fix: make sure to match servers even if they contain “regexp” chars (#9)

This is a fix in the JWT token verification in both:

- the server verification which was using an uneeded regex in the
  `start_with?` parameter
- the path verification which was using the matching_server data
  inside a regexp without escaping the input data

I added a test case showcasing the issue.

proxy_server.rb

@@ -70,7 +70,7 @@ class ProxyServer < Sinatra::Base
         target_url = request.fullpath[1..].gsub(":/", "://")
 
         # Verify server is allowed
-        matching_server = @payload["servers"].find { |server| target_url.to_s.start_with?(/^#{server}/) }&.chomp("/")
+        matching_server = @payload["servers"].find { |server| target_url.to_s.start_with?(server) }&.chomp("/")
 
         unless matching_server
           halt 403, {error: "Server not allowed"}.to_json
@@ -91,7 +91,7 @@ class ProxyServer < Sinatra::Base
 
   helpers do
     def path_from_target_url(target_url, matching_server)
-      target_url.gsub(/^#{matching_server}/, "")
+      target_url.gsub(/^#{Regexp.escape(matching_server)}/, "")
     end
 
     def path_matches_pattern?(actual_path, pattern_path)

spec/proxy_server_spec.rb

@@ -62,17 +62,18 @@ def expect_json_body(k, v)
       .to_return(status: 200, body: {title: "updated title"}.to_json, headers: {})
     stub_request(:post, "https://jsonplaceholder.typicode.com/posts")
       .to_return(status: 201, body: {title: "foo", body: "bar", userId: 1}.to_json, headers: {})
-    stub_request(:get, "https://staging.bump.sh/api/v1/ping")
-      .with(
-        headers: {
-        'Accept'=>'*/*',
-        'Accept-Encoding'=>'gzip;q=1.0,deflate;q=0.6,identity;q=0.3',
-        'Cookie'=>'',
-        'Host'=>'staging.bump.sh',
-        'User-Agent'=>'Ruby',
-        'X-Foo'=>'bar'
-        })
-      .to_return(status: 200, body: "", headers: {})
+    ["https://staging.bump.sh/api/v1/ping", "https://bump.sh/api/Custom+Api/v1/ping"].each do |server|
+      stub_request(:get, server)
+        .with(headers: {
+            'Accept' => '*/*',
+            'Accept-Encoding' => 'gzip;q=1.0,deflate;q=0.6,identity;q=0.3',
+            'Cookie'=>'',
+            'Host'=> URI.parse(server).host,
+            'User-Agent'=>'Ruby',
+            'X-Foo'=>'bar'
+          })
+        .to_return(status: 200, body: "", headers: {})
+    end
   end
 
   context "preflight request" do
@@ -99,7 +100,6 @@ def expect_json_body(k, v)
         end
 
         context "when server contains some path like /api/v1" do
-
           let(:payload) do
             {
               "servers": [
@@ -118,6 +118,25 @@ def expect_json_body(k, v)
           it "returns 200" do
             expect(last_response.status).to eq(200)
           end
+
+          context "when server contains path with regexp character" do
+            let(:payload) do
+              {
+                "servers": [
+                  "https://bump.sh/api/Custom+Api/v1"
+                ],
+                "verb": "GET",
+                "path": "/ping",
+                "exp": Time.now.to_i + 500
+              }
+            end
+
+            let(:target_url) { "https://bump.sh/api/Custom+Api/v1/ping"}
+
+            it "returns 200" do
+              expect(last_response.status).to eq(200)
+            end
+          end
         end
 
         it "returns cors headers" do