smime/smime.cnf

[ req ]
default_bits        = 2048
distinguished_name  = req_distinguished_name
string_mask         = utf8only
default_md          = sha256
req_extensions      = smime_req_ext

[ 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

[ smime_req_ext ]
subjectKeyIdentifier = hash
basicConstraints = CA:FALSE
keyUsage = digitalSignature, keyEncipherment
extendedKeyUsage = emailProtection
subjectAltName = email:copy

[ smime_ext ]
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid:always,issuer
basicConstraints = CA:FALSE
keyUsage = critical, digitalSignature, keyEncipherment
extendedKeyUsage = critical, emailProtection
subjectAltName = email:copy