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refactor(encryption): extract standalone encrypter/decrypter (#1945)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| import { _decrypt, _encrypt, ENCRYPTION_KEY_BYTES, getKeyDigest, loadKey } from './utils'; | ||
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| /** | ||
| * Default encrypter | ||
| */ | ||
| export class Encrypter { | ||
| private key: CryptoKey | undefined; | ||
| private keyDigest: string | undefined; | ||
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| constructor(private readonly encryptionKey: Uint8Array) { | ||
| if (encryptionKey.length !== ENCRYPTION_KEY_BYTES) { | ||
| throw new Error(`Encryption key must be ${ENCRYPTION_KEY_BYTES} bytes`); | ||
| } | ||
| } | ||
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| /** | ||
| * Encrypts the given data | ||
| */ | ||
| async encrypt(data: string): Promise<string> { | ||
| if (!this.key) { | ||
| this.key = await loadKey(this.encryptionKey, ['encrypt']); | ||
| } | ||
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| if (!this.keyDigest) { | ||
| this.keyDigest = await getKeyDigest(this.encryptionKey); | ||
| } | ||
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| return _encrypt(data, this.key, this.keyDigest); | ||
| } | ||
| } | ||
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| /** | ||
| * Default decrypter | ||
| */ | ||
| export class Decrypter { | ||
| private keys: Array<{ key: CryptoKey; digest: string }> = []; | ||
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| constructor(private readonly decryptionKeys: Uint8Array[]) { | ||
| if (decryptionKeys.length === 0) { | ||
| throw new Error('At least one decryption key must be provided'); | ||
| } | ||
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| for (const key of decryptionKeys) { | ||
| if (key.length !== ENCRYPTION_KEY_BYTES) { | ||
| throw new Error(`Decryption key must be ${ENCRYPTION_KEY_BYTES} bytes`); | ||
| } | ||
| } | ||
| } | ||
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| /** | ||
| * Decrypts the given data | ||
| */ | ||
| async decrypt(data: string): Promise<string> { | ||
| if (this.keys.length === 0) { | ||
| this.keys = await Promise.all( | ||
| this.decryptionKeys.map(async (key) => ({ | ||
| key: await loadKey(key, ['decrypt']), | ||
| digest: await getKeyDigest(key), | ||
| })) | ||
| ); | ||
| } | ||
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| return _decrypt(data, async (digest) => | ||
| this.keys.filter((entry) => entry.digest === digest).map((entry) => entry.key) | ||
| ); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,96 @@ | ||
| import { z } from 'zod'; | ||
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| export const ENCRYPTER_VERSION = 1; | ||
| export const ENCRYPTION_KEY_BYTES = 32; | ||
| export const IV_BYTES = 12; | ||
| export const ALGORITHM = 'AES-GCM'; | ||
| export const KEY_DIGEST_BYTES = 8; | ||
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| const encoder = new TextEncoder(); | ||
| const decoder = new TextDecoder(); | ||
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| const encryptionMetaSchema = z.object({ | ||
| // version | ||
| v: z.number(), | ||
| // algorithm | ||
| a: z.string(), | ||
| // key digest | ||
| k: z.string(), | ||
| }); | ||
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| export async function loadKey(key: Uint8Array, keyUsages: KeyUsage[]): Promise<CryptoKey> { | ||
| return crypto.subtle.importKey('raw', key, ALGORITHM, false, keyUsages); | ||
| } | ||
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| export async function getKeyDigest(key: Uint8Array) { | ||
| const rawDigest = await crypto.subtle.digest('SHA-256', key); | ||
| return new Uint8Array(rawDigest.slice(0, KEY_DIGEST_BYTES)).reduce( | ||
| (acc, byte) => acc + byte.toString(16).padStart(2, '0'), | ||
| '' | ||
| ); | ||
| } | ||
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| export async function _encrypt(data: string, key: CryptoKey, keyDigest: string): Promise<string> { | ||
| const iv = crypto.getRandomValues(new Uint8Array(IV_BYTES)); | ||
| const encrypted = await crypto.subtle.encrypt( | ||
| { | ||
| name: ALGORITHM, | ||
| iv, | ||
| }, | ||
| key, | ||
| encoder.encode(data) | ||
| ); | ||
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| // combine IV and encrypted data into a single array of bytes | ||
| const cipherBytes = [...iv, ...new Uint8Array(encrypted)]; | ||
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| // encryption metadata | ||
| const meta = { v: ENCRYPTER_VERSION, a: ALGORITHM, k: keyDigest }; | ||
|
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| // convert concatenated result to base64 string | ||
| return `${btoa(JSON.stringify(meta))}.${btoa(String.fromCharCode(...cipherBytes))}`; | ||
| } | ||
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| export async function _decrypt(data: string, findKey: (digest: string) => Promise<CryptoKey[]>): Promise<string> { | ||
| const [metaText, cipherText] = data.split('.'); | ||
| if (!metaText || !cipherText) { | ||
| throw new Error('Malformed encrypted data'); | ||
| } | ||
|
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| let metaObj: unknown; | ||
| try { | ||
| metaObj = JSON.parse(atob(metaText)); | ||
| } catch (error) { | ||
| throw new Error('Malformed metadata'); | ||
| } | ||
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| // parse meta | ||
| const { a: algorithm, k: keyDigest } = encryptionMetaSchema.parse(metaObj); | ||
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| // find a matching decryption key | ||
| const keys = await findKey(keyDigest); | ||
| if (keys.length === 0) { | ||
| throw new Error('No matching decryption key found'); | ||
| } | ||
|
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| // convert base64 back to bytes | ||
| const bytes = Uint8Array.from(atob(cipherText), (c) => c.charCodeAt(0)); | ||
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| // extract IV from the head | ||
| const iv = bytes.slice(0, IV_BYTES); | ||
| const cipher = bytes.slice(IV_BYTES); | ||
| let lastError: unknown; | ||
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| for (const key of keys) { | ||
| let decrypted: ArrayBuffer; | ||
| try { | ||
| decrypted = await crypto.subtle.decrypt({ name: algorithm, iv }, key, cipher); | ||
| } catch (err) { | ||
| lastError = err; | ||
| continue; | ||
| } | ||
| return decoder.decode(decrypted); | ||
| } | ||
|
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||
| throw lastError; | ||
| } |
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