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Versions: 00                                                            
SFC                                                                C. Li
Internet-Draft                                                   Z. Tang
Intended status: Informational                                   C. Chen
Expires: October 2, 2021                   Zhejiang Gongshang University
                                                          March 31, 2021

                      SFC Security Mimicry Defense


   With the increase of network threats, the Service Function Chain
   (SFC) is vulnerable to various attacks, and as a key component of the
   entire SFC, the security of the service function (SF) is more
   critical.  This document proposes a mimic SF security architecture
   based on the dynamic heterogeneous redundancy model, which can
   effectively protect the normal execution function of SF in SFC.  The
   security architecture adopts an active defense method to defend
   against network attacks, and it can effectively defend against most
   SF attacks.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 2, 2021.

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   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Security issues of SFC  . . . . . . . . . . . . . . . . . . .   3
     3.1.  Tamper with Network Service Header  . . . . . . . . . . .   3
     3.2.  Attack Service Function . . . . . . . . . . . . . . . . .   3
   4.  SFC Security Mimicry Defense  . . . . . . . . . . . . . . . .   4
     4.1.  Mimicry Defense . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  SFC Mimicry Defense Architecture  . . . . . . . . . . . .   5
     4.3.  Data Flow . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.4.  Analysis of Attack and Defense  . . . . . . . . . . . . .   7
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   SF is the most critical part of the entire SFC.  The data flow in the
   SFC domain must go through specific SFs to complete a specific
   function.  If the SF is controlled by the hacker, the hacker can
   tamper with and discard the data by the hijacked SF, and even
   paralyze the SFF by DOS attacks.  It can not only result in the
   failure of specified functioning when operating SF, but it may also
   cause the collapse of the entire SFC domain, which completely
   violates the original intention of SFC.

   This document describes a mimic security architecture based on
   Dynamic Heterogeneous Redundancy Model (DHRM), adopting a proactive
   defense method to deal with the SFC security problems mentioned

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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3.  Security issues of SFC

3.1.  Tamper with Network Service Header

   [RFC8300] points out that the NSH (Network Service Header) is the SFC
   encapsulation referenced in [RFC7665].NSH contains path
   identification information to implement service paths.  Metadata
   information is also included which enables service functions to share
   initial and intermediate classification results with downstream
   service functions.  NSH provides functions to monitor and
   troubleshoot the SFC.

   [RFC8300]mentions three methods of protecting NSH headers: SFF / SF
   NSH Verification, Transport Security, NSH Variable Header-Based

   However, the above three methods cannot solve the NSH tampering
   problem effectively.  If a hacker cracks the encryption mode of NSH
   and obtained the permission successfully to change the header of a
   certain SF, the hacker can change the NSH information, and the data
   is therefore discarded when returns to SFF without finding the
   mapping relationship.  While in practical applications, it is
   impossible for each SFF to belong to only a specific SFC.  Thus, if a
   hacker obtains the mapping relationship in the SFF, the hacker can
   change the NSH information to make the packet taking another SFC
   path, and the control plane cannot detect it.  By changing the
   metadata information, the hacker can even make all devices in the SFC
   domain reach a wrong consensus.

3.2.  Attack Service Function

   If a hacker attacks the SF directly and successfully controls the SF,
   obtaining all the permissions of the SF, the hacker can manipulate
   the SF arbitrarily.  SFC domain may leads to the following damage.

   a.  The packets passing through the SF may be tampered with,
       discarded, or even diverted to the hacker server, thereby
       intercepting the effective information in the network traffic.
       For example, a hacker can tamper with the data fields of all data
       packets flowing through the SF.

   b.  This will cause all the packets in the SFC domain that pass the
       SF to be finally sent to the destination host with incorrect
       information.  Even if the destination host finds an error and
       discards the packet, it will cause the waste of bandwidth and
       normal SF resources.

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   c.  The attacker can directly change the functions completed by the
       SF, which is difficult to detect.  Assuming that the firewall
       function is to filter useful information, and due to the unknown
       information that the firewall need to filter in the control
       level, it seems that the firewall still completes the filtering
       function, actually, it is the useful packet which is filtered.
       Even if it notices a lot of information that should not be
       present in the SFC, it is not easy to locate which specific part
       has been attacked.

4.  SFC Security Mimicry Defense

   This document designs a mimic SF defense architecture based on a
   Dynamic Heterogeneous Redundancy Model (DHRM).  This framework
   ensures the security of SF by setting up an SF executive pool
   composed of M heterogeneous SFs, and the control plane manages the SF
   executive pool.  Assuming that the decision algorithm is perfectly
   performed without any wrong outcome, the SF will be offline and
   cleaned by the control plane once the execution result of the SF is
   wrong, The following sub-chapter illustrates the architecture and
   mimic defense process specifically.

4.1.  Mimicry Defense

   The mimic defense technology is an active defense strategy proposed
   against the serious asymmetry of the defense cost and attack cost of
   cyberspace.  The redundancy and heterogeneity of the executive body
   are introduced to change the unity and similarity of the system, and
   the dynamic and randomness are adopted to change the stativity and
   certainty of the system, and the non-similar redundancy space is used
   to block or disrupt the network attack to meet the requirements of
   controllable system security risks.

