This is a text-only version of the following page on https://raymii.org: --- Title : OCSP Stapling on nginx Author : Remy van Elst Date : 03-02-2014 URL : https://raymii.org/s/tutorials/OCSP_Stapling_on_nginx.html Format : Markdown/HTML --- When connecting to a server, clients should verify the validity of the server certificate using either a Certificate Revocation List (CRL), or an Online Certificate Status Protocol (OCSP) record. The problem with CRL is that the lists have grown huge and takes forever to download. OCSP is much more lightweight, as only one record is retrieved at a time. But the side effect is that OCSP requests must be made to a 3rd party OCSP responder when connecting to a server, which adds latency and potential failures. In fact, the OCSP responders operated by CAs are often so unreliable that browser will fail silently if no response is received in a timely manner. This reduces security, by allowing an attacker to DoS an OCSP responder to disable the validation.

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The solution is to allow the server to send its cached OCSP record during the TLS handshake, therefore bypassing the OCSP responder. This mechanism saves a roundtrip between the client and the OCSP responder, and is called OCSP Stapling. The server will send a cached OCSP response only if the client requests it, by announcing support for the status_request TLS extension in its CLIENT HELLO. Most servers will cache OCSP response for up to 48 hours. At regular intervals, the server will connect to the OCSP responder of the CA to retrieve a fresh OCSP record. The location of the OCSP responder is taken from the Authority Information Access field of the signed certificate. [This tutorial is also available for Apache][2] ### What is OCSP Stapling OCSP stapling is defined in the [IETF RFC 6066][3]. The term "stapling" is a popular term used to describe how the OCSP response is obtained by the web server. The web server caches the response from the CA that issued the certificate. When an SSL/TLS handshake is initiated, the response is returned by the web server to the client by attaching the cached OCSP response to the CertificateStatus message. To make use of OCSP stapling, a client must include the "status_request" extension with its SSL/TSL Client "Hello" message. OCSP stapling presents several advantages including the following: * The relying party receives the status of the web servers certificate when it is needed (during the SSL/TLS handshake). * No additional HTTP connection needs to be set up with the issuing CA. * OCSP stapling provides added security by reducing the number of attack vectors. [Read][4] [one][5] [of][6] [the][7] [following][8] [links][9] for [more][10] information on OCSP and OCSP stapling. ### Requirements You need at least nginx 1.3.7 for this to work. This is not available in the current Ubuntu LTS releases (12.04), [it has 1.1.19][11] and on CentOS you need EPEL or the official repositories. However, it is easy [to install the latest version of nginx.][12] You also need create a firewall exception to allow your server to make outbound connections to the upstream OCSP's. You can view all OCSP URI's from a website using this one liner: OLDIFS=$IFS; IFS=':' certificates=$(openssl s_client -connect google.com:443 -showcerts -tlsextdebug -tls1 2>&1 . Just to be clear, the information on this website is for meant for educational purposes and you use it at your own risk. I do not take responsibility if you screw something up. Use common sense, do not 'rm -rf /' as root for example. If you have any questions then do not hesitate to contact me. See https://raymii.org/s/static/About.html for details.