157 lines
8.1 KiB
Markdown
157 lines
8.1 KiB
Markdown
# safer-buffer [![travis][travis-image]][travis-url] [![npm][npm-image]][npm-url] [![javascript style guide][standard-image]][standard-url] [![Security Responsible Disclosure][secuirty-image]][secuirty-url]
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[travis-image]: https://travis-ci.org/ChALkeR/safer-buffer.svg?branch=master
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[travis-url]: https://travis-ci.org/ChALkeR/safer-buffer
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[npm-image]: https://img.shields.io/npm/v/safer-buffer.svg
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[npm-url]: https://npmjs.org/package/safer-buffer
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[standard-image]: https://img.shields.io/badge/code_style-standard-brightgreen.svg
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[standard-url]: https://standardjs.com
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[secuirty-image]: https://img.shields.io/badge/Security-Responsible%20Disclosure-green.svg
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[secuirty-url]: https://github.com/nodejs/security-wg/blob/master/processes/responsible_disclosure_template.md
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Modern Buffer API polyfill without footguns, working on Node.js from 0.8 to current.
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## How to use?
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First, port all `Buffer()` and `new Buffer()` calls to `Buffer.alloc()` and `Buffer.from()` API.
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Then, to achieve compatibility with outdated Node.js versions (`<4.5.0` and 5.x `<5.9.0`), use
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`const Buffer = require('safer-buffer').Buffer` in all files where you make calls to the new
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Buffer API. _Use `var` instead of `const` if you need that for your Node.js version range support._
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Also, see the
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[porting Buffer](https://github.com/ChALkeR/safer-buffer/blob/master/Porting-Buffer.md) guide.
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## Do I need it?
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Hopefully, not — dropping support for outdated Node.js versions should be fine nowdays, and that
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is the recommended path forward. You _do_ need to port to the `Buffer.alloc()` and `Buffer.from()`
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though.
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See the [porting guide](https://github.com/ChALkeR/safer-buffer/blob/master/Porting-Buffer.md)
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for a better description.
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## Why not [safe-buffer](https://npmjs.com/safe-buffer)?
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_In short: while `safe-buffer` serves as a polyfill for the new API, it allows old API usage and
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itself contains footguns._
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`safe-buffer` could be used safely to get the new API while still keeping support for older
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Node.js versions (like this module), but while analyzing ecosystem usage of the old Buffer API
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I found out that `safe-buffer` is itself causing problems in some cases.
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For example, consider the following snippet:
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```console
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$ cat example.unsafe.js
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console.log(Buffer(20))
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$ ./node-v6.13.0-linux-x64/bin/node example.unsafe.js
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<Buffer 0a 00 00 00 00 00 00 00 28 13 de 02 00 00 00 00 05 00 00 00>
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$ standard example.unsafe.js
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standard: Use JavaScript Standard Style (https://standardjs.com)
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/home/chalker/repo/safer-buffer/example.unsafe.js:2:13: 'Buffer()' was deprecated since v6. Use 'Buffer.alloc()' or 'Buffer.from()' (use 'https://www.npmjs.com/package/safe-buffer' for '<4.5.0') instead.
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```
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This is allocates and writes to console an uninitialized chunk of memory.
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[standard](https://www.npmjs.com/package/standard) linter (among others) catch that and warn people
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to avoid using unsafe API.
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Let's now throw in `safe-buffer`!
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```console
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$ cat example.safe-buffer.js
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const Buffer = require('safe-buffer').Buffer
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console.log(Buffer(20))
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$ standard example.safe-buffer.js
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$ ./node-v6.13.0-linux-x64/bin/node example.safe-buffer.js
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<Buffer 08 00 00 00 00 00 00 00 28 58 01 82 fe 7f 00 00 00 00 00 00>
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```
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See the problem? Adding in `safe-buffer` _magically removes the lint warning_, but the behavior
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remains identiсal to what we had before, and when launched on Node.js 6.x LTS — this dumps out
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chunks of uninitialized memory.
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_And this code will still emit runtime warnings on Node.js 10.x and above._
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That was done by design. I first considered changing `safe-buffer`, prohibiting old API usage or
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emitting warnings on it, but that significantly diverges from `safe-buffer` design. After some
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discussion, it was decided to move my approach into a separate package, and _this is that separate
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package_.
