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471 lines
14 KiB
471 lines
14 KiB
'use strict'
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const crypto = require('crypto')
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const MiniPass = require('minipass')
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const SPEC_ALGORITHMS = ['sha256', 'sha384', 'sha512']
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// TODO: this should really be a hardcoded list of algorithms we support,
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// rather than [a-z0-9].
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const BASE64_REGEX = /^[a-z0-9+/]+(?:=?=?)$/i
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const SRI_REGEX = /^([a-z0-9]+)-([^?]+)([?\S*]*)$/
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const STRICT_SRI_REGEX = /^([a-z0-9]+)-([A-Za-z0-9+/=]{44,88})(\?[\x21-\x7E]*)?$/
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const VCHAR_REGEX = /^[\x21-\x7E]+$/
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const defaultOpts = {
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algorithms: ['sha512'],
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error: false,
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options: [],
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pickAlgorithm: getPrioritizedHash,
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sep: ' ',
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single: false,
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strict: false
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}
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const ssriOpts = (opts = {}) => ({ ...defaultOpts, ...opts })
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const getOptString = options => !options || !options.length
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? ''
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: `?${options.join('?')}`
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const _onEnd = Symbol('_onEnd')
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const _getOptions = Symbol('_getOptions')
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class IntegrityStream extends MiniPass {
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constructor (opts) {
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super()
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this.size = 0
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this.opts = opts
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// may be overridden later, but set now for class consistency
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this[_getOptions]()
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// options used for calculating stream. can't be changed.
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const { algorithms = defaultOpts.algorithms } = opts
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this.algorithms = Array.from(
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new Set(algorithms.concat(this.algorithm ? [this.algorithm] : []))
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)
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this.hashes = this.algorithms.map(crypto.createHash)
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}
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[_getOptions] () {
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const {
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integrity,
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size,
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options
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} = { ...defaultOpts, ...this.opts }
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// For verification
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this.sri = integrity ? parse(integrity, this.opts) : null
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this.expectedSize = size
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this.goodSri = this.sri ? !!Object.keys(this.sri).length : false
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this.algorithm = this.goodSri ? this.sri.pickAlgorithm(this.opts) : null
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this.digests = this.goodSri ? this.sri[this.algorithm] : null
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this.optString = getOptString(options)
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}
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emit (ev, data) {
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if (ev === 'end') this[_onEnd]()
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return super.emit(ev, data)
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}
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write (data) {
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this.size += data.length
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this.hashes.forEach(h => h.update(data))
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return super.write(data)
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}
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[_onEnd] () {
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if (!this.goodSri) {
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this[_getOptions]()
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}
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const newSri = parse(this.hashes.map((h, i) => {
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return `${this.algorithms[i]}-${h.digest('base64')}${this.optString}`
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}).join(' '), this.opts)
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// Integrity verification mode
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const match = this.goodSri && newSri.match(this.sri, this.opts)
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if (typeof this.expectedSize === 'number' && this.size !== this.expectedSize) {
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const err = new Error(`stream size mismatch when checking ${this.sri}.\n Wanted: ${this.expectedSize}\n Found: ${this.size}`)
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err.code = 'EBADSIZE'
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err.found = this.size
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err.expected = this.expectedSize
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err.sri = this.sri
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this.emit('error', err)
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} else if (this.sri && !match) {
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const err = new Error(`${this.sri} integrity checksum failed when using ${this.algorithm}: wanted ${this.digests} but got ${newSri}. (${this.size} bytes)`)
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err.code = 'EINTEGRITY'
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err.found = newSri
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err.expected = this.digests
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err.algorithm = this.algorithm
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err.sri = this.sri
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this.emit('error', err)
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} else {
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this.emit('size', this.size)
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this.emit('integrity', newSri)
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match && this.emit('verified', match)
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}
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}
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}
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class Hash {
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get isHash () { return true }
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constructor (hash, opts) {
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opts = ssriOpts(opts)
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const strict = !!opts.strict
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this.source = hash.trim()
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// set default values so that we make V8 happy to
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// always see a familiar object template.
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this.digest = ''
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this.algorithm = ''
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this.options = []
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// 3.1. Integrity metadata (called "Hash" by ssri)
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// https://w3c.github.io/webappsec-subresource-integrity/#integrity-metadata-description
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const match = this.source.match(
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strict
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? STRICT_SRI_REGEX
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: SRI_REGEX
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)
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if (!match) { return }
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if (strict && !SPEC_ALGORITHMS.some(a => a === match[1])) { return }
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this.algorithm = match[1]
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this.digest = match[2]
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const rawOpts = match[3]
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if (rawOpts) {
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this.options = rawOpts.slice(1).split('?')
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}
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}
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hexDigest () {
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return this.digest && Buffer.from(this.digest, 'base64').toString('hex')
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}
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toJSON () {
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return this.toString()
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}
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toString (opts) {
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opts = ssriOpts(opts)
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if (opts.strict) {
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// Strict mode enforces the standard as close to the foot of the
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// letter as it can.
