Pour cela, on va se rendre dans un dossier isolé :

# mkdir /root/ca && cd /root/ca
</bash>
 
puis on va créer l'organisation de dossier suivante:
 
<code bash>
# mkdir certs crl newcerts private csr
# chmod 700 private

Et on créer les fichiers de contrôle :

# touch index.txt
# echo 1000 > serial

puis on créer le fichier :

openssf.cfg

[ ca ]
# `man ca`
default_ca = CA_default
 
[ CA_default ]
# Directory and file locations.
dir               = /root/ca
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        = sha256
 
name_opt          = ca_default
cert_opt          = ca_default
default_days      = 375
preserve          = no
policy            = policy_loose
 
[ 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          = sha256
 
# Extension to add when the -x509 option is used.
x509_extensions     = v3_ca
 
 
 
[ req_distinguished_name ]
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
 
countryName_default             = FR
stateOrProvinceName_default     = Deux-Sèvres
localityName_default            = Niort
0.organizationName_default      = VirtIT
#organizationalUnitName_default =
emailAddress_default           = contact@virtit.fr
 
[ 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
 
[ 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

On génére ensuite la clé privé du CA root :

# openssl genrsa -out private/ca.key.pem 4096

et puis le certificat :

# openssl req -config openssl.cnf \
      -key private/ca.key.pem \
      -new -x509 -days 7300 -sha256 -extensions v3_ca \
      -out certs/ca.cert.pem

On créer ensuite la clé privée du certificat :

# openssl genrsa -out private/server.key.pem 4096

puis le CSR :

# openssl req -key private/server.key.pem -new -out csr/server.csr.pem

Et puis on le signe :

# openssl ca -config openssl.cnf -extensions server_cert -days 375 -notext -in csr/server.csr.pem -out certs/server.cert.pem