NAME¶

ssh-keysign — ssh helper program for host-based authentication

SYNOPSIS¶

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.

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

ssh-keysign is not intended to be invoked by the user, but from ssh(1). See ssh(1) and sshd(8) 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_ecdsa_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. Since they are readable only by root, ssh-keysign must be set-uid root if host-based authentication is used.

ENVIRONMENT¶

SSH_USE_STRONG_RNG

The reseeding of the OpenSSL random generator is usually done from /dev/urandom. If the SSH_USE_STRONG_RNG environment variable is set to value other than 0 the OpenSSL random generator is reseeded from /dev/random. The number of bytes read is defined by the SSH_USE_STRONG_RNG value. Minimum is 14 bytes. This setting is not recommended on the computers without the hardware random generator because insufficient entropy causes the connection to be blocked until enough entropy is available.

SEE ALSO¶

ssh(1), ssh-keygen(1), ssh_config(5), sshd(8)

HISTORY¶

ssh-keysign first appeared in OpenBSD 3.2.

AUTHORS¶

Markus Friedl ⟨markus@openbsd.org⟩