How to Install a SSL for FREE on your Amazon EC2 Hosted Domain

To see these instructions on Amazon’s Support page CLICK HERE

Tutorial: Configure Apache Web Server on Amazon Linux to Use SSL/TLS

Secure Sockets Layer/Transport Layer Security (SSL/TLS) creates an encrypted channel between a web server and web client that protects data in transit from being eavesdropped on. This tutorial explains how to add support manually for SSL/TLS on a single instance of Amazon Linux running Apache web server. The AWS Certificate Manager, not discussed here, is a good option if you plan to offer commercial-grade services.

Prerequisites

Before you begin this tutorial, complete the following steps:

Step 1: Enable SSL/TLS on the Server

This procedure takes you through the process of setting up SSL/TLS on Amazon Linux with a self-signed digital certificate.

To enable SSL/TLS on a server

1. Connect to your instance and confirm that Apache is running.

   [ec2-user ~]$ sudo service httpd status

   If necessary, start Apache.

   [ec2-user ~]$ sudo service httpd start

2. To ensure that all of your software packages are up to date, perform a quick software update on your instance. This process may take a few minutes, but it is important to make sure you have the latest security updates and bug fixes.

   Note

   The -y option installs the updates without asking for confirmation. If you would like to examine the updates before installing, you can omit this option.

   [ec2-user ~]$ sudo yum update -y

3. Now that your instance is current, add SSL/TLS support by installing the Apache module mod_ssl:

   [ec2-user ~]$ sudo yum install -y mod24_ssl

   Later in this tutorial you will work with three important files that have been installed:

   • /etc/httpd/conf.d/ssl.confThe configuration file for mod_ssl. It contains “directives” telling Apache where to find encryption keys and certificates, the SSL/TLS protocol versions to allow, and the encryption ciphers to accept.
   • /etc/pki/tls/private/localhost.keyAn automatically generated, 2048-bit RSA private key for your Amazon EC2 host. During installation, OpenSSL used this key to generate a self-signed host certificate, and you can also use this key to generate a certificate signing request (CSR) to submit to a certificate authority (CA).
   • /etc/pki/tls/certs/localhost.crtAn automatically generated, self-signed X.509 certificate for your server host. This certificate is useful for testing that Apache is properly set up to use SSL/TLS.

   The .key and .crt files are both in PEM format, which consists of Base64-encoded ASCII characters framed by “BEGIN” and “END” lines, as in this abbreviated example of a certificate:

                           -----BEGIN CERTIFICATE-----
                           MIIEazCCA1OgAwIBAgICWxQwDQYJKoZIhvcNAQELBQAwgbExCzAJBgNVBAYTAi0t
                           MRIwEAYDVQQIDAlTb21lU3RhdGUxETAPBgNVBAcMCFNvbWVDaXR5MRkwFwYDVQQK
                           DBBTb21lT3JnYW5pemF0aW9uMR8wHQYDVQQLDBZTb21lT3JnYW5pemF0aW9uYWxV
                           bml0MRkwFwYDVQQDDBBpcC0xNzItMzEtMjAtMjM2MSQwIgYJKoZIhvcNAQkBFhVy
                           ...
                           z5rRUE/XzxRLBZOoWZpNWTXJkQ3uFYH6s/sBwtHpKKZMzOvDedREjNKAvk4ws6F0
                           WanXWehT6FiSZvB4sTEXXJN2jdw8g+sHGnZ8zCOsclknYhHrCVD2vnBlZJKSZvak
                           3ZazhBxtQSukFMOnWPP2a0DMMFGYUHOd0BQE8sBJxg==
                           -----END CERTIFICATE-----                    

   The file names and extensions are a convenience and have no effect on function; you can call a certificate cert.crt, cert.pem, or any other file name, so long as the related directive in the ssl.conf file uses the same name.

   Note

   When you replace the default SSL/TLS files with your own customized files, be sure that they are in PEM format.

4. Restart Apache.

   [ec2-user ~]$ sudo service httpd restart

   Note

   Make sure the TCP port 443 is accessible on your EC2 instance, as described above.

