61 lines
1.9 KiB
JavaScript
61 lines
1.9 KiB
JavaScript
const assert = require('assert')
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const isGzipFile = async (handler, fd) => {
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// https://tools.ietf.org/html/rfc1952.html#page-5
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const magicNumber = Buffer.allocUnsafe(2)
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assert.strictEqual((await handler.read(fd, magicNumber, 0)).bytesRead, magicNumber.length)
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return magicNumber[0] === 31 && magicNumber[1] === 139
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}
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// TODO: better check?
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//
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// our heuristic is not good enough, there has been some false positives
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// (detected as invalid by us but valid by `tar` and imported with success),
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// either THOUGH THEY MAY HAVE BEEN COMPRESSED FILES:
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// - these files were normal but the check is incorrect
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// - these files were invalid but without data loss
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// - these files were invalid but with silent data loss
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//
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// maybe reading the end of the file looking for a file named
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// /^Ref:\d+/\d+\.checksum$/ and then validating the tar structure from it
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//
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// https://github.com/npm/node-tar/issues/234#issuecomment-538190295
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const isValidTar = async (handler, size, fd) => {
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if (size <= 1024 || size % 512 !== 0) {
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return false
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}
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const buf = Buffer.allocUnsafe(1024)
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assert.strictEqual((await handler.read(fd, buf, size - buf.length)).bytesRead, buf.length)
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return buf.every(_ => _ === 0)
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}
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// TODO: find an heuristic for compressed files
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async function isValidXva(path) {
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const handler = this._handler
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try {
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const fd = await handler.openFile(path, 'r')
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try {
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const size = await handler.getSize(fd)
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if (size < 20) {
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// neither a valid gzip not tar
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return false
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}
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return (await isGzipFile(handler, fd))
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? true // gzip files cannot be validated at this time
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: await isValidTar(handler, size, fd)
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} finally {
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handler.closeFile(fd).catch(noop)
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}
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} catch (error) {
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// never throw, log and report as valid to avoid side effects
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console.error('isValidXva', path, error)
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return true
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}
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}
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exports.isValidXva = isValidXva
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const noop = Function.prototype
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