Updated icon fetching.

- Added image type checking, and prevent downloading non images.
  We didn't checked this before, which could in turn could allow someone
to download an arbitrary file.
- This also prevents SVG images from being used, while they work on the
  web-vault and desktop client, they didn't on the mobile versions.
- Because of this image type checking we can return a valid file type
  instead of only 'x-icon' (which is still used as a fallback).
- Prevent rel values with `icon-mask`, these are not valid favicons.

src/api/icons.rs

@@ -37,6 +37,7 @@ static CLIENT: Lazy<Client> = Lazy::new(|| {
 
 // Build Regex only once since this takes a lot of time.
 static ICON_REL_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"(?i)icon$|apple.*icon").unwrap());
+static ICON_REL_BLACKLIST: Lazy<Regex> = Lazy::new(|| Regex::new(r"(?i)mask-icon").unwrap());
 static ICON_SIZE_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"(?x)(\d+)\D*(\d+)").unwrap());
 
 // Special HashMap which holds the user defined Regex to speedup matching the regex.
@@ -52,7 +53,9 @@ fn icon(domain: String) -> Cached<Content<Vec<u8>>> {
     }
 
     match get_icon(&domain) {
-        Some(i) => Cached::ttl(Content(ContentType::new("image", "x-icon"), i), CONFIG.icon_cache_ttl()),
+        Some((icon, icon_type)) => {
+            Cached::ttl(Content(ContentType::new("image", icon_type), icon), CONFIG.icon_cache_ttl())
+        },
         _ => Cached::ttl(Content(ContentType::new("image", "png"), FALLBACK_ICON.to_vec()), CONFIG.icon_cache_negttl()),
     }
 }
@@ -243,7 +246,7 @@ fn is_domain_blacklisted(domain: &str) -> bool {
     is_blacklisted
 }
 
-fn get_icon(domain: &str) -> Option<Vec<u8>> {
+fn get_icon(domain: &str) -> Option<(Vec<u8>, String)> {
     let path = format!("{}/{}.png", CONFIG.icon_cache_folder(), domain);
 
     // Check for expiration of negatively cached copy
@@ -252,7 +255,11 @@ fn get_icon(domain: &str) -> Option<Vec<u8>> {
     }
 
     if let Some(icon) = get_cached_icon(&path) {
-        return Some(icon);
+        let icon_type =  match get_icon_type(&icon) {
+            Some(x) => x,
+            _ => "x-icon",
+        };
+        return Some((icon, icon_type.to_string()));
     }
 
     if CONFIG.disable_icon_download() {
@@ -261,9 +268,9 @@ fn get_icon(domain: &str) -> Option<Vec<u8>> {
 
     // Get the icon, or None in case of error
     match download_icon(&domain) {
-        Ok(icon) => {
+        Ok((icon, icon_type)) => {
             save_icon(&path, &icon);
-            Some(icon)
+            Some((icon, icon_type.unwrap_or("x-icon").to_string()))
         }
         Err(e) => {
             error!("Error downloading icon: {:?}", e);
@@ -324,7 +331,6 @@ fn icon_is_expired(path: &str) -> bool {
     expired.unwrap_or(true)
 }
 
-#[derive(Debug)]
 struct Icon {
     priority: u8,
     href: String,
@@ -348,7 +354,7 @@ fn get_favicons_node(node: &std::rc::Rc<markup5ever_rcdom::Node>, icons: &mut Ve
                 let attr_name = attr.name.local.as_ref();
                 let attr_value = attr.value.as_ref();
 
-                if attr_name == "rel" && ICON_REL_REGEX.is_match(attr_value) {
+                if attr_name == "rel" && ICON_REL_REGEX.is_match(attr_value) && !ICON_REL_BLACKLIST.is_match(attr_value) {
                     has_rel = true;
                 } else if attr_name == "href" {
                     href = Some(attr_value);
@@ -597,7 +603,7 @@ fn parse_sizes(sizes: Option<&str>) -> (u16, u16) {
     (width, height)
 }
 
-fn download_icon(domain: &str) -> Result<Vec<u8>, Error> {
+fn download_icon(domain: &str) -> Result<(Vec<u8>, Option<&str>), Error> {
     if is_domain_blacklisted(domain) {
         err!("Domain is blacklisted", domain)
     }
@@ -605,6 +611,7 @@ fn download_icon(domain: &str) -> Result<Vec<u8>, Error> {
     let icon_result = get_icon_url(&domain)?;
 
     let mut buffer = Vec::new();
+    let mut icon_type: Option<&str> = None;
 
     use data_url::DataUrl;
 
@@ -616,17 +623,31 @@ fn download_icon(domain: &str) -> Result<Vec<u8>, Error> {
                 Ok((body, _fragment)) => {
                     // Also check if the size is atleast 67 bytes, which seems to be the smallest png i could create
                     if body.len() >= 67 {
+                        // Check if the icon type is allowed, else try an icon from the list.
+                        icon_type = get_icon_type(&body);
+                        if icon_type.is_none() {
+                            debug!("Icon from {} data:image uri, is not a valid image type", domain);
+                            continue;
+                        }
+                        info!("Extracted icon from data:image uri for {}", domain);
                         buffer = body;
                         break;
                     }
                 }
-                _ => warn!("data uri is invalid"),
+                _ => warn!("Extracted icon from data:image uri is invalid"),
             };
         } else {
             match get_page_with_cookies(&icon.href, &icon_result.cookies, &icon_result.referer) {
                 Ok(mut res) => {
-                    info!("Downloaded icon from {}", icon.href);
                     res.copy_to(&mut buffer)?;
+                    // Check if the icon type is allowed, else try an icon from the list.
+                    icon_type = get_icon_type(&buffer);
+                    if icon_type.is_none() {
+                        buffer.clear();
+                        debug!("Icon from {}, is not a valid image type", icon.href);
+                        continue;
+                    }
+                    info!("Downloaded icon from {}", icon.href);
                     break;
                 }
                 _ => warn!("Download failed for {}", icon.href),
@@ -635,10 +656,10 @@ fn download_icon(domain: &str) -> Result<Vec<u8>, Error> {
     }
 
     if buffer.is_empty() {
-        err!("Empty response")
+        err!("Empty response downloading icon")
     }
 
-    Ok(buffer)
+    Ok((buffer, icon_type))
 }
 
 fn save_icon(path: &str, icon: &[u8]) {
@@ -650,7 +671,18 @@ fn save_icon(path: &str, icon: &[u8]) {
             create_dir_all(&CONFIG.icon_cache_folder()).expect("Error creating icon cache");
         }
         Err(e) => {
-            info!("Icon save error: {:?}", e);
+            warn!("Icon save error: {:?}", e);
+        }
     }
 }
+
+fn get_icon_type(bytes: &[u8]) -> Option<&'static str> {
+    match bytes {
+        [137, 80, 78, 71, ..] => Some("png"),
+        [0, 0, 1, 0, ..] => Some("x-icon"),
+        [82, 73, 70, 70, ..] => Some("webp"),
+        [255, 216, 255, ..] => Some("jpeg"),
+        [66, 77, ..] => Some("bmp"),
+        _ => None
+    }
 }