man/man1m/ssh-keysign.sunssh.1m

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 SSH-KEYSIGN 1M "Jun 9, 2004"
 NAME
ssh-keysign - ssh helper program for host-based authentication
 SYNOPSIS

ssh-keysign


 DESCRIPTION

ssh-keysign is used by ssh(1) to access the local host keys and
generate the digital signature required during host-based authentication with
SSH protocol version 2. This signature is of data that includes, among other
items, the name of the client host and the name of the client user.

ssh-keysign is disabled by default and can be enabled only in the global
client configuration file /etc/ssh/ssh_config by setting
HostbasedAuthentication to yes.

ssh-keysign is not intended to be invoked by the user, but from
ssh. See ssh(1) and sshd(1M) for more information about
host-based authentication.
 FILES
/etc/ssh/ssh_config

Controls whether ssh-keysign is enabled.


/etc/ssh/ssh_host_dsa_key

/etc/ssh/ssh_host_rsa_key

These files contain the private parts of the host keys used to generate the
digital signature. They should be owned by root, readable only by root, and not
accessible to others. Because they are readable only by root, ssh-keysign
must be set-uid root if host-based authentication is used.


 SECURITY

ssh-keysign will not sign host-based authentication data under the following
conditions:


If the HostbasedAuthentication client configuration parameter is not set
to yes in /etc/ssh/ssh_config. This setting cannot be overriden in
users' ~/.ssh/ssh_config files.


If the client hostname and username in /etc/ssh/ssh_config do not match
the canonical hostname of the client where ssh-keysign is invoked and the
name of the user invoking ssh-keysign.


In spite of ssh-keysign's restrictions on the contents of the host-based
authentication data, there remains the ability of users to use it as an avenue
for obtaining the client's private host keys. For this reason host-based
authentication is turned off by default.
 ATTRIBUTES

See attributes(5) for descriptions of the following attributes:


ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Evolving


 SEE ALSO

ssh(1), sshd(1M), ssh_config(4), attributes(5)
 AUTHORS

Markus Friedl, markus@openbsd.org
 HISTORY

ssh-keysign first appeared in Ox 3.2.