NelmioSecurityBundle

About

The NelmioSecurityBundle provides additional security features for your Symfony2 application.

Installation

Require the nelmio/security-bundle package in your composer.json and update your dependencies.

$ composer require nelmio/security-bundle

Add the NelmioSecurityBundle to your application's kernel:

public function registerBundles()
{
    $bundles = array(
        ...
        new Nelmio\SecurityBundle\NelmioSecurityBundle(),
        ...
    );
    ...
}

Features

• Content Security Policy: Cross site scripting attacks (XSS) can be mitigated in modern browsers using a policy which instructs the browser never to execute inline scripts, or never to load content from another domain than the page's domain.

• Signed Cookies: Specify certain cookies to be signed, so that the user cannot modify them. Note that they will not be encrypted, but signed only. The contents will still be visible to the user.

• Encrypted Cookies: Specify certain cookies to be encrypted, so that the value cannot be read. When you retrieve the cookie it will be automatically decrypted.

• Clickjacking Protection: X-Frame-Options header is added to all responses to prevent your site from being put in a frame/iframe. This can have serious security implications as it has been demonstrated time and time again with Facebook and others. You can allow framing of your site from itself or from anywhere on a per-URL basis.

• External Redirects Detection: Redirecting from your site to arbitrary URLs based on user input can be exploited to confuse users into clicking links that seemingly point to valid sites while they in fact lead to malicious content. It also may be possible to gain PageRank that way.

• Forced HTTPS/SSL Handling: This forces by all requests to go through SSL. It will also send HSTS headers so that modern browsers supporting it can make users use HTTPS even if they enter URLs without https, avoiding attacks on public Wi-Fi.

• Flexible HTTPS/SSL Handling: If you don't want to force all users to use HTTPS, you should at least use secure session cookies and force SSL for logged-in users. But then logged-in users appear logged-out when they access a non-HTTPS resource. This is not really a good solution. This will make the application detect logged-in users and redirect them to a secure URL, without making the session cookie insecure.

• Cookie Session Handler: You can configure the session handler to use a cookie based storage. WARNING: by default the session is not encrypted, it is your responsibility to properly configure the Encrypted Cookies section to include the session cookie (default name: session). The size limit of a cookie is 4KB, so make sure you are not storing object or long text into session.

• Disable Content Type Sniffing: Require that scripts are loaded using the correct mime type. This disables the feature that some browsers have which uses content sniffing to determine if the response is a valid script file or not.

Maximum Security Configuration (Read on for detailed recommendations!)

nelmio_security:
    # signs/verifies all cookies
    signed_cookie:
        names: ['*']
    # encrypt all cookies
    encrypted_cookie:
        names: ['*']
    # prevents framing of the entire site
    clickjacking:
        paths:
            '^/.*': DENY
    # prevents redirections outside the website's domain
    external_redirects:
        abort: true
        log: true

    # prevents inline scripts, unsafe eval, external scripts/images/styles/frames, etc
    csp:
        report:
            report-uri: [/nelmio/csp/report]
            default-src: [ 'self' ]
            # There's no flash on our site
            object-src:
                - 'none'
            script-src:
                - 'unsafe-inline'
                - 'unsafe-eval'
                - 'self'
        enforce:
            # see https://github.com/nelmio/NelmioSecurityBundle/issues/32
            report-uri: [/nelmio/csp/report]
            script-src:
                - 'self'

    # disables content type sniffing for script resources
    content_type:
        nosniff: true

    # forced HTTPS handling, don't combine with flexible mode
    # and make sure you have SSL working on your site before enabling this
#    forced_ssl:
#        hsts_max_age: 2592000 # 30 days
#        hsts_subdomains: true

    # flexible HTTPS handling, read the detailed config info
    # and make sure you have SSL working on your site before enabling this
#    flexible_ssl:
#        cookie_name: auth
#        unsecured_logout: false

Configuration Detail

Content Security Policy:

Using CSP you can set a policy which modern browsers understand and will honor. The policy contains nine different directives; default-src, script-src, object-src, style-src, img-src, media-src, frame-src, font-src, connect-src, report-uri. You can provide an array of directives per content type. Empty content types will inherit from default-src, specified content types will never inherit from default-src. Please see the Content Security Policy 1.0 specification for details.

Each directive should be a domain, URI or keyword. The keyword 'self' will allow content from the same origin as the page. If you need to allow inline scripts or eval() you can use 'unsafe-inline' and 'unsafe-eval'.

WARNING: By using 'unsafe-inline' or 'unsafe-eval' you're effectively disabling the XSS protection mechanism of CSP.

