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toolkit/packages/attest/src/attest.ts

98 lines
3.1 KiB
TypeScript

import {bundleToJSON} from '@sigstore/bundle'
import {X509Certificate} from 'crypto'
import {SigstoreInstance, signingEndpoints} from './endpoints'
import {buildIntotoStatement} from './intoto'
import {Payload, signPayload} from './sign'
import {writeAttestation} from './store'
import type {Bundle} from '@sigstore/sign'
import type {Attestation, Predicate, Subject} from './shared.types'
const INTOTO_PAYLOAD_TYPE = 'application/vnd.in-toto+json'
/**
* Options for attesting a subject / predicate.
*/
export type AttestOptions = {
// The name of the subject to be attested.
subjectName: string
// The digest of the subject to be attested. Should be a map of digest
// algorithms to their hex-encoded values.
subjectDigest: Record<string, string>
// Content type of the predicate being attested.
predicateType: string
// Predicate to be attested.
predicate: object
// GitHub token for writing attestations.
token: string
// Sigstore instance to use for signing. Must be one of "public-good" or
// "github".
sigstore?: SigstoreInstance
// Whether to skip writing the attestation to the GH attestations API.
skipWrite?: boolean
}
/**
* Generates an attestation for the given subject and predicate. The subject and
* predicate are combined into an in-toto statement, which is then signed using
* the identified Sigstore instance and stored as an attestation.
* @param options - The options for attestation.
* @returns A promise that resolves to the attestation.
*/
export async function attest(options: AttestOptions): Promise<Attestation> {
const subject: Subject = {
name: options.subjectName,
digest: options.subjectDigest
}
const predicate: Predicate = {
type: options.predicateType,
params: options.predicate
}
const statement = buildIntotoStatement(subject, predicate)
// Sign the provenance statement
const payload: Payload = {
body: Buffer.from(JSON.stringify(statement)),
type: INTOTO_PAYLOAD_TYPE
}
const endpoints = signingEndpoints(options.sigstore)
const bundle = await signPayload(payload, endpoints)
// Store the attestation
let attestationID: string | undefined
if (options.skipWrite !== true) {
attestationID = await writeAttestation(bundleToJSON(bundle), options.token)
}
return toAttestation(bundle, attestationID)
}
function toAttestation(bundle: Bundle, attestationID?: string): Attestation {
let certBytes: Buffer
switch (bundle.verificationMaterial.content.$case) {
case 'x509CertificateChain':
certBytes =
bundle.verificationMaterial.content.x509CertificateChain.certificates[0]
.rawBytes
break
case 'certificate':
certBytes = bundle.verificationMaterial.content.certificate.rawBytes
break
default:
throw new Error('Bundle must contain an x509 certificate')
}
const signingCert = new X509Certificate(certBytes)
// Collect transparency log ID if available
const tlogEntries = bundle.verificationMaterial.tlogEntries
const tlogID = tlogEntries.length > 0 ? tlogEntries[0].logIndex : undefined
return {
bundle: bundleToJSON(bundle),
certificate: signingCert.toString(),
tlogID,
attestationID
}
}