From 90231619888635e13eca0ba6d8b8f378ccc23dc3 Mon Sep 17 00:00:00 2001
From: Sean Bowe <ewillbefull@gmail.com>
Date: Sat, 10 Jul 2021 08:25:00 -0600
Subject: [PATCH] Add bounds check to Assignment::query_instance impls.

---
 src/dev.rs              | 4 ++++
 src/dev/graph/layout.rs | 2 --
 src/plonk/keygen.rs     | 6 +++++-
 src/plonk/prover.rs     | 4 ++++
 4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/dev.rs b/src/dev.rs
index 7bfa869d..ed93f450 100644
--- a/src/dev.rs
+++ b/src/dev.rs
@@ -297,6 +297,10 @@ impl<F: Field + Group> Assignment<F> for MockProver<F> {
     }
 
     fn query_instance(&self, column: Column<Instance>, row: usize) -> Result<Option<F>, Error> {
+        if !self.usable_rows.contains(&row) {
+            return Err(Error::BoundsFailure);
+        }
+
         self.instance
             .get(column.index())
             .and_then(|column| column.get(row))
diff --git a/src/dev/graph/layout.rs b/src/dev/graph/layout.rs
index 389e721b..bb8cdf7f 100644
--- a/src/dev/graph/layout.rs
+++ b/src/dev/graph/layout.rs
@@ -308,8 +308,6 @@ impl<F: Field> Assignment<F> for Layout {
         self.assign_fixed(annotation, selector.0, row, || Ok(F::one()))
     }
 
-    /// Query the value of the cell of an instance column at a particular
-    /// absolute row, if known.
     fn query_instance(&self, _: Column<Instance>, _: usize) -> Result<Option<F>, Error> {
         Ok(None)
     }
diff --git a/src/plonk/keygen.rs b/src/plonk/keygen.rs
index 4be0af08..ae2d1488 100644
--- a/src/plonk/keygen.rs
+++ b/src/plonk/keygen.rs
@@ -83,7 +83,11 @@ impl<F: Field> Assignment<F> for Assembly<F> {
         self.assign_fixed(annotation, selector.0, row, || Ok(F::one()))
     }
 
-    fn query_instance(&self, _: Column<Instance>, _: usize) -> Result<Option<F>, Error> {
+    fn query_instance(&self, _: Column<Instance>, row: usize) -> Result<Option<F>, Error> {
+        if !self.usable_rows.contains(&row) {
+            return Err(Error::BoundsFailure);
+        }
+
         // There is no instance in this context.
         Ok(None)
     }
diff --git a/src/plonk/prover.rs b/src/plonk/prover.rs
index 82d54750..d3e0ae3a 100644
--- a/src/plonk/prover.rs
+++ b/src/plonk/prover.rs
@@ -166,6 +166,10 @@ pub fn create_proof<
                     column: Column<Instance>,
                     row: usize,
                 ) -> Result<Option<F>, Error> {
+                    if !self.usable_rows.contains(&row) {
+                        return Err(Error::BoundsFailure);
+                    }
+
                     self.instances
                         .get(column.index())
                         .and_then(|column| column.get(row))