/*

* (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(std::span<const uint8_t> in) {

   // 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(in.size() > p_bits / 8) {

      return;

   }

   try {

      const Botan::BigInt a = Botan::BigInt::from_bytes(in);

      Botan::BigInt a_sqrt = Botan::sqrt_modulo_prime(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) {

            FUZZER_WRITE_AND_CRASH("A = " << a.to_hex_string() << "\n"

                                          << "P = " << p.to_hex_string() << "\n"

                                          << "R = " << a_sqrt.to_hex_string() << "\n"

                                          << "Z = " << z.to_hex_string() << "\n");

         }

      }

   } catch(Botan::Exception& e) {}

}