[jira] [Created] (GUACAMOLE-1784) guac_user instances must only be referenced from user callbacks

["Mike Jumper (Jira)" <ji...@apache.org>]

Mike Jumper created GUACAMOLE-1784:
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             Summary: guac_user instances must only be referenced from user callbacks
                 Key: GUACAMOLE-1784
                 URL: https://issues.apache.org/jira/browse/GUACAMOLE-1784
             Project: Guacamole
          Issue Type: Bug
          Components: guacamole-server
            Reporter: Mike Jumper


An instance of {{guac_user}} has a lifecycle that may result in that {{guac_user}} becoming invalid at any moment _except_ within the context of a callback directly related to that user. The {{guac_client_for_user()}} function exists to provide a mechanism for referencing a {{guac_user}} without a corresponding callback, but this call is missing in a few locations, resulting in potential segfaults.

For example:
{code:c}
static void guac_rdp_audio_buffer_ack(guac_rdp_audio_buffer* audio_buffer,
        const char* message, guac_protocol_status status) {

    guac_user* user = audio_buffer->user;
    guac_stream* stream = audio_buffer->stream;

    ...
    guac_protocol_send_ack(user->socket, stream, message, status);
    ...

}   
{code}
The above is incorrect because {{user->socket}} is being accessed outside a user-related callback and without using {{{}guac_client_for_user(){}}}. If the {{user}} turns out to not be valid, this will segfault.

We should fix the above, look through the code for other references to {{guac_user}} outside a user-related callback, and fix those as well.



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