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[WEB SECURITY] New Whitepaper - .NET Framework Rootkits: Backdoors inside your Framework

From: "Erez Metula" <erezmetula@xxxxxxxxxxxxxx>
Subject: [WEB SECURITY] New Whitepaper - .NET Framework Rootkits: Backdoors inside your Framework
Date: Thu, 13 Nov 2008 17:38:39 +0200
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Paper Name

=3D=3D=3D=3D=3D=3D=3D=3D=3D

=20

.NET Framework Rootkits - Backdoors inside your Framework (Author: Erez
Metula)

=20

=20

Paper Description

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

=20

The paper introduces a new method that enables an attacker to change the
.NET language, and to hide malicious code inside its core.

It covers various ways to develop rootkits for the .NET framework, so
that every EXE/DLL that runs on a modified Framework will behave
differently than what it's supposed to do. Code reviews will not detect
backdoors installed inside the Framework since the payload is not in the
code itself, but rather it is inside the Framework implementation.
Writing Framework rootkits will enable the attacker to install a reverse
shell inside the framework, to steal valuable information, to fixate
encryption keys, disable security checks and to perform other nasty
things as described in this paper.=20

=20

=20

=20

Paper Summary

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

=20

Framework modification can be achieved by tampering with a Framework DLL
and "pushing" it back into the Framework.

The process is composed of several steps, described thoroughly at the
corresponding whitepaper.

It also exposes a flaw in the manner in which a .NET Framework DLL is
loaded, and how it is possible to bypass its signature mechanism.

Instead of re-signing tampered DLL's with a spoofed Microsoft signature
key - surprisingly, it was found during this research that the modified
DLL can be directly copied to the correct location at the file system,
because the SN mechanism does not check the actual signature of a loaded
DLL but blindly loads the DLL based on the directory name with the
corresponding signature name!

It is important to mention that this technique does not requires "full
trust" permissions, which further proves the fact that the GAC / CAS
protection mechanisms are broken.

=20

This paper also introduces ".Net-Sploit" - a new tool for building MSIL
rootkits that will enable the user to inject preloaded/custom payload to
the Framework core DLL.

=20

You can find the detailed whitepaper, .NET-Sploit tool, source code, and
the OWASP presentation at:

http://www.applicationsecurity.co.il/.NET-Framework-Rootkits.aspx

=20


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<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>Paper =
Name<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>=3D=3D=3D=3D=3D=3D=3D=3D=3D<=
o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'><o:p>&nbsp;</o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>.NET Framework Rootkits - =
Backdoors
inside your Framework (Author: Erez Metula)<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>&nbsp;<o:p></o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'><o:p>&nbsp;</o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>Paper =
Description<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'><o:p>&nbsp;</o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>The paper introduces a new =
method
that enables an attacker to change the .NET language, and to hide =
malicious
code inside its core.<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>It covers various ways to =
develop
rootkits for the .NET framework, so that every EXE/DLL that runs on a =
modified
Framework will behave differently than what it's supposed to do. Code =
reviews
will not detect backdoors installed inside the Framework since the =
payload is
not in the code itself, but rather it is inside the Framework =
implementation.
Writing Framework rootkits will enable the attacker to install a reverse =
shell
inside the framework, to steal valuable information, to fixate =
encryption keys,
disable security checks and to perform other nasty things as described =
in this
paper. <o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'><o:p>&nbsp;</o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'><o:p>&nbsp;</o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'><o:p>&nbsp;</o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>Paper =
Summary<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>&nbsp;<o:p></o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>Framework modification can =
be
achieved by tampering with a Framework DLL and &quot;pushing&quot; it =
back into
the Framework.<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>The process is composed of =
several
steps, described thoroughly at the corresponding =
whitepaper.<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>It also exposes a flaw in =
the manner
in which a .NET Framework DLL is loaded, and how it is possible to =
bypass its
signature mechanism.<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>Instead of re-signing =
tampered DLL's
with a spoofed Microsoft signature key - surprisingly, it was found =
during this
research that the modified DLL can be directly copied to the correct =
location
at the file system, because the SN mechanism does not check the actual
signature of a loaded DLL but blindly loads the DLL based on the =
directory name
with the corresponding signature name!<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>It is important to mention =
that this
technique does not requires &quot;full trust&quot; permissions, which =
further
proves the fact that the GAC / CAS protection mechanisms are =
broken.<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'><o:p>&nbsp;</o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>This paper also introduces
&quot;.Net-Sploit&quot; - a new tool for building MSIL rootkits that =
will
enable the user to inject preloaded/custom payload to the Framework core =
DLL.<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'><o:p>&nbsp;</o:p></span></fo=
nt></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>You can find the detailed
whitepaper, .NET-Sploit tool, source code, and the OWASP presentation =
at:<o:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DLTR =
style=3D'text-align:left;text-autospace:none;
direction:ltr;unicode-bidi:embed'><font size=3D2 face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'><a
href=3D"http://www.applicationsecurity.co.il/.NET-Framework-Rootkits.aspx=
">http://www.applicationsecurity.co.il/.NET-Framework-Rootkits.aspx</a><o=
:p></o:p></span></font></p>

<p class=3DMsoNormal dir=3DRTL><font size=3D3 face=3D"Times New =
Roman"><span dir=3DLTR
style=3D'font-size:12.0pt'><o:p>&nbsp;</o:p></span></font></p>

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