WEB3-88: feat: implement minimal beacon API client (#214)

A simple reimplementation using reqwest and only supporting the two
required methods. This gets rid of the `beacon-api-client` dependency.

closes WEB3-97

Cargo.toml

@@ -33,7 +33,6 @@ alloy = { version = "0.3" }
 alloy-trie = { version = "0.5" }
 
 # Beacon chain support
-beacon-api-client = { git = "https://github.com/ralexstokes/ethereum-consensus.git", rev = "cf3c404043230559660810bc0c9d6d5a8498d819" }
 ethereum-consensus = { git = "https://github.com/ralexstokes/ethereum-consensus.git", rev = "cf3c404043230559660810bc0c9d6d5a8498d819" }
 
 anyhow = { version = "1.0" }
@@ -43,10 +42,12 @@ log = "0.4"
 nybbles = { version = "0.2.1" }
 once_cell = "1.19"
 revm = { version = "14.0", default-features = false, features = ["std"] }
+reqwest = "0.12"
 serde = "1.0"
 serde_json = "1.0"
 sha2 = { version = "0.10" }
 test-log = "0.2.15"
+thiserror = "1.0"
 tokio = { version = "1.35" }
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 url = { version = "2.5" }

steel/Cargo.toml

@@ -19,14 +19,16 @@ alloy-rlp = { workspace = true }
 alloy-rlp-derive = { workspace = true }
 alloy-sol-types = { workspace = true }
 anyhow = { workspace = true }
-beacon-api-client = { workspace = true, optional = true }
 ethereum-consensus = { workspace = true, optional = true }
 log = { workspace = true, optional = true }
 nybbles = { workspace = true, features = ["serde"] }
 once_cell = { workspace = true }
+reqwest = { workspace = true, optional = true }
 revm = { workspace = true, features = ["serde"] }
 serde = { workspace = true }
+serde_json = { workspace = true, optional = true }
 sha2 = { workspace = true }
+thiserror = { workspace = true }
 tokio = { workspace = true, optional = true }
 url = { workspace = true, optional = true }
 
@@ -42,9 +44,10 @@ test-log = { workspace = true }
 default = []
 host = [
     "dep:alloy",
-    "dep:beacon-api-client",
     "dep:ethereum-consensus",
     "dep:log",
+    "dep:reqwest",
+    "dep:serde_json",
     "dep:tokio",
     "dep:url",
 ]

steel/src/beacon.rs

@@ -27,7 +27,7 @@ pub struct BeaconInput<H> {
 }
 
 impl<H: EvmBlockHeader> BeaconInput<H> {
-    /// Converts the input into a [EvmEnv] for a verifiable state access in the guest.
+    /// Converts the input into a [EvmEnv] for verifiable state access in the guest.
     ///
     /// [EvmEnv]: crate::EvmEnv
     pub fn into_env(self) -> GuestEvmEnv<H> {
@@ -89,9 +89,9 @@ mod host {
         EvmBlockHeader,
     };
     use alloy::{network::Ethereum, providers::Provider, transports::Transport};
-    use alloy_primitives::Sealable;
+    use alloy_primitives::{Sealable, B256};
     use anyhow::{bail, ensure, Context};
-    use beacon_api_client::{mainnet::Client as BeaconClient, BeaconHeaderSummary, BlockId};
+    use client::{BeaconClient, GetBlockHeaderResponse};
     use ethereum_consensus::{ssz::prelude::*, types::SignedBeaconBlock, Fork};
     use log::info;
     use proofs::{Proof, ProofAndWitness};
@@ -118,47 +118,11 @@ mod host {
             let input = BlockInput::from_env(env)
                 .await
                 .context("failed to derive block input")?;
-            let client = BeaconClient::new(url);
 
-            // first get the header of the parent and then the actual block header
-            let parent_beacon_header = client
-                .get_beacon_header(BlockId::Root(parent_beacon_block_root.0.into()))
-                .await
-                .with_context(|| {
-                    format!("failed to get block header {}", parent_beacon_block_root)
-                })?;
-            let beacon_header = get_child_beacon_header(&client, parent_beacon_header)
-                .await
-                .with_context(|| {
-                    format!("failed to get child of block {}", parent_beacon_block_root)
-                })?;
-
-            // get the entire block
-            let signed_beacon_block = client
-                .get_beacon_block(BlockId::Root(beacon_header.root))
-                .await
-                .with_context(|| format!("failed to get block {}", beacon_header.root))?;
-            // create the inclusion proof of the execution block hash depending on the fork version
-            let (proof, beacon_root) = match signed_beacon_block {
-                SignedBeaconBlock::Deneb(signed_block) => {
-                    prove_block_hash_inclusion(signed_block.message)?
-                }
-                _ => {
-                    bail!(
-                        "invalid version of block {}: expected {}; got {}",
-                        beacon_header.root,
-                        Fork::Deneb,
-                        signed_beacon_block.version()
-                    );
-                }
-            };
-
-            // convert and verify the proof
-            let proof: MerkleProof = proof
-                .try_into()
-                .context("proof derived from API is invalid")?;
+            let client = BeaconClient::new(url).context("invalid URL")?;
+            let (proof, beacon_root) = create_proof(parent_beacon_block_root, client).await?;
             ensure!(
-                proof.process(block_hash).0 == beacon_root.0,
+                proof.process(block_hash) == beacon_root,
                 "proof derived from API does not verify",
             );
 
