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doc-sniff

1.0.1 • Public • Published

doc-sniff

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A helper for combating incorrect content-type, aka a mime sniffing module for node.js

Motivation

So you have made a http request and got back some headers and a response body, but you just don't know if that innocent Content-Type header tells you what really goes on in its body.

Enter doc-sniff, a much simpler implementation of whatwg mime sniffing algorithm. Specifically for those responses that can't be easily distinguished via file extensions or magic numbers, eg. HTML, XML documents.

Install

npm install doc-sniff --save

Usage

var docsniff = require('doc-sniff');
 
var mime1 = docsniff(false, '<html></html>');
console.log(mime1); // text/html
 
var mime2 = docsniff('text/html', '<?xml version="1.0" encoding="UTF-8" ?><feed></feed>');
console.log(mime2); // application/atom+xml
 
var mime3 = docsniff('application/xml; charset=UTF-8', '<?xml version="1.0" encoding="UTF-8" ?><feed></feed>');
console.log(mime3); // application/xml

Currently this module will correct following mime:

  • text/html
  • text/xml
  • text/plain
  • application/xml
  • application/rss+xml
  • application/atom+xml
  • application/rdf+xml
  • application/octet-stream

It does not attempt to be overzealous at correcting subtypes; see example 3 above, if original mime is acceptable, it will not be replaced.

API

docsniff(type, body);

  • type is the content-type header in response
  • body is the response body string
  • returns the sniffed content-type as string

Limits

The whatwg spec has a much more thorough algorithm and mime list for browser vendors, but on server-side, we are more interested in parsable documents and information extractions, if you encounter a use case not covered by this algorithm, please let us know on github issues.

Like any simple algorithm, this can easily be spoofed, so don't use it for validation, use it for mime sniffing incoming documents only.

(For better security: mime and mmmagic can handle most filetypes, but you still need XSS protections and content whitelist to safely serve content to users.)

License

MIT

install

npm i doc-sniff

Downloadsweekly downloads

29

version

1.0.1

license

MIT

homepage

github.com

repository

Gitgithub

last publish

collaborators

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