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href="/oauth2-servers/accessing-data/create-an-application/" data-section="2.1">Create an Application</a></li> <li class="page_item page-item-903"><a href="/oauth2-servers/accessing-data/setting-up-the-environment/" data-section="2.2">Setting up the Environment</a></li> <li class="page_item page-item-907"><a href="/oauth2-servers/accessing-data/authorization-request/" data-section="2.3">Authorization Request</a></li> <li class="page_item page-item-910"><a href="/oauth2-servers/accessing-data/obtaining-an-access-token/" data-section="2.4">Obtaining an Access Token</a></li> <li class="page_item page-item-912"><a href="/oauth2-servers/accessing-data/making-api-requests/" data-section="4.5">Making API Requests</a></li> </ul> </li> <li class="page_item page-item-28 page_item_has_children"><a href="/oauth2-servers/signing-in-with-google/" data-section="3">Signing in with Google</a> <ul class='children'> <li class="page_item page-item-883"><a href="/oauth2-servers/signing-in-with-google/create-an-application/" data-section="3.1">Create an Application</a></li> <li class="page_item page-item-886"><a href="/oauth2-servers/signing-in-with-google/setting-up-the-environment/" data-section="3.2">Setting up the Environment</a></li> <li class="page_item page-item-888"><a href="/oauth2-servers/signing-in-with-google/authorization-request/" data-section="3.3">Authorization Request</a></li> <li class="page_item page-item-891"><a href="/oauth2-servers/signing-in-with-google/getting-an-id-token/" data-section="3.4">Getting an ID Token</a></li> <li class="page_item page-item-893"><a href="/oauth2-servers/signing-in-with-google/verifying-the-user-info/" data-section="3.5">Verifying the User Info</a></li> </ul> </li> <li class="page_item page-item-95 page_item_has_children"><a href="/oauth2-servers/server-side-apps/" data-section="4">Server-Side Apps</a> <ul class='children'> <li class="page_item page-item-865"><a href="/oauth2-servers/server-side-apps/authorization-code/" data-section="4.1">Authorization Code Grant</a></li> <li class="page_item page-item-869"><a href="/oauth2-servers/server-side-apps/example-flow/" data-section="4.2">Example Flow</a></li> <li class="page_item page-item-872"><a href="/oauth2-servers/server-side-apps/possible-errors/" data-section="4.3">Possible Errors</a></li> <li class="page_item page-item-874"><a href="/oauth2-servers/server-side-apps/user-experience/" data-section="4.4">User Experience and Security Considerations</a></li> </ul> </li> <li class="page_item page-item-36 page_item_has_children"><a href="/oauth2-servers/single-page-apps/" data-section="5">Single-Page Apps</a> <ul class='children'> <li class="page_item page-item-856"><a href="/oauth2-servers/single-page-apps/authorization/" data-section="5.1">Authorization</a></li> <li class="page_item page-item-850"><a href="/oauth2-servers/single-page-apps/example-flow/" data-section="5.2">Example Flow</a></li> <li class="page_item page-item-847"><a href="/oauth2-servers/single-page-apps/implicit-flow/" data-section="5.3">Implicit Flow for Single-Page Apps</a></li> <li class="page_item page-item-854"><a href="/oauth2-servers/single-page-apps/security-considerations/" data-section="5.4">Security Considerations for Single-Page Apps</a></li> </ul> </li> <li class="page_item page-item-33 page_item_has_children"><a href="/oauth2-servers/mobile-and-native-apps/" data-section="6">Mobile and Native Apps</a> <ul class='children'> <li class="page_item page-item-838"><a href="/oauth2-servers/mobile-and-native-apps/authorization/" data-section="6.1">Authorization</a></li> <li class="page_item page-item-841"><a href="/oauth2-servers/mobile-and-native-apps/security-considerations/" data-section="6.2">Security Considerations</a></li> </ul> </li> <li class="page_item page-item-138 page_item_has_children"><a href="/oauth2-servers/making-authenticated-requests/" data-section="7">Making Authenticated Requests</a> <ul class='children'> <li class="page_item page-item-833"><a href="/oauth2-servers/making-authenticated-requests/refreshing-an-access-token/" data-section="7.1">Refresh Tokens</a></li> </ul> </li> <li class="page_item page-item-140 page_item_has_children"><a href="/oauth2-servers/client-registration/" data-section="8">Client Registration</a> <ul class='children'> <li class="page_item page-item-142"><a href="/oauth2-servers/client-registration/registering-new-application/" data-section="8.1">Registering a New Application</a></li> <li class="page_item page-item-144"><a href="/oauth2-servers/client-registration/client-id-secret/" data-section="8.2">The