Module: ExecSandbox::Users

Defined in:
lib/exec_sandbox/users.rb

Overview

Manages sandbox users.

See Also:

Class Method Summary collapse

Class Method Details

.create(user_name, primary_group_name = nil) ⇒ Fixnum

Creates a user for unprivileged operations.

Parameters:

  • user_name (String) —

    the user’s short (UNIX) name (should be unique)

  • primary_group_name; (String) —

    if no name is supplied, the user’s primary group will be set to a new group

Returns:

  • (Fixnum) —

    the new user’s UID



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# File 'lib/exec_sandbox/users.rb', line 37

def self.create(user_name, primary_group_name = nil)
  group_id = primary_group_name && Etc.getgrnam(primary_group_name).gid 
  
  if RUBY_PLATFORM =~ /darwin/  # OSX
    home_dir = "/Users/#{user_name}" 
    unless group_id
      # Create a group with the same name as the user.
      group_id = `dscl . -list /Groups`.split.
          map { |g| `dscl . -read /Groups/#{g} PrimaryGroupID`.split.last.
          to_i }.sort.last + 1

      # Simulate adduser's group creation.
      command_prefix = ['dscl', '.', '-create', "/Groups/#{user_name}"]
      [
        [],
        ['PrimaryGroupID', group_id.to_s],
      ].each do |command_suffix|
        command = command_prefix + command_suffix
        unless Kernel.system(*command)
          raise RuntimeError, "User creation failed at #{command.inspect}!"
        end
      end
    end
    
    # Find an available UID.
    user_id = `dscl . -list /Users`.split.
        map { |u| `dscl . -read /Users/#{u} UniqueID`.split.last.to_i }.
        sort.last + 1
  
    # Simulate adduser.
    command_prefix = ['dscl', '.', '-create', "/Users/#{user_name}"]
    [
      [],
      ['UserShell', '/bin/bash'],
      ['UniqueID', user_id.to_s],
      ['PrimaryGroupID', group_id.to_s],
      ['NFSHomeDirectory', home_dir],
    ].each do |command_suffix|
      command = command_prefix + command_suffix
      unless Kernel.system(*command)
        raise RuntimeError, "User creation failed at #{command.inspect}!"
      end
    end
    
  elsif RUBY_PLATFORM =~ /win/  # Windows
    raise 'Windows is not supported; patches welcome!'
    
  else  # Linux
    if group_id
      command = ['useradd', '--gid', group_id.to_s, '--no-user-group',
                 '--no-create-home', '--system',
                 '--comment', 'exec_sandbox.rb temporary user', user_name]
    else
      command = ['useradd', '--user-group', '--no-create-home', '--system',
                 '--comment', 'exec_sandbox.rb temporary user', user_name]
    end
    unless Kernel.system(*command)
      raise RuntimeError, "User creation failed at #{command.inspect}!"
    end
  
    home_dir = File.join '/home', user_name
    user_id = Etc.getpwnam(user_name).uid
    group_id = Etc.getpwnam(user_name).gid
  end  # RUBY_PLATFORM

  FileUtils.mkdir_p home_dir
  FileUtils.chown_R user_id, group_id, home_dir
  FileUtils.chmod_R 0750, home_dir
  
  user_id
end

.destroy(user_name) ⇒ Object

Removes a user that was previously created by create.

Parameters:

  • user_name (String) —

    the user’s short (UNIX) name



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# File 'lib/exec_sandbox/users.rb', line 112

def self.destroy(user_name)
  user_pw = Etc.getpwnam(user_name)
  home_dir = user_pw.dir
  FileUtils.rm_rf home_dir
  
  user_gid = user_pw.gid
  group_name = Etc.getgrgid(user_gid).name
  # If the group name matches the user name, the group is a temp.
  destroy_group = user_name == group_name
  
  if RUBY_PLATFORM =~ /darwin/  # OSX
    command = ['dscl', '.', '-delete', "/Users/#{user_name}"]
    unless Kernel.system(*command)
      raise RuntimeError, "User removal failed at #{command.inspect}!"
    end

    if destroy_group
      command = ['dscl', '.', '-delete', "/Groups/#{group_name}"]
      unless Kernel.system(*command)
        raise RuntimeError, "User removal failed at #{command.inspect}!"
      end
    end
  elsif RUBY_PLATFORM =~ /win/  # Windows
    raise 'Windows is not supported; patches welcome!'
    ['userdel', git_user]
  else  # Linux
    command = ['userdel', user_name]
    unless Kernel.system(*command)
      raise RuntimeError, "User removal failed at #{command.inspect}!"
    end
    if destroy_group
      # Make sure that the group exists. userdel might remove it.
      begin
        Etc.getgrnam(group_name)
      rescue ArgumentError
        destroy_group = false
      end
    end
    if destroy_group
      command = ['groupdel', group_name]
      unless Kernel.system(*command)
        raise RuntimeError, "User removal failed at #{command.inspect}!"
      end
    end
  end  # RUBY_PLATFORM
end

.destroy_temps(prefix = 'xsbx.rb') ⇒ Array<String>

Destroys users created by temp.

Parameters:

  • prefix (String) (defaults to: 'xsbx.rb') —

    match the prefix given to temp

Returns:

  • (Array<String>) —

    names of users that were deleted



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# File 'lib/exec_sandbox/users.rb', line 175

def self.destroy_temps(prefix = 'xsbx.rb')
  # Matches the names created by temp.
  pattern = /^#{prefix}\-[0-9a-f]+\.[0-9a-f]+\.[0-9a-f]+$/
  # Each returns the collection that it iterates over.
  self.named(pattern).each { |name| destroy name }
end

.named(pattern) ⇒ Array<String>

Finds users whose names match a String or Regexp pattern.

Parameters:

  • pattern (String) —

    matched against user names using ===

Returns:

  • (Array<String>) —

    names of users



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# File 'lib/exec_sandbox/users.rb', line 163

def self.named(pattern)
  users = []
  Etc.passwd do |user|
    users << user.name if pattern === user.name
  end
  users
end

.temp(prefix = 'xsbx.rb') ⇒ String

Creates an unprivileged user.

Parameters:

  • prefix (String) (defaults to: 'xsbx.rb') —

    used at the beginning of temporary user names to help identify the application that created the users

Returns:

  • (String) —

    the user’s name



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# File 'lib/exec_sandbox/users.rb', line 14

def self.temp(prefix = 'xsbx.rb')
  loop do
    user_name = prefix + '-%x.%x.%x' % [$PID, Time.now.to_i, rand(65536)]
    etc = nil
    begin
      etc = Etc.getpwnam(name)
    rescue ArgumentError
      # User not found: good!
    end
    next if etc
    
    create user_name
    return user_name
  end
end