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

   1 import { wait } from '@root-helpers/utils'
   2 import { Segment } from 'p2p-media-loader-core'
   3 import { basename } from 'path'
   4
   5 type SegmentsJSON = { [filename: string]: string | { [byterange: string]: string } }
   6
   7 const maxRetries = 3
   8
   9 function segmentValidatorFactory (segmentsSha256Url: string) {
  10   let segmentsJSON = fetchSha256Segments(segmentsSha256Url)
  11   const regex = /bytes=(\d+)-(\d+)/
  12
  13   return async function segmentValidator (segment: Segment, retry = 1) {
  14     const filename = basename(segment.url)
  15
  16     const segmentValue = (await segmentsJSON)[filename]
  17
  18     if (!segmentValue && retry > maxRetries) {
  19       throw new Error(`Unknown segment name ${filename} in segment validator`)
  20     }
  21
  22     if (!segmentValue) {
  23       await wait(1000)
  24
  25       console.log('Refetching sha segments for %s.', filename)
  26
  27       segmentsJSON = fetchSha256Segments(segmentsSha256Url)
  28       await segmentValidator(segment, retry + 1)
  29
  30       return
  31     }
  32
  33     let hashShouldBe: string
  34     let range = ''
  35
  36     if (typeof segmentValue === 'string') {
  37       hashShouldBe = segmentValue
  38     } else {
  39       const captured = regex.exec(segment.range)
  40       range = captured[1] + '-' + captured[2]
  41
  42       hashShouldBe = segmentValue[range]
  43     }
  44
  45     if (hashShouldBe === undefined) {
  46       throw new Error(`Unknown segment name ${filename}/${range} in segment validator`)
  47     }
  48
  49     const calculatedSha = await sha256Hex(segment.data)
  50     if (calculatedSha !== hashShouldBe) {
  51       throw new Error(
  52         `Hashes does not correspond for segment ${filename}/${range}` +
  53         `(expected: ${hashShouldBe} instead of ${calculatedSha})`
  54       )
  55     }
  56   }
  57 }
  58
  59 // ---------------------------------------------------------------------------
  60
  61 export {
  62   segmentValidatorFactory
  63 }
  64
  65 // ---------------------------------------------------------------------------
  66
  67 function fetchSha256Segments (url: string) {
  68   return fetch(url)
  69     .then(res => res.json() as Promise<SegmentsJSON>)
  70     .catch(err => {
  71       console.error('Cannot get sha256 segments', err)
  72       return {}
  73     })
  74 }
  75
  76 async function sha256Hex (data?: ArrayBuffer) {
  77   if (!data) return undefined
  78
  79   if (window.crypto.subtle) {
  80     return window.crypto.subtle.digest('SHA-256', data)
  81       .then(data => bufferToHex(data))
  82   }
  83
  84   // Fallback for non HTTPS context
  85   const shaModule = await import('sha.js')
  86   return new shaModule.sha256().update(Buffer.from(data)).digest('hex')
  87 }
  88
  89 // Thanks: https://stackoverflow.com/a/53307879
  90 function bufferToHex (buffer?: ArrayBuffer) {
  91   if (!buffer) return ''
  92
  93   let s = ''
  94   const h = '0123456789abcdef'
  95   const o = new Uint8Array(buffer)
  96
  97   o.forEach((v: any) => s += h[ v >> 4 ] + h[ v & 15 ])
  98
  99   return s
 100 }