Add feature to modify URLs in ruleset

README.md

@@ -17,7 +17,7 @@ Freedom of information is an essential pillar of democracy and informed decision
 ### Features
 - [x] Bypass Paywalls
 - [x] Remove CORS headers from responses, assets, and images ...
-- [x] Apply domain based ruleset/code to modify response
+- [x] Apply domain based ruleset/code to modify response / requested URL
 - [x] Keep site browsable
 - [x] API
 - [x] Fetch RAW HTML
@@ -115,7 +115,7 @@ http://localhost:8080/ruleset
 
 ### Ruleset
 
-It is possible to apply custom rules to modify the response. This can be used to remove unwanted or modify elements from the page. The ruleset is a YAML file that contains a list of rules for each domain and is loaded on startup
+It is possible to apply custom rules to modify the response or the requested URL. This can be used to remove unwanted or modify elements from the page. The ruleset is a YAML file that contains a list of rules for each domain and is loaded on startup
 
 See in [ruleset.yaml](ruleset.yaml) for an example.
 
@@ -155,4 +155,18 @@ See in [ruleset.yaml](ruleset.yaml) for an example.
     - position: .left-content article # Position where to inject the code into DOM
       prepend: | 
         <h2>Suptitle</h2>
+- domain: tagesspiegel.de
+  headers:
+    content-security-policy: script-src 'self';
+    user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36
+  urlMods:              # Modify the URL
+    query:              
+      - key: amp        # (this will append ?amp=1 to the URL)
+        value: 1 
+    domain:             
+      - match: www      # regex to match part of domain
+        replace: amp    # (this would modify the domain from www.tagesspiegel.de to amp.tagesspielgel.de)
+    path:               
+      - match: ^        # regex to match part of path
+        replace: /amp/  # (modify the url from https://www.tagesspiegel.de/internationales/ to https://www.tagesspiegel.de/amp/internationales/)
 ```

handlers/proxy.go

@@ -40,6 +40,41 @@ func ProxySite(c *fiber.Ctx) error {
 	return c.SendString(body)
 }
 
+func modifyURL(uri string, rule Rule) (string, error) {
+	newUrl, err := url.Parse(uri)
+	if err != nil {
+		return "", err
+	}
+
+	for _, urlMod := range rule.UrlMods.Domain {
+		re := regexp.MustCompile(urlMod.Match)
+		newUrl.Host = re.ReplaceAllString(newUrl.Host, urlMod.Replace)
+	}
+
+	for _, urlMod := range rule.UrlMods.Path {
+		re := regexp.MustCompile(urlMod.Match)
+		newUrl.Path = re.ReplaceAllString(newUrl.Path, urlMod.Replace)
+	}
+
+	v := newUrl.Query()
+	for _, query := range rule.UrlMods.Query {
+		if query.Value == "" {
+			v.Del(query.Key)
+			continue
+		}
+		v.Set(query.Key, query.Value)
+	}
+	newUrl.RawQuery = v.Encode()
+
+	if rule.GoogleCache {
+		newUrl, err = url.Parse("https://webcache.googleusercontent.com/search?q=cache:" + newUrl.String())
+		if err != nil {
+			return "", err
+		}
+	}
+	return newUrl.String(), nil
+}
+
 func fetchSite(urlpath string, queries map[string]string) (string, *http.Request, *http.Response, error) {
 	urlQuery := "?"
 	if len(queries) > 0 {
@@ -63,18 +98,17 @@ func fetchSite(urlpath string, queries map[string]string) (string, *http.Request
 		log.Println(u.String() + urlQuery)
 	}
 
+	// Modify the URI according to ruleset
 	rule := fetchRule(u.Host, u.Path)
-
-	if rule.GoogleCache {
-		u, err = url.Parse("https://webcache.googleusercontent.com/search?q=cache:" + u.String())
-		if err != nil {
-			return "", nil, nil, err
-		}
+	url, err := modifyURL(u.String()+urlQuery, rule)
+	if err != nil {
+		return "", nil, nil, err
 	}
+	log.Println("fetch URI: %", url)
 
 	// Fetch the site
 	client := &http.Client{}
-	req, _ := http.NewRequest("GET", u.String()+urlQuery, nil)
+	req, _ := http.NewRequest("GET", url, nil)
 
 	if rule.Headers.UserAgent != "" {
 		req.Header.Set("User-Agent", rule.Headers.UserAgent)

handlers/types.go

@@ -4,6 +4,10 @@ type Regex struct {
 	Match   string `yaml:"match"`
 	Replace string `yaml:"replace"`
 }
+type KV struct {
+	Key   string `yaml:"key"`
+	Value string `yaml:"value"`
+}
 
 type RuleSet []Rule
 
@@ -20,7 +24,14 @@ type Rule struct {
 	} `yaml:"headers,omitempty"`
 	GoogleCache bool    `yaml:"googleCache,omitempty"`
 	RegexRules  []Regex `yaml:"regexRules"`
-	Injections  []struct {
+
+	UrlMods struct {
+		Domain []Regex `yaml:"domain"`
+		Path   []Regex `yaml:"path"`
+		Query  []KV    `yaml:"query"`
+	} `yaml:"urlMods"`
+
+	Injections []struct {
 		Position string `yaml:"position"`
 		Append   string `yaml:"append"`
 		Prepend  string `yaml:"prepend"`

ruleset.yaml

@@ -163,3 +163,11 @@
     user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36
     content-security-policy: script-src 'self';
     cookie: 
+- domain: tagesspiegel.de
+  headers:
+    content-security-policy: script-src 'self';
+    user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36
+  urlMods:
+    query:
+      - key: amp
+        value: 1