Install custom RAND_METHOD for fuzzing

Instead of setting a "magic" global variable to force RAND to keep
consistent state and always generate the same bytestream, have
the fuzzing code install its own RAND_METHOD that does this.  For
BN_RAND_DEBUG, we just don't do it; that debugging was about mucking
with BN's internal representation, not requiring predictable rand
bytes.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/4025)

1 files changed, 31 insertions, 0 deletions

diff --git a/fuzz/test-corpus.c b/fuzz/test-corpus.c
index 9cef01f86d..a876f209c9 100644
--- a/fuzz/test-corpus.c
+++ b/fuzz/test-corpus.c
@@ -18,8 +18,39 @@
 #include <stdlib.h>
 #include <sys/stat.h>
 #include <openssl/crypto.h>
+#include <openssl/rand.h>
 #include "fuzzer.h"
 
+static int fuzz_bytes(unsigned char *buf, int num)
+{
+    unsigned char val = 1;
+
+    while (--num >= 0)
+        *buf++ = val++;
+    return 1;
+}
+
+static int fuzz_status(void)
+{
+    return 1;
+}
+
+static RAND_METHOD fuzz_rand_method = {
+    NULL,
+    fuzz_bytes,
+    NULL,
+    NULL,
+    fuzz_bytes,
+    fuzz_status
+};
+
+void FuzzerSetRand(void)
+{
+    RAND_set_rand_method(&fuzz_rand_method);
+}
+
+
+
 int main(int argc, char **argv) {
     int n;