1 files changed, 45 insertions, 0 deletions
diff --git a/src/fuzzer/ressol.cpp b/src/fuzzer/ressol.cpp
new file mode 100644
index 000000000..17ba88b8b
--- /dev/null
+++ b/src/fuzzer/ressol.cpp
@@ -0,0 +1,45 @@
+/*
+* (C) 2015,2016 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include "fuzzers.h"
+#include <botan/numthry.h>
+#include <botan/reducer.h>
+
+void fuzz(const uint8_t in[], size_t len)
+   {
+   // Ressol is mostly used for ECC point decompression so best to test smaller sizes
+   static const size_t p_bits = 256;
+   static const Botan::BigInt p = random_prime(fuzzer_rng(), p_bits);
+   static const Botan::Modular_Reducer mod_p(p);
+
+   if(len > p_bits / 8)
+      return;
+
+   try
+      {
+      const Botan::BigInt a = Botan::BigInt::decode(in, len);
+      Botan::BigInt a_sqrt = Botan::ressol(a, p);
+
+      if(a_sqrt > 0)
+         {
+         const Botan::BigInt a_redc = mod_p.reduce(a);
+         const Botan::BigInt z = mod_p.square(a_sqrt);
+
+         if(z != a_redc)
+            {
+            std::cout << "A = " << a << "\n";
+            std::cout << "P = " << p << "\n";
+            std::cout << "R = " << a_sqrt << "\n";
+            std::cout << "Z = " << z << "\n";
+            abort();
+            }
+         }
+      }
+   catch(Botan::Exception& e) {}
+
+   return;
+   }
+