<!--
  ~ Copyright 2016 Red Hat, Inc. and/or its affiliates
  ~ and other contributors as indicated by the @author tags.
  ~
  ~ Licensed under the Apache License, Version 2.0 (the "License");
  ~ you may not use this file except in compliance with the License.
  ~ You may obtain a copy of the License at
  ~
  ~ http://www.apache.org/licenses/LICENSE-2.0
  ~
  ~ Unless required by applicable law or agreed to in writing, software
  ~ distributed under the License is distributed on an "AS IS" BASIS,
  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  ~ See the License for the specific language governing permissions and
  ~ limitations under the License.
  -->

<chapter id="security_vulnerabilities">
    <title>Security Vulnerabilities</title>
    <para>
        This chapter discusses possible security vulnerabilities Keycloak could have, how Keycloak mitigates those
        vulnerabilities, and what steps you need to do to configure Keycloak to mitigate some vulnerabilities.  A good list
        of potential vulnerabilities and what security implementations should do to mitigate them can be found in the
        <ulink url="http://tools.ietf.org/html/rfc6819">OAuth 2.0 Threat Model</ulink> document put out by the IETF.  Many of those vulnerabilities are discussed here.
    </para>
    <section>
        <title>SSL/HTTPS Requirement</title>
        <para>
            If you do not use SSL/HTTPS for all communication between the Keycloak auth server and the clients it secures
            you will be very vulnerable to man in the middle attacks.  OAuth 2.0/OpenID Connect uses access tokens for
            security.  Without SSL/HTTPS, attackers can sniff your network and obtain an access token.  Once they have an
            access token they can do any operation that the token has been given permission for.
        </para>
        <para>
            Keycloak has <link linkend="ssl_modes">three modes for SSL/HTTPS</link>.  SSL can be hard to set up, so out of the box, Keycloak allows
            non-HTTPS communication over private IP addresses like localhost, 192.168.x.x, and other private IP addresses.
            In production, you should make sure SSL is enabled and required across the board.
        </para>
        <para>
            On the adapter/client side, Keycloak allows you to turn off the SSL trust manager.  The trust manager ensures
            identity the client is talking to.  It checks the DNS domain name against the server's certificate.  In production
            you should make sure that each of your client adapters is configured to use a truststore.  Otherwise you are vulnerable
            to DNS man in the middle attacks.
        </para>
    </section>
    <section>
        <title>CSRF Attacks</title>
        <para>
            Cross-site request forgery (CSRF) is a web-based attack whereby HTTP
            requests are transmitted from a user that the web site trusts or has
            authenticated (e.g., via HTTP redirects or HTML forms).  Any site that uses
            cookie based authentication is vulnerable for these types of attacks.  These attacks are mitigated
            by matching a state cookie against a posted form or query parameter.
        </para>
        <para>
            OAuth 2.0 login specification requires that a state cookie be used and matched against a transmitted state
            parameter.  Keycloak fully implements this part of the specification so all logins are protected.
        </para>
        <para>
            The Keycloak adminstration console is a pure Javascript/HTML5 application that makes REST calls to the
            backend Keycloak admin API.  These calls all require bearer token authentication and are made via Javascript
            Ajax calls.  CSRF does not apply here.  The admin REST API can also be configured to validate CORS origins
            as well.
        </para>
        <para>
            The only part of Keycloak that really falls into CSRF is the user account management pages.  To mitigate this
            Keycloak sets a state cookie and also embeds the value of this state cookie within hidden form fields or
            query parameters in action links.  This query or form parameter is checked against the state cookie to verify
            that the call was made by the user.
        </para>
    </section>
    <section>
        <title>Clickjacking</title>
        <para>
            With clickjacking, a malicious site loads the target site in a
            transparent iFrame overlaid on top of a set of dummy
            buttons that are carefully constructed to be placed directly under
            important buttons on the target site.  When a user clicks a visible
            button, they are actually clicking a button (such as an "Authorize"
            button) on the hidden page.  An attacker can steal a user's authentication credentials and
            access their resources.
        </para>
        <para>
            By default, every response by Keycloak sets some specific browser headers that can prevent this from happening
            specifically <ulink url="http://tools.ietf.org/html/rfc7034">X-FRAME_OPTIONS</ulink> and <ulink url="http://www.w3.org/TR/CSP/">Content-Security-Policy</ulink>.  You
            should take a look at both of these headers.  In the admin console you can specify the values these headers will
            have.  By default, Keycloak only sets up a same-origin policy for iframes.
        </para>
    </section>
    <section>
        <title>Compromised Access Codes</title>
        <para>
            It would be very hard for an attacker to compromise Keycloak access codes.  Keycloak generates a cryptographically
            strong random value for its access codes so it would be very hard to guess an access token.
            An access code can only be turned into an access token once so it can't be replayed.  In the admin console
            you can specify how long an access token is valid for.  This value should be really short.  Like a seconds.
            Just long enough for the client to make the request to turn the code into an token.
