1 files changed, 50 insertions, 0 deletions
diff --git a/src/extra_tests/fuzzers/jigs/ressol.cpp b/src/extra_tests/fuzzers/jigs/ressol.cpp
new file mode 100644
index 000000000..011194866
--- /dev/null
+++ b/src/extra_tests/fuzzers/jigs/ressol.cpp
@@ -0,0 +1,50 @@
+/*
+* (C) 2015,2016 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include "driver.h"
+#include <botan/numthry.h>
+#include <botan/system_rng.h>
+
+void fuzz(const uint8_t in[], size_t len)
+   {
+   if(len % 2 != 0)
+      return;
+
+   const BigInt a = BigInt::decode(in, len / 2);
+   const BigInt n = BigInt::decode(in + len / 2, len / 2);
+
+   try {
+       BigInt a_sqrt = ressol(a, n);
+
+      if(a_sqrt > 0)
+         {
+         /*
+         * If n is not prime then the result of ressol will be bogus. But
+         * this function is exposed to untrusted inputs (via OS2ECP) so
+         * should not hang or crash even with composite modulus.
+         * If the result is incorrect, check if n is a prime: if it is
+         * then z != a is a bug.
+         */
+         BigInt z = (a_sqrt * a_sqrt) % n;
+         BigInt a_redc = a % n;
+         if(z != a_redc)
+            {
+            if(is_prime(n, system_rng(), 64))
+               {
+               std::cout << "A = " << a << "\n";
+               std::cout << "Ressol = " << a_sqrt << "\n";
+               std::cout << "N = " << n << "\n";
+               std::cout << "Z = " << z << "\n";
+               abort();
+               }
+            }
+         }
+      }
+   catch(Botan::Exception& e) {}
+
+   return;
+   }
+