Make the bignum fuzzer reproducible

Reviewed-by: NRich Salz <rsalz@openssl.org>
GH: #2182

fuzz/bignum.c

@@ -15,23 +15,14 @@
 
 #include <stdio.h>
 #include <openssl/bn.h>
+#include <openssl/err.h>
 #include "fuzzer.h"
 
-static BN_CTX *ctx;
-static BIGNUM *b1;
-static BIGNUM *b2;
-static BIGNUM *b3;
-static BIGNUM *b4;
-static BIGNUM *b5;
 
 int FuzzerInitialize(int *argc, char ***argv)
 {
-    b1 = BN_new();
-    b2 = BN_new();
-    b3 = BN_new();
-    b4 = BN_new();
-    b5 = BN_new();
-    ctx = BN_CTX_new();
+    OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CRYPTO_STRINGS, NULL);
+    ERR_get_state();
 
     return 1;
 }
@@ -41,6 +32,19 @@ int FuzzerTestOneInput(const uint8_t *buf, size_t len)
     int success = 0;
     size_t l1 = 0, l2 = 0, l3 = 0;
     int s1 = 0, s2 = 0, s3 = 0;
+    BN_CTX *ctx;
+    BIGNUM *b1;
+    BIGNUM *b2;
+    BIGNUM *b3;
+    BIGNUM *b4;
+    BIGNUM *b5;
+
+    b1 = BN_new();
+    b2 = BN_new();
+    b3 = BN_new();
+    b4 = BN_new();
+    b5 = BN_new();
+    ctx = BN_CTX_new();
 
     /* Divide the input into three parts, using the values of the first two
      * bytes to choose lengths, which generate b1, b2 and b3. Use three bits
@@ -91,16 +95,17 @@ int FuzzerTestOneInput(const uint8_t *buf, size_t len)
 
  done:
     OPENSSL_assert(success);
-
-    return 0;
-}
-
-void FuzzerCleanup(void)
-{
     BN_free(b1);
     BN_free(b2);
     BN_free(b3);
     BN_free(b4);
     BN_free(b5);
     BN_CTX_free(ctx);
+    ERR_clear_error();
+
+    return 0;
+}
+
+void FuzzerCleanup(void)
+{
 }