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529 lines
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Markdown
529 lines
20 KiB
Markdown
# ssri [](https://npm.im/ssri) [](https://npm.im/ssri) [](https://travis-ci.org/npm/ssri) [](https://ci.appveyor.com/project/npm/ssri) [](https://coveralls.io/github/npm/ssri?branch=latest)
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[`ssri`](https://github.com/npm/ssri), short for Standard Subresource
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Integrity, is a Node.js utility for parsing, manipulating, serializing,
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generating, and verifying [Subresource
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Integrity](https://w3c.github.io/webappsec/specs/subresourceintegrity/) hashes.
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## Install
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`$ npm install --save ssri`
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## Table of Contents
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* [Example](#example)
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* [Features](#features)
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* [Contributing](#contributing)
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* [API](#api)
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* Parsing & Serializing
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* [`parse`](#parse)
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* [`stringify`](#stringify)
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* [`Integrity#concat`](#integrity-concat)
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* [`Integrity#merge`](#integrity-merge)
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* [`Integrity#toString`](#integrity-to-string)
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* [`Integrity#toJSON`](#integrity-to-json)
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* [`Integrity#match`](#integrity-match)
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* [`Integrity#pickAlgorithm`](#integrity-pick-algorithm)
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* [`Integrity#hexDigest`](#integrity-hex-digest)
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* Integrity Generation
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* [`fromHex`](#from-hex)
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* [`fromData`](#from-data)
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* [`fromStream`](#from-stream)
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* [`create`](#create)
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* Integrity Verification
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* [`checkData`](#check-data)
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* [`checkStream`](#check-stream)
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* [`integrityStream`](#integrity-stream)
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### Example
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```javascript
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const ssri = require('ssri')
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const integrity = 'sha512-9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A==?foo'
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// Parsing and serializing
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const parsed = ssri.parse(integrity)
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ssri.stringify(parsed) // === integrity (works on non-Integrity objects)
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parsed.toString() // === integrity
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// Async stream functions
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ssri.checkStream(fs.createReadStream('./my-file'), integrity).then(...)
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ssri.fromStream(fs.createReadStream('./my-file')).then(sri => {
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sri.toString() === integrity
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})
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fs.createReadStream('./my-file').pipe(ssri.createCheckerStream(sri))
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// Sync data functions
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ssri.fromData(fs.readFileSync('./my-file')) // === parsed
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ssri.checkData(fs.readFileSync('./my-file'), integrity) // => 'sha512'
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```
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### Features
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* Parses and stringifies SRI strings.
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* Generates SRI strings from raw data or Streams.
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* Strict standard compliance.
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* `?foo` metadata option support.
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* Multiple entries for the same algorithm.
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* Object-based integrity hash manipulation.
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* Small footprint: no dependencies, concise implementation.
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* Full test coverage.
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* Customizable algorithm picker.
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### Contributing
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The ssri team enthusiastically welcomes contributions and project participation!
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There's a bunch of things you can do if you want to contribute! The [Contributor
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Guide](CONTRIBUTING.md) has all the information you need for everything from
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reporting bugs to contributing entire new features. Please don't hesitate to
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jump in if you'd like to, or even ask us questions if something isn't clear.
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### API
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#### <a name="parse"></a> `> ssri.parse(sri, [opts]) -> Integrity`
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Parses `sri` into an `Integrity` data structure. `sri` can be an integrity
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string, an `Hash`-like with `digest` and `algorithm` fields and an optional
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`options` field, or an `Integrity`-like object. The resulting object will be an
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`Integrity` instance that has this shape:
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```javascript
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{
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'sha1': [{algorithm: 'sha1', digest: 'deadbeef', options: []}],
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'sha512': [
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{algorithm: 'sha512', digest: 'c0ffee', options: []},
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{algorithm: 'sha512', digest: 'bad1dea', options: ['foo']}
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],
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}
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```
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If `opts.single` is truthy, a single `Hash` object will be returned. That is, a
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single object that looks like `{algorithm, digest, options}`, as opposed to a
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larger object with multiple of these.
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If `opts.strict` is truthy, the resulting object will be filtered such that
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it strictly follows the Subresource Integrity spec, throwing away any entries
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with any invalid components. This also means a restricted set of algorithms
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will be used -- the spec limits them to `sha256`, `sha384`, and `sha512`.
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Strict mode is recommended if the integrity strings are intended for use in
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browsers, or in other situations where strict adherence to the spec is needed.