5. Your Apache web server should now support HTTPS (secure HTTP) over port 443. Test it by typing the IP address or fully qualified domain name of your EC2 instance into a browser URL bar with the prefix https://. Because you are connecting to a site with a self-signed, untrusted host certificate, your browser may display a series of security warnings.Override the warnings and proceed to the site. If the default Apache test page opens, it means that you have successfully configured SSL/TLS on your server. All data passing between the browser and server is now safely encrypted.

   To prevent site visitors from encountering warning screens, you need to obtain a certificate that not only encrypts, but also publicly authenticates you as the owner of the site.

Step 2: Obtain a CA-signed Certificate

This section describes the process of generating a certificate signing request (CSR) from a private key, submitting the CSR to a certificate authority (CA), obtaining a signed host certificate, and configuring Apache to use it.

A self-signed SSL/TLS X.509 host certificate is cryptologically identical to a CA-signed certificate. The difference is social, not mathematical; a CA promises to validate, at a minimum, a domain’s ownership before issuing a certificate to an applicant. Each web browser contains a list of CAs trusted by the browser vendor to do this. An X.509 certificate consists primarily of a public key that corresponds to your private server key, and a signature by the CA that is cryptographically tied to the public key. When a browser connects to a web server over HTTPS, the server presents a certificate for the browser to check against its list of trusted CAs. If the signer is on the list, or accessible through a chain of trust consisting of other trusted signers, the browser negotiates a fast encrypted data channel with the server and loads the page.

Certificates generally cost money because of the labor involved in validating the requests, so it pays to shop around. A list of well-known CAs can be found at dmoztools.net. A few CAs offer basic-level certificates free of charge. The most notable of these is the Let’s Encrypt project, which also supports automation of the certificate creation and renewal process. For more information about using Let’s Encrypt as your CA, see Appendix: Let’s Encrypt with Certbot on Amazon Linux.

Underlying the host certificate is the key. As of 2017, government and industry groups recommend using a minimum key (modulus) size of 2048 bits for RSA keys intended to protect documents through 2030. The default modulus size generated by OpenSSL in Amazon Linux is 2048 bits, which means that the existing auto-generated key is suitable for use in a CA-signed certificate. An alternative procedure is described below for those who desire a customized key, for instance, one with a larger modulus or using a different encryption algorithm.

To obtain a CA-signed certificate

1. Connect to your instance and navigate to /etc/pki/tls/private/. This is the directory where the server’s private key for SSL/TLS is stored. If you prefer to use your existing host key to generate the CSR, skip to Step 3.
2. (Optional) Generate a new private key. Here are some sample key configurations. Any of the resulting keys work with your web server, but they vary in how (and how much) security they implement.
   1. As a starting point, here is the command to create an RSA key resembling the default host key on your instance:

      [ec2-user ~]$ sudo openssl genrsa -out custom.key 2048

      The resulting file, custom.key, is a 2048-bit RSA private key.

   2. To create a stronger RSA key with a bigger modulus, use the following command:

      [ec2-user ~]$ sudo openssl genrsa -out custom.key 4096

      The resulting file, custom.key, is a 4096–bit RSA private key.

   3. To create a 4096-bit encrypted RSA key with password protection, use the following command:

      [ec2-user ~]$ sudo openssl genrsa -aes128 -passout pass:abcde12345 -out custom.key 4096

      This results in a 4096-bit RSA private key that has been encrypted with the AES-128 cipher.

      Important

      Encryption provides greater security, but because an encrypted key requires a password, services depending on it cannot be auto-started. Each time you use this key, you need to supply the password “abcde12345” over an SSH connection.

   4. RSA cryptography can be relatively slow, because its security relies on the difficulty of factoring the product of two large two prime numbers. However, it is possible to create keys for SSL/TLS that use non-RSA ciphers. Keys based on the mathematics of elliptic curves are smaller and computationally faster when delivering an equivalent level of security. Here is an example:

      [ec2-user ~]$ sudo openssl ecparam -name prime256v1 -out custom.key -genkey

      The output in this case is a 256-bit elliptic curve private key using prime256v1, a “named curve” that OpenSSL supports. Its cryptographic strength is slightly greater than a 2048-bit RSA key, according to NIST.