Client ID and Secret</a></li> <li class="page_item page-item-146"><a href="/oauth2-servers/client-registration/deleting-applications-revoking-secrets/" data-section="8.3">Deleting Applications and Revoking Secrets</a></li> </ul> </li> <li class="page_item page-item-148 page_item_has_children current_page_ancestor current_page_parent"><a href="/oauth2-servers/authorization/" data-section="9">Authorization</a> <ul class='children'> <li class="page_item page-item-161"><a href="/oauth2-servers/authorization/the-authorization-request/" data-section="9.1">The Authorization Request</a></li> <li class="page_item page-item-164"><a href="/oauth2-servers/authorization/requiring-user-login/" data-section="9.2">Requiring User Login</a></li> <li class="page_item page-item-166"><a href="/oauth2-servers/authorization/the-authorization-interface/" data-section="9.3">The Authorization Interface</a></li> <li class="page_item page-item-168"><a href="/oauth2-servers/authorization/the-authorization-response/" data-section="9.4">The Authorization Response</a></li> <li class="page_item page-item-170 current_page_item"><a href="/oauth2-servers/authorization/security-considerations/" data-section="9.5">Security Considerations</a></li> </ul> </li> <li class="page_item page-item-174 page_item_has_children"><a href="/oauth2-servers/scope/" data-section="10">Scope</a> <ul class='children'> <li class="page_item page-item-177"><a href="/oauth2-servers/scope/defining-scopes/" data-section="10.1">Defining Scopes</a></li> <li class="page_item page-item-179"><a href="/oauth2-servers/scope/user-interface/" data-section="10.2">User Interface</a></li> <li class="page_item page-item-181"><a href="/oauth2-servers/scope/checkboxes/" data-section="10.3">Checkboxes</a></li> </ul> </li> <li class="page_item page-item-184 page_item_has_children"><a href="/oauth2-servers/redirect-uris/" data-section="11">Redirect URLs</a> <ul class='children'> <li class="page_item page-item-186"><a href="/oauth2-servers/redirect-uris/redirect-uri-registration/" data-section="11.1">Redirect URL Registration</a></li> <li class="page_item page-item-188"><a href="/oauth2-servers/redirect-uris/redirect-uris-native-apps/" data-section="11.2">Redirect URLs for Native Apps</a></li> <li class="page_item page-item-190"><a href="/oauth2-servers/redirect-uris/redirect-uri-validation/" data-section="11.3">Redirect URL Validation</a></li> </ul> </li> <li class="page_item page-item-194 page_item_has_children"><a href="/oauth2-servers/access-tokens/" data-section="12">Access Tokens</a> <ul class='children'> <li class="page_item page-item-196"><a href="/oauth2-servers/access-tokens/authorization-code-request/" data-section="12.1">Authorization Code Request</a></li> <li class="page_item page-item-198"><a href="/oauth2-servers/access-tokens/password-grant/" data-section="12.2">Password Grant</a></li> <li class="page_item page-item-200"><a href="/oauth2-servers/access-tokens/client-credentials/" data-section="12.3">Client Credentials</a></li> <li class="page_item page-item-202"><a href="/oauth2-servers/access-tokens/access-token-response/" data-section="12.4">Access Token Response</a></li> <li class="page_item page-item-204"><a href="/oauth2-servers/access-tokens/self-encoded-access-tokens/" data-section="12.5">Self-Encoded Access Tokens</a></li> <li class="page_item page-item-206"><a href="/oauth2-servers/access-tokens/access-token-lifetime/" data-section="12.6">Access Token Lifetime</a></li> <li class="page_item page-item-208"><a href="/oauth2-servers/access-tokens/refreshing-access-tokens/" data-section="12.7">Refreshing Access Tokens</a></li> </ul> </li> <li class="page_item page-item-210 page_item_has_children"><a href="/oauth2-servers/listing-authorizations/" data-section="13">Listing Authorizations</a> <ul class='children'> <li class="page_item page-item-212"><a href="/oauth2-servers/listing-authorizations/revoking-access/" data-section="13.1">Revoking Access</a></li> </ul> </li> <li class="page_item page-item-216"><a href="/oauth2-servers/the-resource-server/" data-section="14">The Resource Server</a></li> <li class="page_item page-item-608 page_item_has_children"><a href="/oauth2-servers/oauth-native-apps/" data-section="15">OAuth for Native Apps</a> <ul class='children'> <li class="page_item page-item-614"><a href="/oauth2-servers/oauth-native-apps/use-system-browser/" data-section="15.1">Use a System Browser</a></li> <li class="page_item page-item-620"><a href="/oauth2-servers/oauth-native-apps/redirect-urls-for-native-apps/" data-section="15.2">Redirect URLs for Native Apps</a></li> <li class="page_item