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##### Example
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```javascript
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ssri.parse('sha512-9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A==?foo') // -> Integrity object
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```
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#### <a name="stringify"></a> `> ssri.stringify(sri, [opts]) -> String`
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This function is identical to [`Integrity#toString()`](#integrity-to-string),
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except it can be used on _any_ object that [`parse`](#parse) can handle -- that
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is, a string, an `Hash`-like, or an `Integrity`-like.
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The `opts.sep` option defines the string to use when joining multiple entries
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together. To be spec-compliant, this _must_ be whitespace. The default is a
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single space (`' '`).
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If `opts.strict` is true, the integrity string will be created using strict
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parsing rules. See [`ssri.parse`](#parse).
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##### Example
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```javascript
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// Useful for cleaning up input SRI strings:
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ssri.stringify('\n\rsha512-foo\n\t\tsha384-bar')
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// -> 'sha512-foo sha384-bar'
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// Hash-like: only a single entry.
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ssri.stringify({
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algorithm: 'sha512',
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digest:'9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A==',
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options: ['foo']
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})
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// ->
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// 'sha512-9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A==?foo'
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// Integrity-like: full multi-entry syntax. Similar to output of `ssri.parse`
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ssri.stringify({
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'sha512': [
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{
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algorithm: 'sha512',
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digest:'9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A==',
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options: ['foo']
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}
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]
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})
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// ->
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// 'sha512-9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A==?foo'
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```
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#### <a name="integrity-concat"></a> `> Integrity#concat(otherIntegrity, [opts]) -> Integrity`
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Concatenates an `Integrity` object with another IntegrityLike, or an integrity
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string.
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This is functionally equivalent to concatenating the string format of both
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integrity arguments, and calling [`ssri.parse`](#ssri-parse) on the new string.
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If `opts.strict` is true, the new `Integrity` will be created using strict
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parsing rules. See [`ssri.parse`](#parse).
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##### Example
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```javascript
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// This will combine the integrity checks for two different versions of
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// your index.js file so you can use a single integrity string and serve
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// either of these to clients, from a single `<script>` tag.
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const desktopIntegrity = ssri.fromData(fs.readFileSync('./index.desktop.js'))
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const mobileIntegrity = ssri.fromData(fs.readFileSync('./index.mobile.js'))
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// Note that browsers (and ssri) will succeed as long as ONE of the entries
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// for the *prioritized* algorithm succeeds. That is, in order for this fallback
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// to work, both desktop and mobile *must* use the same `algorithm` values.
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desktopIntegrity.concat(mobileIntegrity)
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```
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#### <a name="integrity-merge"></a> `> Integrity#merge(otherIntegrity, [opts])`
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Safely merges another IntegrityLike or integrity string into an `Integrity`
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object.
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If the other integrity value has any algorithms in common with the current
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object, then the hash digests must match, or an error is thrown.
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Any new hashes will be added to the current object's set.
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This is useful when an integrity value may be upgraded with a stronger
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algorithm, you wish to prevent accidentally suppressing integrity errors by
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overwriting the expected integrity value.
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##### Example
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```javascript
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const data = fs.readFileSync('data.txt')
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// integrity.txt contains 'sha1-X1UT+IIv2+UUWvM7ZNjZcNz5XG4='
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// because we were young, and didn't realize sha1 would not last
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const expectedIntegrity = ssri.parse(fs.readFileSync('integrity.txt', 'utf8'))
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const match = ssri.checkData(data, expectedIntegrity, {
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algorithms: ['sha512', 'sha1']
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})
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if (!match) {
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throw new Error('data corrupted or something!')
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}
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// get a stronger algo!
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if (match && match.algorithm !== 'sha512') {
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const updatedIntegrity = ssri.fromData(data, { algorithms: ['sha512'] })
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expectedIntegrity.merge(updatedIntegrity)
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fs.writeFileSync('integrity.txt', expectedIntegrity.toString())
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// file now contains
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// 'sha1-X1UT+IIv2+UUWvM7ZNjZcNz5XG4= sha512-yzd8ELD1piyANiWnmdnpCL5F52f10UfUdEkHywVZeqTt0ymgrxR63Qz0GB7TKPoeeZQmWCaz7T1+9vBnypkYWg=='
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}
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```
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#### <a name="integrity-to-string"></a> `> Integrity#toString([opts]) -> String`
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Returns the string representation of an `Integrity` object. All hash entries
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will be concatenated in the string by `opts.sep`, which defaults to `' '`.
