By: Prashant Sharma
November 2, 2020
Reverse Engineering: Everything You Need To Know
By: Prashant Sharma
November 2, 2020
Over the past hundreds of years, we have witnessed a drastic change in products and technology. Due to continuous advancement in technology, we have seen many products remain as relevant as they were years ago. However, the case is not the same for all the products. As time progresses, many products malfunction, and some even break down completely. We then replace that one malfunctioning part of a product, and we get the working device again. This is all possible because of Reverse Engineering.
As the name implies, Reverse Engineering (also called back engineering) is a process in which an object is deconstructed to extract the designs, architectures, code, or crucial information. It is a process that allows analyzing the core constituent components of any existing product to replicate the design or design knowledge, then creating an exact functioning product.
Engineering is what happens when we have specifications, then code or draw up a design that ends up re-creating a final product that functions as per the specifications. Conversely, Reverse Engineering is when we have the final product, analyzes the working functions through product behavior or codes, and end up with specifications. We can finalize here that Reverse Engineering begins by having a final product and processing in the opposite direction to get specifications. Reverse Engineering can be performed on both hardware and software levels, leaving us with two different kinds of Reverse Engineering. We are going to cover only Software Reverse Engineering in this article.
Software Reverse Engineering
In the context of software engineering, Reverse Engineering is the process that involves taking a software system, converting its machine language into a programming language like Java or C, analyzing it to trace it back to the original design, then implementing information. We are bound to convert machine language because it's in binary form, not user-friendly, while programming language is easy to understand, making it easily studied. There were four basics to evaluate the software in the past: functionality, cost, vendor stability, and the attractiveness of the user interface. A fifth base is added when Reverse Engineering comes into the picture: quality. We can estimate how well the application, database, or software has been designed and conceived. Aside from the quality, there are several other additional benefits of Reverse Engineering:
- Understanding: Few vendors provide products to help understand the applications. However, there may be some glitch in your contract or other processes that, somehow, make one able to purchase that product again. Existing products can help one understand both the scope and the content of a vendor product. One can use Reverse Engineering to check what has been served in the past, making it possible to construct your product on the same basis. However, copying the code is not what we intended with Reverse Engineering. It is more likely to take the inspiration and re-build with its strategy.
- Negotiation: It is human nature to emphasize strengths over weakness. The same thing can be done with your vendors. Point out the weaknesses with Reverse Engineering, giving better hands-on negotiations.
- Communication: While the vendors may have their assumptions, architecture, terminologies, and mindset, which provide a context for their explanation of an application, if you are not familiar with their context, you will not understand a word of what they mean. Here, Reverse Engineering comes to the rescue so that you can get into their minds and converse with their terminologies.
- Data Conversion: There must be some legacy data that migrates to the vendor product. You need to understand the source of the target before converting the vendor's data.
Based on source code presence, there are two forms of Software Reverse Engineering. In the first case, source code is already available. Still, higher-level aspects of the program may be poorly documented or documented in such a way that it is no longer valid or available. Therefore, we can conclude that no efforts are needed to find the source code in this case. In the second case, neither source code nor higher-level aspects are available. Extra efforts are required to determine the software's possible source code, which is considered Reverse Engineering.
Purposes of Software Reverse Engineering
From the above paragraphs, we can summarize that a third party generally performs Reverse Engineering with no hand in writing the original code. With the help of Reverse Engineering, the reverser (who performs Reverse Engineering) serves the following purposes:
- Security auditing
- Understanding underlying source code for maintenance and improvements
- Extracting relevant information for debugging
- Detection and fixing a software bug or system vulnerability
- Recovering extinct design information
- Cracking (removal of copy protection)
- Enabling additional features
- Reducing the time and overall cost of software development
- Detect and eliminate malicious codes using code detectors
- Finding the alternate use of existing source code
- Revealing how a competitor's product is built
- Finding vulnerabilities in the operating system to build computer virus
- Cryptanalysis (finding vulnerabilities in a substitution cipher, symmetric-key algorithm, or public-key cryptography)
- Analyzing the complexity of core software algorithms
- Researching malware and viruses
- Testing and quality management of software
- Further development of software
- Investigation of network communication protocols
- Moving or maintenance of programs which is abounded
- Use of undocumented platform functions
- Mere satisfaction of curiosity
Apart from this, Reverse Engineering has two other major components, namely, Re-Documentation and Design Recovery. Re-Documentation is the process of creating documents again. But here, it signifies creating new representations of user-friendly computer code that are easier to analyze. Design Recovery is the term for analyzing and understanding the products from general knowledge or personal usage, without looking at the source code.
