Spatial Signature Method (SSM) Against XML Signature Wrapping Attacks

Living in cyber world with revolutionizes of Industrial 4.0, most of the users and organisations prefer to sell and buy products or services via website online transaction. This online transaction is done through a messaging protocol (SOAP) and signing entire SOAP (SESOAP) using Extensible Markup Language (XML). XML is implemented to secure the SOAP contents by applying the signing method called as XML Digital signature. However, the XML digital signature has issues related to XML signature wrapping (XSW) attacks specifically on Sibling Value Context and Sibling Order Context attacks. Therefore, this paper proposes an enhanced method called as Spatial Signature Method (SSM) which aims to resolve the limitation of SESOAP from the aspect of XSW attacks. It proposes new parameters for XML digital signature inspired by the concept of ratio and space in biotechnology to detect the XSW attacks. The experiment was conducted in a controlled lab by using the Ubuntu Linux system and PHP programming. Based on the comparison made with SESOAP and ID Referencing method (IDR), SSM has proven to defend against the XSW attacks. For the future work, the spatial signature method can be forged with more extensive spatial information for the digital signature and to integrate it with web services.


Introduction
Simple Object Access Protocol (SOAP) is a protocol used in handling information exchange between clients and servers for web services. While XML digital signature protects the SOAP from XML signature wrapping (XSW) attacks. Unfortunately, XSW attacks specifically sibling value context and sibling order context attacks are able to exploit SOAP [1][2][3][4]. As for sibling value context or known as security header injection, the message is attached to a different ancestor which change the meaning entirely and it is within the security header. While sibling order context or known as namespace injection, exploits the order of the messages, which affects its meaning and implication. In order to solve these attacks, signing entire SOAP (SESOAP) and ID Referencing (IDR) have been developed, but it is time consuming, affects the web services performance and are not able to encounter the XML signature wrapping attacks completely such as multiple assertions and multiple signatures. The XSW attacks started in the year 2013, where it launched attacks to the Amazon online website and until now still a challenge to be solved by the web developer. Hence, in this paper, a new method called as Spatial Signature Method (SSM) is proposed to countermeasure against the XSW attacks. It is inspired by the concept of space and ratio in the biotechnology field and the principle is used to detect abnormality for XML digital signature and to combat the XSW attacks.
This paper is organized as follows: Section 2 presents existing work related to XWS attack detection techniques. Section 3 describes the methodology used in this research. Section 4 presents the results of experiments carried out in this research. Section 5 includes the summary and potential future work of this paper.

Related Work
There are several approaches against XWS attacks and these are summarised in Table 1. There are four types of XSW attacks which are simple ancestry context, optional element context, sibling value context (security header) and sibling order context (namespace injection), where most detection methods are only encountering simple ancestry context and optional element context attacks. As for sibling value context and sibling order context attacks, only IDR and SESOAP are able to encounter these attacks, though these two techniques cannot encounter XSW attacks completely [5]. Therefore, SSM is developed and proposed in this paper to fill in the existing gaps and challenges in encountering XSW attacks. Another main concern is time processing or known as performance to form the XML digital

Method Description Limitation
XPath Expression [7] 1) It selects complex node sets based on the XPath specification and uses timestamp as a reference. Xu et al. [12] hypothesized that the imbalance of two opposing effects in lung cancer cells, represented by yin and yang genes. It determines a patient's prognosis. Yin and yang genes are compared based on the expression data from normal lung and lung that is infected by cancer. The proposed Spatial Signature Method (SSM) is inspired by the concept of ratio and space in biotechnology, where specific set of critical points are extracted for the digital signature to build up the spatial method. The mapping between the ratio signature model and the SSM can be found in Table 2. The SSM concept is inspired from the notion of ratio signature, which exploits the relative difference of certain measures to ascertain a particular diagnosis. Yin and Yang balance status in lung cells is referred as the ratio.
SSM selects a collection of specific points as spatial identity from the original message. Any changes to the spatial information can be detected by SSM.
The ratio is referred as the location and total number of the gene expression.
SSM defines the location and size (total number) of the original message from the SOAP message.

Methodology
The overall processes involved in this experiment are summarised in Figure 1. The components involved in this experiment are depicted in Table 3.

Table 3. Experimentation Setup
An example of the SSM creation is illustrated in Figure  2(a)~(b), where it is being attached before the close header. Fig. 2(a). Illustration for SOAP Message extraction and formation of SSM.

Finding
For evaluation purpose, four XSW attacks have been launched and the results are as the following. As for the simple ancestry context attack, SSM has successfully detected this attack, which leads to validation process failed, and tampered message is rejected. This process is illustrated in Figure 3. For optional element attack, SSM has successfully detected the tampering message. This attack tried to change the total size of the entire SOAP message. This is simplified and illustrated in Figure 4.
As for the sibling value attack, SSM has successfully detected this attack, which leads to validation process failed, and tampered message is rejected. This process is illustrated in Figure 5. SSM solved the unprocessed <Security> tag within the spatial information, which can lead to changes of spatial information value.   As for the sibling order attack, SSM has successfully detected this attack, which leads to validation process failed. This process is illustrated in Figure 6. When the information being reordered by the attacker, SSM has detected the changes.

Entity and Specification
Based on the above testing for the XSW attacks, SSM has successfully detected all of these attacks compared to SESOAP and IDR. Fig. 6. SSM detected the sibling order attack.

Conclusion
Spatial Signature Method (SSM) is inspired by the notion of ratio signature model in cancer detection. Reasoning analogically, the XSW attacks can be perceived as a cancer which innately destructive to the body and in a form of anomaly to the XML message. These XSW attacks would be destructive to the web services. Based on the evaluation conducted, SSM has successfully detected all the XSW attacks which are very beneficial and a great contribution to the web security area. For future work, SSM can be forged with more extensive spatial information for the digital signature and can be integrated with web services.