Load RSA key from ssh id_rsa.pub file (timid)

load_id_rsa.rb

def load_rsa_key(key)
  case key
    when nil
      raise ArgumentError, "Key cannot be nil"
    when OpenSSL::PKey::PKey
      key
    when String, File, IO
      text = read_file(key)
      if text =~ /^ssh-rsa/
        load_ssh_pubkey text
      else
        OpenSSL::PKey.read text
      end
    end
end

private 

def load_ssh_pubkey(text)
  rsakey = OpenSSL::PKey::RSA.new
  text.lines.each do |line|
    base64 = line.chomp.split[1]
    keydata = base64.unpack("m").first
    parts = Array.new
    while (keydata.length > 0)
      dlen = keydata[0, 4].bytes.inject(0) do |a, b|
        (a << 8) + b
      end
      data = keydata[4, dlen]
      keydata = keydata[(dlen + 4)..-1]
      parts.push(data)
    end
    type = parts[0]
    raise ArgumentError, "Unsupported key type #{type}" unless type == "ssh-rsa"
    e = parts[1].bytes.inject do |a, b|
      (a << 8) + b
    end
    n = parts[2].bytes.inject do |a, b|
      (a << 8) + b
    end
    rsakey.n = n
    rsakey.e = e
  end
  rsakey
end

def read_file file
  f = open_file file, 'r'
  f.read
end
  
def open_file file, mode
  case file
  when String
    File.open file, mode
  when File, IO
    file
  else
    raise ArgumentError, "Invalid file #{file}"
  end
end