A software program invoice of supplies (SBOM) gives 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 may be rising curiosity in utilizing SBOMs to help 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, via its Software program Quick Monitor 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.
Completely different SBOM instruments ought to produce comparable data for a chunk 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 vital paperwork for software program high quality and safety. This weblog publish outlines our crew’s latest findings on why SBOMs diverge and recommends seven methods to enhance SBOM accuracy.
SBOM Harmonization Plugfest
The SEI’s 2024 SBOM Harmonization Plugfest undertaking, sponsored by the Cybersecurity and Infrastructure Safety Company (CISA), aimed to uncover the foundation causes of SBOM divergence, resembling 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 neighborhood 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 crew’s findings, evaluation, and proposals to assist SBOM producers generate extra constant and dependable SBOMs.
We requested Plugfest members to generate and submit SBOMs based mostly on 9 software program targets chosen as a consultant pattern of varied programming languages as seen in Desk 1 under.
The SEI gained approval from most members to make their submissions public. These SBOMs that had been authorised for launch are now accessible at SEI’s GitHub web site.
Overview and Evaluation of Submitted SBOMs
We acquired 243 SBOMs from 21 Plugfest members. To make sure anonymity and to stop any bias in our overview, 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 overview of the SBOMs. We then decided automated approaches to extract data 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 part in figuring out their completeness and accuracy. An inventory of minimal components specifies the baseline SBOMs ought to meet and facilitates data sharing. The standards we used for minimal components are these required for documenting a software program product’s main part and its included parts as outlined in CISA’s Framing Software program Part Transparency: Establishing a Frequent Software program Invoice of Supplies (SBOM):
- SBOM Creator Title
- SBOM Timestamp
- SBOM Sort
- SBOM Major Part
- Part Title
- Part Model String
- Part Provider Title
- Part Cryptographic Hash
- Part Distinctive Identifier
- Part Relationships
- Part License
- Part Copyright Holder
Evaluation Instruments
As a result of many submissions, we developed instruments to automate ingesting and processing SBOMs to gather, collate, and export knowledge about them. Individuals submitted SBOMs in SPDX and CycloneDX codecs in quite a lot 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 replica 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:
- data associated to the presence or absence of minimal components
- details about software program parts, together with their relationships to 1 one other and with the goal software program
In every pocket book, we collected data from every SBOM by doing the next:
- traversing the listing of SBOM submissions, importing JSON SBOM information, and decoding the JSON information in order that knowledge could possibly be extracted
- extracting minimal components from every SBOM the place the info existed and noting the place knowledge was lacking
- developing a dependency tree based mostly on the dependencies listed in every SBOM (These dependency timber contained details about software program parts and the varieties of relationships amongst these parts as listed within the SBOM.)
- collating knowledge from every SBOM into two frequent knowledge constructions: one for data associated to minimal components and the opposite for part data
We analyzed the info constructions utilizing Python knowledge science packages, or we exported them as comma separated worth (CSV) information 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 data to investigate the presence/absence of parts and assess the depth of the SBOMs.
Baseline SBOMs
We chosen three distinguished open supply instruments, Syft, Trivy, and Microsoft’s SBOM Software, to create baseline SBOMs for every of the 9 software program targets. The baseline SBOMs served as preliminary examples of what we’d anticipate to see submitted by Plugfest members. The baseline SBOMs additionally allowed us to develop evaluation instruments early within the undertaking so we might begin analyzing members’ 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 complicated, clarify the varieties of variances within the SBOMs in addition to their causes.
- Part 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 members for a similar software program on the identical lifecycle part. 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 varied variations listed throughout completely different members for every goal that allowed model ranges.
- Minimal components. Some variance in SBOM content material is because of variations in whether or not members included minimal components or not, which can be because of the considerably synthetic nature of producing SBOMs for a analysis undertaking.
- Use circumstances. SBOMs have various use circumstances, which result in several types of SBOMs. The wide range 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, members could have taken a extra harmonized strategy to how they generated, enriched, or augmented their SBOMs for that use case.
- Construct and supply SBOMs. Individuals used completely different approaches to generate their construct and supply SBOMs, which led to variations within the found parts. Some members 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 various based mostly on the atmosphere and gear configurations every participant used. Supply SBOMs seize dependencies declared or inferred from supply code. Some members used extra data from exterior areas, such because the artifact repositories referenced by dependencies or the contents of platform toolchain libraries, to deduce extra dependencies.
- Dependency interpretation. A overview of submitted explanatory readme information and discussions with members indicated some variations within the interpretation of dependency. Some submissions included dependencies of first-party parts that aren’t sometimes deployed, resembling goal documentation construct instruments, CI/CD pipeline parts, and elective language bindings.
7 Suggestions for Bettering SBOM High quality
The next suggestions based mostly 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 Sort.
Embrace the SBOM Sort to doc the lifecycle part for which this SBOM was generated (e.g., Supply, Construct). We advocate that this attribute be required reasonably than elective. -
Part Model String.
Emphasize the significance of reporting the model precisely as supplied by the provider. This reporting minimizes the necessity for normalization because of knowledge being inconsistently reported (e.g., one SBOM reviews
v 2.0
and one other reviews
2.0
). -
Part Provider Title.
Embrace the identify 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 availability chain. A typical registry of part suppliers would assist normalize this entry. For open supply software program parts, which do not need a conventional provider, a direct reference or hyperlink to the undertaking repository needs to be supplied. -
Part Cryptographic Hash.
SBOM steering ought to clearly state what parts are being hashed when a cryptographic hash is included. Make it extra easy for SBOM customers to know learn how to confirm the hash worth. Alternatively, when supplying cryptographic hashes, SBOM creators needs to be express about what was hashed. -
Part License.
Emphasize the necessity to present licensing data or to notice that the license data will not be 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 steering to tell apart dependencies by class (e.g., runtime, exams, docs). -
SBOM mills ought to doc their strategy to producing SBOMs.
This can assist shoppers higher perceive potential variations in SBOMs for a similar software program. Additionally doc the use case for which the SBOM is being generated. Completely different use circumstances could require variations in SBOMs. -
Use the suitable device for the environmen
t
.
SBOM creators and customers ought to guarantee they’re utilizing an acceptable SBOM device for his or her particular atmosphere. SBOM instruments sometimes concentrate on a subset of the programming languages and construct environments. -
Assist developer neighborhood 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 influence as a result of they decrease the barrier for creating SBOMs and push the SBOM era additional upstream to undertaking 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 that means and allowable values for every subject, its cardinality, and structural points. The
OWASP Software program Part Verifications Normal (SCVS) BOM Maturity Mannequin
profiles function is an instance. One other strategy can be to outline a JSON schema that extends the present schemas for CycloneDX and/or SPDX and provides the mandatory 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 demanding infrastructure methods. As extra organizations require use of SBOMs, there might be better want to make sure their high quality and completeness, together with offering transparency for undeclared dependencies. Choices to maintain SBOM components opaque could also be rethought if third occasion SBOMs can present wanted transparency. This analysis undertaking is a part of a unbroken SEI effort to enhance the standard of SBOMs.