Class: Rack::Auth::Kerberos

Inherits:
Object
  • Object
show all
Defined in:
lib/rack/auth/kerberos.rb

Overview

The Kerberos class encapsulates kerberos authentication handling.

Constant Summary collapse

VERSION =

The version of the rack-auth-kerberos library.

'0.2.5'

Instance Method Summary collapse

Constructor Details

#initialize(app, user_field = 'username', password_field = 'password', realm = nil) ⇒ Kerberos

Creates a new Rack::Kerberos object. The user_field and password_field are the params looked for in the call method. The defaults are ‘username’ and ‘password’, respectively.

If the optional realm parameter is supplied it will override the default realm specified in your krb5.conf file.

The realm is automatically appended to the username if not already present. This makes it easier for application developers, i.e. they can supply a username with or without a realm and it will Just Work (TM).



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# File 'lib/rack/auth/kerberos.rb', line 25

def initialize(app, user_field = 'username', password_field = 'password', realm = nil)
  @kerberos = nil
  @app = app
  @user_field = user_field
  @password_field = password_field
  @realm = realm
end

Instance Method Details

#call(env) ⇒ Object

The call method we’ve defined first checks to see if the AUTH_USER environment variable is set. If it is, we assume that the user has already been authenticated and move on.

If AUTH_USER is not set, and AUTH_FAIL is not set, we then attempt to authenticate the user against the Kerberos server. If successful then AUTH_USER is set to the username.

If unsuccessful then AUTH_USER is set to nil and AUTH_FAIL is set to an appropriate error message.

It is then up to the application to check for the presence of AUTH_USER and/or AUTH_FAIL and act as necessary.

Several other request environment variables are set on success:

AUTH_TYPE => “Kerberos Password” AUTH_TYPE_USER => user + realm AUTH_TYPE_THIS_REQUEST => “Kerberos Password” AUTH_DATETIME => Time.now.utc



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# File 'lib/rack/auth/kerberos.rb', line 54

def call(env)
  @kerberos = Krb5Auth::Krb5.new
  @realm ||= @kerberos.get_default_realm

  @log = "Entering Rack::Auth::Kerberos"
  request = Rack::Request.new(env)

  user = request.params[@user_field]
  password = request.params[@password_field]

  log "Kerberos user: #{user}, password length: #{password.nil? ? 'nil' : password.size}"

  # Only authenticate user if both the username and password fields are present
  unless user && password
    return @app.call(env)
  end

  # Automatically append the realm if not already present
  user_with_realm = user.dup
  user_with_realm += "@#{@realm}" unless user.include?('@')
  log "Kerberos user_with_realm: #{user_with_realm}"
  
  # Do not authenticate if either one of these is set
  if env['AUTH_USER'] || env['AUTH_FAIL']
    return @app.call(env)
  end

  begin
    @kerberos.get_init_creds_password(user_with_realm, password)
  rescue Krb5Auth::Krb5::Exception => err
    case err.message
      when /client not found/i
        msg = "Invalid userid '#{user}'"
      when /integrity check failed/i
        msg = "Invalid password for '#{user}'"
      else
        log "Krb5Auth::Krb5::Exception: #{err.message}"
        msg = "Error attempting to validate userid and password"
    end

    env.delete('AUTH_USER')
    env['AUTH_FAIL'] = msg
  rescue => err
    env.delete('AUTH_USER')
    log "Kerberos Unexpected Error: #{err.message}"
    env['AUTH_FAIL'] = "Unexpected failure during Kerberos authentication"
  else
    env.delete('AUTH_FAIL')

    env['AUTH_USER'] = user
    env['AUTH_TYPE'] = "Kerberos Password"
    env['AUTH_TYPE_USER'] = user_with_realm
    env['AUTH_TYPE_THIS_REQUEST'] = "Kerberos Password"
    env['AUTH_DATETIME'] = Time.now.utc
  ensure
    @kerberos.close
  end

  log "Kerberos sign in results: AUTH_TYPE_USER=#{env['AUTH_TYPE_USER']}, AUTH_FAIL=#{env['AUTH_FAIL']}"
  env['AUTH_LOG'] = @log
  @app.call(env)
end

#log(msg) ⇒ Object

Append a msg to a @log string that can be used for logging & debugging.



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# File 'lib/rack/auth/kerberos.rb', line 119

def log(msg)
  @log << "\n    #{msg}"
end