Open Stack

Hi,

In spiceconsole when sending request to websocket server "payload" of
websocket is getting converted to javascript ArrayBuffer
(https://github.com/metacloud/spice-html5/blob/master/spiceconn.js#L126)
and then while converting "message" to arraybuffer connection_id is
getting converted to 32 bit integer (https://github.com/metacloud/spice-
html5/blob/master/spicemsg.js#L118). This connection_id then gets
encrypted (using anding and bit shifting of 32 bit integer)
(https://github.com/metacloud/spice-
html5/blob/master/spicedataview.js#L84).

At the servers side we get this "message" in recv_frames method of websocket(https://github.com/kanaka/websockify/blob/master/websockify/websocket.py#L337). This message is then decrypted and we get payload in hex format (https://github.com/kanaka/websockify/blob/master/websockify/websocket.py#L348). In this payload first four bytes is connection_id but it is in hex encrypted format.
As data received from client is in hex format, its difficult to retrive the connection_id in user readable format.

To overcome this issue, IMO the sessions need to be managed only in case of NoVncConsole and if the console is SpiceConsole then  there is no need to manage the sessions.
For this purpose one flag (is_vnc = true/false) will be passed from novncproxy to determine the console type while creating the server object(websocketproxy.NovaWebSocketProxy).

Please let me know if you found any workaround for the same.

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https://bugs.launchpad.net/bugs/1227575

Title:
  DoS style attack on noVNC server can lead to service interruption or
  disruption

Status in OpenStack Compute (Nova):
  In Progress
Status in OpenStack Security Notes:
  New

Bug description:
  There is no limiting on the number of VNC sessions that can be created for a single user's VNC token.
  Any attempt to create multiple (say hundreds or thousands) of websocket connections to the VNC server
  results in many connection timeouts. Due to these connection timeout error, other users trying to access their 
  VM's VNC console cannot do so.

  A sample script that tries to create 100,000 connections to Nova noVNC proxy, shows timeout errors
  Script: http://paste.openstack.org/show/47254/

  Script output.... connections get timed out after a while
  -------------------
  ....
  ..

  Creating Connection
  Receiving...
  Received 'RFB 003.008
  '
  Creating Connection
  Receiving...
  Received 'RFB 003.008
  '
  Creating Connection
  Receiving...
  Received 'RFB 003.008
  '
  Creating Connection
  Receiving...
  Received 'RFB 003.008
  '
  Creating Connection
  Receiving...
  Received 'RFB 003.008
  '
  Creating Connection
  Receiving...
  Received 'RFB 003.008
  '
  Creating Connection
  Receiving...
  timed out
  Creating Connection
  Receiving...
  timed out
  Creating Connection
  Receiving...
  timed out
  Creating Connection
  Receiving...
  timed out
  Creating Connection
  Receiving...
  timed out
  --------------------

  Impact:
  1. Many of the sessions timeout. Any attempt to open other sessions also intermittently fail.
  This can cause serious problems to users already having a running VNC session or trying to create new sessions.

  2. The overall performance and response times of other nova services running on the novnc host, using tcp protocol
  also gets affected after the connection timeout errors.

  For example:
  Before running the sumulate thousands of connections program:
  $ time nova get-vnc-console c1b093a3-f53b-4282-b89c-e68f0fa1b6e5  novnc
  +-------+---------------------------------------------------------------------------------+
  | Type  | Url                                                                             |
  +-------+---------------------------------------------------------------------------------+
  | novnc | http://10.2.3.102:6080/vnc_auto.html?token=e776dd33-422f-4b56-9f98-e317410d0212 |
  +-------+---------------------------------------------------------------------------------+

  real    0m0.751s
  user    0m0.376s
  sys     0m0.084s

  rohit at precise-dev-102:~/tools/websocket-client-0.7.0$

  After running the program, the response time is quite high:
  $ time nova get-vnc-console c1b093a3-f53b-4282-b89c-e68f0fa1b6e5  novnc

  +-------+---------------------------------------------------------------------------------+
  | Type  | Url                                                                             |
  +-------+---------------------------------------------------------------------------------+
  | novnc | http://10.2.3.102:6080/vnc_auto.html?token=6865d675-d852-478b-b1ee-457b092f11b9 |
  +-------+---------------------------------------------------------------------------------+

  real    3m9.231s
  user    0m0.424s
  sys     0m0.108s

  
  Possible solutions:
  1. Allow just 1 session per instance, and raise a new exception, say, VNCSessionAlreadyExists to reject multiple
  connections for the same token, and return an error code to the user.
  2. Make the number of sessions allowed per instance configurable, limited by some count of sessions.

  However, both of these solutions may need to override and modify the do_proxy() method of websockify's WebSocketProxy class, 
  which can lead to maintenance issues.

  Another possible solution would be to implement some kind of callback function in websockify, to which we can pass the token
  for reconnection. This would first need contribution to the websockify project code, and then update Nova.

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