Here is a running list of useful OpenSSL Commands
Private Keys: Working with RSA and ECDSA keys
In the commands below, replace [bits] with the key size
(For example, 2048, 4096, 8192).
# Generate an RSA key:
openssl genrsa -out example.key [bits]
# Print public key or modulus only:
openssl rsa -in example.key -pubout
openssl rsa -in example.key -noout -modulus
# Print textual representation of RSA key:
openssl rsa -in example.key -text -noout
# Generate new RSA key and encrypt with a pass phrase based on AES CBC 256 encryption:
openssl genrsa -aes256 -out example.key [bits]
# Check your private key. If the key has a pass phrase, you’ll be prompted for it:
openssl rsa -check -in example.key
# Remove passphrase from the key:
openssl rsa -in example.key -out example.key
# Encrypt existing private key with a pass phrase:
openssl rsa -des3 -in example.key -out example_with_pass.key
# Generate ECDSA key. curve is to be replaced with:
# prime256v1, secp384r1, secp521r1, or any other supported elliptic curve:
openssl ecparam -genkey -name [curve] | openssl ec -out example.ec.key
# Print ECDSA key textual representation:
openssl ec -in example.ec.key -text -noout
#List available EC curves, that OpenSSL library supports:
openssl ecparam -list_curves
# Generate DH params with a given length:
openssl dhparam -out dhparams.pem [bits]
Create certificate signing requests (CSR)
In the commands below, replace [digest] with the name of the supported hash function:
md5, sha1, sha224, sha256, sha384 or sha512, etc.
It’s better to avoid weak functions like md5 and sha1, and stick to sha256
and above.
# Create a CSR from existing private key.
openssl req -new -key example.key -out example.csr -[digest]
# Create a CSR and a private key without a pass phrase in a single command:
openssl req -nodes -newkey rsa:[bits] -keyout example.key -out example.csr
# Provide CSR subject info on a command line, rather than through interactive prompt.
openssl req -nodes
-newkey rsa:[bits]
-keyout example.key
-out example.csr
-subj "/C=UA/ST=Kharkov/L=Kharkov/O=Super Secure Company/OU=IT Department/CN=example.com"
# Create a CSR from existing certificate and private key:
openssl x509 -x509toreq -in cert.pem -out example.csr -signkey example.key
# Generate a CSR for multi-domain SAN certificate by supplying an openssl config file:
openssl req -new -key example.key -out example.csr -config req.conf
where req.conf:
# req.conf
[req]prompt=nodefault_md = sha256distinguished_name = dnreq_extensions = req_ext
[dn]CN=example.com
[req_ext]subjectAltName=@alt_names
[alt_names]DNS.1=example.comDNS.2=www.example.comDNS.3=ftp.example.com
Certificates: Create X.509 certificates
# Create self-signed certificate and new private key from scratch:
openssl req -nodes
-newkey rsa:2048
-keyout example.key
-out example.crt -x509
-days 365
# Create a self signed certificate using existing CSR and private key:
openssl x509 -req
-in example.csr
-signkey example.key
-out example.crt
-days 365
# Sign child certificate using your own “CA” certificate and it’s private key.
# If you were a CA company, this shows a very naive example of how you could issue new certificates.
openssl x509 -req
-in child.csr
-days 365
-CA ca.crt
-CAkey ca.key
-set_serial 01
-out child.crt
# Print textual representation of the certificate
openssl x509 -in example.crt -text -noout
# Print certificate’s fingerprint as md5, sha1, sha256 digest:
openssl x509 -in cert.pem -fingerprint -sha256 -noout
Verify a CSR signature:
openssl req -in example.csr -verify
# Verify that private key matches a certificate and CSR:
openssl rsa -noout -modulus -in example.key | openssl sha256
openssl x509 -noout -modulus -in example.crt | openssl sha256
openssl req -noout -modulus -in example.csr | openssl sha256
# Verify certificate, provided that you have root and any intemediate
# certificates configured as trusted on your machine:
openssl verify example.crt
# Verify certificate, when you have intermediate certificate chain.
# Root certificate is not a part of bundle, and should be configured as a
# trusted on your machine.
openssl verify -untrusted intermediate-ca-chain.pem example.crt
# Verify certificate, when you have intermediate certificate chain
# and root certificate, that is not configured as a trusted one.
openssl verify -CAFile root.crt -untrusted intermediate-ca-chain.pem child.crt
# Verify that certificate served by a remote server covers given host name.
# Useful to check your mutlidomain certificate properly covers all the host names.
openssl s_client -verify_hostname www.example.com -connect example.com:443
Calculate message digests and base64 encoding
# Calculate md5, sha1, sha256, sha384, sha512 digests:
openssl dgst -[hash_function] <input.file
cat input.file | openssl [hash_function]
# Base64 encoding and decoding:
cat /dev/urandom | head -c 50 | openssl base64 | openssl base64 -d
Using TLS client (openssl s_client) to test TLS on a remote server
# Connect to a server supporting TLS:
openssl s_client -connect example.com:443
openssl s_client -host example.com -port 443
# Connect to a server and show full certificate chain:
openssl s_client -showcerts -host example.com -port 443 </dev/null
# Extract the certificate:
openssl s_client -connect example.com:443 2>&1 < /dev/null | sed -n '/-----BEGIN/,/-----END/p' > certificate.pem
# Override SNI (Server Name Indication) extension with another server name. Useful for testing when multiple secure sites are hosted on same IP address:
openssl s_client -servername www.example.com -host example.com -port 443
Check Certificate on remote server
Get all information:
# Extract the all information from the SSL certificate (decoded):
echo | openssl s_client
-servername www.example.com
-connect www.example.com:443
2>/dev/null | openssl x509 -noout -text
Certificate:
Data:
Version: 3 (0x2)
Serial Number:
03:86:f4:63:3d:34:50:a8:47:cc:f7:99:10:1f:79:1c:21:c8
Signature Algorithm: sha256WithRSAEncryption
[...]
# Show the SSL certificate itself (encoded):
$ echo | openssl s_client
-servername example.com
-connect example.com:443
2>/dev/null | openssl x509
-----BEGIN CERTIFICATE-----
MIIFGDCCBACgAwIBAgISA4b0Yz00UKhHzPeZEB95HCHIMA0GCSqGSIb3DQEBCwUA
MEoxCzAJBgNVBAYTAlVTMRYwFAYDVQQKEw1MZXQncyBFbmNyeXB0MSMwIQYDVQQD
ExpMZXQncyBFbmNyeXB0IEF1dGhvcml0eSBYMzAeFw0xNzAzMTgxMDU1MDBaFw0x
[...]
Get specific information back:
# Check SSL Certificate Expiration Date
echo | openssl s_client
-servername www.example.com
-connect www.example.com:443
2>/dev/null | openssl x509 -noout -dates
notBefore=Mar 18 10:55:00 2017 GMT
notAfter=Jun 16 10:55:00 2017 GMT
# OpenSSL: Check SSL Certificate – Additional Information:
# issuer, issued to, validity
$ echo | openssl s_client
-servername shellhacks.com
-connect shellhacks.com:443
2>/dev/null | openssl x509 -noout -issuer -subject -dates
issuer= /C=US/O=Let's Encrypt/CN=Let's Encrypt Authority X3
subject= /CN=www.shellhacks.com
notBefore=Mar 18 10:55:00 2017 GMT
notAfter=Jun 16 10:55:00 2017 GMT
# Show the SHA1 fingerprint of the SSL certificate:
$ echo | openssl s_client
-servername www.example.com
-connect www.shellhacks.com:443
2>/dev/null | openssl x509 -noout -fingerprint
SHA1 Fingerprint=26:F8:D5:E4:3E:7A:7B:7E:72:20:15:77:FE:C7:89:E7:E4:8A:15:CF
Verify if the particular cipher is accepted on URL
If you are working on security findings and pen test results show some of the
weak ciphers is accepted then to validate, you can use the above command.
Of course, you will have to change the cipher and URL, which you want to test against.
If the mentioned cipher is accepted, then you will get “CONNECTED” else “handshake failure”.