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This footgun is not imaginary — I observed top-downloaded packages doing that kind of thing,
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«fixing» the lint warning by blindly including `safe-buffer` without any actual changes.
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Also in some cases, even if the API _was_ migrated to use of safe Buffer API — a random pull request
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can bring unsafe Buffer API usage back to the codebase by adding new calls — and that could go
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unnoticed even if you have a linter prohibiting that (becase of the reason stated above), and even
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pass CI. _I also observed that being done in popular packages._
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Some examples:
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* [webdriverio](https://github.com/webdriverio/webdriverio/commit/05cbd3167c12e4930f09ef7cf93b127ba4effae4#diff-124380949022817b90b622871837d56cR31)
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(a module with 548 759 downloads/month),
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* [websocket-stream](https://github.com/maxogden/websocket-stream/commit/c9312bd24d08271687d76da0fe3c83493871cf61)
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(218 288 d/m, fix in [maxogden/websocket-stream#142](https://github.com/maxogden/websocket-stream/pull/142)),
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* [node-serialport](https://github.com/node-serialport/node-serialport/commit/e8d9d2b16c664224920ce1c895199b1ce2def48c)
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(113 138 d/m, fix in [node-serialport/node-serialport#1510](https://github.com/node-serialport/node-serialport/pull/1510)),
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* [karma](https://github.com/karma-runner/karma/commit/3d94b8cf18c695104ca195334dc75ff054c74eec)
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(3 973 193 d/m, fix in [karma-runner/karma#2947](https://github.com/karma-runner/karma/pull/2947)),
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* [spdy-transport](https://github.com/spdy-http2/spdy-transport/commit/5375ac33f4a62a4f65bcfc2827447d42a5dbe8b1)
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(5 970 727 d/m, fix in [spdy-http2/spdy-transport#53](https://github.com/spdy-http2/spdy-transport/pull/53)).
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* And there are a lot more over the ecosystem.
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I filed a PR at
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[mysticatea/eslint-plugin-node#110](https://github.com/mysticatea/eslint-plugin-node/pull/110) to
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partially fix that (for cases when that lint rule is used), but it is a semver-major change for
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linter rules and presets, so it would take significant time for that to reach actual setups.
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_It also hasn't been released yet (2018-03-20)._
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Also, `safer-buffer` discourages the usage of `.allocUnsafe()`, which is often done by a mistake.
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It still supports it with an explicit concern barier, by placing it under
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`require('safer-buffer/dangereous')`.
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## But isn't throwing bad?
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Not really. It's an error that could be noticed and fixed early, instead of causing havoc later like
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unguarded `new Buffer()` calls that end up receiving user input can do.
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This package affects only the files where `var Buffer = require('safer-buffer').Buffer` was done, so
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it is really simple to keep track of things and make sure that you don't mix old API usage with that.
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Also, CI should hint anything that you might have missed.
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New commits, if tested, won't land new usage of unsafe Buffer API this way.
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_Node.js 10.x also deals with that by printing a runtime depecation warning._
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### Would it affect third-party modules?
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No, unless you explicitly do an awful thing like monkey-patching or overriding the built-in `Buffer`.
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Don't do that.
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### But I don't want throwing…
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That is also fine!
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Also, it could be better in some cases when you don't comprehensive enough test coverage.
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In that case — just don't override `Buffer` and use
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`var SaferBuffer = require('safer-buffer').Buffer` instead.
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That way, everything using `Buffer` natively would still work, but there would be two drawbacks:
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* `Buffer.from`/`Buffer.alloc` won't be polyfilled — use `SaferBuffer.from` and
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`SaferBuffer.alloc` instead.
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* You are still open to accidentally using the insecure deprecated API — use a linter to catch that.
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Note that using a linter to catch accidential `Buffer` constructor usage in this case is strongly
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recommended. `Buffer` is not overriden in this usecase, so linters won't get confused.
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## «Without footguns»?
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Well, it is still possible to do _some_ things with `Buffer` API, e.g. accessing `.buffer` property
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on older versions and duping things from there. You shouldn't do that in your code, probabably.
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The intention is to remove the most significant footguns that affect lots of packages in the
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ecosystem, and to do it in the proper way.
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Also, this package doesn't protect against security issues affecting some Node.js versions, so for
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usage in your own production code, it is still recommended to update to a Node.js version
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[supported by upstream](https://github.com/nodejs/release#release-schedule).
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