|SSH-KEYSCAN(1)||General Commands Manual||SSH-KEYSCAN(1)|
host | addrlist namelist]
ssh-keyscanis a utility for gathering the public SSH host keys of a number of hosts. It was designed to aid in building and verifying ssh_known_hosts files, the format of which is documented in sshd(8).
ssh-keyscanprovides a minimal interface suitable for use by shell and perl scripts.
ssh-keyscanuses non-blocking socket I/O to contact as many hosts as possible in parallel, so it is very efficient. The keys from a domain of 1,000 hosts can be collected in tens of seconds, even when some of those hosts are down or do not run sshd(8). For scanning, one does not need login access to the machines that are being scanned, nor does the scanning process involve any encryption. The options are as follows:
ssh-keyscanto use IPv4 addresses only.
ssh-keyscanto use IPv6 addresses only.
ssh-keyscanwill read from the standard input. Input is expected in the format:
ssh-keyscanwithout verifying the keys, users will be vulnerable to man in the middle attacks. On the other hand, if the security model allows such a risk,
ssh-keyscancan help in the detection of tampered keyfiles or man in the middle attacks which have begun after the ssh_known_hosts file was created. /etc/ssh/ssh_known_hosts
$ ssh-keyscan -t rsa hostname
$ ssh-keyscan -t rsa,dsa,ecdsa,ed25519 -f ssh_hosts | \ sort -u - ssh_known_hosts | diff ssh_known_hosts -
|March 5, 2018||OpenBSD-current|