Class: Rack::Shibboleth::Response

Inherits:
Object
  • Object
show all
Defined in:
lib/rack/shibboleth/response.rb

Overview

Encapsulates the logic for parsing the response of an IdP to the application. The XML of the response has already been extracted and is the parameter for the construction of this class

Instance Method Summary (collapse)

Constructor Details

- (Response) initialize(xml)

Initializes a new response with the given XML from the IdP

Parameters:

  • xml (String)

    the response from the IdP



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# File 'lib/rack/shibboleth/response.rb', line 19

def initialize xml
  begin
    @doc = LibXML::XML::Document.string(xml)
  rescue LibXML::XML::Error
    @doc = nil
  end
end

Instance Method Details

- (LibXML::XML::Document) decode(private_key)

Decodes the response of the IdP and retuns the decrypted XML

Parameters:

  • private_key (OpenSSL::PKey::RSA)

    the corresponding key to the public key which was used to encrypt the response.

Returns:

  • (LibXML::XML::Document)

    The XML document which was decrypted, or if decryption failed, nil is returned.



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# File 'lib/rack/shibboleth/response.rb', line 34

def decode private_key
  # This is the public key which encrypted the first CipherValue
  cert   = @doc.find_first(
      '//xenc:EncryptedData//ds:X509Certificate', [DS, XENC]).content
  c1, c2 = @doc.find('//xenc:CipherValue', XENC).map(&:content)

  cert = OpenSSL::X509::Certificate.new(Base64.decode64(cert))
  return nil unless cert.check_private_key(private_key)

  # Generate the key used for the cipher below via the RSA::OAEP algo
  rsak = RSA::Key.new private_key.n, private_key.d
  v1s  = Base64.decode64(c1)

  begin
    cipherkey = RSA::OAEP.decode rsak, v1s
  rescue RSA::OAEP::DecodeError
    return nil
  end

  # The aes-128-cbc cipher has a 128 bit initialization vector (16 bytes)
  # and this is the first 16 bytes of the raw string.
  bytes  = Base64.decode64(c2).unpack('C*')
  iv     = bytes.pack('c16')
  others = bytes.pack('c16X16c*')

  cipher = OpenSSL::Cipher.new('aes-128-cbc')
  cipher.decrypt
  cipher.iv  = iv
  cipher.key = cipherkey

  out = cipher.update(others)

  # The encrypted string's length might not be a multiple of the block
  # length of aes-128-cbc (16), so add in another block and then trim
  # off the padding. More info about padding is available at
  # http://www.w3.org/TR/2002/REC-xmlenc-core-20021210/Overview.html in
  # Section 5.2
  out << cipher.update("\x00" * 16)
  padding = out.bytes.to_a.last

  dec = LibXML::XML::Document.string(out[0..-(padding + 1)])

  # Must check that there is a signature listed and that the signature is
  # valid for the enclosing document.
  sig = dec.find_first('//ds:Signature', DS)
  if sig && valid_hashes?(sig) && valid_signature?(sig)
    dec
  end
end