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caman

A self-signing certificate authority manager - create your own certificate authority, and generate and manage SSL certificates using openssl.

If you want to see how caman works and why it exists, you read the accompanying article, Self-Signing Certificate Authorities

This document explains how to use caman to create a certificate authority, optionally use an intermediate CA, and to create, sign, renew and revoke host certificates.

Version 0.3.2, 2016-11-24. For changelog and upgrade information, see Changes

Quickstart

To create a certificate authority and start signing:

git clone https://github.com/radiac/caman.git
cd caman
cp ca/caconfig.cnf.default ca/caconfig.cnf && vi ca/caconfig.cnf
cp ca/host.cnf.default ca/host.cnf && vi ca/host.cnf
./caman init
./caman new host.example.com
./caman sign host.example.com
./caman renew host.example.com
./caman revoke host.example.com

Read on to see more details, how you can do this using an intermediate certificate authority, and how to create wildcard and SAN certificates.

Creating a Certificate Authority

  1. Make sure openssl is installed on your system before using caman:

    • Debian and Ubuntu: sudo apt-get install openssl

  2. Clone this repository:

     git clone https://github.com/radiac/caman.git

    The .gitignore is set up to ignore all files caman will create. This is to prevent you from accidentally pushing secrets to a public repository.

    Although these instructions assume you'll keep everything in the cloned directory, the caman script operates on the current working directory and just expects it to contain the ca directory.

    This means you can move/symlink the script to /usr/local/bin/ to make it available system-wide, or move the ca directory into a separate folder or repository.

  3. Configure the files in the ca directory - (see Configuration)

  4. Initialise caman in the current directory:

     cd caman
 ./caman init
    • You will be asked for a PEM key - this must be at least 4 characters long, but the longer the better. Keep it safe - you will need it for most caman commands.
    • If you plan to use a intermediate CAs, this will be your root CA.

    You are now ready to create and manage host certificates.

  5. Optional: Create an intermediate CA to do your day-to-day signing, so you can keep your root CA key safe and offline. See Using an intermediate CA for details.

  6. Optional: Publish ca/ca.crl.pem at the URL in your configuration (or you can you disable CRL in your config).

  7. Optional: Distribute ca/ca.crt.pem for your host certificates to be recognised; see Distribution for more information

Keep ca/ca.key.pem private. If it is compromised, you will need to destroy your certificate authority and start again.

Configuration

Copy the default configs:

cp ca/caconfig.cnf.default ca/caconfig.cnf
cp ca/host.cnf.default ca/host.cnf

Edit both files; look for comments starting # >> for where you need to make changes.

Changes to make in ca/caconfig.cnf:

  • Change the 6 values under [ req_distinguished_name ]:
    • countryName: your two-character country code
    • stateOrProvinceName: your state or province
    • organizationName: the name of your organisation
    • organizationUnitName: your department in the organisation
    • commonName: the name of your organisation
    • emailAddress: your e-mail address
  • Change the CRL distribution points URL under [ usr_cert ] and [ v3_ca ]:
    • crlDistributionPoints: URL where you will publish your ca.crl.pem
    • If you don't plan on publishing a CRL, comment these lines out, as well as crl_extensions and crlnumber under [ CA_default ].
  • The lifespan of your CA is default_days - 100 years by default

In ca/host.cnf:

  • Change 5 of the values under [ host_distinguished_name ]:
    • countryName: the two-character country code for this host
    • stateOrProvinceName: the state or province for this host
    • organizationName: the name of the organisation for this host
    • organizationUnitName: your department in the organisation
    • emailAddress: the e-mail address for the admin for this host
    • Do not change commonName - this is a placeholder which will be set by caman
  • The lifespan of your host certs is default_days - 10 years by default

Distribution

You need to distribute your ca/ca.crt.pem to clients for your host certificates to be recognised.

To install your CA cert system-wide in Debian and Ubuntu:

sudo cp ca/ca.crt.pem /usr/local/share/ca-certificates/my_ca_name.crt
sudo dpkg-reconfigure ca-certificates

To install your CA cert system-wide in other Linux distros:

cp ca/ca.crt.pem "/etc/openssl/certs/$( \
    openssl x509 -inform PEM -subject_hash -in ca/ca.crt.pem | head -1 \
).0"

To install your CA cert system-wide in Windows:

  1. For Windows Certificate Manager to recognise your certificate, you will need to remove the .pem file extension and distribute the file as ca.crt.
  2. Open the file from your filer or Internet Explorer like a normal file; Windows Certificate Manager will be used automatically.
  3. Click "Install certificate..." and accept all defaults

Some applications (such as Firefox and Thunderbird) have their own certificate stores; you may need to install your root certificate in these applications separately.

