Annotation of src/usr.bin/ssh/ssh-keyscan.1, Revision 1.35
1.35 ! naddy 1: .\" $OpenBSD: ssh-keyscan.1,v 1.34 2014/01/28 14:13:39 jmc Exp $
1.4 deraadt 2: .\"
3: .\" Copyright 1995, 1996 by David Mazieres <dm@lcs.mit.edu>.
4: .\"
5: .\" Modification and redistribution in source and binary forms is
6: .\" permitted provided that due credit is given to the author and the
1.6 pvalchev 7: .\" OpenBSD project by leaving this copyright notice intact.
1.3 niklas 8: .\"
1.35 ! naddy 9: .Dd $Mdocdate: January 28 2014 $
1.4 deraadt 10: .Dt SSH-KEYSCAN 1
1.1 markus 11: .Os
12: .Sh NAME
13: .Nm ssh-keyscan
14: .Nd gather ssh public keys
15: .Sh SYNOPSIS
16: .Nm ssh-keyscan
1.15 jmc 17: .Bk -words
1.20 jmc 18: .Op Fl 46Hv
19: .Op Fl f Ar file
1.10 markus 20: .Op Fl p Ar port
21: .Op Fl T Ar timeout
22: .Op Fl t Ar type
23: .Op Ar host | addrlist namelist
1.25 sobrado 24: .Ar ...
1.15 jmc 25: .Ek
1.1 markus 26: .Sh DESCRIPTION
27: .Nm
28: is a utility for gathering the public ssh host keys of a number of
1.15 jmc 29: hosts.
30: It was designed to aid in building and verifying
1.1 markus 31: .Pa ssh_known_hosts
32: files.
33: .Nm
34: provides a minimal interface suitable for use by shell and perl
35: scripts.
36: .Pp
37: .Nm
38: uses non-blocking socket I/O to contact as many hosts as possible in
1.15 jmc 39: parallel, so it is very efficient.
40: The keys from a domain of 1,000
1.1 markus 41: hosts can be collected in tens of seconds, even when some of those
1.15 jmc 42: hosts are down or do not run ssh.
43: For scanning, one does not need
1.12 deraadt 44: login access to the machines that are being scanned, nor does the
45: scanning process involve any encryption.
1.9 mpech 46: .Pp
47: The options are as follows:
1.1 markus 48: .Bl -tag -width Ds
1.20 jmc 49: .It Fl 4
50: Forces
51: .Nm
52: to use IPv4 addresses only.
53: .It Fl 6
54: Forces
55: .Nm
56: to use IPv6 addresses only.
57: .It Fl f Ar file
58: Read hosts or
1.34 jmc 59: .Dq addrlist namelist
60: pairs from
61: .Ar file ,
62: one per line.
1.20 jmc 63: If
64: .Pa -
65: is supplied instead of a filename,
66: .Nm
67: will read hosts or
1.34 jmc 68: .Dq addrlist namelist
1.20 jmc 69: pairs from the standard input.
1.19 djm 70: .It Fl H
71: Hash all hostnames and addresses in the output.
72: Hashed names may be used normally by
73: .Nm ssh
74: and
75: .Nm sshd ,
76: but they do not reveal identifying information should the file's contents
77: be disclosed.
1.10 markus 78: .It Fl p Ar port
79: Port to connect to on the remote host.
1.11 stevesk 80: .It Fl T Ar timeout
1.15 jmc 81: Set the timeout for connection attempts.
82: If
1.34 jmc 83: .Ar timeout
1.1 markus 84: seconds have elapsed since a connection was initiated to a host or since the
85: last time anything was read from that host, then the connection is
1.15 jmc 86: closed and the host in question considered unavailable.
87: Default is 5 seconds.
1.10 markus 88: .It Fl t Ar type
1.11 stevesk 89: Specifies the type of the key to fetch from the scanned hosts.
1.10 markus 90: The possible values are
91: .Dq rsa1
92: for protocol version 1 and
1.29 djm 93: .Dq dsa ,
1.33 naddy 94: .Dq ecdsa ,
95: .Dq ed25519 ,
1.29 djm 96: or
1.10 markus 97: .Dq rsa
98: for protocol version 2.
