`openssl x509 -in $FILE -text | less`
https://lapo.it/asn1js
https://golang.org/pkg/crypto/x509/
https://github.com/agl/certificatetransparency
GnuTLS has some useful stuff too, IIRC
`openssl x509 -in $FILE -text | less`
https://lapo.it/asn1js
https://golang.org/pkg/crypto/x509/
https://github.com/agl/certificatetransparency