From f289374e70ca6cbd67c226292cd2f2521d04a182 Mon Sep 17 00:00:00 2001
From: Felix Ableitner <me@nutomic.com>
Date: Fri, 18 Jun 2021 20:38:34 +0200
Subject: [PATCH] Remove tracking params from post url (fixes #768)

---
 crates/api_crud/src/post/create.rs |  4 ++--
 crates/api_crud/src/post/update.rs |  4 ++--
 crates/utils/src/utils.rs          | 27 +++++++++++++++++++++++++++
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/crates/api_crud/src/post/create.rs b/crates/api_crud/src/post/create.rs
index 835518a14..4ce7c0644 100644
--- a/crates/api_crud/src/post/create.rs
+++ b/crates/api_crud/src/post/create.rs
@@ -13,7 +13,7 @@ use lemmy_db_schema::source::post::*;
 use lemmy_db_views::post_view::PostView;
 use lemmy_utils::{
   request::fetch_iframely_and_pictrs_data,
-  utils::{check_slurs, check_slurs_opt, is_valid_post_title},
+  utils::{check_slurs, check_slurs_opt, clean_url_params, is_valid_post_title},
   ApiError,
   ConnectionId,
   LemmyError,
@@ -48,7 +48,7 @@ impl PerformCrud for CreatePost {
 
     let post_form = PostForm {
       name: data.name.trim().to_owned(),
-      url: data_url.map(|u| u.to_owned().into()),
+      url: data_url.map(|u| clean_url_params(u.to_owned()).into()),
       body: data.body.to_owned(),
       community_id: data.community_id,
       creator_id: local_user_view.person.id,
diff --git a/crates/api_crud/src/post/update.rs b/crates/api_crud/src/post/update.rs
index ca7634d5a..59f8e446a 100644
--- a/crates/api_crud/src/post/update.rs
+++ b/crates/api_crud/src/post/update.rs
@@ -7,7 +7,7 @@ use lemmy_db_schema::{naive_now, source::post::*};
 use lemmy_db_views::post_view::PostView;
 use lemmy_utils::{
   request::fetch_iframely_and_pictrs_data,
-  utils::{check_slurs_opt, is_valid_post_title},
+  utils::{check_slurs_opt, clean_url_params, is_valid_post_title},
   ApiError,
   ConnectionId,
   LemmyError,
@@ -59,7 +59,7 @@ impl PerformCrud for EditPost {
       creator_id: orig_post.creator_id.to_owned(),
       community_id: orig_post.community_id,
       name: data.name.to_owned().unwrap_or(orig_post.name),
-      url: data_url.map(|u| u.to_owned().into()),
+      url: data_url.map(|u| clean_url_params(u.to_owned()).into()),
       body: data.body.to_owned(),
       nsfw: data.nsfw,
       updated: Some(naive_now()),
diff --git a/crates/utils/src/utils.rs b/crates/utils/src/utils.rs
index 31936788a..c6f1aaaf0 100644
--- a/crates/utils/src/utils.rs
+++ b/crates/utils/src/utils.rs
@@ -4,6 +4,7 @@ use chrono::{DateTime, FixedOffset, NaiveDateTime};
 use itertools::Itertools;
 use rand::{distributions::Alphanumeric, thread_rng, Rng};
 use regex::{Regex, RegexBuilder};
+use url::Url;
 
 lazy_static! {
   static ref EMAIL_REGEX: Regex = Regex::new(r"^[a-zA-Z0-9.!#$%&’*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$").expect("compile regex");
@@ -25,6 +26,8 @@ lazy_static! {
   static ref VALID_COMMUNITY_NAME_REGEX: Regex = Regex::new(r"^[a-z0-9_]{3,20}$").expect("compile regex");
   static ref VALID_POST_TITLE_REGEX: Regex = Regex::new(r".*\S.*").expect("compile regex");
   static ref VALID_MATRIX_ID_REGEX: Regex = Regex::new(r"^@[A-Za-z0-9._=-]+:[A-Za-z0-9.-]+\.[A-Za-z]{2,}$").expect("compile regex");
+  // taken from https://en.wikipedia.org/wiki/UTM_parameters
+  static ref CLEAN_URL_PARAMS_REGEX: Regex = Regex::new(r"^utm_source|utm_medium|utm_campaign|utm_term|utm_content|gclid|gclsrc|dclid|fbclid$").expect("compile regex");
 }
 
 pub fn naive_from_unix(time: i64) -> NaiveDateTime {
@@ -148,3 +151,27 @@ pub fn get_ip(conn_info: &ConnectionInfo) -> IpAddr {
       .to_string(),
   )
 }
+
+pub fn clean_url_params(mut url: Url) -> Url {
+  let new_query = url
+    .query_pairs()
+    .filter(|q| !CLEAN_URL_PARAMS_REGEX.is_match(&q.0))
+    .map(|q| format!("{}={}", q.0, q.1))
+    .join("&");
+  url.set_query(Some(&new_query));
+  url
+}
+
+#[cfg(test)]
+mod tests {
+  use crate::utils::clean_url_params;
+  use url::Url;
+
+  #[test]
+  fn test_clean_url_params() {
+    let url = Url::parse("https://example.com/path/123?utm_content=buffercf3b2&utm_medium=social&username=randomuser&id=123").unwrap();
+    let cleaned = clean_url_params(url);
+    let expected = Url::parse("https://example.com/path/123?username=randomuser&id=123").unwrap();
+    assert_eq!(expected.to_string(), cleaned.to_string());
+  }
+}