From d1245462199d24bd680d78f2dbf1baca0d4e2270 Mon Sep 17 00:00:00 2001
From: Chris Czub <chris.czub@gmail.com>
Date: Wed, 17 Jul 2024 10:11:45 -0400
Subject: [PATCH] fix(rust): Enforce that `spec.InnerSpec.ChildSize` is >= 1
 (#339)

* Enforce that the spec.InnerSpec.ChildSize is >= 1

* Add changelog entry

---------

Co-authored-by: Romain Ruetschi <romain@informal.systems>
---
 CHANGELOG.md       | 7 +++++++
 rust/src/verify.rs | 4 ++++
 2 files changed, 11 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cbfe0b75..023a0497 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,11 @@
 # Changelog
+
+# Unreleased
+
+## Rust
+
+- fix(rust): Enforce that `spec.InnerSpec.ChildSize` is >= 1  ([#339](https://github.com/cosmos/ics23/pull/339))
+
 # 0.11.1
 
 ## Rust
diff --git a/rust/src/verify.rs b/rust/src/verify.rs
index babe99ae..ade0b93a 100644
--- a/rust/src/verify.rs
+++ b/rust/src/verify.rs
@@ -201,6 +201,10 @@ fn ensure_inner(inner: &ics23::InnerOp, spec: &ics23::ProofSpec) -> Result<()> {
                 "Inner prefix too long: {}",
                 inner.prefix.len(),
             );
+            ensure!(
+                inner_spec.child_size > 0,
+                "spec.InnerSpec.ChildSize must be >= 1"
+            );
             ensure!(
                 inner.suffix.len() % (inner_spec.child_size as usize) == 0,
                 "InnerOp suffix malformed"