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 type SegmentsJSON = { [filename: string]: string | { [byterange: string]: string } }
   5
   6 function segmentValidatorFactory (segmentsSha256Url: string) {
   7   let segmentsJSON = fetchSha256Segments(segmentsSha256Url)
   8   const regex = /bytes=(\d+)-(\d+)/
   9
  10   return async function segmentValidator (segment: Segment, canRefetchSegmentHashes = true) {
  11     const filename = basename(segment.url)
  12
  13     const segmentValue = (await segmentsJSON)[filename]
  14
  15     if (!segmentValue && !canRefetchSegmentHashes) {
  16       throw new Error(`Unknown segment name ${filename} in segment validator`)
  17     }
  18
  19     if (!segmentValue) {
  20       console.log('Refetching sha segments.')
  21
  22       // Refetch
  23       segmentsJSON = fetchSha256Segments(segmentsSha256Url)
  24       segmentValidator(segment, false)
  25       return
  26     }
  27
  28     let hashShouldBe: string
  29     let range = ''
  30
  31     if (typeof segmentValue === 'string') {
  32       hashShouldBe = segmentValue
  33     } else {
  34       const captured = regex.exec(segment.range)
  35       range = captured[1] + '-' + captured[2]
  36
  37       hashShouldBe = segmentValue[range]
  38     }
  39
  40     if (hashShouldBe === undefined) {
  41       throw new Error(`Unknown segment name ${filename}/${range} in segment validator`)
  42     }
  43
  44     const calculatedSha = bufferToEx(await sha256(segment.data))
  45     if (calculatedSha !== hashShouldBe) {
  46       throw new Error(
  47         `Hashes does not correspond for segment ${filename}/${range}` +
  48         `(expected: ${hashShouldBe} instead of ${calculatedSha})`
  49       )
  50     }
  51   }
  52 }
  53
  54 // ---------------------------------------------------------------------------
  55
  56 export {
  57   segmentValidatorFactory
  58 }
  59
  60 // ---------------------------------------------------------------------------
  61
  62 function fetchSha256Segments (url: string) {
  63   return fetch(url)
  64     .then(res => res.json() as Promise<SegmentsJSON>)
  65     .catch(err => {
  66       console.error('Cannot get sha256 segments', err)
  67       return {}
  68     })
  69 }
  70
  71 function sha256 (data?: ArrayBuffer) {
  72   if (!data) return undefined
  73
  74   return window.crypto.subtle.digest('SHA-256', data)
  75 }
  76
  77 // Thanks: https://stackoverflow.com/a/53307879
  78 function bufferToEx (buffer?: ArrayBuffer) {
  79   if (!buffer) return ''
  80
  81   let s = ''
  82   const h = '0123456789abcdef'
  83   const o = new Uint8Array(buffer)
  84
  85   o.forEach((v: any) => s += h[ v >> 4 ] + h[ v & 15 ])
  86
  87   return s
  88 }