This discussion on GitHub may give you hints about how OCSP might be integrated into the standard library in future. On the other hand, applications dont know whether certificates are revoked until they download the newer version of CRL. Please include the URL and the reason for the request.

The biggest offender is the use of InsecureSkipVerify.

How exactly will the arguments look like? The answer is TLS config. In our case, we will use minica to provision this for us. Even with OCSP / CRL support, your solution might be susceptible to design and implementation mistakes, opening a wide attack surface.

Another example would be identity stealing. Otherwise these instructions should suffice. Lets start by creating an Http client-server implementation in Go. You cant just use Gos defaults here because Go wont be able to verify and trust your self-signed certificate*. The second argument is the issuer of this certificate, here it is verifiedChains[0][1]. You can imagine the consequences. The only difference is that we will call the server on three different URLs to understand what is going on under the hood. This ensures all the three guarantees that we discussed earlier. We stand with Ukraine, and we stand for Ukraine. They should be able to verify the servers identity through a CA. Thats why this post has a security overview, the implementation details, and the what could go wrong section. Its essential to verify the CRL response signature to prevent potential attackers from tampering with the list.

Protecting data signals transmitted over the air between power distribution stations and central dispatch system. Lets take a look at ocsp.CreateRequest: The first argument is the certificate we are validating. That stolen private key makes it possible to perform MitM attacks on visitors, redirecting them to the malicious website instead of the real one or intercepting sensitive data. This is the part that most people run in to problems with. In reality, a Certificate Authority (CA) or a Domain Administrator (within an organization) will provide you a keypair and a signed certificate. Lets start with crafting the OCSP request. CRL disadvantages: there may be some time frame during which the application continues to use a revoked certificate before the new CRL is downloaded. Acra provides application level encryption, masking, tokenisation, access control, database leakage prevention, and intrusion detection for modern data-processing apps. The request is often sent as an unencrypted HTTP because the response is signed, decreasing the chances of its tampering. Below, cert.pem is the PEM-encoded certificate and key.pem is the PEM-encoded private key. This section hosts cryptographic research and whitepapers authored by Cossack Labs team. This is good news, which means the server is sending encrypted data. We create a pool of client CA certificates that the server should trust. The MIME types we are sending and expecting are application/ocsp-request and application/ocsp-response respectively. OCSP disadvantages: increased handshake time because of additional network request(s). Lets run a TLS server that uses a valid and non-revoked certificate: The client-side application connects to the server, receives a TLS certificate, checks the local cache for the CRL file, and searches if the certificate serial ID is present there.

However, implementing OCSP and CRL are a part of the application code. Lets take SHA256 instead of default SHA1: Now the buffer contains the request, serialized in a proper format, ready to be sent to the server. The ocspResponse.Status represents one of the following: Now, based on ocspResponse.Status, you can return nil or some custom error from the callback. Note: If generating these seems a hassle, you can reuse the certificates committed with the Github repository. CRL advantages: instant response (unless the cached CRL is outdated and should be downloaded again). The client should have a public certificate of CA-1 that has signed the servers certificate. OCSP advantages: the application finds out the certificate was revoked as soon as possible (time depends only on how often the application performs OCSP requests). Typically, setting up PKI components is done by the infrastructure engineers. The fastest way is to check the local CRL cache, but then the application wont know if the certificate was revoked lately. Mostly, we rely on cryptography, but it doesnt live in a vacuum. Would you like to join?

If the OCSP infrastructure is under attack, the application will continue talking to the already malicious service, treating it as valid.

At this point, our infrastructure setup is complete. OCSP and CRL provide a way to verify whether the TLS certificate was revoked by CA before the application establishes secure communication with a service that uses this certificate. Lets talk about how things could go wrong in using OCSP and CRL. Adding a custom certificate authority pool to your http.Client requires a few extra steps but is straightforward: And thats it. If there are any validation errors on either side, the connection will be aborted. This step is crucial to prevent tampering with CRLs. The sequence of the checking local CRL cache, downloading new CRL, and checking OCSP response matters. That should be a good starting place, even if you dont need to allow multiple domains and / or IP addresses. is by writing to standard output and standard error. NOTE : In a production system, it would be wise to use InsecureSkipVerify : true parameter if the normal/secure method failed. Even though the standard Golang library provides easy-to-use and secure TLS 1.3, it doesnt support OCSP and CRL protocol out-of-the-box. Therefore, we are dealing with a self-signed certificate that passed previous checks (is allowed by TLS config), and OCSP is not relevant in this case. Unfortunately, even though Golang has native support for TLS, it has extremely limited support for OCSP and CRL. environment with limited resources. If you understand the TLS protocol and handshake correctly, Go offers everything else you need right out of the box.

