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---- __NAME__ ssh-keyscan - gather ssh public keys __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 build- ing and verifying ssh_known_hosts files. ssh-keyscan pro- vides 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 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. The options are as follows: -p port Port to connect to on the remote host.-T timeoutSet 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. Default 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 proto- col version 2. Multiple values may be specified by separating them with commas. The default is ``rsa1''. -f filename Read hosts or addrlist namelist pairs from this file, one per line. If - is supplied instead of a file- name, ssh-keyscan will read hosts or addrlist namelist pairs from the standard input. -v Verbose mode. Causes ssh-keyscan to print debugging messages about its progress. -4 Forces ssh-keyscan to use IPv4 addresses only. -6 Forces ssh-keyscan to use IPv6 addresses only. __SECURITY__ If a ssh_known_hosts file is constructed using ssh-keyscan without verifying the keys, users will be vulnerable to attacks. On the other hand, if the security model allows such a risk, ssh-keyscan can help in the detection of tam- pered keyfiles or man in the middle attacks which have begun after the ssh_known_hosts file was created. __EXAMPLES__ Print the rsa1 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 - __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-dsa''. /etc/ssh/ssh_known_hosts __BUGS__ It generates __SEE ALSO__ ssh(1), sshd(8) __AUTHORS__ David Mazieres BSD January 1, 1996 1 ----
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