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if (!(
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// The spec has very restricted productions for algorithms.
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// https://www.w3.org/TR/CSP2/#source-list-syntax
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SPEC_ALGORITHMS.some(x => x === this.algorithm) &&
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// Usually, if someone insists on using a "different" base64, we
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// leave it as-is, since there's multiple standards, and the
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// specified is not a URL-safe variant.
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// https://www.w3.org/TR/CSP2/#base64_value
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this.digest.match(BASE64_REGEX) &&
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// Option syntax is strictly visual chars.
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// https://w3c.github.io/webappsec-subresource-integrity/#grammardef-option-expression
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// https://tools.ietf.org/html/rfc5234#appendix-B.1
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this.options.every(opt => opt.match(VCHAR_REGEX))
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)) {
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return ''
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}
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}
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const options = this.options && this.options.length
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? `?${this.options.join('?')}`
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: ''
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return `${this.algorithm}-${this.digest}${options}`
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}
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}
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class Integrity {
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get isIntegrity () { return true }
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toJSON () {
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return this.toString()
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}
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isEmpty () {
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return Object.keys(this).length === 0
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}
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toString (opts) {
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opts = ssriOpts(opts)
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let sep = opts.sep || ' '
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if (opts.strict) {
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// Entries must be separated by whitespace, according to spec.
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sep = sep.replace(/\S+/g, ' ')
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}
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return Object.keys(this).map(k => {
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return this[k].map(hash => {
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return Hash.prototype.toString.call(hash, opts)
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}).filter(x => x.length).join(sep)
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}).filter(x => x.length).join(sep)
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}
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concat (integrity, opts) {
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opts = ssriOpts(opts)
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const other = typeof integrity === 'string'
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? integrity
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: stringify(integrity, opts)
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return parse(`${this.toString(opts)} ${other}`, opts)
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}
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hexDigest () {
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return parse(this, { single: true }).hexDigest()
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}
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// add additional hashes to an integrity value, but prevent
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// *changing* an existing integrity hash.
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merge (integrity, opts) {
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opts = ssriOpts(opts)
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const other = parse(integrity, opts)
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for (const algo in other) {
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if (this[algo]) {
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if (!this[algo].find(hash =>
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other[algo].find(otherhash =>
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hash.digest === otherhash.digest))) {
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throw new Error('hashes do not match, cannot update integrity')
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}
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} else {
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this[algo] = other[algo]
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}
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}
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}
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match (integrity, opts) {
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opts = ssriOpts(opts)
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const other = parse(integrity, opts)
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const algo = other.pickAlgorithm(opts)
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return (
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this[algo] &&
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other[algo] &&
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this[algo].find(hash =>
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other[algo].find(otherhash =>
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hash.digest === otherhash.digest
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)
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)
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) || false
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}
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pickAlgorithm (opts) {
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opts = ssriOpts(opts)
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const pickAlgorithm = opts.pickAlgorithm
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const keys = Object.keys(this)
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return keys.reduce((acc, algo) => {
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return pickAlgorithm(acc, algo) || acc
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})
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}
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}
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module.exports.parse = parse
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function parse (sri, opts) {
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if (!sri) return null
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opts = ssriOpts(opts)
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if (typeof sri === 'string') {
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return _parse(sri, opts)
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} else if (sri.algorithm && sri.digest) {
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const fullSri = new Integrity()
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fullSri[sri.algorithm] = [sri]
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return _parse(stringify(fullSri, opts), opts)
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} else {
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return _parse(stringify(sri, opts), opts)
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}
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}
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function _parse (integrity, opts) {
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// 3.4.3. Parse metadata
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// https://w3c.github.io/webappsec-subresource-integrity/#parse-metadata
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if (opts.single) {
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return new Hash(integrity, opts)
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}
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const hashes = integrity.trim().split(/\s+/).reduce((acc, string) => {
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const hash = new Hash(string, opts)
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if (hash.algorithm && hash.digest) {
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const algo = hash.algorithm
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if (!acc[algo]) { acc[algo] = [] }
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acc[algo].push(hash)
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}
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return acc
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}, new Integrity())
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return hashes.isEmpty() ? null : hashes
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}
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module.exports.stringify = stringify
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function stringify (obj, opts) {
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opts = ssriOpts(opts)
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if (obj.algorithm && obj.digest) {
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return Hash.prototype.toString.call(obj, opts)
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} else if (typeof obj === 'string') {
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return stringify(parse(obj, opts), opts)
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} else {
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return Integrity.prototype.toString.call(obj, opts)
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}
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}
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module.exports.fromHex = fromHex
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function fromHex (hexDigest, algorithm, opts) {
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opts = ssriOpts(opts)
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const optString = getOptString(opts.options)
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return parse(
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`${algorithm}-${
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Buffer.from(hexDigest, 'hex').toString('base64')
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}${optString}`, opts
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)
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}
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module.exports.fromData = fromData
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function fromData (data, opts) {
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opts = ssriOpts(opts)
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const algorithms = opts.algorithms
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const optString = getOptString(opts.options)
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return algorithms.reduce((acc, algo) => {
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const digest = crypto.createHash(algo).update(data).digest('base64')
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const hash = new Hash(
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`${algo}-${digest}${optString}`,
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opts
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)
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/* istanbul ignore else - it would be VERY strange if the string we
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* just calculated with an algo did not have an algo or digest.
