purpose of xp extensions

[d tbsky]

2018-06-29 18:51 GMT+08:00 Matthew Newton <mcn at freeradius.org>:
> On Fri, 2018-06-29 at 16:08 +0800, d tbsky wrote:
>> Hmmm. I tried to use let's encrypt certificate, and windows 7 seems
>> to swallow it.
>
> Let's Encrypt certs include the TLS Web Server Auth EKU, as do all
> commercial certs used for web servers.
>
>> BTW, how can we check if the certificate comes with xp extensions or
>> not?
>> I tried to use "openssl x509 -text -in my.crt", but can not find info
>> about the extension.
>
> in
>
>   X509v3 extensions:
>
> look for
>
>     X509v3 Extended Key Usage:
>       TLS Web Server Authentication, TLS Web Client Authentication

thanks for the hint. but many certificates all have these kind of
info. that's really confuse me.