   Specifically, the mimic security defense is composed of executive
   bodies with equivalent functions but different composition structures
   to form the core function.  Based on the DHRM, randomness and
   dynamicity are realized, and the heterogeneous executive bodies in
   the heterogeneous executive pool are continuously changing, which
   greatly improves the dynamics and uncertainty of functional
   representation.  It makes it difficult for a hacker to detect the
   behavior and characteristics of the target system, increasing the
   complexity of the system, and also makes it difficult for hackers to
   exploit system vulnerabilities to make effective attacks.

   The DHRM is the basic model of mimic defense.  Heterogeneity is the
   foundation of the dynamic heterogeneous redundancy architecture.  It
   is necessary to ensure that each heterogeneous executive has the
   greatest difference in various characteristics and attributes.  The

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   more heterogeneous attributes a heterogeneous executor has, the more
   loopholes it can defend, and the higher the cost and price an
   attacker will have to pay for an attack.  Dynamicity means that
   different sets of heterogeneous actuators can be generated in
   different periods to replace the currently compromised set of
   heterogeneous actuators.  Dynamicity makes the system present
   different characteristics to the outside world in different periods.
   This brings uncertainty to the attacker's attack, which will further
   increase the difficulty of the attacker's attack.  Redundancy means
   that multiple heterogeneous executors which have the same function
   process the same business request.  The collaborative work between
   the heterogeneity and redundancy realizes the change of the single
   environment on which the attack depends, increasing the attacker's
   attack cost and difficulty, and improving the security and
   reliability of the system.  This concept was first proposed in 2013
   and has been effectively applied in the field of cyberspace security,
   such as mimic routers, mimic web servers, mimic DNS, mimic workflow
   execution system, mimic blockchain, etc.  In addition, some mimic
   network devices have been produced and tested successfully.

4.2.  SFC Mimicry Defense Architecture

   |                                 Control   Plane                     |
            |          |         |               |           |
            |          | +=====================+ |+======================+
            |          | |   Mimetic Control   | ||    Mimetic Control   |
            |          | |       Plugin        | ||        Plugin        |
            |          | |+--------+ +--------+| || +--------+ +--------+|
            |          | ||Schedule| |Decision|| || |Schedule| |Decision||
            |          | || Module | | Module || || | Module | | Module ||
            |          | |+--------+ +--------+| || +--------+ +--------+|
            |          | +=====================+ |+======================+
            |          |   |     |               |  |        |
            |          |   |     |               |  |        |
            |          |   | +-------------+     |  |  +--------------+
            |          |   | |Heterogeneous|     |  |  |Heterogeneous |
            |          |   | | SF Executive|     |  |  | SF Executive |
            |          |   | |    Pool     |     |  |  |    Pool      |
            |          |   | +-------------+     |  |  +--------------+
            |          |   |     |               |  |    |
            |          |   |     |               |  |    |
+-----+ +----------+  +-----------+       +----------------+  +------+
|Users|-|Classifier|--|    SFF1   | ......|      SFFn      |--|Target|
+-----+ +----------+  +-----------+       +----------------+  +------+
              Figure 1: SFC Mimicry Defense Architecture

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   The detailed system architecture is shown in Figure 1.  For a better
   understanding, it is assumed that the system has a single SFC
   (including the host, SFF, SF, and independent servers with other
   modules, each SF connected to an SFF) and a single control plane.
   The system architecture contains 05 components as follows:

   Control plane defines the SFC in the network.  The control plane
   installs the flow rules in the SFF, and delivers the classification
   strategy to the classifier based on the information uploaded by the
   classifier.  According to the judgment result, the abnormal SF
   executor is cleaned and be offline, and the next SFF in the SFC is
   notified that data is coming when the data passes through the SFF.

   Mimic control plug-in: composed of 02 modules.

   a.  Scheduling module: accept the running instruction of the control
       plane, select N SF executives from the SF executive pool to
       activate by using the scheduling algorithm.

   b.  Judgment module: Judge the execution result of the SF executive
       body, and randomly select one from the correct results and send
       it to the SFF.  If an abnormal SF executor is judged, the
       abnormal information will be transmitted to the control plane.

   SF executive body pool: it consists of M heterogeneous SF executive
   bodies, and N of them are activated by the scheduling module every
   time when data passes.

   SFF: forward the data according to the NSH information, copy the
   packet into N copies and send the information to activate the
   scheduling module.

   Classifier: send the packet information to the control plane, and add
   the corresponding NSH to the packet according to the classification
   strategy issued by the control plane.

