OpenSSL create self signed certificate Linux with example Table of Contents Steps required to create self signed certificate in Linux Install openssl Create encrypted password file (Optional) Openssl create self signed certificate with passphrase Generate private key Create Certificate Signing Request (CSR) certificate Create self signed certificate using openssl x509 Openssl verify certificate content Openssl self signed certificate without passphrase Openssl generate private key Create certificate Signing Request (CSR) certificate Create self signed certificate using openssl x509 Openssl verify certificate content Setup Apache with self signed certificate

Steps required to create self signed certificate in Linux The steps involved to generate self signed certificate include:

Generate private key server.key Create Certificate Signing Request (CSR) server.csr Sign the certificate signing request and generate self signed certificate server.crt

Install openssl On RHEL/CentOS 7/8 you can use yum/dnf respectively while on Ubuntu use apt-get to install openssl rpm

NOTE: On RHEL system you must have an active subscription to RHN or you can configure a local offline repository using which "yum" package manager can install the provided rpm and it's dependencies. [root@centos8-1 ~]# yum -y install openssl

Create encrypted password file (Optional) With openssl self signed certificate you can generate private key with and without passphrase. If you use any type of encryption while creating private key then you will have to provide passphrase every time you try to access private key. With the encrypted password file we can avoid entering the password when we create self signed certificate. I have created a plain text file "mypass" with my "secret" passphrase

[root@centos8-1 ~]# echo secret > mypass Using openssl enc I will encrypt mypass file and create an encrypted file mypass.enc

[root@centos8-1 ~]# openssl enc -aes256 -pbkdf2 -salt -in mypass -out mypass.enc enter aes-256-cbc encryption password: Verifying - enter aes-256-cbc encryption password: As you see the content of the encrypted file is not readable any more. Now you can easily share this encrypted file to any user to generate ssl certificate

[root@centos8-1 ~]# cat mypass.enc Salted__▒▒Y$▒V΃cQVȥ▒2ĺ)▒MS▒ To decrypt the encrypted password file, we use below command:

[root@centos8-1 ~]# openssl enc -aes256 -pbkdf2 -salt -d -in mypass.enc enter aes-256-cbc decryption password: secret

I will create a new directory to store my certificates

[root@centos8-1 certs]# mkdir /root/certs [root@centos8-1 certs]# cd /root/certs I have also copied my encrypted password file to /root/certs

[root@centos8-1 certs]# ls -l total 8 -rw-r--r-- 1 root root 32 Apr 9 13:31 mypass.enc

Openssl create self signed certificate with passphrase In this section I will share the examples to openssl create self signed certificate with passphrase but we will use our encrypted file mypass.enc to create private key and other certificate files.

Generate private key We need to generate private key which will use in next steps to create Certificate Signing Request (CSR) In this example we will create private key with 3DES encryption. You can also choose any other encyption. [root@centos8-1 certs]# openssl genrsa -des3 -passout file:mypass.enc -out server.key 4096 Generating RSA private key, 4096 bit long modulus (2 primes) ................................................++++ ..++++ e is 65537 (0x010001) HINT: In this example I have used -passout with file:, but you can also use pass:, env:, fd:. You can read more about these options: Network Security with OpenSSL. if you do not use -passout option, openssl generate private key command would prompt for the passphrase before generating private key.

Create Certificate Signing Request (CSR) certificate ALSO READ: Many people miss most important points when they are creating a CSR. If you are not sure about what should be added for individual fields then I would recommend to read this article before you generate CSR: Things to consider when creating CSR with OpenSSL

Next create a certificate signing request (server.csr) using the openssl private key (server.key).

This command will prompt for a series of things (country, state or province, etc.). Make sure that "Common Name" matches the registered fully qualified domain name of your Linux server (or your IP address if you don't have one). Alternatively you can also create SAN certification which will allow you to provide multiple Alternative Names in a single certificate.