# Test TLS connection by forcibly using specific cipher suite,
# e.g. ECDHE-RSA-AES128-GCM-SHA256. Useful to check if a server can
# properly talk via different configured cipher suites, not one it prefers.
openssl s_client
-host example.com
-port 443
-cipher ECDHE-RSA-AES128-GCM-SHA256
2>&1 </dev/null
Check if SSL V2 or V3 is accepted on URL
# Check SSL V2
openssl s_client -connect secureurl.com:443 -ssl2
# Check SSL V3
openssl s_client -connect secureurl.com:443 –ssl3
# Check TLS 1.0
openssl s_client -connect secureurl.com:443 –tls1
# Check TLS 1.1
openssl s_client -connect secureurl.com:443 –tls1_1
# Check TLS 1.2
openssl s_client -connect secureurl.com:443 –tls1_2
# Check SSL V2/V3
# If you are securing web server and need to validate if SSL V2/V3 is enabled or not,
# you can use the above command. If activated, you will get “CONNECTED” else “handshake failure.”
Check Certificate Expiration Date of SSL URL
# Useful if you are planning to monitor SSL cert expiration date remotely or particular URL.
openssl s_client -connect secureurl.com:443 2>/dev/null | openssl x509 -noout –enddate
##
## Measure TLS connection and handshake time
```bash
# Measure SSL connection time without/with session reuse:
openssl s_time -connect example.com:443 -new
openssl s_time -connect example.com:443 -reuse
# Roughly examine TCP and SSL handshake times using curl:
curl -kso /dev/null -w "tcp:%{time_connect}, ssldone:%{time_appconnect}n" https://example.com
# Measure speed of various security algorithms:
openssl speed rsa2048
openssl speed ecdsap256
Convert between encoding and container formats
# Convert certificate between DER and PEM formats:
openssl x509 -in example.pem -outform der -out example.der
openssl x509 -in example.der -inform der -out example.pem
# Combine several certificates in PKCS7 (P7B) file:
openssl crl2pkcs7 -nocrl -certfile child.crt -certfile ca.crt -out example.p7b
# Convert from PKCS7 back to PEM. If PKCS7 file has multiple certificates,
# the PEM file will contain all of the items in it.
openssl pkcs7 -in example.p7b -print_certs -out example.crt
# Combine a PEM certificate file and a private key to PKCS#12 (.pfx .p12).
# Also, you can add a chain of certificates to PKCS12 file.
openssl pkcs12
-export
-out certificate.pfx
-inkey privkey.pem
-in certificate.pem
-certfile ca-chain.pem
# Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates
# back to PEM:
openssl pkcs12 -in keystore.pfx -out keystore.pem -nodes
List cipher suites
# List available TLS cipher suites, openssl client is capable of:
openssl ciphers -v
# Enumerate all individual cipher suites, which are described by a short-hand
# OpenSSL cipher list string. This is useful when you’re configuring server
# like Nginx, and you need to test your ssl_ciphers string.
openssl ciphers -v 'EECDH+ECDSA+AESGCM:EECDH+aRSA+SHA256:EECDH:DHE+AESGCM:DHE:!RSA!aNULL:!eNULL:!LOW:!RC4'
Manually check certificate revocation status from OCSP responder
This is a multi-step process:
- Retrieve the certificate from a remote server
- Obtain the intermediate CA certificate chain
- Read OCSP endpoint URI from the certificate
- Request a remote OCSP responder for certificate revocation status
# First, retrieve the certificate from a remote server:
openssl s_client -connect example.com:443
2>&1 < /dev/null | sed -n '/-----BEGIN/,/-----END/p' > cert.pem
# You’d also need to obtain intermediate CA certificate chain.
# Use -showcerts flag to show full certificate chain, and manually save all
# intermediate certificates to chain.pem file:
openssl s_client -showcerts -host example.com -port 443 </dev/null
# Read OCSP endpoint URI from the certificate:
openssl x509 -in cert.pem -noout -ocsp_uri
# Request a remote OCSP responder for certificate revocation status using the URI
# from the above step (e.g. http://ocsp.stg-int-x1.letsencrypt.org).
openssl ocsp -header "Host" "ocsp.stg-int-x1.letsencrypt.org"
-issuer chain.pem
-VAfile chain.pem
-cert cert.pem
-text
-url http://ocsp.stg-int-x1.letsencrypt.org
Display and verify Certificate Information
# 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
# Likewise, you can display the contents of a DER formatted certificate:
openssl x509 -in MYCERT.der -inform der -text
# Check Expiry Date
openssl x509 -enddate -noout -in file.pem
Check Private key, certificate and CSR match
To verify the consistency we need to view the modulus value:
# We should have a match comparing myserver.key, myserver.crt and CSR.csr
openssl x509 -noout -modulus -in fullchain.pem | openssl md5;
openssl rsa -noout -modulus -in privkey.pem | openssl md5
openssl req -noout -modulus -in CSR.csr | openssl md5
(stdin)= 138efb8eb453fc9e5098ee81fd441e0a
(stdin)= 138efb8eb453fc9e5098ee81fd441e0a
(stdin)= 138efb8eb453fc9e5098ee81fd441e0a
Convert a PEM Certificate to PFX/P12 format for web browser Client certificate
openssl pkcs12 -export -out nginx-repo.p12 -in nginx-repo.crt -inkey nginx-repo.key -passin pass:root -passout pass:root