From 902055f29565234cd5f799af75eba3b91e8690ed Mon Sep 17 00:00:00 2001
From: Pawan Dhananjay <pawandhananjay@gmail.com>
Date: Tue, 22 Nov 2022 01:58:21 +0530
Subject: [PATCH] ugly utils

---
 beacon_node/beacon_chain/Cargo.toml       |  1 +
 beacon_node/beacon_chain/src/kzg_utils.rs | 65 +++++++++++++++++------
 beacon_node/beacon_chain/src/lib.rs       |  1 +
 consensus/types/src/eth_spec.rs           |  5 ++
 crypto/kzg/src/lib.rs                     |  1 +
 5 files changed, 57 insertions(+), 16 deletions(-)

diff --git a/beacon_node/beacon_chain/Cargo.toml b/beacon_node/beacon_chain/Cargo.toml
index 39ff16c6b..51c1fbb57 100644
--- a/beacon_node/beacon_chain/Cargo.toml
+++ b/beacon_node/beacon_chain/Cargo.toml
@@ -50,6 +50,7 @@ lru = "0.7.1"
 tempfile = "3.1.0"
 bitvec = "0.20.4"
 bls = { path = "../../crypto/bls" }
+kzg = { path = "../../crypto/kzg" }
 safe_arith = { path = "../../consensus/safe_arith" }
 fork_choice = { path = "../../consensus/fork_choice" }
 task_executor = { path = "../../common/task_executor" }
diff --git a/beacon_node/beacon_chain/src/kzg_utils.rs b/beacon_node/beacon_chain/src/kzg_utils.rs
index 11060a131..ef6045043 100644
--- a/beacon_node/beacon_chain/src/kzg_utils.rs
+++ b/beacon_node/beacon_chain/src/kzg_utils.rs
@@ -1,27 +1,60 @@
-use types::{Blob, BlobsSidecar, EthSpec, KzgCommitment, KzgProof};
+use kzg::Kzg;
+use types::{Blob, BlobsSidecar, EthSpec, Hash256, KzgCommitment, KzgProof, Slot};
 
-pub fn validate_blobs_sidecar(
+// TODO(pawan): make this generic over blob size
+fn ssz_blob_to_crypto_blob<T: EthSpec>(blob: Blob<T>) -> Option<[u8; 131072]> {
+    if blob.len() != 131072 {
+        return None;
+    }
+    let blob_vec: Vec<u8> = blob.into();
+    let mut arr = [0; 131072];
+    arr.copy_from_slice(&blob_vec);
+    Some(arr)
+}
+
+pub fn validate_blobs_sidecar<T: EthSpec>(
+    kzg: &Kzg,
     slot: Slot,
     beacon_block_root: Hash256,
     expected_kzg_commitments: &[KzgCommitment],
-    blobs_sidecar: BlobsSidecar<T: EthSpec>,
-) -> bool {
-    //TODO(pawan): change to a Result later
-    if slot != blobs_sidecar.blobs
+    blobs_sidecar: BlobsSidecar<T>,
+) -> Result<bool, String> {
+    if slot != blobs_sidecar.beacon_block_slot
         || beacon_block_root != blobs_sidecar.beacon_block_root
         || blobs_sidecar.blobs.len() != expected_kzg_commitments.len()
-        || !verify_aggregate_kzg_proof(
-            blobs_sidecar.blobs,
-            expected_kzg_commitments,
-            blobs_sidecar.kzg_aggregate_proof,
-        )
     {
-        return false;
-    } else {
-        return true;
+        return Ok(false);
     }
+
+    let blobs = blobs_sidecar
+        .blobs
+        .into_iter()
+        .map(|blob| ssz_blob_to_crypto_blob::<T>(blob.clone())) // TODO(pawan): avoid this clone
+        .collect::<Option<Vec<_>>>()
+        .ok_or_else(|| "Invalid blobs in sidecar".to_string())?;
+
+    kzg.verify_aggregate_kzg_proof(
+        &blobs,
+        expected_kzg_commitments,
+        blobs_sidecar.kzg_aggregate_proof,
+    )
+    .map_err(|e| format!("Failed to verify kzg proof: {:?}", e))
 }
 
-pub fn compute_aggregate_kzg_proof(blobs: &[Blob<T: EthSpec>]) -> KzgProof {
-    unimplemented!()
+pub fn compute_aggregate_kzg_proof<T: EthSpec>(
+    kzg: &Kzg,
+    blobs: &[Blob<T>],
+) -> Result<KzgProof, String> {
+    let blobs = blobs
+        .into_iter()
+        .map(|blob| ssz_blob_to_crypto_blob::<T>(blob.clone())) // TODO(pawan): avoid this clone
+        .collect::<Option<Vec<_>>>()
+        .ok_or_else(|| "Invalid blobs in sidecar".to_string())?;
+    kzg.compute_aggregate_kzg_proof(&blobs)
+        .map_err(|e| format!("Failed to compute kzg proof: {:?}", e))
+}
+
+pub fn blob_to_kzg_commitment<T: EthSpec>(kzg: &Kzg, blob: Blob<T>) -> Option<KzgCommitment> {
+    let blob = ssz_blob_to_crypto_blob::<T>(blob)?;
+    Some(kzg.blob_to_kzg_commitment(blob))
 }
diff --git a/beacon_node/beacon_chain/src/lib.rs b/beacon_node/beacon_chain/src/lib.rs
index 19b90de1a..e1831078d 100644
--- a/beacon_node/beacon_chain/src/lib.rs
+++ b/beacon_node/beacon_chain/src/lib.rs
@@ -23,6 +23,7 @@ pub mod fork_choice_signal;
 pub mod fork_revert;
 mod head_tracker;
 pub mod historical_blocks;
+pub mod kzg_utils;
 pub mod merge_readiness;
 mod metrics;
 pub mod migrate;
diff --git a/consensus/types/src/eth_spec.rs b/consensus/types/src/eth_spec.rs
index 745aa304d..fd1064a34 100644
--- a/consensus/types/src/eth_spec.rs
+++ b/consensus/types/src/eth_spec.rs
@@ -258,6 +258,11 @@ pub trait EthSpec: 'static + Default + Sync + Send + Clone + Debug + PartialEq +
     fn chunks_per_blob() -> usize {
         Self::FieldElementsPerBlob::to_usize()
     }
+
+    /// Returns the `BYTES_PER_BLOB` constant for the specification.
+    fn bytes_per_blob() -> usize {
+        Self::BytesPerBlob::to_usize()
+    }
 }
 
 /// Macro to inherit some type values from another EthSpec.
diff --git a/crypto/kzg/src/lib.rs b/crypto/kzg/src/lib.rs
index 0f9638546..8f068848c 100644
--- a/crypto/kzg/src/lib.rs
+++ b/crypto/kzg/src/lib.rs
@@ -24,6 +24,7 @@ pub enum Error {
     KzgProofComputationFailed(CKzgError),
 }
 
+/// A wrapper over a kzg library that holds the trusted setup parameters.
 pub struct Kzg {
     trusted_setup: KZGSettings,
 }