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If you want to serialize an object that didn't come from an `ssri` function,
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use [`ssri.stringify()`](#stringify).
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If `opts.strict` is true, the integrity string will be created using strict
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parsing rules. See [`ssri.parse`](#parse).
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##### Example
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```javascript
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const integrity = 'sha512-9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A==?foo'
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ssri.parse(integrity).toString() === integrity
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```
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#### <a name="integrity-to-json"></a> `> Integrity#toJSON() -> String`
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Returns the string representation of an `Integrity` object. All hash entries
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will be concatenated in the string by `' '`.
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This is a convenience method so you can pass an `Integrity` object directly to `JSON.stringify`.
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For more info check out [toJSON() behavior on mdn](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#toJSON%28%29_behavior).
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##### Example
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```javascript
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const integrity = '"sha512-9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A==?foo"'
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JSON.stringify(ssri.parse(integrity)) === integrity
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```
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#### <a name="integrity-match"></a> `> Integrity#match(sri, [opts]) -> Hash | false`
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Returns the matching (truthy) hash if `Integrity` matches the argument passed as
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`sri`, which can be anything that [`parse`](#parse) will accept. `opts` will be
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passed through to `parse` and [`pickAlgorithm()`](#integrity-pick-algorithm).
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##### Example
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```javascript
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const integrity = 'sha512-9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A=='
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ssri.parse(integrity).match(integrity)
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// Hash {
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// digest: '9KhgCRIx/AmzC8xqYJTZRrnO8OW2Pxyl2DIMZSBOr0oDvtEFyht3xpp71j/r/pAe1DM+JI/A+line3jUBgzQ7A=='
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// algorithm: 'sha512'
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// }
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ssri.parse(integrity).match('sha1-deadbeef')
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// false
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```
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#### <a name="integrity-pick-algorithm"></a> `> Integrity#pickAlgorithm([opts]) -> String`
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Returns the "best" algorithm from those available in the integrity object.
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If `opts.pickAlgorithm` is provided, it will be passed two algorithms as
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arguments. ssri will prioritize whichever of the two algorithms is returned by
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this function. Note that the function may be called multiple times, and it
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**must** return one of the two algorithms provided. By default, ssri will make
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a best-effort to pick the strongest/most reliable of the given algorithms. It
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may intentionally deprioritize algorithms with known vulnerabilities.
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##### Example
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```javascript
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ssri.parse('sha1-WEakDigEST sha512-yzd8ELD1piyANiWnmdnpCL5F52f10UfUdEkHywVZeqTt0ymgrxR63Qz0GB7TKPoeeZQmWCaz7T1').pickAlgorithm() // sha512
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```
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#### <a name="integrity-hex-digest"></a> `> Integrity#hexDigest() -> String`
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`Integrity` is assumed to be either a single-hash `Integrity` instance, or a
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`Hash` instance. Returns its `digest`, converted to a hex representation of the
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base64 data.
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##### Example
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```javascript
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ssri.parse('sha1-deadbeef').hexDigest() // '75e69d6de79f'
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```
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#### <a name="from-hex"></a> `> ssri.fromHex(hexDigest, algorithm, [opts]) -> Integrity`
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Creates an `Integrity` object with a single entry, based on a hex-formatted
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hash. This is a utility function to help convert existing shasums to the
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Integrity format, and is roughly equivalent to something like:
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```javascript
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algorithm + '-' + Buffer.from(hexDigest, 'hex').toString('base64')
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```
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`opts.options` may optionally be passed in: it must be an array of option
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strings that will be added to all generated integrity hashes generated by
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`fromData`. This is a loosely-specified feature of SRIs, and currently has no
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specified semantics besides being `?`-separated. Use at your own risk, and
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probably avoid if your integrity strings are meant to be used with browsers.
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If `opts.strict` is true, the integrity object will be created using strict
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parsing rules. See [`ssri.parse`](#parse).
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If `opts.single` is true, a single `Hash` object will be returned.
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##### Example
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```javascript
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ssri.fromHex('75e69d6de79f', 'sha1').toString() // 'sha1-deadbeef'
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```
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#### <a name="from-data"></a> `> ssri.fromData(data, [opts]) -> Integrity`
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Creates an `Integrity` object from either string or `Buffer` data, calculating
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all the requested hashes and adding any specified options to the object.
