Add offset checks for sigverify (#6452)

* Add offset checks for sigverify

* decode_len returning error instead of unwrap

core/benches/sigverify.rs

@@ -22,3 +22,23 @@ fn bench_sigverify(bencher: &mut Bencher) {
         let _ans = sigverify::ed25519_verify(&batches, &recycler, &recycler_out);
     })
 }
+
+#[bench]
+fn bench_get_offsets(bencher: &mut Bencher) {
+    let tx = test_tx();
+
+    // generate packet vector
+    let batches = to_packets(&vec![tx; 1024]);
+
+    let recycler = Recycler::default();
+    // verify packets
+    bencher.iter(|| {
+        let ans = sigverify::generate_offsets(&batches, &recycler);
+        assert!(ans.is_ok());
+        let ans = ans.unwrap();
+        recycler.recycle(ans.0);
+        recycler.recycle(ans.1);
+        recycler.recycle(ans.2);
+        recycler.recycle(ans.3);
+    })
+}