Mike Powers created GUACAMOLE-1717:
--------------------------------------
Summary: Cursor Improperly Initialized when Connecting to Gnome
Remote Desktop via RDP
Key: GUACAMOLE-1717
URL: https://issues.apache.org/jira/browse/GUACAMOLE-1717
Project: Guacamole
Issue Type: Bug
Components: RDP
Affects Versions: 1.4.0
Reporter: Mike Powers
When connecting to a [Gnome Remote
Desktop|https://gitlab.gnome.org/GNOME/gnome-remote-desktop] RDP instance the
mouse cursor is created but the image data is never copied into the cursor's
pixel buffer resulting in a garbled bitmap containing uninitialized data:
!image-2022-11-20-19-59-57-478.png|width=664,height=311!
This appears to happen because of this guard condition in
src/protocols/rdp/pointer.c:
```c
if (pointer->andMaskData && pointer->xorMaskData)
```
It appears when Gnome Remote Desktop [initializes
cursors|https://gitlab.gnome.org/GNOME/gnome-remote-desktop/-/blob/master/src/grd-session-rdp.c#L591]
when starting the session it sets `andMaskData` to NULL with a length of zero:
```c
pointer_color->lengthAndMask = 0;
pointer_color->lengthXorMask = xor_mask_length;
pointer_color->andMaskData = NULL;
```
This causes the guard condition in the RDP plugin to fail to copy bitmap data
from the server. It appears as if FreeRDP [correctly
handles|https://github.com/FreeRDP/FreeRDP/blob/eb7adaec46eceaa4b247dc664dcce2d65a5edead/libfreerdp/codec/color.c#L322]
the image data in `freerdp_image_copy_from_pointer_data` if `lengthAndMask` ==
0:
```c
if (!xorMask || (xorMaskLength == 0))
return FALSE;
if (!andMask || (andMaskLength == 0))
return FALSE;
```
I believe this guard condition is probably not necessary; removing it resolves
the issue for me. I tested against both Gnome Remote Desktop and a Windows 11
Professional instance.
Please let me know if you'd like any additional information or testing done.
This was tested with Guacamole 1.4.0 from Docker Hub (guacamole/guacamole:1.4.0
and guacamole/guacd:1.4.0). Testing against a fresh install of Fedora 37/Gnome
43.
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