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`opts.algorithms` determines which algorithms to generate hashes for. All
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results will be included in a single `Integrity` object. The default value for
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`opts.algorithms` is `['sha512']`. All algorithm strings must be hashes listed
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in `crypto.getHashes()` for the host Node.js platform.
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`opts.options` may optionally be passed in: it must be an array of option
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strings that will be added to all generated integrity hashes generated by
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`fromData`. This is a loosely-specified feature of SRIs, and currently has no
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specified semantics besides being `?`-separated. Use at your own risk, and
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probably avoid if your integrity strings are meant to be used with browsers.
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If `opts.strict` is true, the integrity object will be created using strict
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parsing rules. See [`ssri.parse`](#parse).
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##### Example
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```javascript
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const integrityObj = ssri.fromData('foobarbaz', {
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algorithms: ['sha256', 'sha384', 'sha512']
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})
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integrity.toString('\n')
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// ->
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// sha256-l981iLWj8kurw4UbNy8Lpxqdzd7UOxS50Glhv8FwfZ0=
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// sha384-irnCxQ0CfQhYGlVAUdwTPC9bF3+YWLxlaDGM4xbYminxpbXEq+D+2GCEBTxcjES9
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// sha512-yzd8ELD1piyANiWnmdnpCL5F52f10UfUdEkHywVZeqTt0ymgrxR63Qz0GB7TKPoeeZQmWCaz7T1+9vBnypkYWg==
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```
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#### <a name="from-stream"></a> `> ssri.fromStream(stream, [opts]) -> Promise<Integrity>`
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Returns a Promise of an Integrity object calculated by reading data from
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a given `stream`.
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It accepts both `opts.algorithms` and `opts.options`, which are documented as
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part of [`ssri.fromData`](#from-data).
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Additionally, `opts.Promise` may be passed in to inject a Promise library of
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choice. By default, ssri will use Node's built-in Promises.
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If `opts.strict` is true, the integrity object will be created using strict
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parsing rules. See [`ssri.parse`](#parse).
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##### Example
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```javascript
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ssri.fromStream(fs.createReadStream('index.js'), {
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algorithms: ['sha1', 'sha512']
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}).then(integrity => {
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return ssri.checkStream(fs.createReadStream('index.js'), integrity)
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}) // succeeds
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```
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#### <a name="create"></a> `> ssri.create([opts]) -> <Hash>`
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Returns a Hash object with `update(<Buffer or string>[,enc])` and `digest()` methods.
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The Hash object provides the same methods as [crypto class Hash](https://nodejs.org/dist/latest-v6.x/docs/api/crypto.html#crypto_class_hash).
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`digest()` accepts no arguments and returns an Integrity object calculated by reading data from
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calls to update.
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It accepts both `opts.algorithms` and `opts.options`, which are documented as
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part of [`ssri.fromData`](#from-data).
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If `opts.strict` is true, the integrity object will be created using strict
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parsing rules. See [`ssri.parse`](#parse).
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##### Example
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```javascript
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const integrity = ssri.create().update('foobarbaz').digest()
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integrity.toString()
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// ->
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// sha512-yzd8ELD1piyANiWnmdnpCL5F52f10UfUdEkHywVZeqTt0ymgrxR63Qz0GB7TKPoeeZQmWCaz7T1+9vBnypkYWg==
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```
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#### <a name="check-data"></a> `> ssri.checkData(data, sri, [opts]) -> Hash|false`
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Verifies `data` integrity against an `sri` argument. `data` may be either a
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`String` or a `Buffer`, and `sri` can be any subresource integrity
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representation that [`ssri.parse`](#parse) can handle.
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If verification succeeds, `checkData` will return the name of the algorithm that
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was used for verification (a truthy value). Otherwise, it will return `false`.
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If `opts.pickAlgorithm` is provided, it will be used by
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[`Integrity#pickAlgorithm`](#integrity-pick-algorithm) when deciding which of
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the available digests to match against.
|
|
|
|
If `opts.error` is true, and verification fails, `checkData` will throw either
|
|
an `EBADSIZE` or an `EINTEGRITY` error, instead of just returning false.
