The Complete Guide to SBOM (Software Bill of Materials)

Eran Orzel
Jan 27 · 9 min read

Developers using third-party and community-built products is routine practice with vulnerabilities stemming from these tools becoming a growing concern. To mitigate the issue, one critical practice is to tag open-source code with component information, usually termed as Software Bill of Materials (SBOM), which according to Forrester – especially in the wake of recent Log4J attacks – are becoming critical in importance.

Figure 1: Software supply chain is riddled with the flawed codebase

Imagine you have a craving for chocolate and reach an aisle of confectioneries at a supermarket, but you are lactose intolerant. You might see a couple of new chocolate bars among the different options of your favorite flavors and brands. The first thing you reasonably do is check the list of ingredients in the new bars, to see if there is anything that will set off your lactose intolerance. If milk products are a vulnerability, then the ingredients list helps you determine if milk products were used in its making.

The list of ingredients on food packages is very similar to the Software Bill of Materials for code. It tells you, as a developer or security engineer whether the software has any components that will harm your application development.

Read on to understand the significance of SBOMs in software development and maintenance.

What is Software Bill of Materials?

SBOM is nested metadata of all the components present in both proprietary and open-source software. It compromises component names, the relationship between the components within the supply chain, open-source licenses, and dependencies. SBOMs facilitate transparency and enable organizations in managing risks.

The 5 key applications of SBOMs are as follows:

  1. Identify vulnerable components within the software
  2. Standardize vulnerability check formats across sectors
  3. Detect suspicious or counterfeit software components
  4. Reduce time and effort consumed by supply chain risks
  5. Increase trust across the supply chain

The term ‘SBOM’ is derived from the traditional manufacturing industry where the Bill of Materials (BOM) is extensively used. It consists of systematic data of raw materials, components, and parts that go into the manufacturing of automobiles, electronics, and food products. BOMs help manufacturers identify, track, and resolve production challenges.

For example, if a batch of defective chips finds its way into the memory board of a computer, the manufacturer can easily remediate the issue. The BOMs will help the manufacturer identify which units used the defective chips. This mechanism works smoothly because every computer unit features the details of all the components fixed into it.

With the current software development ecosystem heavily dependent on third-party codebases – open-source and proprietary, SBOMs have gained wide popularity and relevance. It helps you visualize any underlying risks with respect to license compliance, security, and quality. This detailed insight into software supply chain vulnerabilities helps developers and security owners to quickly mitigate them.

The importance of SBOMs was further emphasized by the Federal Government of the US. A recent Executive Order requires ‘providing a purchaser a Software Bill of Materials (SBOM) for each product directly or by publishing it on a public website’ as a mandatory practice to enhance software supply chain security.

Benefits of SBOMs

1.    Improve productivity

You can eliminate the need for unplanned work to tackle vulnerabilities because SBOM will help you prioritize threats by bringing enhanced visibility into the codebase.

2.    Lower costs

You can greatly reduce time to mitigate security risks with an effective detection process. This saves not just time, but even the costs incurred due to these risks.

3.    Reduce code bloat

SBOMs allow you to identify duplicate or unnecessary components. These are usually vulnerable components that need to be managed. A secondary benefit of this is that it reduces code bloat.

4.    Understand dependencies

With SBOMs, you can easily analyze and manage dependencies within complex software. This improves the product’s overall quality.

5.    Detect vulnerabilities

When it comes to security, it’s important to know every part of the system. SBOM gives you a clear list of components that help in monitoring every part for vulnerabilities.

6.    Easy code review

As you can identify and eliminate vulnerabilities by tracking components from the early stages, reviewing code becomes much easier.

7.    Compliance

SBOMs contain details of license obligations and policy compliance, making it better for you to understand the limitations of using of any software.

8.    EoL Components

With easy End-of-Life management, you can make informed decisions on removing and replacing components that are nearing their end-of-life stage. This helps you steer clear of outdated components.

What does SBOM include?

SBOMs make it easier to identify, track and manage software components due to their systematic and universally agreed-upon structure. However, they don’t exist independently, and instead seek information from other entities. For example, an SBOM will require a vulnerabilities catalog for effective component management. And for license management, it’ll need licenses and associated restrictions of a component.

As per the National Telecommunications and Information Administration (NTIA), SBOMs must include seven necessary and minimum data fields to effectively track components across the supply chain to mitigate risks.

7 Baseline attributes every SBOM must include

Figure 2: Elements of SBOM

1. Author:

The person or an organization that drafts the metadata. Although not necessary, the author is usually the supplier of the software component.

2. Component:

The name of the software component, which is usually given by the supplier. It will also include multiple names, if any, of the component. It is mentioned in namespace: name syntax.

3. Component relationship:

A description of how two or more components are related. It is either described using the relationship type ‘includes’ or ‘included in.’ It is common for components to be related across the supply chain.

4. Component hash:

For easy identification of a component, it is defined by a unique cryptographic hash. This is to identify the precise and unmodified version of the component.

5. Supplier:

Indicates the name of the person or the organization that owns or has supplied the software component.

6. Unique identifier:

Unique identifiers help you in determining components in key databases. Some identifiers are Software Identification (SWID) Tags and Common Platform Enumeration (CPE).

7. Version string:

This defines the version of the software and is often given by the supplier.

