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Then, to achieve compatibility with outdated Node.js versions (`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Hopefully, not — dropping support for outdated Node.js versions should be fine nowdays, and that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