page-item-626"><a href="/oauth2-servers/oauth-native-apps/pkce/" data-section="15.3">PKCE Extension</a></li> <li class="page_item page-item-627"><a href="/oauth2-servers/oauth-native-apps/checklist-server-support-native-apps/" data-section="15.4">Checklist for Server Support for Native Apps</a></li> </ul> </li> <li class="page_item page-item-640 page_item_has_children"><a href="/oauth2-servers/device-flow/" data-section="16">OAuth for Browserless and Input-Constrained Devices</a> <ul class='children'> <li class="page_item page-item-643"><a href="/oauth2-servers/device-flow/user-flow/" data-section="16.1">User Flow</a></li> <li class="page_item page-item-656"><a href="/oauth2-servers/device-flow/authorization-request/" data-section="16.2">Authorization Request</a></li> <li class="page_item page-item-660"><a href="/oauth2-servers/device-flow/token-request/" data-section="16.3">Token Request</a></li> <li class="page_item page-item-662"><a href="/oauth2-servers/device-flow/authorization-server-requirements/" data-section="16.4">Authorization Server Requirements</a></li> <li class="page_item page-item-666"><a href="/oauth2-servers/device-flow/security-considerations/" data-section="16.5">Security Considerations</a></li> </ul> </li> <li class="page_item page-item-668 page_item_has_children"><a href="/oauth2-servers/pkce/" data-section="17">Protecting Apps with PKCE</a> <ul class='children'> <li class="page_item page-item-670"><a href="/oauth2-servers/pkce/authorization-request/" data-section="17.1">Authorization Request</a></li> <li class="page_item page-item-673"><a href="/oauth2-servers/pkce/authorization-code-exchange/" data-section="17.2">Authorization Code Exchange</a></li> </ul> </li> <li class="page_item page-item-214"><a href="/oauth2-servers/token-introspection-endpoint/" data-section="18">Token Introspection Endpoint</a></li> <li class="page_item page-item-220"><a href="/oauth2-servers/creating-documentation/" data-section="19">Creating Documentation</a></li> <li class="page_item page-item-108"><a href="/oauth2-servers/definitions/" data-section="20">Terminology Reference</a></li> <li class="page_item page-item-136 page_item_has_children"><a href="/oauth2-servers/differences-between-oauth-1-2/" data-section="21">Differences Between OAuth 1 and 2</a> <ul class='children'> <li class="page_item page-item-225"><a href="/oauth2-servers/differences-between-oauth-1-2/authentication-and-signatures/" data-section="21.1">Authentication and Signatures</a></li> <li class="page_item page-item-227"><a href="/oauth2-servers/differences-between-oauth-1-2/user-experience-alternative-token-issuance-options/" data-section="21.2">User Experience and Alternative Token Issuance Options</a></li> <li class="page_item page-item-229"><a href="/oauth2-servers/differences-between-oauth-1-2/performance-at-scale/" data-section="21.3">Performance at Scale</a></li> <li class="page_item page-item-231"><a href="/oauth2-servers/differences-between-oauth-1-2/bearer-tokens/" data-section="21.4">Bearer Tokens</a></li> <li class="page_item page-item-233"><a href="/oauth2-servers/differences-between-oauth-1-2/short-lived-tokens-long-lived-authorizations/" data-section="21.5">Short-lived tokens with Long-lived authorizations</a></li> <li class="page_item page-item-235"><a href="/oauth2-servers/differences-between-oauth-1-2/separation-of-roles/" data-section="21.6">Separation of Roles</a></li> </ul> </li> <li class="page_item page-item-676 page_item_has_children"><a href="/oauth2-servers/openid-connect/" data-section="22">OpenID Connect</a> <ul class='children'> <li class="page_item page-item-678"><a href="/oauth2-servers/openid-connect/authorization-vs-authentication/" data-section="22.1">Authorization vs Authentication</a></li> <li class="page_item page-item-680"><a href="/oauth2-servers/openid-connect/building-an-authentication-framework/" data-section="22.2">Building an Authentication Framework</a></li> <li class="page_item page-item-682"><a href="/oauth2-servers/openid-connect/id-tokens/" data-section="22.3">ID Tokens</a></li> <li class="page_item page-item-684"><a href="/oauth2-servers/openid-connect/summary/" data-section="22.4">Summary</a></li> </ul> </li> <li class="page_item page-item-686 page_item_has_children"><a href="/oauth2-servers/indieauth/" data-section="23">IndieAuth</a> <ul class='children'> <li class="page_item page-item-738"><a href="/oauth2-servers/indieauth/discovery/" data-section="23.1">Discovery</a></li> <li class="page_item page-item-688"><a href="/oauth2-servers/indieauth/sign-in/" data-section="23.2">IndieAuth Sign-In Workflow</a></li> <li class="page_item page-item-690"><a href="/oauth2-servers/indieauth/authorization/" data-section="23.3">IndieAuth Authorization Workflow</a></li> </ul> </li> <li class="page_item page-item-693"><a href="/oauth2-servers/map-oauth-2-0-specs/" data-section="24">Map of OAuth 2.0 Specs</a></li> <li class="page_item page-item-697"><a href="/oauth2-servers/tools-and-libraries/" data-section="25">Tools and Libraries</a></li> <li class="page_item page-item-715"><a href="/oauth2-servers/appendix/">Appendix</a></li> </ul> </li> </ul>  </nav>   <a id="menu-icon-close" href="#"> <?xml version="1.0" encoding="UTF-8"?