[GUACAMOLE-587] RDP connections fail due to Guacamole protocol violation

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 1.0.0
• Fix Version/s: 1.0.0
• Component/s: libguac
• Assignee: Nick Couchman
• Reporter: Marc
• Created: 05/Jul/18 14:29
• Updated: 09/Jul/18 04:56
• Resolved: 05/Jul/18 21:49

Description

The implementation of the Guacamole protocol within libguac enforces a limit on the number of elements a instruction may contain to ensure instruction space cannot be exhausted without bound by a malicious client. This limit is currently set at 64:

/**
 * The maximum number of elements per instruction, including the opcode.
 */
#define GUAC_INSTRUCTION_MAX_ELEMENTS 64

As GUACAMOLE-445 added a 64th parameter to RDP, this means the client cannot send its connect response to the initial args instruction during the Guacamole protocol handshake without exceeding this limit, and connections cannot be established:

...
guacd[7]: ERROR:        Guacamole protocol violation. Perhaps the version of guacamole-client is incompatible with this version of libguac?
guacd[7]: DEBUG:        Error reading "connect": Instruction parse error
...

Issue Links

• relates to: GUACAMOLE-445 Allow RDP printer name to be configured
• links to: https://github.com/apache/guacamole-server/pull/175