https://github.com/sergiusthebest/vctest
A sample that demonstrates RDP8.1 virtual channel bug
https://github.com/sergiusthebest/vctest
bug rdp virtual-channel
Last synced: about 1 month ago
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A sample that demonstrates RDP8.1 virtual channel bug
- Host: GitHub
- URL: https://github.com/sergiusthebest/vctest
- Owner: SergiusTheBest
- Created: 2015-02-09T15:37:42.000Z (about 10 years ago)
- Default Branch: master
- Last Pushed: 2015-05-08T12:13:59.000Z (almost 10 years ago)
- Last Synced: 2025-01-29T10:31:34.771Z (3 months ago)
- Topics: bug, rdp, virtual-channel
- Language: C++
- Size: 262 KB
- Stars: 1
- Watchers: 2
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# VcTest
A sample that demonstrates RDP8.1 virtual channel bug
## The Bug
If RDP 8.1 is active packets with the length of 1591-1596 bytes are working not as expected. Reproduced on Windows 8.1/2012R2.
## Response from Microsoft
* The packet length is reduced from 1600 to 1596 bytes because static virtual channels are run on dynamic ones in RDP8.1.
* The bug is fixed in the latest private build of Windows 10. The latest public build 9926 has the bug.
* Affected systems:
* Windows 7/2008R2 (with RDP 8.1 update)
* Windows 8/2012 (with RDP 8.1 update)
* Windows 8.1/2012R2.
* They are working on a fix for pre-Windows 10 systems.
## Hotfixes
After 2 months Microsoft released hotfixes for this issue:
* https://support.microsoft.com/en-us/kb/3042841/
* https://support.microsoft.com/en-us/kb/3042842/
## How to Run
1. Build a solution with VS2013 (or [download release binaries](//github.com/SergiusTheBest/VcTest/releases/latest)).
2. Copy `VcTestAddin.dll` to `system32` (or `syswow64` on 64-bit windows, in that case you need to [disable 64-bit mstsc.exe](http://blogs.msdn.com/b/notime/archive/2012/12/15/run-32-bit-remote-desktop-rdp-on-windows-64-bit.aspx)).
3. Import `AddinRegistry.reg`.
4. Open a remote session via `mstsc.exe`.
5. Copy `VcTest` into the remote session.
6. Open command prompt and run `VcTest [packet length]`
Update: Added x64 build, so it can be tested on x64 mstsc.
## Test Results
For better reading the test results here are the flag values:
```cpp
#define CHANNEL_FLAG_FIRST 0x01
#define CHANNEL_FLAG_LAST 0x02
```
### Sending 1592 bytes
Windows 8.1 | Windows 8.0
------------| -----------
|
BUG: `CHANNEL_FLAG_LAST` is not set on Windows 8.1.
### Sending 1000 bytes after 1592
Windows 8.1 | Windows 8.0
------------| -----------
|
BUG: The next packet is treated as a continuation of the previous one on Windows 8.1. `CHANNEL_FLAG_FIRST` is not set.
### Sending 1592 bytes after 1592
Windows 8.1 | Windows 8.0
------------| -----------
|
BUG: Packets with the length of 1591-1596 bytes aren't treated as a continuation of the previous packet on Windows 8.1 (like other packets).
### Sending 1600 bytes
Windows 8.1 | Windows 8.0
------------| -----------
|
|
1600 is the length of a virtual channel chunk. On Windows 8.1 it is transmitted as 2 packets while on Windows 8.0 - as 1 packet.
### Sending 1000 bytes
Windows 8.1 | Windows 8.0
------------| -----------
|
This is a positive case where everything goes like it should.
### Sending 2000 bytes
Windows 8.1 | Windows 8.0
------------| -----------
|
|
This is a positive case too but we see the chunk length is not 1600 on Windows 8.1.