client/src/assets/player/p2p-media-loader/segment-validator.ts

   1 import { Segment } from 'p2p-media-loader-core'
   2 import { basename } from 'path'
   3
   4 function segmentValidatorFactory (segmentsSha256Url: string) {
   5   const segmentsJSON = fetchSha256Segments(segmentsSha256Url)
   6   const regex = /bytes=(\d+)-(\d+)/
   7
   8   return async function segmentValidator (segment: Segment) {
   9     const filename = basename(segment.url)
  10     const captured = regex.exec(segment.range)
  11
  12     const range = captured[1] + '-' + captured[2]
  13
  14     const hashShouldBe = (await segmentsJSON)[filename][range]
  15     if (hashShouldBe === undefined) {
  16       throw new Error(`Unknown segment name ${filename}/${range} in segment validator`)
  17     }
  18
  19     const calculatedSha = bufferToEx(await sha256(segment.data))
  20     if (calculatedSha !== hashShouldBe) {
  21       throw new Error(
  22         `Hashes does not correspond for segment ${filename}/${range}` +
  23         `(expected: ${hashShouldBe} instead of ${calculatedSha})`
  24       )
  25     }
  26   }
  27 }
  28
  29 // ---------------------------------------------------------------------------
  30
  31 export {
  32   segmentValidatorFactory
  33 }
  34
  35 // ---------------------------------------------------------------------------
  36
  37 function fetchSha256Segments (url: string) {
  38   return fetch(url)
  39     .then(res => res.json())
  40     .catch(err => {
  41       console.error('Cannot get sha256 segments', err)
  42       return {}
  43     })
  44 }
  45
  46 function sha256 (data?: ArrayBuffer) {
  47   if (!data) return undefined
  48
  49   return window.crypto.subtle.digest('SHA-256', data)
  50 }
  51
  52 // Thanks: https://stackoverflow.com/a/53307879
  53 function bufferToEx (buffer?: ArrayBuffer) {
  54   if (!buffer) return ''
  55
  56   let s = ''
  57   const h = '0123456789abcdef'
  58   const o = new Uint8Array(buffer)
  59
  60   o.forEach((v: any) => s += h[ v >> 4 ] + h[ v & 15 ])
  61
  62   return s
  63 }