handle proxy redirects even if the scheme doesn't match

Normally, when receiving a Location header, nginx will rewrite it to
reference a URL if it matches the proxy_pass. This breaks when the
scheme changes, since proxy_pass can have a scheme. For instance, if you
have a proxy: "https://www.foo.com", but the Location on a redirect from
that site returns "http://www.foo.com" nginx won't rewrite the URL. This
fixes it by specifying the redirect for both http and https.

scripts/config/lib/nginx_config.rb

@@ -29,6 +29,9 @@ class NginxConfig
       json["proxies"][loc]["path"] = uri.path
       uri.path = ""
       json["proxies"][loc]["host"] = uri.to_s
+      redirect_scheme = uri.scheme == "https" ? "http" : "https"
+      json["proxies"][loc]["redirect"] = uri.dup.tap {|u| u.scheme = redirect_scheme }.to_s
+      json["proxies"][loc]["redirect"] += "/" if !uri.to_s.end_with?("/")
     end
 
     json["clean_urls"] ||= DEFAULT[:clean_urls]

scripts/config/templates/nginx.conf.erb

@@ -81,6 +81,8 @@ http {
     location <%= location %> {
       proxy_pass <%= hash['origin'] %>;
       proxy_ssl_server_name on;
+      proxy_redirect default;
+      proxy_redirect <%= hash["redirect"] %>  <%= location %>;
     }
   <% end %>
 
@@ -95,6 +97,8 @@ http {
       rewrite ^<%= location %>(.*)$ <%= hash['path'] %>/$1 break;
       proxy_pass <%= hash['host'] %>;
       proxy_ssl_server_name on;
+      proxy_redirect default;
+      proxy_redirect <%= hash["redirect"] %>  <%= location %>;
     }
   <% end %>
 

spec/simple_spec.rb

@@ -383,6 +383,7 @@ STATIC_JSON
       include PathHelper
 
       let(:name)              { "proxies" }
+      let(:proxy_scheme)      { "http" }
       let(:static_json_path)  { fixtures_path("proxies/static.json") }
       let(:proxy) do
         <<PROXY
@@ -393,6 +394,16 @@ end
 get "/foo/baz/" do
   "baz"
 end
+
+get "/foo/http_redirect/" do
+  uri = URI("http://\#{request.host}/foo/redirect")
+  redirect URI(uri), 307
+end
+
+get "/foo/https_redirect/" do
+  uri = URI("https://\#{request.host}/foo/redirect")
+  redirect URI(uri), 307
+end
 PROXY
       end
       let(:setup_static_json) do
@@ -402,7 +413,7 @@ PROXY
 {
   "proxies": {
     "/api/": {
-      "origin": "http://#{@proxy_ip_address}#{path}"
+      "origin": "#{proxy_scheme}://#{@proxy_ip_address}#{path}"
     }
   },
   "headers": {
@@ -419,7 +430,7 @@ STATIC_JSON
 
       before do
         @proxy_ip_address = app.proxy.ip_address
-        setup_static_json.call("/foo/")
+        setup_static_json.call("/foo")
       end
 
       after do
@@ -439,6 +450,18 @@ STATIC_JSON
           expect(response["X-Header"]).to be_nil
         end
       end
+
+      it "should hanadle redirects regardless of scheme" do
+        app.run do
+          response = app.get("/api/http_redirect/")
+          expect(response.code).to eq("307")
+          expect(response["Location"]).not_to include(@proxy_ip_address)
+
+          response = app.get("/api/https_redirect/")
+          expect(response.code).to eq("307")
+          expect(response["Location"]).not_to include(@proxy_ip_address)
+        end
+      end
     end
   end