OpenSSL Certificate Authority

README.md

Create CA (root and intermediate) and sign certificates

1. Setup the environment variables in the env.sh file

CA_ROOT_PASSPHRASE='SuperStrongROOTPassphrase'
CA_ROOT_EMAIL='contact@example.com'
CA_ROOT_COMMON_NAME="Example"
CA_ROOT_COUNTRY="US"
CA_ROOT_STATE="New York"
CA_ROOT_LOCATION="New York City"
CA_ROOT_ORGANIZATION="Example Inc."
CA_ROOT_ORGANIZATION_UNIT="IT Department"

CA_INTERMEDIATE_PASSPHRASE='SuperStrongINTERMEDIATEPassphrase'
CA_INTERMEDIATE_EMAIL='contact2@example.com'
CA_INTERMEDIATE_COMMON_NAME="Example CA"
CA_INTERMEDIATE_COUNTRY="US"
CA_INTERMEDIATE_STATE="New York"
CA_INTERMEDIATE_LOCATION="New York City"
CA_INTERMEDIATE_ORGANIZATION="Example Inc."
CA_INTERMEDIATE_ORGANIZATION_UNIT="CA IT Department"

CLIENT_PASSPHRASE='SuperStrongCLIENTPassphrase'
CLIENT_EMAIL='contact@clientdomainexample.com'
CLIENT_COMMON_NAME="clientdomainexample.com"
CLIENT_COUNTRY="US"
CLIENT_STATE="New Jersey"
CLIENT_LOCATION="Newark"
CLIENT_ORGANIZATION="OK Complany Inc."
CLIENT_ORGANIZATION_UNIT="Awesome IT Department"
CLIENT_DOMAIN='clientdomainexample.com'

2. Generate a root key and a root certificate

./root.sh

2. Generate an intermediate key and an intermediate certificate (signed by the root)

./intermediate.sh

3. Generate a client key and a certificate signing request

./client.sh

4. Sign the certificate signing request (with the intermediate key)

./sign.sh

References

• OpenSSL Certificate Authority

client.sh

#!/bin/bash
set -e

# Load the environment variables
source "env.sh"

# Prepare the directories
mkdir client client/private client/certs

# Set the access permissions
chmod 700 client/private

# Generate the client key
openssl genrsa \
  -aes256 \
  -passout env:CLIENT_PASSPHRASE \
  -out client/private/${CLIENT_DOMAIN}.key.pem \
  2048

# Set the access permissions
chmod 400 client/private/${CLIENT_DOMAIN}.key.pem

# Create a certificate signing request
openssl req \
  -config openssl.intermediate.cnf \
  -passin env:CLIENT_PASSPHRASE \
  -new \
  -sha512 \
  -key client/private/${CLIENT_DOMAIN}.key.pem \
  -out ca/intermediate/csr/${CLIENT_DOMAIN}.csr.pem \
  -subj "/emailAddress=${CLIENT_EMAIL}/CN=${CLIENT_COMMON_NAME}/C=${CLIENT_COUNTRY}/ST=${CLIENT_STATE}/L=${CLIENT_LOCATION}/O=${CLIENT_ORGANIZATION}/OU=${CLIENT_ORGANIZATION_UNIT}"

env.sh

#!/bin/bash
set -e

# Root variables
export CA_ROOT_PASSPHRASE='SuperStrongROOTPassphrase'
export CA_ROOT_EMAIL='contact@example.com'
export CA_ROOT_COMMON_NAME="Example"
export CA_ROOT_COUNTRY="US"
export CA_ROOT_STATE="New York"
export CA_ROOT_LOCATION="New York City"
export CA_ROOT_ORGANIZATION="Example Inc."
export CA_ROOT_ORGANIZATION_UNIT="IT Department"

# Intermediate variables
export CA_INTERMEDIATE_PASSPHRASE='SuperStrongINTERMEDIATEPassphrase'
export CA_INTERMEDIATE_EMAIL='contact2@example.com'
export CA_INTERMEDIATE_COMMON_NAME="Example CA"
export CA_INTERMEDIATE_COUNTRY="US"
export CA_INTERMEDIATE_STATE="New York"
export CA_INTERMEDIATE_LOCATION="New York City"
export CA_INTERMEDIATE_ORGANIZATION="Example Inc."
export CA_INTERMEDIATE_ORGANIZATION_UNIT="CA IT Department"