      Note

      Not all CAs provide the same level of support for elliptic-curve-based keys as for RSA keys.

   Make sure that the new private key has highly restrictive ownership and permissions (owner=root, group=root, read/write for owner only). The commands would be as follows:

   [ec2-user ~]$ sudo chown root.root custom.key [ec2-user ~]$ sudo chmod 600 custom.key [ec2-user ~]$ ls -al custom.key

   The commands above should yield the following result:

   -rw------- root root custom.key

   After you have created and configured a satisfactory key, you can create a CSR.

3. Create a CSR using your preferred key; the example below uses custom.key:

   [ec2-user ~]$ sudo openssl req -new -key custom.key -out csr.pem

   OpenSSL opens a dialog and prompts you for information shown in the table below. All of the fields except Common Name are optional for a basic, domain-validated host certificate.

   Name	Description	Example
   Country Name	The two-letter ISO abbreviation for your country.	US (=United States)
   State or Province Name	The name of the state or province where your organization is located. This name cannot be abbreviated.	Washington
   Locality Name	The location of your organization, such as a city.	Seattle
   Organization Name	The full legal name of your organization. Do not abbreviate your organization name.	Example Corporation
   Organizational Unit Name	Additional organizational information, if any.	Example Dept
   Common Name	This value must exactly match the web address that you expect users to type into a browser. Usually, this means a domain name with a prefixed host name or alias in the form www.example.com. In testing with a self-signed certificate and no DNS resolution, the common name may consist of the host name alone. CAs also offer more expensive certificates that accept wild-card names such as *.example.com.	www.example.com
   Email Address	The server administrator’s email address.	someone@example.com

   Finally, OpenSSL prompts you for an optional challenge password. This password applies only to the CSR and to transactions between you and your CA, so follow the CA’s recommendations about this and the other optional field, optional company name. The CSR challenge password has no effect on server operation.

   The resulting file csr.pem contains your public key, your digital signature of your public key, and the metadata that you entered.

4. Submit the CSR to a CA. This usually consists of opening your CSR file in a text editor and copying the contents into a web form. At this time, you may be asked to supply one or more subject alternate names (SANs) to be placed on the certificate. If www.example.com is the common name, then example.com would be a good SAN, and vice versa. A visitor to your site typing in either of these names would see an error-free connection. If your CA web form allows it, include the common name in the list of SANs. Some CAs include it automatically.After your request has been approved, you will receive a new host certificate signed by the CA. You may also be instructed to download an intermediate certificatefile that contains additional certificates needed to complete the CA’s chain of trust.

   Note

   Your CA may send you files in multiple formats intended for various purposes. For this tutorial, you should only use a certificate file in PEM format, which is usually (but not always) marked with a .pem or .crt extension. If you are uncertain which file to use, open the files with a text editor and find the one containing one or more blocks beginning with the following:

   - - - - -BEGIN CERTIFICATE - - - - - 

   The file should also end with the following:

   - - - -END CERTIFICATE - - - - -

   You can also test a file at the command line as follows:

   [ec2-user certs]$ openssl x509 -in certificate.crt -text

   Examine the output for the tell-tale lines described above. Do not use files ending with .p7b, .p7c, or similar extensions.

5. Remove or rename the old self-signed host certificate localhost.crt from the /etc/pki/tls/certs directory and place the new CA-signed certificate there (along with any intermediate certificates).

   Note

   There are several ways to upload your new certificate to your EC2 instance, but the most straightforward and informative way is to open a text editor (vi, nano, notepad, etc.) on both your local computer and your instance, and then copy and paste the file contents between them. You need root [sudo] privileges when performing these operations on the EC2 instance. This way, you can see immediately if there are any permission or path problems. Be careful, however, not to add any additional lines while copying the contents, or to change them in any way.

