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import path from 'path'
import fs from 'fs'
import crypto from 'crypto'
import type { __ApiPreviewProps } from '../server/api-utils'
import { getStorageDirectory } from '../server/cache-dir'
const CONFIG_FILE = '.previewinfo'
const PREVIEW_ID = 'previewModeId'
const PREVIEW_SIGNING_KEY = 'previewModeSigningKey'
const PREVIEW_ENCRYPTION_KEY = 'previewModeEncryptionKey'
const PREVIEW_EXPIRE_AT = 'expireAt'
const EXPIRATION = 1000 * 60 * 60 * 24 * 14 // 14 days
async function writeCache(distDir: string, config: __ApiPreviewProps) {
const cacheBaseDir = getStorageDirectory(distDir)
if (!cacheBaseDir) return
const configPath = path.join(cacheBaseDir, CONFIG_FILE)
if (!fs.existsSync(cacheBaseDir)) {
await fs.promises.mkdir(cacheBaseDir, { recursive: true })
}
await fs.promises.writeFile(
configPath,
JSON.stringify({
[PREVIEW_ID]: config.previewModeId,
[PREVIEW_SIGNING_KEY]: config.previewModeSigningKey,
[PREVIEW_ENCRYPTION_KEY]: config.previewModeEncryptionKey,
[PREVIEW_EXPIRE_AT]: Date.now() + EXPIRATION,
})
)
}
function generateConfig() {
return {
previewModeId: crypto.randomBytes(16).toString('hex'),
previewModeSigningKey: crypto.randomBytes(32).toString('hex'),
previewModeEncryptionKey: crypto.randomBytes(32).toString('hex'),
}
}
// This utility is used to get a key for the cache directory. If the
// key is not present, it will generate a new one and store it in the
// cache directory inside dist.
// The key will also expire after a certain amount of time. Once it
// expires, a new one will be generated.
export async function generatePreviewKeys({
distDir,
isBuild,
}: {
distDir: string
isBuild: boolean
}): Promise<__ApiPreviewProps> {
const cacheBaseDir = getStorageDirectory(distDir)
if (!cacheBaseDir) {
// There's no persistent storage available. We generate a new config.
// This also covers development time.
return generateConfig()
}
const configPath = path.join(cacheBaseDir, CONFIG_FILE)
async function tryReadCachedConfig(): Promise<false | __ApiPreviewProps> {
if (!fs.existsSync(configPath)) return false
try {
const config = JSON.parse(await fs.promises.readFile(configPath, 'utf8'))
if (!config) return false
if (
typeof config[PREVIEW_ID] !== 'string' ||
typeof config[PREVIEW_ENCRYPTION_KEY] !== 'string' ||
typeof config[PREVIEW_SIGNING_KEY] !== 'string' ||
typeof config[PREVIEW_EXPIRE_AT] !== 'number'
) {
return false
}
// For build time, we need to rotate the key if it's expired. Otherwise
// (next start) we have to keep the key as it is so the runtime key matches
// the build time key.
if (isBuild && config[PREVIEW_EXPIRE_AT] < Date.now()) {
return false
}
return {
previewModeId: config[PREVIEW_ID],
previewModeSigningKey: config[PREVIEW_SIGNING_KEY],
previewModeEncryptionKey: config[PREVIEW_ENCRYPTION_KEY],
}
} catch (e) {
// Broken config file. We should generate a new key and overwrite it.
return false
}
}
const maybeValidConfig = await tryReadCachedConfig()
if (maybeValidConfig !== false) {
return maybeValidConfig
}
const config = generateConfig()
await writeCache(distDir, config)
return config
}
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