Country Name (2 letter code) [XX]:IN State or Province Name (full name) []:KARNATAKA Locality Name (eg, city) [Default City]:BENGALURU Organization Name (eg, company) [Default Company Ltd]:GoLinuxCloud Organizational Unit Name (eg, section) []:R&D Common Name (eg, your name or your server's hostname) []:centos8-1 Email Address []:[email protected]

Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []: An optional company name []:

(Optional) To automate this step to create CSR (server.csr) we can either use openssl.cnf or create one configuration file with required input as I have shown below：

[root@centos8-1 certs]# cat self_signed_certificate.cnf [req] distinguished_name = req_distinguished_name prompt = no [req_distinguished_name] C = IN ST = Karnataka L = Banaglore O = GoLinuxCloud OU = SDM CN = centos8-1

Now to create CSR using this config file (If you have already created server.csr then you can ignore this):

[root@centos8-1 certs]# openssl req -new -key server.key -out server.csr -passin file:mypass.enc -config self_signed_certificate.cnf

Here we are using -config to take input from self_signed_certificate.cnf file. But make sure you change CN value based on your server hostname.

Create self signed certificate using openssl x509 The openssl x509 command is a multi purpose certificate utility. It can be used to display certificate information, convert certificates to various forms, sign certificate requests like a "mini CA" or edit certificate trust settings The last step to create self signed certificate is to sign the certificate signing request. In this example the openssl certificate will last for 365 days. We will use use our private key "server.key" with "server.csr" to sign the certificate and generate self signed certificate server.crt [root@centos8-1 certs]# openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt -passin file:mypass.enc Signature ok subject=C = IN, ST = Karnataka, L = Banaglore, O = GoLinuxCloud, OU = SDM, CN = centos8-1 Getting Private key So our our openssl generate ssl certificate commands were successful and we have our self signed certificate server.crt

Openssl verify certificate content In this article we have create below certificates

server.key ⇒ Private Key server.csr ⇒ Certificate Signing Request server.crt ⇒ Self-signed certificate You can view the content of self signed certificate and other files using openssl:

Openssl self signed certificate without passphrase In this section I will share the examples to create openssl self signed certificate without passphrase. All the commands and steps will remain the same as we used above to generate self signed certificate, the only difference would be that we will not use any encryption method while we create private key in step 1

Openssl generate private key In this example with openssl genrsa we will not use any encryption:

[root@centos8-1 certs]# openssl genrsa -out server-noenc.key 4096 Generating RSA private key, 4096 bit long modulus (2 primes) ................................................................++++ ...................................................................................................++++ e is 65537 (0x010001) As expected the openssl generate private key was executed without prompting for any passphrase.

Create certificate Signing Request (CSR) certificate Next we will create CSR certificate using our private key. Again make sure you provide proper Common Name value and it should match the hostname/FQDN of your server's detail where you plan to use this certificate.

Country Name (2 letter code) [XX]:IN State or Province Name (full name) []:KARNATAKA Locality Name (eg, city) [Default City]:BENGALURU Organization Name (eg, company) [Default Company Ltd]:GoLinuxCloud Organizational Unit Name (eg, section) []:R&D Common Name (eg, your name or your server's hostname) []:centos8-1 Email Address []:[email protected]

Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []: An optional company name []: To automate this step again you can create a configuration file as we created in this step....

Create self signed certificate using openssl x509 Now in the last step using openssl x509 we will create and sign our certificate using server-noenc.key and server-noenc.csr

[root@centos8-1 certs]# openssl x509 -req -days 365 -in server-noenc.csr -signkey server-noenc.key -out server-noenc.crt Signature ok subject=C = IN, ST = KARNATAKA, L = BENGALURU, O = GoLinuxCloud, OU = R&D, CN = centos8-1, emailAddress = [email protected] Getting Private key

Openssl verify certificate content In this article we have create below certificates

server-noenc.key ⇒ Private Key server-noenc.csr ⇒ Certificate Signing Request server-noenc.crt ⇒ Self-signed certificate You can view the content of self signed certificate and other files using openssl:

Setup Apache with self signed certificate After you create self signed certificates, you can these certificate and key to set up Apache with SSL (although browser will complain of insecure connection).

Transfer server.crt and server.key to your Apache server and then define below values inside Virtual Hosting of /etc/https/conf/httpd.conf file

SSLEngine On SSLCertificateFile /path/to/server.crt SSLCertificateKeyFile /path/to/server.key Next restart your httpd service and now you can use your Apache over HTTPS. But this is not considered secure and you should configure server client certificates to set up Apache with SSL for end to end encryption.

Lastly I hope the steps from the article to openssl create self signed certificate Linux was helpful. So, let me know your suggestions and feedback using the comment section.

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