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Signed and unsigned cookies based on Keygrip

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README.md

Cookies

Build Status

Cookies is a node.js module for getting and setting HTTP(S) cookies. Cookies can be signed to prevent tampering, using Keygrip. It can be used with the built-in node.js HTTP library, or as Connect/Express middleware.

Requirements

Install

$ npm install cookies

Features

  • Lazy: Since cookie verification against multiple keys could be expensive, cookies are only verified lazily when accessed, not eagerly on each request.

  • Secure: All cookies are httponly by default, and cookies sent over SSL are secure by default. An error will be thrown if you try to send secure cookies over an insecure socket.

  • Unobtrusive: Signed cookies are stored the same way as unsigned cookies, instead of in an obfuscated signing format. An additional signature cookie is stored for each signed cookie, using a standard naming convention (cookie-name.sig). This allows other libraries to access the original cookies without having to know the signing mechanism.

  • Agnostic: This library is optimized for use with Keygrip, but does not require it; you can implement your own signing scheme instead if you like and use this library only to read/write cookies. Factoring the signing into a separate library encourages code reuse and allows you to use the same signing library for other areas where signing is needed, such as in URLs.

API

cookies = new Cookies( request, response, [ Object keygrip ] )

This creates a cookie jar corresponding to the current request and response. A Keygrip object can optionally be passed as the third argument keygrip to enable cryptographic signing based on SHA1 HMAC, using rotated credentials.

Note that since this only saves parameters without any other processing, it is very lightweight. Cookies are only parsed on demand when they are accessed.

express.createServer( Cookies.express([ Object keygrip ] ) )

This adds cookie support as a Connect middleware layer for use in Express apps, allowing inbound cookies to be read using req.cookies.get and outbound cookies to be set using res.cookies.set.

cookies.get( name, [ options ] )

This extracts the cookie with the given name from the Cookie header in the request. If such a cookie exists, its value is returned. Otherwise, nothing is returned.

{ signed: true } can optionally be passed as the second parameter options. In this case, a signature cookie (a cookie of same name ending with the .sig suffix appended) is fetched. If no such cookie exists, nothing is returned.

If the signature cookie does exist, the provided Keygrip object is used to check whether the hash of cookie-name=cookie-value matches that of any registered key:

  • If the signature cookie hash matches the first key, the original cookie value is returned.
  • If the signature cookie hash matches any other key, the original cookie value is returned AND an outbound header is set to update the signature cookie's value to the hash of the first key. This enables automatic freshening of signature cookies that have become stale due to key rotation.
  • If the signature cookie hash does not match any key, nothing is returned, and an outbound header with an expired date is used to delete the cookie.

cookies.set( name, [ value ], [ options ] )

This sets the given cookie in the response and returns the current context to allow chaining.

If the name is omitted, an outbound header with an expired date is used to delete the cookie.

If the options object is provided, it will be used to generate the outbound cookie header as follows:

  • expires: a Date object indicating the cookie's expiration date (expires at the end of session by default).
  • path: a string indicating the path of the cookie (/ by default).
  • domain: a string indicating the domain of the cookie (no default).
  • secure: a boolean indicating whether the cookie is only to be sent over HTTPS (false by default for HTTP, true by default for HTTPS).
  • httpOnly: a boolean indicating whether the cookie is only to be sent over HTTP(S), and not made available to client JavaScript (true by default).
  • signed: a boolean indicating whether the cookie is to be signed (false by default). If this is true, another cookie of the same name with the .sig suffix appended will also be sent, with a 27-byte url-safe base64 SHA1 value representing the hash of cookie-name=cookie-value against the first Keygrip key. This signature key is used to detect tampering the next time a cookie is received.

Example

// from ./test.js
server = http.createServer( function( req, res ) {
  var cookies = new Cookies( req, res, keys )
    , unsigned, signed, tampered

  if ( req.url == "/set" ) {
    cookies
      // set a regular cookie
      .set( "unsigned", "foo", { httpOnly: false } )

      // set a signed cookie
      .set( "signed", "bar", { signed: true } )

      // mimic a signed cookie, but with a bogus signature
      .set( "tampered", "baz" )
      .set( "tampered.sig", "bogus" )

    res.writeHead( 302, { "Location": "/" } )
    return res.end( "Now let's check." )
  }

  unsigned = cookies.get( "unsigned" )
  signed = cookies.get( "signed", { signed: true } )
  tampered = cookies.get( "tampered", { signed: true } )

  assert.equal( unsigned, "foo" )
  assert.equal( signed, "bar" )
  assert.notEqual( tampered, "baz" )
  assert.equal( tampered, undefined )

  res.writeHead( 200, { "Content-Type": "text/plain" } )
  res.end(
    "unsigned expected: foo\n\n" +
    "unsigned actual: " + unsigned + "\n\n" +
    "signed expected: bar\n\n" +
    "signed actual: " + signed + "\n\n" +
    "tampered expected: undefined\n\n"+
    "tampered: " + tampered + "\n\n"
  )
})

Copyright

Copyright (c) 2012 Jed Schmidt. See LICENSE.txt for details.

Send any questions or comments here.

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