Make using insecure connections opt-in (#1309)

* add insecure url checks

* rename variables

* add feature flags to expose Url properly

* fix test compile error

* fix feature errors

* remove comment

* add url crate and use it for url parsing

* fix compile errors

* satisfy the holy clippy

* fix typos and host loopback

* macro attribute, provide validation function in utils

* fix expected output of ui tests

* remove the success case for --allow-insecure because we cannot establish ws:// connection at the moment.

subxt/src/utils/mod.rs

@@ -13,8 +13,11 @@ mod static_type;
 mod unchecked_extrinsic;
 mod wrapper_opaque;
 
+use crate::error::RpcError;
+use crate::Error;
 use codec::{Compact, Decode, Encode};
 use derivative::Derivative;
+use url::Url;
 
 pub use account_id::AccountId32;
 pub use era::Era;
@@ -47,6 +50,31 @@ pub(crate) fn strip_compact_prefix(bytes: &[u8]) -> Result<(u64, &[u8]), codec::
     Ok((val.0, *cursor))
 }
 
+/// A URL is considered secure if it uses a secure scheme ("https" or "wss") or is referring to localhost.
+///
+/// Returns an error if the the string could not be parsed into a URL.
+pub fn url_is_secure(url: &str) -> Result<bool, Error> {
+    let url = Url::parse(url).map_err(|e| Error::Rpc(RpcError::ClientError(Box::new(e))))?;
+
+    let secure_scheme = url.scheme() == "https" || url.scheme() == "wss";
+    let is_localhost = url.host().is_some_and(|e| match e {
+        url::Host::Domain(e) => e == "localhost",
+        url::Host::Ipv4(e) => e.is_loopback(),
+        url::Host::Ipv6(e) => e.is_loopback(),
+    });
+
+    Ok(secure_scheme || is_localhost)
+}
+
+/// Validates, that the given Url is secure ("https" or "wss" scheme) or is referring to localhost.
+pub fn validate_url_is_secure(url: &str) -> Result<(), Error> {
+    if !url_is_secure(url)? {
+        Err(Error::Rpc(crate::error::RpcError::InsecureUrl(url.into())))
+    } else {
+        Ok(())
+    }
+}
+
 /// A version of [`std::marker::PhantomData`] that is also Send and Sync (which is fine
 /// because regardless of the generic param, it is always possible to Send + Sync this
 /// 0 size type).