A software program invoice of supplies (SBOM) supplies transparency into the weather of an built-in software program product. Such transparency is vital to figuring out system vulnerabilities and thus mitigating potential safety dangers. There’s rising curiosity in utilizing SBOMs to assist software program provide chain danger administration. In September 2024 Military leaders signed a memorandum requiring SBOMs for vendor-supplied software program. Extra not too long ago, the Division of Protection (DoD) Chief Info Officer, by means of its Software program Quick Observe Program, is requiring that software program distributors submit their SBOMs, in addition to these from third-party assessors, to allow detection of variances between SBOMs for a similar software program.
Totally different SBOM instruments ought to produce comparable data for a bit of software program at a given level in its lifecycle, however this isn’t at all times the case. The divergence of SBOMs for particular person items of software program can undermine confidence in these essential paperwork for software program high quality and safety. This weblog publish outlines our group’s current findings on why SBOMs diverge and recommends seven methods to enhance SBOM accuracy.
SBOM Harmonization Plugfest
The SEI’s 2024 SBOM Harmonization Plugfest challenge, sponsored by the Cybersecurity and Infrastructure Safety Company (CISA), aimed to uncover the basis causes of SBOM divergence, equivalent to imprecise definitions or requirements, how uncertainty is addressed, or different implementation choices. The SEI introduced collectively SBOM device distributors, requirements producers, and others within the SBOM group to supply pattern SBOMs for evaluation. The not too long ago launched Software program Invoice of Supplies (SBOM) Harmonization Plugfest 2024, on which this publish is predicated, outlines our group’s findings, evaluation, and proposals to assist SBOM producers generate extra constant and dependable SBOMs.
We requested Plugfest contributors to generate and submit SBOMs primarily based on 9 software program targets chosen as a consultant pattern of varied programming languages as seen in Desk 1 beneath.
The SEI gained approval from most contributors to make their submissions public. These SBOMs that had been authorized for launch are now obtainable at SEI’s GitHub web site.
Overview and Evaluation of Submitted SBOMs
We obtained 243 SBOMs from 21 Plugfest contributors. To make sure anonymity and to stop any bias in our assessment, we anonymized participant names by assigning alphanumeric codes to every. One participant, who was assigned the code Y2, submitted many extra SBOMs (102) than all of the others (Determine 1). Y2 generated and submitted SBOMs in each format their device supported (i.e., supply and binary evaluation in addition to enriched and non-enriched).
Determine 1: SBOMs Submitted per Goal
Evaluation
To make sure an goal evaluation, we first decided analysis standards for our assessment of the SBOMs. We then decided automated approaches to extract info from the SBOMs to facilitate our improvement of software program instruments for evaluation in addition to our era of baseline SBOMs, which we used for comparability functions.
Analysis Standards
Assessing the consistency of the minimal components of the submitted SBOMs was a vital element in figuring out their completeness and accuracy. A listing of minimal components specifies the baseline SBOMs ought to meet and facilitates info sharing. The standards we used for minimal components are these required for documenting a software program product’s main element and its included parts as outlined in CISA’s Framing Software program Element Transparency: Establishing a Widespread Software program Invoice of Supplies (SBOM):
- SBOM Writer Identify
- SBOM Timestamp
- SBOM Kind
- SBOM Main Element
- Element Identify
- Element Model String
- Element Provider Identify
- Element Cryptographic Hash
- Element Distinctive Identifier
- Element Relationships
- Element License
- Element Copyright Holder
Evaluation Instruments
Because of the many submissions, we developed instruments to automate ingesting and processing SBOMs to gather, collate, and export information about them. Members submitted SBOMs in SPDX and CycloneDX codecs in a wide range of encodings together with JSON, XML, and YML.
We wrote code for processing SBOMs utilizing Python inside Jupyter computational notebooks hosted on an SEI inner Bitbucket repository, which additionally contained a duplicate of SBOM Plugfest submissions. We used two main notebooks for analyzing SBOM submissions: one for CycloneDX and one for SPDX. We sought to extract the next from every SBOM:
- info associated to the presence or absence of minimal components
- details about software program parts, together with their relationships to at least one one other and with the goal software program
In every pocket book, we collected info from every SBOM by doing the next:
- traversing the listing of SBOM submissions, importing JSON SBOM recordsdata, and decoding the JSON recordsdata in order that information might be extracted
- extracting minimal components from every SBOM the place the info existed and noting the place information was lacking
- setting up a dependency tree primarily based on the dependencies listed in every SBOM (These dependency timber contained details about software program parts and the sorts of relationships amongst these parts as listed within the SBOM.)
- collating information from every SBOM into two frequent information constructions: one for info associated to minimal components and the opposite for element info
We analyzed the info constructions utilizing Python information science packages, or we exported them as comma separated worth (CSV) recordsdata for additional evaluation. We used details about the presence or absence of minimal components to generate abstract statistics for every software program goal and every SBOM sort (supply/construct). We used dependency graph info to investigate the presence/absence of parts and assess the depth of the SBOMs.
Baseline SBOMs
We chosen three outstanding open supply instruments, Syft, Trivy, and Microsoft’s SBOM Device, to create baseline SBOMs for every of the 9 software program targets. The baseline SBOMs served as preliminary examples of what we would count on to see submitted by Plugfest contributors. The baseline SBOMs additionally allowed us to develop evaluation instruments early within the challenge so we might begin analyzing contributors’ SBOMs as quickly as they had been submitted.
Findings from SBOM Evaluation
The next are notable findings from our analysis on the SBOMs submitted for the Plugfest. These findings, ordered from the trivial to the extra advanced, clarify the sorts of variances within the SBOMs in addition to their causes.
