Generate, check, debug and convert with OpenSSL

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
    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 CSR and key for a SAN sertificateCreate a config file called req.cnf to use it with openssl like the following:
  • [req] 
    distinguished_name = req_distinguished_name 
    req_extensions = v3_req 
    prompt = no 
    [req_distinguished_name] 
    C = NL 
    ST = NL 
    L = Amsterdam 
    O = Red Light District B.V. 
    OU = IT 
    CN = amsterdamredlights.nl 
    [v3_req] 
    keyUsage = keyEncipherment, dataEncipherment 
    extendedKeyUsage = serverAuth 
    subjectAltName = @alt_names 
    [alt_names] 
    DNS.1 = www.amsterdamredlights.nl 
    DNS.2 = amsterdamredlights.nl 
    DNS.3 = intranet.redlightdistrict.nl

With this file use the following command:

openssl req -new -out redlightsdistrict.nl.csr -newkey rsa:2048 -nodes -sha256 -keyout redlightsdistrict.nlkey.temp -config req.cnf
  • 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.

  • 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 a CA bundle against a certificate
    openssl verify -verbose -purpose sslserver -CAfile <chain file> <cert>
    • Check certificate issuer
openssl x509 -noout -in cert.pem -issuer
    • Check the subject for whom the cert has been issued
openssl x509 -noout -in cert.pem -subject
    • Check validity (dates)
openssl x509 -noout -in cert.pem -dates
    • Check the above 3, all at once
openssl x509 -noout -in cert.pem -issuer -subject -dates
    • Check hash value
 openssl x509 -noout -in cert.pem -hash
    • Check certificate MD5 fingerprint
openssl x509 -noout -in cert.pem -fingerprint

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
openssl rsa -noout -modulus -in privateKey.key | openssl md5
openssl req -noout -modulus -in CSR.csr | openssl md5

 

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.

  • 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
    openssl rsa -noout -modulus -in privateKey.key | openssl md5
    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:443
  • If the dns hasn’t propagated yet you can use an ip address and a hostname like the following example
$ openssl s_client -connect 127.0.0.1:443 -servername giuseppeurso.net

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.

  • 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
  • Convert a p7b (non binary) certificate to Pem
    openssl pkcs7 -in certificate_file.p7b -print_certs -out cert.pem

    If this throws an error, just open the p7b fiel and replace:

    -----BEGIN PKCS #7 SIGNED DATA-----
    -----END PKCS #7 SIGNED DATA-----
    

    with

    -----BEGIN CERTIFICATE-----
    -----END CERTIFICATE-----
    • Convert a p7b (binary) certificate to Pem

      You can easily guess whether a certificate is in a binary form by looking at it with for instance the cat command, If it looks garbled it’s binary
      In these cases you should first convert it from binary tand then you can convert it to pem with the previous example. This is how you convert it if binary:

      openssl pkcs7 -inform der -in a.p7b -out a.cer
    • SSL bundle concatenation order for haproxy:
-----BEGIN MY CERTIFICATE-----
-----END MY CERTIFICATE-----
-----BEGIN INTERMEDIATE CERTIFICATE-----
-----END INTERMEDIATE CERTIFICATE-----
-----BEGIN INTERMEDIATE CERTIFICATE-----
-----END INTERMEDIATE CERTIFICATE-----
-----BEGIN ROOT CERTIFICATE-----
-----END ROOT CERTIFICATE-----
-----BEGIN RSA PRIVATE KEY-----
-----END RSA PRIVATE KEY-----

 

Originally posted on Sun Jan 13, 2008 at https://www.sslshopper.com/article-most-common-openssl-commands.html expanded, enriched and improved with personal experiences since then.

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Free SSL Certificate to Ispconfig websites with Startssl – How to

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This article will go through the complete process in order to obtain, install and run an SSL Webserver Certificate for free with ISPConfig3 and Startssl dot com.
Some years ago i discovered this useful service for generating Class 2 webserver certificates, very useful to offer your user a secure, encrypted connection over wich they can send their data reducing the risks of being sniffed (i’ll write something about sniffing).
Continue reading “Free SSL Certificate to Ispconfig websites with Startssl – How to”

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