Apart from content types, the policy also accepts report-uri which should be a URI where a browser can POST a JSON payload to whenever a policy directive is violated.

nelmio_security:
    csp:
        report_logger_service: logger
        enforce:
            report-uri: /nelmio/csp/report
            default-src: [ 'self' ]
            frame-src: [ 'https://www.youtube.com' ]
            script-src:
                - 'self'
                - 'unsafe-inline'
            img-src:
                - 'self'
                - facebook.com
                - flickr.com
        report:
            report-uri: /nelmio/csp/report
            script-src:
                - 'self'

The above configuration would enforce the following policy:

• Default is to allow from same origin as the page
• Frames only from secure youtube connections
• JavaScript from same origin and from inline <script> tags
• Images from same origin, facebook.com and flickr.com

Any violation of the enforced policy would be posted to /nelmio/csp/report.

In addition, the configuration only reports but doesn't enforce the policy that JavaScript may only be executed when it comes from the same server.

The bundle provides a default reporting implementation that logs violations as notices to the default logger, to enable add the following to your routing.yml:

nelmio_security:
    path:     /nelmio/csp/report
    defaults: { _controller: nelmio_security.csp_reporter_controller:indexAction }
    methods:  [POST]

(Optional) Use report_logger_id to log to the 'security' channel:

nelmio_security:
    csp:
        report_logger_service: monolog.logger.security

(Optional) Disable compat_headers to avoid sending X-Content-Security-Policy (IE10, IE11, Firefox < 23). This will mean those browsers get no CSP instructions.

nelmio_security:
    csp:
        compat_headers: false

Signed Cookies:

Ideally you should explicitly specify which cookies to sign. The reason for this is simple. Cookies are sent with each request. Signatures are often longer than the cookie values themselves, so signing everything would just needlessly slow down your app and increase bandwidth usage for your users.

nelmio_security:
    signed_cookie:
        names: [test1, test2]

However, for simplicity reasons, and to start with a high security and optimize later, you can specify '*' as a cookie name to have all cookies signed automatically.

nelmio_security:
    signed_cookie:
        names: ['*']

Additional, optional configuration settings:

nelmio_security:
    signed_cookie:
        secret: this_is_very_secret # defaults to global %secret% parameter
        hash_algo: sha512 # defaults to sha256, see `hash_algos()` for available algorithms

Encrypted Cookies:

Encrypts the cookie values using nelmio_security.encrypted_cookie.secret. It works the same as Signed Cookies:

nelmio_security:
    encrypted_cookie:
        names: [test1, test2]

Additional, optional configuration settings:

nelmio_security:
    encrypted_cookie:
        secret: this_is_very_secret # defaults to global %secret% parameter
        algorithm: rijndael-256 # defaults to rijndael-128, see `mcrypt_list_algorithms()` for available algorithms

Clickjacking Protection:

Most websites do not use frames and do not need to be frame-able. This is a common attack vector for which all current browsers (IE8+, Opera10.5+, Safari4+, Chrome4+ and Firefox3.7+) have a solution. An extra header sent by your site will tell the browser that it can not be displayed in an frame. Browsers react by showing a short explanation instead of the content, or a blank page.

The valid values for the X-Frame-Options header are DENY (prevent framing from all pages) and SAMEORIGIN (prevent framing from all pages not on the same domain). Additionally this bundle supports the ALLOW option which skips the creation of the header for the matched URLs, if you want to whitelist a few URLs and then DENY everything else.

One more option, as of yet not well supported, is to use ALLOW FROM uri where uri can be any origin URL, from example.org to https://example.org:123/sub/path. This lets you specify exactly which domain can embed your site, in case you have a multi-domain setup.

Default configuration (deny everything):

nelmio_security:
    clickjacking:
        paths:
            '^/.*': DENY

Whitelist configuration (deny all but a few URLs):

nelmio_security:
    clickjacking:
        paths:
            '^/iframes/': ALLOW
            '^/business/': 'ALLOW FROM https://biz.example.org'
            '^/local/': SAMEORIGIN
            '^/.*': DENY

You can also of course only deny a few critical URLs, while leaving the rest alone:

nelmio_security:
    clickjacking:
        paths:
            '^/message/write': DENY

External Redirects Detection:

This feature helps you detect and prevent redirects to external sites. This can easily happen by accident if you carelessly take query parameters as redirection target.

You can log those (it's logged at warning level) by turning on logging:

nelmio_security:
    external_redirects:
        log: true

You can abort (they are replaced by a 403 response) the redirects:

nelmio_security:
    external_redirects:
        abort: true

Or you can override them, replacing the redirect's Location header by a route name or another URL:

# redirect to the 'home' route
nelmio_security:
    external_redirects:
        override: home

# redirect to another URL
nelmio_security:
    external_redirects:
        override: /foo

If you want to display the URL that was blocked on the overriding page you can specify the forward_as parameter, which defines which query parameter will receive the URL. For example using the config below, doing a redirect to http://example.org/ will be overridden to /external-redirect?redirUrl=http://example.org/.

