ejabberd ACME unexpected content type when it receives certificate

[lukewarms]

Hi,
Thought i would get some opinion if this may be a bug.
I am running a processone/ejabberd container that i am trying to get to request a certificate via ACME to a smallstep ca container. The request fails with this error:

           #{<<"kid">> =>
                                <<"https://ca.mydomain.local:8000/acme/acme/account/svUkT7QwXD4pBqyrVdys94VMeVCeeo0D">>,
                            <<"nonce">> =>
                                <<"..">>,
                            <<"url">> =>
                                <<"https://ca.mydomain.local:8000/acme/acme/certificate/Jks2zJjdJwqDzE7VSsLM0TOaAzzYUB2P">>}}
2022-11-07 08:30:28.355858+00:00 [debug] HTTP request: {post,{"https://ca.mydomain.local:8000/acme/acme/certificate/Jks2zJjdJwqDzE7VSsLM0TOaAzzYUB2P",
                     [],"application/jose+json",
                     <<"{\"signature\":\"....\",\"protected\":\"......\",\"payload\":\"\"}">>}}
2022-11-07 08:30:28.608072+00:00 [debug] HTTP response: {{"HTTP/1.1",200,"OK"},
                [{"cache-control","no-store"},
                 {"date","Mon, 07 Nov 2022 08:30:28 GMT"},
                 {"content-length","2108"},
                 {"content-type",
                  "application/pem-certificate-chain; charset=utf-8"},
                 {"link",
                  "<https://ca.mydomain.local:8000/acme/acme/directory>;rel=\"index\""},
                 {"replay-nonce",
                  ".."}],
                <<"-----BEGIN CERTIFICATE-----........\n-----END CERTIFICATE-----\n-----BEGIN CERTIFICATE-----........\n-----END CERTIFICATE-----\n">>}
2022-11-07 08:30:28.609162+00:00 [error] Failed to request certificate for jabber-gw.mydomain.me: HTTP error: unexpected content type: application/pem-certificate-chain; charset=utf-8
2022-11-07 08:30:28.609456+00:00 [debug] Unregistering ACME challenge #Ref<0.1802325958.1657798659.124306>
2022-11-07 08:35:26.914567+00:00 [debug] Error when retrieving http headers gen_tcp: timeout 

It's seems as if ejabberd wasn't expecting the cert?!?

Prior to the error, logs show the ACME challenge looking healthy where the content type is application/json:

                      ```

<<"https://ca.mydomain.local:8000/acme/acme/order/IKXRHjiqqRhSjlvSUExtaZjI89swHOYV">>}}
2022-11-07 08:30:27.007780+00:00 [debug] HTTP request: {post,{"https://ca.mydomain.local:8000/acme/acme/order/IKXRHjiqqRhSjlvSUExtaZjI89swHOYV",
[],"application/jose+json",
<<"{"signature":"_...","payload":""}">>}}
2022-11-07 08:30:27.428351+00:00 [debug] HTTP response: {{"HTTP/1.1",200,"OK"},
[{"cache-control","no-store"},
{"date","Mon, 07 Nov 2022 08:30:27 GMT"},
{"location",
"https://ca.mydomain.local:8000/acme/acme/order/IKXRHjiqqRhSjlvSUExtaZjI89swHOYV"},
{"content-length","424"},
{"content-type","application/json"},
{"link",
"https://ca.mydomain.local:8000/acme/acme/directory;rel="index""},
{"replay-nonce",
"..."}],

Any thoughts?

[hslatman]

I have found the cause and potential fixes and written about them in the issue: #3938 (comment).