How to create a maintainable set of self-signed SSL certificates on a Mac

Last Update On: Nov 4, 2024

There are numerous articles out there on creating a self-signed certificate with OpenSSL, but they often fall short in some key points.

First, the self-signed certificates generated by common methods are usually not secure enough for modern browsers, they need to include the v3 extension. Second, since certificates may need to be updated periodically, it's crucial to maintain a well-organized configuration.

As a real developer, managing self-signed certificates is a systematic process. This article will guide you on how to do it properly on a Mac.

The base idea is to create a certificate that acts as a Root CA. Once we have this root certificate, we can use it to sign any other Certificate Signing Requests (CSRs). After configuring Keychain Access to trust the root certificate, any subsequent certificates signed by it will automatically be trusted by the browser.

Git Repo

Before we begin, it's important to note that several files will be involved in the signing process. To keep everything organized, it's best to use Git. So first, let's initialize a Git repository:

mkdir my_ca && cd my_ca
git init

Config File

Now let’s create a configuration file for OpenSSL, this is an example:

For self-explanation, the comments generated by OpenSSL have been retained, making this file a little bit longer. You can just ignore them, or you might find them informative.

#
# OpenSSL example configuration file.
# See doc/man5/config.pod for more info.
#
# This is mostly being used for generation of certificate requests,
# but may be used for auto loading of providers

# Note that you can include other files from the main configuration
# file using the .include directive.
#.include filename

# This definition stops the following lines choking if HOME isn't
# defined.
HOME			= .

 # Use this in order to automatically load providers.
openssl_conf = openssl_init

# Comment out the next line to ignore configuration errors
config_diagnostics = 1

# Extra OBJECT IDENTIFIER info:
# oid_file       = $ENV::HOME/.oid
oid_section = new_oids

# To use this configuration file with the "-extfile" option of the
# "openssl x509" utility, name here the section containing the
# X.509v3 extensions to use:
# extensions		=
# (Alternatively, use a configuration file that has only
# X.509v3 extensions in its main [= default] section.)

[ new_oids ]
# We can add new OIDs in here for use by 'ca', 'req' and 'ts'.
# Add a simple OID like this:
# testoid1=1.2.3.4
# Or use config file substitution like this:
# testoid2=${testoid1}.5.6

# Policies used by the TSA examples.
tsa_policy1 = 1.2.3.4.1
tsa_policy2 = 1.2.3.4.5.6
tsa_policy3 = 1.2.3.4.5.7

# For FIPS
# Optionally include a file that is generated by the OpenSSL fipsinstall
# application. This file contains configuration data required by the OpenSSL
# fips provider. It contains a named section e.g. [fips_sect] which is
# referenced from the [provider_sect] below.
# Refer to the OpenSSL security policy for more information.
# .include fipsmodule.cnf

[openssl_init]
providers = provider_sect

# List of providers to load
[provider_sect]
default = default_sect
# The fips section name should match the section name inside the
# included fipsmodule.cnf.
# fips = fips_sect

# If no providers are activated explicitly, the default one is activated implicitly.
# See man 7 OSSL_PROVIDER-default for more details.
#
# If you add a section explicitly activating any other provider(s), you most
# probably need to explicitly activate the default provider, otherwise it
# becomes unavailable in openssl.  As a consequence applications depending on
# OpenSSL may not work correctly which could lead to significant system
# problems including inability to remotely access the system.
[default_sect]
# activate = 1


####################################################################
[ ca ]
default_ca	= CA_default		# The default ca section

####################################################################
[ CA_default ]

dir		= /Users/back2wild/work/ssl/my_ca/store		# Where everything is kept
certs		= $dir/certs		# Where the issued certs are kept
crl_dir		= $dir/crl		# Where the issued crl are kept
database	= $dir/index.txt	# database index file.
#unique_subject	= no			# Set to 'no' to allow creation of
					# several certs with same subject.
new_certs_dir	= $dir/newcerts		# default place for new certs.

certificate	= $dir/cacert.pem 	# The CA certificate
serial		= $dir/serial 		# The current serial number
crlnumber	= $dir/crlnumber	# the current crl number
					# must be commented out to leave a V1 CRL
crl		= $dir/crl.pem 		# The current CRL
private_key	= $dir/private/cakey.pem# The private key

x509_extensions	= usr_cert		# The extensions to add to the cert

# Comment out the following two lines for the "traditional"
# (and highly broken) format.
name_opt 	= ca_default		# Subject Name options
cert_opt 	= ca_default		# Certificate field options

# Extension copying option: use with caution.
# copy_extensions = copy

# Extensions to add to a CRL. Note: Netscape communicator chokes on V2 CRLs
# so this is commented out by default to leave a V1 CRL.
# crlnumber must also be commented out to leave a V1 CRL.
# crl_extensions	= crl_ext

default_days	= 365			# how long to certify for
default_crl_days= 30			# how long before next CRL
default_md	= default		# use public key default MD
preserve	= no			# keep passed DN ordering

# A few difference way of specifying how similar the request should look
# For type CA, the listed attributes must be the same, and the optional
# and supplied fields are just that :-)
# by zy: # policy		= policy_match
policy		= policy_anything

# For the CA policy
[ policy_match ]
countryName		= match
stateOrProvinceName	= match
organizationName	= match
organizationalUnitName	= optional
commonName		= supplied
emailAddress		= optional

# For the 'anything' policy
# At this point in time, you must list all acceptable 'object'
# types.
[ policy_anything ]
countryName		= optional
stateOrProvinceName	= optional
localityName		= optional
organizationName	= optional
organizationalUnitName	= optional
commonName		= supplied
emailAddress		= optional

####################################################################
[ req ]
default_bits		= 2048
default_keyfile 	= privkey.pem
distinguished_name	= req_distinguished_name
attributes		= req_attributes
x509_extensions	= v3_ca	# The extensions to add to the self signed cert

# Passwords for private keys if not present they will be prompted for
# input_password = secret
# output_password = secret

# This sets a mask for permitted string types. There are several options.
# default: PrintableString, T61String, BMPString.
# pkix	 : PrintableString, BMPString (PKIX recommendation before 2004)
# utf8only: only UTF8Strings (PKIX recommendation after 2004).
# nombstr : PrintableString, T61String (no BMPStrings or UTF8Strings).
# MASK:XXXX a literal mask value.
# WARNING: ancient versions of Netscape crash on BMPStrings or UTF8Strings.
string_mask = utf8only

# req_extensions = v3_req # The extensions to add to a certificate request

[ req_distinguished_name ]
countryName			= Country Name (2 letter code)
countryName_default		= AU
countryName_min			= 2
countryName_max			= 2

stateOrProvinceName		= State or Province Name (full name)
stateOrProvinceName_default	= Some-State

localityName			= Locality Name (eg, city)

0.organizationName		= Organization Name (eg, company)
0.organizationName_default	= Internet Widgits Pty Ltd

# we can do this but it is not needed normally :-)
#1.organizationName		= Second Organization Name (eg, company)
#1.organizationName_default	= World Wide Web Pty Ltd

organizationalUnitName		= Organizational Unit Name (eg, section)
#organizationalUnitName_default	=

commonName			= Common Name (e.g. server FQDN or YOUR name)
commonName_max			= 64

emailAddress			= Email Address
emailAddress_max		= 64

# SET-ex3			= SET extension number 3

[ req_attributes ]
challengePassword		= A challenge password
challengePassword_min		= 4
challengePassword_max		= 20

unstructuredName		= An optional company name

[ usr_cert ]

# These extensions are added when 'ca' signs a request.

# This goes against PKIX guidelines but some CAs do it and some software
# requires this to avoid interpreting an end user certificate as a CA.