4.3.  Data Flow

   +-----+  +----------+  +----+     +----+       +----+        +------+
   |Users|--|Classifier|--|SFF1|-----|SFF2| ......|SFFn|--------|Target|
   +-----+  +----------+  +----+     +----+       +----+        +------+
                             |          |           |
                             |          |           |
                          +-----+    +-----+     +-----+
                          | SF1 |    | SF2 |     | SFn |
                          +-----+    +-----+     +-----+
                            Figure 2: SFC Use Case

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   Take the SFC in Figure 2 as an example, we assume that the packet
   path is the source host-classifier-SFF1-SF1-SFF1-SFF2-SF2 ...- target
   host.  The data first reaches the classifier before entering the SFC
   domain, and the classifier sends the data information to the control
   plane.  The controller sends a classification strategy to the
   classifier based on the uploaded information, then the classifier
   adds NSH to the data packet according to the strategy and forwards
   the data packet to SFF1 based on the header information.  When the
   data arrives at SFF1, we need to judge whether the data packet needs
   to go through SF1 according to the NSH of the data packet.

   When the packet reaches SFF1 for the first time, it should be
   forwarded to SF.  Therefore, SFF1 first sends a running instruction
   to the scheduling module.  After the scheduling module receives the
   instruction, it uses a scheduling algorithm to select N activations
   from the SF executive pool.  Then, the information for activating the
   SF actuator is forwarded to SFF1.  SFF1 copies the packet into N
   copies and sends the data to N SF actuators according to the
   information provided by the scheduling module.  Each SF performs its
   designated network function and sends the execution result to the
   decision module.  After the judgment module accepts the execution
   result, it judges whether there is an abnormal SF executive body by
   using a judgment algorithm.  If there is an abnormal execution body,
   the abnormal information is sent to the control plane, and the
   abnormal SF will be cleaned and offline by the control plane, then
   the decision module selects one from the correct results and sends it
   to SFF1.  If there is no abnormal execution body, it will directly
   select one from the correct results and send it to SFF1.  SFF1 judges
   whether to forward to SF1 according to the NSH of the returned

   In this case, the packet should be forwarded to SFF2.  After the
   packet reaches SFF2, the same judgment and operation are performed
   until it leaves the SFC domain.

4.4.  Analysis of Attack and Defense

   The SF executive pool is the foundation of the security of this
   framework.  By configuring M heterogeneous SF execution bodies to
   form an SF execution body pool and using a scheduling algorithm to
   select N activation methods from the M SF execution bodies to improve
   the heterogeneity and dynamicity of the architecture, which increases
   the difficulty of the hacker's attacks.  Assuming that the packet
   path is the source host-classifier-SFF1-SF1-SFF1-SFF2-SF2 ...- target
   host.  For a traditional SFC, if a hacker hijacks SF1, it can
   manipulate SF1 to tamper with NSH so that traffic cannot reach SFF2.
   Furthermore, if the attacker intercepts the mapping table of SFF2,
   the hacker can tamper with the NSH header to make the traffic go

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   through a completely different SFC link.  Any device in the SFC
   domain, including the controller, will not find any abnormalities.  A
   hacker can also directly tamper with the service functions of SF, for
   instance, the original SF performs load-balancing function.  The
   hacker can tamper with all the data to the same link, which may
   paralyze the entire link.

   If the security framework of this document is adopted, first, during
   the SF attack detection phase, the hacker will find that there are M
   SFs with the same function but different operating environments and
   hardware devices mounted under the same SFF, which has caused certain
   difficulty for the attack.  If the hacker successfully controls one
   SF executive in the M SF executive pool under SFF2.  Before the data
   is forwarded from the control module to the SF executive body, the
   scheduling module uses a scheduling algorithm to activate N of the M
   SF executive bodies.  When M and N differ greatly, the probability of
   selecting an abnormal SF execution body by random scheduling is
   extremely low.  It is further assumed that even if an abnormal
   executor is selected, no matter whether the attacker tampers with the
   packet or data function in the controlled SF executor, the decision
   module can judge the exception when it judges the N execution
   results, it can select the correct result and send abnormal
   information to the control module for offline processing.  Unless the
   hacker successfully attacks more than half of the SF execution
   bodies, the attack can be completely successful.  While development
   vendors and hardware equipment are different in different SFs
   operating environment, which will cause great difficulty to the

   In another case, after the packet arrives at SFF1, it is not
   forwarded to SF to complete the specified function but directly
   forwarded to SFF2.  When the packet arrives at SFF2, SFF2 will infer
   from the NSH's SPI and SI information that the packet do not pass the
   specified function in the previous SFF, and then report an error to
   the control plane.

5.  Acknowledgements

   Thanks to Lei Rui and Chen Zebin for the first draft.

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

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   [RFC8300]  Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
              "Network Service Header (NSH)", RFC 8300,
              DOI 10.17487/RFC8300, January 2018,

6.2.  Informative References

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,

Authors' Addresses

   Chuanhuang Li
   Zhejiang Gongshang University
   18 Xuezheng Str., Xiasha University Town
   Hangzhou  310018

   Phone: +86 571 28877723
   Email: chuanhuang_li@zjsu.edu.cn

   Zhongyun Tang
   Zhejiang Gongshang University
   18 Xuezheng Str., Xiasha University Town
   Hangzhou  310018

   Phone: +86 571 28877723
   Email: tangzy@zjsu.edu.cn

   Chao Chen
   Zhejiang Gongshang University
   18 Xuezheng Str., Xiasha University Town
   Hangzhou  310018

   Phone: +86 571 28877723
   Email: eckio_491@zjgsu.edu.cn

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