-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 NTFS and PGP interact to expose EFS encrypted data © 2002 Ry Jones, Airgap Networks. Summary: NTFS, a feature of Windows XP, supports an "encrypted" attribute. PGP 7.0.3 Freeware, a product of Network Associates, supports wiping files as they are deleted. If you enable file wiping and then set the "encrypted" attribute on a folder, copies of the contents are left un-encrypted on the file system. Details: As explorer works it's way through the file system encrypting the contents, it first renames the source file to a name in the format of "EFSn.TMP" where n is an increasing series of integers starting at 0. It then encrypts the file into a target file with the same name as the original. The permissions on the temp file are set to a very restrictive level; the temp file is then deleted. However, if you have set PGP to wipe deleted files, it appears PGP intercepts the deletion of the file. PGP, running as the user, has insufficient privilege to delete the file, and leaves the temp file in place. Anyone who recovers the hard drive can take ownership of these temp files and read them. Also, in the default setting, hidden files are not shown in explorer, so a user may not be aware that the temp files exist at all. Any administrator may take ownership of the temp files and read the data. Repro: 1: create a directory "efs-pgp-interaction-bug". Copy a text file into the directory. 2: right click on the PGP icon. Set the "Automatically wipe on delete" flag. Click OK. 3: right click on the "efs-pgp-interaction-bug" directory in explorer. Click properties, advanced, and check the "Encrypt contents to secure data" flag. Click OK, OK. 4: double click on efs-pgp-interaction-bug. If you have set the "show hidden files and folders" flag (tools, folder options, view, show hidden files and folders, OK) you well see the EFSn.TMP files. Attempting to open the temp files will result in an error (depending on application). Vim reports "[Permission Denied]". 5: hit the backspace key. Right click on the efs-pgp-interaction-bug directory. Select sharing and security; select security, advanced. Check the "replace permission entries on all child objects…" check box and click OK. Click "Yes", "OK". 6: Re-open efs-pgp-interaction-bug and right click on the temp file (EFS0.TMP). Select Open With, Notepad. View your file. Workaround: Do not enable PGP's Wipe Deleted Files option if you are using Encrypted NTFS. Vendor Response: This issue has been resolved, and a hot fix for PGP Desktop Security v7.0.x, PGP Corporate Desktop v7.1.x and PGPfreeware v7.0.x (all for Windows 2000) is available at http://www.nai.com/naicommon/download/upgrade/upgrades-patch.asp. Users should be aware that Win2K EFS does NOT wipe the contents of files that are encrypted according to the steps above. The PGP Wipe Free Space feature to ensure that the clear text has been wiped. Discovered: 10 MAR 2002 Sent to vendors: 17 MAR 2002 Submitted to NTBugtraq, Bugtraq: 08 MAY 2002 Thanks to: Russ of NTBugtraq for driving the issue with Microsoft and NAI much more effectively than I ever would have. There never would have been a resolution without his efforts. -----BEGIN PGP SIGNATURE----- Version: PGP 7.0.4 iQA/AwUBPNl9sxLoz2rGojSMEQIqXACg0CbHJHJOm0bh9gqBfr5HvdIz+ZAAn2Ve HOJ1qt1tkX7wnU5qpQxOOXiU =0LBF -----END PGP SIGNATURE-----