basicConstraints=CA:FALSE

# This is typical in keyUsage for a client certificate.
# keyUsage = nonRepudiation, digitalSignature, keyEncipherment

# PKIX recommendations harmless if included in all certificates.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid,issuer

# This stuff is for subjectAltName and issuerAltname.
# Import the email address.
# subjectAltName=email:copy
# An alternative to produce certificates that aren't
# deprecated according to PKIX.
# subjectAltName=email:move

# Copy subject details
# issuerAltName=issuer:copy

# This is required for TSA certificates.
# extendedKeyUsage = critical,timeStamping

[ v3_req ]

# Extensions to add to a certificate request

basicConstraints = CA:FALSE
keyUsage = nonRepudiation, digitalSignature, keyEncipherment

subjectAltName	=	@alt_names

[alt_names]
DNS.1 = *.back2wild.com
DNS.2 = *.google.com

[ v3_ca ]


# Extensions for a typical CA


# PKIX recommendation.

subjectKeyIdentifier=hash

authorityKeyIdentifier=keyid:always,issuer

basicConstraints = critical,CA:true

# Key usage: this is typical for a CA certificate. However since it will
# prevent it being used as an test self-signed certificate it is best
# left out by default.
# keyUsage = cRLSign, keyCertSign

# Include email address in subject alt name: another PKIX recommendation
# subjectAltName=email:copy
# Copy issuer details
# issuerAltName=issuer:copy

# DER hex encoding of an extension: beware experts only!
# obj=DER:02:03
# Where 'obj' is a standard or added object
# You can even override a supported extension:
# basicConstraints= critical, DER:30:03:01:01:FF

[ crl_ext ]

# CRL extensions.
# Only issuerAltName and authorityKeyIdentifier make any sense in a CRL.

# issuerAltName=issuer:copy
authorityKeyIdentifier=keyid:always

[ proxy_cert_ext ]
# These extensions should be added when creating a proxy certificate

# This goes against PKIX guidelines but some CAs do it and some software
# requires this to avoid interpreting an end user certificate as a CA.

basicConstraints=CA:FALSE

# This is typical in keyUsage for a client certificate.
# keyUsage = nonRepudiation, digitalSignature, keyEncipherment

# PKIX recommendations harmless if included in all certificates.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid,issuer

# This stuff is for subjectAltName and issuerAltname.
# Import the email address.
# subjectAltName=email:copy
# An alternative to produce certificates that aren't
# deprecated according to PKIX.
# subjectAltName=email:move

# Copy subject details
# issuerAltName=issuer:copy

# This really needs to be in place for it to be a proxy certificate.
proxyCertInfo=critical,language:id-ppl-anyLanguage,pathlen:3,policy:foo

####################################################################
[ tsa ]

default_tsa = tsa_config1	# the default TSA section

[ tsa_config1 ]

# These are used by the TSA reply generation only.
dir		= ./demoCA		# TSA root directory
serial		= $dir/tsaserial	# The current serial number (mandatory)
crypto_device	= builtin		# OpenSSL engine to use for signing
signer_cert	= $dir/tsacert.pem 	# The TSA signing certificate
					# (optional)
certs		= $dir/cacert.pem	# Certificate chain to include in reply
					# (optional)
signer_key	= $dir/private/tsakey.pem # The TSA private key (optional)
signer_digest  = sha256			# Signing digest to use. (Optional)
default_policy	= tsa_policy1		# Policy if request did not specify it
					# (optional)
other_policies	= tsa_policy2, tsa_policy3	# acceptable policies (optional)
digests     = sha1, sha256, sha384, sha512  # Acceptable message digests (mandatory)
accuracy	= secs:1, millisecs:500, microsecs:100	# (optional)
clock_precision_digits  = 0	# number of digits after dot. (optional)
ordering		= yes	# Is ordering defined for timestamps?
				# (optional, default: no)
tsa_name		= yes	# Must the TSA name be included in the reply?
				# (optional, default: no)
ess_cert_id_chain	= no	# Must the ESS cert id chain be included?
				# (optional, default: no)
ess_cert_id_alg		= sha1	# algorithm to compute certificate
				# identifier (optional, default: sha1)