@@ -171,30 +135,153 @@ mod host {
         }
     }
 
-    /// Returns the inclusion proof of `block_hash` in the given `BeaconBlock`.
-    fn prove_block_hash_inclusion<T: SimpleSerialize>(
-        beacon_block: T,
-    ) -> Result<ProofAndWitness, MerkleizationError> {
-        // the `block_hash` is in the ExecutionPayload in the BeaconBlockBody in the BeaconBlock
-        beacon_block.prove(&[
-            "body".into(),
-            "execution_payload".into(),
-            "block_hash".into(),
-        ])
+    mod client {
+        use ethereum_consensus::{
+            phase0::SignedBeaconBlockHeader, primitives::Root, types::mainnet::SignedBeaconBlock,
+            Fork,
+        };
+        use reqwest::IntoUrl;
+        use serde::{Deserialize, Serialize};
+        use std::{collections::HashMap, fmt::Display};
+        use url::Url;
+
+        /// Errors returned by the [BeaconClient].
+        #[derive(Debug, thiserror::Error)]
+        pub enum Error {
+            #[error("could not parse URL: {0}")]
+            Url(#[from] url::ParseError),
+            #[error("HTTP request failed: {0}")]
+            Http(#[from] reqwest::Error),
+            #[error("version field does not match data version")]
+            VersionMismatch,
+        }
+
+        /// Response returned by the `get_block_header` API.
+        #[derive(Debug, Serialize, Deserialize)]
+        pub struct GetBlockHeaderResponse {
+            pub root: Root,
+            pub canonical: bool,
+            pub header: SignedBeaconBlockHeader,
+        }
+
+        /// Wrapper returned by the API calls.
+        #[derive(Serialize, Deserialize)]
+        struct Response<T> {
+            data: T,
+            #[serde(flatten)]
+            meta: HashMap<String, serde_json::Value>,
+        }
+
+        /// Wrapper returned by the API calls that includes a version.
+        #[derive(Serialize, Deserialize)]
+        struct VersionedResponse<T> {
+            version: Fork,
+            #[serde(flatten)]
+            inner: Response<T>,
+        }
+
+        /// Simple beacon API client for the `mainnet` preset that can query headers and blocks.
+        pub struct BeaconClient {
+            http: reqwest::Client,
+            endpoint: Url,
+        }
+
+        impl BeaconClient {
+            /// Creates a new beacon endpoint API client.
+            pub fn new<U: IntoUrl>(endpoint: U) -> Result<Self, Error> {
+                let client = reqwest::Client::new();
+                Ok(Self {
+                    http: client,
+                    endpoint: endpoint.into_url()?,
+                })
+            }
+
+            async fn http_get<T: serde::de::DeserializeOwned>(
+                &self,
+                path: &str,
+            ) -> Result<T, Error> {
+                let target = self.endpoint.join(path)?;
+                let resp = self.http.get(target).send().await?;
+                let value = resp.error_for_status()?.json().await?;
+                Ok(value)
+            }
+
+            /// Retrieves block header for given block id.
+            pub async fn get_block_header(
+                &self,
+                block_id: impl Display,
+            ) -> Result<GetBlockHeaderResponse, Error> {
+                let path = format!("eth/v1/beacon/headers/{block_id}");
+                let result: Response<GetBlockHeaderResponse> = self.http_get(&path).await?;
+                Ok(result.data)
+            }
+
+            /// Retrieves block details for given block id.
+            pub async fn get_block(
+                &self,
+                block_id: impl Display,
+            ) -> Result<SignedBeaconBlock, Error> {
+                let path = format!("eth/v2/beacon/blocks/{block_id}");
+                let result: VersionedResponse<SignedBeaconBlock> = self.http_get(&path).await?;
+                if result.version.to_string() != result.inner.data.version().to_string() {
+                    return Err(Error::VersionMismatch);
+                }
+                Ok(result.inner.data)
+            }
+        }
+    }
+
+    /// Creates the [MerkleProof] of `block_hash` in the `BeaconBlock` with the given
+    /// `parent_beacon_block_root`.
+    async fn create_proof(
+        parent_root: B256,
+        client: BeaconClient,
+    ) -> anyhow::Result<(MerkleProof, B256)> {
+        // first get the header of the parent and then the actual block header
+        let parent_beacon_header = client
+            .get_block_header(parent_root)
+            .await
+            .with_context(|| format!("failed to get block header {}", parent_root))?;
+        let beacon_header = get_child_beacon_header(&client, parent_beacon_header)
+            .await
+            .with_context(|| format!("failed to get child of block {}", parent_root))?;
+
+        // get the entire block
+        let signed_beacon_block = client
+            .get_block(beacon_header.root)
+            .await
+            .with_context(|| format!("failed to get block {}", beacon_header.root))?;
+        // create the inclusion proof of the execution block hash depending on the fork version
+        let (proof, beacon_root) = match signed_beacon_block {
+            SignedBeaconBlock::Deneb(signed_block) => prove_block_hash(signed_block.message)?,
+            _ => {
+                bail!(
+                    "invalid version of block {}: expected {}; got {}",
+                    beacon_header.root,
+                    Fork::Deneb,
+                    signed_beacon_block.version()
+                );
+            }
+        };
+        let proof: MerkleProof = proof
+            .try_into()
+            .context("proof derived from API is invalid")?;
+
+        Ok((proof, beacon_root.0.into()))
     }
 