Using an intermediate CA

When running a CA, it is best practice to use an intermediate CA. You will publish your root CA's public certificate as normal, but can store your root CA's private key offline and use your intermediate CA to sign host certificates.

If your intermediate CA's private key is then compromised, you can revoke your current intermediate CA and create a new one, without needing to re-issue your root CA's public certificate.

A paranoid user may want to create and use their root key on a machine which is permanently air-gapped and never connects to a network. If you don't have one of those available, it should be sufficient to move your root CA to removable media, kept offline in a secure location.

Caman supports multiple intermediate CAs from your root CA, and intermediate CAs can be used to create longer chains of intermediate CAs as desired.

Creating an intermediate CA

Creating an intermediate CA is exactly the same as creating a root CA, but you pass the path of your root CA to the init command, and only publish the CRT for your root CA:

  1. Follow the (standard installation)[#creating-a-certificate-authority] to create your root CA, including publishing its CRL and distributing its CRT.

  2. Create a new caman installation for your intermediate CA:

     cd ../
 mv caman caman-root
 git clone https://github.com/radiac/caman.git caman-int
 cd caman-int
    • Your caman directory names don't need to match the ones in this example; they don't even need to be caman installations. The caman script operates on the current working directory, so if you install it system-wide, your root and intermediate CAs can start as folders with nothing but a configured ca directory. Just make sure you're in the right directory when you call caman.

  3. Configure your intermediate CA using the files in caman-int/ca - (see Configuration)

    • Make sure that your commonName is unique - it must be different to your root CA's common name, any other intermediate CAs you create, and it must not match any hosts
    • Make sure that your CRL is at a different URL to that of your other CAs.

  4. Initialise your intermediate CA by passing the caman dir for your root CA as an argument to init:

     ./caman init ca:../caman-root
    • Note that CA paths are always specified with the ca: prefix
    • You now have your root CA in caman-root and your intermediate CA in caman-int
    • Your intermediate CA's chain file is caman-int/ca/ca-chain.crt.pem

    You are now ready to create and manage host certificates using the new intermediate CA.

  5. Optional: Publish caman-int/ca/ca.crl.pem at the URL in your intermediate CA's configuration (or you can you disable CRL in your config).

  6. Optional: Move your your caman-root dir to secure offline storage

Note: you can use a caman intermediate CA to create further intermediate CAs, should you so wish.

Managing host certificates with an intermediate CA

Caman's syntax for managing host certificates is the same whether or not you are using an intermediate CA, but creating a host certificate with an intermediate CA will also create a file called hostname.chained.crt.pem (with corresponding hostname.chained.keycrt.pem), which is a combined certificate containing your host's certificate along with the intermediate CA's trust chain.

Some servers will want you to use these combined certificates (eg nginx's ssl_certificate directive, or Dovecot's ssl_cert setting), whereas others will want you to use the plain host certificate and provide the chain file in caman-int/ca/ca-chain.crt.pem separately (eg Apache's SSLCACertificateFile directive).

Revoking an intermediate CA

Revoke an intermediate CA from your root CA by passing a CA path to revoke; instead of a hostname, use the ca: prefix, and the path to the caman dir for your intermediate CA:

cd caman-root
./caman revoke ca:../caman-int

Your intermediate CA has now been revoked; publish the updated CRL for your root CA, caman-root/ca/ca.crl.pem.

You cannot use caman to renew intermediate CAs; you have to revoke them and start again.

Managing host certificates

Host certificates are found in the store directory. Each host has its own directory with the config and signing request, and each sign operation creates a new directory with today's date. Use the files inside the latest directory.

Add a new host

./caman new <hostname> [<alt> [<alt> ...]]
  • <hostname> is the main hostname for the certificate
  • Use an asterisk subdomain to generate a wildcard certificate
  • Add multiple <alt> hostnames after the main hostname to create a SAN certificate

Examples:

  • Single host: ./caman new myserver.example.com
  • Wildcard: ./caman new *.example.com
  • SAN: ./caman new myserver.example.com virtual1.example.com virtual2.example.com

This command generates a config file for this host in store/hostname/config.cnf, using the defaults you configured in ca/host.cnf. You can edit this file manually to customise it further (for example, to change the organisational unit name from your default).

Create a new certificate

./caman sign <hostname>

This will generate a new private key, CSR, and signed server certificate. For client certificates use following command:

./caman client_sign <hostname>

Revoke a certificate

./caman revoke <hostname>

You will need to re-publish ca/ca.crl.pem after running this command.

Renew a certificate

./caman renew <hostname>

This revokes the existing certificate, and then creates a new one, so is suitable for replacing both expired or compromised host certificates You will need to re-publish ca/ca.crl.pem after running this command. For client certificates use following command:

./caman client_renew <hostname>

Contributing

Contributions are welcome, preferably via pull request.

Thanks to all contributors, who are listed in CHANGES