Purpose and application of SBOMs

With extensive use of open-source and third-party software blocks, commercial software development lacks transparency. This leads to cybersecurity threats, code tampering, and other malicious activities. SBOM’s significance was highlighted in the US government’s executive order calling for strict measures for cybersecurity. However, it holds massive benefits for enterprises, not just in terms of security but also to enable seamless business processes.

Maximized customer data security

SBOMs empower you to provide highly secure products and services to your customers. They also identify software flaws and disclose the details to you, ensuring high transparency. This is especially critical in industries such as healthcare and defense. Cybercriminals could exploit these vulnerabilities to expose or seize confidential data.

Increased ROI

SBOMs proactively expose risks and compromising aspects of third-party codebases. This helps you avoid heavy costs incurred due to security breaches, a bad reputation, and regulatory penalties. Over time, SBOMs will prove to be a golden investment in cybersecurity with significant returns in terms of reduced operational costs, improved productivity, and effective compliance.

Improved policy compliance

SBOMs include information regarding licensing and policy compliance. Going through this nested inventory will ensure you don’t overlook any strict licensing requirements. For example, a supplier could include clauses of author attribution when using their software. This mandate will be included with the SBOM documentation and knowing this information could save you serious litigation costs.

Applications

Figure 3: Applications of SBOM in securing the software supply chain

Primarily, SBOMs exist to track and manage components and their relationships in the software supply chain to ensure a secure software ecosystem. However, their applications go beyond that. These applications can be clubbed into three core categories:

1. Vulnerability Management:

SBOMs don’t just help you with a swift and accurate assessment of software vulnerability, but also provide additional information. They seek data from Common Vulnerabilities & Exposures (CVE) and National Vulnerability Database (NVD) to help you detect and exploit a vulnerable component’s downstream relation.

2. Safeguard Intellectual Property:

Besides giving you details of the components, SBOMs also provide software licensing details to disclose redistribution constraints, attribution requirements, and other compliance policies. It is a widely used niche application of SBOMs. Some DevSeCOps tools are designed specifically to extract such licensing details. The industry standards Software Package Data eXchange (SPDX) and Software Identification (SWID) were developed for this application.

3. Component Integrity Management:

SBOMs constantly verify the integrity of components through the data fields it is fed. Information related to the supplier, component relationship, and version string enables SBOMs to effectively manage the quality of components.

SBOM: Creation & Management

Suppliers, who are essentially an individual or an entity creating, modifying, and delivering software, are tasked with creating an SBOM. They define the SBOM with basic component information as a part of their software build. It is mandatory for suppliers to mention identifiable aspects of components while describing the characteristics of the components is optional. Data given by the supplier is considered the authentic source of information of a component. However, some components might need information from external sources like CVEs (​​Common Vulnerabilities and Exposures).

A new SBOM can be created and published in various formats including HTML, CSV, PDF, Markdown, and plain text. The three commonly used formats of SBOMs are Software Package Data Exchange (SPDX), Software Identification (SWID) Tags, and Cyclone DX.

Figure 4: Three commonly used formats of SBOM

SPDX

Also known as ISO/IEC 5962:2021, SPDX is spearheaded by The Linux Foundation. It is an open standard for describing SBOM information related to provenance, licensing, and security.

SWID Tags

This format identifies and reports software components in XML format under four categories across the development lifecycle:

  • Corpus Tags: Identifies and describes components in a pre-installation stage.
  • Primary Tags: Identifies and describes components in a post-installation stage.
  • Patch Tags: Identifies and describes the patch.
  • Supplement Tags: Allows only the tag creator to modify corpus, primary, and patch tags.

Cyclone DX

Managed by Cyclone DX’s core working group, it is designed for application security contexts. Cyclone DX is considered a lightweight standard with features of both SPDX and SWID. It includes four data fields:

  • BOM Metadata: Description of the supplier, manufacturer, component, and compilation tools.
  • Components: Complete information of a proprietary and open-source components along with licensing requirements.
  • Services: A list of external APIs that the software may invoke.
  • Dependencies: All forms of relationship within the supply chain.

SBOMs: Road ahead

Although SBOMs help in detecting and managing flawed components during the early stages, they suffer from a few limitations.

Vendor-generated SBOMs:

As vendors and suppliers generate SBOMs, we need to trust and depend on the information they provide. Intentional or unintentional gaps in the data provided could result in a nasty jolt.

Inconsistent SBOM standards:

Despite being well-structured, SBOMs often suffer from inconsistent naming conventions and incomparable formats.

Supply chain vulnerability:

SBOMs do not offer absolute protection against cyber risks as software flaws can be exploited much later.

Incomplete SBOM information:

Since it is not entirely regulated, vendors could choose to mention data they feel is crucial, and skip other parts. This incomplete SBOM leaves your software open to attacks.

Even with these limitations, your organization can successfully utilize SBOM methodology to detect and resolve vulnerabilities quickly. You can also employ tools to analyze a codebase across the deployment lifecycle of an application.

As a software security company and pioneer Argon is an innovative software supply chain security solution. Argon assigns a security score to components with every release after a rigorous review of components. This enables you to implement a strict security evaluation across CI/CD pipelines to effectively mitigate security threats.

Eran Orzel
Jan 27 · 9 min read

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