NAME

create-cert — create openssl client key and certificates

SYNOPSIS

create-cert [-nv] [-c config] -I

create-cert [-nv] [-c config] -C cert

create-cert [-nv] [-c config] -R

create-cert [-fnv] [-c config] [-b bits] [-d days] [-D digest] FQDN ...

DESCRIPTION

create-cert is a script that uses openssl(1) to create self-signed host certificates and private keys for fully qualified domain names (FQDNs).

A configuration file to specify certificate attributes. The -I flag is used to create an initial version of this file. The user may optionally customize this file before running create-cert with the -R flag which creates a self-signed rootca cert and key.

Once a valid configuration file, rootca cert, and key files are all present, create-cert can be used to create cert and key files for a FQDN. The FQDN will be added as a Subject Alt Name as will an additional arguments. create-cert requires each FQDN (and any Subject Alt Names) to include at least one ‘.’ in it; use the -f flag to override this restriction. IPv4 and IPv6 addresses may also be specified.

Key files are created without group or world read permissions. The script always refuses to overwrite existing files. If c_rehash is found on the user's PATH, it is used to hash the certs directory after a host cert is created.

OPTIONS

Here are the command line options:

-b bits: Override the size of the key in bits when creating a certificate.
-d days: When creating a new certificate, override the number days to certify it.
-D digest: When creating a new certificate, override the digest.
-c config: Specify the configuration file; defaults to create-cert.conf.
-C cert: Like -I, creates an initial configuration file but populates the values from an existing X509 root or host certificate file cert. This is a handy way to bootstrap an old tree of self-signed certs for use with create-cert.
-f: Normally, create-cert requires FQDNs (with at least one ‘.’ in them). The -f flag removes this restriction.
-I: Create an initial configuration file; see the description for the -c flag for more details about the filename used.
-n: Show the shell commands but do not execute them (aka dry run).
-R: Create a self-signed rootca cert and private key.
-v: Increase verbosity.

CONFIGURATION OPTIONS

Here are the configuration options that may be used in create-cert.conf.

country: The two character country code.
state: The State or province.
city: The City or locality.
organization: The name of the organization or company.
authority: The name of the authority.
rootname: The root certificate authority name.
email: The email address of the organization.
bits: Size of the key in bits. Keys smaller than 2048 are not recommended.
digest: The format of the message digest. Possible values include md2, md5, mdc2, rmd160, sha, sha1, sha224, sha256, sha384 and sha512. sha1 or higher is recommend and in particular md5 is not recommended as iPhones reject certificates using this hash algorithm due to its weakness.
days: The number of days to certify the certificate. The default is 3650 (10 years).

EXAMPLES

Here's an example work flow using create-cert to create a new rootca and host certs and keys (uninteresting output from openssl has been removed):

% create-cert
create-cert: Please use -I or -C to create a config (create-cert.conf)
% create-cert -I
create-cert: Creating a default in create-cert.conf
% vi create-cert.conf
% create-cert -R
create-cert: Creating the key for the new rootca
create-cert: Creating temporary rootca config
create-cert: Creating the cert for the new rootca
create-cert: Creating the database file for the new rootca
create-cert: Creating the serial file for the new rootca
% create-cert foo.example.com
create-cert: Creating the key for foo.example.com
create-cert: Create a cert config for foo.example.com
create-cert: Create a CSR config for foo.example.com
create-cert: Create a CSR for foo.example.com
create-cert: Sign the certificate request for foo.example.com
create-cert: Verify the the csr for foo.example.com
create-cert: Remove junk we don't need
create-cert: Rehashing the cert directory
create-cert: Cert and key for foo.example.com successfully created
% create-cert bar.example.com 203.0.113.1
create-cert: Creating the key for bar.example.com
[...]
create-cert: Cert and key for bar.example.com successfully created
% find . -type f | sort
./certs/bar.example.com.pem
./certs/foo.example.com.pem
./certs/rootca.index
./certs/rootca.index.attr
./certs/rootca.index.attr.old
./certs/rootca.pem
./create-cert.conf
./private/bar.example.com.key
./private/foo.example.com.key
./private/rootca.key
./private/serial
% openssl x509 -text -noout -in certs/bar.example.com | egrep 'Alternative|DNS'
X509v3 Subject Alternative Name:
DNS:bar.example.com, IP Address:203.0.113.1

Here are some examples of the error checking:

% create-cert -I
create-cert: Error: create-cert.conf exists
% create-cert -R
create-cert: Error: private/rootca.key exists
create-cert: Error: certs/rootca.pem exists
% create-cert bar.example.com
create-cert: Error: private/bar.example.com.key exists
create-cert: Error: certs/bar.example.com.pem exists

FILES

create-cert.conf: create-cert configuration file
certs: public certs directory
certs/rootca.index: certificate database file
certs/rootca.pem: rootca public cert file
private: private key directory
private/rootca.key: rootca private key file
private/serial: certificate serial number file

AUTHOR

Craig Leres