|
|
|
|
##### Example
|
|
|
|
```javascript
|
|
const data = fs.readFileSync('index.js')
|
|
ssri.checkData(data, ssri.fromData(data)) // -> 'sha512'
|
|
ssri.checkData(data, 'sha256-l981iLWj8kurw4UbNy8Lpxqdzd7UOxS50Glhv8FwfZ0')
|
|
ssri.checkData(data, 'sha1-BaDDigEST') // -> false
|
|
ssri.checkData(data, 'sha1-BaDDigEST', {error: true}) // -> Error! EINTEGRITY
|
|
```
|
|
|
|
#### <a name="check-stream"></a> `> ssri.checkStream(stream, sri, [opts]) -> Promise<Hash>`
|
|
|
|
Verifies the contents of `stream` against an `sri` argument. `stream` will be
|
|
consumed in its entirety by this process. `sri` can be any subresource integrity
|
|
representation that [`ssri.parse`](#parse) can handle.
|
|
|
|
`checkStream` will return a Promise that either resolves to the
|
|
`Hash` that succeeded verification, or, if the verification fails
|
|
or an error happens with `stream`, the Promise will be rejected.
|
|
|
|
If the Promise is rejected because verification failed, the returned error will
|
|
have `err.code` as `EINTEGRITY`.
|
|
|
|
If `opts.size` is given, it will be matched against the stream size. An error
|
|
with `err.code` `EBADSIZE` will be returned by a rejection if the expected size
|
|
and actual size fail to match.
|
|
|
|
If `opts.pickAlgorithm` is provided, it will be used by
|
|
[`Integrity#pickAlgorithm`](#integrity-pick-algorithm) when deciding which of
|
|
the available digests to match against.
|
|
|
|
##### Example
|
|
|
|
```javascript
|
|
const integrity = ssri.fromData(fs.readFileSync('index.js'))
|
|
|
|
ssri.checkStream(
|
|
fs.createReadStream('index.js'),
|
|
integrity
|
|
)
|
|
// ->
|
|
// Promise<{
|
|
// algorithm: 'sha512',
|
|
// digest: 'sha512-yzd8ELD1piyANiWnmdnpCL5F52f10UfUdEkHywVZeqTt0ymgrxR63Qz0GB7TKPoeeZQmWCaz7T1'
|
|
// }>
|
|
|
|
ssri.checkStream(
|
|
fs.createReadStream('index.js'),
|
|
'sha256-l981iLWj8kurw4UbNy8Lpxqdzd7UOxS50Glhv8FwfZ0'
|
|
) // -> Promise<Hash>
|
|
|
|
ssri.checkStream(
|
|
fs.createReadStream('index.js'),
|
|
'sha1-BaDDigEST'
|
|
) // -> Promise<Error<{code: 'EINTEGRITY'}>>
|
|
```
|
|
|
|
#### <a name="integrity-stream"></a> `> integrityStream([opts]) -> IntegrityStream`
|
|
|
|
Returns a `Transform` stream that data can be piped through in order to generate
|
|
and optionally check data integrity for piped data. When the stream completes
|
|
successfully, it emits `size` and `integrity` events, containing the total
|
|
number of bytes processed and a calculated `Integrity` instance based on stream
|
|
data, respectively.
|
|
|
|
If `opts.algorithms` is passed in, the listed algorithms will be calculated when
|
|
generating the final `Integrity` instance. The default is `['sha512']`.
|
|
|
|
If `opts.single` is passed in, a single `Hash` instance will be returned.
|
|
|
|
If `opts.integrity` is passed in, it should be an `integrity` value understood
|
|
by [`parse`](#parse) that the stream will check the data against. If
|
|
verification succeeds, the integrity stream will emit a `verified` event whose
|
|
value is a single `Hash` object that is the one that succeeded verification. If
|
|
verification fails, the stream will error with an `EINTEGRITY` error code.
|
|
|
|
If `opts.size` is given, it will be matched against the stream size. An error
|
|
with `err.code` `EBADSIZE` will be emitted by the stream if the expected size
|
|
and actual size fail to match.
|
|
|
|
If `opts.pickAlgorithm` is provided, it will be passed two algorithms as
|
|
arguments. ssri will prioritize whichever of the two algorithms is returned by
|
|
this function. Note that the function may be called multiple times, and it
|
|
**must** return one of the two algorithms provided. By default, ssri will make
|
|
a best-effort to pick the strongest/most reliable of the given algorithms. It
|
|
may intentionally deprioritize algorithms with known vulnerabilities.
|
|
|
|
##### Example
|
|
|
|
```javascript
|
|
const integrity = ssri.fromData(fs.readFileSync('index.js'))
|
|
fs.createReadStream('index.js')
|
|
.pipe(ssri.integrityStream({integrity}))
|
|
```
|