> <svg width="15px" height="15px" viewBox="0 0 15 15" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">  <title>Close</title> <desc>Created with Sketch.</desc> <defs></defs> <g id="Design" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd"> <g id="OAuth---Table-of-Contents-Menu" transform="translate(-1292.000000, -30.000000)" fill-rule="nonzero" fill="#333333"> <g id="ToC-Menu-Open" transform="translate(993.000000, -16.000000)"> <g id="Close" transform="translate(299.000000, 46.000000)"> <path d="M15.9149259,8.53193792 L-1.05529018,8.53193792 C-1.56341203,8.53193792 -1.97626292,8.12026136 -1.97626292,7.61096518 L-1.97626292,7.24987497 C-1.97626292,6.74175311 -1.56458636,6.32890222 -1.05529018,6.32890222 L15.9161303,6.32890222 C16.4242522,6.32890222 16.8371031,6.74057879 16.8371031,7.24987497 L16.8371031,7.61096518 C16.8359266,8.12026136 16.4242522,8.53193792 15.914956,8.53193792 L15.9149259,8.53193792 Z" id="Shape" transform="translate(7.430420, 7.430420) rotate(-315.000000) translate(-7.430420, -7.430420) "></path> <path d="M15.9149259,8.53193792 L-1.05529018,8.53193792 C-1.56341203,8.53193792 -1.97626292,8.12026136 -1.97626292,7.61096518 L-1.97626292,7.24987497 C-1.97626292,6.74175311 -1.56458636,6.32890222 -1.05529018,6.32890222 L15.9161303,6.32890222 C16.4242522,6.32890222 16.8371031,6.74057879 16.8371031,7.24987497 L16.8371031,7.61096518 C16.8359266,8.12026136 16.4242522,8.53193792 15.914956,8.53193792 L15.9149259,8.53193792 Z" id="Shape-Copy" transform="translate(7.430420, 7.430420) scale(-1, 1) rotate(-315.000000) translate(-7.430420, -7.430420) "></path> </g> </g> </g> </g> </svg> </a> </div>  </header>  </div>  <div id="body" class="clearfix">  <div id="valprop"> <header class="valprop-content"> <h1 class="page-title"> Security Considerations </h1> </header> <span class="section-number">9.5</span> </div>   <div id="layout" class="pagewidth-narrow clearfix">  <div id="content" class="clearfix"> <div id="page-170" class="type-page">  <time datetime="2016-08-17"></time> <h1 class="page-title"> </h1>  <div class="page-content entry-content"> <p>Below are some known issues that should be taken into consideration when building an authorization server.</p> <p>In addition to the considerations listed here, there is more information available in the <a href="https://oauth.net/2/security-considerations/">OAuth 2.0 Thread Model and Security Considerations</a> RFC as well as <a href="https://oauth.net/2/oauth-best-practice/">OAuth 2.0 Security Best Current Practice</a>.</p> <h2>Phishing Attacks</h2> <p>One potential attack against OAuth servers is a phishing attack. This is where an attacker makes a web page that looks identical to the service’s authorization page, which typically contain username and password fields. Then, through various means, the attacker can trick the user in to visiting the page. Unless the user can inspect the address bar of the browser, the page may look otherwise identical to the genuine authorization page, and the user may enter their username and password.</p> <p>One way attackers can attempt to trick the user into visiting the counterfeit server is by embedding this phishing page in an embedded web view in a native application. Since embedded web views don’t show the address bar, the user then has no way to visually confirm they are on the legitimate site. This is unfortunately common in mobile applications, and often justified by the developer wanting to provide a better user experience by keeping the user in the application through the entire login process. Some OAuth providers encourage third party applications to either open a web browser or launch the provider’s native application instead of allowing them to embed an authorization page in a web view.</p> <h3>Countermeasures</h3> <p>Ensure the authorization server is served via https to avoid DNS spoofing.</p> <p>The authorization server should educate developers of the risks of phishing attacks, and can take steps to prevent the page from being embedded in native applications or in iframes.