ressol.cpp - mozsearch

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/*

* (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)

            FUZZER_WRITE_AND_CRASH("A = " << a << "\n"

                                   << "P = " << p << "\n"

                                   << "R = " << a_sqrt << "\n"

                                   << "Z = " << z << "\n");

   catch(Botan::Exception& e) {}

   return;