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author | Colin Watson <cjwatson@debian.org> | 2010-03-31 00:43:52 +0100 |
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committer | Colin Watson <cjwatson@debian.org> | 2010-03-31 00:43:52 +0100 |
commit | 004a7fb9c6a00b13dc98f56599918a54a3506d10 (patch) | |
tree | c8cb70b404e798f78982f06cd892ab82ecb1e03e /ssh-keyscan.0 | |
parent | d13d995a202c562c80d7e7a11c43504c505481d1 (diff) | |
parent | 1e4cfeee6c17b02af09418c5afe4a4d71aaaf0c8 (diff) |
Import 5.4p1 tarball
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1 | SSH-KEYSCAN(1) OpenBSD Reference Manual SSH-KEYSCAN(1) | ||
2 | |||
3 | NAME | ||
4 | ssh-keyscan - gather ssh public keys | ||
5 | |||
6 | SYNOPSIS | ||
7 | ssh-keyscan [-46Hv] [-f file] [-p port] [-T timeout] [-t type] | ||
8 | [host | addrlist namelist] ... | ||
9 | |||
10 | DESCRIPTION | ||
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 | -4 Forces ssh-keyscan to use IPv4 addresses only. | ||
26 | |||
27 | -6 Forces ssh-keyscan to use IPv6 addresses only. | ||
28 | |||
29 | -f file | ||
30 | Read hosts or addrlist namelist pairs from this file, one per | ||
31 | line. If - is supplied instead of a filename, ssh-keyscan will | ||
32 | read hosts or addrlist namelist pairs from the standard input. | ||
33 | |||
34 | -H Hash all hostnames and addresses in the output. Hashed names may | ||
35 | be used normally by ssh and sshd, but they do not reveal identi- | ||
36 | fying information should the file's contents be disclosed. | ||
37 | |||
38 | -p port | ||
39 | Port to connect to on the remote host. | ||
40 | |||
41 | -T timeout | ||
42 | Set the timeout for connection attempts. If timeout seconds have | ||
43 | elapsed since a connection was initiated to a host or since the | ||
44 | last time anything was read from that host, then the connection | ||
45 | is closed and the host in question considered unavailable. De- | ||
46 | fault is 5 seconds. | ||
47 | |||
48 | -t type | ||
49 | Specifies the type of the key to fetch from the scanned hosts. | ||
50 | The possible values are ``rsa1'' for protocol version 1 and | ||
51 | ``rsa'' or ``dsa'' for protocol version 2. Multiple values may | ||
52 | be specified by separating them with commas. The default is | ||
53 | ``rsa''. | ||
54 | |||
55 | -v Verbose mode. Causes ssh-keyscan to print debugging messages | ||
56 | about its progress. | ||
57 | |||
58 | SECURITY | ||
59 | If an ssh_known_hosts file is constructed using ssh-keyscan without veri- | ||
60 | fying the keys, users will be vulnerable to man in the middle attacks. | ||
61 | On the other hand, if the security model allows such a risk, ssh-keyscan | ||
62 | can help in the detection of tampered keyfiles or man in the middle at- | ||
63 | tacks which have begun after the ssh_known_hosts file was created. | ||
64 | |||
65 | FILES | ||
66 | Input format: | ||
67 | |||
68 | 1.2.3.4,1.2.4.4 name.my.domain,name,n.my.domain,n,1.2.3.4,1.2.4.4 | ||
69 | |||
70 | Output format for rsa1 keys: | ||
71 | |||
72 | host-or-namelist bits exponent modulus | ||
73 | |||
74 | Output format for rsa and dsa keys: | ||
75 | |||
76 | host-or-namelist keytype base64-encoded-key | ||
77 | |||
78 | Where keytype is either ``ssh-rsa'' or ``ssh-dss''. | ||
79 | |||
80 | /etc/ssh/ssh_known_hosts | ||
81 | |||
82 | EXAMPLES | ||
83 | Print the rsa host key for machine hostname: | ||
84 | |||
85 | $ ssh-keyscan hostname | ||
86 | |||
87 | Find all hosts from the file ssh_hosts which have new or different keys | ||
88 | from those in the sorted file ssh_known_hosts: | ||
89 | |||
90 | $ ssh-keyscan -t rsa,dsa -f ssh_hosts | \ | ||
91 | sort -u - ssh_known_hosts | diff ssh_known_hosts - | ||
92 | |||
93 | SEE ALSO | ||
94 | ssh(1), sshd(8) | ||
95 | |||
96 | AUTHORS | ||
97 | David Mazieres <dm@lcs.mit.edu> wrote the initial version, and Wayne | ||
98 | Davison <wayned@users.sourceforge.net> added support for protocol version | ||
99 | 2. | ||
100 | |||
101 | BUGS | ||
102 | It generates "Connection closed by remote host" messages on the consoles | ||
103 | of all the machines it scans if the server is older than version 2.9. | ||
104 | This is because it opens a connection to the ssh port, reads the public | ||
105 | key, and drops the connection as soon as it gets the key. | ||
106 | |||
107 | OpenBSD 4.6 January 9, 2010 2 | ||