        </para>
    </section>
    <section>
        <title>Compromised access and refresh tokens</title>
        <para>
            There's a few things you can do to mitigate access tokens and refresh tokens from being stolen.
            Most importantly is to enforce SSL/HTTPS communication between Keycloak and its clients and applications.
            Short lifespans (minutes) for access tokens allows Keycloak to check the validity of a refresh token.  Making
            sure refresh tokens always stay private to the client and are never transmitted ever is very important as well.
        </para>
        <para>
            If an access token or refresh token is compromised, the first thing you should do is go to the admin console
            and push a not-before revocation policy to all applications.  This will enforce that any tokens issued
            prior to that date are now invalid.  You can also disable specific applications, clients, and users if you
            feel that any one of those entities is completely compromised.
        </para>
    </section>
    <section>
        <title>Open redirectors</title>
        <para>
            An attacker could use the end-user authorization endpoint and the
            redirect URI parameter to abuse the authorization server as an open
            redirector.  An open redirector is an endpoint using a parameter to
            automatically redirect a user agent to the location specified by the
            parameter value without any validation.  An attacker could utilize a user's trust in an authorization
            server to launch a phishing attack.
        </para>
        <para>
            Keycloak requires that all registered applications and clients register at least one redirection uri pattern.
            Any time a client asks Keycloak to perform a redirect (on login or logout for example), Keycloak will
            check the redirect uri vs. the list of valid registered uri patterns.  It is important that clients and
            applications register as specific a URI pattern as possible to mitigate open redirector attacks.
        </para>
    </section>
    <section>
        <title>Password guess: brute force attacks</title>
        <para>
            A brute force attack happens when an attacker is trying to guess a user's password.  Keycloak has some
            limited brute force detection capabilities.  If turned on, a user account will be temporarily disabled
            if a threshold of login failures is reached.  The downside of this is that this makes Keycloak vulnerable
            to denial of service attacks.  Eventually we will expand this functionality to take client IP address into
            account when deciding whether to block a user.
        </para>
        <para>
            Another thing you can do to prevent password guessing is to point a tool like <ulink url="http://fail2ban.org">Fail2Ban</ulink> to the Keycloak
            server's log file.  Keycloak logs every login failure and client IP address that had the failure.
        </para>
        <para>
            In the admin console, per realm, you can set up a password policy to enforce that users pick hard to guess passwords.
            A password has to match all policies. The password policies that can be configured are hash iterations, length, digits,
            lowercase, uppercase, special characters, not username, regex patterns, password history and force expired password update. 
            Force expired password update policy forces or requires password updates after specified span of time. Password history policy 
            restricts a user from resetting his password to N old expired passwords. Multiple regex patterns can be specified.
            If there's more than one regex added, password has to match all fully.
            Increasing number of Hash Iterations (n) does not worsen anything (and certainly not the cipher) and it greatly increases the 
            resistance to dictionary attacks. However the drawback to increasing n is that it has some cost (CPU usage, energy, delay) for 
            the legitimate parties. Increasing n also slightly increases the odds that a random password gives the same result as the right 
            password due to hash collisions, and is thus a false but accepted password; however that remains very unlikely, in the order of 
            n*[1/(2^256)] for practical values of n, and can be entirely ignored in practice. Keycloak also uses PBKDF2 internally to 
            cryptographically derive passwords to refine and improve the ratio of cost between attacker and legitimate parties.
            Good practice is to pay attention to the time complexity of hash_password and hash; then increase n as much as tolerable in 
            the situation(s) at hand and and revise parameters such as n every few years to account for time complexity trade off.
        </para>
        <para>
            Finally, the best way to mitigate against brute force attacks is to require user to set up a one-time-password (OTP).
        </para>
    </section>
    <section>
        <title>Password database compromised</title>
        <para>
            Keycloak does not store passwords in raw text.  It stores a hash of them.  Because of performance reasons,
            Keycloak only hashes passwords once.  While a human could probably never crack a hashed password, it is very
            possible that a computer could.  The security community suggests around 20,000 (yes thousand!) hashing iterations
            to be done to each password.  This number grows every year due to increasing computing power (It was 1000 12 years ago).
            The problem with this is that password hashing is a huge performance hit as each login would require the entered
            password to be hashed that many times and compared to the stored hash.  So, its up to the admin to configure the
            password hash iterations.  This can be done in the admin console password policy configuration.  Again, the default
            value is 1 as we thought it might be more important for Keycloak to scale out of the box.  There's a lot of
            other measures admins can do to protect their password databases.
        </para>
    </section>
    <section>
        <title>SQL Injection attacks</title>
        <para>
            At this point in time, there is no knowledge of any SQL injection vulnerabilities in Keycloak
        </para>
    </section>
    <section>
        <title>Limiting Scope</title>
        <para>
            Using the <literal>Scope</literal> menu in the admin console for clients, you can control
            exactly which role mappings will be included within the token sent back to the client application.  This
            allows you to limit the scope of permissions given to the client which is great if the client isn't
            very trusted and is known to not being very careful with its tokens.
        </para>
    </section>
</chapter>