The requested release binding is patch.  

The ssh_config(4) file is Evolving, this case is about a set of
changes that may help bring it up to Stable.  This case does not assert that
ssh_config(4) become Stable at this time.  The taxonomy of the new options
is Evolving.

ABSTRACT
--------

This case concerns ssh(1)'s behaviour in the face of unknown
configuration options.

It's been recently discovered that the current behaviour (exit with an
error message) makes per-user ssh configuration files (see ssh(1) and
ssh_config(4)) not extensible in compatible ways.

This behaviour is inherited from OpenSSH and exists ostensibly to
prevent mis-spelling and other errors from causing security problems.

This behaviour affects compatibility between SUNWssh versions as well as
between all versions and derivatives of OpenSSH which share the per-user
configuration file path "~/.ssh/config" and a solution is badly needed.

PROPOSAL
--------

We note that the OpenSSH team feels free to add new ssh_config(4)
parameters at any time, thus refraining from adding parameters to
ssh_config(4) is not an option.  Silently ignoring unknown parameters is
not an option either since this can cause users to assume that ssh(1)
understood a given parameter when it didn't.  Neither is prompting about
unknown parameters appealing.

Therefore we propose to make ssh(1) support a mechanism by which to
inform it of parameters known to other versions of ssh(1) which can then
be safely ignored by it:

 - Add a new ssh_config(4) ssh configuration parameter called
   'IgnoreIfUnknown' whose value(s) is(are) comma-separated lists of
   configuration parameter names.

   Man page text:

     IgnoreIfUnknown
	   Specifies a comma-separated list of ssh_config(4)
	   parameters which, if unknown to ssh(1) are to be
	   ignored by ssh(1).  Multiple values for this parameter
	   may be given; ssh(1) will honor the combined lists.

	   This parameter is primarily intended to be used in the
	   system-wide ssh_config(4), though it may also be used
	   in the per-user ssh_config(4) (~/.ssh/config) files.

 - Add a new ssh_config(4) ssh configuration parameter called
   'DontIgnoreIfUnknown' whose value(s) is(are) comma-separated lists of
   configuration parameter names which must not be ignored by ssh(1)'s
   which do not understand them.  This parameter overrides
   'IgnoreIfUnknown'.

   Man page text:

     DontIgnoreIfUnknown
           Specifies a comma-separated list of ssh_config(4)
	   parameters which must not be ignored by ssh(1) if it
	   does not support them.  Multiple values for this
	   parameter may be given; ssh(1) will honor the combined
	   lists.

	   This parameter is primarily intended to be used in the
	   per-user ssh_config(4) (~/.ssh/config) files.


 - Whenever new ssh_config(4) configuration parameters are added in
   micro/patch releases the release notes will document the need to
   update /etc/ssh/ssh_config on older systems to add the new parameters
   to the IgnoreIfUnknown lists.

 - Whenever new ssh_config(4) configuration parameters are added a patch
   should be considered for previous minor releases to update
   IgnoreIfUnknown in /etc/ssh/ssh_config.

 - Support for IgnoreIfUnknown should be backported to SUNWssh 1.0.x
   (Solaris 9's ssh).

 - Sun will contribute patches to OpenSSH for this new option.

   The OpenSSH team doesn't seem to want to commit to any solution;
   typically they don't like to commit to adding support for any user
   requested features unless patches are included.


REFERENCES
----------

http://bugzilla.mindrot.org/show_bug.cgi?id=866