99: Multiple values may be specified by separating them with commas.
1.30 djm 100: The default is to fetch
1.35 ! naddy 101: .Dq rsa ,
! 102: .Dq ecdsa ,
1.30 djm 103: and
1.35 ! naddy 104: .Dq ed25519
1.30 djm 105: keys.
1.10 markus 106: .It Fl v
107: Verbose mode.
108: Causes
109: .Nm
110: to print debugging messages about its progress.
1.2 itojun 111: .El
1.9 mpech 112: .Sh SECURITY
1.22 ray 113: If an ssh_known_hosts file is constructed using
1.9 mpech 114: .Nm
1.12 deraadt 115: without verifying the keys, users will be vulnerable to
1.18 brad 116: .Em man in the middle
1.9 mpech 117: attacks.
1.12 deraadt 118: On the other hand, if the security model allows such a risk,
1.9 mpech 119: .Nm
1.12 deraadt 120: can help in the detection of tampered keyfiles or man in the middle
121: attacks which have begun after the ssh_known_hosts file was created.
1.1 markus 122: .Sh FILES
1.34 jmc 123: Input format:
1.10 markus 124: .Bd -literal
1.1 markus 125: 1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4
1.10 markus 126: .Ed
1.1 markus 127: .Pp
1.35 ! naddy 128: Output format for RSA1 keys:
1.10 markus 129: .Bd -literal
1.1 markus 130: host-or-namelist bits exponent modulus
1.10 markus 131: .Ed
132: .Pp
1.35 ! naddy 133: Output format for RSA, DSA, ECDSA, and ED25519 keys:
1.10 markus 134: .Bd -literal
135: host-or-namelist keytype base64-encoded-key
136: .Ed
137: .Pp
138: Where
1.34 jmc 139: .Ar keytype
1.10 markus 140: is either
1.29 djm 141: .Dq ecdsa-sha2-nistp256 ,
142: .Dq ecdsa-sha2-nistp384 ,
143: .Dq ecdsa-sha2-nistp521 ,
1.32 markus 144: .Dq ssh-ed25519 ,
1.29 djm 145: .Dq ssh-dss
1.10 markus 146: or
1.29 djm 147: .Dq ssh-rsa .
1.1 markus 148: .Pp
1.13 deraadt 149: .Pa /etc/ssh/ssh_known_hosts
1.17 jmc 150: .Sh EXAMPLES
1.34 jmc 151: Print the rsa host key for machine
152: .Ar hostname :
1.17 jmc 153: .Bd -literal
154: $ ssh-keyscan hostname
155: .Ed
156: .Pp
157: Find all hosts from the file
158: .Pa ssh_hosts
159: which have new or different keys from those in the sorted file
160: .Pa ssh_known_hosts :
161: .Bd -literal
1.35 ! naddy 162: $ ssh-keyscan -t rsa,dsa,ecdsa,ed25519 -f ssh_hosts | \e
1.17 jmc 163: sort -u - ssh_known_hosts | diff ssh_known_hosts -
164: .Ed
1.1 markus 165: .Sh SEE ALSO
1.4 deraadt 166: .Xr ssh 1 ,
1.1 markus 167: .Xr sshd 8
1.7 mpech 168: .Sh AUTHORS
1.21 jaredy 169: .An -nosplit
1.31 schwarze 170: .An David Mazieres Aq Mt dm@lcs.mit.edu
1.10 markus 171: wrote the initial version, and
1.31 schwarze 172: .An Wayne Davison Aq Mt wayned@users.sourceforge.net
1.10 markus 173: added support for protocol version 2.
1.17 jmc 174: .Sh BUGS
175: It generates "Connection closed by remote host" messages on the consoles
176: of all the machines it scans if the server is older than version 2.9.
177: This is because it opens a connection to the ssh port, reads the public
178: key, and drops the connection as soon as it gets the key.
![[BACK]](/icons/back.gif){kind=icon}
Return to ssh-keyscan.1 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh