Getting Chrome to accept self-signed localhost certificate

Question

I have created a self-signed SSL certificate for the localhost CN. Firefox accepts this certificate after initially complaining about it, as expected. Chrome and IE, however

Answer 1

On the Mac, you can create a certificate that's fully trusted by Chrome and Safari at the system level by doing the following:

    # create a root authority cert
    ./create_root_cert_and_key.sh
    
    # create a wildcard cert for mysite.com
    ./create_certificate_for_domain.sh mysite.com
    
    # or create a cert for www.mysite.com, no wildcards
    ./create_certificate_for_domain.sh www.mysite.com www.mysite.com

The above uses the following scripts, and a supporting file v3.ext, to avoid subject alternative name missing errors

If you want to create a new self signed cert that's fully trusted using your own root authority, you can do it using these scripts.

create_root_cert_and_key.sh

    #!/usr/bin/env bash
    openssl genrsa -out rootCA.key 2048
    openssl req -x509 -new -nodes -key rootCA.key -sha256 -days 1024 -out rootCA.pem

create_certificate_for_domain.sh

    #!/usr/bin/env bash
    
    if [ -z "$1" ]
    then
      echo "Please supply a subdomain to create a certificate for";
      echo "e.g. www.mysite.com"
      exit;
    fi
    
    if [ ! -f rootCA.pem ]; then
      echo 'Please run "create_root_cert_and_key.sh" first, and try again!'
      exit;
    fi
    if [ ! -f v3.ext ]; then
      echo 'Please download the "v3.ext" file and try again!'
      exit;
    fi
    
    # Create a new private key if one doesnt exist, or use the xeisting one if it does
    if [ -f device.key ]; then
      KEY_OPT="-key"
    else
      KEY_OPT="-keyout"
    fi
    
    DOMAIN=$1
    COMMON_NAME=${2:-*.$1}
    SUBJECT="/C=CA/ST=None/L=NB/O=None/CN=$COMMON_NAME"
    NUM_OF_DAYS=825
    openssl req -new -newkey rsa:2048 -sha256 -nodes $KEY_OPT device.key -subj "$SUBJECT" -out device.csr
    cat v3.ext | sed s/%%DOMAIN%%/"$COMMON_NAME"/g > /tmp/__v3.ext
    openssl x509 -req -in device.csr -CA rootCA.pem -CAkey rootCA.key -CAcreateserial -out device.crt -days $NUM_OF_DAYS -sha256 -extfile /tmp/__v3.ext 
    
    # move output files to final filenames
    mv device.csr "$DOMAIN.csr"
    cp device.crt "$DOMAIN.crt"
    
    # remove temp file
    rm -f device.crt;
    
    echo 
    echo "###########################################################################"
    echo Done! 
    echo "###########################################################################"
    echo "To use these files on your server, simply copy both $DOMAIN.csr and"
    echo "device.key to your webserver, and use like so (if Apache, for example)"
    echo 
    echo "    SSLCertificateFile    /path_to_your_files/$DOMAIN.crt"
    echo "    SSLCertificateKeyFile /path_to_your_files/device.key"

v3.ext

    authorityKeyIdentifier=keyid,issuer
    basicConstraints=CA:FALSE
    keyUsage = digitalSignature, nonRepudiation, keyEncipherment, dataEncipherment
    subjectAltName = @alt_names
    
    [alt_names]
    DNS.1 = %%DOMAIN%%

One more step - How to make the self signed certs fully trusted in Chrome/Safari

To allow the self signed certificates to be FULLY trusted in Chrome and Safari, you need to import a new certificate authority into your Mac. To do so follow these instructions, or the more detailed instructions on this general process on the mitmproxy website:

You can do this one of 2 ways, at the command line, using this command which will prompt you for your password:

$ sudo security add-trusted-cert -d -r trustRoot -k /Library/Keychains/System.keychain rootCA.pem

or by using the Keychain Access app:

1. Open Keychain Access
2. Choose "System" in the "Keychains" list
3. Choose "Certificates" in the "Category" list
4. Choose "File | Import Items..."
5. Browse to the file created above, "rootCA.pem", select it, and click "Open"
6. Select your newly imported certificate in the "Certificates" list.
7. Click the "i" button, or right click on your certificate, and choose "Get Info"
8. Expand the "Trust" option
9. Change "When using this certificate" to "Always Trust"
10. Close the dialog, and you'll be prompted for your password.
11. Close and reopen any tabs that are using your target domain, and it'll be loaded securely!

and as a bonus, if you need java clients to trust the certificates, you can do so by importing your certs into the java keystore. Note this will remove the cert from the keystore if it already exists, as it needs to update it in case things change. It of course only does this for the certs being imported.

import_certs_in_current_folder_into_java_keystore.sh

KEYSTORE="$(/usr/libexec/java_home)/jre/lib/security/cacerts";

function running_as_root()
{
  if [ "$EUID" -ne 0 ]
    then echo "NO"
    exit
  fi

  echo "YES"
}

function import_certs_to_java_keystore
{
  for crt in *.crt; do 
    echo prepping $crt 
    keytool -delete -storepass changeit -alias alias__${crt} -keystore $KEYSTORE;
    keytool -import -file $crt -storepass changeit -noprompt --alias alias__${crt} -keystore $KEYSTORE
    echo 
  done
}

if [ "$(running_as_root)" == "YES" ]
then
  import_certs_to_java_keystore
else
  echo "This script needs to be run as root!"
fi