Anderson Toshiyuki Sasaki f18a7cc17e kex: Do not ignore keys in known_hosts files ...

Previously, if the SSH_OPTIONS_HOSTKEYS option was set by any mean,
including the client configuration file, the keys in known_hosts files
wouldn't be considered before advertising the list of wanted host keys.

This could result in the client requesting the server to provide a
signature using a key not present in the known_hosts files (e.g. when
the first wanted algorithm in SSH_OPTIONS_HOSTKEYS is not present in the
known_hosts files), causing a host key mismatch and possible key
rejection.

Now, the keys present in the known_hosts files are prioritized over the
other wanted keys.  This do not change the fact that only keys of types
present in the list set in SSH_OPTIONS_HOSTKEYS will be accepted and
prioritized following the order defined by such list.

The new wanted list of hostkeys is given by:
 - The keys present in known_hosts files, ordered by preference defined
   in SSH_OPTIONS_HOSTKEYS.  If the option is not set, a default order
   of preference is used.
 - The other keys present in the same option are appended without adding
   duplicates.  If the option is not set, the default list of keys is
   used.

Fixes: T156

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

2019-07-04 10:29:20 +02:00

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