SSH-KEYSIGN(1M)SSH-KEYSIGN(1M)NAMEssh-keysign - ssh helper program for host-based authentication
SYNOPSISssh-keysignDESCRIPTIONssh-keysign is used by ssh(1) to access the local host keys and gener‐
ate 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 Host‐
basedAuthentication 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 authenti‐
cation.
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.
SECURITYssh-keysign will not sign host-based authentication data under the fol‐
lowing conditions:
o If the HostbasedAuthentication client configuration parame‐
ter is not set to yes in /etc/ssh/ssh_config. This setting
cannot be overriden in users' ~/.ssh/ssh_config files.
o 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 ALSOssh(1), sshd(1M), ssh_config(4), attributes(5)AUTHORS
Markus Friedl, markus@openbsd.org
HISTORYssh-keysign first appeared in Ox 3.2.
Jun 9, 2004 SSH-KEYSIGN(1M)
