handle srcset resource URL rewrites; monkey patch JS for URL rewrites
This commit is contained in:
Kevin Pham
62
proxychain/responsemodifers/monkey_patch_resource_urls.js
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62
proxychain/responsemodifers/monkey_patch_resource_urls.js
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@@ -0,0 +1,62 @@
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// Overrides the global fetch and XMLHttpRequest open methods to modify the request URLs.
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// Also overrides the attribute setter prototype to modify the request URLs
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// fetch("/relative_script.js") -> fetch("http://localhost:8080/relative_script.js")
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(() => {
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function rewriteURL(url) {
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if (!url) return url
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if (url.startsWith(window.location.origin)) return url
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if (url.startsWith("//")) {
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url = `${window.location.origin}/${encodeURIComponent(url.substring(2))}`;
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} else if (url.startsWith("/")) {
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url = `${window.location.origin}/${encodeURIComponent(url.substring(1))}`;
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} else if (url.startsWith("http://") || url.startsWith("https://")) {
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url = `${window.location.origin}/${encodeURIComponent(url)}`;
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}
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return url;
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};
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// monkey patch fetch
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const oldFetch = globalThis.fetch ;
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globalThis.fetch = async (url, init) => {
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return oldFetch(rewriteURL(url), init)
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}
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// monkey patch xmlhttprequest
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const oldOpen = XMLHttpRequest.prototype.open;
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XMLHttpRequest.prototype.open = function(method, url, async = true, user = null, password = null) {
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return oldOpen.call(this, method, rewriteURL(url), async, user, password);
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};
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// Monkey patch setter methods
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const elements = [
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{ tag: 'a', attribute: 'href' },
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{ tag: 'img', attribute: 'src' },
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{ tag: 'script', attribute: 'src' },
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{ tag: 'link', attribute: 'href' },
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{ tag: 'iframe', attribute: 'src' },
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{ tag: 'audio', attribute: 'src' },
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{ tag: 'video', attribute: 'src' },
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{ tag: 'source', attribute: 'src' },
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{ tag: 'embed', attribute: 'src' },
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{ tag: 'object', attribute: 'src' },
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{ tag: 'input', attribute: 'src' },
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{ tag: 'track', attribute: 'src' },
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{ tag: 'form', attribute: 'action' },
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];
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elements.forEach(({ tag, attribute }) => {
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const proto = document.createElement(tag).constructor.prototype;
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const descriptor = Object.getOwnPropertyDescriptor(proto, attribute);
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if (descriptor && descriptor.set) {
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Object.defineProperty(proto, attribute, {
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...descriptor,
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set(value) {
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return descriptor.set.call(this, rewriteURL(value));
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}
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});
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}
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});
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})();
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@@ -5,7 +5,6 @@ import (
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"fmt"
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"io"
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"ladder/proxychain"
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"log"
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"net/url"
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"strings"
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@@ -17,24 +16,22 @@ var AttributesToRewrite map[string]bool
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func init() {
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AttributesToRewrite = map[string]bool{
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"src": true,
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"href": true,
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/*
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"action": true,
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"srcset": true,
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"poster": true,
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"data": true,
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"cite": true,
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"formaction": true,
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"background": true,
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"usemap": true,
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"longdesc": true,
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"manifest": true,
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"archive": true,
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"codebase": true,
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"icon": true,
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"pluginspage": true,
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*/
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"src": true,
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"href": true,
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"action": true,
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"srcset": true, // TODO: fix
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"poster": true,
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"data": true,
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"cite": true,
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"formaction": true,
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"background": true,
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"usemap": true,
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"longdesc": true,
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"manifest": true,
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"archive": true,
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"codebase": true,
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"icon": true,
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"pluginspage": true,
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}
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}
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@@ -42,7 +39,7 @@ func init() {
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// It uses an HTML tokenizer to process HTML content and rewrites URLs in src/href attributes.
