Content Security Policy Builder
Easily integrate Content-Security-Policy headers into your web application, either
from a JSON configuration file, or programatically.
CSP Builder was created by Paragon Initiative Enterprises
as part of our effort to encourage better application security practices.
Check out our other open source projects too.
There's also a CSP middleware available that uses this library.
Installing
First, get Composer, then run:
composer require paragonie/csp-builder
Build a Content Security Policy header from a JSON configuration file
<?php
use ParagonIE\CSPBuilder\CSPBuilder;
$csp = CSPBuilder::fromFile('/path/to/source.json');
$csp->sendCSPHeader();
You can also load the configuration from a JSON string, like so:
<?php
use ParagonIE\CSPBuilder\CSPBuilder;
$configuration = file_get_contents('/path/to/source.json');
if (!is_string($configuration)) {
throw new Error('Could not read configuration file!');
}
$csp = CSPBuilder::fromData($configuration);
$csp->sendCSPHeader();
Finally, you can just pass an array to the first argument of the constructor:
<?php
use ParagonIE\CSPBuilder\CSPBuilder;
$configuration = file_get_contents('/path/to/source.json');
if (!is_string($configuration)) {
throw new Error('Could not read configuration file!');
}
$decoded = json_decode($configuration, true);
if (!is_array($decoded)) {
throw new Error('Could not parse configuration!');
}
$csp = new CSPBuilder($decoded);
$csp->sendCSPHeader();
Example
{
"report-only": false,
"report-to": "PolicyName",
"report-uri": "/csp_violation_reporting_endpoint",
"base-uri": [],
"default-src": [],
"child-src": {
"allow": [
"https://www.youtube.com",
"https://www.youtube-nocookie.com"
],
"self": false
},
"connect-src": [],
"font-src": {
"self": true
},
"form-action": {
"allow": [
"https://example.com"
],
"self": true
},
"frame-ancestors": [],
"img-src": {
"blob": true,
"self": true,
"data": true
},
"media-src": [],
"object-src": [],
"plugin-types": [],
"script-src": {
"allow": [
"https://www.google-analytics.com"
],
"self": true,
"unsafe-inline": false,
"unsafe-eval": false
},
"style-src": {
"self": true
},
"upgrade-insecure-requests": true
}
Build a Content Security Policy, programmatically
<?php
use ParagonIE\CSPBuilder\CSPBuilder;
$csp = CSPBuilder::fromFile('/path/to/source.json');
// Let's add a nonce for inline JS
$nonce = $csp->nonce('script-src');
$body .= "<script nonce={$nonce}>";
$body .= $desiredJavascriptCode;
$body .= "</script>";
// Let's add a hash to the CSP header for $someScript
$hash = $csp->hash('script-src', $someScript, 'sha256');
// Add a new source domain to the whitelist
$csp->addSource('image', 'https://ytimg.com');
// Set the Report URI
$csp->setReportUri('https://example.com/csp_report.php');
// Let's turn on HTTPS enforcement
$csp->addDirective('upgrade-insecure-requests', true);
$csp->sendCSPHeader();
Note that many of these methods can be chained together:
$csp = CSPBuilder::fromFile('/path/to/source.json');
$csp->addSource('image', 'https://ytimg.com')
->addSource('frame', 'https://youtube.com')
->addDirective('upgrade-insecure-requests', true)
->sendCSPHeader();
addSource()addDirective()disableOldBrowserSupport()enableOldBrowserSupport()hash()preHash()setDirective()setBlobAllowed()setDataAllowed()setFileSystemAllowed()setMediaStreamAllowed()setReportUri()setSelfAllowed()setAllowUnsafeEval()setAllowUnsafeInline()
Inject a CSP header into a PSR-7 message
Instead of invoking sendCSPHeader(), you can instead inject the headers into
your PSR-7 message object by calling it like so:
/**
* $yourMessageHere is an instance of an object that implements
* \Psr\Http\Message\MessageInterface
*
* Typically, this will be a Response object that implements
* \Psr\Http\Message\ResponseInterface
*
* @ref https://github.com/guzzle/psr7/blob/master/src/Response.php
*/
$csp->injectCSPHeader($yourMessageHere);
Save a CSP header for configuring Apache/nginx
Instead of calling sendCSPHeader() on every request, you can build the CSP once
and save it to a snippet for including in your server configuration:
$policy = CSPBuilder::fromFile('/path/to/source.json');
$policy->saveSnippet(
'/etc/nginx/snippets/my-csp.conf',
CSPBuilder::FORMAT_NGINX
);
Make sure you reload your webserver afterwards.
Support Contracts
If your company uses this library in their products or services, you may be
interested in purchasing a support contract from Paragon Initiative Enterprises.