1 files changed, 36 insertions, 0 deletions
diff --git a/security/nss/fuzz/mpi_mod_target.cc b/security/nss/fuzz/mpi_mod_target.cc
new file mode 100644
index 000000000..85c883faf
--- /dev/null
+++ b/security/nss/fuzz/mpi_mod_target.cc
@@ -0,0 +1,36 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * This target fuzzes NSS mpi against openssl bignum.
+ * It therefore requires openssl to be installed.
+ */
+
+#include "mpi_helper.h"
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  // We require at least size 3 to get two integers from Data.
+  if (size < 3) {
+    return 0;
+  }
+  INIT_FOUR_NUMBERS
+
+  // We can't divide by 0.
+  if (mp_cmp_z(&b) == 0) {
+    CLEANUP_AND_RETURN
+  }
+
+  // Compare with OpenSSL mod
+  assert(mp_mod(&a, &b, &c) == MP_OKAY);
+  (void)BN_mod(C, A, B, ctx);
+  check_equal(C, &c, max_size);
+
+  // Check a mod b = a - floor(a / b) * b
+  assert(mp_div(&a, &b, &r, nullptr) == MP_OKAY);
+  assert(mp_mul(&r, &b, &r) == MP_OKAY);
+  assert(mp_sub(&a, &r, &r) == MP_OKAY);
+  assert(mp_cmp(&c, &r) == 0);
+
+  CLEANUP_AND_RETURN
+}