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Use openssl to create an x509 self-signed certificate authority (CA), certificate signing request (CSR), and resulting private key with IP SAN and DNS SAN
# Define where to store the generated certs and metadata.
# Optional: Ensure the target directory exists and is empty.
rm -rf "${DIR}"
mkdir -p "${DIR}"
# Create the openssl configuration file. This is used for both generating
# the certificate as well as for specifying the extensions. It aims in favor
# of automation, so the DN is encoding and not prompted.
cat > "${DIR}/openssl.cnf" << EOF
default_bits = 2048
encrypt_key = no # Change to encrypt the private key using des3 or similar
default_md = sha256
prompt = no
utf8 = yes
# Speify the DN here so we aren't prompted (along with prompt = no above).
distinguished_name = req_distinguished_name
# Extensions for SAN IP and SAN DNS
req_extensions = v3_req
# Be sure to update the subject to match your organization.
C = US
ST = California
L = The Cloud
O = Demo
CN = My Certificate
# Allow client and server auth. You may want to only allow server auth.
# Link to SAN names.
basicConstraints = CA:FALSE
subjectKeyIdentifier = hash
keyUsage = digitalSignature, keyEncipherment
extendedKeyUsage = clientAuth, serverAuth
subjectAltName = @alt_names
# Alternative names are specified as IP.# and DNS.# for IP addresses and
# DNS accordingly.
IP.1 =
DNS.1 =
# Create the certificate authority (CA). This will be a self-signed CA, and this
# command generates both the private key and the certificate. You may want to
# adjust the number of bits (4096 is a bit more secure, but not supported in all
# places at the time of this publication).
# To put a password on the key, remove the -nodes option.
# Be sure to update the subject to match your organization.
openssl req \
-new \
-newkey rsa:2048 \
-days 120 \
-nodes \
-x509 \
-subj "/C=US/ST=California/L=The Cloud/O=My Company CA" \
-keyout "${DIR}/ca.key" \
-out "${DIR}/ca.crt"
# For each server/service you want to secure with your CA, repeat the
# following steps:
# Generate the private key for the service. Again, you may want to increase
# the bits to 4096.
openssl genrsa -out "${DIR}/my-service.key" 2048
# Generate a CSR using the configuration and the key just generated. We will
# give this CSR to our CA to sign.
openssl req \
-new -key "${DIR}/my-service.key" \
-out "${DIR}/my-service.csr" \
-config "${DIR}/openssl.cnf"
# Sign the CSR with our CA. This will generate a new certificate that is signed
# by our CA.
openssl x509 \
-req \
-days 120 \
-in "${DIR}/my-service.csr" \
-CA "${DIR}/ca.crt" \
-CAkey "${DIR}/ca.key" \
-CAcreateserial \
-extensions v3_req \
-extfile "${DIR}/openssl.cnf" \
-out "${DIR}/my-service.crt"
# (Optional) Verify the certificate.
openssl x509 -in "${DIR}/my-service.crt" -noout -text
# Here is a sample response (truncate):
# Certificate:
# Signature Algorithm: sha256WithRSAEncryption
# Issuer: C = US, ST = California, L = The Cloud, O = My Organization CA
# Subject: C = US, ST = California, L = The Cloud, O = Demo, CN = My Certificate
# # ...
# X509v3 extensions:
# X509v3 Basic Constraints:
# X509v3 Subject Key Identifier:
# 36:7E:F0:3D:93:C6:ED:02:22:A9:3D:FF:18:B6:63:5F:20:52:6E:2E
# X509v3 Key Usage:
# Digital Signature, Key Encipherment
# X509v3 Extended Key Usage:
# TLS Web Client Authentication, TLS Web Server Authentication
# X509v3 Subject Alternative Name:
# IP Address:,
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