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 may be rising curiosity in utilizing SBOMs to assist software program provide chain threat administration. In September 2024 Military leaders signed a memorandum requiring SBOMs for vendor-supplied software program. Extra lately, the Division of Protection (DoD) Chief Info Officer, by 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 related information for a bit of software program at a given level in its lifecycle, however this isn’t all the time the case. The divergence of SBOMs for particular person items of software program can undermine confidence in these necessary paperwork for software program high quality and safety. This weblog put up outlines our staff’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 mission, sponsored by the Cybersecurity and Infrastructure Safety Company (CISA), aimed to uncover the foundation causes of SBOM divergence, similar 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 lately launched Software program Invoice of Supplies (SBOM) Harmonization Plugfest 2024, on which this put up is predicated, outlines our staff’s findings, evaluation, and suggestions to assist SBOM producers generate extra constant and dependable SBOMs.
We requested Plugfest members to generate and submit SBOMs primarily based on 9 software program targets chosen as a consultant pattern of assorted programming languages as seen in Desk 1 under.
The SEI gained approval from most members to make their submissions public. These SBOMs that have been authorised for launch are now accessible at SEI’s GitHub website.
Overview and Evaluation of Submitted SBOMs
We acquired 243 SBOMs from 21 Plugfest members. To make sure anonymity and to forestall 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 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 factors we used for minimal components are these required for documenting a software program product’s major 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 Creator Identify
- SBOM Timestamp
- SBOM Sort
- 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. Contributors 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 inside Bitbucket repository, which additionally contained a replica 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:
- info 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 info 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 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 varieties 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) 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 kind (supply/construct). We used dependency graph info to research 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’d count on to see submitted by Plugfest members. The baseline SBOMs additionally allowed us to develop evaluation instruments early within the mission so we might begin analyzing members’ 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 varieties 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 members for a similar software program on the identical lifecycle part. Some variance in SBOM content material is as a result of 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 spread of potential software program variations, however SBOMs permit solely a single model to be documented for every dependency. This ends in 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 as a result of considerably synthetic nature of producing SBOMs for a analysis mission.
- Use circumstances. SBOMs have numerous use circumstances, which result in several types 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, members could have taken a extra harmonized method to how they generated, enriched, or augmented their SBOMs for that use case.
- Construct and supply SBOMs. Contributors 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 surroundings utilizing the goal’s language or build-framework-specific course of. Construct SBOMs additionally diversified primarily based on the surroundings and power configurations every participant used. Supply SBOMs seize dependencies declared or inferred from supply code. Some members 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 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, similar to goal documentation construct instruments, CI/CD pipeline parts, and non-obligatory language bindings.
7 Suggestions for Bettering 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 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 somewhat than non-obligatory. -
Element Model String.
Emphasize the significance of reporting the model precisely as offered by the provider. This reporting minimizes the necessity for normalization on account of information being inconsistently reported (e.g., one SBOM reviews
v 2.0
and one other reviews
2.0
). -
Element Provider Identify.
Embrace the title of the entity that offered the contents of the software program being described. This helps customers of the SBOM perceive which third events have been a part of the availability chain. A standard registry of element suppliers would assist normalize this entry. For open supply software program parts, which would not have a conventional provider, a direct reference or hyperlink to the mission repository needs to be offered. -
Element 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 the way to confirm the hash worth. Alternatively, when supplying cryptographic hashes, SBOM creators needs to be specific about what was hashed. -
Element License.
Emphasize the necessity to present licensing info or to notice that the license info shouldn’t be recognized 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
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 differentiate dependencies by class (e.g., runtime, assessments, 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. Totally different use circumstances could require variations in SBOMs. -
Use the suitable device for the surroundings.
SBOM creators and customers ought to guarantee they’re utilizing an applicable SBOM device for his or her particular surroundings. SBOM instruments sometimes deal with a subset of the programming languages and construct environments. -
Assist developer group 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 impression as a result of they decrease the barrier for creating SBOMs and push the SBOM era additional upstream to mission maintainers who’ve detailed data 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 subject, its cardinality, and structural points. 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 prevailing 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 programs, together with DoD and important infrastructure programs. As extra organizations require use of SBOMs, there might be larger 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 social gathering SBOMs can present wanted transparency. This analysis mission is a part of a seamless SEI effort to enhance the standard of SBOMs.