Re[2]: [Full-disclosure] Microsoft Windows 2000/XP/2003/Vista ReadDirectoryChangesW informaton leak Feb 22 2007 12:03PM
Dear Andres Tarasco,

Agree, but actually, I mean to store sensitive data in different
location (different network share).

There will be one more advisory, it will demonstrate symlink-like
attacks on Windows. In the same advisory I plan to discuss problem of
secure data in insecure folder mode deeply.

E.g. it's quite impossible for administrator to _create_ secure folder
in insecure one without not-quite-race conditions this folder will be
available for different bad things (without deleting network share, of
cause). Under POSIX system this problem is solvable with umask, for
Windows it seems it was never discussed.

--Thursday, February 22, 2007, 2:29:49 PM, you wrote to 3APA3A (at) security.nnov (dot) ru [email concealed]:

AT> Hi,

AT> You told that as a workaround that we should never allow "creation of more
AT> secure folder in less secure ones."

AT> I agree but, as i see.., that means that also allowing the "Bypass traverse
AT> checking" policy is also a bad idea.

AT> Anyway, there are several scenarios where we could not protect us against
AT> that threat easily, like for example a shared environment with terminal
AT> server/citrix where all our stored documents can be stolen.
AT> In that case, only a software restriction policy will protect us.

AT> regards,

AT> Andres Tarasco

AT> 2007/2/22, 3APA3A <3APA3A (at) security.nnov (dot) ru [email concealed]>:
>> Title: Microsoft Windows 2000/XP/2003/Vista ReadDirectoryChangesW
>> informaton leak
>> Author: 3APA3A,
>> Affected: Microsoft Windows 2000,XP,2003,Vista
>> Exploitable: Yes
>> Type: Remote (from local network), authentication required
>> (NULL session was not tested).
>> Class: Information leak, insecure design
>> CVE: CVE-2007-0843
>> Original
>> Advisory:
>> SecurityVulns
>> news:
>> Intro:
>> It's very simple yet interesting vulnerability. ReadDirectoryChangesW()
>> API allows application to monitor directory changes in real time.
>> bWatchSubtree parameter of this functions allows to monitor changes
>> within whole directory tree with of monitored directory. To monitor
>> changes directory must be open with LIST (READ) access. Function returns
>> the list of modified files with a type of modification. File
>> modification refers to any modification of file record in directory.
>> Vulnerability:
>> ReadDirectoryChangesW() doesn't check user's permissions for child
>> child objects, making it's possible to retrieve information about
>> objects user has no "LIST" permissions.
>> Impact:
>> Any unprivileged user with LIST access to parent directory can monitor
>> any files in child directories regardless of subdirectories and files
>> permissions. Because by default Windows updates access time of any
>> accessed files on NTFS volumes, it makes it possible for user to gather
>> information about NTFS-protected files, their names and time of access
>> to the files (reading, writing, creation, deletion, renaming, etc).
>> Filenames may contain sensitive information or leak information about
>> user's behavior (e.g. cookies files).
>> In addition to it's own impact, this vulnerability elevates impact of
>> few different vulnerabilities and common practices, to be reported
>> later.
>> Exploit:
>> compiled version of Spydir is available from
>> Usage example:
>> spydir \\corpsrv\corpdata
>> I believe you find this utility useful regardless of this security
>> issue. It shows names of accessed/modified files for given directory in
>> real time (it seems there are non-security bugs in ReadDirectoryChangesW
>> implementations, e.g. you can not see non-ASCII names and some changes
>> are missing).
>> Workaround:
>> Avoid creation of more secure folder in less secure ones. Avoid using
>> sensitive data in documents naming.
>> Vendor (Microsoft):
>> January, 17 2006 Initial vendor notification
>> January, 18 2006 Vendor reply (assigned)
>> January, 26 2006 2nd vendor notification
>> February, 7 2006 3rd vendor notification
>> February, 9 2006 Vendor accepted vulnerability as "service pack
>> class" for Windows XP and Windows 2003.
>> February, 9 2006 Accepted to wait until SP
>> February, 22 2006 Vendor gives SP timelines (late 2006 for W2K3
>> SP2 and 2007 for XP SP3)
>> February, 22 2007 Public release, because Windows Vista is
>> released with same vulnerability.
>> _______________________________________________
>> Full-Disclosure - We believe in it.
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