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OpenSSL allows you to create, modify, and view certificates and private keys. You can use it to generate [[Self Signed SSL Certificates]].


== General OpenSSL Commands ==
==General OpenSSL Commands==


=== Generate Keys and Certificate Signing Requests ===
These commands allow you to generate CSRs, Certificates, Private Keys and do other miscellaneous tasks.
These commands allow you to generate CSRs, Certificates, Private Keys and do other miscellaneous tasks.
{| class="wikitable"
!Task
!Command
|-
|Generate a new private key
|{{highlight|lang=terminal|code=
# openssl req -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key
}}Or just a 4096 bit RSA:{{highlight|lang=terminal|code=
# openssl genrsa -out server.key 4096
}}
|-
|Generate a new private key and Certificate Signing Request
|{{highlight|lang=terminal|code=
# openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout privateKey.key -out certificate.crt
}}
|-
|Generate a certificate signing request with an existing private key
|{{highlight|lang=terminal|code=
# openssl req -out CSR.csr -key privateKey.key -new
}}
|-
|Generate a certificate signing request based on an existing certificate
|{{highlight|lang=terminal|code=
# openssl x509 -x509toreq -in certificate.crt -out CSR.csr -signkey privateKey.key
}}
|-
|Generate a certificate signing request for various SANs.
|{{highlight|lang=terminal|code=
# openssl req -new -sha256 \
        -key server.key \
        -subj "/C=CA/ST=Alberta/O=Steamr/CN=steamr.com" \
        -reqexts SAN \
        -extensions SAN \
        -config <(cat /etc/ssl/openssl.cnf <(printf "[SAN]\nsubjectAltName=DNS:x.steamr.com,DNS:y.steamr.com")) \
        -out server.csr
}}
|-
|Remove a passphrase from a private key
|{{highlight|lang=terminal|code=
# openssl rsa -in privateKey.pem -out newPrivateKey.pem
}}
|}


Generate a new private key and Certificate Signing Request
=== Verification ===
openssl req -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key
{| class="wikitable"
!Task
!Command
|-
|View a PEM certificate
|{{highlight|lang=terminal|code=
# openssl x509 -in certificate.crt -text -noout
}}
|-
|Check a PKCS#12 file (.pfx or .p12)
|{{highlight|lang=terminal|code=
# openssl pkcs12 -info -in keyStore.p12
}}
|-
|View a certificate signing request
|{{highlight|lang=terminal|code=
# openssl req -text -noout -verify -in CSR.csr
}}
|-
|Check a private key
|{{highlight|lang=terminal|code=
# openssl rsa -in privateKey.key -check
}}
|-
|Check if your certificate matches a key
|{{highlight|lang=terminal|code=
# 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
}}
|}


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
==Checking & Verifying==
openssl rsa -in privateKey.pem -out newPrivateKey.pem
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. It might be a good idea to use an online SSL checker service as well to determine what issues that are with the installed certificate.


The public key should match your private key and must be used in your certificate and certificate signing request. You can verify this by running:
{{highlight|lang=terminal|code=
# 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
}}


===Remote Server Certificate===
All the certificates (including Intermediates) should be displayed when using {{code|s_client}}.


== Checking Using OpenSSL ==
SNI allows virtual hosting of multiple domains on the same IP address. It is a mechanism that allows the web server to know which domain is being accessed in order to use the proper certificate when establishing a connection to the client.  For websites that have been assigned a dedicated IP address, using SNI is not required.


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.
If the server is not using SNI:
{{highlight|lang=terminal|code=
# openssl s_client -showcerts -connect www.paypal.com:443
}}


Check a Certificate Signing Request (CSR)
If the server is using SNI, you will need to provide the hostname:
openssl req -text -noout -verify -in CSR.csr
{{highlight|lang=terminal|code=
# openssl s_client -showcerts -servername www.paypal.com -connect www.paypal.com:443
}}


Check a private key
The x509 certificate can be retrieved in either case by piping the output through {{code| openssl x509 -text}}.
openssl rsa -in privateKey.key -check
{{highlight|lang=terminal|code=
 
