Support DNS verification via AWS Route53

[natemcmaster]

Is your feature request related to a problem? Please describe.
Opening on behalf of @PaulDMendoza. In #29 (comment) he said

Add an AWS Route53 DNS option. I have a server that isn't accessible to the internet that I need to generate the certificate using DNS. But it doesn't seem to work.

This library currently only supports HTTP verification which requires the server endpoint be exposed to Let's Encrypt CA servers.

Additional context
This is also a pre-requisite for #1

[natemcmaster]

@PaulDMendoza - out of curiosity, have you looked into using https://aws.amazon.com/certificate-manager/ for your HTTPS certificate generation? If you are running your services on AWS, this may provide what you need without the overhead of Let's Encrypt. I haven't tried it myself with an ASP.NET Core app, but I happen to know the folks at AWS who work on .NET support and they may be able to help if you're running into issues.

[PaulDMendoza]

Actually, don't worry about this. I ended up just buying an SSL cert from Namecheap for $7 for this backend server. Seems to work fine now. I use certificate manager for my public facing stuff with API Gateway. But private API Gateway endpoints are accessible with the Client VPN it seems and I don't want to extra pay for the ELB. So I just opted to use an EC2 instance where I public my ASP.NET Core app to and run Kestrel web server.

…

On Mon, Feb 17, 2020 at 8:51 PM Nate McMaster ***@***.***> wrote: @PaulDMendoza <https://github.com/PaulDMendoza> - out of curiosity, have you looked into using https://aws.amazon.com/certificate-manager/ for your HTTPS certificate generation? If you are running your services on AWS, this may provide what you need without the overhead of Let's Encrypt. I haven't tried it myself with an ASP.NET Core app, but I happen to know the folks at AWS who work on .NET support and they may be able to help if you're running into issues. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#51>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAH53MZLDPS72B735BTKAQDRDNSN3ANCNFSM4KW47QYQ> .

-- *Paul Mendoza* *C: (760) 917-3753* *mendoza.paul@gmail.com <mendoza.paul@gmail.com>*

[natemcmaster]

Ok, thanks for the additional info.