</p> <p>Users should be educated about the dangers of phishing attacks, and should be taught best practices such as only accessing applications that they trust, and periodically reviewing the list of applications they’ve authorized to <a href="/oauth2-servers/listing-authorizations/revoking-access/">revoke access</a> to apps they no longer use.</p> <p>The service may want to validate third-party applications prior to allowing other users to use the application. Services such as Instagram and Dropbox currently do this, where upon initial creation of an application, the app is only usable by the developer or other whitelisted user accounts. After the app is submitted for approval and reviewed, then it can be used by the whole user base of the service. This gives the service a chance to inspect how the application interacts with the service.</p> <h2>Clickjacking</h2> <p>In a clickjacking attack, the attacker creates a malicious website in which it loads the authorization server URL in a transparent iframe above the attacker’s web page. The attacker’s web page is stacked below the iframe, and has some innocuous-looking buttons or links, placed very carefully to be directly under the authorization server’s confirmation button. When the user clicks the misleading visible button, they are actually clicking the invisible button on the authorization page, thereby granting access to the attacker’s application. This allows the attacker to trick the user into granting access without their knowledge.</p> <h3>Countermeasures</h3> <p>This kind of attack can be prevented by ensuring the authorization URL is always loaded directly in a native browser, and not embedded in an iframe. Newer browsers have the ability for the authorization server to set an HTTP header, <code>X-Frame-Options</code>, and older browsers can use common Javascript “frame-busting” techniques.</p> <h2>Redirect URL Manipulation</h2> <p>An attacker can construct an authorization URL using a client ID that belongs to a known good application, but set the redirect URL to a URL under the control of the attacker. If the authorization server does not validate redirect URLs, and the attacker uses the “token” response type, the user will be returned to the attacker’s application with the access token in the URL. If the client is a public client, and the attacker intercepts the authorization code, then the attacker can also exchange the code for an access token.</p> <p>Another similar attack is when the attacker can spoof the user’s DNS, and the registered redirect is not an https URL. This would allow the attacker to pretend to be the valid redirect URL, and steal the access token that way.</p> <p>The “Open Redirect” attack is when the authorization server does not require an exact match of the redirect URL, and instead allows an attacker to construct a URL that will redirect to the attacker’s website. Whether or not this ends up being used to steal authorization codes or access tokens, this is also a danger in that it can be used to launch other unrelated attacks. More details about the Open Redirect attack can be found at <a href="https://oauth.net/advisories/2014-1-covert-redirect/">https://oauth.net/advisories/2014-1-covert-redirect/</a>.</p> <h3>Countermeasures</h3> <p>The authorization server must require that one or more redirect URLs are registered by the application, and only redirect to an exact match of a previously registered URL.</p> <p>The authorization server should also require that all redirect URLs are https. Since this can sometimes be a burden during development, it is also acceptable to allow non-https redirect URLs while the application is “in development” and can only be accessed by the developer, and then require that the redirect URL is changed to an https URL before the application is published and available to other users.</p> <div id="themify_builder_content-170" data-postid="170" class="themify_builder_content themify_builder_content-170 themify_builder"> </div>    </div>  </div> </div>  <nav id="page"> <div class="alignleft"> <a href="/oauth2-servers/authorization/the-authorization-response/"><span>Previous Chapter</span>The Authorization Response</a> </div> <div class="alignright"> <a href="/oauth2-servers/scope/"><span>Next Chapter</span>Scope</a> </div> </nav> </div>  </div>  <div id="footerwrap" > <footer id="footer" class="pagewidth clearfix" itemscope="itemscope" itemtype="https://schema.org/WPFooter"> <div class="Row u-Flex u-Stretch"> <div class="no-hassle Column--6 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