# Client variables
export CLIENT_PASSPHRASE='SuperStrongCLIENTPassphrase'
export CLIENT_EMAIL='contact@clientdomainexample.com'
export CLIENT_COMMON_NAME="clientdomainexample.com"
export CLIENT_COUNTRY="US"
export CLIENT_STATE="New Jersey"
export CLIENT_LOCATION="Newark"
export CLIENT_ORGANIZATION="OK Complany Inc."
export CLIENT_ORGANIZATION_UNIT="Awesome IT Department"
export CLIENT_DOMAIN='clientdomainexample.com'

intermediate.sh

#!/bin/bash
set -e

# Load the environment variables
source "env.sh"

# Prepare the directories
mkdir ca/intermediate \
  ca/intermediate/certs \
  ca/intermediate/crl \
  ca/intermediate/csr \
  ca/intermediate/newcerts \
  ca/intermediate/private

# Set the access permissions
chmod 700 ca/intermediate/private

# Prepare the file database
touch ca/intermediate/index.txt
echo 1000 > ca/intermediate/serial

# Add a `crlnumber` file to the intermediate CA directory tree
echo 1000 > ca/intermediate/crlnumber

# Generate the intermediate key
openssl genrsa \
  -aes256 \
  -passout env:CA_INTERMEDIATE_PASSPHRASE \
  -out ca/intermediate/private/intermediate.key.pem 4096

# Set the access permissions
chmod 400 ca/intermediate/private/intermediate.key.pem

# Create a certificate signing request
openssl req \
  -config openssl.intermediate.cnf \
  -passin env:CA_INTERMEDIATE_PASSPHRASE \
  -new \
  -sha512 \
  -key ca/intermediate/private/intermediate.key.pem \
  -out ca/intermediate/csr/intermediate.csr.pem \
  -subj "/emailAddress=${CA_INTERMEDIATE_EMAIL}/CN=${CA_INTERMEDIATE_COMMON_NAME}/C=${CA_INTERMEDIATE_COUNTRY}/ST=${CA_INTERMEDIATE_STATE}/L=${CA_INTERMEDIATE_LOCATION}/O=${CA_INTERMEDIATE_ORGANIZATION}/OU=${CA_INTERMEDIATE_ORGANIZATION_UNIT}"

# Create an intermediate certificate
openssl ca \
  -config openssl.cnf \
  -passin env:CA_ROOT_PASSPHRASE \
  -extensions v3_intermediate_ca \
  -days 3650 \
  -notext \
  -batch \
  -md sha512 \
  -in ca/intermediate/csr/intermediate.csr.pem \
  -out ca/intermediate/certs/intermediate.cert.pem

# Set the access permissions
chmod 444 ca/intermediate/certs/intermediate.cert.pem

# Verify it is stored the database
cat ca/root/index.txt

# Verify the intermediate certificate
openssl x509 \
  -noout \
  -text \
  -in ca/intermediate/certs/intermediate.cert.pem

# Verify the intermediate certificate against the root certificate
openssl verify \
  -CAfile ca/root/certs/ca.cert.pem \
  ca/intermediate/certs/intermediate.cert.pem

# Create the CA certificate chain
cat ca/intermediate/certs/intermediate.cert.pem \
  ca/root/certs/ca.cert.pem > ca/intermediate/certs/ca-chain.cert.pem

# Set the access permissions
chmod 444 ca/intermediate/certs/ca-chain.cert.pem

openssl.cnf

# OpenSSL root CA configuration file.

[ ca ]
# `man ca`
default_ca = CA_default

[ CA_default ]
# Directory and file locations.
dir               = ca/root
certs             = $dir/certs
crl_dir           = $dir/crl
new_certs_dir     = $dir/newcerts
database          = $dir/index.txt
serial            = $dir/serial
RANDFILE          = $dir/private/.rand

# The root key and root certificate.
private_key       = $dir/private/ca.key.pem
certificate       = $dir/certs/ca.cert.pem

# For certificate revocation lists.
crlnumber         = $dir/crlnumber
crl               = $dir/crl/ca.crl.pem
crl_extensions    = crl_ext
default_crl_days  = 30

# SHA-1 is deprecated, so use SHA-2 instead.
default_md        = sha512

name_opt          = ca_default
cert_opt          = ca_default
default_days      = 375
preserve          = no
policy            = policy_strict

[ policy_strict ]
# The root CA should only sign intermediate certificates that match.
# See the POLICY FORMAT section of `man ca`.
countryName             = match
stateOrProvinceName     = match
organizationName        = match
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional

