Security advisory
Advisory released Mar 23 1999
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Application: Lotus Notes Client (Version 4.5, probably others)
Impact: Encrypted mail sent from the Notes client may
traverse the network in the clear and may be stored
on the mail server unencrypted.
Author: Martin Bartosch
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Synopsis
--------
When performing network analysis experiments with the Lotus Notes Client
a very subtle bug was discovered that may lead to inadvertent revelation of
confidential information.
Usually the Notes client sends at least two copies of a newly created mail.
One copy is sent to the recipient, the other is stored in the "Sent Mail"
folder of the sender's Notes server.
If an encrypted mail is to be sent and the conditions for this bug are
met, the copy for the sender's "Sent Mail" folder is not encrypted. As a
result, the message is sent to the Notes server in the clear and stored
on the Notes server unencrypted.
The message may thus be intercepted and read by analyzing the network
traffic between the sender's Notes client and the server or by directly
accessing the "Sent Mail" folder on the Notes server.
The user is not given any warning or notification about the problem, and
the problem causes almost no noticable side effects. As a result, if a
user is affected by the problem, this will probably remain unnoticed.
Lotus is currently working on the problem, a detailed analysis and official
fixes may be available soon. Once this is available, it should be preferred
to the workaround presented in this document.
Details
-------
The problem seems to result from an inadequate check condition in the
client code.
Traditionally Windows, DOS and OS/2 use the backslash character ('\') as
a path separator, whereas Unix systems use the slash ('/') for this
purpose. Applications that deal with both styles need to be aware of the
problem and have to take care of paths passed to applications or services
on other systems.
The user's database usually is located on a remote server. Though Notes
clients are normally Windows style systems, the servers may either run
Windows, OS/2 or Unix as the server operating system. Thus Notes needs to
take care of proper translation of file paths as files are accessed on
various platforms.
Notes accesses databases by specifying the server and the path to
the database. In order to open a user's database in the first place, the
user needs to enter the correct path to the database or traverse the
directory tree on the server. When the database has been opened, Notes
remembers the path to the database for subsequent access to this database.
Internally the Notes client seems to store the path to the database using
the client operating system file naming conventions. In particular, on
Windows or OS/2 platforms, Notes uses Backslash characters ('\') as path
separators.
The current Notes environment settings may be changed by opening the
environment document (File/Mobile/Edit current environment). In the second
entry of the section "Mail" the path to the mail file can be changed by
the user.
Notes uses this entry for various purposes. One of these is the periodical
check for new mail or agenda events. (If the user specifies an incorrect
path here, mail notification does not work any longer.)
To address the backslash-slash problem, Notes seems to translate
any path entered by the user into the proper representation needed for
accessing the service required. Apparently it does not matter at all if
paths are entered with slashes or backslashes as path separators. The GUI
dialogs accept any spelling as well as the environment document mentioned
above.
However, if for some reason the environment document of a Windows style
client specifies the mail file with *slashes* as a path separator (like
e. g. mail/users/user.nsf instead of mail\users\user.nsf) Notes does
a proper translation of the path and almost all functions will work as
expected.
Except for one side effect: Notes does not recognize the specified
database as the user's mail database. Probably a simple string compare
between the currently opened mail database and the database path of the
environment document is performed, and this comparison fails because of
the different representation of paths.
The resulting effect: if an encrypted mail is to be sent and the
environment document does contain a mail database path with 'incorrect'
path separators as seen from the client OS view, the mail copy for the
user's "Sent Mail" folder is being sent to the user's database in the
plain and stored unencrypted on the server. The contents of the message
may be read in plain text by sniffing on the network or by directly
accessing the notes database.
The behaviour described can be reproduced with almost any Notes client
and server combination. Even if both the server and client use the
same operating system, it is still possible to enter the mail path
separated with slash characters. The Notes client will behave as described
above.
Detection
---------
- compose a new mail message
- address this message to some other user
- using the mail properties dialog enable encryption for this individual
message
- send message
- change to the "Sent Mail" folder of your mail database
- right-click on the sent message once
- open the properties dialog for this document
- choose "fields" in the document properties
- check existence of the fields "$Seal", "$SealData" and "Body"
Under normal circumstances the "$Seal"/"$SealData" and "Body" fields are
mutually exclusive.
The existence of "$Seal" and "$SealData" usually indicate that the message
was properly encrypted.
If the field "Body" exists, this message is stored in the plain on the
server and was transferred unencrypted across the network.
Alternatively the network traffic can be analyzed while sending an
encrypted mail. This is how the bug was discovered in the first place.
Workaround
----------
The workaround described here may be an incomplete fix for the problem;
the problem may be triggered by other conditions as well. As Lotus is
actively investigating on the problem, the solution presented by Lotus
may be more general and should be preferred once it is available.
First method:
Open your environment document. The path to the database must *not*
contain any path separator characters that are not natively used by
the client operating system.
When using a Windows or OS/2 environment, the path must only contain
backslash '\' characters.
Example:
Mail File: mail\path\to\user.nsf * OK *
Mail File: mail/path/to/user.nsf * DANGER! *
A client restart is required to make the changes effective.
Second method:
In your global preferences check the "Encrypt saved mail" box. Every
message you send will be encrypted when saving the message to the "Sent
Mail" folder on the server.
Use both methods to be sure that mail sent by the client is not sent and
stored in the clear. Be aware that using the second methond will
result in encryption of the whole database and that loss of your
passphrase or Notes ID will effectively cause loss of your mail database
contents.
Vendor activities
-----------------
Lotus has been informed of this bug and is currently working on the problem.
An official fix or workaround will be published by Lotus.
Credits
-------
Michael Doberenz; Michael Popp
whose network analysis experiments revealed that there was a problem
in the first place
Artur Hahn
found the real reason (path separator issue) for the Notes encryption
problem
--
Martin Bartosch bartoschat_private
This message and any statements expressed therein are those of myself
and not of the Deutsche Bank AG or its subsidiary companies.
This archive was generated by hypermail 2b30 : Fri Apr 13 2001 - 14:39:28 PDT