SSL is cryptographic protocol, which provides secure communications on the Internet for email, web etc.

An SSL certificate is a digital certificate that authenticates the identity of a Web site and encrypts information that is sent to the server using Secure Sockets Layer (SSL) technology. Encryption is the process of scrambling data into an undecipherable format that can only be returned to a readable format with the proper decryption key.

SSL is good if you run ecommerce site or accept payments via CC. It is a good choice to use SSL for user login or registration pages etc.

To purchase a digital certificate, you must first generate and submit a Certificate Signing Request (CSR) to the Certification Authority (CA). The CSR contains your certificate-application information, including your public key. The CSR is generated (using openssl command) with your web server software, which will also create your public/private key pair used for encrypting and decrypting secure transactions.

Requirements

• Lighttpd webserver with SSL support
• Dedicated IP assign to your domain i.e. IP based hosting needed
• SSL certificate from CA
• Domain name – theos.in (for example purpose I am using theos.in domain)

Important files on your server

• /etc/lighttpd/theos.in/ – Directory to store SSL certificate and related files
• /etc/lighttpd/theos.in/theos.in.key – Your private key file. Never ever, give this file to anybody. This is used by Lighttpd to encrypt the server traffic.
• /etc/lighttpd/theos.in/theos.in.csr – You need to cut/copy and paste this file into the CSR field on the SSL certificate-request page/application form. It includes your public key.
• /etc/lighttpd/theos.in/theos.in.pem – This file can contain all of private keys (RSA and DSA), public keys (RSA and DSA) and (x509) certificates. Usually your keys and certificate stored in this file.

Important files issued by CA

Usually a zip file contains following files

• CA_issuing.crt – Your intermediate certificate or chained root certificate file. An intermediate certificate is a subordinate certificate issued by the trusted root specifically to issue end-entity server certificates. The result is a chain that begins at the trusted root CA, through the intermediate certificate, and ending with the Web Server SSL certificate issued to you. The usage of an intermediate certificate thus provides an added level of security as the Certification Authority (CA) does not need to issue certificates directly from its CA root certificate.
• theos.in.crt – Your domain certificate

Lighttpd SSL Tutorial

Following are steps to configure SSL under Lighttpd web server.

Step # 1: Generate a certificate signing request (CSR)

First, generate a certificate-signing request using openssl command for your domain theos.in:
# mkdir -p /etc/lighttpd/ssl/theos.in
# cd /etc/lighttpd/ssl/theos.in


Create a RSA key:
# openssl genrsa -des3 -out theos.in.key 1024

Now create a CSR:
# openssl req -new -key theos.in.key -out theos.in.csr

You will be promoted to enter your domain name and other information. Please note that if you are requesting a wild card certificate, prefix an asterisk (*) symbol i.e. *.theos.in. This will secure all subdomains. If you just use theos.in, it will only secure theos.in domain and note www.theos.in.

Now, you need to submit your theos.in.csr file to CA while ordering your certificate. Next, you need to verify your domain ownership. Once your request is approved, you can download the certificate to use with Lighttpd webserver.

Step # 2: Prepare certificate

Your CA will issue you signed Web Server Certificate. The final step in the certificate request process is the installation of the certificate on your Lighttpd Web server.

Now copy downloaded certificate (theos.in.crt) to /etc/lighttpd/ssl/theos.in
# cp theos.in.crt /etc/lighttpd/ssl/theos.in

Now create your final pem file and setup permission:
# cat theos.in.key theos.in.crt > theos.in.pem
# chmod 0600 theos.in.pem
# chown lighttpd:lighttpd /etc/lighttpd/ssl/theos.in -R

Optional: How do I remove the password from key file?

Lighttpd will prompt for the password while starting at port 443. You can remove the password:
# cp theos.in.key theos.in.key.bak
# cp theos.in.pem theos.in.pem.bak
# openssl rsa -in theos.in.key -out no.pwd.theos.in.key
# cat no.pwd.theos.in.key theos.in.crt > theos.in.pem


Step #3: Make sure Lighttpd support SSL

Use following command to verify that Lighttpd support SSL:
[vivek@cyberciti.biz]$ /usr/sbin/lighttpd -v
lighttpd-1.4.11 (ssl) - a light and fast webserver
Build-Date: Jul 12 2006 13:47:40


Otherwise, follow these instructions to build Lighttpd with SSL support.

Step #4: Configure Lighttpd SSL support for your domain

Now open your lighttpd configuration file
# vi /etc/lighttpd/lighttpd.conf

Add config section:
$SERVER["socket"] == "theos.in:443" {
ssl.engine = "enable"
ssl.pemfile = "/etc/lighttpd/theos.in/theos.in.pem"
ssl.ca-file = "/etc/lighttpd/theos.in/CA_issuing.crt"
server.name = "theos.in"
server.document-root = "/home/lighttpd/theos.in/https"
server.errorlog = "/var/log/lighttpd/theos.in/serror.log"
accesslog.filename = "/var/log/lighttpd/theos.in/saccess.log"
}

Where,

• ssl.engine = “enable” : Enable lighttpd SSL support
• ssl.pemfile = “/etc/lighttpd/theos.in/theos.in.pem” – Your PEM file
• ssl.ca-file = “/etc/lighttpd/theos.in/CA_issuing.crt” – Your intermediate certificate file

Save and close the file. Restart lighttpd webserver (please note that it will prompt you for SSL private key password):
# /etc/init.d/lighttpd restart

Output:

Password:

Open a web browser and type url https://yourdomain.com (https://theos.in) to test SSL installation.

Further readings:

• How can I tell if a web page is secure?
• How SSL works – This described it as a sequence diagram (PDF file)
• Applied Cryptography book (2 ed) by Bruce Schneier – An excellent book if you want to understand cryptography