mike-jumper commented on a change in pull request #327:
URL: https://github.com/apache/guacamole-server/pull/327#discussion_r566599491
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File path: src/protocols/vnc/vnc.c
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@@ -385,6 +385,12 @@ void* guac_vnc_client_thread(void* data) {
}
#endif
+ /* Disable remote console (Server input) */
+ if (settings->disable_server_input) {
+ rfbBool success = PermitServerInput(rfb_client, 1);
+ guac_client_log(client, GUAC_LOG_INFO, "Disabling server input %s.",
success ? "succeeded" : "failed");
Review comment:
There is admittedly not much documentation on the return value of
`PermitServerInput()`, but reading through the libvncclient code, the value
doesn't appear to indicate whether disabling input succeeded:
```c
/*
* UltraVNC Server Input Disable
* Apparently, the remote client can *prevent* the local user from
interacting with the display
* I would think this is extremely helpful when used in a HelpDesk situation
*/
rfbBool PermitServerInput(rfbClient* client, int enabled)
{
rfbSetServerInputMsg msg;
if (!SupportsClient2Server(client, rfbSetServerInput)) return TRUE;
/* enabled==1, then server input from local keyboard is disabled */
msg.type = rfbSetServerInput;
msg.status = (enabled ? 1 : 0);
msg.pad = 0;
return (WriteToRFBServer(client, (char *)&msg, sz_rfbSetServerInputMsg)
? TRUE : FALSE);
}
```
(https://github.com/LibVNC/libvncserver/blob/c82b3abb369983cd737190331b897814a580a980/libvncclient/rfbproto.c#L1502-L1517)
Given the above, it looks like:
* If the VNC server supports the relevant message, the return value
indicates only if the message was successfully sent, not whether the server
honored the message.
* If the VNC server _doesn't_ support the relevant message,
`PermitServerInput()` pretends to succeed.
The silent success of `PermitServerInput()` makes this log message less
useful. If you want to keep the message, I suggest moving it to the
`GUAC_LOG_DEBUG` level and rephrasing to capture only what we know.
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