Documentation, tutorials, and guides, and a large collection of ready-to-try examples of Cossack Labs' products. Hope you may find it useful when you encounter the similar situation in future. Typical application and network security controls are necessary parts of surrounding infrastructure, and they, for various reasons, rely on OCSP and CRL to establish trust to remote parties. OCSP / CRL are the small bits, but theyre the connection tissue in the trust fabric of PKI in distributed applications. Use encryption where possible, prefer ciphers with PFS, and may the force be with you. Revokedthe certificate was revoked for some reason, and the app shouldnt trust it. Let use the key and certificate generated for the server-cert domain to configure TLS on the server. Stunned by losing their robotic devices, [REDACTED] learnt that they were hijacked by attackers even with communication being encrypted. Go uses your systems root certificate authority set by default, so if you add your certificate to this root set of certificates, you can use http.Client without modification. So, all our work from now on will be around this single callback: VerifyPeerCertificate. CRL does not require creating any particular request type. We will further explore how to set mutual-TLS encryption. We will start by writing a simple Http server and a client in Go. +24k Golang : How to create new XML file ? The client and the server certificates generated above are valid for the domains server-cert and client-cert respectively.

These domains do not exist, so we will create an alias for localhost (127.0.0.1). The client is the same as earlier.

For example, CRL cache TTL might differ from CRLs next update date; thus, the application checks for a new CRL more often.

But in a lot of use cases, the server needs to trust the client. Nginx), youll configure your certificate and key there. PKI consists of many moving parts: deployed services and admin procedures to manage them. You also shouldnt use self-signed certificates for public-facing endpoints. The standard library in Golang allows extracting such stapled OCSP responses, but they are not processed by default. Basically, just a custom HTTP transport client disabled security check. This tutorial is a note from helping a friend today to create a custom HTTP transport client in Golang. a certificate from CA. Any requests for content removal should be directed to CRL is a file that contains a list of certificates revoked by a single CAcertificates' serial numbers and reasons why they were revoked. However, for performance purposes, it would be better to build a map[bytes]pkix.RevokedCertificate after parsing the CRL for more efficient lookups. Attempt 2 to https://localhost:8080/server, the response is: Client Error: Get https://localhost:8080/server: x509: certificate is valid for server-cert, not localhost, Server Error: http: TLS handshake error from 127.0.0.1:35698: remote error: tls: bad certificate. Long caching may allow the attackers to use revoked certificates while the application treats them as valid. This way, the client does not need to perform additional network requests, only to validate the attached response. Only after performing all validation steps, the app should establish a TLS connection with the service. Thats why many TLS libraries have limited support for many of these extensions. Possible reasons include: the private key was compromised, the CA key was compromised, the user owning the mentioned certificate no longer belongs to the company. Golang: Establish secure HTTP connections with self-signed certificates. This is precisely what this post is about, but before diving into implementation details, lets talk about OCSP and CRL from the birds eye. Before we come to that stage, we should set up our public key infrastructure (PKI). See the signature validation in our example or refer to Go crypto/x509 docs. This post is hugely inspired by this wonderful talk by Liz Rice in Gophercon-2018, please check it out. that you use a unique user agent in your requests (so we can identify you), It depends on a threat model and security requirements. However, CRLs have a certain lifetime, so your cache should have an expiration feature. This may be caused by a misconfiguration or delays in OCSP server database updates. server-cert/cert.pem (certificate for domain server-cert, signed by roots public key), server-cert/key.pem (private key for domain server-cert), client-cert/cert.pem (certificate for domain client-cert), client-cert/key.pem (private key for domain client-cert). Copyright 2014-2022 Cossack Labs Limited, 113274642861313425704666455845030198894915511470, 547114458127197346809836113712612368226057720033, I consent for this website to store my submitted information and accept, Configuring TLS for OCSP and CRL in Golang, OCSP (Online Certificate Status Protocol), GitHub repo cossacklabs/blogposts-examples, OWASP Transport Layer Protection Cheat Sheet.