Module: Rex::Proto::Gss::Asn1

Included in:
Msf::Exploit::Remote::Kerberos::ServiceAuthenticator::Base, KerberosToken, Kerberos::Crypto::Rc4Hmac, LDAP::AuthAdapter::RexKerberos::Encryptor
Defined in:
lib/rex/proto/gss/asn1.rb

Overview

Helpers for the pseudo-ASN.1 framing used by GSS mechanism tokens.

Instance Method Summary collapse

Instance Method Details

#unwrap_pseudo_asn1(token) ⇒ Object

GSS has some “pseudo-asn1” to wrap up tokens. This function parses that wrapping, extracts the mechanism specified, and returns it and the token following it



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# File 'lib/rex/proto/gss/asn1.rb', line 11

def unwrap_pseudo_asn1(token)
  start_of_token = nil
  mech_id = nil
  # This bit is pseudo-ASN1 - we parse up until the OID, then take note of where we got up
  # to, and continue parsing from there.
  OpenSSL::ASN1.traverse(token) do |depth, offset, header_len, length, _constructed, tag_class, tag|
    component = token[offset, header_len + length]
    if depth == 1 && tag_class == :UNIVERSAL && tag == 6
      mech_id = OpenSSL::ASN1.decode(component)
      start_of_token = offset + header_len + length
      break
    end
  end

  unless mech_id && start_of_token
    raise OpenSSL::ASN1::ASN1Error, 'GSS token does not contain a top-level mechanism OID'
  end

  [mech_id, token.byteslice(start_of_token, token.bytesize - start_of_token)]
end

#wrap_pseudo_asn1(mech_id, token) ⇒ Object 



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# File 'lib/rex/proto/gss/asn1.rb', line 32

def wrap_pseudo_asn1(mech_id, token)
  OpenSSL::ASN1::ASN1Data.new(
    [
      mech_id,
      token
    ],
    0,
    :APPLICATION
  ).to_der
end