = (flags & FILEUTILS_MAKE_SOFTLINK) ? symlink : link;
if (lf(source, dest) < 0) {
ovr = ask_and_unlink(dest, flags);
@ -226,7 +227,7 @@ int FAST_FUNC copy_file(const char *source, const char *dest, int flags)
}
}
/* _Not_ jumping to preserve_mode_ugid_time:
* hard/softlinks don't have those */
* (sym)links don't have those */
return 0;
}
@ -274,19 +275,12 @@ int FAST_FUNC copy_file(const char *source, const char *dest, int flags)
if (!S_ISREG(source_stat.st_mode))
new_mode = 0666;
/* POSIX way is a security problem versus symlink attacks,
* we do it only for non-symlinks, and only for non-recursive,
* 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 (!ENABLE_FEATURE_NON_POSIX_CP
|| (dest_exists
&& !(flags & (FILEUTILS_RECUR|FILEUTILS_INTERACTIVE))
&& !S_ISLNK(dest_stat.st_mode))
) {
// POSIX way is a security problem versus (sym)link attacks
if (!ENABLE_FEATURE_NON_POSIX_CP) {
dst_fd = open(dest, O_WRONLY|O_CREAT|O_TRUNC, new_mode);
} else /* safe way: */
} else { /* safe way: */
dst_fd = open(dest, O_WRONLY|O_CREAT|O_EXCL, new_mode);
}
if (dst_fd == -1) {
ovr = ask_and_unlink(dest, flags);
if (ovr <= 0) {