John Siu Blog

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DOMAIN=<domain>
openssl s_client -connect $DOMAIN:443 -showcerts </dev/null | openssl x509 -outform pem > $DOMAIN.pem

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openssl x509 -in <file> -noout -text
openssl x509 -in domain.pem -noout -text

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openssl x509 -in <file> -noout -ext subjectAltName
openssl x509 -in <file> -noout -ext keyUsage

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openssl x509 -in <file> -noout -issuer

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openssl x509 -in <file> -noout -serial

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openssl x509 -in <file> -noout -subject

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openssl x509 -in <file> -noout -fingerprint
openssl x509 -in <file> -noout -fingerprint -md5
openssl x509 -in <file> -noout -fingerprint -sha1
openssl x509 -in <file> -noout -fingerprint -sha256