[oss-fuzz] fix clang compiler error

Fix size_t compare with < 0 in CpriMisc.c

Issue reported here:
    https://github.com/google/oss-fuzz/issues/859

Change-Id: I908c674f11d16bf9a795fe0c9e5c0fd0b467b1dc
Reviewed-on: https://chromium-review.googlesource.com/739946
Commit-Ready: Nagendra Modadugu <ngm@google.com>
Tested-by: Nagendra Modadugu <ngm@google.com>
Reviewed-by: Andrey Pronin <apronin@chromium.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/CpriMisc.c b/CpriMisc.c
index e809dce..edc5c4b 100644
--- a/CpriMisc.c
+++ b/CpriMisc.c
@@ -29,10 +29,12 @@ BnTo2B(
     )
 {
     BYTE      *pb = outVal->buffer;
+    UINT16    unpaddedSize = (((UINT16) BN_num_bits(inVal) + 7) / 8);
     outVal->size = size;
-    size = size - (((UINT16) BN_num_bits(inVal) + 7) / 8);
-    if(size < 0)
+    if(size < unpaddedSize)
         return FALSE;
+
+    size -= unpaddedSize;
     for(;size > 0; size--)
         *pb++ = 0;
     BN_bn2bin(inVal, pb);