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module Rex::Proto::Gss::Asn1
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  #
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  # GSS has some "pseudo-asn1" to wrap up tokens. This function parses that wrapping, extracts
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  # the mechanism specified, and returns it and the token following it
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  def unwrap_pseudo_asn1(token)
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    start_of_token = nil
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    mech_id = nil
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    # This bit is pseudo-ASN1 - we parse up until the OID, then take note of where we got up 
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    # to, and continue parsing from there.
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    OpenSSL::ASN1.traverse(token) do | depth, offset, header_len, length, constructed, tag_class, tag|
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      component = token[offset, header_len+length]
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      if depth == 1 && tag_class == :UNIVERSAL && tag == 6
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        mech_id = OpenSSL::ASN1.decode(component)
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        start_of_token = offset+header_len+length
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        break
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      end
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    end
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    [mech_id, token[start_of_token, token.length - start_of_token]]
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  end
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  def wrap_pseudo_asn1(mech_id, token)
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    OpenSSL::ASN1::ASN1Data.new(
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      [
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        mech_id,
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        token
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      ],
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      0,
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      :APPLICATION
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    ).to_der
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  end
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end
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