Files
passkit-generator/src/signature.ts
2021-06-19 20:26:06 +02:00

79 lines
2.0 KiB
TypeScript

import forge from "node-forge";
import type * as Schemas from "./schemas";
/**
* Generates the PKCS #7 cryptografic signature for the manifest file.
*
* @method create
* @params {Object} manifest - Manifest content.
* @returns {Buffer}
*/
export function create(
manifest: Schemas.Manifest,
certificates: Schemas.CertificatesSchema,
): Buffer {
const signature = forge.pkcs7.createSignedData();
signature.content = forge.util.createBuffer(
JSON.stringify(manifest),
"utf8",
);
signature.addCertificate(certificates.wwdr);
signature.addCertificate(certificates.signerCert);
/**
* authenticatedAttributes belong to PKCS#9 standard.
* It requires at least 2 values:
* • content-type (which is a PKCS#7 oid) and
* • message-digest oid.
*
* Wallet requires a signingTime.
*/
signature.addSigner({
key: certificates.signerKey,
certificate: certificates.signerCert,
digestAlgorithm: forge.pki.oids.sha1,
authenticatedAttributes: [
{
type: forge.pki.oids.contentType,
value: forge.pki.oids.data,
},
{
type: forge.pki.oids.messageDigest,
},
{
type: forge.pki.oids.signingTime,
},
],
});
/**
* We are creating a detached signature because we don't need the signed content.
* Detached signature is a property of PKCS#7 cryptography standard.
*/
signature.sign({ detached: true });
/**
* Signature here is an ASN.1 valid structure (DER-compliant).
* Generating a non-detached signature, would have pushed inside signature.contentInfo
* (which has type 16, or "SEQUENCE", and is an array) a Context-Specific element, with the
* signed content as value.
*
* In fact the previous approach was to generating a detached signature and the pull away the generated
* content.
*
* That's what happens when you copy a fu****g line without understanding what it does.
* Well, nevermind, it was funny to study BER, DER, CER, ASN.1 and PKCS#7. You can learn a lot
* of beautiful things. ¯\_(ツ)_/¯
*/
return Buffer.from(
forge.asn1.toDer(signature.toAsn1()).getBytes(),
"binary",
);
}