All files / lib verifyPDF.js

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import forge from "node-forge";
 
import { VerifyPDFError } from "./VerifyPDFError.js";
import { extractCertificatesDetails } from "./certificateDetails.js";
import {
	authenticateSignature,
	checkForSubFilter,
	extractSignature,
	getClientCertificate,
	getMessageFromSignature,
	isCertsExpired,
	preparePDF,
	sortCertificateChain,
} from "./helpers/index.js";
 
/**
 * @typedef SignatureMeta
 * @property {string|null} [contactInfo]
 * @property {string|null} [reason]
 * @property {string|null} [location]
 * @property {string|null} [name]
 */
 
/**
 * @param {forge.Bytes} signature
 * @param {Uint8Array} signedData
 * @param {SignatureMeta} [signatureMeta]
 */
const verify = (signature, signedData, signatureMeta) => {
	const message = getMessageFromSignature(signature);
	const {
		certificates,
		rawCapture: {
			signature: sig,
			authenticatedAttributes: attrs,
			digestAlgorithm,
		},
	} = message;
	const hashAlgorithmOid = forge.asn1.derToOid(digestAlgorithm);
	/**
	 * @type {keyof typeof forge.md.algorithms}
	 */
	// @ts-expect-error IDK
	const hashAlgorithm = forge.pki.oids[hashAlgorithmOid].toLowerCase();
	const set = forge.asn1.create(
		forge.asn1.Class.UNIVERSAL,
		forge.asn1.Type.SET,
		true,
		attrs,
	);
	const clientCertificate = getClientCertificate(certificates);
	const digest = forge.md[hashAlgorithm]
		.create()
		.update(forge.asn1.toDer(set).data)
		.digest()
		.getBytes();
	/**
	 * @type {forge.pki.rsa.PublicKey | undefined}
	 */
	// @ts-expect-error IDK
	const publicKey = clientCertificate?.publicKey;
	const validAuthenticatedAttributes = publicKey?.verify(digest, sig);
	if (!validAuthenticatedAttributes) {
		throw new VerifyPDFError(
			"Wrong authenticated attributes",
			VerifyPDFError.Type.VERIFY_SIGNATURE,
		);
	}
	const messageDigestAttr = forge.pki.oids.messageDigest;
	const fullAttrDigest = attrs.find(
		/**
		 * @param {forge.pki.Attribute} attr
		 */
		(attr) => forge.asn1.derToOid(attr.value[0].value) === messageDigestAttr,
	);
	const attrDigest = fullAttrDigest.value[1].value[0].value;
	const dataDigest = forge.md[hashAlgorithm]
		.create()
		.update(Buffer.from(signedData).toString("latin1"))
		.digest()
		.getBytes();
	const integrity = dataDigest === attrDigest;
	const sortedCerts = sortCertificateChain(certificates);
	const parsedCerts = extractCertificatesDetails(sortedCerts);
	const authenticity = authenticateSignature(sortedCerts);
	const expired = isCertsExpired(sortedCerts);
	return {
		verified: integrity && authenticity && !expired,
		authenticity,
		integrity,
		expired,
		meta: { certs: parsedCerts, signatureMeta },
	};
};
 
/**
 * @param {Uint8Array} pdf
 */
export default (pdf) => {
	const pdfBuffer = preparePDF(pdf);
	checkForSubFilter(pdfBuffer);
	try {
		const { signatureStr, signedData, signatureMeta } =
			extractSignature(pdfBuffer);
 
		const signatures = signedData.map((signed, index) => {
			return verify(signatureStr[index] ?? "", signed, signatureMeta[index]);
		});
 
		return {
			verified: signatures.every((o) => o.verified === true),
			authenticity: signatures.every((o) => o.authenticity === true),
			integrity: signatures.every((o) => o.integrity === true),
			expired: signatures.some((o) => o.expired === true),
			signatures,
		};
	} catch (error) {
		return {
			verified: false,
			message:
				// @ts-expect-error error
				error.message,
			error,
		};
	}
};