OpenSSL is an open-source software library that provides SSL (Secure Sockets Layer) and TLS (Transport Layer Security) protocols. OpenSSL is widely used to generate and manage digital certificates, including CRL (Certificate Revocation List) files. In this article, we will explore how to convert CRL files to PEM format using OpenSSL.
What is a CRL File?
A Certificate Revocation List (CRL) is a file that contains a list of digital certificates that have been revoked by a Certificate Authority (CA). CRL files are used to verify the validity of digital certificates. CRL files are typically in the DER (Distinguished Encoding Rules) format, which is a binary format. However, some applications require CRL files in the PEM (Privacy Enhanced Mail) format, which is a base64-encoded ASCII format.
DER vs PEM Format
DER (Distinguished Encoding Rules) is a binary format that is used to represent digital certificates and CRL files. DER files are typically smaller than PEM files because they do not contain base64-encoded characters. PEM (Privacy Enhanced Mail), on the other hand, is a base64-encoded ASCII format. PEM files are larger than DER files because they contain base64-encoded characters.
Converting CRL Files to PEM Format
To convert a CRL file from DER format to PEM format, we will use the OpenSSL command-line tool. Here are the steps to follow:
- Open a terminal window and navigate to the directory where the CRL file is located.
- Run the following command to convert the CRL file from DER to PEM format:
openssl crl -inform DER -outform PEM -in <CRL_FILE_NAME>.crl -out <PEM_FILE_NAME>.pem
In this command, replace <CRL_FILE_NAME> with the name of your CRL file (without the .crl extension) and <PEM_FILE_NAME> with the name you want to give to your PEM file (with the .pem extension).
- Press Enter to run the command. OpenSSL will convert the CRL file from DER to PEM format and create a new file with the specified name in the same directory.
Example
Let’s say you have a CRL file named example.crl in the directory /home/user/crls/. You want to convert this file to PEM format and name the new file example.pem. Here’s how you would run the command:
openssl crl -inform DER -outform PEM -in /home/user/crls/example.crl -out /home/user/crls/example.pem
This command will convert the example.crl file to example.pem and save it in the /home/user/crls/ directory.
FAQs: openssl convert crl to pem format
What is a CRL?
A Certificate Revocation List (CRL) is a list of digital certificates that have been revoked or invalidated by the certificate authority (CA) that issued them. CRLs are used by relying parties (e.g. web browsers) to check whether a particular certificate has been revoked and should no longer be trusted.
What is a PEM format?
PEM (Privacy Enhanced Mail) is a standard format for storing and transferring digital certificates and keys. PEM files are base64-encoded and have a header and footer that define the type of data they contain. PEM format can store certificates, CRLs, private keys, and certificates with their associated private keys.
How do I convert a CRL to PEM format using OpenSSL?
You can use the OpenSSL command-line tool to convert a CRL file to PEM format. The following command will convert a CRL file (e.g. crl.crl) to PEM format and output the result to stdout:
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openssl crl -inform DER -in crl.crl -outform PEM -out crl.pem
This command specifies that the input format (-inform) is DER, the input file is crl.crl, the output format (-outform) is PEM, and the output file (-out) is crl.pem. You can redirect the output to a file using standard shell redirection (e.g. > crl.pem).
Can I convert a PEM formatted CRL back to DER format?
Yes, you can use the same OpenSSL command-line tool to convert a PEM formatted CRL back to DER format. The following command will convert a PEM formatted CRL file (e.g. crl.pem) to DER format:
openssl crl -inform PEM -in crl.pem -outform DER -out crl.crl
This command specifies that the input format is PEM, the input file is crl.pem, the output format is DER, and the output file is crl.crl. You can redirect the output to a file using standard shell redirection (e.g. > crl.crl).