[ policy_loose ]
# Allow the intermediate CA to sign a more diverse range of certificates.
# See the POLICY FORMAT section of the `ca` man page.
countryName             = optional
stateOrProvinceName     = optional
localityName            = optional
organizationName        = optional
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional

[ req ]
# Options for the `req` tool (`man req`).
default_bits        = 4096
distinguished_name  = req_distinguished_name
string_mask         = utf8only

# SHA-1 is deprecated, so use SHA-2 instead.
default_md          = sha512

# Extension to add when the -x509 option is used.
x509_extensions     = v3_ca

[ req_distinguished_name ]
# See <https://en.wikipedia.org/wiki/Certificate_signing_request>.
countryName                     = Country Name (2 letter code)
stateOrProvinceName             = State or Province Name
localityName                    = Locality Name
0.organizationName              = Organization Name
organizationalUnitName          = Organizational Unit Name
commonName                      = Common Name
emailAddress                    = Email Address

# Optionally, specify some defaults.
countryName_default             = GB
stateOrProvinceName_default     = England
localityName_default            =
0.organizationName_default      = Alice Ltd
organizationalUnitName_default  =
emailAddress_default            =

[ v3_ca ]
# Extensions for a typical CA (`man x509v3_config`).
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid:always,issuer
basicConstraints = critical, CA:true
keyUsage = critical, digitalSignature, cRLSign, keyCertSign

[ v3_intermediate_ca ]
# Extensions for a typical intermediate CA (`man x509v3_config`).
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid:always,issuer
basicConstraints = critical, CA:true, pathlen:0
keyUsage = critical, digitalSignature, cRLSign, keyCertSign

[ usr_cert ]
# Extensions for client certificates (`man x509v3_config`).
basicConstraints = CA:FALSE
nsCertType = client, email
nsComment = "OpenSSL Generated Client Certificate"
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid,issuer
keyUsage = critical, nonRepudiation, digitalSignature, keyEncipherment
extendedKeyUsage = clientAuth, emailProtection

[ server_cert ]
# Extensions for server certificates (`man x509v3_config`).
basicConstraints = CA:FALSE
nsCertType = server
nsComment = "OpenSSL Generated Server Certificate"
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid,issuer:always
keyUsage = critical, digitalSignature, keyEncipherment
extendedKeyUsage = serverAuth

[ crl_ext ]
# Extension for CRLs (`man x509v3_config`).
authorityKeyIdentifier=keyid:always

[ ocsp ]
# Extension for OCSP signing certificates (`man ocsp`).
basicConstraints = CA:FALSE
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid,issuer
keyUsage = critical, digitalSignature
extendedKeyUsage = critical, OCSPSigning

openssl.intermediate.cnf

# OpenSSL intermediate CA configuration file.

[ ca ]
# `man ca`
default_ca = CA_default

[ CA_default ]
# Directory and file locations.
dir               = ca/intermediate
certs             = $dir/certs
crl_dir           = $dir/crl
new_certs_dir     = $dir/newcerts
database          = $dir/index.txt
serial            = $dir/serial
RANDFILE          = $dir/private/.rand

# The root key and root certificate.
private_key       = $dir/private/intermediate.key.pem
certificate       = $dir/certs/intermediate.cert.pem

# For certificate revocation lists.
crlnumber         = $dir/crlnumber
crl               = $dir/crl/intermediate.crl.pem
crl_extensions    = crl_ext
default_crl_days  = 30

# SHA-1 is deprecated, so use SHA-2 instead.
default_md        = sha512

name_opt          = ca_default
cert_opt          = ca_default
default_days      = 375
preserve          = no
policy            = policy_loose

[ policy_strict ]
# The root CA should only sign intermediate certificates that match.
# See the POLICY FORMAT section of `man ca`.
countryName             = match
stateOrProvinceName     = match
organizationName        = match
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional

[ policy_loose ]
# Allow the intermediate CA to sign a more diverse range of certificates.
# See the POLICY FORMAT section of the `ca` man page.
countryName             = optional
stateOrProvinceName     = optional
localityName            = optional
organizationName        = optional
organizationalUnitName  = optional
commonName              = supplied
emailAddress            = optional

[ req ]
# Options for the `req` tool (`man req`).
default_bits        = 4096
distinguished_name  = req_distinguished_name
string_mask         = utf8only

