fix "modifer" -> "modifier" typo everywhere

proxychain/responsemodifiers/patch_dynamic_resource_urls.go

@@ -0,0 +1,56 @@
+package responsemodifiers
+
+import (
+	_ "embed"
+	"fmt"
+	"strings"
+
+	"ladder/proxychain"
+	"ladder/proxychain/responsemodifiers/rewriters"
+)
+
+//go:embed patch_dynamic_resource_urls.js
+var patchDynamicResourceURLsScript string
+
+// PatchDynamicResourceURLs patches the javascript runtime to rewrite URLs client-side.
+//   - This function is designed to allow the proxified page
+//     to still be browsible by routing all resource URLs through the proxy.
+//   - Native APIs capable of network requests will be hooked
+//     and the URLs arguments modified to point to the proxy instead.
+//   - fetch('/relative_path') -> fetch('/https://proxiedsite.com/relative_path')
+//   - Element.setAttribute('src', "/assets/img.jpg") -> Element.setAttribute('src', "/https://proxiedsite.com/assets/img.jpg") -> fetch('/https://proxiedsite.com/relative_path')
+func PatchDynamicResourceURLs() proxychain.ResponseModification {
+	return func(chain *proxychain.ProxyChain) error {
+		// don't add rewriter if it's not even html
+		ct := chain.Response.Header.Get("content-type")
+		if !strings.HasPrefix(ct, "text/html") {
+			return nil
+		}
+
+		// this is the original URL sent by client:
+		// http://localhost:8080/http://proxiedsite.com/foo/bar
+		originalURI := chain.Context.Request().URI()
+
+		// this is the extracted URL that the client requests to proxy
+		// http://proxiedsite.com/foo/bar
+		reqURL := chain.Request.URL
+
+		params := map[string]string{
+			// ie: http://localhost:8080
+			"{{PROXY_ORIGIN}}": fmt.Sprintf("%s://%s", originalURI.Scheme(), originalURI.Host()),
+			// ie: http://proxiedsite.com
+			"{{ORIGIN}}": fmt.Sprintf("%s://%s", reqURL.Scheme, reqURL.Host),
+		}
+
+		rr := rewriters.NewScriptInjectorRewriterWithParams(
+			patchDynamicResourceURLsScript,
+			rewriters.BeforeDOMContentLoaded,
+			params,
+		)
+
+		htmlRewriter := rewriters.NewHTMLRewriter(chain.Response.Body, rr)
+		chain.Response.Body = htmlRewriter
+
+		return nil
+	}
+}