- The following sections describe how to use OpenSSL to generate a CSR for a single host name. If you want to generate a CSR for multiple host names, we recommend using the Cloud Control Panel or the MyRackspace Portal. Install OpenSSL. Check whether OpenSSL is installed by using the following command: CentOS® and Red Hat® Enterprise Linux®.
- Generating the Public Key - Windows 1. At the command prompt, type the following: openssl rsa -in rsa.private -out rsa.public -pubout -outform PEM 2. The public key is saved in a file named rsa.public located in the same folder. Generating the Private Key - Linux 1. Open the Terminal. Navigate to the folder with the.
Openssl req -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key will include your public key. This is mandatory as per the PKI process. The CSR, containing your entity information and the public key is sent to any Certificate Authority you like for a request of certificate (hence the CSR name).
Common OpenSSL Commands with Keys and Certificates
Generate RSA private key with certificate in a single command
Generate Certificate Signing Request (CSR) from private key with passphrase
Generate RSA private key (2048 bit)
Generate a Certificate Signing Request (CSR)
Generate RSA private key (2048 bit) and a Certificate Signing Request (CSR) with a single command
Convert private key to PEM format
Generate a self-signed certificate that is valid for a year with sha256 hash
View details of a RSA private key
View details of a CSR
View details of a Certificate
View details of a Certificate in DER format
Convert a DER file (.crt .cer .der) to PEM
Convert a PEM file to DER
While Encrypting a File with a Password from the Command Line using OpenSSLis very useful in its own right, the real power of the OpenSSL library is itsability to support the use of public key cryptograph for encrypting orvalidating data in an unattended manner (where the password is not required toencrypt) is done with public keys.
The Commands to Run
Generate a 2048 bit RSA Key
You can generate a public and private RSA key pair like this:
openssl genrsa -des3 -out private.pem 2048
That generates a 2048-bit RSA key pair, encrypts them with a password you provideand writes them to a file. You need to next extract the public key file. You willuse this, for instance, on your web server to encrypt content so that it canonly be read with the private key.
Export the RSA Public Key to a File
This is a command that is
openssl rsa -in private.pem -outform PEM -pubout -out public.pem
The
-pubout
flag is really important. Be sure to include it.Next open the
public.pem
and ensure that it starts with-----BEGIN PUBLIC KEY-----
. This is how you know that this file is thepublic key of the pair and not a private key.To check the file from the command line you can use the
less
command, like this:less public.pem
Do Not Run This, it Exports the Private Key
A previous version of the post gave this example in error.
openssl rsa -in private.pem -out private_unencrypted.pem -outform PEM
The error is that the
-pubout
was dropped from the end of the command.That changes the meaning of the command from that of exporting the public keyto exporting the private key outside of its encrypted wrapper. Inspecting theoutput file, in this case private_unencrypted.pem
clearly shows that the keyis a RSA private key as it starts with -----BEGIN RSA PRIVATE KEY-----
.Visually Inspect Your Key Files
It is important to visually inspect you private and public key files to makesure that they are what you expect. OpenSSL will clearly explain the nature ofthe key block with a
-----BEGIN RSA PRIVATE KEY-----
or -----BEGIN PUBLIC KEY-----
.Generate Public Key From Csr Openssl 1
You can use less to inspect each of your two files in turn:
less private.pem
to verify that it starts with a-----BEGIN RSA PRIVATE KEY-----
less public.pem
to verify that it starts with a-----BEGIN PUBLIC KEY-----
The next section shows a full example of what each key file should look like.
The Generated Key Files
The generated files are base64-encoded encryption keys in plain text format.If you select a password for your private key, its file will be encrypted withyour password. Be sure to remember this password or the key pair becomes useless.
The private.pem file looks something like this:
The public key, public.pem, file looks like:
Protecting Your Keys
Depending on the nature of the information you will protect, it’s important tokeep the private key backed up and secret. The public key can be distributedanywhere or embedded in your web application scripts, such as in your PHP,Ruby, or other scripts. Again, backup your keys!
Remember, if the key goes away the data encrypted to it is gone. Keeping aprinted copy of the key material in a sealed envelope in a bank safety depositbox is a good way to protect important keys against loss due to fire or harddrive failure.
Oh, and one last thing.
Openssl Generate Csr San
If you, dear reader, were planning any funny business with the private key that I have just published here. Know that they were made especially for this series of blog posts. I do not use them for anything else.
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