[insta] # CMP using Insta Demo CA
# Message transfer
server = pki.certificate.fi:8700
# proxy = # set this as far as needed, e.g., http://192.168.1.1:8080
# tls_use = 0
path = pkix/

# Server authentication
recipient = "/C=FI/O=Insta Demo/CN=Insta Demo CA" # or set srvcert or issuer
ignore_keyusage = 1 # potentially needed quirk
unprotected_errors = 1 # potentially needed quirk
extracertsout = insta.extracerts.pem

# Client authentication
ref = 3078 # user identification
secret = pass:insta # can be used for both client and server side

# Generic message options
cmd = ir # default operation, can be overridden on cmd line with, e.g., kur

# Certificate enrollment
subject = "/CN=openssl-cmp-test"
newkey = insta.priv.pem
out_trusted = insta.ca.crt
certout = insta.cert.pem

[pbm] # Password-based protection for Insta CA
# Server and client authentication
ref = $insta::ref # 3078
secret = $insta::secret # pass:insta

[signature] # Signature-based protection for Insta CA
# Server authentication
trusted = insta.ca.crt # does not include keyUsage digitalSignature

# Client authentication
secret = # disable PBM
key = $insta::newkey # insta.priv.pem
cert = $insta::certout # insta.cert.pem

[ir]
cmd = ir

[cr]
cmd = cr

[kur]
# Certificate update
cmd = kur
oldcert = $insta::certout # insta.cert.pem

[rr]
# Certificate revocation
cmd = rr
oldcert = $insta::certout # insta.cert.pem

Note that the [ v3_req ] section, which is required for a modern SSL cert.

You can change the alt_names, add your custom domains.

Generate Root CA Cert

Let's create a shell file to create root CA:

#!/bin/zsh

set -e
export PATH=/opt/homebrew/Cellar/openssl@3/3.2.0_1/bin/:$PATH

# generate private key for root CA cert:
openssl genrsa -out store/private/cakey.key 2048

# generate the cert:
openssl req -new -x509 -days 3650 \
-key store/private/cakey.key -sha256 \
-out store/cacert.crt \
-config /Users/back2wild/work/ssl/my_ca/_openssl.cnf

Generate Client Files

It's time to generate the client's cert, which can be used for nginx. Also let's create a shell file:

#!/bin/zsh

set -e
export PATH=/opt/homebrew/Cellar/openssl@3/3.2.0_1/bin/:$PATH

# generate client's private key:
openssl genrsa -out store/private/client1.key 2048

# generate CSR:
openssl req -new \
-out store/private/client1.csr \
-key store/private/client1.key \
-config /Users/back2wild/work/ssl/my_ca/_openssl.cnf

Sign the Cert

Also create a shell file:

#!/bin/zsh

set -e
export PATH=/opt/homebrew/Cellar/openssl@3/3.2.0_1/bin/:$PATH

openssl ca -in store/private/client1.csr \
-out store/client1.crt \
-cert store/cacert.crt \
-keyfile store/private/cakey.key \
-extensions v3_req \
-config /Users/back2wild/work/ssl/my_ca/_openssl.cnf

Wrap up

Okay, after creating the shell scripts mentioned above, we can execute them to generate the self-signed cert files.

You'll notice that a store folder will be created. If you encounter any issues, simply clear this folder to start fresh.

In the future, if you need to sign certificates for additional domains, just update the config file and run the corresponding script. Your new certs will be output to the "store" folder.

Everything is well-organized. Isn't it beautiful?

Thanks for reading. Stay Awesome!

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See Also

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  • How to create a maintainable set of self-signed SSL certificates on a Mac
  • FFmpeg Cookbook: frequently used ffmpeg commands and parameters
  • The complete guide to set up a Docker proxy

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