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Linux & Terminal

OpenSSL Certificates

Inspect PEM certs, CSRs, and keys, convert formats, verify chains, and probe live TLS

31 entries7 sectionsCopy an entry or print the full reference.
A certificate, wax seal, brass key, and linked certificate cards.

31 entries · Use the copy icon.

All cheatsheets
On this pageEntries
Inspect PEM6Keys6Create certs4Convert5Verify5Live TLS4Sources1

1Inspect PEM

6 entries
Inspect PEM: syntax and descriptions
SyntaxDescription
openssl x509 -in cert.pem -text -noout
Print a certificate
openssl x509 -in cert.pem -noout -subject -issuer -dates
Subject, issuer, and dates
openssl x509 -in cert.pem -noout -ext subjectAltName
Print SAN
openssl x509 -in cert.pem -noout -fingerprint -sha256
SHA-256 fingerprint
openssl req -in csr.pem -text -noout
Print a CSR
openssl crl -in crl.pem -text -noout
Print a CRL

2Keys

6 entries
Keys: syntax and descriptions
SyntaxDescription
openssl pkey -in key.pem -text -noout
Inspect a private key (prints material)
openssl pkey -in key.pem -pubout
Write the public key
openssl pkey -in key.pem -check
Check key consistency
openssl genpkey -algorithm RSA -out key.pem -pkeyopt rsa_keygen_bits:2048
Generate an RSA key
openssl genpkey -algorithm ED25519 -out key.pem
Generate an Ed25519 key
openssl rsa -in key.pem -pubout
RSA public key from an RSA key file

3Create certs

4 entries
Create certs: syntax and descriptions
SyntaxDescription
openssl req -new -key key.pem -out req.csr
Create a CSR
openssl req -new -x509 -key key.pem -out cert.pem -days 365
Self-signed certificate
openssl x509 -req -in req.csr -signkey key.pem -out cert.pem -days 90
Sign a CSR with a key
openssl req -new -x509 -nodes -newkey rsa:2048 -keyout key.pem -out cert.pem -days 30 -subj "/CN=localhost"
One-shot local cert and key

4Convert

5 entries
Convert: syntax and descriptions
SyntaxDescription
openssl x509 -in cert.der -inform DER -out cert.pem
DER cert to PEM
openssl x509 -in cert.pem -outform DER -out cert.der
PEM cert to DER
openssl pkcs12 -in bundle.p12 -nodes -out bundle.pem
PKCS#12 to PEM
openssl pkcs12 -export -in cert.pem -inkey key.pem -out bundle.p12
PEM cert and key to PKCS#12
openssl x509 -in cert.pem -noout -pubkey
Extract the cert public key

5Verify

5 entries
Verify: syntax and descriptions
SyntaxDescription
openssl verify -CAfile ca.pem cert.pem
Verify a cert against a CA file
openssl verify -untrusted chain.pem -CAfile root.pem leaf.pem
Verify with intermediates
openssl x509 -in cert.pem -noout -checkend 86400
Fail if cert ends within 1 day
openssl ocsp -issuer ca.pem -cert cert.pem -url http://ocsp.example/
Query OCSP for a cert
diff <(openssl x509 -in a.pem -noout -modulus) <(openssl pkey -in key.pem -noout -modulus)
Check cert and key modulus match

6Live TLS

4 entries
Live TLS: syntax and descriptions
SyntaxDescription
openssl s_client -connect host:443 -servername host
Open a TLS session
openssl s_client -connect host:443 -servername host </dev/null | openssl x509 -noout -text
Show the presented cert
openssl s_client -connect host:443 -showcerts
Print the cert chain
echo | openssl s_client -connect host:443 2>/dev/null | openssl x509 -noout -dates
Print live notBefore/notAfter

7Sources

1 entries
Sources: syntax and descriptions
SyntaxDescription
https://docs.openssl.org/3.6/man1/openssl/
OpenSSL 3.6 command index: certificate, key, verification, and TLS commands.

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