Invalid self signed SSL cert - "Subject Alternative Name Missing"

To fix this, you need to supply an extra parameter to openssl when you're creating the cert, basically

-sha256 -extfile v3.ext

where v3.ext is a file like so, with %%DOMAIN%% replaced with the same name you use as your Common Name. More info here and over here. Note that typically you'd set the Common Name and %%DOMAIN%% to the domain you're trying to generate a cert for. So if it was www.mysupersite.com, then you'd use that for both.

v3.ext

authorityKeyIdentifier=keyid,issuerbasicConstraints=CA:FALSEkeyUsage = digitalSignature, nonRepudiation, keyEncipherment, dataEnciphermentsubjectAltName = @alt_names[alt_names]DNS.1 = %%DOMAIN%%

Note: Scripts that address this issue, and create fully trusted ssl certs for use in Chrome, Safari and from Java clients can be found here

Another note: If all you're trying to do is stop chrome from throwing errors when viewing a self signed certificate, you can can tell Chrome to ignore all SSL errors for ALL sites by starting it with a special command line option, as detailed here on SuperUser

Following solution worked for me on chrome 65 (ref) -

Create an OpenSSL config file (example: req.cnf)

[req]distinguished_name = req_distinguished_namex509_extensions = v3_reqprompt = no[req_distinguished_name]C = USST = VAL = SomeCityO = MyCompanyOU = MyDivisionCN = www.company.com[v3_req]keyUsage = critical, digitalSignature, keyAgreementextendedKeyUsage = serverAuthsubjectAltName = @alt_names[alt_names]DNS.1 = www.company.comDNS.2 = company.comDNS.3 = company.net

Create the certificate referencing this config file

openssl req -x509 -nodes -days 730 -newkey rsa:2048 \ -keyout cert.key -out cert.pem -config req.cnf -sha256

The Issue

As others have mentioned, the NET::ERR_CERT_COMMON_NAME_INVALID error is occurring because the generated certificate does not include the SAN (subjectAltName) field.

RFC2818 has deprecated falling back to the commonName field since May of 2000. The use of the subjectAltName field has been enforced in Chrome since version 58 (see Chrome 58 deprecations).

OpenSSL accepts x509v3 configuration files to add extended configurations to certificates (see the subjectAltName field for configuration options).

Bash Script

I created a self-signed-tls bash script with straightforward options to make it easy to generate certificate authorities and sign x509 certificates with OpenSSL (valid in Chrome using the subjectAltName field).

The script will guide you through a series of questions to include the necessary information (including the subjectAltName field). You can reference the README.md for more details and options for automation.

Be sure to restart chrome after installing new certificates.

chrome://restart

Other Resources

• The Docker documentation has a great straightforward example for creating a self-signed certificate authority and signing certificates with OpenSSL.
• cfssl is also a very robust tool that is widely used and worth checking out.
• mkcert is a tool written in GoLang. It seems simple to use and great for local development.