fix: add bounds checks for proof node size and count in verify_proof

Enforce MAX_PROOF_NODE_SIZE (1024 bytes) and MAX_PROOF_NODES (65) limits
in verify_proof to prevent memory/CPU exhaustion from malicious proofs
with oversized RLP payloads or excessive node counts.

The node count is validated upfront before any decoding, and individual
node sizes are checked before RLP decoding in each iteration.

Author: drappi-ai

src/proof/verify.rs

@@ -37,6 +37,16 @@ pub fn verify_proof<'a, I>(
 where
     I: IntoIterator<Item = &'a Bytes>,
 {
+    let proof: Vec<&'a Bytes> = proof.into_iter().collect();
+
+    // Enforce maximum proof node count.
+    if proof.len() > MAX_PROOF_NODES {
+        return Err(ProofVerificationError::TooManyProofNodes {
+            got: proof.len(),
+            max: MAX_PROOF_NODES,
+        });
+    }
+
     let mut proof = proof.into_iter().peekable();
 
     // If the proof is empty or contains only an empty node, the expected value must be None.
@@ -62,6 +72,13 @@ where
     let mut last_decoded_node = Some(NodeDecodingResult::Node(RlpNode::word_rlp(&root)));
     let mut last_decoded_node_is_private = false;
     for node in proof {
+        // Enforce maximum proof node size.
+        if node.len() > MAX_PROOF_NODE_SIZE {
+            return Err(ProofVerificationError::ProofNodeTooLarge {
+                got: node.len(),
+                max: MAX_PROOF_NODE_SIZE,
+            });
+        }
         // Check if the node that we just decoded (or root node, if we just started) matches
         // the expected node from the proof.
         if Some(RlpNode::from_rlp(node).as_slice()) != last_decoded_node.as_deref() {