Overview#Obtain a Certificate from Server with OpenSSL
Obtain Subject Alternative Name#We found we often needed to verify the Subject Alternative Name of Certificates when doing installs and validations. Bouncing around in Imanager or other tools took too long and we came up with this.
openssl s_client -connect ldap.willeke.com:636 | openssl x509 -noout -text | egrep -A 1 'X509v3 Subject Alternative Name:' depth=1 O = UNIXAUTH, OU = Organizational CA verify error:num=19:self signed certificate in certificate chain verify return:0 X509v3 Subject Alternative Name: IP Address:10.220.180.80, IP Address:10.220.180.81, IP Address:10.220.21.19, DNS:ldap.willeke.com
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 -new -newkey rsa:2048 -nodes -keyout privateKey.key
Generate a self-signed certificate (see How to Create and Install an Apache Self Signed Certificate for more info)#
openssl req -x509 -nodes -days 365 -newkey rsa:2048 -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
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 md5 or openssl rsa -noout -modulus -in privateKey.key | openssl md5 or openssl req -noout -modulus -in CSR.csr | openssl md5
Check an SSL connection. All the certificates (including Intermediates) should be displayed#
openssl s_client -connect www.paypal.com:443Converting Certificate Formats 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.
More Information#There might be more information for this subject on one of the following:
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