Private CA and self signed certs that work with Chrome

Warning

⚠️ 💩 ⚠️

This method is for testing and development only.
The vast majority of users should not use this method, as it requires loading a cert on each of your devices, which is both error-prone and requires future maintenance.
Instead, focus your energy on obtaining real certs via Let's Encrypt.
This can even work if your vaultwarden instance is not on the public Internet (example).

☠️ ☠️ ☠️

This method is not supported.
Please do not open GitHub issues or post on the discussion forums asking about how to get this to work.

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To get bitwarden working properly with self-signed certificates, Chrome needs the certificate to include the domain name in the alternative name field of the certificate.

Create a CA key (your own little on-premise Certificate Authority):

openssl genpkey -algorithm RSA -aes128 -out private-ca.key -outform PEM -pkeyopt rsa_keygen_bits:2048

Instead of -aes128 you could also use the older -des3.

Create a CA certificate:

openssl req -x509 -new -nodes -sha256 -days 3650 -key private-ca.key -out self-signed-ca-cert.crt

The -nodes argument prevents setting a pass-phrase for the private key (key pair) in a test/safe environment, otherwise you'll have to input the pass-phrase every time you start/restart the server.

Create a bitwarden key:

openssl genpkey -algorithm RSA -out bitwarden.key -outform PEM -pkeyopt rsa_keygen_bits:2048

Create the bitwarden certificate request file:

openssl req -new -key bitwarden.key -out bitwarden.csr

Create a text file bitwarden.ext with the following content, change the domain names to your setup.

authorityKeyIdentifier=keyid,issuer
basicConstraints=CA:TRUE
keyUsage = digitalSignature, nonRepudiation, keyEncipherment, dataEncipherment
extendedKeyUsage = serverAuth
subjectAltName = @alt_names

[alt_names]
DNS.1 = bitwarden.local
DNS.2 = www.bitwarden.local
# Optionally add IP if you're not using DNS names:
IP.1 = 192.168.1.3

Create the bitwarden certificate, signed from the root CA:

openssl x509 -req -in bitwarden.csr -CA self-signed-ca-cert.crt -CAkey private-ca.key -CAcreateserial -out bitwarden.crt -days 365 -sha256 -extfile bitwarden.ext

Note: As of April 2019 iOS 13+ and macOS 15+, the server certificate can not have an expiry > 825 and must include ExtendedKeyUsage extension https://support.apple.com/en-us/HT210176

Note: As of Android 11, the basicConstraints value must be set to CA:TRUE in order to be importable via the Settings app.

Add the root certificate and the bitwarden certificate to client computers.

For reference, see here: https://deliciousbrains.com/ssl-certificate-authority-for-local-https-development/