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*/
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if (hash.algorithm && hash.digest) {
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const algo = hash.algorithm
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if (!acc[algo]) { acc[algo] = [] }
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acc[algo].push(hash)
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}
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return acc
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}, new Integrity())
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}
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module.exports.fromStream = fromStream
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function fromStream (stream, opts) {
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opts = ssriOpts(opts)
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const istream = integrityStream(opts)
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return new Promise((resolve, reject) => {
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stream.pipe(istream)
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stream.on('error', reject)
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istream.on('error', reject)
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let sri
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istream.on('integrity', s => { sri = s })
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istream.on('end', () => resolve(sri))
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istream.on('data', () => {})
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})
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}
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module.exports.checkData = checkData
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function checkData (data, sri, opts) {
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opts = ssriOpts(opts)
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sri = parse(sri, opts)
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if (!sri || !Object.keys(sri).length) {
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if (opts.error) {
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throw Object.assign(
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new Error('No valid integrity hashes to check against'), {
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code: 'EINTEGRITY'
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}
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)
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} else {
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return false
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}
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}
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const algorithm = sri.pickAlgorithm(opts)
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const digest = crypto.createHash(algorithm).update(data).digest('base64')
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const newSri = parse({ algorithm, digest })
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const match = newSri.match(sri, opts)
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if (match || !opts.error) {
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return match
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} else if (typeof opts.size === 'number' && (data.length !== opts.size)) {
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const err = new Error(`data size mismatch when checking ${sri}.\n Wanted: ${opts.size}\n Found: ${data.length}`)
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err.code = 'EBADSIZE'
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err.found = data.length
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err.expected = opts.size
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err.sri = sri
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throw err
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} else {
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const err = new Error(`Integrity checksum failed when using ${algorithm}: Wanted ${sri}, but got ${newSri}. (${data.length} bytes)`)
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err.code = 'EINTEGRITY'
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err.found = newSri
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err.expected = sri
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err.algorithm = algorithm
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err.sri = sri
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throw err
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}
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}
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module.exports.checkStream = checkStream
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function checkStream (stream, sri, opts) {
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opts = ssriOpts(opts)
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opts.integrity = sri
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sri = parse(sri, opts)
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if (!sri || !Object.keys(sri).length) {
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return Promise.reject(Object.assign(
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new Error('No valid integrity hashes to check against'), {
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code: 'EINTEGRITY'
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}
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))
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}
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const checker = integrityStream(opts)
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return new Promise((resolve, reject) => {
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stream.pipe(checker)
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stream.on('error', reject)
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checker.on('error', reject)
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let sri
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checker.on('verified', s => { sri = s })
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checker.on('end', () => resolve(sri))
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checker.on('data', () => {})
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})
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}
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module.exports.integrityStream = integrityStream
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function integrityStream (opts = {}) {
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return new IntegrityStream(opts)
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}
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module.exports.create = createIntegrity
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function createIntegrity (opts) {
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opts = ssriOpts(opts)
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const algorithms = opts.algorithms
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const optString = getOptString(opts.options)
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const hashes = algorithms.map(crypto.createHash)
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return {
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update: function (chunk, enc) {
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hashes.forEach(h => h.update(chunk, enc))
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return this
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},
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digest: function (enc) {
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const integrity = algorithms.reduce((acc, algo) => {
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const digest = hashes.shift().digest('base64')
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const hash = new Hash(
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`${algo}-${digest}${optString}`,
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opts
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)
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/* istanbul ignore else - it would be VERY strange if the hash we
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* just calculated with an algo did not have an algo or digest.
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*/
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if (hash.algorithm && hash.digest) {
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const algo = hash.algorithm
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if (!acc[algo]) { acc[algo] = [] }
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acc[algo].push(hash)
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}
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return acc
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}, new Integrity())
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return integrity
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}
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}
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}
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const NODE_HASHES = new Set(crypto.getHashes())
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// This is a Best Effort™ at a reasonable priority for hash algos
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const DEFAULT_PRIORITY = [
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'md5', 'whirlpool', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512',
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// TODO - it's unclear _which_ of these Node will actually use as its name
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// for the algorithm, so we guesswork it based on the OpenSSL names.
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'sha3',
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'sha3-256', 'sha3-384', 'sha3-512',
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'sha3_256', 'sha3_384', 'sha3_512'
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].filter(algo => NODE_HASHES.has(algo))
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function getPrioritizedHash (algo1, algo2) {
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return DEFAULT_PRIORITY.indexOf(algo1.toLowerCase()) >= DEFAULT_PRIORITY.indexOf(algo2.toLowerCase())
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? algo1
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: algo2
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}
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