Class Net::SSH::KnownHosts

  1. lib/net/ssh/known_hosts.rb
Parent: Object

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.

Methods

public class

  1. add
  2. hostfiles
  3. new
  4. search_for
  5. search_in

public instance

  1. add
  2. keys_for

Attributes

source [R] The host-key file name that this KnownHosts instance will use to search for keys.

Public class methods

add (host, key, options={})

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.

[show source] 
    # File lib/net/ssh/known_hosts.rb, line 52
52:       def add(host, key, options={})
53:         hostfiles(options, :user).each do |file|
54:           begin
55:             KnownHosts.new(file).add(host, key)
56:             return
57:           rescue SystemCallError
58:             # try the next hostfile
59:           end
60:         end
61:       end
hostfiles (options, which=:all)

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.

[show source] 
    # File lib/net/ssh/known_hosts.rb, line 35
35:       def hostfiles(options, which=:all)
36:         files = []
37: 
38:         if which == :all || which == :user
39:           files += Array(options[:user_known_hosts_file] || %w(~/.ssh/known_hosts ~/.ssh/known_hosts2))
40:         end
41: 
42:         if which == :all || which == :global
43:           files += Array(options[:global_known_hosts_file] || %w(/etc/ssh/known_hosts /etc/ssh/known_hosts2))
44:         end
45: 
46:         return files
47:       end
new (source)

Instantiate a new KnownHosts instance that will search the given known-hosts file. The path is expanded file File.expand_path.

[show source] 
    # File lib/net/ssh/known_hosts.rb, line 70
70:     def initialize(source)
71:       @source = File.expand_path(source)
72:     end
search_for (host, options={})

Searches all known host files (see KnownHosts.hostfiles) for all keys of the given host. Returns an array of keys found.

[show source] 
    # File lib/net/ssh/known_hosts.rb, line 16
16:       def search_for(host, options={})
17:         search_in(hostfiles(options), host)
18:       end
search_in (files, host)

Search for all known keys for the given host, in every file given in the files array. Returns the list of keys.

[show source] 
    # File lib/net/ssh/known_hosts.rb, line 22
22:       def search_in(files, host)
23:         files.map { |file| KnownHosts.new(file).keys_for(host) }.flatten
24:       end

Public instance methods

add (host, key)

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.

[show source] 
     # File lib/net/ssh/known_hosts.rb, line 121
121:     def add(host, key)
122:       File.open(source, "a") do |file|
123:         blob = [Net::SSH::Buffer.from(:key, key).to_s].pack("m*").gsub(/\s/, "")
124:         file.puts "#{host} #{key.ssh_type} #{blob}"
125:       end
126:     end
keys_for (host)

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
[show source] 
     # File lib/net/ssh/known_hosts.rb, line 87
 87:     def keys_for(host)
 88:       keys = []
 89:       return keys unless File.readable?(source)
 90: 
 91:       entries = host.split(/,/)
 92: 
 93:       File.open(source) do |file|
 94:         scanner = StringScanner.new("")
 95:         file.each_line do |line|
 96:           scanner.string = line
 97: 
 98:           scanner.skip(/\s*/)
 99:           next if scanner.match?(/$|#/)
100: 
101:           hostlist = scanner.scan(/\S+/).split(/,/)
102:           next unless entries.all? { |entry| hostlist.include?(entry) }
103: 
104:           scanner.skip(/\s*/)
105:           type = scanner.scan(/\S+/)
106: 
107:           next unless %w(ssh-rsa ssh-dss).include?(type)
108: 
109:           scanner.skip(/\s*/)
110:           blob = scanner.rest.unpack("m*").first
111:           keys << Net::SSH::Buffer.new(blob).read_key
112:         end
113:       end
114: 
115:       keys
116:     end