   From inside the /etc/pki/tls/certs directory, check that the file ownership, group, and permission settings match the highly restrictive Amazon Linux defaults (owner=root, group=root, read/write for owner only). The commands would be as follows:

   [ec2-user certs]$ sudo chown root.root custom.crt [ec2-user certs]$ sudo chmod 600 custom.crt [ec2-user certs]$ ls -al custom.crt

   The commands above should yield the following result:

   -rw------- root root custom.crt

   The permissions for the intermediate certificate file are less stringent (owner=root, group=root, owner can write, group can read, world can read). The commands would be:

   [ec2-user certs]$ sudo chown root.root intermediate.crt [ec2-user certs]$ sudo chmod 644 intermediate.crt [ec2-user certs]$ ls -al intermediate.crt

   The commands above should yield the following result:

   -rw-r--r-- root root intermediate.crt

6. If you used a custom key to create your CSR and the resulting host certificate, remove or rename the old key from the /etc/pki/tls/private/ directory, and then install the new key there.

   Note

   There are several ways to upload your custom key to your EC2 instance, but the most straightforward and informative way is to open a text editor (vi, nano, notepad, etc.) on both your local computer and your instance, and then copy and paste the file contents between them. You need root [sudo] privileges when performing these operations on the EC2 instance. This way, you can see immediately if there are any permission or path problems. Be careful, however, not to add any additional lines while copying the contents, or to change them in any way.

   From inside the /etc/pki/tls/private directory, check that the file ownership, group, and permission settings match the highly restrictive Amazon Linux defaults (owner=root, group=root, read/write for owner only). The commands would be as follows:

   [ec2-user private]$ sudo chown root.root custom.key [ec2-user private]$ sudo chmod 600 custom.key [ec2-user private]$ ls -al custom.key

   The commands above should yield the following result:

   -rw------- root root custom.key

7. Because the file name of the new CA-signed host certificate (custom.crt in this example) probably differs from the old certificate, edit /etc/httpd/conf.d/ssl.confand provide the correct path and file name using Apache’s SSLCertificateFile directive:

   SSLCertificateFile /etc/pki/tls/certs/custom.crt

   If you received an intermediate certificate file (intermediate.crt in this example), provide its path and file name using Apache’s SSLCACertificateFile directive:

   SSLCACertificateFile /etc/pki/tls/certs/intermediate.crt

   Note

   Some CAs combine the host certificate and the intermediate certificates in a single file, making this directive unnecessary. Consult the instructions provided by your CA.

   If you installed a custom private key (custom.key in this example), provide its path and file name using Apache’s SSLCertificateKeyFile directive:

   SSLCertificateKeyFile /etc/pki/tls/private/custom.key

8. Save /etc/httpd/conf.d/ssl.conf and restart Apache.

   [ec2-user ~]$ sudo service httpd restart

Step 3: Test and Harden the Security Configuration

After your SSL/TLS is operational and exposed to the public, you should test how secure it really is. This is easy to do using online services such as Qualys SSL Labs, which performs a free and thorough analysis of your security setup. Based on the results, you may decide to harden the default security configuration by controlling which protocols you accept, which ciphers you prefer, and which you exclude. For more information, see how Qualys formulates its scores.

On the Qualys SSL Labs site, type the fully qualified domain name of your server, in the form www.example.com. After about two minutes, you receive a grade (from A to F) for your site and a detailed breakdown of the findings. The table below summarizes the report for a domain with settings identical to the default Apache configuration on Amazon Linux and a default Certbot certificate:

The report shows that the configuration is mostly sound, with acceptable ratings for certificate, protocol support, key exchange, and cipher strength issues. The configuration also supports Forward secrecy, a feature of protocols that encrypt using temporary (ephemeral) session keys derived from the private key. This means in practice that attackers cannot decrypt HTTPS data even if they possess a web server’s long-term private key. However, the report also flags one serious vulnerability that is responsible for lowering the overall grade, and points to an additional potential problem:

Restart Apache after saving these changes to the edited configuration file.

