Real-time collaboration for Jupyter Notebooks, Linux Terminals, LaTeX, VS Code, R IDE, and more,
all in one place.

1
# -*- coding: binary -*-
2

3
require 'rex/socket'
4
require 'forwardable'
5

6
module Rex
7
module Proto
8
module DNS
9
  ##
10
  # This class manages statically defined hostnames for DNS resolution where each name is a mapping to an IPv4 and or
11
  # an IPv6 address. A single hostname can only map to one address of each family.
12
  ##
13
  class StaticHostnames
14
    extend Forwardable
15

16
    def_delegators :@hostnames, :each, :each_with_index, :length, :empty?, :sort_by
17

18
    # @param [Hash<String, IPAddr>] hostnames The hostnames to IP address mappings to initialize with.
19
    def initialize(hostnames: nil)
20
      @hostnames = {}
21
      if hostnames
22
        hostnames.each do |hostname, ip_address|
23
          add(hostname, ip_address)
24
        end
25
      end
26
    end
27

28
    # Locate and parse a hosts file on the system. Only the first hostname to IP address definition is used which
29
    # replicates the behavior of /etc/hosts on Linux. Loaded definitions are merged with existing definitions.
30
    def parse_hosts_file
31
      path = %w[
32
        %WINDIR%\system32\drivers\etc\hosts
33
        /etc/hosts
34
        /data/data/com.termux/files/usr/etc/hosts
35
      ].find do |path|
36
        path = File.expand_path(path)
37
        File.file?(path) && File.readable?(path)
38
      end
39
      return unless path
40

41
      path = File.expand_path(path)
42
      ::IO.foreach(path) do |line|
43
        words = line.split
44
        next unless words.length > 1 && Rex::Socket.is_ip_addr?(words.first)
45

46
        ip_address = IPAddr.new(words.shift)
47
        words.each do |hostname|
48
          add(hostname, ip_address)
49
        end
50
      end
51
    end
52

53
    # Get an IP address of the specified type for the hostname. Only the first address is returned in cases where
54
    # multiple addresses are defined.
55
    #
56
    # @param [String] hostname The hostname to retrieve an address for.
57
    # @param [Integer] type The family of address to return represented as a DNS type (either A or AAAA).
58
    # @return Returns the IP address if it was found, otherwise nil.
59
    # @rtype [IPAddr, nil]
60
    def get1(hostname, type = Dnsruby::Types::A)
61
      get(hostname, type).first
62
    end
63

64
    # Get all IP addresses of the specified type for the hostname.
65
    #
66
    # @param [String] hostname The hostname to retrieve an address for.
67
    # @param [Integer] type The family of address to return represented as a DNS type (either A or AAAA).
68
    # @return Returns an array of IP addresses.
69
    # @rtype [Array<IPAddr>]
70
    def get(hostname, type = Dnsruby::Types::A)
71
      hostname = hostname.downcase
72
      @hostnames.fetch(hostname, {}).fetch(type, []).dup
73
    end
74

75
    # Add an IP address for the specified hostname.
76
    #
77
    # @param [String] hostname The hostname whose IP address is being defined.
78
    # @param [IPAddr, String] ip_address The IP address that is being defined for the hostname. If this value is a
79
    #   string, it will be converted to an IPAddr instance.
80
    def add(hostname, ip_address)
81
      unless self.class.is_valid_hostname?(hostname)
82
        # it is important to validate the hostname because assumptions about what characters it may contain are made
83
        # when saving and loading it from the configuration
84
        raise ::ArgumentError.new("Invalid hostname: #{hostname}")
85
      end
86

87
      ip_address = IPAddr.new(ip_address) if ip_address.is_a?(String) && Rex::Socket.is_ip_addr?(ip_address)
88

89
      hostname = hostname.downcase.delete_suffix('.')
90
      this_host = @hostnames.fetch(hostname, {})
91
      if ip_address.family == ::Socket::AF_INET
92
        type = Dnsruby::Types::A
93
      else
94
        type = Dnsruby::Types::AAAA
95
      end
96
      this_type = this_host.fetch(type, [])
97
      this_type << ip_address unless this_type.include?(ip_address)
98
      this_host[type] = this_type
99
      @hostnames[hostname] = this_host
100
      nil
101
    end
102

103
    # Delete an IP address for the specified hostname.
104
    #
105
    # @param [String] hostname The hostname whose IP address is being undefined.
106
    # @param [IPAddr, String] ip_address The IP address that is being undefined. If this value is a string, it will be
107
    #   converted to an IPAddr instance.
108
    def delete(hostname, ip_address)
109
      ip_address = IPAddr.new(ip_address) if ip_address.is_a?(String) && Rex::Socket.is_ip_addr?(ip_address)
110
      if ip_address.family == ::Socket::AF_INET
111
        type = Dnsruby::Types::A
112
      else
113
        type = Dnsruby::Types::AAAA
114
      end
115

116
      hostname = hostname.downcase
117
      this_host = @hostnames.fetch(hostname, {})
118
      this_type = this_host.fetch(type, [])
119
      this_type.delete(ip_address)
120
      if this_type.empty?
121
        this_host.delete(type)
122
      else
123
        this_host[type] = this_type
124
      end
125
      if this_host.empty?
126
        @hostnames.delete(hostname)
127
      else
128
        @hostnames[hostname] = this_host
129
      end
130

131
      nil
132
    end
133

134
    # Delete all hostname to IP address definitions.
135
    def flush
136
      @hostnames.clear
137
    end
138

139
    def self.is_valid_hostname?(name)
140
      # check if it appears to be a fully qualified domain name, e.g. www.metasploit.com
141
      return true if Rex::Socket.is_name?(name)
142

143
      # check if it appears to at least be a valid hostname, e.g. localhost
144
      return true if (name =~ /^([a-z0-9][a-z0-9\-]{0,61})?[a-z0-9]$/i) && (name =~ /\s/).nil?
145

146
      false
147
    end
148
  end
149
end
150
end
151
end
152

153