Does this work with initial certificate setup and `sniproxy`?

[ntninja]

Hi! I just spent some time trying set up this software behind an sniproxy-based reverse protocol with enabled “proxy_protocol” support, but I couldn't get it to work. When using the ALPN challenge I get:

test_caddy | Activating privacy features... 2019/01/26 20:44:19 [INFO] acme: Registering account for alexander-tls-test@ninetailed.ninja
test_caddy | 2019/01/26 20:44:19 [INFO] [test.ninetailed.ninja] acme: Obtaining bundled SAN certificate
test_caddy | 2019/01/26 20:44:19 [INFO] [test.ninetailed.ninja] AuthURL: https://acme-staging-v02.api.letsencrypt.org/acme/authz/cFVMAoxTSk4JwTN2D0-MVhYXB0sVmOQdg6LSUNsgz78
test_caddy | 2019/01/26 20:44:19 [INFO] [test.ninetailed.ninja] acme: use tls-alpn-01 solver
test_caddy | 2019/01/26 20:44:19 [INFO] [test.ninetailed.ninja] acme: Trying to solve TLS-ALPN-01
test_caddy | 2019/01/26 20:44:21 http: TLS handshake error from 172.18.0.5:44350: tls: oversized record received with length 22617
test_caddy | 2019/01/26 20:44:21 http: TLS handshake error from 172.18.0.5:44354: tls: oversized record received with length 22617
test_caddy | 2019/01/26 20:44:21 http: TLS handshake error from 172.18.0.5:44358: tls: oversized record received with length 22617
test_caddy | 2019/01/26 20:44:21 http: TLS handshake error from 172.18.0.5:44362: tls: oversized record received with length 22617
test_caddy | 2019/01/26 20:44:21 http: TLS handshake error from 172.18.0.5:44364: tls: oversized record received with length 22617
test_caddy | 2019/01/26 20:44:21 http: TLS handshake error from 172.18.0.5:44366: tls: oversized record received with length 22617
test_caddy | 2019/01/26 20:44:21 http: TLS handshake error from 172.18.0.5:44368: tls: oversized record received with length 22617
test_caddy | 2019/01/26 20:44:21 http: TLS handshake error from 172.18.0.5:44370: tls: oversized record received with length 22617
test_caddy | 2019/01/26 20:44:26 [test.ninetailed.ninja] failed to obtain certificate: acme: Error -> One or more domains had a problem:
test_caddy | [test.ninetailed.ninja] acme: error: 400 :: urn:ietf:params:acme:error:tls :: remote error: tls: record overflow, url: 
test_caddy | exit status 1
test_caddy exited with code 1

When disabling TLS-ALPN-01 and using HTTP-01 instead, I get:

test_caddy | Activating privacy features... 2019/01/26 20:47:30 [INFO] [test.ninetailed.ninja] acme: Obtaining bundled SAN certificate
test_caddy | 2019/01/26 20:47:31 [INFO] [test.ninetailed.ninja] AuthURL: https://acme-staging-v02.api.letsencrypt.org/acme/authz/pSEq4OKVS8Rq_4Qvr_2DBRWW8izqUI0wkM1OXIkVhXU
test_caddy | 2019/01/26 20:47:31 [INFO] [test.ninetailed.ninja] acme: Could not find solver for: tls-alpn-01
test_caddy | 2019/01/26 20:47:31 [INFO] [test.ninetailed.ninja] acme: use http-01 solver
test_caddy | 2019/01/26 20:47:31 [INFO] [test.ninetailed.ninja] acme: Trying to solve HTTP-01
test_caddy | 2019/01/26 20:47:37 [test.ninetailed.ninja] failed to obtain certificate: acme: Error -> One or more domains had a problem:
test_caddy | [test.ninetailed.ninja] acme: error: 403 :: urn:ietf:params:acme:error:unauthorized :: Invalid response from http://test.ninetailed.ninja/.well-known/acme-challenge/XyPxxbLYHFOe8R_FySSwLJ2daCY1sa6epb71Yvdf39w [2001:1608:39::a]: 400, url: 
test_caddy | exit status 1
test_caddy exited with code 1

Both of these work however, when disabling the PROXY protocol in both Caddy (this plugin) and sniproxy (the proxy_protocol flag). I can also attest that sniproxy's PROXY protocol implementation works without issues when used with nginx.

When getting a cert without using the PROXY protocol (ie: disable this plugin), I'm also not able to view HTTPS content when enabling it afterwards (but HTTP work although it will receive the PROXY headers as well):

test_caddy | Activating privacy features... 2019/01/26 20:53:35 [INFO][test.ninetailed.ninja] Obtain: Certificate already exists in storage
test_caddy | done.
test_caddy | https://test.ninetailed.ninja
test_caddy | http://test.ninetailed.ninja
test_caddy | 2019/01/26 20:53:35 https://test.ninetailed.ninja
test_caddy | 2019/01/26 20:53:35 http://test.ninetailed.ninja
test_caddy | 2019/01/26 20:53:35 [NOTICE] Sending telemetry: we were too early; waiting 1h1m45.482846269s before trying again
test_caddy | 2019/01/26 20:53:58 http: TLS handshake error from 172.18.0.5:39472: invalid source address
test_caddy | 2019/01/26 20:54:01 http: TLS handshake error from 172.18.0.5:39498: invalid source address

In each case the Caddyfile was just:

test.ninetailed.ninja
proxyprotocol

And the sniproxy config was:

listener [::]:80 {
    protocol http
}

listener [::]:443 {
    protocol tls
}

table {
    # some other rules

    test.ninetailed.ninja test_caddy proxy_protocol

    # some other rules
}

(where test_caddy is the name of the Caddy server container).

Do maybe have some insights into this by any chance?