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@tadast
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Last active June 19, 2025 23:35
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localhost SSL with puma
# 1) Create your private key (any password will do, we remove it below)
$ cd ~/.ssh
$ openssl genrsa -des3 -out server.orig.key 2048
# 2) Remove the password
$ openssl rsa -in server.orig.key -out server.key
# 3) Generate the csr (Certificate signing request) (Details are important!)
$ openssl req -new -key server.key -out server.csr
# IMPORTANT
# MUST have localhost.ssl as the common name to keep browsers happy
# (has to do with non internal domain names ... which sadly can be
# avoided with a domain name with a "." in the middle of it somewhere)
Country Name (2 letter code) [AU]:
...
Common Name: localhost.ssl
...
# 4) Generate self signed ssl certificate
$ openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt
# 5) Finally Add localhost.ssl to your hosts file
$ echo "127.0.0.1 localhost.ssl" | sudo tee -a /private/etc/hosts
# 6) Boot puma
$ puma -b 'ssl://127.0.0.1:3000?key=/Users/tadas/.ssh/server.key&cert=/Users/tadas/.ssh/server.crt'
# 7) Add server.crt as trusted !!SYSTEM!! (not login) cert in the mac osx keychain
# Open keychain tool, drag .crt file to system, and trust everything.
# Notes:
# 1) Https traffic and http traffic can't be served from the same process. If you want
# both you need to start two instances on different ports.
#
#
@anon987654321
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For what it's worth, here's a simpler and more secure alternative to Linux for hosting your static sites and Rails apps on the same server: https://gist.github.com/anon987654321/4532cf8d6c59c1f43ec8973faa031103

@TheNotary
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I'm seeing this error on modern versions of Chrome.

2020-06-26 09:23:21 -0500: SSL error, peer: 127.0.0.1, peer cert: , #<Puma::MiniSSL::SSLError: OpenSSL error: error:141F7065:SSL routines:final_key_share:no suitable key share - 337604709>

According to google, this indicates that the cert generated in this guide is insecure and not supported in SSL 1.3

@anon987654321
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OpenSSL is fundamentally insecure. I'd recommend checking out my gist above which is based on OpenBSD's OpenSSL rewrite LibreSSL:

https://www.libressl.org/

OpenBSD's acme-client is also the most secure cert generator around. Check it out!

@TheNotary
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Can such cert be generated on a mac, @anon987654321? I'd love to get away from openssl, but it seems like it's the only TLS group that figured out how to do distribution of their software (which is clearly a bit less than ideal given their quality track record).

@liam-le-goldenowl
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thank you, it work for me

@etozzato
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etozzato commented Aug 6, 2021

Thank you for this great thread!

This is my adaptation: https://gist.github.com/etozzato/0ba2140ea3c6125d4839373309fe733a

  • Allows for a domain and wildcard subdomain;
  • Cleans up after itself in case of error;
  • Will still boot puma (no SSL) in case of error;

@basicfeatures
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@TheNotary thanks for getting back at me. You'd probably have to spawn a new server using OpenBSD, check out:

https://github.com/basicfeatures/openbsd-rails

Does SSL/TLS termination before Puma as Puma isn't really suited for this. Check out https://github.com/ErwinM/acts_as_tenant for multiple domains/subdomains, or message me.

@etozzato I might be wrong, but your gist looks over-engineered.

@etozzato
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@etozzato I might be wrong, but your gist looks over-engineered.

yes, it's plausible! 👍

@calebhaye
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calebhaye commented Sep 27, 2021

You can generate a trusted localhost cert by using letsencrypt and creating a certificate like localhost.domain.com (or *.localhost.domain.com for wildcards), verify that with a dns challenge, which usually involves creating an _acme_challenge TXT record. Then, once you have passed the challenges and have the cert, point localhost.domain.com to 127.0.0.1

If you have a multi-tenant app, you can create a wildcard cert also, but you'll have to go through the extra step of manually adding subdomains to localhost.domain.com to/etc/hosts and your config/enviroments/development.rb (assuming this is a rails app)

@allencch
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In order to run with Rails (version 7),

bin/rails s -u puma -b 'ssl://127.0.0.1:3000?key=server.key&cert=server.crt&verify_mode=peer&ca=server.crt'

@pirkka
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pirkka commented May 27, 2022

There is a fantastic tool called mkcert which eliminates most of the pain of generating self signed certs and installing them as trusted certs on your machine - https://github.com/FiloSottile/mkcert. Way easier than trying wrangle OpenSSL commands and APIs.

I would like to recommend this approach as well.

I am no SSL guru, so I had a long battle trying to get local SSL to work a my new computer (it works fine on my older one). At some point I even had subjectively non-deterministic results where my SSL would work for a minute or two and then stop working with no apparent change in anything.

Using the mkcert on my macOS computer via homebrew solved the problem very quickly and easily.

@chaffeqa
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I created a fork of @etozzato great sample, but added automatic local trusting per OS:

https://gist.github.com/chaffeqa/d6c6ac491d3e1824a2980607d796e4a8

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