SSHM-bM-^@M-^PKEYSCAN(1)            BSD General Commands Manual           SSHM-bM-^@M-^PKEYSCAN(1)

^[[1mNAME^[[0m
     ^[[1msshM-bM-^@M-^Pkeyscan ^[[22mM-bMM-^R gather ssh public keys

^[[1mSYNOPSIS^[[0m
     ^[[1msshM-bM-^@M-^Pkeyscan ^[[22m[^[[1mM-bMM-^Rv46^[[22m] [^[[1mM-bMM-^Rp ^[[4m^[[22mport^[[24m] [^[[1mM-bMM-^RT ^[[4m^[[22mtimeout^[[24m] [^[[1mM-bMM-^Rt ^[[4m^[[22mtype^[[24m] [^[[1mM-bMM-^Rf ^[[4m^[[22mfile^[[24m]
                 [^[[4mhost^[[24m | ^[[4maddrlist^[[24m ^[[4mnamelist^[[24m] [^[[4m...^[[24m]

^[[1mDESCRIPTION^[[0m
     ^[[1msshM-bM-^@M-^Pkeyscan ^[[22mis a utility for gathering the public ssh host keys of a numM-bM-^@M-^P
     ber of hosts.  It was designed to aid in building and verifying
     ^[[4mssh_known_hosts^[[24m files.  ^[[1msshM-bM-^@M-^Pkeyscan ^[[22mprovides a minimal interface suitable
     for use by shell and perl scripts.

     ^[[1msshM-bM-^@M-^Pkeyscan ^[[22muses nonM-bM-^@M-^Pblocking socket I/O to contact as many hosts as posM-bM-^@M-^P
     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 proM-bM-^@M-^P
     cess involve any encryption.

     The options are as follows:

     ^[[1mM-bMM-^Rp ^[[4m^[[22mport^[[0m
             Port to connect to on the remote host.

     ^[[1mM-bMM-^RT ^[[4m^[[22mtimeout^[[0m
             Set the timeout for connection attempts.  If ^[[4mtimeout^[[24m 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.

     ^[[1mM-bMM-^Rt ^[[4m^[[22mtype^[[0m
             Specifies the type of the key to fetch from the scanned hosts.
             The possible values are M-bM-^@M-^\rsa1M-bM-^@M-^] for protocol version 1 and M-bM-^@M-^\rsaM-bM-^@M-^]
             or M-bM-^@M-^\dsaM-bM-^@M-^] for protocol version 2.  Multiple values may be speciM-bM-^@M-^P
             fied by separating them with commas.  The default is M-bM-^@M-^\rsa1M-bM-^@M-^].

     ^[[1mM-bMM-^Rf ^[[4m^[[22mfilename^[[0m
             Read hosts or ^[[4maddrlist^[[24m ^[[4mnamelist^[[24m pairs from this file, one per
             line.  If ^[[4mM-bM-^@M-^P^[[24m is supplied instead of a filename, ^[[1msshM-bM-^@M-^Pkeyscan ^[[22mwill
             read hosts or ^[[4maddrlist^[[24m ^[[4mnamelist^[[24m pairs from the standard input.

     ^[[1mM-bMM-^Rv      ^[[22mVerbose mode.  Causes ^[[1msshM-bM-^@M-^Pkeyscan ^[[22mto print debugging messages
             about its progress.

     ^[[1mM-bMM-^R4      ^[[22mForces ^[[1msshM-bM-^@M-^Pkeyscan ^[[22mto use IPv4 addresses only.

     ^[[1mM-bMM-^R6      ^[[22mForces ^[[1msshM-bM-^@M-^Pkeyscan ^[[22mto use IPv6 addresses only.

^[[1mSECURITY^[[0m
     If a ssh_known_hosts file is constructed using ^[[1msshM-bM-^@M-^Pkeyscan ^[[22mwithout veriM-bM-^@M-^P
     fying the keys, users will be vulnerable to attacks.  On the other hand,
     if the security model allows such a risk, ^[[1msshM-bM-^@M-^Pkeyscan ^[[22mcan help in the
     detection of tampered keyfiles or man in the middle attacks which have
     begun after the ssh_known_hosts file was created.

^[[1mEXAMPLES^[[0m
     Print the ^[[4mrsa1^[[24m host key for machine ^[[4mhostname^[[24m:

     $ sshM-bM-^@M-^Pkeyscan hostname

     Find all hosts from the file ^[[4mssh_hosts^[[24m which have new or different keys
     from those in the sorted file ^[[4mssh_known_hosts^[[24m:

     $ sshM-bM-^@M-^Pkeyscan M-bM-^@M-^Pt rsa,dsa M-bM-^@M-^Pf ssh_hosts | \
             sort M-bM-^@M-^Pu M-bM-^@M-^P ssh_known_hosts | diff ssh_known_hosts M-bM-^@M-^P

^[[1mFILES^[[0m
     ^[[4mInput^[[24m ^[[4mformat:^[[0m

     1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4

     ^[[4mOutput^[[24m ^[[4mformat^[[24m ^[[4mfor^[[24m ^[[4mrsa1^[[24m ^[[4mkeys:^[[0m

     hostM-bM-^@M-^PorM-bM-^@M-^Pnamelist bits exponent modulus

     ^[[4mOutput^[[24m ^[[4mformat^[[24m ^[[4mfor^[[24m ^[[4mrsa^[[24m ^[[4mand^[[24m ^[[4mdsa^[[24m ^[[4mkeys:^[[0m

     hostM-bM-^@M-^PorM-bM-^@M-^Pnamelist keytype base64M-bM-^@M-^PencodedM-bM-^@M-^Pkey

     Where ^[[4mkeytype^[[24m is either M-bM-^@M-^\sshM-bM-^@M-^PrsaM-bM-^@M-^] or M-bM-^@M-^\sshM-bM-^@M-^PdsaM-bM-^@M-^].

     ^[[4m/etc/ssh/ssh_known_hosts^[[0m

^[[1mBUGS^[[0m
     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.

^[[1mSEE ALSO^[[0m
     ssh(1), sshd(8)

^[[1mAUTHORS^[[0m
     David Mazieres <dm@lcs.mit.edu> wrote the initial version, and Wayne
     Davison <wayned@users.sourceforge.net> added support for protocol version
     2.

BSD                             January 1, 1996                            BSD