108 lines
4.0 KiB
Plaintext
108 lines
4.0 KiB
Plaintext
SSH-KEYSCAN(1) OpenBSD Reference Manual SSH-KEYSCAN(1)
|
|
|
|
NAME
|
|
ssh-keyscan - gather ssh public keys
|
|
|
|
SYNOPSIS
|
|
ssh-keyscan [-46Hv] [-f file] [-p port] [-T timeout] [-t type]
|
|
[host | addrlist namelist] ...
|
|
|
|
DESCRIPTION
|
|
ssh-keyscan is a utility for gathering the public ssh host keys of a num-
|
|
ber of hosts. It was designed to aid in building and verifying
|
|
ssh_known_hosts files. ssh-keyscan provides a minimal interface suitable
|
|
for use by shell and perl scripts.
|
|
|
|
ssh-keyscan uses non-blocking socket I/O to contact as many hosts as pos-
|
|
sible 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 ssh. For scanning, one does not need login
|
|
access to the machines that are being scanned, nor does the scanning pro-
|
|
cess involve any encryption.
|
|
|
|
The options are as follows:
|
|
|
|
-4 Forces ssh-keyscan to use IPv4 addresses only.
|
|
|
|
-6 Forces ssh-keyscan to use IPv6 addresses only.
|
|
|
|
-f file
|
|
Read hosts or addrlist namelist pairs from this file, one per
|
|
line. If - is supplied instead of a filename, ssh-keyscan will
|
|
read hosts or addrlist namelist pairs from the standard input.
|
|
|
|
-H Hash all hostnames and addresses in the output. Hashed names may
|
|
be used normally by ssh and sshd, but they do not reveal identi-
|
|
fying information should the file's contents be disclosed.
|
|
|
|
-p port
|
|
Port to connect to on the remote host.
|
|
|
|
-T timeout
|
|
Set the timeout for connection attempts. If timeout seconds have
|
|
elapsed since a connection was initiated to a host or since the
|
|
last time anything was read from that host, then the connection
|
|
is closed and the host in question considered unavailable. De-
|
|
fault is 5 seconds.
|
|
|
|
-t type
|
|
Specifies the type of the key to fetch from the scanned hosts.
|
|
The possible values are ``rsa1'' for protocol version 1 and
|
|
``rsa'' or ``dsa'' for protocol version 2. Multiple values may
|
|
be specified by separating them with commas. The default is
|
|
``rsa''.
|
|
|
|
-v Verbose mode. Causes ssh-keyscan to print debugging messages
|
|
about its progress.
|
|
|
|
SECURITY
|
|
If an ssh_known_hosts file is constructed using ssh-keyscan without veri-
|
|
fying 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-keyscan
|
|
can help in the detection of tampered keyfiles or man in the middle at-
|
|
tacks which have begun after the ssh_known_hosts file was created.
|
|
|
|
FILES
|
|
Input format:
|
|
|
|
1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4
|
|
|
|
Output format for rsa1 keys:
|
|
|
|
host-or-namelist bits exponent modulus
|
|
|
|
Output format for rsa and dsa keys:
|
|
|
|
host-or-namelist keytype base64-encoded-key
|
|
|
|
Where keytype is either ``ssh-rsa'' or ``ssh-dss''.
|
|
|
|
/etc/ssh/ssh_known_hosts
|
|
|
|
EXAMPLES
|
|
Print the rsa host key for machine hostname:
|
|
|
|
$ ssh-keyscan hostname
|
|
|
|
Find all hosts from the file ssh_hosts which have new or different keys
|
|
from those in the sorted file ssh_known_hosts:
|
|
|
|
$ ssh-keyscan -t rsa,dsa -f ssh_hosts | \
|
|
sort -u - ssh_known_hosts | diff ssh_known_hosts -
|
|
|
|
SEE ALSO
|
|
ssh(1), sshd(8)
|
|
|
|
AUTHORS
|
|
David Mazieres <dm@lcs.mit.edu> wrote the initial version, and Wayne
|
|
Davison <wayned@users.sourceforge.net> added support for protocol version
|
|
2.
|
|
|
|
BUGS
|
|
It generates "Connection closed by remote host" messages on the consoles
|
|
of all the machines it scans if the server is older than version 2.9.
|
|
This is because it opens a connection to the ssh port, reads the public
|
|
key, and drops the connection as soon as it gets the key.
|
|
|
|
OpenBSD 4.7 January 9, 2010 2
|