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// <img src='/relative_path'> -> <img src='/https://proxiedsite.com/relative_path'>
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type HTMLResourceURLRewriter struct {
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baseURL string // eg: https://proxiedsite.com (note, no trailing '/')
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baseURL *url.URL
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tokenizer *html.Tokenizer
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currentToken html.Token
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tokenBuffer *bytes.Buffer
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@@ -52,7 +49,7 @@ type HTMLResourceURLRewriter struct {
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// NewHTMLResourceURLRewriter creates a new instance of HTMLResourceURLRewriter.
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// It initializes the tokenizer with the provided source and sets the proxy URL.
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func NewHTMLResourceURLRewriter(src io.ReadCloser, baseURL string) *HTMLResourceURLRewriter {
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func NewHTMLResourceURLRewriter(src io.ReadCloser, baseURL *url.URL) *HTMLResourceURLRewriter {
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return &HTMLResourceURLRewriter{
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tokenizer: html.NewTokenizer(src),
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currentToken: html.Token{},
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@@ -110,64 +107,124 @@ func (r *HTMLResourceURLRewriter) Read(p []byte) (int, error) {
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return n, err
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}
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func patchResourceURL(token *html.Token, baseURL string) {
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// Root-relative URLs: These are relative to the root path and start with a "/".
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func handleRootRelativePath(attr *html.Attribute, baseURL *url.URL) {
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// doublecheck this is a valid relative URL
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_, err := url.Parse(fmt.Sprintf("http://localhost.com%s", attr.Val))
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if err != nil {
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return
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}
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//log.Printf("BASEURL patch: %s\n", baseURL)
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attr.Val = fmt.Sprintf(
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"/%s://%s/%s",
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baseURL.Scheme,
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baseURL.Host,
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strings.TrimPrefix(attr.Val, "/"),
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)
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attr.Val = url.QueryEscape(attr.Val)
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attr.Val = fmt.Sprintf("/%s", attr.Val)
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//log.Printf("root rel url rewritten-> '%s'='%s'", attr.Key, attr.Val)
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}
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// Document-relative URLs: These are relative to the current document's path and don't start with a "/".
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func handleDocumentRelativePath(attr *html.Attribute, baseURL *url.URL) {
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attr.Val = fmt.Sprintf(
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"%s://%s/%s%s",
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baseURL.Scheme,
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strings.Trim(baseURL.Host, "/"),
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strings.Trim(baseURL.RawPath, "/"),
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strings.Trim(attr.Val, "/"),
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)
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attr.Val = url.QueryEscape(attr.Val)
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attr.Val = fmt.Sprintf("/%s", attr.Val)
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//log.Printf("doc rel url rewritten-> '%s'='%s'", attr.Key, attr.Val)
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}
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// Protocol-relative URLs: These start with "//" and will use the same protocol (http or https) as the current page.
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func handleProtocolRelativePath(attr *html.Attribute, baseURL *url.URL) {
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attr.Val = strings.TrimPrefix(attr.Val, "/")
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handleRootRelativePath(attr, baseURL)
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//log.Printf("proto rel url rewritten-> '%s'='%s'", attr.Key, attr.Val)
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}
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func handleAbsolutePath(attr *html.Attribute, baseURL *url.URL) {
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// check if valid URL
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u, err := url.Parse(attr.Val)
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if err != nil {
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return
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}
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if !(u.Scheme == "http" || u.Scheme == "https") {
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return
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}
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attr.Val = fmt.Sprintf(
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"/%s",
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url.QueryEscape(
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strings.TrimPrefix(attr.Val, "/"),
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),
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)
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//log.Printf("abs url rewritten-> '%s'='%s'", attr.Key, attr.Val)
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}
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func handleSrcSet(attr *html.Attribute, baseURL *url.URL) {
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for i, src := range strings.Split(attr.Val, ",") {
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src = strings.Trim(src, " ")
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for j, s := range strings.Split(src, " ") {
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s = strings.Trim(s, " ")
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if j == 0 {
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f := &html.Attribute{Val: s, Key: attr.Key}
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switch {
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case strings.HasPrefix(s, "//"):
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handleProtocolRelativePath(f, baseURL)
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case strings.HasPrefix(s, "/"):
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handleRootRelativePath(f, baseURL)
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case strings.HasPrefix(s, "https://") || strings.HasPrefix(s, "http://"):
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handleAbsolutePath(f, baseURL)
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default:
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handleDocumentRelativePath(f, baseURL)