Steps to perform Software Reverse Engineering
- Collection Information:__ As per the name, this step is concentrated on collecting all possible information about the software like source design documents, code information, strategic documentation, etc.
- Examining the information:__ In this step, the collected information needs to be studied and examined to understand the system specifications fully.
- Extracting the structure:__ In this step, the program structure is identified in the form of a structure chart. In this structure chart, each node corresponds to some routine.
- Recording the functionality:__ This step involves the processing details of each module of the structure. In this step, charts are recorded using structured language like decision tables, etc.
- Recording data flow:__ Now that all of the information has been collected and functionality has been recorded, the next step is where a set of data flow diagrams are derived to show the flow of data among the processes.
- Recording control flow:__ After recording data flow, a high-level control structure of the software is recorded.
- Review extracted design:__ In this step, the design document is prepared as per the recorded data. This document needs to be reviewed several times to ensure consistency and correctness. This design represents the program.
- Generate documentation:__ In this final step, Documentation is recorded for future use. These documents include SRS, design document, overview, history, etc.
Software Reverse Engineering in different areas
Product and Process Improvement Many software developers use Reverse Engineering to improve their existing programs or improve interoperability between programs. With this, they can easily determine the vulnerabilities of the program and fix them before exploitation. Some software suites in the market consist of application programming interfaces (APIs), which can allow program interoperability. But there can be a problem with such software suites: the APIs are not well written. For this reason, developers prefer Reverse Engineering over software suites, just to ensure compatibility.
Cybersecurity Reverse Engineering is the most common practice for companies that develop security software. By Reverse Engineering and studying viruses or other malware, they can develop tools to combat the techniques used by malware or virus developers. This reduces the man-force and time used for reactively developing defenses for individual malware programs. Security experts use this process to find the security flaws in software and understand how hard it is to hack the software, while hackers use it to find gaps in security to exploit them. Reverse Engineering is a boon for developers involved in researching client issues, working in a wide range of data formats and protocols, and ensuring the code's compatibility with third-party software.
Intelligence and Espionage With the continuous evolution of technologies and developments, almost everyone relies on computer systems for warfare, commerce, and more. Along with it, systems are more vulnerable to those who are keeping an eye on exploiting systems. These hackers reverse-engineer systems to inject malware or viruses in an attempt to fetch crucial data. They can also perform reverse-engineering to spy on you by manipulating the source code of any program.
Things to keep in mind while performing Reverse Engineering:
- Don't mistake hypotheses for conclusions. Reverse Engineering can distract you with hypotheses. Don't jump to conclusions based on limited pieces of evidence. Go through the entire process and fully understand the application or software before reaching firm conclusions.
- Expect multiple interpretations. Since a piece of code can function differently from another program, there will be several assumptions when performing Reverse Engineering. A single wrong interpretation can lead to an entirely different model. Learn to look for all of the possibilities; more information, fewer judgments should vary among reversers.
- Don't be discouraged by approximate results. Reverse Engineering is time-consuming. Don't settle for the less. It is worth a considerable amount of time if you have already extracted 80 percent of an existing program. You can also approach knowledgeable users to understand the program better. This is one of the forward engineering techniques which will help analyze the remaining part of the program.
- Expect odd constructs. Software designers or programmers, even the experts, occasionally use uncommon constructs, which is enough to make one uneasy about the program. There may be a chance of misdirection or the inability to produce a complete and accurate model because that model never existed.
