Add dynamic CSS support (#4940)

* Add dynamic CSS support

Together with https://github.com/dani-garcia/bw_web_builds/pull/180 this PR will add support for dynamic CSS changes.

For example, we could hide the register link if signups are not allowed.
In the future show or hide the SSO button depending on if it is enabled or not.

There also is a special `user.vaultwarden.scss` file so that users can add custom CSS without the need to modify the default (static) changes.
This will prevent future changes from not being applied and still have the custom user changes to be added.

Also added a special redirect when someone goes directly to `/index.html` as that might cause issues with loading other scripts and files.

Signed-off-by: BlackDex <black.dex@gmail.com>

* Add versions and fallback to built-in

- Add both Vaultwarden and web-vault versions to the css_options.
- Fallback to the inner templates if rendering or compiling the scss fails.
  This ensures the basics are always working even if someone breaks the templates.

Signed-off-by: BlackDex <black.dex@gmail.com>

* Fix fallback code to actually work

The fallback now works by using an alternative `reg!` macro.
This adds an extra template register which prefixes the template with `fallback_`.

Signed-off-by: BlackDex <black.dex@gmail.com>

* Updated the wiki link in the user template

---------

Signed-off-by: BlackDex <black.dex@gmail.com>

src/api/web.rs

@@ -1,13 +1,20 @@
+use once_cell::sync::Lazy;
 use std::path::{Path, PathBuf};
 
-use rocket::{fs::NamedFile, http::ContentType, response::content::RawHtml as Html, serde::json::Json, Catcher, Route};
+use rocket::{
+    fs::NamedFile,
+    http::ContentType,
+    response::{content::RawCss as Css, content::RawHtml as Html, Redirect},
+    serde::json::Json,
+    Catcher, Route,
+};
 use serde_json::Value;
 
 use crate::{
     api::{core::now, ApiResult, EmptyResult},
     auth::decode_file_download,
     error::Error,
-    util::{Cached, SafeString},
+    util::{get_web_vault_version, Cached, SafeString},
     CONFIG,
 };
 
@@ -16,7 +23,7 @@ pub fn routes() -> Vec<Route> {
     // crate::utils::LOGGED_ROUTES to make sure they appear in the log
     let mut routes = routes![attachments, alive, alive_head, static_files];
     if CONFIG.web_vault_enabled() {
-        routes.append(&mut routes![web_index, web_index_head, app_id, web_files]);
+        routes.append(&mut routes![web_index, web_index_direct, web_index_head, app_id, web_files, vaultwarden_css]);
     }
 
     #[cfg(debug_assertions)]
@@ -45,11 +52,101 @@ fn not_found() -> ApiResult<Html<String>> {
     Ok(Html(text))
 }
 
+#[get("/css/vaultwarden.css")]
+fn vaultwarden_css() -> Cached<Css<String>> {
+    // Configure the web-vault version as an integer so it can be used as a comparison smaller or greater then.
+    // The default is based upon the version since this feature is added.
+    static WEB_VAULT_VERSION: Lazy<u32> = Lazy::new(|| {
+        let re = regex::Regex::new(r"(\d{4})\.(\d{1,2})\.(\d{1,2})").unwrap();
+        let vault_version = get_web_vault_version();
+
+        let (major, minor, patch) = match re.captures(&vault_version) {
+            Some(c) if c.len() == 4 => (
+                c.get(1).unwrap().as_str().parse().unwrap(),
+                c.get(2).unwrap().as_str().parse().unwrap(),
+                c.get(3).unwrap().as_str().parse().unwrap(),
+            ),
+            _ => (2024, 6, 2),
+        };
+        format!("{major}{minor:02}{patch:02}").parse::<u32>().unwrap()
+    });
+
+    // Configure the Vaultwarden version as an integer so it can be used as a comparison smaller or greater then.
+    // The default is based upon the version since this feature is added.
+    static VW_VERSION: Lazy<u32> = Lazy::new(|| {
+        let re = regex::Regex::new(r"(\d{1})\.(\d{1,2})\.(\d{1,2})").unwrap();
+        let vw_version = crate::VERSION.unwrap_or("1.32.1");
+
+        let (major, minor, patch) = match re.captures(vw_version) {
+            Some(c) if c.len() == 4 => (
+                c.get(1).unwrap().as_str().parse().unwrap(),
+                c.get(2).unwrap().as_str().parse().unwrap(),
+                c.get(3).unwrap().as_str().parse().unwrap(),
+            ),
+            _ => (1, 32, 1),
+        };
+        format!("{major}{minor:02}{patch:02}").parse::<u32>().unwrap()
+    });
+
+    let css_options = json!({
+        "web_vault_version": *WEB_VAULT_VERSION,
+        "vw_version": *VW_VERSION,
+        "signup_disabled": !CONFIG.signups_allowed() && CONFIG.signups_domains_whitelist().is_empty(),
+        "mail_enabled": CONFIG.mail_enabled(),
+        "yubico_enabled": CONFIG._enable_yubico() && (CONFIG.yubico_client_id().is_some() == CONFIG.yubico_secret_key().is_some()),
+        "emergency_access_allowed": CONFIG.emergency_access_allowed(),
+        "sends_allowed": CONFIG.sends_allowed(),
+        "load_user_scss": true,
+    });
+
+    let scss = match CONFIG.render_template("scss/vaultwarden.scss", &css_options) {
+        Ok(t) => t,
+        Err(e) => {
+            // Something went wrong loading the template. Use the fallback
+            warn!("Loading scss/vaultwarden.scss.hbs or scss/user.vaultwarden.scss.hbs failed. {e}");
+            CONFIG
+                .render_fallback_template("scss/vaultwarden.scss", &css_options)
+                .expect("Fallback scss/vaultwarden.scss.hbs to render")
+        }
+    };
+
+    let css = match grass_compiler::from_string(
+        scss,
+        &grass_compiler::Options::default().style(grass_compiler::OutputStyle::Compressed),
+    ) {
+        Ok(css) => css,
+        Err(e) => {
+            // Something went wrong compiling the scss. Use the fallback
+            warn!("Compiling the Vaultwarden SCSS styles failed. {e}");
+            let mut css_options = css_options;
+            css_options["load_user_scss"] = json!(false);
+            let scss = CONFIG
+                .render_fallback_template("scss/vaultwarden.scss", &css_options)
+                .expect("Fallback scss/vaultwarden.scss.hbs to render");
+            grass_compiler::from_string(
+                scss,
+                &grass_compiler::Options::default().style(grass_compiler::OutputStyle::Compressed),
+            )
+            .expect("SCSS to compile")
+        }
+    };
+
+    // Cache for one day should be enough and not too much
+    Cached::ttl(Css(css), 86_400, false)
+}
+
 #[get("/")]
 async fn web_index() -> Cached<Option<NamedFile>> {
     Cached::short(NamedFile::open(Path::new(&CONFIG.web_vault_folder()).join("index.html")).await.ok(), false)
 }
 
+// Make sure that `/index.html` redirect to actual domain path.
+// If not, this might cause issues with the web-vault
+#[get("/index.html")]
+fn web_index_direct() -> Redirect {
+    Redirect::to(format!("{}/", CONFIG.domain_path()))
+}
+
 #[head("/")]
 fn web_index_head() -> EmptyResult {
     // Add an explicit HEAD route to prevent uptime monitoring services from