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vulnerability attestation: ITE-9 specification #268

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Sep 8, 2023
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vulnerability attestation: ITE-9 specification #268

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4fd1020
add vulnerability predicate type
hectorj2f Jul 23, 2023
69d51fc
address reviewer comments
hectorj2f Aug 6, 2023
89b4d48
address reviewer comments
hectorj2f Aug 17, 2023
3caded8
add few links to examples
hectorj2f Aug 17, 2023
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2 changes: 2 additions & 0 deletions spec/predicates/README.md
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Expand Up @@ -23,13 +23,15 @@ our [vetting process], and may be of general interest:
artifact.
- [SPDX]: SPDX-formatted BOM for software artifacts.
- [CycloneDX]: CycloneDX BOM for software artifacts.
- [Vulnerability]: Defines the metadata to share the results of vulnerability scanning on software artifacts.
- [Test Result]: A generic schema to express results of any type of tests.

[CycloneDX]: https://cyclonedx.org/
[Link]: link.md
[New Predicate Guidelines]: ../../docs/new_predicate_guidelines.md
[Runtime Traces]: runtime-trace.md
[SCAI Report]: scai.md
[Vulnerability]: vuln.md
[SLSA Provenance]: https://slsa.dev/provenance
[SLSA Verification Summary]: vsa.md
[SPDX]: spdx.md
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136 changes: 136 additions & 0 deletions spec/predicates/vuln.md
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@@ -0,0 +1,136 @@
# Predicate type: Vulnerabilities

Type URI: https://in-toto.io/attestation/vulns/attribute-report
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Version: 0.1

## Purpose

The definition of a vulnerability attestation type has been discussed in the past in [in-toto attestation](https://github.com/in-toto/attestation/issues/58) and [issue](https://github.com/sigstore/cosign/issues/442). However we need to identify two different purposes from these initial conversations:

* The definition of a common format to represent the results of a vulnerability report.

* The definition of a certain set of metadata fields that could help to consume these vulnerability attestations from the different scanning tools.

Obviously the first goal is quite challenging and requires a bigger community to agree upon a specific format. As a consequence, the following attestation type focuses on the definition of that common metadata which could enable the beginning of an exportable and manageable vulnerability attestation.

This document describes a vulnerability attestation type to represent vulnerability reports from the scanners in an "exportable" manner and independently of the format chosen to output the results.

## Prerequisites

The in-toto [attestation] framework and a [Vulnerability scanner tool].
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## Use Cases
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nit: for some reason Markdown doesn't seem to identify this as a header?

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having a look at this!


When sharing the results of a vulnerability scan using an attestation, there is certain metadata that is crucial to trust and reuse this information.
Information about the scanner used during the scanning is relevant to trust these resuls. The state of the vulnerability database used to search for vulnerabilities defines the accuracy of the results. Other metadata information such as the timestamp when the scan finished could define the reusability of these results.
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nit: resuls -> results


## Model

This is a predicate type that fits within the larger [Attestation] framework.
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## Schema

The schema of this predicate type is documented below.

### Fields

The fields that make up this predicate type are:

The `subject` contains whatever software artifacts are to be associated with this vulnerability report document.
The `predicate` contains a JSON-encoded data with the following fields:

**scanner**

> There are lots of container image scanners such as Trivy, Grype, Clair, etc.
> This field describes which scanner is used while performing a container image scan,
> as well as version information and which Vulnerability DB is used.

**scanner.uri** string (ResourceURI), optional

> > URI indicating the identity of the source of the scanner.

**scanner.version** string (ResourceURI), optional

> The version of the scanner.

**scanner.db.uri** string (ResourceURI), optional

> URI indicating the identity of the source of the Vulnerability DB.

**scanner.db.version** string, optional

> The version of the Vulnerability DB.

**scanner.db.lastUpdate string (Timestamp), required**

> The timestamp of when the vulnerability DB was updated last time.

**scanner.result** object
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@pxp928 pxp928 Jul 24, 2023 •
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As this is the most important, we should have a set struct that people should follow. For example, a field to specify vulnerabilityIDs and such.

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Agreed.

I'd probably expect a list of vulnerability identifiers coupled with severity. If you'd like to allow scanners to add additional custom information perhaps let them add annotations?

E.g.

scanner.result = [{"id": "CVE-123", "severity": "medium", "annotations": { "cvss_score": 5.2 }}, {...}]

I could see having different lists for CVEs vs OSV results?

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It sounds good to me 👍🏻 !

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@TomHennen @pxp928 This suggestion makes sense to me. But I wanted to stay away from the defined format to represent the results at least for now. Users may prefer to use SARIF,or any other custom JSON format to set the results of the scan. I'd say a second iteration should define the format of this result struct.

wdyt ?

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IMO the real value from predicates is having the predicates be well defined so that consumers know how to use it. Without result being well defined I don't think there's much value. Perhaps I'm missing something?

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@hectorj2f hectorj2f Jul 27, 2023 •
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@TomHennen Sure! I highlighted it on the Purpose section. My initial goal was to define the metadata around the results which could help to exchange these attestations without having to solve the problem of which format to use when sharing the results of a vulnerability scan by any scanner.

However I am happy to move on defining a structure for the result's section if we feel we are ready to come to an agreement. cc @znewman01

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Hey @hectorj2f, yes we should define a starting structure for the results for an initial release that we can iterate on if needed. For example, having a list of vulnerabilityIDs might be a start. Not sure if we want to include this but we could also have severity:

{
	"severity": [ {
		"type": string,
		"score": string
	} ]
}

similar to the osv implementation: https://ossf.github.io/osv-schema/#severity-field

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Sgtm! I'll add these suggestions.


> This is the most important part of this field because it'll store the scan result as a whole. So, people might want
> to use this field to take decisions based on them by making use of Policy Engines tooling whether allow or deny these images.

**metadata.scanStartedOn string (Timestamp), required**

> The timestamp of when the scan started.

**metadata.scanFinishedOn string (Timestamp), required**

> The timestamp of when the scan completed.

## Example

```jsonc
{
"_type": "https://in-toto.io/Statement/v0.1",
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"subject": [
{
...
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}
],
// Predicate:
"predicateType": "https://in-toto.io/attestation/vulns/attribute-report/v0.1",
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"predicate": {
"invocation": {
"parameters": [],
// [ "--format=json", "--skip-db-update" ]
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"uri": "",
// https://github.com/developer-guy/alpine/actions/runs/1071875574
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"event_id": "",
// 1071875574
"builder.id": ""
// GitHub Actions
},
"scanner": {
"uri": "",
// pkg:github/aquasecurity/trivy@244fd47e07d1004f0aed9
"version": "",
// 0.19.2
"db": {
"uri": "",
// pkg:github/aquasecurity/trivy-db/commit/4c76bb580b2736d67751410fa4ab66d2b6b9b27d
"version": "",
// "v1-2021080612"
"lastUpdate": ""
// 2021-08-06T17:45:50.52Z
},
"result": {}
},
"metadata": {
"scanStartedOn": "",
// 2021-08-06T17:45:50.52Z
"scanFinishedOn": ""
// 2021-08-06T17:50:50.52Z
}
}
}
```

## Changelog and Migrations

Not applicable for this initial version.

[Attestation]: ../README.md