     /// Returns the header, with `parent_root` equal to `parent.root`.
     ///
     /// It iteratively tries to fetch headers of successive slots until success.
-    /// TODO: use [BeaconClient::get_beacon_header_for_parent_root], once the nodes add support.
+    /// TODO: use `eth/v1/beacon/headers?parent_root`, once all the nodes support it.
     async fn get_child_beacon_header(
         client: &BeaconClient,
-        parent: BeaconHeaderSummary,
-    ) -> anyhow::Result<BeaconHeaderSummary> {
+        parent: GetBlockHeaderResponse,
+    ) -> anyhow::Result<GetBlockHeaderResponse> {
         let parent_slot = parent.header.message.slot;
         let mut request_error = None;
         for slot in (parent_slot + 1)..=(parent_slot + 32) {
-            match client.get_beacon_header(BlockId::Slot(slot)).await {
+            match client.get_block_header(slot).await {
                 Err(err) => request_error = Some(err),
                 Ok(resp) => {
                     let header = &resp.header.message;
@@ -214,6 +301,18 @@ mod host {
         Err(err.context("no valid response received for the 32 consecutive slots"))
     }
 
+    /// Returns the inclusion proof of `block_hash` in the given `BeaconBlock`.
+    fn prove_block_hash<T: SimpleSerialize>(
+        beacon_block: T,
+    ) -> Result<ProofAndWitness, MerkleizationError> {
+        // the `block_hash` is in the ExecutionPayload in the BeaconBlockBody in the BeaconBlock
+        beacon_block.prove(&[
+            "body".into(),
+            "execution_payload".into(),
+            "block_hash".into(),
+        ])
+    }
+
     impl TryFrom<Proof> for MerkleProof {
         type Error = anyhow::Error;
 
@@ -228,10 +327,38 @@ mod host {
             })
         }
     }
+
+    #[cfg(test)]
+    mod tests {
+        use super::*;
+        use alloy::{eips::BlockNumberOrTag, network::BlockResponse, providers::ProviderBuilder};
+
+        #[tokio::test]
+        #[ignore] // This queries actual RPC nodes, running only on demand.
+        async fn eth_mainnet_proof() {
+            const EL_URL: &str = "https://ethereum-rpc.publicnode.com";
+            const CL_URL: &str = "https://ethereum-beacon-api.publicnode.com";
+
+            let el = ProviderBuilder::new().on_builtin(EL_URL).await.unwrap();
+            let cl = BeaconClient::new(CL_URL).unwrap();
+
+            let block = el
+                .get_block_by_number(BlockNumberOrTag::Finalized, false)
+                .await
+                .expect("eth_getBlockByNumber failed")
+                .unwrap();
+            let header = block.header();
+
+            let (proof, beacon_root) = create_proof(header.parent_beacon_block_root.unwrap(), cl)
+                .await
+                .expect("proving failed");
+            assert_eq!(proof.process(header.hash), beacon_root);
+        }
+    }
 }
 
 #[cfg(test)]
-pub(crate) mod tests {
+mod tests {
     use super::*;
     use alloy_primitives::b256;
 

steel/src/config.rs

@@ -55,6 +55,13 @@ pub struct ChainSpec {
 
 impl ChainSpec {
     /// Creates a new configuration consisting of only one specification ID.
+    ///
+    /// For example, this can be used to create a [ChainSpec] for an anvil instance:
+    /// ```rust
+    /// # use revm::primitives::SpecId;
+    /// # use risc0_steel::config::ChainSpec;
+    /// let spec = ChainSpec::new_single(31337, SpecId::CANCUN);
+    /// ```
     pub fn new_single(chain_id: ChainId, spec_id: SpecId) -> Self {
         ChainSpec {
             chain_id,