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}
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s = f.Val
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}
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if i == 0 && j == 0 {
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attr.Val = s
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continue
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}
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attr.Val = fmt.Sprintf("%s %s", attr.Val, s)
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}
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attr.Val = fmt.Sprintf("%s,", attr.Val)
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}
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attr.Val = strings.TrimSuffix(attr.Val, ",")
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}
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// TODO: figure out how to handle these
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// srcset
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func patchResourceURL(token *html.Token, baseURL *url.URL) {
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for i := range token.Attr {
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attr := &token.Attr[i]
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switch {
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// dont touch attributes except for the ones we defined
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_, exists := AttributesToRewrite[attr.Key]
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if !exists {
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case !AttributesToRewrite[attr.Key]:
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continue
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case attr.Key == "srcset":
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handleSrcSet(attr, baseURL)
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continue
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case strings.HasPrefix(attr.Val, "//"):
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handleProtocolRelativePath(attr, baseURL)
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continue
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case strings.HasPrefix(attr.Val, "/"):
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handleRootRelativePath(attr, baseURL)
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continue
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case strings.HasPrefix(attr.Val, "https://") || strings.HasPrefix(attr.Val, "http://"):
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handleAbsolutePath(attr, baseURL)
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continue
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default:
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handleDocumentRelativePath(attr, baseURL)
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continue
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}
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isRelativePath := strings.HasPrefix(attr.Val, "/")
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//log.Printf("PRE '%s'='%s'", attr.Key, attr.Val)
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// double check if attribute is valid http URL before modifying
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if isRelativePath {
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_, err := url.Parse(fmt.Sprintf("http://localhost%s", attr.Val))
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if err != nil {
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return
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}
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} else {
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u, err := url.Parse(attr.Val)
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if err != nil {
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return
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}
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if !(u.Scheme == "http" || u.Scheme == "https") {
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return
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}
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}
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// patch relative paths
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// <img src="/favicon.png"> -> <img src="/http://images.cdn.proxiedsite.com/favicon.png">
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if isRelativePath {
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log.Printf("BASEURL patch: %s\n", baseURL)
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attr.Val = fmt.Sprintf(
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"/%s/%s",
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baseURL,
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//url.QueryEscape(
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strings.TrimPrefix(attr.Val, "/"),
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//),
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)
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log.Printf("url rewritten-> '%s'='%s'", attr.Key, attr.Val)
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continue
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}
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// patch absolute paths to relative path pointing to ladder proxy
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// <img src="http://images.cdn.proxiedsite.com/favicon.png"> -> <img src="/http://images.cdn.proxiedsite.com/favicon.png">
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//log.Printf("abolute patch: %s\n", attr.Val)
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attr.Val = fmt.Sprintf(
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"/%s",
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//url.QueryEscape(attr.Val),
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//url.QueryEscape(
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strings.TrimPrefix(attr.Val, "/"),
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//),
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//attr.Val,
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)
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log.Printf("url rewritten-> '%s'='%s'", attr.Key, attr.Val)
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}
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}
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@@ -199,15 +256,7 @@ func RewriteHTMLResourceURLs() proxychain.ResponseModification {
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return nil
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}
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// should be site being requested to proxy
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baseUrl := fmt.Sprintf("%s://%s", chain.Request.URL.Scheme, chain.Request.URL.Host)
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/*
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log.Println("--------------------")
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log.Println(baseUrl)
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log.Println("--------------------")
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*/
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chain.Response.Body = NewHTMLResourceURLRewriter(chain.Response.Body, baseUrl)
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chain.Response.Body = NewHTMLResourceURLRewriter(chain.Response.Body, chain.Request.URL)
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return nil
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}
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}
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