A software program invoice of supplies (SBOM) offers transparency into the weather of an built-in software program product. Such transparency is important 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 lately, the Division of Protection (DoD) Chief Data 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.
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 essential paperwork for software program high quality and safety. This weblog submit outlines our staff’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 venture, sponsored by the Cybersecurity and Infrastructure Safety Company (CISA), aimed to uncover the foundation causes of SBOM divergence, comparable to imprecise definitions or requirements, how uncertainty is addressed, or different implementation choices. The SEI introduced collectively SBOM software distributors, requirements producers, and others within the SBOM neighborhood to provide pattern SBOMs for evaluation. The lately launched Software program Invoice of Supplies (SBOM) Harmonization Plugfest 2024, on which this submit relies, outlines our staff’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 under.
The SEI gained approval from most contributors to make their submissions public. These SBOMs that have been accepted for launch are now out there at SEI’s GitHub web site.
Overview and Evaluation of Submitted SBOMs
We acquired 243 SBOMs from 21 Plugfest contributors. To make sure anonymity and to stop any bias in our evaluation, 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 software 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 evaluation 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 parts of the submitted SBOMs was a important part in figuring out their completeness and accuracy. A listing of minimal parts specifies the baseline SBOMs ought to meet and facilitates data sharing. The standards we used for minimal parts are these required for documenting a software program product’s major 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 Identify
- SBOM Timestamp
- SBOM Sort
- SBOM Main Part
- Part Identify
- Part Model String
- Part Provider Identify
- Part Cryptographic Hash
- Part Distinctive Identifier
- Part Relationships
- Part License
- Part 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. Individuals 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 major 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 parts
- 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 recordsdata, and decoding the JSON recordsdata in order that information could possibly be extracted
- extracting minimal parts 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 kinds of relationships amongst these parts as listed within the SBOM.)
- collating information from every SBOM into two widespread information buildings: one for data associated to minimal parts and the opposite for part data
We analyzed the info buildings 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 parts 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 Instrument, 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 venture so we might begin analyzing contributors’ SBOMs as quickly as they have 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 kinds 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 parts in SBOMs from totally different contributors for a similar software program on the identical lifecycle section. Some variance in SBOM content material is as a result of lack of normalization; the identical content material was merely being written in a different 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 enable for a variety of attainable software program variations, however SBOMs enable solely a single model to be documented for every dependency. This leads to SBOMs having numerous variations listed throughout totally different contributors for every goal that allowed model ranges.
- Minimal parts. Some variance in SBOM content material is because of variations in whether or not contributors included minimal parts or not, which can be as a result of considerably synthetic nature of producing SBOMs for a analysis venture.
- Use instances. SBOMs have various use instances, which result in various kinds of SBOMs. The wide range of attainable use instances is an extra trigger for the dearth of harmonization throughout SBOMs for a similar goal. If we had specified a use case, contributors could have taken a extra harmonized method to how they generated, enriched, or augmented their SBOMs for that use case.
- Construct and supply SBOMs. Individuals used totally 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 setting utilizing the goal’s language or build-framework-specific course of. Construct SBOMs additionally diverse primarily based on the setting and power configurations every participant used. Supply SBOMs seize dependencies declared or inferred from supply code. Some contributors used further data from exterior places, such because the artifact repositories referenced by dependencies or the contents of platform toolchain libraries, to deduce further dependencies.
- Dependency interpretation. A evaluation 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 usually deployed, comparable to goal documentation construct instruments, CI/CD pipeline parts, and non-obligatory 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 parts:-
SBOM Sort.
Embody the SBOM Sort to doc the lifecycle section for which this SBOM was generated (e.g., Supply, Construct). We suggest that this attribute be required fairly than non-obligatory. -
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 information being inconsistently reported (e.g., one SBOM stories
v 2.0
and one other stories
2.0
). -
Part 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 have been a part of the provision chain. A standard registry of part suppliers would assist normalize this entry. For open supply software program parts, which don’t have a conventional provider, a direct reference or hyperlink to the venture repository ought to be supplied. -
Part Cryptographic Hash.
SBOM steerage ought to clearly state what parts are being hashed when a cryptographic hash is included. Make it extra simple for SBOM customers to know find out how to confirm the hash worth. Alternatively, when supplying cryptographic hashes, SBOM creators ought to be express about what was hashed. -
Part License.
Emphasize the necessity to present licensing data or to notice that the license data shouldn’t be recognized or was not included.
-
-
Enhance normalization of SBOM parts.
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
major 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, checks, docs). -
SBOM turbines ought to doc their method to producing SBOMs.
This can 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. Completely different use instances could require variations in SBOMs. -
Use the suitable software for the setting.
SBOM creators and customers ought to guarantee they’re utilizing an acceptable SBOM software for his or her particular setting. SBOM instruments usually deal with a subset of the programming languages and construct environments. -
Help developer neighborhood SBOM efforts.
Some developer communities are working to incorporate SBOM turbines in language instruments and construct frameworks to make it a lot simpler for tasks 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 venture 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 discipline, its cardinality, and structural elements. The
OWASP Software program Part Verifications Customary (SCVS) BOM Maturity Mannequin
profiles characteristic is an instance. One other method can 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 Making certain 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 will likely be higher want to make sure their high quality and completeness, together with offering transparency for undeclared dependencies. Choices to maintain SBOM parts opaque could also be rethought if third occasion SBOMs can present wanted transparency. This analysis venture is a part of a seamless SEI effort to enhance the standard of SBOMs.
