From d22ab5de0ad47e6840b46c5a8e00876e631aac18 Mon Sep 17 00:00:00 2001
From: joshieDo <93316087+joshieDo@users.noreply.github.com>
Date: Wed, 17 Aug 2022 22:13:51 +0100
Subject: [PATCH] fix(providers): validate address resolver (#1605)

* validate address resolver

* use Selector type instead

* specify which ens_name on resolver error

* pad supportsInterface argument
---
 ethers-providers/src/ens.rs      | 16 ++++++++++
 ethers-providers/src/provider.rs | 53 ++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/ethers-providers/src/ens.rs b/ethers-providers/src/ens.rs
index 8e349ba1..74ad728d 100644
--- a/ethers-providers/src/ens.rs
+++ b/ethers-providers/src/ens.rs
@@ -28,6 +28,9 @@ pub const NAME_SELECTOR: Selector = [105, 31, 52, 49];
 /// text(bytes32, string)
 pub const FIELD_SELECTOR: Selector = [89, 209, 212, 60];
 
+/// supportsInterface(bytes4 interfaceID)
+pub const INTERFACE_SELECTOR: Selector = [1, 255, 201, 167];
+
 /// Returns a transaction request for calling the `resolver` method on the ENS server
 pub fn get_resolver<T: Into<Address>>(ens_address: T, name: &str) -> TransactionRequest {
     // keccak256('resolver(bytes32)')
@@ -39,6 +42,19 @@ pub fn get_resolver<T: Into<Address>>(ens_address: T, name: &str) -> Transaction
     }
 }
 
+/// Returns a transaction request for checking interface support
+pub fn supports_interface<T: Into<Address>>(
+    resolver_address: T,
+    selector: Selector,
+) -> TransactionRequest {
+    let data = [&INTERFACE_SELECTOR[..], &selector[..], &[0; 28]].concat();
+    TransactionRequest {
+        data: Some(data.into()),
+        to: Some(NameOrAddress::Address(resolver_address.into())),
+        ..Default::default()
+    }
+}
+
 /// Returns a transaction request for calling
 pub fn resolve<T: Into<Address>>(
     resolver_address: T,
diff --git a/ethers-providers/src/provider.rs b/ethers-providers/src/provider.rs
index dc07c8fe..d4d0a0eb 100644
--- a/ethers-providers/src/provider.rs
+++ b/ethers-providers/src/provider.rs
@@ -1263,6 +1263,11 @@ impl<P: JsonRpcClient> Provider<P> {
             return Err(ProviderError::EnsError(ens_name.to_string()))
         }
 
+        if let ParamType::Address = param {
+            // Reverse resolver reverts when calling `supportsInterface(bytes4)`
+            self.validate_resolver(resolver_address, selector, ens_name).await?;
+        }
+
         // resolve
         let data = self
             .call(&ens::resolve(resolver_address, selector, ens_name, parameters).into(), None)
@@ -1271,6 +1276,39 @@ impl<P: JsonRpcClient> Provider<P> {
         Ok(decode_bytes(param, data))
     }
 
+    /// Validates that the resolver supports `selector`.
+    async fn validate_resolver(
+        &self,
+        resolver_address: Address,
+        selector: Selector,
+        ens_name: &str,
+    ) -> Result<(), ProviderError> {
+        let data =
+            self.call(&ens::supports_interface(resolver_address, selector).into(), None).await?;
+
+        if data.is_empty() {
+            return Err(ProviderError::EnsError(format!(
+                "`{}` resolver ({:?}) is invalid.",
+                ens_name, resolver_address
+            )))
+        }
+
+        let supports_selector = abi::decode(&[ParamType::Bool], data.as_ref())
+            .map(|token| token[0].clone().into_bool().unwrap_or_default())
+            .unwrap_or_default();
+
+        if !supports_selector {
+            return Err(ProviderError::EnsError(format!(
+                "`{}` resolver ({:?}) does not support selector {}.",
+                ens_name,
+                resolver_address,
+                hex::encode(&selector)
+            )))
+        }
+
+        Ok(())
+    }
+
     #[cfg(test)]
     /// Anvil and Ganache-only function for mining empty blocks
     pub async fn mine(&self, num_blocks: usize) -> Result<(), ProviderError> {
@@ -2133,4 +2171,19 @@ mod tests {
         assert_eq!(tx.gas_price(), Some(gas_price));
         assert!(tx.access_list().is_none());
     }
+
+    #[tokio::test]
+    async fn mainnet_lookup_address_invalid_resolver() {
+        let provider = crate::MAINNET.provider();
+
+        let err = provider
+            .lookup_address("0x30c9223d9e3d23e0af1073a38e0834b055bf68ed".parse().unwrap())
+            .await
+            .unwrap_err();
+
+        assert_eq!(
+            &err.to_string(),
+            "ens name not found: `ox63616e.eth` resolver (0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2) is invalid."
+        );
+    }
 }