Re: Additional AD Comment: draft-ietf-secsh-publickey-subsystem and garbage

[Sam Hartman <hartmans-ietf%mit.edu@localhost>]

>>>>> "Nicolas" == Nicolas Williams <Nicolas.Williams%sun.com@localhost> writes:

    Nicolas> On Thu, Aug 31, 2006 at 08:52:03AM -0400, Sam Hartman
    Nicolas> wrote:
    >> I'd like to draw your attention to a particularly annoying part
    >> of RFC 4254:
    >> 
    >> This last form executes a predefined subsystem.  It is expected
    >> that these will include a general file transfer mechanism, and
    >> possibly other features.  Implementations may also allow
    >> configuring more such mechanisms.  As the user's shell is
    >> usually used to execute the subsystem, it is advisable for the
    >> subsystem protocol to have a "magic cookie" at the beginning of
    >> the protocol transaction to distinguish it from arbitrary
    >> output generated by shell initialization scripts, etc.  This
    >> spurious output from the shell may be filtered out either at
    >> the server or at the client.
    >> 
    >> 
    >> In order to guarantee interoperability, your subsystem needs to
    >> be able to filter out leading garbage and clients MUST do so.

    Nicolas> The text you quote says "advisable" and "may."

Yes.  The server MAY spew random garbage.  So, the client MUST deal
with it.