Create self signed certificate with subjectAltName to fix [missing_subjectAltName] in Chrome 58+

While reading the documentation for subjectAltName, I noticed, that my certificate has shown Version: 1 while the documentation show Version: 3.

To get a Version 3 certificate, I specified the -extfile option:

sudo openssl x509 -req -in ./../nginx/ssl/${filename}.csr -CA ~/ssl/rootCA.pem -CAkey ~/ssl/rootCA.key -CAcreateserial -out ./../nginx/ssl/${filename}.crt -days 500 -sha256 -extfile v3.ext

v3.ext looks like this:

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

[alt_names]
DNS.1 = localhost

When running openssl x509 -text -in ../nginx/ssl/server.crt -noout again, the certificate now also contains the Subject Alternative Name section:

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 17237690484651272016 (0xef38942aa5c52750)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=US, ST=New York, L=Rochester, O=End Point, CN=localhost/[email protected]
        Validity
            Not Before: Apr 23 16:07:38 2017 GMT
            Not After : Sep  5 16:07:38 2018 GMT
        Subject: C=US, ST=New York, L=Rochester, O=End Point, OU=Testing Domain/emailAddress=your-administrative-address@your-awesome-existing-domain.com, CN=localhost
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    00:b2:e3:bd:ed:28:04:85:ea:75:ee:d2:82:e1:eb:
                    f5:5f:7f:cf:7e:cb:70:de:86:9f:75:7c:f3:71:e7:
                    da:16:fb:bc:1f:89:bc:47:08:77:ca:33:20:f1:c1:
                    9e:e3:20:8d:89:14:7e:c1:0a:12:d2:59:24:56:9b:
                    77:90:5f:69:d1:a5:f1:00:38:93:1b:a7:75:f1:33:
                    e2:da:dc:32:a9:0a:85:7d:9a:20:81:ca:20:ee:86:
                    ce:e2:a0:52:d2:ab:11:34:e5:52:99:3a:81:c6:9f:
                    6b:0f:6a:02:2b:38:a6:84:c9:ba:fa:9b:ef:0a:89:
                    22:4b:79:86:3c:bd:44:a5:54:fb:cf:4d:8b:d1:44:
                    03:35:22:de:69:77:c8:fa:4d:c6:01:25:08:9f:4d:
                    a9:79:7a:aa:ca:03:b6:e4:51:57:22:27:5f:a7:12:
                    11:f3:e6:00:29:f6:58:be:2c:aa:09:e4:06:45:d9:
                    3f:75:a7:f0:75:bd:2b:a6:bb:6d:ad:93:bb:b9:1d:
                    d7:75:39:4e:9b:1d:0e:39:cc:17:74:88:f7:e2:b7:
                    85:12:96:e0:cb:42:56:d0:11:e0:84:86:e5:14:a5:
                    f2:6d:43:5d:f9:59:ae:61:7f:01:ae:95:b8:92:27:
                    1d:1c:02:d7:ad:fb:ee:f6:25:38:60:c8:41:20:17:
                    80:69
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Authority Key Identifier:
                keyid:5A:8D:89:64:BD:F2:3E:C2:D7:7B:BE:17:84:F4:29:E8:C5:32:35:34

            X509v3 Basic Constraints:
                CA:FALSE
            X509v3 Key Usage:
                Digital Signature, Non Repudiation, Key Encipherment, Data Encipherment
            X509v3 Subject Alternative Name:
                DNS:localhost
    Signature Algorithm: sha256WithRSAEncryption
         27:1d:d6:84:50:33:d2:ff:b1:06:9b:fa:f1:40:7d:47:11:bc:
         f7:80:fd:26:87:0e:91:9f:14:be:1f:1d:9b:32:d1:fb:d6:8d:
         af:30:8a:88:38:8c:1c:bf:77:98:8e:cd:06:48:82:fa:09:b9:
         3c:0d:38:c4:a0:da:b7:4d:f5:81:5f:5a:76:04:61:f8:c2:1a:
         17:ad:56:7c:72:ba:f6:65:7f:7f:e7:5e:b2:34:ba:13:23:57:
         84:f1:c5:ca:dd:5b:55:69:95:71:44:4a:30:53:61:5c:ad:47:
         d8:9c:d5:a2:1b:18:2d:e1:19:35:3e:3f:b2:7e:fd:bf:f3:d0:
         45:dc:f5:57:f0:1b:cd:70:1b:e0:34:de:27:98:89:b4:a5:25:
         a5:6c:29:c3:89:a6:a5:c5:4d:f5:45:3b:47:8e:13:45:23:07:
         5e:d6:59:0d:96:c6:a3:f0:c5:3d:ee:a8:ad:36:96:43:13:a1:
         b8:55:f6:c7:10:7e:8f:5d:09:ef:61:17:2a:9c:3b:50:28:c8:
         e3:8d:a6:34:06:50:d4:3e:d5:17:ea:7d:31:97:d3:ee:df:b5:
         23:66:5e:22:b7:e4:fa:36:4f:9a:d5:f0:a3:f9:b4:2b:27:02:
         0b:41:94:d1:a1:f7:1b:2c:7e:74:e6:14:c3:b5:67:15:d2:ca:
         02:77:57:a6

I also created a blog post.

If you want to add 127.0.0.1, you must write:

[alt_names]
IP.1 = 127.0.0.1

If you add DNS.1 = 127.0.0.1 Chrome will return a ERR_CERT_COMMON_NAME_INVALID.

Thanks to @Robar for pointing this out in the comments.

In Windows, save this script in your SSL folder as makeCert.bat. The self-signed certificate it makes will satisfy Chrome ver 58+ requirement for SAN (Subject Alternative Name).

This script will create these files: example.cnf, example.crt, example.key

@echo off

REM IN YOUR SSL FOLDER, SAVE THIS FILE AS: makeCert.bat
REM AT COMMAND LINE IN YOUR SSL FOLDER, RUN: makecert
REM IT WILL CREATE THESE FILES: example.cnf, example.crt, example.key
REM IMPORT THE .crt FILE INTO CHROME Trusted Root Certification Authorities
REM REMEMBER TO RESTART APACHE OR NGINX AFTER YOU CONFIGURE FOR THESE FILES

REM PLEASE UPDATE THE FOLLOWING VARIABLES FOR YOUR NEEDS.
SET HOSTNAME=example
SET DOT=com
SET COUNTRY=US
SET STATE=KS
SET CITY=Olathe
SET ORGANIZATION=IT
SET ORGANIZATION_UNIT=IT Department
SET EMAIL=webmaster@%HOSTNAME%.%DOT%

(
echo [req]
echo default_bits = 2048
echo prompt = no
echo default_md = sha256
echo x509_extensions = v3_req
echo distinguished_name = dn
echo:
echo [dn]
echo C = %COUNTRY%
echo ST = %STATE%
echo L = %CITY%
echo O = %ORGANIZATION%
echo OU = %ORGANIZATION_UNIT%
echo emailAddress = %EMAIL%
echo CN = %HOSTNAME%.%DOT%
echo:
echo [v3_req]
echo subjectAltName = @alt_names
echo:
echo [alt_names]
echo DNS.1 = *.%HOSTNAME%.%DOT%
echo DNS.2 = %HOSTNAME%.%DOT%
)>%HOSTNAME%.cnf

openssl req -new -x509 -newkey rsa:2048 -sha256 -nodes -keyout %HOSTNAME%.key -days 3560 -out %HOSTNAME%.crt -config %HOSTNAME%.cnf