diff options
Diffstat (limited to 'ssh-keyscan.0')
-rw-r--r-- | ssh-keyscan.0 | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/ssh-keyscan.0 b/ssh-keyscan.0 new file mode 100644 index 000000000000..f655abd47465 --- /dev/null +++ b/ssh-keyscan.0 @@ -0,0 +1,107 @@ +SSH-KEYSCAN(1) OpenBSD Reference Manual SSH-KEYSCAN(1) + +NAME + ssh-keyscan - gather ssh public keys + +SYNOPSIS + ssh-keyscan [-46Hv] [-f file] [-p port] [-T timeout] [-t type] + [host | addrlist namelist] [...] + +DESCRIPTION + ssh-keyscan is a utility for gathering the public ssh host keys of a num- + ber of hosts. It was designed to aid in building and verifying + ssh_known_hosts files. ssh-keyscan provides 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 pos- + 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 pro- + cess involve any encryption. + + The options are as follows: + + -4 Forces ssh-keyscan to use IPv4 addresses only. + + -6 Forces ssh-keyscan to use IPv6 addresses only. + + -f file + Read hosts or addrlist namelist pairs from this file, one per + line. If - is supplied instead of a filename, ssh-keyscan will + read hosts or addrlist namelist pairs from the standard input. + + -H Hash all hostnames and addresses in the output. Hashed names may + be used normally by ssh and sshd, but they do not reveal identi- + fying information should the file's contents be disclosed. + + -p port + Port to connect to on the remote host. + + -T timeout + Set 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. De- + fault 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 protocol version 2. Multiple values may + be specified by separating them with commas. The default is + ``rsa1''. + + -v Verbose mode. Causes ssh-keyscan to print debugging messages + about its progress. + +SECURITY + If an ssh_known_hosts file is constructed using ssh-keyscan without veri- + fying the keys, users will be vulnerable to man in the middle attacks. + On the other hand, if the security model allows such a risk, ssh-keyscan + can help in the detection of tampered keyfiles or man in the middle at- + tacks which have begun after the ssh_known_hosts file was created. + +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-dss''. + + /etc/ssh/ssh_known_hosts + +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 - + +SEE ALSO + ssh(1), sshd(8) + +AUTHORS + David Mazieres <dm@lcs.mit.edu> wrote the initial version, and Wayne + Davison <wayned@users.sourceforge.net> added support for protocol version + 2. + +BUGS + 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. + +OpenBSD 4.1 January 1, 1996 2 |