cherrypy ssl self certificate

CherryPY SSL Self Certificate

CherryPy can encrypt connections using SSL to create an https connection. This keeps your web traffic secure. Here’s how.

Generate a Private Key

Generate a private key. We’ll use openssl and follow the OpenSSL Keys HOWTO.:

$ openssl genrsa -out privkey.pem 2048

You can create either a key that requires a password to use, or one without a password. Protecting your private key with a password is much more secure, but requires that you enter the password every time you use the key. For example, you may have to enter the password when you start or restart your CherryPy server. This may or may not be feasible, depending on your setup.

If you want to require a password, add one of the -aes128, -aes192 or -aes256 switches to the command above. You should not use any of the DES, 3DES, or SEED algorithms to protect your password, as they are insecure.

SSL Labs recommends using 2048-bit RSA keys for security (see references section at the end).

Generate a certificate. We’ll use openssl and follow the OpenSSL Certificates HOWTO. Let’s start off with a self-signed certificate for testing:

Generate Certificate

$ openssl req -new -x509 -days 365 -key privkey.pem -out cert.pem

openssl will then ask you a series of questions. You can enter whatever values are applicable, or leave most fields blank. The one field you must fill in is the ‘Common Name’: enter the hostname you will use to access your site. If you are just creating a certificate to test on your own machine and you access the server by typing ‘localhost’ into your browser, enter the Common Name ‘localhost’.

Decide whether you want to use python’s built-in SSL library, or the pyOpenSSL library. CherryPy supports either.

Built-in. To use python’s built-in SSL, add the following line to your CherryPy config:

#In the cherrypy config
cherrypy.server.ssl_module = 'builtin'

pyOpenSSL. Because python did not have a built-in SSL library when CherryPy was first created, the default setting is to use pyOpenSSL. To use it you’ll need to install it (we could recommend you install cython first):

$ pip install cython, pyOpenSSL

Add the following lines in your CherryPy config to point to your certificate files:

cherrypy.server.ssl_certificate = "cert.pem"
cherrypy.server.ssl_private_key = "privkey.pem"

If you have a certificate chain at hand, you can also specify it:

cherrypy.server.ssl_certificate_chain = "certchain.perm"

Start your CherryPy server normally. Note that if you are debugging locally and/or using a self-signed certificate, your browser may show you security warnings.

Note: For Curl I add -k which disables the "warning" regarding Unknown certificate.

SSL Self Certified Certificate

Write down the Common Name (CN) for your SSL Certificate. The CN is the fully qualified name for the system that uses the certificate.

If you are using Dynamic DNS, your CN should have a wild-card, for example: * Otherwise, use the hostname or IP address set in your Gateway Cluster (for example. or

Run the following OpenSSL command to generate your private key and public certificate. Answer the questions and enter the Common Name when prompted.

Generate a Private Key

The openssl toolkit is used to generate an RSA Private Key and CSR (Certificate Signing Request). It can also be used to generate self-signed certificates which can be used for testing purposes or internal usage.

The first step is to create your RSA Private Key. This key is a 1024 bit RSA key which is encrypted using Triple-DES and stored in a PEM format so that it is readable as ASCII text.

openssl genrsa -des3 -out server.key 2048

Remember your passkey

Generate a CSR (Certificate Signing Request)

Once the private key is generated a Certificate Signing Request can be generated. The CSR is then used in one of two ways. Ideally, the CSR will be sent to a Certificate Authority, such as Thawte or Verisign who will verify the identity of the requestor and issue a signed certificate. The second option is to self-sign the CSR, which will be demonstrated in the next section.

During the generation of the CSR, you will be prompted for several pieces of information. These are the X.509 attributes of the certificate. One of the prompts will be for "Common Name (e.g., YOUR name)". It is important that this field be filled in with the fully qualified domain name of the server to be protected by SSL. If the website to be protected will be, then enter at this prompt. The command to generate the CSR is as follows:

openssl req -new -key server.key -out server.csr

You will be prompted for data like this

Country Name (2 letter code) [GB]:CH
State or Province Name (full name) [Berkshire]:Bern
Locality Name (eg, city) [Newbury]:Oberdiessbach
Organization Name (eg, company) [My Company Ltd]:Akadia AG
Organizational Unit Name (eg, section) []:Information Technology
Common Name (eg, your name or your server's hostname) []
Email Address []:martin dot zahn at akadia dot ch
Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

Remove Passphrase from Key

One unfortunate side-effect of the pass-phrased private key is that Apache will ask for the pass-phrase each time the web server is started. Obviously this is not necessarily convenient as someone will not always be around to type in the pass-phrase, such as after a reboot or crash. mod_ssl includes the ability to use an external program in place of the built-in pass-phrase dialog, however, this is not necessarily the most secure option either. It is possible to remove the Triple-DES encryption from the key, thereby no longer needing to type in a pass-phrase. If the private key is no longer encrypted, it is critical that this file only be readable by the root user! If your system is ever compromised and a third party obtains your unencrypted private key, the corresponding certificate will need to be revoked.

With that being said, use the following command to remove the pass-phrase from the key

cp server.key
openssl rsa -in -out server.key

The newly created server.key file has no more passphrase in it.

-rw-r--r-- 1 root root 745 Jun 29 12:19 server.csr
-rw-r--r-- 1 root root 891 Jun 29 13:22 server.key
-rw-r--r-- 1 root root 963 Jun 29 13:22

Generating a Self-Signed Certificate

At this point you will need to generate a self-signed certificate because you either don't plan on having your certificate signed by a CA, or you wish to test your new SSL implementation while the CA is signing your certificate. This temporary certificate will generate an error in the client browser to the effect that the signing certificate authority is unknown and not trusted.

To generate a temporary certificate which is good for 365 days, issue the following command:

openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt

I see the output like

Signature ok
Getting Private key

Installing the Private Key and Certificate

When Apache with mod_ssl is installed, it creates several directories in the Apache config directory. The location of this directory will differ depending on how Apache was compiled.

cp server.crt /usr/local/apache/conf/ssl.crt
cp server.key /usr/local/apache/conf/ssl.key