- Watch for a consistent style. Many programs have a significant and consistent strategy, so don't be fooled by extra underlying codes. Stick to the consistent strategy, and you will be able to trace the exact program strategy.
Reverse Engineering Tools
The time-consuming aspects of Reverse Engineering can be compensated with the help of certain tools. These tools that make this tedious process easier are mentioned below:
- Disassemblers: Disassemblers are used to convert binary codes into assembly code. We can also say that disassemblers help in converting machine language into a more user-friendly one. There are various disassemblers in the market used for different purposes. One such tool is Decompilers, which convert binary code into the native language (restricted to some architecture).
Example: IDA Pro, Binary Ninja, DEBUG, Interactive disassemblers (IDA), Hiew.
- Debuggers: Debuggers can look into the program, what the program is, and how it is impacting a system or network. They are used in analyzing the binary code as disassemblers do. Debuggers give specific controls for looking through the code by running a line at a time. Due to this, reversers can set breakpoints as well as edit assembly codes at run time. It allows expanding the functionality by supporting the CPU registers, hex dumping of programs, and the stack's view, among other things.
Example: x64dbg, Windbg, GDB
- Hex Editors: Hex is an abbreviation for Hexadecimal, a standard numerical format for representing binary data. Hence, Hex editors are also known as binary file editors or byte editors. They are used to see, analyze, or edit raw and exact contents of a file. A hex editor is a computer program that allows correcting or fixing the data corrupted by a system or application.
Example: HxD, 010 editor, beye, bvi, Cheat Engine, FlexHex.
- PE and Resource Viewer: PE and Resource Viewers allow extracting important information from executables files and editing them. They make it easy to edit information like icons, edit menu, version information, dialog, etc. PE explorer allows translating the applications that don't have source codes. This can be easily done by replacing the text resources with their translated versions, then resizing buttons, forms, etc.
Example: CFF Explorer, PE Explorer, PEView, FileAlyzer, PEstudio, Exeinfo PE, PE insider.
- Network Analyzers: A network analyzer helps run an efficient and optimized network by discovering performance issues before they affect the whole network. It decodes the data passing through the network and displays it in a format that is readable. It performs several tasks like troubleshooting network problems, determining WiFi availability and speeds, searching for bandwidth, detecting network intrusion or spyware, locating DDoS attack, and discovering faulty applications.
Example: Wireshark, Network Performance Monitor, Netflow traffic Analyzer, WiFi Analyzer, NetSpot.
Laws associated with Reverse Engineering
Generally, the software is too costly, comes with uneven quality, and requires a long time to deliver. In such cases, Reverse Engineering is of no harm and quite reliable as compared to the vendor's product. Now, imagine a situation where everyone is reverse-engineering the products to have the benefits of the products. How much pressure will be on vendors who are spending so much on production costs? But again, this is not as easy as a lookalike. Earlier, we discussed that it's not easy to trace the exact working models through Reverse Engineering. In another scenario, competitors will also want to exploit software for their business or strategy theft. For preventing such discoveries, there are a few international laws that allow vendors to put restrictions on Reverse Engineering on their products. These laws include:
- Patent Law: prevent competitors from copying the invention through Reverse Engineering or from other ways.
- Copyright Law: allows protection for software and programs from both direct copying and close paraphrasing. The only copyright owner has exclusive rights to reproduction and distribution of protected work.
- Digital Millennium Copyright Act (DMCA): allows Reverse Engineering only to create or improve software interoperability.
From the discussion above, we can conclude that Reverse Engineering is an essential part of evolving technology. It helps one to look inside a product and discover the hidden strengths and weaknesses. Only Reverse Engineering lets one determine the intrinsic quality of a product. Based on how it is used, Reverse Engineering can be a boon or taboo for reverse engineers. It is also a tough process to find out the exact match of existing models even though this is the only process that lets one deep-dive into the quality of products and detection and fixing of vulnerabilities.
Author – Prashant Sharma (https://www.linkedin.com/in/prashantique/)