[jira] Resolved: (NET-345) Telnet client: not properly handling IAC bytes within subnegotiation messages

["Sebb (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/NET-345?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sebb resolved NET-345.
----------------------

    Resolution: Fixed

Thanks, applied patches with a few minor changes.
E.g. output is buffered, so simpler to double the IACs on the fly rather than using another buffer.

> Telnet client: not properly handling IAC bytes within subnegotiation messages
> -----------------------------------------------------------------------------
>
>                 Key: NET-345
>                 URL: https://issues.apache.org/jira/browse/NET-345
>             Project: Commons Net
>          Issue Type: Bug
>          Components: Telnet
>    Affects Versions: 2.0
>            Reporter: Archie Cobbs
>         Attachments: patch3.txt, patch4.txt
>
>
> Subnegotiation messages in telnet are sent using the sequence {{IAC SB ... IAC SE}}.
> Although it's not clearly spelled out in [RFC 854|http://tools.ietf.org/html/rfc854], any {{IAC}} ({{0xff}}) bytes inside these messages must be escaped by doubling. Other clients do this and this is the only behavior that makes sense.
> The commons-net telnet client is failing both to escape and to unescape {{IAC}} bytes within subnegotiation messages. Moreover, if it does receive a valid {{IAC IAC}} sequence within a subnegotiation message, it will incorrectly jump back to "data" input mode, discarding the message and introducing its remainder as garbage in the data stream.
> In addition, the code fails to check for an overflow of the subnegotiation buffer, which would cause an {{ArrayIndexOutOfBounds}} exception if a malicious peer triggered this condition.
> Finally, a {{IAC SE}} sequence appearing by itself should probably be discarded, rather than passing as a command to the handler.
> I'm attaching a patch to fix these issues.

-- 
This message is automatically generated by JIRA.
-
For more information on JIRA, see: http://www.atlassian.com/software/jira