If you test the domain again on Qualys SSL Labs, you should see that the RC4 vulnerability is gone and the summary looks something like the following:

Troubleshooting

Appendix: Let’s Encrypt with Certbot on Amazon Linux

The Let’s Encrypt certificate authority is the centerpiece of the Electronic Frontier Foundation (EFF) effort to encrypt the entire Internet. In line with that goal, Let’s Encrypt host certificates are designed to be created, validated, installed, and maintained with minimal human intervention. The automated aspects of certificate management are carried out by an agent running on the webserver. After you install and configure the agent, it communicates securely with Let’s Encrypt and performs administrative tasks on Apache and the key management system. This tutorial uses the free Certbot agent because it allows you either to supply a customized encryption key as the basis for your certificates, or to allow the agent itself to create a key based on its defaults. You can also configure Certbot to renew your certificates on a regular basis without human interaction, as described below in Configure Automated Certificate Renewal. For more information, consult the Certbot User Guide or man page.

Install and Run Certbot

While Certbot is not officially supported on Amazon Linux, and is not available from the Amazon Linux package repositories, it functions correctly once installed. These instructions are based on EFF’s documentation for installing Certbot on RHEL 6.

This procedure describes the default use of Certbot, resulting in a certificate based on a 2048-bit RSA key. If you want to experiment with customized keys, you might start with Using ECDSA certificates with Let’s Encrypt.

1. Enable the Extra Packages for Enterprise Linux (EPEL) repository from the Fedora project on your instance. Packages from EPEL are required as dependencies when you run the Certbot installation script.

   [ec2-user ~]$ sudo yum-config-manager --enable epel

2. Download the latest release of Certbot from EFF onto your EC2 instance using the following command.

   [ec2-user ~]$ wget https://dl.eff.org/certbot-auto

3. Make the downloaded file executable.

   [ec2-user ~]$ chmod a+x certbot-auto

4. Run the file with root permissions and the --debug flag.

   [ec2-user ~]$ sudo ./certbot-auto --debug

5. At the prompt “Is this ok [y/d/N],” type “y” and press Enter.
6. At the prompt “Enter email address (used for urgent renewal and security notices),” type a contact address and press Enter.
7. Agree to the Let’s Encrypt Terms of Service at the prompt. Type “A” and press Enter to proceed:

   -------------------------------------------------------------------------------
   Please read the Terms of Service at
   https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf. You must agree
   in order to register with the ACME server at
   https://acme-v01.api.letsencrypt.org/directory
   -------------------------------------------------------------------------------
   (A)gree/(C)ancel: A

8. Click through the authorization for EFF put you on their mailing list by typing “Y” or “N” and press Enter.
9. At the prompt shown below, type your Common Name (the name of your domain as described above) and your Subject Alternative Name (SAN), separating the two names with a space or a comma. Then press Enter. In this example, the names have been provided:

   No names were found in your configuration files. Please enter in your domain
   name(s) (comma and/or space separated)  (Enter 'c' to cancel):example.com www.example.com

10. On an Amazon Linux system with a default Apache configuration, you see output similar to the example below, asking about the first name you provided. Type “1” and press Enter.

    Obtaining a new certificate
    Performing the following challenges:
    tls-sni-01 challenge for example.com
    tls-sni-01 challenge for www.example.com
    
    We were unable to find a vhost with a ServerName or Address of example.com.
    Which virtual host would you like to choose?
    (note: conf files with multiple vhosts are not yet supported)
    -------------------------------------------------------------------------------
    1: ssl.conf                       |                       | HTTPS | Enabled
    -------------------------------------------------------------------------------
    Press 1 [enter] to confirm the selection (press 'c' to cancel): 1

11. Next, Certbot asks about the second name. Type “1” and press Enter.

    We were unable to find a vhost with a ServerName or Address of www.example.com.
    Which virtual host would you like to choose?
    (note: conf files with multiple vhosts are not yet supported)
    -------------------------------------------------------------------------------
    1: ssl.conf                       |                       | HTTPS | Enabled
    -------------------------------------------------------------------------------
    Press 1 [enter] to confirm the selection (press 'c' to cancel): 1

