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diff --git a/ssh-keyscan.0 b/ssh-keyscan.0 new file mode 100644 index 0000000..ee73788 --- /dev/null +++ b/ssh-keyscan.0 @@ -0,0 +1,121 @@ +SSH-KEYSCAN(1) General Commands Manual SSH-KEYSCAN(1) + +NAME + ssh-keyscan M-bM-^@M-^S gather SSH public keys from servers + +SYNOPSIS + ssh-keyscan [-46cDHv] [-f file] [-O option] [-p port] [-T timeout] + [-t type] [host | addrlist namelist] + +DESCRIPTION + ssh-keyscan is a utility for gathering the public SSH host keys of a + number of hosts. It was designed to aid in building and verifying + ssh_known_hosts files, the format of which is documented in sshd(8). + 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 + possible 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 sshd(8). For scanning, one does not need + login access to the machines that are being scanned, nor does the + scanning process involve any encryption. + + Hosts to be scanned may be specified by hostname, address or by CIDR + network range (e.g. 192.168.16/28). If a network range is specified, + then all addresses in that range will be scanned. + + The options are as follows: + + -4 Force ssh-keyscan to use IPv4 addresses only. + + -6 Force ssh-keyscan to use IPv6 addresses only. + + -c Request certificates from target hosts instead of plain keys. + + -D Print keys found as SSHFP DNS records. The default is to print + keys in a format usable as a ssh(1) known_hosts file. + + -f file + Read hosts or M-bM-^@M-^\addrlist namelistM-bM-^@M-^] pairs from file, one per line. + If M-bM-^@M-^X-M-bM-^@M-^Y is supplied instead of a filename, ssh-keyscan will read + from the standard input. Names read from a file must start with + an address, hostname or CIDR network range to be scanned. + Addresses and hostnames may optionally be followed by comma- + separated name or address aliases that will be copied to the + output. For example: + + 192.168.11.0/24 + 10.20.1.1 + happy.example.org + 10.0.0.1,sad.example.org + + -H Hash all hostnames and addresses in the output. Hashed names may + be used normally by ssh(1) and sshd(8), but they do not reveal + identifying information should the file's contents be disclosed. + + -O option + Specify a key/value option. At present, only a single option is + supported: + + hashalg=algorithm + Selects a hash algorithm to use when printing SSHFP + records using the -D flag. Valid algorithms are M-bM-^@M-^\sha1M-bM-^@M-^] + and M-bM-^@M-^\sha256M-bM-^@M-^]. The default is to print both. + + -p port + Connect to port 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, the connection is + closed and the host in question considered unavailable. The + default is 5 seconds. + + -t type + Specify the type of the key to fetch from the scanned hosts. The + possible values are M-bM-^@M-^\dsaM-bM-^@M-^], M-bM-^@M-^\ecdsaM-bM-^@M-^], M-bM-^@M-^\ed25519M-bM-^@M-^], M-bM-^@M-^\ecdsa-skM-bM-^@M-^], + M-bM-^@M-^\ed25519-skM-bM-^@M-^], or M-bM-^@M-^\rsaM-bM-^@M-^]. Multiple values may be specified by + separating them with commas. The default is to fetch M-bM-^@M-^\rsaM-bM-^@M-^], + M-bM-^@M-^\ecdsaM-bM-^@M-^], M-bM-^@M-^\ed25519M-bM-^@M-^], M-bM-^@M-^\ecdsa-skM-bM-^@M-^], and M-bM-^@M-^\ed25519-skM-bM-^@M-^] keys. + + -v Verbose mode: print debugging messages about progress. + + If an ssh_known_hosts file is constructed using ssh-keyscan without + verifying 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 attacks which have begun after the ssh_known_hosts file was + created. + +FILES + /etc/ssh/ssh_known_hosts + +EXAMPLES + Print the RSA host key for machine hostname: + + $ ssh-keyscan -t rsa hostname + + Search a network range, printing all supported key types: + + $ ssh-keyscan 192.168.0.64/25 + + 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,ecdsa,ed25519 -f ssh_hosts | \ + sort -u - ssh_known_hosts | diff ssh_known_hosts - + +SEE ALSO + ssh(1), sshd(8) + + Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints, RFC + 4255, 2006. + +AUTHORS + David Mazieres <dm@lcs.mit.edu> wrote the initial version, and Wayne + Davison <wayned@users.sourceforge.net> added support for protocol version + 2. + +OpenBSD 7.3 February 10, 2023 OpenBSD 7.3 |