1 files changed, 49 insertions, 0 deletions
diff --git a/comm/third_party/botan/src/fuzzer/barrett.cpp b/comm/third_party/botan/src/fuzzer/barrett.cpp
new file mode 100644
index 0000000000..ebc6001971
--- /dev/null
+++ b/comm/third_party/botan/src/fuzzer/barrett.cpp
@@ -0,0 +1,49 @@
+/*
+* (C) 2018,2020 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include "fuzzers.h"
+#include <botan/numthry.h>
+#include <botan/reducer.h>
+#include <botan/divide.h>
+
+void fuzz(const uint8_t in[], size_t len)
+   {
+   static const size_t max_bits = 4096;
+
+   if(len <= 4)
+      return;
+
+   if(len > 2*(max_bits/8))
+      return;
+
+   const size_t x_len = 2 * ((len + 2) / 3);
+
+   Botan::BigInt x = Botan::BigInt::decode(in, x_len);
+   const Botan::BigInt p = Botan::BigInt::decode(in + x_len, len - x_len);
+
+   if(p.is_zero())
+      return;
+
+   const size_t x_bits = x.bits();
+   if(x_bits % 8 == 0 && x_bits / 8 == x_len)
+      x.flip_sign();
+
+   const Botan::BigInt ref = x % p;
+
+   const Botan::Modular_Reducer mod_p(p);
+   const Botan::BigInt z = mod_p.reduce(x);
+
+   const Botan::BigInt ct = ct_modulo(x, p);
+
+   if(ref != z || ref != ct)
+      {
+      FUZZER_WRITE_AND_CRASH("X = " << x << "\n"
+                             << "P = " << p << "\n"
+                             << "Barrett = " << z << "\n"
+                             << "Ct = " << ct << "\n"
+                             << "Ref = " << ref << "\n");
+      }
+   }