ssh-keyscan(1)							   User Commands						    ssh-keyscan(1)

NAME

       ssh-keyscan - gather public ssh host keys of a number of hosts

SYNOPSIS

       ssh-keyscan [-v46] [-p port] [-T timeout] [-t type] [-f file] [-] [host... | addrlist namelist]	[...]

DESCRIPTION

       ssh-keyscan  is	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. ssh-keyscan provides a minimal interface suitable for use by shell and perl scripts.  The output of  ssh-keyscan	is
       directed to standard output.

       ssh-keyscan  uses 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 ssh. For scanning,  one  does  not
       need login access to the machines that are being scanned, nor does the scanning process involve any encryption.

   File Format
       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, where keytype is either ssh-rsa or `ssh-dsa:

       host-or-namelist keytype base64-encoded-key

OPTIONS

       The following options are supported:

       -f filename	       Read  hosts  or	addrlist namelist pairs from this file, one per line. If you specity - instead of a filename, ssh-
			       keyscan reads hosts or addrlist namelist pairs from the standard input.

       -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, the connection is closed and the host in question is con-
			       sidered unavailable. The default is for timeout is 5 seconds.

       -t type		       Specify the type of the key to fetch from the scanned hosts. The possible values for type  are  rsa1  for  protocol
			       version	1  and	rsa  or  dsa  for  protocol version 2. Specify multiple values by separating them with commas. The
			       default is rsa1.

       -v		       Specify verbose mode. Print debugging messages about progress.

       -4		       Force to use IPv4 addresses only.

       -6		       Forces to use IPv6 addresses only.

SECURITY

       If a ssh_known_hosts file is constructed using ssh-keyscan without verifying the keys, users are vulnerable to  man-in-the-middle  attacks.
       If  the	security  model  allows such a risk, ssh-keyscan can help in the detection of tampered keyfiles or man-in-the-middle attacks which
       have begun after the ssh_known_hosts file was created.

EXAMPLES

       Example 1: Printing the rsa1 Host Key

       The following example prints the rsa1 host key for machine hostname:

       $ ssh-keyscan hostname

       Example 2: Finding All Hosts

       The following commands finds 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 -

FILES

       /etc/ssh_known_hosts

EXIT STATUS

       The following exit values are returned:

       0	No usage errors. ssh-keyscan might or might not have succeeded or failed to scan one, more or all of the given hosts.

       1	Usage error.

ATTRIBUTES

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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWsshu			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       ssh(1), sshd(1M), attributes(5)

AUTHORS

       David Mazieres wrote the initial version, and Wayne Davison added suppport for protocol version 2.

BUGS

       ssh--keyscan generates

       Connection closed by remote host
       messages  on  the consoles of all machines it scans if the server is older than version 2.9. This is because ssh-keyscan opens a connection
       to the ssh port, reads the public key, and drops the connection as soon as it gets the key.

SunOS 5.10							    24 Jul 2004 						    ssh-keyscan(1)