    At this point, Certbot creates your key and a CSR:

    Waiting for verification...
    Cleaning up challenges
    Generating key (2048 bits): /etc/letsencrypt/keys/0000_key-certbot.pem
    Creating CSR: /etc/letsencrypt/csr/0000_csr-certbot.pem

12. Authorize Certbot to create and all needed host certificates. When prompted for each name, type “1” and press Enter as shown in the example:

    We were unable to find a vhost with a ServerName or Address of example.com.
    Which virtual host would you like to choose?
    (note: conf files with multiple vhosts are not yet supported)
    -------------------------------------------------------------------------------
    1: ssl.conf                       |                       | HTTPS | Enabled
    -------------------------------------------------------------------------------
    Press 1 [enter] to confirm the selection (press 'c' to cancel): 1 Deploying Certificate for example.com to VirtualHost /etc/httpd/conf.d/ssl.conf We were unable to find a vhost with a ServerName or Address of www.example.com. Which virtual host would you like to choose? (note: conf files with multiple vhosts are not yet supported) ------------------------------------------------------------------------------- 1: ssl.conf | example.com | HTTPS | Enabled ------------------------------------------------------------------------------- Press 1 [enter] to confirm the selection (press 'c' to cancel): 1 Deploying Certificate for www.example.com to VirtualHost /etc/httpd/conf.d/ssl.conf

13. Choose whether to allow insecure connections to your web server. If you choose option 2 (as shown in the example), all connections to your server will either be encrypted or rejected.

    Please choose whether HTTPS access is required or optional. 
    -------------------------------------------------------------------------------
    1: Easy - Allow both HTTP and HTTPS access to these sites
    2: Secure - Make all requests redirect to secure HTTPS access
    -------------------------------------------------------------------------------
    Select the appropriate number [1-2] then [enter] (press 'c' to cancel): 2

    Certbot completes the configuration of Apache and reports success and other information:

    Congratulations! You have successfully enabled https://example.com and
    https://www.example.com
    
    You should test your configuration at:
    https://www.ssllabs.com/ssltest/analyze.html?d=example.com
    https://www.ssllabs.com/ssltest/analyze.html?d=www.example.com
    -------------------------------------------------------------------------------
    
    IMPORTANT NOTES:
     - Congratulations! Your certificate and chain have been saved at
       /etc/letsencrypt/live/example.com/fullchain.pem. Your cert will
       expire on 2017-07-19. To obtain a new or tweaked version of this
       certificate in the future, simply run certbot-auto again with the
       "certonly" option. To non-interactively renew *all* of your
       certificates, run "certbot-auto renew"
    ....

14. After you complete the installation, test and optimize the security of your server as described in Step 3: Test and Harden the Security Configuration.

Configure Automated Certificate Renewal

Certbot is designed to become an invisible, error-resistant part of your server system. By default, it generates host certificates with a short, 90-day expiration time. Prior to expiration, re-run the certbot command manually if you have not previously allowed your system to call the command automatically. This procedure shows how to automate Certbot by setting up a cron job.

1. After you have successfully run Certbot for the first time, open /etc/crontab in a text editor and add a line similar to the following:

   39      1,13    *       *       *       root    /home/ec2-user/certbot-auto renew --no-self-upgrade --debug

   Here is an explanation of each component:

   39 1,13 * * *

   Schedules a command to be run at 01:39 and 13:39 every day. The selected values are arbitrary, but the Certbot developers suggest running the command at least twice daily.

   root

   The command runs with root privileges.

   /home/ec2-user/certbot-auto renew --no-self-upgrade --debug

   The command to be run. The path /home/ec2-user/ assumes that you installed Certbot in your default user home directory; adjust this as necessary. The renew subcommand causes Certbot to check any previously obtained certificates and to renew those that are approaching expiration. The --no-self-upgradeflag prevents Certbot from upgrading itself without your intervention. The --debug flag avoids possible compatibility problems.

   Save the file when done.

2. Restart the cron daemon:

   [ec2-user ~]$ sudo service crond restart