9 Advanced topics
•reverse the order of byte 6 and 7.
Using this conversion you will get identical results when converting the binary UUID
to the string representation.
The second arguments contains information about the guest authentication status.
Forthe first call, it is always set to VRDPAuthGuestNotAsked. In case the function
returns VRDPAuthDelegateToGuest, a guest authentication will be attempted and
another call to the method is made with its result. This can be either granted / de-
nied or no judgement (the guest component chose for whatever reason to not make
a decision). In case there is a problem with the guest authentication module (e.g.
the Additions are not installed or not running or the guest did not respond within a
timeout), the “not reacted” status will be returned.
9.4 Secure labeling with VBoxSDL
When running guest operating systems in fullscreen mode, the guest operating system
usually has control over the whole screen. This could present a security risk as the
guest operating system might fool the user into thinking that it is either a different
system (which might have a higher security level) or it might present messages on the
screen that appear to stem from the host operating system.
In order to protect the user against the above mentioned security risks, the secure
labeling feature has been developed. Secure labeling is currently available only for
VBoxSDL. When enabled, a portion of the display area is reserved for a label in which
a user defined message is displayed. The label height in set to 20 pixels in VBoxSDL.
The label font color and background color can be optionally set as hexadecimal RGB
color values. The following syntax is used to enable secure labeling:
VBoxSDL --startvm VMNAME
--securelabel --seclabelfnt ~/fonts/arial.ttf
--seclabelsiz 14 --seclabelfgcol 00FF00 --seclabelbgcol 00FFFF
In addition to enabling secure labeling, a TrueTypefont has to be supplied. Touse
another font size than 12 point use the parameter --seclabelsiz.
The label text can be set with
VBoxManage setextradata VMNAME "VBoxSDL/SecureLabel" "The Label"
Changing this label will take effect immediately.
Typically,full screen resolutions are limited to certain “standard” geometries such
as 1024 x 768. Increasing this by twenty lines is not usually feasible, so in most cases,
VBoxSDLwill chose the next higher resolution, e.g. 1280x 1024 and the guest’s screen
will not cover the whole display surface. If VBoxSDL is unable to choose a higher
resolution,the secure label will be painted on top of the guest’s screen surface. Inorder
to address the problem of the bottom part of the guest screen being hidden, VBoxSDL
can provide custom video modes to the guest that are reduced by the height of the
label. For Windows guests and recent Solaris and Linux guests, the VirtualBox Guest
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