-----BEGIN PGP SIGNED MESSAGE-----

Hash: SHA1

Hello,

I have come across a possible problem in the way PGP handles

signature verification.

The problem lies in the fact that PGP will strip OLE objects inserted

in an e-mail and verify the message signature based only on the text,

not informing the user that objects were striped.

A WordPad document can be inserted in the e-mail as an OLE object,

having the same font style and size as the original message.

An attacker would take a signed message and insert such word document

anywhere in the message as an OLE object and when the recepient

checks the signature - the wordpad document is stripped and the

signature would be valid - The attack would only work if the

recepient does not use the pgp verified message "text viewer" dialog

box to read the message but uses it only to verify the validity of

the signature.

This was tested with pgp.com's PGP version 8.0, other versions may be

vulnerable as well.

I have experimented with older versions and they only worked in the

hash field of the PGP header which is stripped before the message is

verified and the same attack can be performed but text would only be

added at the beginning of the message.

Regards,

Avri Schneider

http://pgp.mit.edu 0x44F87D04

-----BEGIN PGP SIGNATURE-----

Version: PGP 8.0 - not licensed for commercial use: www.pgp.com

iQA/AwUBPm0AKGelhJFE+H0EEQIyxACg7HTH5UjaSGy5D3cobYx0h6io1lsAnRk1

cWnPtLBNw3G3XBkZuuUXPgIg

=fWay

-----END PGP SIGNATURE-----

[ reply ]