# redirect and forward the overridden URL
nelmio_security:
    external_redirects:
        override: /external-redirect
        forward_as: redirUrl

Since it's quite common to have to redirect outside the website for legit reasons, typically OAuth logins and such, you can whitelist a few domain names. All their subdomains will be whitelisted as well, so that allows you to whitelist your own website's subdomains if needed.

nelmio_security:
    external_redirects:
        abort: true
        whitelist:
            - twitter.com
            - facebook.com

Forced HTTPS/SSL Handling:

By default, this option forces your entire site to use SSL, always. It redirect all users reaching the site with a http:// URL to a https:// URL.

The base configuration for this is the following:

nelmio_security:
    forced_ssl: ~

If you turn this option on, it's recommended to also set your session cookie to be secure, and all other cookies your send for that matter. You can do the former using:

framework:
    session:
        cookie_secure: true

To keep a few URLs from being force-redirected to SSL you can define a whitelist of regular expressions:

nelmio_security:
    forced_ssl:
        enabled: true
        whitelist:
            - ^/unsecure/

Then if you want to push it further, you can enable HTTP Strict Transport Security (HSTS). This is basically sending a header to tell the browser that your site must always be accessed using SSL. If a user enters a http:// URL, the browser will convert it to https:// automatically, and will do so before making any request, which prevents man-in-the-middle attacks.

The browser will cache the value for as long as the specified hsts_max_age (in seconds), and if you turn on the hsts_subdomains option, the behavior will be applied to all subdomains as well.

nelmio_security:
    forced_ssl:
        hsts_max_age: 2592000 # 30 days
        hsts_subdomains: true

You can also tell the browser to add your site to the list of known HSTS sites, by enabling hsts_preload. Once your site has appeared in the Chrome and Firefox preload lists, then new users who come to your site will already be redirected to https urls.

nelmio_security:
    forced_ssl:
        hsts_max_age: 10886400 # 18 weeks
        hsts_preload: true

Note: A value of at least 18 weeks is currently required by Chrome and Firefox. It seems hsts_subdomains must also be enabled for preloading to work.

You can speed up the inclusion process by submitting your site to the HSTS Preload List.

A small word of caution: While HSTS is great for security, it means that if the browser can not establish your SSL certificate is valid, it will not allow the user to query your site. That just means you should be careful and renew your certificate in due time.

Note: HSTS presently (Jan. 2015) works in Firefox 4+, Chrome 4+ and Opera 12+. Check caniuse for HSTS support in other browsers.

Flexible HTTPS/SSL Handling:

The best way to handle SSL securely is to enable it for your entire site.

However in some cases this is not desirable, be it for caching or performance reasons, or simply because most visitors of your site are anonymous and don't benefit much from the added privacy and security of SSL.

If you don't want to enable SSL across the board, you need to avoid that people on insecure networks (typically open Wi-Fi) get their session cookie stolen by sending it non-encrypted. The way to achieve this is to set your session cookie to be secure as such - but don't do it just yet, keep reading to the end.

framework:
    session:
        cookie_secure: true

If you use the remember-me functionality, you would also mark that one as secure:

security:
    firewalls:
        somename:
            remember_me:
                secure: true

Now if you do this, you have two problems. First, insecure pages will not be able to use the session anymore, which can be inconvenient. Second, if a logged in user gets to a non-https page of your site, it is seen as anonymous since his browser will not send the session cookie. To fix this, this bundle sets a new insecure cookie (flexible_ssl.cookie_name, defaults to auth) once a user logs in. That way, if any page is accessed insecurely by a logged in user, he is redirected to the secure version of the page, and his session is then visible to the framework.

Enabling the flexible_ssl option of the NelmioSecurityBundle will make sure that logged-in users are always seeing secure pages, and it will make sure their session cookie is secure, but anonymous users will still be able to have an insecure session, if you need to use it to store non critical data like language settings and whatnot. The remember-me cookie will also be made always secure, even if you leave the setting to false.

nelmio_security:
    flexible_ssl:
        cookie_name: auth
        unsecured_logout: false

You have to configure one more thing in your security configuration though, every firewall should have our logout listener added, so that the special auth cookie can be cleared when users log out. You can do it as such:

security:
    firewalls:
        somename:
            # ...
            logout:
                handlers:
                    - nelmio_security.flexible_ssl_listener

On logout, if you would like users to be redirected to an unsecure page set unsecured_logout to true.

Cookie Session Handler:

You can configure the session handler to use a cookie based storage. There are various reasons to do this, but generally speaking unless you have a very good one you should avoid it.

WARNING: by default the session is not encrypted, it is your responsibility to properly configure the Encrypted Cookies section to include the session cookie (default name: session). The size limit of a cookie is 4KB, so make sure you are not storing objects or long strings in the session.

framework:
    session:
        handler_id: nelmio_security.session.handler

nelmio_security:
    cookie_session:
        enabled: true
        name: session

    encrypted_cookie:
        names: [session]

Content Type Sniffing

Disables the content type sniffing for script resources. Forces the browser to only execute script files with valid content type headers. This is a non-standard header from Microsoft, more information can be found in their documentation at MSDN.

nelmio_security:
    content_type:
        nosniff: true

License

Released under the MIT License, see LICENSE.