metasploit-framework/lib/net/ssh/known_hosts.rb

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require 'strscan'
require 'net/ssh/buffer'
module Net; module SSH
# Searches an OpenSSH-style known-host file for a given host, and returns all
# matching keys. This is used to implement host-key verification, as well as
# to determine what key a user prefers to use for a given host.
#
# This is used internally by Net::SSH, and will never need to be used directly
# by consumers of the library.
class KnownHosts
class <<self
# Searches all known host files (see KnownHosts.hostfiles) for all keys
# of the given host. Returns an array of keys found.
def search_for(host, options={})
search_in(hostfiles(options), host)
end
# Search for all known keys for the given host, in every file given in
# the +files+ array. Returns the list of keys.
def search_in(files, host)
files.map { |file| KnownHosts.new(file).keys_for(host) }.flatten
end
# Looks in the given +options+ hash for the :user_known_hosts_file and
# :global_known_hosts_file keys, and returns an array of all known
# hosts files. If the :user_known_hosts_file key is not set, the
# default is returned (~/.ssh/known_hosts and ~/.ssh/known_hosts2). If
# :global_known_hosts_file is not set, the default is used
# (/etc/ssh/known_hosts and /etc/ssh/known_hosts2).
#
# If you only want the user known host files, you can pass :user as
# the second option.
def hostfiles(options, which=:all)
files = []
if which == :all || which == :user
files += Array(options[:user_known_hosts_file] || %w(~/.ssh/known_hosts ~/.ssh/known_hosts2))
end
if which == :all || which == :global
files += Array(options[:global_known_hosts_file] || %w(/etc/ssh/known_hosts /etc/ssh/known_hosts2))
end
return files
end
# Looks in all user known host files (see KnownHosts.hostfiles) and tries to
# add an entry for the given host and key to the first file it is able
# to.
def add(host, key, options={})
hostfiles(options, :user).each do |file|
begin
KnownHosts.new(file).add(host, key)
return
rescue SystemCallError
# try the next hostfile
end
end
end
end
# The host-key file name that this KnownHosts instance will use to search
# for keys.
attr_reader :source
# Instantiate a new KnownHosts instance that will search the given known-hosts
# file. The path is expanded file File.expand_path.
def initialize(source)
@source = File.expand_path(source)
end
# Returns an array of all keys that are known to be associatd with the
# given host. The +host+ parameter is either the domain name or ip address
# of the host, or both (comma-separated). Additionally, if a non-standard
# port is being used, it may be specified by putting the host (or ip, or
# both) in square brackets, and appending the port outside the brackets
# after a colon. Possible formats for +host+, then, are;
#
# "net.ssh.test"
# "1.2.3.4"
# "net.ssh.test,1.2.3.4"
# "[net.ssh.test]:5555"
# "[1,2,3,4]:5555"
# "[net.ssh.test]:5555,[1.2.3.4]:5555
def keys_for(host)
keys = []
return keys unless File.readable?(source)
entries = host.split(/,/)
File.open(source) do |file|
scanner = StringScanner.new("")
file.each_line do |line|
scanner.string = line
scanner.skip(/\s*/)
next if scanner.match?(/$|#/)
hostlist = scanner.scan(/\S+/).split(/,/)
next unless entries.all? { |entry| hostlist.include?(entry) }
scanner.skip(/\s*/)
type = scanner.scan(/\S+/)
next unless %w(ssh-rsa ssh-dss).include?(type)
scanner.skip(/\s*/)
blob = scanner.rest.unpack("m*").first
keys << Net::SSH::Buffer.new(blob).read_key
end
end
keys
end
# Tries to append an entry to the current source file for the given host
# and key. If it is unable to (because the file is not writable, for
# instance), an exception will be raised.
def add(host, key)
# Forget that. No way I want this thing writing to my known_hosts file.
# Some day, make this configurable. Until that day, off by default.
return
File.open(source, "a") do |file|
blob = [Net::SSH::Buffer.from(:key, key).to_s].pack("m*").gsub(/\s/, "")
file.puts "#{host} #{key.ssh_type} #{blob}"
end
end
end
end; end