- Element quantity, content material, and normalization. We discovered vital variance in each the variety of parts and the content material of the minimal required components in SBOMs from completely different contributors for a similar software program on the identical lifecycle section. Some variance in SBOM content material is because of the lack of normalization; the identical content material was merely being written in another way (e.g., software program model detailed as v 2.0 or simply 2.0).
- Software program variations. One other trigger for variance in SBOM content material is that some software program specs permit for a variety of potential software program variations, however SBOMs permit solely a single model to be documented for every dependency. This leads to SBOMs having numerous variations listed throughout completely different contributors for every goal that allowed model ranges.
- Minimal components. Some variance in SBOM content material is because of variations in whether or not contributors included minimal components or not, which can be because of the considerably synthetic nature of producing SBOMs for a analysis challenge.
- Use circumstances. SBOMs have various use circumstances, which result in various kinds of SBOMs. The big variety of potential use circumstances is an extra trigger for the dearth of harmonization throughout SBOMs for a similar goal. If we had specified a use case, contributors might have taken a extra harmonized method to how they generated, enriched, or augmented their SBOMs for that use case.
- Construct and supply SBOMs. Members used completely different approaches to generate their construct and supply SBOMs, which led to variations within the found parts. Some contributors used a container construct course of to generate their construct SBOM, and others constructed a standalone executable for his or her chosen runtime atmosphere utilizing the goal’s language or build-framework-specific course of. Construct SBOMs additionally different primarily based on the atmosphere and power configurations every participant used. Supply SBOMs seize dependencies declared or inferred from supply code. Some contributors used extra info from exterior places, such because the artifact repositories referenced by dependencies or the contents of platform toolchain libraries, to deduce extra dependencies.
- Dependency interpretation. A assessment of submitted explanatory readme recordsdata and discussions with contributors indicated some variations within the interpretation of dependency. Some submissions included dependencies of first-party parts that aren’t sometimes deployed, equivalent to goal documentation construct instruments, CI/CD pipeline parts, and optionally available language bindings.
7 Suggestions for Enhancing SBOM High quality
The next suggestions primarily based on our analysis and evaluation will enhance the standard of SBOMs and assist guarantee constant content material in SBOMs for a similar goal.
-
Emphasize inclusion of the next minimal components:-
SBOM Kind.
Embody the SBOM Kind to doc the lifecycle section for which this SBOM was generated (e.g., Supply, Construct). We suggest that this attribute be required relatively than optionally available. -
Element Model String.
Emphasize the significance of reporting the model precisely as supplied by the provider. This reporting minimizes the necessity for normalization attributable to information being inconsistently reported (e.g., one SBOM stories
v 2.0
and one other stories
2.0
). -
Element Provider Identify.
Embody the title of the entity that supplied the contents of the software program being described. This helps customers of the SBOM perceive which third events had been a part of the provision chain. A standard registry of element suppliers would assist normalize this entry. For open supply software program parts, which wouldn’t have a standard provider, a direct reference or hyperlink to the challenge repository ought to be supplied. -
Element Cryptographic Hash.
SBOM steerage ought to clearly state what parts are being hashed when a cryptographic hash is included. Make it extra easy for SBOM customers to know how you can confirm the hash worth. Alternatively, when supplying cryptographic hashes, SBOM creators ought to be specific about what was hashed. -
Element License.
Emphasize the necessity to present licensing info or to notice that the license info just isn’t identified or was not included.
-
-
Enhance normalization of SBOM components.
A lot divergence in SBOMs is because of lack of normalization (e.g., model numbering as talked about earlier or
date/time
which can be written as 2025-06-15 or just as August 2025). Standardize on utilizing the time period
provider
for a
main provider
and the time period
producer
for a
secondary provider
. -
Doc how the time period
dependencies
is interpreted within the SBOM era course of.
Develop steerage to tell apart dependencies by class (e.g., runtime, assessments, docs). -
SBOM mills ought to doc their method to producing SBOMs.
It will assist customers higher perceive potential variations in SBOMs for a similar software program. Additionally doc the use case for which the SBOM is being generated. Totally different use circumstances might require variations in SBOMs. -
Use the suitable device for the atmosphere.
SBOM creators and customers ought to guarantee they’re utilizing an applicable SBOM device for his or her particular atmosphere. SBOM instruments sometimes deal with a subset of the programming languages and construct environments. -
Help developer group SBOM efforts.
Some developer communities are working to incorporate SBOM mills in language instruments and construct frameworks to make it a lot simpler for initiatives utilizing these languages and frameworks to generate SBOMs as upstream suppliers. These efforts have an outsize impression as a result of they decrease the barrier for creating SBOMs and push the SBOM era additional upstream to challenge maintainers who’ve detailed information of their very own supply code and construct processes. -
Develop and validate SBOM profiles.
To assist stakeholders talk extra successfully, they may develop and validate SBOM profiles, every profile being a well-defined restriction positioned on a number of SBOM requirements to make clear which means and allowable values for every discipline, its cardinality, and structural facets. The
OWASP Software program Element Verifications Commonplace (SCVS) BOM Maturity Mannequin
profiles characteristic is an instance. One other method could be to outline a JSON schema that extends the present schemas for CycloneDX and/or SPDX and provides the required clarifications and restrictions for a profile.
Future Work on Guaranteeing SBOM High quality
SBOMs are of rising significance to safeguarding the safety of all software program methods, together with DoD and important infrastructure methods. As extra organizations require use of SBOMs, there shall be better want to make sure their high quality and completeness, together with offering transparency for undeclared dependencies. Selections to maintain SBOM components opaque could also be rethought if third social gathering SBOMs can present wanted transparency. This analysis challenge is a part of a unbroken SEI effort to enhance the standard of SBOMs.