# openssl s_client -showcerts -connect www.paypal.com:443 | openssl x509 -text
Check a certificate
# openssl s_client -showcerts -servername www.paypal.com -connect www.paypal.com:443 | openssl x509 -text
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 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
 
== Converting Using OpenSSL ==


==Certificate and Key Conversion==
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.
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
Convert a DER file (.crt .cer .der) to PEM
openssl x509 -inform der -in certificate.cer -out certificate.pem
{{highlight|lang=terminal|code=
# openssl x509 -inform der -in certificate.cer -out certificate.pem
}}


Convert a PEM file to DER
Convert a PEM file to DER
openssl x509 -outform der -in certificate.pem -out certificate.der
{{highlight|lang=terminal|code=
# 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
Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates to PEM
openssl pkcs12 -in keyStore.pfx -out keyStore.pem -nodes
{{highlight|lang=terminal|code=
# 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.
You can add {{code|-nocerts}} to only output the private key or add {{code|-nokeys}} to only output the certificates.


Convert a PEM certificate file and a private key to PKCS#12 (.pfx .p12)
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
{{highlight|lang=terminal|code=
# openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt
}}




==See Also==


*https://www.sslshopper.com/article-most-common-openssl-commands.html
*[[Self Signed SSL Certificates]]


== See Also ==
{{Navbox Linux}}
* https://www.sslshopper.com/article-most-common-openssl-commands.html
[[Category:Linux]]
* [[Self Signed SSL Certificates]]
 
[[Category:Linux]]{{Navbox Linux}}
[[Category:LinuxUtilities]]
[[Category:LinuxUtilities]]
{{Navbox Linux}}
[[Category:Certificates]]
{{Navbox Certificates}}

Latest revision as of 02:39, 7 February 2022

OpenSSL allows you to create, modify, and view certificates and private keys. You can use it to generate Self Signed SSL Certificates.

General OpenSSL Commands

Generate Keys and Certificate Signing Requests

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

Task Command
Generate a new private key 
# openssl req -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key
Or just a 4096 bit RSA:
# openssl genrsa -out server.key 4096
Generate a new private key and Certificate Signing Request 
# openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout privateKey.key -out certificate.crt
Generate a certificate signing request with 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
Generate a certificate signing request for various SANs. 
# openssl req -new -sha256 \
        -key server.key \
        -subj "/C=CA/ST=Alberta/O=Steamr/CN=steamr.com" \
        -reqexts SAN \
        -extensions SAN \
        -config <(cat /etc/ssl/openssl.cnf <(printf "[SAN]\nsubjectAltName=DNS:x.steamr.com,DNS:y.steamr.com")) \
        -out server.csr
Remove a passphrase from a private key 
# openssl rsa -in privateKey.pem -out newPrivateKey.pem

Verification

Task Command
View a PEM certificate 
# openssl x509 -in certificate.crt -text -noout
Check a PKCS#12 file (.pfx or .p12) 
# openssl pkcs12 -info -in keyStore.p12
View a certificate signing request 
# openssl req -text -noout -verify -in CSR.csr
Check a private key 
# openssl rsa -in privateKey.key -check
Check if your certificate matches a key 
# openssl x509 -noout -modulus -in certificate.crt



Checking & Verifying

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. It might be a good idea to use an online SSL checker service as well to determine what issues that are with the installed certificate.

The public key should match your private key and must be used in your certificate and certificate signing request. You can verify this by running: 

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

Remote Server Certificate

All the certificates (including Intermediates) should be displayed when using s_client.

SNI allows virtual hosting of multiple domains on the same IP address. It is a mechanism that allows the web server to know which domain is being accessed in order to use the proper certificate when establishing a connection to the client. For websites that have been assigned a dedicated IP address, using SNI is not required.

If the server is not using SNI: 

# openssl s_client -showcerts -connect www.paypal.com:443

If the server is using SNI, you will need to provide the hostname: 

# openssl s_client -showcerts -servername www.paypal.com -connect www.paypal.com:443

The x509 certificate can be retrieved in either case by piping the output through openssl x509 -text. 

# openssl s_client -showcerts -connect www.paypal.com:443

Certificate and Key Conversion

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


See Also

Various Linux Notes
Linux Tools and Utilites
Package Management
Linux Distributions
Networking
Containers
Certificates