# SHA-1 is deprecated, so use SHA-2 instead.
default_md          = sha512

# Extension to add when the -x509 option is used.
x509_extensions     = v3_ca

[ req_distinguished_name ]
# See <https://en.wikipedia.org/wiki/Certificate_signing_request>.
countryName                     = Country Name (2 letter code)
stateOrProvinceName             = State or Province Name
localityName                    = Locality Name
0.organizationName              = Organization Name
organizationalUnitName          = Organizational Unit Name
commonName                      = Common Name
emailAddress                    = Email Address

# Optionally, specify some defaults.
countryName_default             = GB
stateOrProvinceName_default     = England
localityName_default            =
0.organizationName_default      = Alice Ltd
organizationalUnitName_default  =
emailAddress_default            =

[ v3_ca ]
# Extensions for a typical CA (`man x509v3_config`).
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid:always,issuer
basicConstraints = critical, CA:true
keyUsage = critical, digitalSignature, cRLSign, keyCertSign

[ v3_intermediate_ca ]
# Extensions for a typical intermediate CA (`man x509v3_config`).
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid:always,issuer
basicConstraints = critical, CA:true, pathlen:0
keyUsage = critical, digitalSignature, cRLSign, keyCertSign

[ usr_cert ]
# Extensions for client certificates (`man x509v3_config`).
basicConstraints = CA:FALSE
nsCertType = client, email
nsComment = "OpenSSL Generated Client Certificate"
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid,issuer
keyUsage = critical, nonRepudiation, digitalSignature, keyEncipherment
extendedKeyUsage = clientAuth, emailProtection

[ server_cert ]
# Extensions for server certificates (`man x509v3_config`).
basicConstraints = CA:FALSE
nsCertType = server
nsComment = "OpenSSL Generated Server Certificate"
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid,issuer:always
keyUsage = critical, digitalSignature, keyEncipherment
extendedKeyUsage = serverAuth

[ crl_ext ]
# Extension for CRLs (`man x509v3_config`).
authorityKeyIdentifier=keyid:always

[ ocsp ]
# Extension for OCSP signing certificates (`man ocsp`).
basicConstraints = CA:FALSE
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid,issuer
keyUsage = critical, digitalSignature
extendedKeyUsage = critical, OCSPSigning

root.sh

#!/bin/bash
set -e

# Load the environment variables
source "env.sh"

# Prepare the directories
mkdir ca ca/root ca/root/certs ca/root/crl ca/root/newcerts ca/root/private

# Set the access permissions
chmod 700 ca/root/private

# Prepare the file database
touch ca/root/index.txt
echo 1000 > ca/root/serial

# Generate the root key
openssl genrsa \
  -aes256 \
  -passout env:CA_ROOT_PASSPHRASE \
  -out ca/root/private/ca.key.pem 4096

# Set the access permissions
chmod 400 ca/root/private/ca.key.pem

# Create the root certificate
openssl req \
  -config openssl.cnf \
  -key ca/root/private/ca.key.pem \
  -passin env:CA_ROOT_PASSPHRASE \
  -new \
  -x509 \
  -days 7300 \
  -sha512 \
  -extensions v3_ca \
  -out ca/root/certs/ca.cert.pem \
  -subj "/emailAddress=${CA_ROOT_EMAIL}/CN=${CA_ROOT_COMMON_NAME}/C=${CA_ROOT_COUNTRY}/ST=${CA_ROOT_STATE}/L=${CA_ROOT_LOCATION}/O=${CA_ROOT_ORGANIZATION}/OU=${CA_ROOT_ORGANIZATION_UNIT}"

# Set the access permissions
chmod 444 ca/root/certs/ca.cert.pem

# Verify the root certificate
openssl x509 -noout -text -in ca/root/certs/ca.cert.pem

sign.sh

#!/bin/bash
set -e

# Load the environment variables
source "env.sh"

# Create a client certificate
openssl ca \
  -config openssl.intermediate.cnf \
  -passin env:CA_INTERMEDIATE_PASSPHRASE \
  -extensions server_cert \
  -days 90 \
  -notext \
  -batch \
  -md sha512 \
  -in ca/intermediate/csr/${CLIENT_DOMAIN}.csr.pem \
  -out client/certs/${CLIENT_DOMAIN}.cert.pem

# Verify it is stored the database
cat ca/intermediate/index.txt

# Verify the client certificate
openssl x509 \
  -noout \
  -text \
  -in client/certs/${CLIENT_DOMAIN}.cert.pem

# Verify the intermediate certificate against the root certificate
openssl verify \
  -CAfile ca/intermediate/certs/ca-chain.cert.pem \
  client/certs/${CLIENT_DOMAIN}.cert.pem