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feat: add canonical asar integrity information calculator #411

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575b32d
feat: add canonical asar integrity information calculator
nmggithub Mar 18, 2026
8597ff3
fix: add explicit return type to `getArchiveIntegrity`
nmggithub Mar 18, 2026
a49361f
feat: add `getAsarIntegrityInfo` function
nmggithub Mar 18, 2026
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1 change: 1 addition & 0 deletions src/asar.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -409,6 +409,7 @@ export function extractAll(archivePath: string, dest: string) {
}
}

export { getArchiveIntegrity, getAsarIntegrityInfo } from './integrity.js';
export { uncacheAll, uncacheFilesystem as uncache, FileRecord, DirectoryRecord } from './disk.js';
export {
calculateIntegrityDigestForApp,
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4 changes: 2 additions & 2 deletions src/integrity-digest.ts
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Expand Up @@ -3,7 +3,7 @@ import crypto from 'node:crypto';
import plist from 'plist';

import { wrappedFs as fs } from './wrapped-fs.js';
import { FileRecord } from './disk.js';
import { ArchiveIntegrity } from './integrity.js';

// Integrity digest type definitions

Expand Down Expand Up @@ -34,7 +34,7 @@ type AnyIntegrityDigest = DigestByVersion[keyof DigestByVersion];

// Integrity digest calculation functions

type AsarIntegrity = Record<string, Pick<FileRecord['integrity'], 'algorithm' | 'hash'>>;
type AsarIntegrity = Record<string, ArchiveIntegrity>;

function isValidAsarIntegrity(asarIntegrity: any): asarIntegrity is AsarIntegrity {
if (typeof asarIntegrity !== 'object' || asarIntegrity === null) return false;
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57 changes: 57 additions & 0 deletions src/integrity.ts
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@@ -1,6 +1,7 @@
import crypto from 'node:crypto';
import stream from 'node:stream';
import streamPromises from 'node:stream/promises';
import { FileRecord, getRawHeader } from './asar.js';

const ALGORITHM = 'SHA256';
// 4MB default block size
Expand Down Expand Up @@ -64,3 +65,59 @@ export async function getFileIntegrity(
blocks: blockHashes,
};
}

export type ArchiveIntegrity = Pick<FileRecord['integrity'], 'algorithm' | 'hash'>;
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@nmggithub nmggithub Mar 18, 2026 •
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I stole this from @electron/packager's implementation. I wonder if its the best way to type this.

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@nmggithub nmggithub Mar 18, 2026

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It seems, even with Windows' differing implementation, we still use this as the canonical shape and simply convert it at build time in @electron/packager. Not sure if we want to expose the Windows shape as well or just have consumers do this conversion themselves for Windows, when needed.

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@nmggithub nmggithub Mar 21, 2026

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Ended up exposing the Windows resource records and macOS Info.plist dictionaries seperately.


export function getArchiveIntegrity(archivePath: string): ArchiveIntegrity {
const { headerString } = getRawHeader(archivePath);
return {
algorithm: 'SHA256',
hash: crypto.createHash('SHA256').update(headerString).digest('hex'),
};
}

// To be inserted into Info.plist of the app.
export type AsarIntegrityInfoMacOS = Record<string, ArchiveIntegrity>;

// To be added as a resource to the app.
export type AsarIntegrityInfoWindows = { resourceType: 'Integrity', resourceName: 'ElectronAsar', resourceData: Buffer };
export type AsarIntegrityInfoWindowsFiles = {file: string, alg: string, value: string}[];

type ASARIntegrityPlatformInfoMap = {
macos: AsarIntegrityInfoMacOS;
windows: AsarIntegrityInfoWindows;
};

export function getAsarIntegrityInfo(
files: { relativePath: string; fullPath: string }[],
platform: 'macos',
): AsarIntegrityInfoMacOS;
export function getAsarIntegrityInfo(
files: { relativePath: string; fullPath: string }[],
platform: 'windows',
): AsarIntegrityInfoWindows;
export function getAsarIntegrityInfo(
files: { relativePath: string; fullPath: string }[],
platform: keyof ASARIntegrityPlatformInfoMap,
) {
switch (platform) {
case 'macos':
return Object.fromEntries(
files.map((file) => [file.relativePath, getArchiveIntegrity(file.fullPath)]),
);
case 'windows': {
const filesJson: AsarIntegrityInfoWindowsFiles = files.map((file) => ({
file: file.relativePath,
alg: 'SHA256',
value: getArchiveIntegrity(file.fullPath).hash,
}));
return {
resourceType: 'Integrity',
resourceName: 'ElectronAsar',
resourceData: Buffer.from(JSON.stringify(filesJson), 'utf-8'),
} as AsarIntegrityInfoWindows;
}
default:
throw new Error(`Invalid platform: ${platform}`);
}
}