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Read all domains of a certificate (SAN)

harmlessSSL and certificatesalle
Adjust the values, the command updates live
user@server
openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -ext subjectAltName

Fetches the certificate from the server and prints the subjectAltName extension, for example DNS:example.com, DNS:www.example.com. Browsers only check this list now, not the common name. If a variant such as www or a subdomain is missing, the browser shows a certificate warning.

Note: The -ext option requires OpenSSL 1.1.1 or newer. On older systems use -text and look for Subject Alternative Name.

Also searched as

  • which domains does an ssl certificate cover
  • show subject alternative names openssl
  • certificate not valid for www
  • NET::ERR_CERT_COMMON_NAME_INVALID

Related one-liners

All in SSL and certificates

Check the SSL certificate expiration date of a website

$openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -dates
harmlessSSL and certificates

Check whether a certificate expires within the next days

#openssl x509 -in /etc/letsencrypt/live/example.com/cert.pem -noout -checkend $(( 30 * 86400 )) && echo "noch gültig" || echo "läuft bald ab"
harmlessSSL and certificates

Check whether a private key matches a certificate

#openssl x509 -noout -modulus -in /etc/ssl/certs/example.com.crt | openssl md5 && openssl rsa -noout -modulus -in /etc/ssl/private/example.com.key | openssl md5
harmlessSSL and certificates

Check whether a website's certificate is trusted

$openssl s_client -connect example.com:443 -servername example.com -verify_hostname example.com </dev/null 2>/dev/null | grep "Verify return code"
harmlessSSL and certificates

Create a self-signed certificate for testing

$openssl req -x509 -newkey rsa:2048 -nodes -days 365 -keyout test.key -out test.crt -subj "/CN=test.example.com" -addext "subjectAltName=DNS:test.example.com"
cautionSSL and certificates

Generate a private key and CSR for multiple domains

$openssl req -new -newkey rsa:2048 -nodes -keyout example.com.key -out example.com.csr -subj "/CN=example.com" -addext "subjectAltName=DNS:example.com,DNS:www.example.com"
cautionSSL and certificates

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