I'm installing OpenVPN Access Server on a Google Cloud instance. Its webUI listens on port 943 using https. It has a self-signed certificate whose name doesn't match the server's hostname (10.150.0.2). I can't start an SSH tunnel. I'm looking for a way to troubleshoot the connection from the IAP service to my server.
The command I'm running is gcloud compute start-iap-tunnel vpn 943 --local-host-port=localhost:943 I receive the normal Testing if tunnel connection works message.
It errs out with ERROR: (gcloud.compute.start-iap-tunnel) While checking if a connection can be made: Error while connecting [4003: 'failed to connect to backend']. (Failed to connect to port 943)
If I add --log-http to the command invocation the relevant information follows (it looks like a normal req/resp cycle with a 200 that I assume is from my client to the IAP service):
Testing if tunnel connection works.
=======================
==== request start ====
uri: https://oauth2.googleapis.com/token
method: POST
== headers start ==
b'content-type': b'application/x-www-form-urlencoded'
b'user-agent': b'google-cloud-sdk gcloud/367.0.0 command/gcloud.compute.start-iap-tunnel invocation-id/db27de82264f47fcb63f6680afaa8327 environment/None environment-version/None interactive/False from-script/False python/3.7.9 term/xterm-256color (Macintosh; Intel Mac OS X 21.2.0)'
== headers end ==
== body start ==
Body redacted: Contains oauth token. Set log_http_redact_token property to false to print the body of this request.
== body end ==
==== request end ====
---- response start ----
status: 200
-- headers start --
Alt-Svc: h3=":443"; ma=2592000,h3-29=":443"; ma=2592000,h3-Q050=":443"; ma=2592000,h3-Q046=":443"; ma=2592000,h3-Q043=":443"; ma=2592000,quic=":443"; ma=2592000; v="46,43"
Cache-Control: no-cache, no-store, max-age=0, must-revalidate
Content-Encoding: gzip
Content-Type: application/json; charset=utf-8
Date: Fri, 24 Dec 2021 02:11:52 GMT
Expires: Mon, 01 Jan 1990 00:00:00 GMT
Pragma: no-cache
Server: scaffolding on HTTPServer2
Transfer-Encoding: chunked
Vary: Origin, X-Origin, Referer
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 0
-- headers end --
-- body start --
Body redacted: Contains oauth token. Set log_http_redact_token property to false to print the body of this response.
-- body end --
total round trip time (request+response): 0.246 secs
---- response end ----
----------------------
ERROR: (gcloud.compute.start-iap-tunnel) While checking if a connection can be made: Error while connecting [4003: 'failed to connect to backend']. (Failed to connect to port 943)
To my knowledge this is the limit of easily accessible troubleshooting for start-tap-tunnel.
Moving on to the local machine we can connect to 10.150.0.2:943 before puking a la certificate.
root@viongier:/usr/local/openvpn_as# wget https://10.150.0.2:943
--2021-12-24 02:01:47-- https://10.150.0.2:943/
Connecting to 10.150.0.2:943... connected.
ERROR: The certificate of ‘10.150.0.2’ is not trusted.
ERROR: The certificate of ‘10.150.0.2’ doesn't have a known issuer.
The certificate's owner does not match hostname ‘10.150.0.2’
It seems to me that my client happily connects to the IAP service which fails to connect to my server. I would expect to see an IAP error if it was erring out because of the cert. The only thing I can think of to test this is by generating a certificate whose issuer google likes. (LetsEncrypt for example.)
