Derwynd's Weblog

Derwynd's Weblog

Open SSL help

General OpenSSL Commands

These commands allow you to generate CSRs, Certificates, Private Keys and do other miscellaneous tasks.

* Generate a new private key and Certificate Signing Request

# openssl req -out CSR.csr -pubkey -new -keyout privateKey.key

* Generate a self-signed certificate

# openssl req -x509 -nodes -days 365 -newkey rsa:1024 -keyout privateKey.key -out certificate.crt

* Generate a certificate signing request (CSR) for an existing private key

# openssl req -out CSR.csr -key privateKey.key -new

* Generate a certificate signing request based on an existing certificate

# openssl x509 -x509toreq -in certificate.crt -out CSR.csr -signkey privateKey.key

* Remove a passphrase from a private key

# openssl rsa -in privateKey.pem -out newPrivateKey.pem

Checking Using OpenSSL

If you need to check the information within a Certificate, CSR or Private Key, use these commands. You can also check CSRs and check certificates using our online tools.

* Check a Certificate Signing Request (CSR)

# openssl req -text -noout -verify -in CSR.csr

* Check a private key

# openssl rsa -in privateKey.key -check

* Check a certificate

# openssl x509 -in certificate.crt -text -noout

* Check a PKCS#12 file (.pfx or .p12)

# openssl pkcs12 -info -in keyStore.p12

Debugging Using OpenSSL

If you are receiving an error that the private doesn’t match the certificate or that a certificate that you installed to a site is not trusted, try one of these commands. If you are trying to verify that an SSL certificate is installed correctly, be sure to check out the SSL Checker.

* Check an MD5 hash of the public key to ensure that it matches with what is in a CSR or private key

# openssl x509 -noout -modulus -in certificate.crt | openssl md5openssl rsa -noout -modulus -in privateKey.key | openssl md5openssl req -noout -modulus -in CSR.csr | openssl md5

* Check an SSL connection. All the certificates (including Intermediates) should be displayed

# openssl s_client -connect

Converting Using OpenSSL

These commands allow you to convert certificates and keys to different formats to make them compatible with specific types of servers or software. For example, you can convert a normal PEM file that would work with Apache to a PFX (PKCS#12) file and use it with Tomcat or IIS. Use our SSL Converter to convert certificates without messing with OpenSSL.

* Convert a DER file (.crt .cer .der) to PEM

# openssl x509 -inform der -in certificate.cer -out certificate.pem

* Convert a PEM file to DER

# openssl x509 -outform der -in certificate.pem -out certificate.der

* Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates to PEM

# openssl pkcs12 -in keyStore.pfx -out keyStore.pem -nodes

You can add -nocerts to only output the private key or add -nokeys to only output the certificates.
* Convert a PEM certificate file and a private key to PKCS#12 (.pfx .p12)

# openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt

* To test SSL connections to a mail server, use the openssl command with the s_client parameter:

# openssl s_client -connect -starttls smtp

This essentially opens a telnet-like connection to on port 25 using the STARTTLS extension. This is an interactive session, so you can send commands to the remote SMTP server as well as view the certificate used, view the details of the SSL session, and more. To test SMTP over SSL, don’t use the -starttls option:

# openssl s_client -connect

* The above can also be used to connect to any service that uses SSL, such as HTTPS (port 443), POP3 over SSL (port 995), and so forth.

* The openssl command can also be used to create digests of a file, which can be used to verify that a file has not been tampered with:

# echo “test file”> foo.txt

# openssl dgst -md5 foo.txt

MD5(foo.txt)= b05403312f66bdc8ccc597fedf6cd5fe

# openssl dgst -sha1 foo.txt

SHA1(foo.txt)= 0181d93fff60b818g3f92e470ea97a2aff4ca56a

* To view the other message digests that can be used, look at the output of openssl list-message-digest-commands.

* You can also use openssl to encrypt files. To view the list of available ciphers, use openssl list-cipher-commands. Once you’ve chosen a cipher to use, you can encrypt the file using the following commands:

# openssl enc -aes-256-cbc -salt -in foo.txt -out foo.enc

enter aes-256-cbc encryption password:

Verifying – enter aes-256-cbc encryption password:

# file foo.enc

foo.enc: data

# cat foo.enc

Salted__yvi{!e????i”Yt?;(Ѱ e%
# openssl enc -d -aes-256-cbc -in foo.enc

enter aes-256-cbc decryption password:

test file

In the above example, the file foo.txt was encrypted using 256-bit AES in CBC mode, the encrypted copy being saved as the file foo.enc. Looking at the contents of the file provide gibberish. Decrypting the file is done using the -d option; however, keep in mind that not only do you need to remember the password, you also need to know the cipher used.

As you can see, OpenSSL provides more than just a library for other applications to use, and the openssl command-line binary is a powerful program in its own right, allowing for many uses.

January 14, 2010 - Posted by | Uncategorized

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