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 -sha256 -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
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
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.
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 md5Check an SSL connection. All the certificates (including Intermediates) should be displayed
openssl s_client -connect <server>:<port>
Just checking date, use this:
curl -vk https://<server>
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 PEM to CRT (.CRT file)
openssl x509 -outform der -in certificate.pem -out certificate.crt
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 verify that an RSA private key matches the RSA public key in a certificate you need to i) verify the consistency of the private key and ii) compare the modulus of the public key in the certificate against the modulus of the private key.
To verify the consistency of the RSA private key and to view its modulus:
openssl rsa -check -noout -modulus -in myserver.key
To view the modulus of the RSA public key in a certificate:
openssl x509 -noout -modulus -in myserver.crt
via a single line with a short modulus use this:
openssl x509 -noout -modulus -in server.pem | openssl md5 ;\
openssl rsa -noout -modulus -in server.key | openssl md5Public key must be in .pem format, not openssl format beginning with id-rsa ...
Keys can be generated with this, there are many ways:
ssh-keygen -t rsa -b 4096 -C "email@domain.com" -f ~/.ssh/id_rsa
Yes use a passphrase, not a password, except in rare cases, then
save the key in .pem format, this will require the passphrase
created above
openssl rsa -in ~/.ssh/id_rsa -pubout -out ~/.ssh/id_rsa.pub.pem
encrypt small files like this:
openssl rsautl -encrypt -inkey id_rsa.pub.pem -pubin -in file.txt -out file.txt.enc
decrypt files like this:
openssl rsautl -decrypt -inkey ~/.ssh/id_rsa -in file.txt.enc -out file.txt
If you need to encrypt file larger than the key size -11 bits, so 4096 - 11 = 4085
or if someone sends you a small key check with this:
openssl rsa -in id_rsa.pub.pem -pubin -text -noout
then you can generate a random key with this:
openssl rand -base64 128 -out random.key
and then use the smaller key to encrypt that random.key
openssl rsautl -encrypt -inkey id_rsa.pub.pem -pubin -in random.key -out random.key.enc
and use the larger random.key to encrypt the file:
openssl enc -aes-256-cbc -salt -in bigfile -out bigfile.enc -pass file:./random.key
Send the encrypted bigfile.enc and the encrypted random.key.enc
Decrypt the random.key.enc file like this:
openssl rsautl -decrypt -inkey ~/.ssh/id_rsa -in random.key.enc -out random.key
and the bigfile.enc like this:
openssl enc -d -aes-256-cbc -in bigfile.enc -out bigfile -pass file:./random.key