x-forwarded-proto header generates a non standard URL

[jgrocha]

Context

I have MapProxy running behind Apache and my own proxy written in node.

app.use('/', createProxyMiddleware({
  changeOrigin: true,
  secure: false,
  router: (req) => {
    let novo = new URL(req.url.replace(/^\//, ''));
    return novo.origin;
  },
  pathRewrite: (path, req) => {
    let novo = new URL(path.replace(/^\//, ''));
    let res = novo.pathname + novo.search;
    return res;
  },
}));

The proxy adds the header 'x-forwarded-proto': 'https' to the request, which should be ok.

Actual Behavior

Width such 'x-forwarded-proto': 'https' header, the Capabilities gets the URL malformed, as we can see in the example.

<ows:HTTP>
<ows:Get xlink:href="https, https://xxx.ambiente.azores.gov.pt/mapproxy/service?">
<ows:Constraint name="GetEncoding">
<ows:AllowedValues>
<ows:Value>KVP</ows:Value>
</ows:AllowedValues>
</ows:Constraint>
</ows:Get>
</ows:HTTP>

Possible Fix

Since I control the proxy, the work around is to remove the header from the request.

app.use('/', createProxyMiddleware({
  changeOrigin: true,
  secure: false,
  router: (req) => {
    let novo = new URL(req.url.replace(/^\//, ''));
    return novo.origin;
  },
  pathRewrite: (path, req) => {
    delete req.headers['x-forwarded-proto'];

    let novo = new URL(path.replace(/^\//, ''));
    let res = novo.pathname + novo.search;
    return res;
  },
}));

The header should only determine with the usage of http or https, but it changes completely the URL.

Other headers sent

9|proxy  | {
9|proxy  |   host: 'xxx.ambiente.azores.gov.pt',
9|proxy  |   'user-agent': 'Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0',
9|proxy  |   accept: 'text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8',
9|proxy  |   'accept-language': 'pt,pt-BR;q=0.8,en-US;q=0.5,en;q=0.3',
9|proxy  |   'accept-encoding': 'gzip, deflate, br',
9|proxy  |   cookie: '...',
9|proxy  |   'upgrade-insecure-requests': '1',
9|proxy  |   'sec-fetch-dest': 'document',
9|proxy  |   'sec-fetch-mode': 'navigate',
9|proxy  |   'sec-fetch-site': 'none',
9|proxy  |   'sec-fetch-user': '?1',
9|proxy  |   'sec-gpc': '1',
9|proxy  |   pragma: 'no-cache',
9|proxy  |   'cache-control': 'no-cache',
9|proxy  |   'x-forwarded-for': '94.61.164.170',
9|proxy  |   'x-forwarded-proto': 'https',
9|proxy  |   connection: 'Keep-Alive'
9|proxy  | }

Your Environment

• Version used: Version: 1.15.1.post20220707
• Environment name and version: Python 3.8.10
• Operating System and version: Ubuntu 20.04.4 LTS

[jgrocha]

If 'X-Forwarded-Proto': '' the URL generated is <ows:Get xlink:href=", https://xxx.ambiente.azores.gov.pt/mapproxy/service?">.

The value of X-Forwarded-Proto should be tested to make sure it is httpor https only, according to the documentation.