Creating a Self-Signed Certificate: Difference between revisions

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= Creating Certificates =
== Standard Certificates ==
== Standard Certificates ==


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== Creating a Cert with a SAN ==
== Creating a Cert with a SAN ==


(from https://geekflare.com/san-ssl-certificate/)


Create a file named ''san.cnf'' with the following information:
Create a file named ''san.cnf'' with the following information:
<pre>[ req ]
<pre>[req]
default_bits      = 2048
distinguished_name = req_distinguished_name
distinguished_name = req_distinguished_name
req_extensions    = req_ext
x509_extensions = v3_req
[ req_distinguished_name ]
prompt = no
countryName                = Country Name (2 letter code)
[req_distinguished_name]
stateOrProvinceName        = State or Province Name (full name)
C = US
localityName              = Locality Name (eg, city)
ST = VA
organizationName          = Organization Name (eg, company)
L = SomeCity
commonName                = Common Name (e.g. server FQDN or YOUR name)
O = MyCompany
[ req_ext ]
OU = MyDivision
CN = www.company.com
[v3_req]
keyUsage = keyEncipherment, dataEncipherment
extendedKeyUsage = serverAuth
subjectAltName = @alt_names
subjectAltName = @alt_names
[alt_names]
[alt_names]
DNS.1   = bestflare.com
DNS.1 = www.company.net
DNS.2   = usefulread.com
DNS.2 = company.com
DNS.3   = chandank.com</pre>
DNS.3 = company.net</pre>


Note: alt_names section is the one you have to change for additional DNS.  You can also use ''IP.1'' entries to insert IP addresses as SANs
Note: alt_names section is the one you have to change for additional DNS.  You can also use ''IP.1'' entries to insert IP addresses as SANs


Save the file and execute the following OpenSSL command, which will generate CSR and KEY file
Save the file and execute the following OpenSSL command, which will generate PEM and KEY file
 
openssl req -out sancert.csr -newkey rsa:2048 -nodes -keyout sancert.key -config san.cnf
 
This will create sslcert.csr and private.key in the present working directory.  Then you can turn that CSR into a certificate using this command:


  openssl x509 -req -days 365 -in sancert.csr -signkey sancert.key -sha256 -out sancert.crt
  openssl req -x509 -nodes -days 730 -newkey rsa:2048 -keyout sancert.key -out sancert.pem -config san.cnf -extensions 'v3_req'


== Converting .pem to .crt ==
== Converting .crt to .pem ==


In most cases, a simple copy or rename will suffice, but if necessary, use openssl to convert the certificate:
In most cases, a simple copy or rename will suffice, but if necessary, use openssl to convert the certificate:
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  openssl x509 -in cert.pem -text -noout
  openssl x509 -in cert.pem -text -noout
= Installing Certificates =
To avoid the "we don't like self-signed certs" issues with some applications, [[Adding a certificate to the system store|install the certificate in the OS trusted bundle.]]  Note that this does NOT work with docker, which has it's own trusted certificate store for registries.

Latest revision as of 13:03, 9 October 2021

Creating Certificates[edit]

Standard Certificates[edit]

You can do that in one command:

openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes

The -nodes option disables protecting your cert with a passphrase, otherwise it will prompt you for "at least a 4 character" password. The days parameter (365) you can replace with any number to affect expiration date. It will then prompt you for things like "Country Name" but you can just hit enter and accept defaults. Self-signed certs are not validated with any third party unless you import them to the browsers previously. If you need more security, you should use a certificate signed by a CA

Add -subj '/CN=localhost' to suppress questions about the contents of the certificate (replace localhost with your desired domain)

Creating a Cert with a SAN[edit]

Create a file named san.cnf with the following information:

[req]
distinguished_name = req_distinguished_name
x509_extensions = v3_req
prompt = no
[req_distinguished_name]
C = US
ST = VA
L = SomeCity
O = MyCompany
OU = MyDivision
CN = www.company.com
[v3_req]
keyUsage = keyEncipherment, dataEncipherment
extendedKeyUsage = serverAuth
subjectAltName = @alt_names
[alt_names]
DNS.1 = www.company.net
DNS.2 = company.com
DNS.3 = company.net

Note: alt_names section is the one you have to change for additional DNS. You can also use IP.1 entries to insert IP addresses as SANs

Save the file and execute the following OpenSSL command, which will generate PEM and KEY file

openssl req -x509 -nodes -days 730 -newkey rsa:2048 -keyout sancert.key -out sancert.pem -config san.cnf -extensions 'v3_req'

Converting .crt to .pem[edit]

In most cases, a simple copy or rename will suffice, but if necessary, use openssl to convert the certificate:

openssl x509 -in sancert.crt -out sancert.pem -outform PEM

Reading/Verifying a certificate[edit]

openssl x509 -in cert.pem -text -noout

Installing Certificates[edit]

To avoid the "we don't like self-signed certs" issues with some applications, install the certificate in the OS trusted bundle. Note that this does NOT work with docker, which has it's own trusted certificate store for registries.