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qga/win32: Use rundll for VSS installation

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The custom action uses cmd.exe to run VSS Service installation
and removal which causes an interactive command shell to spawn.
This shell can be used to execute any commands as a SYSTEM user.
Even if call qemu-ga.exe directly the interactive command shell
will be spawned as qemu-ga.exe is a console application and used
by users from the console as well as a service.

As VSS Service runs from DLL which contains the installer and
uninstaller code, it can be run directly by rundll32.exe without
any interactive command shell.

Add specific entry points for rundll which is just a wrapper
for COMRegister/COMUnregister functions with proper arguments.

resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2167423
fixes: CVE-2023-0664 (part 2 of 2)

Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Reviewed-by: Yan Vugenfirer <yvugenfi@redhat.com>
Reported-by: Brian Wiltse <brian.wiltse@live.com>
This commit is contained in:
Konstantin Kostiuk 2023-03-03 21:20:08 +02:00
parent 88288c2a51
commit 07ce178a2b
3 changed files with 16 additions and 5 deletions
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10
qga/installer/qemu-ga.wxs
View File

@ -127,22 +127,22 @@
</Directory>
</Directory>
<Property Id="cmd" Value="cmd.exe"/>
<Property Id="rundll" Value="rundll32.exe"/>
<Property Id="REINSTALLMODE" Value="amus"/>
<?ifdef var.InstallVss?>
<CustomAction Id="RegisterCom"
ExeCommand='/c "[qemu_ga_directory]qemu-ga.exe" -s vss-install'
ExeCommand='"[qemu_ga_directory]qga-vss.dll",DLLCOMRegister'
Execute="deferred"
Property="cmd"
Property="rundll"
Impersonate="no"
Return="check"
>
</CustomAction>
<CustomAction Id="UnRegisterCom"
ExeCommand='/c "[qemu_ga_directory]qemu-ga.exe" -s vss-uninstall'
ExeCommand='"[qemu_ga_directory]qga-vss.dll",DLLCOMUnregister'
Execute="deferred"
Property="cmd"
Property="rundll"
Impersonate="no"
Return="check"
>

9
qga/vss-win32/install.cpp
View File

@ -357,6 +357,15 @@ out:
return hr;
}
STDAPI_(void) CALLBACK DLLCOMRegister(HWND, HINSTANCE, LPSTR, int)
{
COMRegister();
}
STDAPI_(void) CALLBACK DLLCOMUnregister(HWND, HINSTANCE, LPSTR, int)
{
COMUnregister();
}
static BOOL CreateRegistryKey(LPCTSTR key, LPCTSTR value, LPCTSTR data)
{

2
qga/vss-win32/qga-vss.def
View File

@ -1,6 +1,8 @@
LIBRARY "QGA-PROVIDER.DLL"
EXPORTS
DLLCOMRegister
DLLCOMUnregister
COMRegister PRIVATE
COMUnregister PRIVATE
DllCanUnloadNow PRIVATE