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authorColin Watson <cjwatson@debian.org>2003-09-17 01:19:29 +0000
committerColin Watson <cjwatson@debian.org>2003-09-17 01:19:29 +0000
commit9221adce6959801664fd4a340c19e6b69107ad0b (patch)
treee8b7b5706043a4eb66e0e41aad2a7986cbedeb0f /ssh-keyscan.0
parentade1cee573c0897cd08987dc14e23a555898cd12 (diff)
parent22f9b945efa61bba12a4778b889df07cf851838a (diff)
Import OpenSSH 3.7.1p1.
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1SSH-KEYSCAN(1) OpenBSD Reference Manual SSH-KEYSCAN(1)
2
3NAME
4 ssh-keyscan - gather ssh public keys
5
6SYNOPSIS
7 ssh-keyscan [-v46] [-p port] [-T timeout] [-t type] [-f file]
8 [host | addrlist namelist] [...]
9
10DESCRIPTION
11 ssh-keyscan is a utility for gathering the public ssh host keys of a num-
12 ber of hosts. It was designed to aid in building and verifying
13 ssh_known_hosts files. ssh-keyscan provides a minimal interface suitable
14 for use by shell and perl scripts.
15
16 ssh-keyscan uses non-blocking socket I/O to contact as many hosts as pos-
17 sible in parallel, so it is very efficient. The keys from a domain of
18 1,000 hosts can be collected in tens of seconds, even when some of those
19 hosts are down or do not run ssh. For scanning, one does not need login
20 access to the machines that are being scanned, nor does the scanning pro-
21 cess involve any encryption.
22
23 The options are as follows:
24
25 -p port
26 Port to connect to on the remote host.
27
28 -T timeout
29 Set the timeout for connection attempts. If timeout seconds have
30 elapsed since a connection was initiated to a host or since the
31 last time anything was read from that host, then the connection
32 is closed and the host in question considered unavailable. De-
33 fault is 5 seconds.
34
35 -t type
36 Specifies the type of the key to fetch from the scanned hosts.
37 The possible values are ``rsa1'' for protocol version 1 and
38 ``rsa'' or ``dsa'' for protocol version 2. Multiple values may
39 be specified by separating them with commas. The default is
40 ``rsa1''.
41
42 -f filename
43 Read hosts or addrlist namelist pairs from this file, one per
44 line. If - is supplied instead of a filename, ssh-keyscan will
45 read hosts or addrlist namelist pairs from the standard input.
46
47 -v Verbose mode. Causes ssh-keyscan to print debugging messages
48 about its progress.
49
50 -4 Forces ssh-keyscan to use IPv4 addresses only.
51
52 -6 Forces ssh-keyscan to use IPv6 addresses only.
53
54SECURITY
55 If a ssh_known_hosts file is constructed using ssh-keyscan without veri-
56 fying the keys, users will be vulnerable to attacks. On the other hand,
57 if the security model allows such a risk, ssh-keyscan can help in the de-
58 tection of tampered keyfiles or man in the middle attacks which have be-
59 gun after the ssh_known_hosts file was created.
60
61FILES
62 Input format:
63
64 1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4
65
66 Output format for rsa1 keys:
67
68 host-or-namelist bits exponent modulus
69
70 Output format for rsa and dsa keys:
71
72 host-or-namelist keytype base64-encoded-key
73
74 Where keytype is either ``ssh-rsa'' or ``ssh-dss''.
75
76 /etc/ssh/ssh_known_hosts
77
78EXAMPLES
79 Print the rsa1 host key for machine hostname:
80
81 $ ssh-keyscan hostname
82
83 Find all hosts from the file ssh_hosts which have new or different keys
84 from those in the sorted file ssh_known_hosts:
85
86 $ ssh-keyscan -t rsa,dsa -f ssh_hosts | \
87 sort -u - ssh_known_hosts | diff ssh_known_hosts -
88
89SEE ALSO
90 ssh(1), sshd(8)
91
92AUTHORS
93 David Mazieres <dm@lcs.mit.edu> wrote the initial version, and
94 Wayne Davison <wayned@users.sourceforge.net> added support for protocol
95 version 2.
96
97BUGS
98 It generates "Connection closed by remote host" messages on the consoles
99 of all the machines it scans if the server is older than version 2.9.
100 This is because it opens a connection to the ssh port, reads the public
101 key, and drops the connection as soon as it gets the key.
102
103OpenBSD 3.4 January 1, 1996 2